Preparation method of anti-aging and anti-deformation plastic storage box

Abstract

The invention discloses a preparation method of an anti-aging and anti-deformation plastic storage box, and relates to the technical field of plastic products. The modified polypropylene product is obtained by preparing polypropylene resin, an antioxidant, an ultraviolet light absorber, a beta nucleating agent, an elastomer, reinforcing filler and other components in parts by mass and adopting melt blending granulation and injection molding processes. The defects that a common polypropylene material is prone to aging and creep deformation in long-term use are effectively overcome, the weather resistance and dimensional stability of the storage box are improved, and the storage box is suitable for household and industrial storage application. The abstract is defined within the core technical features and application range of the content of the specification.

Description

Technical Field

[0001] This invention relates to the field of plastic products technology, and in particular to a method for preparing an aging-resistant and deformation-resistant plastic storage box. Background Technology

[0002] Polypropylene is a thermoplastic polyhydrocarbon polymer material with propylene as its monomer. It has advantages such as low density, good mechanical properties, strong chemical resistance, easy processing and molding, and low cost, and is widely used in packaging, daily plastics, automotive parts, household goods and other fields. Its molecular structure exhibits high crystallinity, thus possessing good rigidity and mechanical strength.

[0003] However, the insufficient anti-aging properties of polypropylene have always been a technical challenge in the field of materials science. The PP molecular chain contains a large number of tertiary carbon structures. These structures have low C–H bond energies and are sensitive to external factors such as heat, oxygen, and long-wave ultraviolet light, readily generating free radicals that trigger oxidative degradation reactions. During thermo-oxidative aging, the PP molecular chain gradually breaks and oxidizes, causing the material surface to lose toughness, crack, darken in color, or yellow, severely affecting the material's performance and lifespan.

[0004] Existing research indicates that unmodified PP typically has a service life of only a few years under normal outdoor conditions, with a significant decline in mechanical properties after aging, and even powdering and cracking. To improve its aging resistance, various modification strategies have been proposed both domestically and internationally. Common methods include adding antioxidants, light stabilizers, and UV absorbers to the resin to block or delay free radical oxidation chain reactions and slow down the material's aging rate. A modified formulation conforming to this approach has been proposed in patent CN112662064A, which includes the combined use of antioxidants, light stabilizers, nano-oxides, and other additives to achieve excellent anti-aging performance.

[0005] Furthermore, aging not only affects mechanical properties but also the dimensional stability and service deformation (such as creep) properties of materials. PP is prone to deformation and even permanent deformation under long-term loads or high temperatures, partly due to its internal crystal structure and chain segment movement. To improve these properties, the addition of nucleating agents has been extensively studied. For example, patents WO2011130928A1 and US9085683B2 disclose nucleating agent compositions for PP, including carboxylates and phosphates, which can effectively improve the material's rigidity and heat distortion temperature, and enhance overall properties such as impact strength, thus helping to solve deformation problems.

[0006] On the other hand, in actual industrial applications, various formulations and manufacturing methods have been proposed for different application scenarios. For example, patent CN102690466A discloses an anti-aging PP material comprising copolymer PP, ethylene propylene diene monomer (EPDM) toughening agent, talc filler, and anti-aging agent, indicating that by combining multiple components, both anti-aging properties and comprehensive mechanical properties can be improved simultaneously.

[0007] In summary, although polypropylene has good overall performance, it has shortcomings such as poor aging resistance and limited deformation resistance. Therefore, how to rationally design polypropylene modification systems and combine them with process flow to prepare high-performance plastic products that are resistant to aging and deformation is a key technical problem that needs to be solved. Summary of the Invention

[0008] Based on the problems raised in the background art mentioned above, the present invention proposes a method for preparing an aging-resistant and deformation-resistant plastic storage box.

[0009] The technical solution is as follows: A method for preparing an aging-resistant and deformation-resistant plastic storage box includes the following steps: (1) Prepare a polypropylene-based modified composite material, which, by mass parts, includes: Polypropylene resin: 100 parts; Antioxidant: 0.5–2.0 parts; Ultraviolet absorber: 0.5–2.5 parts; β-nucleating agent: 0.05–0.5 parts; Elastomer toughening agent: 3-12 parts; Reinforcing filler: 0.5–5 parts; (2) Mix the above components according to the proportion range specified in step (1), preheat and dry them, and then melt-blend and granulate them in a twin-screw granulator at a temperature of 190-240℃ and a speed of 200-500rpm to obtain modified polypropylene granules. (3) The obtained modified polypropylene granules are dried and then injection molded in an injection molding machine under the conditions of melt temperature 200-230℃, mold temperature 40-80℃ and injection pressure 60-120MPa to obtain an aging-resistant and deformation-resistant plastic storage box.

[0010] Furthermore, the antioxidant is selected from 1010 or 168 or a combination thereof.

[0011] Furthermore, the ultraviolet absorber is selected from UV-327 or UV-328.

[0012] Furthermore, the β-nucleating agent is selected from TMB-5β or NJSTARNU-100 / NJS.

[0013] Furthermore, the elastomer toughening agent is selected from ethylene propylene rubber (EPR) or ASA copolymer. Furthermore, the reinforcing filler is modified nano-TiO2, and its preparation method is as follows: According to the mass fractions, 100 parts of nano-TiO2, 1.5-3.0 parts of γ-glycidyl etheroxypropyltrimethoxysilane, and 1000-1200 parts of ethanol were added to a reaction vessel. Nitrogen gas was introduced to remove oxygen and water for 10-30 minutes, and the mixture was stirred at room temperature for 20-60 minutes until it was evenly dispersed. 5-15 parts of deionized water were added dropwise, and the temperature was raised to 60-70℃ and reacted for 2-3.5 hours. 1.2-3.2 parts of 1-aminobenzotriazole were added, followed by 0.6-2.7 parts of triethylamine. The temperature was raised to 70-80℃ and the reaction was continued for 3-4 hours. After the reaction was completed, toluene was removed by vacuum distillation, and the mixture was dried under vacuum at 90-100℃ for 3-7 hours and then ground through an 80-mesh sieve to obtain modified nano-TiO2.

[0014] Furthermore, the preheating and drying temperature is 80–110°C, and the time is 2–6 hours.

[0015] Furthermore, during the injection molding process, the pressure is held for 5 to 15 seconds and the cooling time is 30 to 120 seconds.

[0016] Reaction mechanism of modified nano-TiO2: In an ethanol system, γ-glycidoxypropyltrimethoxysilane undergoes hydrolysis of the siloxane group in deionized water to generate silanol groups. These silanol groups then undergo dehydration condensation with the titanium hydroxyl groups on the surface of nano-TiO2 to form stable covalent bonds, thus achieving chemical grafting of the silane coupling agent onto the surface of nano-TiO2. During this process, the epoxy groups of the silane remain active throughout. Subsequently, 1-aminobenzotriazole is added, and its amino group undergoes a nucleophilic ring-opening addition reaction with the active epoxy groups on the silane grafted onto the surface of nano-TiO2 under the catalysis of triethylamine, forming stable CN covalent bonds. This successfully grafts the benzotriazole functional group with UV absorption properties onto the surface of nano-TiO2, completing the functionalization modification of nano-TiO2.

[0017] Effects of modified nano-TiO2 technology: 1) The interfacial compatibility between the modified nano-TiO2 and the polypropylene matrix is ​​greatly improved, which effectively solves the problem of easy agglomeration of inorganic fillers, enabling the filler to be uniformly dispersed in the polypropylene matrix and strengthening the structural density of the matrix.

[0018] 2) The benzotriazole functional groups grafted onto the surface of modified nano-TiO2 can exert a highly efficient ultraviolet absorption effect, forming a synergistic protective effect with the ultraviolet absorbers in the system, significantly improving the light aging resistance of the material and delaying the photo-oxidative degradation of polypropylene molecular chains.

[0019] 3) The modified nano-TiO2 forms a bifunctional modified layer through chemical grafting, which enhances the bonding force between the filler and the polypropylene matrix, effectively improves the material's creep resistance, and improves the material's dimensional stability and resistance to permanent deformation.

[0020] Compared with the prior art, the present invention has the following advantages: 1. Significantly improves resistance to light aging: The addition of ultraviolet absorbers and antioxidants can effectively delay the damage of ultraviolet rays and heat-oxidation environment to polypropylene chains, and improve the long-term outdoor and indoor service life. 2. Improved resistance to deformation: By adding elastomers and reinforcing fillers, the creep resistance and permanent deformation resistance of the material can be improved, making the product less prone to deformation under load. 3. Simple process and controllable cost: The preparation method is based on conventional melt blending and injection molding processes, which is easy to apply in industrial applications. Detailed Implementation

[0021] The features of the present invention are further illustrated below through embodiments, but the scope of protection of this patent is not limited to the embodiments. Example 1

[0022] A method for preparing an aging-resistant and deformation-resistant plastic storage box includes the following steps: (1) Preparation of polypropylene-based modified composite material: Weigh each component accurately by mass, and the specific amounts are as follows: 100 kg of polypropylene resin (homopolymer polypropylene, melting point 167℃, melt flow rate 2.5 g / 10 min, 230℃ / 2.16 kg); 0.5 kg of antioxidant (antioxidant 1010, purity ≥99.0%, white powder); 0.5 kg of ultraviolet absorber (UV-327, purity ≥98.5%, pale yellow powder); 0.05 kg of β nucleating agent (TMB-5β, purity ≥99.0%); 3 kg of elastomer toughening agent (ethylene propylene rubber EPR, ethylene content 40 wt%, Mooney viscosity ML1+4 (100℃) = 25); 0.5 kg of reinforcing filler (modified nano TiO2).

[0023] The modified nano-TiO2 is prepared as follows: Weigh 100 kg of nano-TiO2 (anatase type, particle size 30 nm, specific surface area 80 m² / g), 1.5 kg of γ-glycidyl etheroxypropyltrimethoxysilane (purity ≥98.5%), and 1000 kg of ethanol (purity ≥99.7%), and add them all to a 5000 L three-necked reactor; introduce nitrogen gas (flow rate 0.3 m³ / h) into the reactor to remove oxygen and water for 10 minutes; close the nitrogen valve, turn on the stirrer (speed 120 r / min), and stir at room temperature for 20 minutes until the material is evenly dispersed; slowly add 5 kg of deionized water dropwise using a constant pressure dropping funnel. After the addition was complete, the temperature was raised to 60℃ and the reaction was maintained at this temperature for 2 hours. Then, 1.2 kg of 1-aminobenzotriazole (purity ≥98.0%) and 0.6 kg of triethylamine (purity ≥99.0%) were added to the reactor, and the temperature was raised to 70℃ and the reaction was maintained at this temperature for 3 hours. After the reaction was completed, the reaction solution was transferred to a vacuum distillation column and distilled under vacuum conditions of -0.08 MPa and 75℃ to remove ethanol from the system. The distillation residue was placed in a vacuum drying oven and dried under vacuum conditions of 90℃ and -0.09 MPa for 3 hours. After drying, it was ground with a universal pulverizer and passed through an 80-mesh sieve to obtain modified nano-TiO2, which was then sealed and stored for later use.

[0024] The weighed polypropylene resin, antioxidant, ultraviolet absorber, β-nucleating agent, elastomer toughening agent, and modified nano-TiO2 were placed together into a three-dimensional mixer (model SYH-200, speed 150r / min) and mixed for 30 minutes to obtain a mixture. The mixture was then transferred to a hot air drying oven, preheated to 80℃, and dried for 2 hours until the moisture content of the material was ≤0.1%. The dried material was then removed for later use.

[0025] (2) Melt blending and granulation: The preheated and dried mixture is fed into a twin-screw granulator (model SHJ-65, length-to-diameter ratio 40:1). The granulation temperature is set as follows: feeding section 190℃, compression section 200℃, homogenization section 210℃, die head 215℃, and screw speed 200rpm. The material is melt blended, extruded, and granulated to obtain modified polypropylene granules with a particle size of 2-3mm. The granules are cooled to room temperature in a cold air cooler, screened, and sealed for later use.

[0026] (3) Injection molding: The modified polypropylene granules are transferred to a hot air drying oven and dried again (temperature 80℃, time 1 hour) to remove the surface moisture of the granules; the dried granules are sent to an injection molding machine (model HTF-120X, clamping force 1200kN), and the injection parameters are set as follows: melt temperature 200℃ (nozzle temperature 205℃, barrel section 1 195℃, barrel section 2 200℃, barrel section 3 205℃), mold temperature 40℃, injection pressure 60MPa; a special cavity mold for storage boxes is selected (size 30cm×20cm×15cm). During injection, the material in the barrel is injected first. After the mold is filled, the pressure is held for 5 seconds, and then cooled for 30 seconds; after cooling, the mold is opened, the molded product is taken out, the gate and burrs are removed, and the aging-resistant and deformation-resistant plastic storage box is obtained. Example 2

[0027] A method for preparing an aging-resistant and deformation-resistant plastic storage box includes the following steps: (1) Preparation of polypropylene-based modified composite material: Weigh each component accurately by mass, and the specific amounts are as follows: 100 kg of polypropylene resin (homopolymer polypropylene, melting point 167℃, melt flow rate 2.5 g / 10 min, 230℃ / 2.16 kg); 1.0 kg of antioxidant (antioxidant 1010 and antioxidant 168 are compounded in a mass ratio of 1:1, and the purity of both is ≥99.0%); 1.2 kg of ultraviolet absorber (UV-328, purity ≥98.5%, white powder); 0.2 kg of β nucleating agent (NJSTARNU-100 / NJS, purity ≥99.0%); 6 kg of elastomer toughening agent (ASA copolymer, acrylonitrile content 25 wt%, rubber content 30 wt%); 2 kg of reinforcing filler (modified nano TiO2).

[0028] The modified nano-TiO2 is prepared as follows: Weigh 100 kg of nano-TiO2 (anatase type, particle size 35 nm, specific surface area 85 m² / g), 2.0 kg of γ-glycidyl etheroxypropyltrimethoxysilane (purity ≥98.5%), and 1075 kg of ethanol (purity ≥99.7%), and add them all to a 5000 L three-necked reactor; introduce nitrogen gas (flow rate 0.4 m³ / h) into the reactor to remove oxygen and water for 18 minutes; close the nitrogen valve, turn on the stirrer (speed 130 r / min), and stir at room temperature for 35 minutes until the material is evenly dispersed; slowly add 8 kg of deionized water dropwise using a constant pressure dropping funnel until the water is completely added. Afterward, the temperature was raised to 64℃ and the reaction was maintained at that temperature for 2.5 hours. Then, 1.8 kg of 1-aminobenzotriazole (purity ≥98.0%) and 1.4 kg of triethylamine (purity ≥99.0%) were added to the reactor, and the temperature was raised to 74℃ and the reaction was maintained at that temperature for 3.3 hours. After the reaction was completed, the reaction solution was transferred to a vacuum distillation column and distilled under vacuum conditions of -0.082 MPa and 78℃ to remove ethanol from the system. The distillation residue was placed in a vacuum drying oven and dried at 93℃ and -0.09 MPa for 4.5 hours. After drying, it was ground with a universal pulverizer and passed through an 80-mesh sieve to obtain modified nano-TiO2, which was then sealed and stored for later use.

[0029] The weighed polypropylene resin, antioxidant, ultraviolet absorber, β-nucleating agent, elastomer toughening agent, and modified nano-TiO2 were placed together into a three-dimensional mixer (model SYH-200, speed 160r / min) and mixed for 35 minutes to obtain a mixture. The mixture was then transferred to a hot air drying oven, preheated to 90℃, and dried for 3.5 hours until the moisture content of the material was ≤0.1%. The dried material was then removed for later use.

[0030] (2) Melt blending and granulation: The preheated and dried mixture is fed into a twin-screw granulator (model SHJ-65, length-to-diameter ratio 40:1). The granulation temperature is set as follows: feeding section 200℃, compression section 210℃, homogenization section 220℃, die head 225℃, and screw speed 300rpm. The material is melt-blended, extruded, and granulated to obtain modified polypropylene granules with a particle size of 2-3mm. The granules are cooled to room temperature in a cold air cooler, screened, and sealed for later use.

[0031] (3) Injection molding: The modified polypropylene granules are transferred to a hot air drying oven and dried again (temperature 90℃, time 1 hour) to remove the surface moisture of the granules; the dried granules are sent to an injection molding machine (model HTF-120X, clamping force 1200kN), and the injection parameters are set as follows: melt temperature 208℃ (nozzle temperature 213℃, barrel section 1 203℃, barrel section 2 208℃, barrel section 3 213℃), mold temperature 55℃, injection pressure 80MPa; a special cavity mold for storage boxes is selected (size 30cm×20cm×15cm). During injection, the material in the barrel is injected first. After the mold is filled, the pressure is held for 8 seconds, and then cooled for 60 seconds; after cooling, the mold is opened, the molded product is taken out, the gate and burrs are removed, and the aging-resistant and deformation-resistant plastic storage box is obtained. Example 3

[0032] A method for preparing an aging-resistant and deformation-resistant plastic storage box includes the following steps: (1) Preparation of polypropylene-based modified composite material: Weigh each component accurately by mass, and the specific amounts are as follows: 100 kg of polypropylene resin (homopolymer polypropylene, melting point 167℃, melt flow rate 2.5 g / 10 min, 230℃ / 2.16 kg); 1.5 kg of antioxidant (antioxidant 1010 and antioxidant 168 are compounded in a mass ratio of 2:1, and the purity of both is ≥99.0%); 1.8 kg of ultraviolet absorber (UV-327, purity ≥98.5%, light yellow powder); 0.35 kg of β nucleating agent (TMB-5β, purity ≥99.0%); 9 kg of elastomer toughening agent (ethylene propylene rubber EPR, ethylene content 45 wt%, Mooney viscosity ML1+4 (100℃) = 30); 3.5 kg of reinforcing filler (modified nano TiO2).

[0033] The modified nano-TiO2 is prepared as follows: Weigh 100 kg of nano-TiO2 (anatase type, particle size 40 nm, specific surface area 90 m² / g), 2.5 kg of γ-glycidyl etheroxypropyltrimethoxysilane (purity ≥98.5%), and 1150 kg of ethanol (purity ≥99.7%), and add them all to a 5000 L three-necked reactor; introduce nitrogen gas (flow rate 0.5 m³ / h) into the reactor to remove oxygen and water for 25 minutes; close the nitrogen valve, turn on the stirrer (speed 140 r / min), and stir at room temperature for 50 minutes until the material is evenly dispersed; slowly add 12 kg of deionized water dropwise using a constant pressure dropping funnel. After the addition was complete, the temperature was raised to 68℃ and the reaction was maintained at this temperature for 3 hours. Then, 2.6 kg of 1-aminobenzotriazole (purity ≥98.0%) and 2.1 kg of triethylamine (purity ≥99.0%) were added to the reactor, and the temperature was raised to 78℃ and the reaction was maintained at this temperature for 3.7 hours. After the reaction was completed, the reaction solution was transferred to a vacuum distillation column and distilled under vacuum conditions of -0.085 MPa and 82℃ to remove ethanol from the system. The distillation residue was placed in a vacuum drying oven and dried at 97℃ and -0.09 MPa for 6 hours. After drying, it was ground with a universal pulverizer and passed through an 80-mesh sieve to obtain modified nano-TiO2, which was then sealed and stored for later use.

[0034] The weighed polypropylene resin, antioxidant, ultraviolet absorber, β-nucleating agent, elastomer toughening agent, and modified nano-TiO2 were placed together into a three-dimensional mixer (model SYH-200, speed 170r / min) and mixed for 40 minutes to obtain a mixture. The mixture was then transferred to a hot air drying oven, preheated to 100℃, and dried for 5 hours until the moisture content of the material was ≤0.1%. The dried material was then removed for later use.

[0035] (2) Melt blending and granulation: The preheated and dried mixture is fed into a twin-screw granulator (model SHJ-65, length-to-diameter ratio 40:1). The granulation temperature is set as follows: feeding section 210℃, compression section 220℃, homogenization section 230℃, die head 235℃, and screw speed 400rpm. The material is melt blended, extruded, and granulated to obtain modified polypropylene granules with a particle size of 2-3mm. The granules are cooled to room temperature in a cold air cooler, screened, and sealed for later use.

[0036] (3) Injection molding: The modified polypropylene granules are transferred to a hot air drying oven and dried again (temperature 100℃, time 1 hour) to remove the surface moisture of the granules; the dried granules are sent to an injection molding machine (model HTF-120X, clamping force 1200kN), and the injection parameters are set as follows: melt temperature 220℃ (nozzle temperature 225℃, barrel section 1 215℃, barrel section 2 220℃, barrel section 3 225℃), mold temperature 70℃, injection pressure 100MPa; the mold is a special cavity mold for storage boxes (size 30cm×20cm×15cm). During injection, the material in the barrel is injected first. After the mold is filled, the pressure is held for 12 seconds, and then cooled for 90 seconds; after cooling, the mold is opened, the molded product is taken out, the gate and burrs are removed, and the aging-resistant and deformation-resistant plastic storage box is obtained. Example 4

[0037] A method for preparing an aging-resistant and deformation-resistant plastic storage box includes the following steps: (1) Preparation of polypropylene-based modified composite material: Weigh each component accurately by mass, and the specific amounts are as follows: 100 kg of polypropylene resin (homopolymer polypropylene, melting point 167℃, melt flow rate 2.5 g / 10 min, 230℃ / 2.16 kg); 2.0 kg of antioxidant (antioxidant 168, purity ≥99.0%, white powder); 2.5 kg of ultraviolet absorber (UV-328, purity ≥98.5%, white powder); 0.5 kg of β nucleating agent (NJSTARNU-100 / NJS, purity ≥99.0%); 12 kg of elastomer toughening agent (ASA copolymer, acrylonitrile content 28 wt%, rubber content 35 wt%); 5 kg of reinforcing filler (modified nano TiO2).

[0038] The modified nano-TiO2 is prepared as follows: Weigh 100 kg of nano-TiO2 (anatase type, particle size 45 nm, specific surface area 95 m² / g), 3.0 kg of γ-glycidyl etheroxypropyltrimethoxysilane (purity ≥98.5%), and 1200 kg of ethanol (purity ≥99.7%), and add them all to a 5000 L three-necked reactor; introduce nitrogen gas (flow rate 0.6 m³ / h) into the reactor to remove oxygen and water for 30 minutes; close the nitrogen valve, turn on the stirrer (speed 150 r / min), and stir at room temperature for 60 minutes until the material is evenly dispersed; slowly add 15 kg of deionized water dropwise using a constant pressure dropping funnel. After the addition was complete, the temperature was raised to 70℃ and the reaction was maintained at this temperature for 3.5 hours. Then, 3.2 kg of 1-aminobenzotriazole (purity ≥98.0%) and 2.7 kg of triethylamine (purity ≥99.0%) were added to the reactor, and the temperature was raised to 80℃ and the reaction was maintained at this temperature for 4 hours. After the reaction was completed, the reaction solution was transferred to a vacuum distillation column and distilled under vacuum conditions of -0.09 MPa and 85℃ to remove ethanol from the system. The distillation residue was placed in a vacuum drying oven and dried at 100℃ and -0.09 MPa for 7 hours. After drying, it was ground with a universal pulverizer and passed through an 80-mesh sieve to obtain modified nano-TiO2, which was then sealed and stored for later use.

[0039] The weighed polypropylene resin, antioxidant, ultraviolet absorber, β-nucleating agent, elastomer toughening agent, and modified nano-TiO2 were placed together into a three-dimensional mixer (model SYH-200, speed 180r / min) and mixed for 45 minutes to obtain a mixture. The mixture was then transferred to a hot air drying oven, and the preheating and drying temperature was set to 110℃ for 6 hours. The mixture was dried until the moisture content was ≤0.1%, and then removed for later use.

[0040] (2) Melt blending and granulation: The preheated and dried mixture is fed into a twin-screw granulator (model SHJ-65, length-to-diameter ratio 40:1). The granulation temperature is set as follows: feeding section 220℃, compression section 230℃, homogenization section 240℃, die head 245℃, and screw speed 500rpm. The material is melt blended, extruded, and granulated to obtain modified polypropylene granules with a particle size of 2-3mm. The granules are cooled to room temperature in a cold air cooler, screened, and sealed for later use.

[0041] (3) Injection molding: The modified polypropylene granules are transferred to a hot air drying oven for further drying (temperature 110℃, time 1 hour) to remove surface moisture. The dried granules are then fed into an injection molding machine (model HTF-120X, clamping force 1200kN). The injection parameters are set as follows: melt temperature 230℃ (nozzle temperature 235℃, barrel section 1 225℃, barrel section 2 230℃, barrel section 3 235℃), mold temperature 80℃, and injection pressure 120MPa. A special cavity mold for storage boxes (size 30cm×20cm×15cm) is used. During injection, the material in the barrel is injected first. After the mold is filled, the pressure is held for 15 seconds, followed by cooling for 120 seconds. After cooling, the mold is opened, the molded product is removed, the gate and burrs are removed, and the aging-resistant and deformation-resistant plastic storage box is obtained.

[0042] Comparative Example 1 A method for preparing an aging-resistant and deformation-resistant plastic storage box includes the following steps: (1) Preparation of polypropylene-based modified composite material: Weigh each component accurately by mass, and the specific amounts are as follows: 100 kg of polypropylene resin (homopolymer polypropylene, melting point 167℃, melt flow rate 2.5 g / 10 min, 230℃ / 2.16 kg); 0.5 kg of antioxidant (antioxidant 1010, purity ≥99.0%, white powder); 0.5 kg of ultraviolet absorber (UV-327, purity ≥98.5%, pale yellow powder); 0.05 kg of β nucleating agent (TMB-5β, purity ≥99.0%); 3 kg of elastomer toughening agent (ethylene propylene rubber EPR, ethylene content 40 wt%, Mooney viscosity ML1+4 (100℃) = 25); 0.5 kg of reinforcing filler (nano TiO2).

[0043] The weighed polypropylene resin, antioxidant, ultraviolet absorber, β-nucleating agent, elastomer toughening agent, and modified nano-TiO2 were placed together into a three-dimensional mixer (model SYH-200, speed 150r / min) and mixed for 30 minutes to obtain a mixture. The mixture was then transferred to a hot air drying oven, preheated to 80℃, and dried for 2 hours until the moisture content of the material was ≤0.1%. The dried material was then removed for later use.

[0044] (2) Melt blending and granulation: The preheated and dried mixture is fed into a twin-screw granulator (model SHJ-65, length-to-diameter ratio 40:1). The granulation temperature is set as follows: feeding section 190℃, compression section 200℃, homogenization section 210℃, die head 215℃, and screw speed 200rpm. The material is melt blended, extruded, and granulated to obtain modified polypropylene granules with a particle size of 2-3mm. The granules are cooled to room temperature in a cold air cooler, screened, and sealed for later use.

[0045] (3) Injection molding: The modified polypropylene granules are transferred to a hot air drying oven and dried again (temperature 80℃, time 1 hour) to remove the surface moisture of the granules; the dried granules are sent to an injection molding machine (model HTF-120X, clamping force 1200kN), and the injection parameters are set as follows: melt temperature 200℃ (nozzle temperature 205℃, barrel section 1 195℃, barrel section 2 200℃, barrel section 3 205℃), mold temperature 40℃, injection pressure 60MPa; a special cavity mold for storage boxes is selected (size 30cm×20cm×15cm). During injection, the material in the barrel is injected first. After the mold is filled, the pressure is held for 5 seconds, and then cooled for 30 seconds; after cooling, the mold is opened, the molded product is taken out, the gate and burrs are removed, and the aging-resistant and deformation-resistant plastic storage box is obtained.

[0046] Comparative Example 2 A method for preparing an aging-resistant and deformation-resistant plastic storage box includes the following steps: (1) Preparation of polypropylene-based modified composite material: Weigh each component accurately by mass, and the specific amounts are as follows: 100 kg of polypropylene resin (homopolymer polypropylene, melting point 167℃, melt flow rate 2.5 g / 10 min, 230℃ / 2.16 kg); 0.5 kg of antioxidant (antioxidant 1010, purity ≥99.0%, white powder); 0.5 kg of ultraviolet absorber (UV-327, purity ≥98.5%, pale yellow powder); 0.05 kg of β nucleating agent (TMB-5β, purity ≥99.0%); 3 kg of elastomer toughening agent (ethylene propylene rubber EPR, ethylene content 40 wt%, Mooney viscosity ML1+4 (100℃) = 25); 0.5 kg of reinforcing filler (modified nano TiO2).

[0047] The modified nano-TiO2 is prepared as follows: Weigh 100 kg of nano-TiO2 (anatase type, particle size 30 nm, specific surface area 80 m² / g) and 1000 kg of ethanol (purity ≥ 99.7%), and add them all to a 5000 L three-necked reactor; introduce nitrogen gas (flow rate 0.3 m³ / h) into the reactor to remove oxygen and water for 10 minutes; close the nitrogen valve, turn on the stirrer (speed 120 r / min), and stir at room temperature for 20 minutes until the material is evenly dispersed; slowly add 5 kg of deionized water dropwise using a constant pressure dropping funnel; after the addition is complete, raise the temperature to 60 °C and maintain the temperature. The reaction was carried out for 2 hours. Then, 1.2 kg of 1-aminobenzotriazole (purity ≥98.0%) and 0.6 kg of triethylamine (purity ≥99.0%) were added to the reactor, and the temperature was raised to 70℃ and kept at a constant temperature for 3 hours. After the reaction was completed, the reaction solution was transferred to a vacuum distillation column and distilled under vacuum conditions of -0.08 MPa and 75℃ to remove ethanol from the system. The distillation residue was placed in a vacuum drying oven and dried for 3 hours at 90℃ and -0.09 MPa. After drying, it was ground with a universal pulverizer and passed through an 80-mesh sieve to obtain modified nano-TiO2, which was then sealed and stored for later use.

[0048] The weighed polypropylene resin, antioxidant, ultraviolet absorber, β-nucleating agent, elastomer toughening agent, and modified nano-TiO2 were placed together into a three-dimensional mixer (model SYH-200, speed 150r / min) and mixed for 30 minutes to obtain a mixture. The mixture was then transferred to a hot air drying oven, preheated to 80℃, and dried for 2 hours until the moisture content of the material was ≤0.1%. The dried material was then removed for later use.

[0049] (2) Melt blending and granulation: The preheated and dried mixture is fed into a twin-screw granulator (model SHJ-65, length-to-diameter ratio 40:1). The granulation temperature is set as follows: feeding section 190℃, compression section 200℃, homogenization section 210℃, die head 215℃, and screw speed 200rpm. The material is melt blended, extruded, and granulated to obtain modified polypropylene granules with a particle size of 2-3mm. The granules are cooled to room temperature in a cold air cooler, screened, and sealed for later use.

[0050] (3) Injection molding: The modified polypropylene granules are transferred to a hot air drying oven and dried again (temperature 80℃, time 1 hour) to remove the surface moisture of the granules; the dried granules are sent to an injection molding machine (model HTF-120X, clamping force 1200kN), and the injection parameters are set as follows: melt temperature 200℃ (nozzle temperature 205℃, barrel section 1 195℃, barrel section 2 200℃, barrel section 3 205℃), mold temperature 40℃, injection pressure 60MPa; a special cavity mold for storage boxes is selected (size 30cm×20cm×15cm). During injection, the material in the barrel is injected first. After the mold is filled, the pressure is held for 5 seconds, and then cooled for 30 seconds; after cooling, the mold is opened, the molded product is taken out, the gate and burrs are removed, and the aging-resistant and deformation-resistant plastic storage box is obtained.

[0051] Comparative Example 3 A method for preparing an aging-resistant and deformation-resistant plastic storage box includes the following steps: (1) Preparation of polypropylene-based modified composite material: Weigh each component accurately by mass, and the specific amounts are as follows: 100 kg of polypropylene resin (homopolymer polypropylene, melting point 167℃, melt flow rate 2.5 g / 10 min, 230℃ / 2.16 kg); 0.5 kg of antioxidant (antioxidant 1010, purity ≥99.0%, white powder); 0.5 kg of ultraviolet absorber (UV-327, purity ≥98.5%, pale yellow powder); 0.05 kg of β nucleating agent (TMB-5β, purity ≥99.0%); 3 kg of elastomer toughening agent (ethylene propylene rubber EPR, ethylene content 40 wt%, Mooney viscosity ML1+4 (100℃) = 25); 0.5 kg of reinforcing filler (modified nano TiO2).

[0052] The modified nano-TiO2 is prepared as follows: Weigh 100 kg of nano-TiO2 (anatase type, particle size 30 nm, specific surface area 80 m² / g), 1.5 kg of γ-glycidyl etheroxypropyltrimethoxysilane (purity ≥98.5%), and 1000 kg of ethanol (purity ≥99.7%), and add them all to a 5000 L three-necked reactor; introduce nitrogen gas (flow rate 0.3 m³ / h) into the reactor to remove oxygen and water for 10 minutes; close the nitrogen valve, turn on the stirrer (speed 120 r / min), and stir at room temperature for 20 minutes until the material is evenly dispersed; use a constant pressure dropping filter... 5 kg of deionized water was slowly added dropwise to the reactor. After the addition was complete, the temperature was raised to 60°C and the reaction was maintained at this temperature for 2 hours. Then, 0.6 kg of triethylamine (purity ≥99.0%) was added to the reactor, and the temperature was raised to 70°C and the reaction was maintained at this temperature for 3 hours. After the reaction was completed, the reaction solution was transferred to a vacuum distillation column and distilled under vacuum conditions of -0.08 MPa and 75°C to remove ethanol from the system. The distillation residue was placed in a vacuum drying oven and dried at 90°C and -0.09 MPa for 3 hours. After drying, it was ground with a universal pulverizer and passed through an 80-mesh sieve to obtain modified nano-TiO2, which was then sealed and stored for later use.

[0053] The weighed polypropylene resin, antioxidant, ultraviolet absorber, β-nucleating agent, elastomer toughening agent, and modified nano-TiO2 were placed together into a three-dimensional mixer (model SYH-200, speed 150r / min) and mixed for 30 minutes to obtain a mixture. The mixture was then transferred to a hot air drying oven, preheated to 80℃, and dried for 2 hours until the moisture content of the material was ≤0.1%. The dried material was then removed for later use.

[0054] (2) Melt blending and granulation: The preheated and dried mixture is fed into a twin-screw granulator (model SHJ-65, length-to-diameter ratio 40:1). The granulation temperature is set as follows: feeding section 190℃, compression section 200℃, homogenization section 210℃, die head 215℃, and screw speed 200rpm. The material is melt blended, extruded, and granulated to obtain modified polypropylene granules with a particle size of 2-3mm. The granules are cooled to room temperature in a cold air cooler, screened, and sealed for later use.

[0055] (3) Injection molding: The modified polypropylene granules are transferred to a hot air drying oven and dried again (temperature 80℃, time 1 hour) to remove the surface moisture of the granules; the dried granules are sent to an injection molding machine (model HTF-120X, clamping force 1200kN), and the injection parameters are set as follows: melt temperature 200℃ (nozzle temperature 205℃, barrel section 1 195℃, barrel section 2 200℃, barrel section 3 205℃), mold temperature 40℃, injection pressure 60MPa; a special cavity mold for storage boxes is selected (size 30cm×20cm×15cm). During injection, the material in the barrel is injected first. After the mold is filled, the pressure is held for 5 seconds, and then cooled for 30 seconds; after cooling, the mold is opened, the molded product is taken out, the gate and burrs are removed, and the aging-resistant and deformation-resistant plastic storage box is obtained.

[0056] Test method: I. Aging Resistance Test Test objective: To evaluate the retention of mechanical properties of the aging-resistant and deformation-resistant plastic storage box prepared in the example under accelerated photoaging conditions.

[0057] Test standards / methods The UV light source specified in ISO 4892-3 (accelerated UV aging test for plastic materials) was used to simulate the natural light environment and the UV aging test conditions.

[0058] The samples were tested in an accelerated aging test chamber under UV-A 340nm irradiation conditions (8 hours of irradiation + 4 hours of condensation per cycle).

[0059] Samples were taken out at different aging time points and subjected to mechanical property testing after being placed at 23±2℃ for 24 hours.

[0060] Test result metrics Tensile strength retention rate (tensile strength after aging / tensile strength before aging × 100%) Elongation at break retention rate (ratio of elongation after aging to elongation before aging) Test results: Table 1 Results of Aging Resistance Test Accelerated aging time (h) Tensile strength retention rate (%) Elongation at break retention (%) Example 1 500 87.5 81.7 Example 2 500 88.1 82.4 Example 3 500 88.7 82.8 Example 4 500 89.3 83.1 Comparative Example 1 500 85.2 79.0 Comparative Example 2 500 86.1 79.8 Comparative Example 3 500 86.4 80.1 II. Deformation (Creep) Resistance Test Test objective: To evaluate the long-term creep resistance of materials under constant static load conditions.

[0061] Test standards / methods Tensile creep tests were performed on the specimens according to ASTM D 2990 standard, and the deformation of the material over time was monitored under constant load and constant temperature.

[0062] Note: ASTM D 2990 is the internationally recognized test method for creep and creep rupture of plastics.

[0063] The standard sample size (10 mm width × 4 mm thickness × 180 mm length) was used, and measurements were taken under specific load (10 kg) and room temperature conditions.

[0064] Test cycle After initial deformation is recorded, static load is maintained for 168 hours (7 days) and deformation data is recorded. Table 2 Results of Deformation (Creep) Resistance Test Initial height (mm) 168 h Static load height (mm) Deformation rate (%) Example 1 50 48.8 2.40% Example 2 50 49.1 1.80% Example 3 50 49.3 1.40% Example 4 50 49.4 1.20% Comparative Example 1 50 48.1 3.80% Comparative Example 2 50 48.4 3.20% Comparative Example 3 50 48.5 3.00% After modified nano-TiO2 was used as a reinforcing filler in the preparation of polypropylene-based plastic storage boxes, the test data of the material's aging resistance and deformation resistance showed a significant improvement trend. This result fully verifies the synergistic effect and functional value of each compound in the modified additive. γ-glycidyl etheroxypropyltrimethoxysilane serves as the core coupling agent, with its siloxane group achieving chemical grafting with nano-TiO2. The organic segment effectively enhances the interfacial bonding between the inorganic filler and the polypropylene organic matrix, laying the structural foundation for maintaining the material's mechanical properties and improving its resistance to deformation. 1-Aminobenzotriazole is successfully grafted onto the surface of nano-TiO2 via a ring-opening reaction. Its benzotriazole functional groups possess excellent UV absorption capabilities, forming a dual UV protection with the added UV absorber, effectively reducing UV damage to the polypropylene molecular chains. Therefore, in accelerated photoaging tests, the tensile strength and elongation at break of the material are significantly improved. Triethylamine, as a catalyst, efficiently catalyzes the ring-opening addition reaction between epoxy and amino groups, ensuring the successful grafting of benzotriazole functional groups onto the nano-TiO2 surface, guaranteeing the modification effect and stability, and allowing the UV absorption modification effect of nano-TiO2 to be fully utilized. Meanwhile, the improved interfacial bonding allows the modified nano-TiO2 to better fulfill its reinforcing role. In the creep test under constant static load, the deformation of the material is significantly reduced and the dimensional stability is significantly improved, which fully demonstrates the key role of each modified compound in improving the overall performance of the material and proves the excellent application effect of modified nano-TiO2 as a reinforcing filler.

[0065] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an aging-resistant and deformation-resistant plastic storage box, characterized in that, Includes the following steps: (1) Prepare a polypropylene-based modified composite material, which, by mass parts, includes: Polypropylene resin: 100 parts; Antioxidant: 0.5–2.0 parts; Ultraviolet absorber: 0.5–2.5 parts; β-nucleating agent: 0.05–0.5 parts; Elastomer toughening agent: 3-12 parts; Reinforcing filler: 0.5–5 parts; (2) Mix the above components according to the proportion range specified in step (1), preheat and dry them, and then melt-blend and granulate them in a twin-screw granulator at a temperature of 190-240℃ and a speed of 200-500rpm to obtain modified polypropylene granules. (3) The obtained modified polypropylene granules were dried and then injection molded in an injection molding machine under the conditions of melt temperature 200-230℃, mold temperature 40-80℃ and injection pressure 60-120MPa to obtain an aging-resistant and deformation-resistant plastic storage box. The reinforcing filler is prepared by reacting nano-TiO2, γ-glycidoxypropyltrimethoxysilane, deionized water, 1-aminobenzotriazole, and triethylamine.

2. The method for preparing an aging-resistant and deformation-resistant plastic storage box according to claim 1, characterized in that: The antioxidant is selected from 1010 or 168 or a combination thereof.

3. The method for preparing an aging-resistant and deformation-resistant plastic storage box according to claim 1, characterized in that: The ultraviolet absorber is selected from UV-327 or UV-328.

4. The method for preparing an aging-resistant and deformation-resistant plastic storage box according to claim 1, characterized in that: The β-nucleating agent is selected from TMB-5β or NJSTARNU-100 / NJS.

5. The method for preparing an aging-resistant and deformation-resistant plastic storage box according to claim 1, characterized in that: The elastomer toughening agent is selected from ethylene propylene rubber (EPR) or ASA copolymer.

6. The method for preparing an aging-resistant and deformation-resistant plastic storage box according to claim 1, characterized in that: The reinforcing filler is modified nano-TiO2, and its preparation method is as follows: According to the mass fractions, 100 parts of nano-TiO2, 1.5-3.0 parts of γ-glycidyl etheroxypropyltrimethoxysilane, and 1000-1200 parts of ethanol were added to a reaction vessel. Nitrogen gas was introduced to remove oxygen and water for 10-30 minutes, and the mixture was stirred at room temperature for 20-60 minutes until it was evenly dispersed. 5-15 parts of deionized water were added dropwise, and the temperature was raised to 60-70℃ and reacted for 2-3.5 hours. 1.2-3.2 parts of 1-aminobenzotriazole were added, followed by 0.6-2.7 parts of triethylamine. The temperature was raised to 70-80℃ and the reaction was continued for 3-4 hours. After the reaction was completed, toluene was removed by vacuum distillation, and the mixture was dried under vacuum at 90-100℃ for 3-7 hours and then ground through an 80-mesh sieve to obtain modified nano-TiO2.

7. The method for preparing an aging-resistant and deformation-resistant plastic storage box according to claim 1, characterized in that: The preheating and drying temperature is 80-110℃ and the time is 2-6 hours.

8. The method for preparing an aging-resistant and deformation-resistant plastic storage box according to claim 1, characterized in that: The injection molding process involves holding pressure for 5–15 seconds and cooling for 30–120 seconds.