Weatherable polypropylene composite for a toy dragon and method of making the same

Abstract

This invention discloses a weather-resistant polypropylene composite material for toy dragons, comprising the following components in parts by weight: 100 parts polypropylene resin, 15-25 parts metallocene ethylene-octene copolymer, 3-5 parts polypropylene grafted maleic anhydride compatibilizer, 2-4 parts rutile nano-titanium dioxide, 0.3-0.6 parts benzotriazole UV absorber, 0.3-0.5 parts low molecular weight hindered amine light stabilizer, 0.2-0.4 parts high molecular weight hindered amine light stabilizer, 0.1-0.2 parts hindered phenolic primary antioxidant, 0.1-0.2 parts phosphite secondary antioxidant, and 0.5-1.0 parts lubricant and dispersant. This invention uses a fully saturated main-chain metallocene ethylene-octene copolymer to replace traditional unsaturated rubber for toughening, and combines it with a three-level synergistic light stabilization system composed of nano-titanium dioxide, ultraviolet absorbers and high and low molecular weight hindered amine light stabilizers, so that the material has excellent long-term weather resistance, high color fastness and excellent low-temperature impact resistance.

Description

Technical Field

[0001] This invention relates to the field of organic composite materials technology, and in particular to a weather-resistant polypropylene composite material for toy dragons. Background Technology

[0002] Polypropylene (PP) is widely used in the toy manufacturing industry due to its advantages such as low density, balanced mechanical properties, chemical corrosion resistance, easy processing and molding, and low cost. It is especially suitable for making products with complex shapes, rich colors, and mass production requirements, such as toy dragons.

[0003] However, when such toys are displayed outdoors or exposed to direct sunlight and significant temperature differences between day and night, ordinary polypropylene materials are highly susceptible to photo-oxidative degradation. This leads to problems such as color fading, surface chalking, decreased gloss, and a rapid deterioration of mechanical properties within a short period. More significantly, toys with complex shapes, such as dragons, are prone to drops and impacts during actual use. Polypropylene's impact strength decreases significantly at low temperatures (below -10°C), exhibiting brittle fracture characteristics. This makes protruding parts like dragon claws and horns extremely vulnerable to cracking or breakage during outdoor play in winter, severely impacting its lifespan and children's safety. To improve the impact resistance and weather resistance of polypropylene, current technologies typically employ elastomer toughening combined with light stabilizers. The most commonly used toughening agents are ethylene propylene diene monomer (EPDM) or styrene-based block copolymers (SBS), whose main chains contain numerous unsaturated double bonds. While these elastomers can effectively improve notched impact strength at room temperature, under the combined effects of long-term ultraviolet irradiation and thermo-oxidative environments, unsaturated double bonds, as structural weaknesses, will break first, triggering the degradation and destruction of the toughening phase itself. This further catalyzes the chain decomposition of the polypropylene matrix, macroscopically manifesting as powdering and cracking of the material from the outside in, ultimately resulting in the loss of toughening function and accelerated deterioration of mechanical properties. Simultaneously, EPDM and PP have limited compatibility; even with the addition of compatibilizers, the dispersed phase size and interfacial adhesion level are insufficient to fully meet the requirements for high toughness at low temperatures, resulting in a relatively low impact strength near -20°C. Regarding light stabilization treatment, existing technical solutions mostly employ single or simple compounding methods. For example, adding benzotriazole or benzophenone ultraviolet absorbers alone only absorbs a portion of ultraviolet light energy and dissipates it as heat, lacking the ability to inhibit unabsorbed ultraviolet light and subsequently generated reactive free radicals. While hindered amine light stabilizers can capture free radicals, low molecular weight varieties are prone to migration and loss, while high molecular weight varieties, due to their low migration rate, are difficult to form effective early protection on the product surface. Some formulations directly add carbon black as a UV shielding agent, but this only meets the needs of black products and is unsuitable for products like toy dragons that require highly saturated colors and vibrant appearances. Furthermore, coloring systems lacking effective UV shielding and free radical capture synergistically suffer from extremely poor colorfastness, often resulting in severe irreversible fading after xenon lamp aging. In addition, to ensure material flexibility or processability, some existing technologies use phthalate plasticizers or introduce inorganic pigments containing heavy metals such as lead, chromium, and cadmium to achieve vibrant colors. These substances are strictly restricted by EU regulations such as EN71-3 and REACH, posing health risks when children bite or come into contact with them. In terms of molding, conventional toughened polypropylene has a low melt flow rate, making it difficult to fill the dense and fine dragon scales, claws, and other complex structures on the surface of toy dragons. This easily leads to defects such as material shortages and weld lines, resulting in long molding cycles and low yield rates.

[0004] In summary, there is an urgent need to develop a polypropylene composite material that combines long-term weather resistance, excellent low-temperature toughness, high color fastness, safety and environmental friendliness, and suitability for injection molding of complex structures, in order to fully meet the stringent requirements of products such as outdoor toy dragons. Summary of the Invention

[0005] Therefore, it is necessary to provide a weather-resistant polypropylene composite material for toy dragons to address the technical problems of insufficient weather resistance and low-temperature toughness of existing toy materials.

[0006] A weather-resistant polypropylene composite material for toy dragons, comprising the following components in parts by weight: Polypropylene resin: 100 parts; Metallocene ethylene-octene copolymer: 15-25 parts; Polypropylene grafted with maleic anhydride compatibilizer: 3-5 parts; Rutile nano-titanium dioxide: 2-4 parts; Benzotriazole UV absorbers: 0.3~0.6 parts; Low molecular weight hindered amine light stabilizer: 0.3~0.5 parts; High molecular weight hindered amine light stabilizer: 0.2~0.4 parts; Hindered phenolic primary antioxidant: 0.1~0.2 parts; Phosphite-based auxiliary antioxidants: 0.1~0.2 parts; Lubricating dispersant: 0.5~1.0 parts.

[0007] In one embodiment, the polypropylene resin is a high-impact copolymer polypropylene with a melt flow rate of 20~30 g / 10 min at 230°C and 2.16 kg load.

[0008] In one embodiment, the metallocene ethylene-octene copolymer has an octene content of 20-40 wt%, a density of 0.86-0.89 g / cm³, and a melt index of 0.5-5 g / 10 min at 190°C and a load of 2.16 kg.

[0009] In one embodiment, the rutile nano-titanium dioxide has an average particle size of 30-50 nm and its surface is coated with an alumina and / or stearic acid treatment layer.

[0010] In one embodiment, the low molecular weight hindered amine light stabilizer is bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, and the high molecular weight hindered amine light stabilizer is poly{[6-[(1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-di][(2,2,6,6-tetramethylpiperidinyl)imino]-1,6-hexanediol}.

[0011] In one embodiment, the benzotriazole UV absorber is 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole.

[0012] In one embodiment, the composite material further comprises a colorant, which is a heavy metal-free organic pigment or masterbatch, and is used in an amount of 0.5 to 5 parts by weight.

[0013] In one embodiment, the lubricating dispersant is ethylene bis-stearamide and / or calcium stearate.

[0014] A method for preparing the weather-resistant polypropylene composite material for toy dragons includes the following steps: S1. The rutile nano-titanium dioxide, benzotriazole UV absorber, low molecular weight hindered amine light stabilizer, high molecular weight hindered amine light stabilizer, hindered phenolic primary antioxidant, phosphite auxiliary antioxidant, and metallocene ethylene-octene copolymer accounting for 5% to 30% of the total weight of the metallocene ethylene-octene copolymer are premixed to obtain a composite additive premix. S2. The polypropylene resin, the remaining metallocene ethylene-octene copolymer, the polypropylene grafted maleic anhydride compatibilizer and the lubricating dispersant are added to the main feed port of the twin-screw extruder. The composite additive premix obtained in step S1 and the optional colorant are added to the twin-screw extruder through the side feed port for melt blending extrusion. After cooling and pelletizing, the weather-resistant polypropylene composite material is obtained.

[0015] In one embodiment, the premixing in step S1 is carried out in a high-speed mixer at a temperature of 50-70°C for 3-10 minutes.

[0016] In one embodiment, the length-to-diameter ratio (L / D) of the twin-screw extruder in step S2 is 40:1, the temperature zone from the main feed port to the die head is set to 160~210℃, and the maximum temperature throughout the process does not exceed 215℃.

[0017] In one embodiment, the screw speed of the twin-screw extruder in step S2 is 300~400 rpm, and vacuum devolatilization is performed during the melt blending extrusion process, with a vacuum degree of -0.06~-0.09 MPa.

[0018] In one embodiment, after pelletizing in step S2, the process further includes drying the resulting particles at 80-90°C until the moisture content is below 0.05%, and then molding the dried particles into a toy dragon part by injection molding.

[0019] In one embodiment, the injection temperature of the injection molding is 200~220°C, and the mold temperature is 30~50°C.

[0020] The aforementioned weather-resistant polypropylene composite material for toy dragons uses a fully saturated main-chain metallocene ethylene-octene copolymer (POE) instead of traditional rubbers such as EPDM containing unsaturated double bonds as a toughening component. This fundamentally eliminates the chain degradation reaction caused by double bond breakage under ultraviolet light and heat-oxidation, allowing the material to maintain excellent elasticity and impact resistance even under long-term exposure. In particular, its notched impact strength at -20℃ can reach 15 kJ / m. 2 The above completely solves the problem of toy dragons cracking easily after being dropped outdoors in winter. Simultaneously, the compounded polypropylene grafted maleic anhydride compatibilizer significantly refines the POE dispersed phase domains, further improving the balance between rigidity and toughness. Regarding light stability, the formula constructs a triple protective barrier: rutile nano-titanium dioxide, benzotriazole UV absorber, and low / high molecular weight hindered amine light stabilizer (HALS). Nano-titanium dioxide initially blocks ultraviolet rays through reflection and absorption; the UV absorber dissipates the transmitted UV energy as harmless heat; low molecular weight HALS rapidly migrates to the surface to capture initial free radicals, while high molecular weight HALS continuously and effectively inhibits internal photo-oxidation. These three components form a full-cycle protective network from the surface to the interior, from immediate to long-term effects, ensuring that the color difference ΔE remains below 2.1 after 2000 hours of xenon lamp aging, with no powdering or cracking on the surface. The synergistic effect of the primary and secondary antioxidants ensures thermo-oxidative stability during repeated heat processing and long-term use. Furthermore, the formula contains no phthalate plasticizers and offers the option of free heavy metal colorants, fully complying with children's toy safety regulations. This composite material also boasts high flowability, allowing for perfect injection molding of intricate structures such as dragon scales and claws, with a short molding cycle. It provides an ideal material solution for toy dragons, combining high weather resistance, high safety, high impact resistance, and excellent moldability. Detailed Implementation

[0021] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0022] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the appendix. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0023] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0024] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0025] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0026] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation. Example 1

[0027] This invention discloses a weather-resistant polypropylene composite material for toy dragons, which comprises the following components in parts by weight: Polypropylene resin: 100 parts; Metallocene ethylene-octene copolymer: 15-25 parts; Polypropylene grafted with maleic anhydride compatibilizer: 3-5 parts; Rutile nano-titanium dioxide: 2-4 parts; Benzotriazole UV absorbers: 0.3~0.6 parts; Low molecular weight hindered amine light stabilizer: 0.3~0.5 parts; High molecular weight hindered amine light stabilizer: 0.2~0.4 parts; Hindered phenolic primary antioxidant: 0.1~0.2 parts; Phosphite-based auxiliary antioxidants: 0.1~0.2 parts; Lubricating dispersant: 0.5~1.0 parts.

[0028] This solution addresses the root cause of accelerated UV aging in traditional unsaturated rubbers (such as EPDM) due to double bond breakage in the main chain by introducing a fully saturated main-chain metallocene ethylene-octene copolymer (POE) as a toughening agent. Simultaneously, a three-tiered synergistic photostable system composed of "nano-titanium dioxide (inorganic UV shielding) + benzotriazole (organic UV absorption) + high and low molecular weight HALS (free radical capture)" provides highly efficient protection across the entire wavelength range and over long periods. This results in a composite material exhibiting excellent long-term outdoor weather resistance, high color fastness, and durable low-temperature toughness, fully meeting the usage requirements of toy dragons in complex outdoor environments. Furthermore, the formulation is free of phthalate plasticizers harmful to children.

[0029] Furthermore, the polypropylene resin is a high-impact copolymer polypropylene, with a melt flow rate of 20-30 g / 10 min at 230°C and a load of 2.16 kg. This embodiment ensures the rigidity and impact resistance of the matrix material itself, while giving the composite material excellent melt flowability. This allows it to completely replicate the complex details of the toy dragon (such as scales and claws) during injection molding, effectively avoiding defects such as material shortages and weld lines, shortening the molding cycle, and improving the yield rate.

[0030] Furthermore, the metallocene ethylene-octene copolymer has an octene content of 20-40 wt%, a density of 0.86-0.89 g / cm³, and a melt flow index of 0.5-5 g / 10 min at 190°C and a load of 2.16 kg. This embodiment ensures that the elastomer has an extremely low glass transition temperature (approximately -55°C) and good compatibility with PP. While significantly improving the impact strength of the composite material at room temperature and low temperatures (e.g., -20°C), the rigidity of the material is not excessively sacrificed due to the addition of the elastomer, ensuring that the toy dragon does not crack when dropped outdoors in cold winter regions.

[0031] Furthermore, the rutile nano-titanium dioxide has an average particle size of 30-50 nm, and its surface is coated with an alumina and / or stearic acid treatment layer. The 30-50 nm particle size efficiently reflects and absorbs ultraviolet light, while the alumina or stearic acid treatment layer on the surface greatly improves the dispersibility of the nanoparticles in the polypropylene matrix, preventing agglomeration. This not only enhances the ultraviolet shielding efficiency but also prevents stress concentration caused by nanoparticle agglomeration, maintaining the mechanical properties of the composite material.

[0032] Furthermore, the low molecular weight hindered amine light stabilizer is bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, and the high molecular weight hindered amine light stabilizer is poly{[6-[(1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-di][(2,2,6,6-tetramethylpiperidinyl)imino]-1,6-hexanediol}. Low molecular weight HALS have a fast migration rate, enabling them to rapidly capture free radicals generated on the surface during the initial stages of product use, providing immediate protection; high molecular weight HALS are resistant to migration and extraction, and can continuously exert a long-term stabilizing effect throughout the entire product lifecycle. The synergistic effect of both can inhibit surface chalking and cracking for a long period.

[0033] Furthermore, the benzotriazole UV absorber is 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole. This absorber has a strong and broad absorption peak in the 290-400 nm UV band and can dissipate UV light energy in the form of harmless thermal energy, effectively protecting the polypropylene backbone. It synergizes with nano-TiO2 and HALS in the formulation through different mechanisms, greatly enhancing the bulk protection of the matrix resin.

[0034] Furthermore, the composite material also includes a colorant, which is a heavy metal-free organic pigment or masterbatch, used in an amount of 0.5 to 5 parts by weight. This embodiment, while providing the toy dragon with diverse and vibrant colors to meet design requirements, strictly ensures the chemical safety and environmental friendliness of the materials, fully meeting the limits for migratable heavy metal elements in toy safety standards such as EU EN71-3, thus protecting children's health while playing or chewing.

[0035] Furthermore, the lubricating dispersant is ethylene bis-stearamide and / or calcium stearate. Ethylene bis-stearamide or calcium stearate can effectively reduce the friction between the resin melt and the metal surface of the processing equipment, improve the release properties, and at the same time assist in the uniform dispersion of pigments and nanofillers in the matrix, ultimately improving the surface finish and color uniformity of the product. Example 2

[0036] A method for preparing the weather-resistant polypropylene composite material for toy dragons includes the following steps: S1. The rutile nano-titanium dioxide, benzotriazole UV absorber, low molecular weight hindered amine light stabilizer, high molecular weight hindered amine light stabilizer, hindered phenolic primary antioxidant, phosphite auxiliary antioxidant, and metallocene ethylene-octene copolymer accounting for 5% to 30% of the total weight of the metallocene ethylene-octene copolymer are premixed to obtain a composite additive premix. S2. The polypropylene resin, the remaining metallocene ethylene-octene copolymer, the polypropylene grafted maleic anhydride compatibilizer and the lubricating dispersant are added to the main feed port of the twin-screw extruder. The composite additive premix obtained in step S1 and the optional colorant are added to the twin-screw extruder through the side feed port for melt blending extrusion. After cooling and pelletizing, the weather-resistant polypropylene composite material is obtained.

[0037] The preparation method in this embodiment involves first encapsulating and premixing the nanoparticles and the thermosensitive light stabilizer with a small amount of elastomer, and then adding them to the polymer melt section via side feeding. This significantly improves the dispersion uniformity of low-dosage, low-bulk-density additives and minimizes the thermal decomposition loss of the light stabilizer under high temperature and strong shear throughout the extrusion process, which is key to maximizing the formulation design effect.

[0038] Furthermore, the premixing described in step S1 is carried out in a high-speed mixer at a temperature of 50~70℃ for 3~10 minutes. Under moderate temperature and shear conditions, the softened POE particles can uniformly encapsulate nano- and powdered additives, forming an effective "powder-coated" structure. This ensures that all trace components are fully mixed, laying the foundation for excellent dispersion in the subsequent main extrusion process and preventing the material from overheating and oxidizing.

[0039] Furthermore, the twin-screw extruder described in step S2 has an L / D ratio of 40:1, and the temperature zones from the main feed inlet to the die head are set at 160~210℃, with the maximum temperature throughout the process not exceeding 215℃. The 40:1 L / D ratio provides sufficient residence time and mixing strength, ensuring the thorough and uniform dispersion of all components, especially nanoparticles. Strict stepped temperature control and maximum temperature limits effectively prevent the high-temperature failure of heat-sensitive additives such as hindered amine light stabilizers while ensuring complete plasticization of polypropylene.

[0040] Furthermore, in step S2, the twin-screw extruder operates at a screw speed of 300-400 rpm, and vacuum devolatilization is performed during the melt blending extrusion process, with a vacuum level of -0.06 to -0.09 MPa. The 300-400 rpm speed matches the production output and reasonable shear heat, ensuring blend quality. Vacuum devolatilization efficiently removes residual moisture, low-molecular-weight volatiles, and air from the melt, eliminating microscopic defects within the material and improving the density and final mechanical properties of the composite material.

[0041] Furthermore, after pelletizing in step S2, the process includes drying the resulting particles at 80-90°C until the moisture content is below 0.05%, and then injection molding the dried particles to produce toy dragon parts. The drying process strictly controls the moisture content, preventing defects such as silver streaks and bubbles from forming in the parts due to moisture vaporization during injection molding. Extending the overall method to the parts protects the complete manufacturing process from raw materials to the final toy product.

[0042] Furthermore, the injection temperature for injection molding is 200~220℃, and the mold temperature is 30~50℃. Reasonable injection and mold temperatures ensure that the melt has appropriate viscosity and flow length when filling complex cavities, perfectly replicating fine structures while achieving sufficient pressure holding and shrinkage compensation, avoiding flash and surface depressions, and ensuring a dense structure and exquisite appearance for the toy dragon. Example 3

[0043] Unlike Example 1, the weather-resistant polypropylene composite material used for the toy dragon comprises the following components in parts by weight: PP: 100 parts, POE: 15 parts, PP-g-MAH: 3 parts, nano TiO2: 2 parts, UV-326: 0.3 parts, light stabilizer 770: 0.3 parts, light stabilizer 944: 0.2 parts, antioxidant 1010: 0.15 parts, antioxidant 168: 0.15 parts, EBS: 0.5 parts, and green masterbatch: 2 parts.

[0044] Unlike Example 2, the preparation method of the weather-resistant polypropylene composite material for the toy dragon includes the following steps: Additive premixing: Take 10% of the total POE (i.e., 1.5 parts) of POE and mix it with nano-... UV-326, light stabilizer 770, light stabilizer 944, antioxidant 1010, and antioxidant 168 are mixed in a high-speed mixer at 60°C and 800 rpm for 5 minutes to obtain a composite additive premix. Extrusion granulation: The remaining 13.5 parts POE, 100 parts PP, 3 parts PP-g-MAH, and 0.5 parts EBS are added to the main feed port of a twin-screw extruder. The premix from step 1 and the masterbatch are added through the side feed port in zone 3. The extruder length-to-diameter ratio (L / D) is... =40:1, temperature settings: Zone 1 165℃, Zone 2 185℃, Zone 3 195℃, Zone 4 200℃, Zone 5 205℃, die head 200℃, maximum temperature throughout ≤210℃; screw speed 350rpm, vacuum devolatilization -0.08MPa; extrudate water cooling, air drying and pelletizing; drying and injection molding: particles are dried at 80℃ for 2 hours to a moisture content of 0.03%, and then injection molded into standard test specimens and toy dragon parts at an injection temperature of 210℃ and a mold temperature of 40℃. Example 4

[0045] Unlike Example 1, the weather-resistant polypropylene composite material used for the toy dragon comprises the following components in parts by weight: PP: 100 parts, POE: 20 parts, PP-g-MAH: 4 parts, nano- 3 parts, UV-326: 0.45 parts, light stabilizer 770: 0.4 parts, light stabilizer 944: 0.3 parts, antioxidant 1010: 0.15 parts, antioxidant 168: 0.15 parts, EBS: 0.7 parts, green masterbatch: 2 parts.

[0046] Unlike Example 2, the preparation method of the weather-resistant polypropylene composite material for the toy dragon includes the following steps: Additive premixing: Take 3 parts of POE (15% of the total POE) and mix it with all powder additives at 60°C for 5 minutes at high speed; Extrusion granulation: The main feed material is 17 parts of POE, and the rest is the same as in Example 2. The extruder temperature is set consistently, and the screw speed is 380 rpm; Drying and injection molding: Same as in Example 2. Example 5

[0047] Unlike Example 1, the weather-resistant polypropylene composite material used for the toy dragon comprises the following components in parts by weight: PP: 100 parts, POE: 25 parts, PP-g-MAH: 5 parts, nano- 4 parts, UV-326: 0.6 parts, light stabilizer 770: 0.5 parts, light stabilizer 944: 0.4 parts, antioxidant 1010: 0.2 parts, antioxidant 168: 0.2 parts, EBS: 1.0 part, green masterbatch: 2 parts.

[0048] Unlike Example 2, the additives were premixed as follows: 5 parts of POE (20% of the total POE) were mixed with all powder additives at 70°C for 4 minutes at high speed. Extrusion granulation: The remaining 20 parts of POE were added to the main feed. Extrusion temperatures were: Zone 1 170°C, Zone 2 190°C, Zone 3 200°C, Zone 4 210°C, Zone 5 210°C, die head 205°C, and ≤215°C throughout the process. Rotation speed was 300 rpm, and vacuum was -0.09 MPa. Drying and injection molding were performed as in Example 2.

[0049] In summary, the weather-resistant polypropylene composite material for toy dragons disclosed in this invention uses a fully saturated main-chain metallocene ethylene-octene copolymer (POE) instead of traditional rubbers such as EPDM containing unsaturated double bonds as the toughening component. This fundamentally eliminates the chain degradation reaction caused by double bond breakage under ultraviolet light and heat-oxidation, allowing the material to maintain excellent elasticity and impact resistance even under long-term exposure, especially with a notched impact strength of up to 15 kJ / m at -20℃. 2 The above completely solves the problem of toy dragons cracking easily after being dropped outdoors in winter. Simultaneously, the compounded polypropylene grafted maleic anhydride compatibilizer significantly refines the POE dispersed phase domains, further improving the balance between rigidity and toughness. Regarding light stability, the formula constructs a triple protective barrier: rutile nano-titanium dioxide, benzotriazole UV absorber, and low / high molecular weight hindered amine light stabilizer (HALS). Nano-titanium dioxide initially blocks ultraviolet rays through reflection and absorption; the UV absorber dissipates the transmitted UV energy as harmless heat; low molecular weight HALS rapidly migrates to the surface to capture initial free radicals, while high molecular weight HALS continuously and effectively inhibits internal photo-oxidation. These three components form a full-cycle protective network from the surface to the interior, from immediate to long-term effects, ensuring that the color difference ΔE remains below 2.1 after 2000 hours of xenon lamp aging, with no powdering or cracking on the surface. The synergistic effect of the primary and secondary antioxidants ensures thermo-oxidative stability during repeated heat processing and long-term use. Furthermore, the formula contains no phthalate plasticizers and offers the option of free heavy metal colorants, fully complying with children's toy safety regulations. This composite material also boasts high flowability, allowing for perfect injection molding of intricate structures such as dragon scales and claws, with a short molding cycle. It provides an ideal material solution for toy dragons, combining high weather resistance, high safety, high impact resistance, and excellent moldability.

[0050] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0051] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A weather-resistant polypropylene composite material for toy dragons, characterized in that, The components include the following parts by weight: Polypropylene resin: 100 parts; Metallocene ethylene-octene copolymer: 15-25 parts; Polypropylene grafted with maleic anhydride compatibilizer: 3-5 parts; Rutile nano-titanium dioxide: 2-4 parts; Benzotriazole UV absorbers: 0.3~0.6 parts; Low molecular weight hindered amine light stabilizer: 0.3~0.5 parts; High molecular weight hindered amine light stabilizer: 0.2~0.4 parts; Hindered phenolic primary antioxidant: 0.1~0.2 parts; Phosphite-based auxiliary antioxidants: 0.1~0.2 parts; Lubricating dispersant: 0.5~1.0 parts.

2. The weather-resistant polypropylene composite material according to claim 1, characterized in that, The polypropylene resin is a high-impact copolymer polypropylene, and its melt flow rate at 230℃ and 2.16kg load is 20~30g / 10min.

3. The weather-resistant polypropylene composite material according to claim 1, characterized in that, The metallocene ethylene-octene copolymer has an octene content of 20-40 wt%, a density of 0.86-0.89 g / cm³, and a melt index of 0.5-5 g / 10 min at 190 °C and a load of 2.16 kg.

4. The weather-resistant polypropylene composite material according to claim 1, characterized in that, The rutile nano-titanium dioxide has an average particle size of 30-50 nm, and its surface is coated with an aluminum oxide and / or stearic acid treatment layer.

5. The weather-resistant polypropylene composite material according to claim 1, characterized in that, The low molecular weight hindered amine light stabilizer is bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, and the high molecular weight hindered amine light stabilizer is poly{[6-[(1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-di][(2,2,6,6-tetramethylpiperidinyl)imino]-1,6-hexanediol}.

6. The weather-resistant polypropylene composite material according to claim 1, characterized in that, The benzotriazole UV absorber is 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole.

7. The weather-resistant polypropylene composite material according to claim 1, characterized in that, The composite material also contains a colorant, which is a heavy metal-free organic pigment or masterbatch, and its dosage is 0.5 to 5 parts by weight.

8. The weather-resistant polypropylene composite material according to claim 1, characterized in that, The lubricating dispersant is ethylene bis-stearamide and / or calcium stearate.

9. A method for preparing a weather-resistant polypropylene composite material for toy dragons as described in any one of claims 1-8, characterized in that, Includes the following steps: S1. The rutile nano-titanium dioxide, benzotriazole UV absorber, low molecular weight hindered amine light stabilizer, high molecular weight hindered amine light stabilizer, hindered phenolic primary antioxidant, phosphite auxiliary antioxidant, and metallocene ethylene-octene copolymer accounting for 5% to 30% of the total weight of the metallocene ethylene-octene copolymer are premixed to obtain a composite additive premix. S2. The polypropylene resin, the remaining metallocene ethylene-octene copolymer, the polypropylene grafted maleic anhydride compatibilizer and the lubricating dispersant are added to the main feed port of the twin-screw extruder. The composite additive premix obtained in step S1 and the optional colorant are added to the twin-screw extruder through the side feed port for melt blending extrusion. After cooling and pelletizing, the weather-resistant polypropylene composite material is obtained.

10. The method for preparing the weather-resistant polypropylene composite material for toy dragons according to claim 9, characterized in that, The premixing described in step S1 is carried out in a high-speed mixer at a temperature of 50~70℃ for 3~10 minutes.