Non-paint metallic polypropylene resin composition with improved flow mark and molded article thereof

Abstract

The present disclosure relates to a paintless metallic polypropylene resin composition with improved flow marks and a molded article thereof. The paintless metallic polypropylene resin composition of the present disclosure minimizes shear stress generated by voids and possesses high viscoelasticity, thereby inducing smooth flow of recycled material and preventing the occurrence of flow marks in the molded article. Furthermore, workability and aesthetics may be excellent when using the paintless metallic polypropylene resin composition of the present disclosure for double injection molding.

Description

Technology Field

[0001] The present disclosure relates to a paintless metallic polypropylene resin composition with improved flow marks and a molded article thereof. Background Technology

[0002] As demands for manufacturing cost reduction and environmental protection intensify, the automotive industry is focusing on increasing production efficiency and introducing eco-friendly manufacturing processes. In particular, the development of paintless exterior parts, which eliminate the painting process, is garnering attention as a key technology to meet these demands. Paintless products offer excellent appearance quality without the need for a separate painting process, while possessing the advantages of cost reduction and minimized environmental impact.

[0003] Polypropylene (PP) is widely used not only in automotive interior and exterior materials but also in the electrical and electronic fields due to its low cost, lightweight properties, and excellent durability and mechanical strength. However, unpainted products made with polypropylene resin require addressing surface defects that occur during injection molding. These defects, known as flow marks or tiger marks, appear on the surface of injection-molded parts as periodic stripes that intersect the flow direction. They are caused by fluctuations in resin flow within the mold and solidification phenomena at the flow ends. Flow marks degrade the appearance quality of the molded product, resulting in a product that is unsuitable for use as high-end exterior parts.

[0004] Recently, the use of recycled materials has been increasing for the purpose of environmental protection. Compared to new materials, recycled materials have weaker mechanical properties and generate relatively more volatile organic compounds (VOCs). These VOCs, such as formaldehyde, acetaldehyde, benzene, toluene, xylene, ethylbenzene, and styrene, can pose a potential threat to user health and can be the source of odors that cause discomfort to users, making it difficult to apply recycled materials directly to vehicles.

[0005] To overcome the disadvantages of such recycled materials, a dual injection molding process is being researched in which recycled material is used for the inner layer and new material for the surface layer. Conventional research on dual injection molding processes has focused on dual injection molding equipment and its control technology. Therefore, there is a need for research and development on resin compositions suitable for the surface layer that facilitate injection and ensure excellent appearance quality of the molded product. The problem to be solved

[0006] The present disclosure aims to solve conventional problems by providing a paint-free metallic polypropylene resin composition and a molded article thereof that can smoothly fill a cavity during double injection and prevent the occurrence of flow marks on a molded article.

[0007] In addition, the present disclosure aims to provide a paintless metallic polypropylene resin composition and a molded article thereof that can be applied in green technology fields, such as the manufacture of automotive interior and exterior materials containing recycled materials. means of solving the problem

[0008] To achieve the above objective, the present disclosure provides a polypropylene resin composition comprising 30 to 80 weight% of a polypropylene-based resin; 5 to 30 weight% of an ethylene-α-olefin copolymer; 1 to 5 weight% of a scratch-resistant additive; 5 to 35 weight% of an inorganic filler; and 0.1 to 0.5 weight% of a processing aid.

[0009] The polypropylene-based resin according to one example of the present disclosure may be a polypropylene homopolymer, an ethylene-propylene block copolymer, or a mixture thereof.

[0010] The polypropylene-based resin according to one example of the present disclosure may have a melt index (MI) of 40 to 120 g / 10 min (230°C, 2.16 kg).

[0011] The ethylene-α-olefin copolymer according to one example of the present disclosure may be a copolymer of at least one α-olefin among ethylene and α-olefins having 3 to 10 carbon atoms.

[0012] The α-olefin according to one example of the present disclosure may comprise one or more selected from the group consisting of propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, and 1-octene.

[0013] The ethylene-α-olefin copolymer according to one example of the present disclosure may have a melt index (MI) of 0.1 to 20 g / 10 min (230°C, 2.16 kg).

[0014] The ethylene-α-olefin copolymer according to one example of the present disclosure may have a Mooney viscosity of 10 to 50 and a degree of crystallinity of 1 to 20.

[0015] The scratch-resistant additive according to one example of the present disclosure may be a siloxane masterbatch.

[0016] The inorganic filler according to one example of the present disclosure may include one or more selected from the group consisting of talc, calcium carbonate, clay, whiskers, kaolin, barium sulfate, olastonite, mica, clay, magnesium hydroxide, titanium oxide, carbon black, glass bubbles, and glass fibers.

[0017] The polypropylene resin composition according to one example of the present disclosure may further include one or more functional additives selected from the group consisting of antioxidants, ultraviolet absorbers, nucleating agents, coupling agents, dispersants, lubricants, slip agents, flame retardants, effect pigments, organic or inorganic pigments, heat stabilizers, weather stabilizers, and antistatic agents.

[0018] The antioxidant according to one example of the present disclosure may include one or more selected from the group consisting of phenolic antioxidants and phosphorus-based antioxidants.

[0019] The polypropylene resin composition according to one example of the present disclosure may comprise 0.1 to 0.5 weight% of the phenolic acid inhibitor, 0.1 to 0.5 weight% of the phosphorus-based antioxidant, 0.1 to 0.5 weight% of the lubricant, 0.5 to 5 weight% of the effect pigment, and 0.1 to 3 weight% of the organic-inorganic pigment.

[0020] In another aspect of the present disclosure, a molded article is provided that is obtained by double injection molding the polypropylene resin composition and the recycled resin composition. Effects of the invention

[0021] The paintless metallic polypropylene resin composition of the present disclosure minimizes shear stress generated by voids and has high viscoelasticity, which can induce smooth flow of recycled material.

[0022] The paintless metallic polypropylene resin composition of the present disclosure can prevent flow marks from occurring in molded articles.

[0023] In addition, the paintless metallic polypropylene resin composition of the present disclosure may have excellent workability and aesthetics. Specific details for implementing the invention

[0024] The present disclosure is described in more detail below. However, the following examples are merely for reference to explain the present disclosure in detail and are not limited thereto, and the present disclosure may be implemented in various forms.

[0025] Additionally, unless otherwise defined, all technical and scientific terms have the same meaning as generally understood by one of the art to which this disclosure pertains.

[0026] The terms used in the description herein are merely for the purpose of effectively describing specific embodiments and are not intended to limit the disclosure.

[0027] Additionally, the singular form used in the specification and the appended claims may be intended to include the plural form unless specifically indicated otherwise in the context.

[0028] Additionally, units used herein without special mention are based on weight, for example, units of % or ratio mean weight % or weight ratio, and weight % means the weight percentage of any one component of the total composition that occupies the composition, unless otherwise defined.

[0029] Furthermore, when it is stated that a part "includes" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0030] Additionally, numerical ranges used in this specification may include lower and upper limits and all values ​​within the range, increments logically derived from the form and width of the defined range, all of which are limited values, and all possible combinations of upper and lower limits of numerical ranges defined in different forms. Unless otherwise specifically defined in this disclosure, values ​​outside the numerical range that may occur due to experimental error or rounding of values ​​are also included in the defined numerical range.

[0031] In this specification, “mooney viscosity” means the Mooney viscosity (ML1+4@121℃) measured according to ASTM-D1646 at 121℃.

[0032] Hereinafter, the compositional components constituting the polypropylene resin composition according to one embodiment of the present disclosure will be described in more detail.

[0033] (a) Polypropylene resin

[0034] A polypropylene resin composition according to one embodiment of the present disclosure comprises a polypropylene-based resin as a base resin. The polypropylene-based resin may be a polypropylene homopolymer, an ethylene-propylene block copolymer, a propylene-1-butene block copolymer, a propylene-1-hexene block copolymer, or a mixture thereof, and specifically may be a polypropylene homopolymer, an ethylene-propylene block copolymer, or a mixture thereof.

[0035] In a specific embodiment, the polypropylene-based resin may be an ethylene-propylene block copolymer, wherein the polypropylene-based resin is preferably a copolymer polymerized with 70 to 99 weight% of propylene monomer and 1 to 30 weight% of ethylene monomer, more specifically 95 to 99 weight% of propylene monomer and 1 to 5 weight% of ethylene monomer. This is because if the content of ethylene monomer as a monomer constituting the polypropylene-based resin is less than 1 weight%, usability decreases due to reduced impact resistance, and if it exceeds 30 weight%, the rigidity of the molded article may decrease, which is undesirable.

[0036] The above polypropylene-based resin may be used having a melt index (MI) of 40 to 120 g / 10 min (230°C, 2.16 kg), specifically 70 to 110 g / 10 min (230°C, 2.16 kg). If the melt index (MI) of the above polypropylene-based resin is less than 40 g / 10 min (230°C, 2.16 kg), moldability may be reduced due to reduced flowability, and if it exceeds 120 g / 10 min (230°C, 2.16 kg), impact strength may be reduced, which is undesirable.

[0037] The density of the above polypropylene-based resin may be 0.850 to 0.950 g / cm³, specifically 0.900 to 0.920 g / cm³, but is not limited thereto.

[0038] The above polypropylene-based resin may have a heat distortion temperature of 120°C or higher and 125°C or higher as a lower limit, and 200°C or lower, 180°C or lower, and 160°C or lower as an upper limit, but is not limited thereto as long as the purpose of the present disclosure can be achieved.

[0039] The above polypropylene-based resin may be included in an amount of 30 to 80 weight% or 40 to 65 weight% based on 100 weight% of the total resin composition. If the content of the above polypropylene-based resin is less than 30 weight%, the rigidity of the resin composition is reduced and the heat resistance is lowered, which makes it difficult to fully perform the function of the molded article. If the content of the above polypropylene-based resin exceeds 80 weight%, the impact resistance may be reduced, which is undesirable.

[0040] (b) Ethylene-α-olefin copolymer

[0041] A polypropylene resin composition according to one embodiment of the present disclosure may include an ethylene-α-olefin copolymer as an elastic material to impart elasticity and flexibility and reinforce impact resistance.

[0042] The above ethylene-α-olefin copolymer may be a copolymer of ethylene and at least one α-olefin among α-olefins having 3 to 10 carbon atoms. Specifically, it may be an olefin copolymer formed by copolymerizing ethylene and one or more α-olefin monomers selected from the group consisting of propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, and 1-octene, a terpolymer, an olefin block copolymer formed by block copolymerizing α-olefin monomers, or a graft copolymer in which one type of α-olefin monomer has a skeletal chain structure of the copolymer and another type of α-olefin monomer is bonded in a branched form. In this case, the ethylene-α-olefin copolymer may have a chemical structure in which carbon atoms with 4, 6, 8, etc. are extended in the side chain of the polyolefin structure.

[0043] The content of the above ethylene-α-olefin copolymer may be included in an amount of 5 to 30 weight% based on 100 weight% of the total resin composition. If the content of the above ethylene-α-olefin copolymer is less than 5 weight%, the impact properties may be reduced, and if it exceeds 30 weight%, the stiffness may be reduced and the ductility may be strengthened, which is undesirable as it may reduce mechanical properties such as flexural modulus.

[0044] At this time, the melt index (MI) of the ethylene-α-olefin copolymer may be 0.1 to 20 g / 10 min (190°C, 2.16 kg), specifically 0.5 to 15 g / 10 min (190°C, 2.16 kg), more specifically 1 to 10 g / 10 min (190°C, 2.16 kg), and is not limited thereto as long as the purpose of the present disclosure can be achieved.

[0045] The Mooney viscosity of the above ethylene-α-olefin copolymer may be 10 to 100, specifically 15 to 80, and more specifically 20 to 50. If this is satisfied, flow marks can be minimized.

[0046] The density of the above ethylene-α-olefin copolymer may be 0.800 to 0.900 g / cm³, specifically 0.855 to 0.890 g / cm³, but is not limited thereto.

[0047] The ethylene-α-olefin copolymer according to one embodiment of the present disclosure may include a first ethylene-α-olefin copolymer and a second ethylene-α-olefin copolymer. By controlling the content of the different ethylene-α-olefin copolymers, flow marks may not occur during molding, thereby providing a molded article with excellent appearance quality.

[0048] According to one embodiment of the present disclosure, the Mooney viscosity of the first ethylene-α-olefin copolymer may be smaller than the Mooney viscosity of the second ethylene-α-olefin copolymer. Specifically, the ratio (M2 / M1) of the Mooney viscosity (M1) of the first ethylene-α-olefin copolymer and the Mooney viscosity (M2) of the second ethylene-α-olefin copolymer may be 2 to 10, specifically 3 to 5. When the above range is satisfied, the length of the flow mark may be minimized.

[0049] (c) Scratch-resistant additive

[0050] A polypropylene resin composition according to one embodiment of the present disclosure may include a scratch-resistant additive to improve the quality of a molded article by imparting scratch-resistant performance. The scratch-resistant additive may be a siloxane masterbatch, but is not limited thereto. The siloxane masterbatch may be a polypropylene-siloxane masterbatch composed of 50% by weight of polypropylene and 50% by weight of ultra-high molecular weight (UHMW) siloxane resin.

[0051] Siloxane masterbatches have the effect of further improving surface functions, such as enhancing slip properties and improving resistance to scratches and defects. In addition, they prevent the leakage of fluids and other additives that may occur when using silicone materials.

[0052] The above-mentioned scratch-resistant additive may be included in a content range of 1 to 5 weight%, specifically 2 to 3 weight%, based on 100 weight% of the total resin composition. If the content of the above-mentioned scratch-resistant additive is less than 1 weight%, the effect of improving scratch resistance performance is insufficient, and if it exceeds 5 weight%, it is difficult to further improve scratch resistance performance, and instead, a problem of increased costs due to excessive input may occur.

[0053] (d) Inorganic filler

[0054] A polypropylene resin composition according to one embodiment of the present disclosure may include an inorganic filler to improve the structural strength of a molded article. The inorganic filler may include one or more selected from the group consisting of talc, calcium carbonate, clay, whiskers, kaolin, barium sulfate, olastonite, mica, clay, magnesium hydroxide, titanium oxide, carbon black, glass bubbles, and glass fibers. Specifically, the inorganic filler may include talc, which is particularly suitable as an inorganic filler of the present disclosure because it has an excellent effect of reinforcing physical properties such as flexibility, stiffness, and low-temperature impact resistance in the resin composition. It is preferable that the average particle size of the talc be 7 μm or less, as the effect of reinforcing stiffness decreases as the average particle size exceeds 7 μm, and if it exceeds 7 μm excessively, the shape of the filler may be observed on the appearance of the molded article, which becomes a problem. However, if talc with an excessively small particle size is used, there are difficulties in process and content control, so it is suitable for the average particle size of the talc to be 3.0 to 7.0 μm.

[0055] The content of the above-mentioned inorganic filler may be included in an amount of 5 to 35 weight% based on 100 weight% of the total resin composition. If the content of the above-mentioned inorganic filler is less than 5 weight%, the stiffness reinforcement effect is low and it is difficult to improve the shrinkage rate, and if it exceeds 35 weight%, there is a problem in that it is difficult to obtain a weight reduction effect due to the high specific gravity.

[0056] (e) Processing aid

[0057] A polypropylene resin composition according to one embodiment of the present disclosure may include a processing aid to increase the flow index of the resin composition. The processing aid may be one or more selected from the group consisting of a carboxylic acid derivative-based processing aid and a dendrimer.

[0058] The content of the above processing aid may be included in an amount of 0.1 to 0.5 weight%, specifically 0.2 to 0.4 weight%, based on 100 weight% of the total resin composition. When the above range is satisfied, the flow index of the resin composition can be efficiently increased.

[0059] (f) Functional additives

[0060] A polypropylene resin composition according to one embodiment of the present disclosure may additionally include functional additives commonly used in the art. For example, the functional additives may include one or more selected from the group consisting of antioxidants, ultraviolet absorbers, nucleating agents, coupling agents, dispersants, lubricants, slip agents, flame retardants, effect pigments, organic or inorganic pigments, heat stabilizers, weather stabilizers, and antistatic agents.

[0061] The above antioxidant may include one or more selected from the group consisting of phenolic antioxidants and phosphorus-based antioxidants.

[0062] The above-mentioned dispersant or lubricant may provide the effect of reducing the dispersibility of inorganic fillers such as pigments and talc and shear stress during processing, and the above-mentioned antioxidant may include one selected from the group consisting of phenolic antioxidants, phosphite-based antioxidants, thiodipropionate, and combinations thereof, for preventing a decrease in the molecular weight of polyolefins that decompose due to shear stress, etc.

[0063] The above-mentioned ultraviolet absorber is included in the polypropylene resin composition and has the property of blocking or absorbing ultraviolet rays that decompose polymer chains, thereby preventing changes in the physical properties and appearance of the polymer, such as aging, and may be one selected from the group consisting of hydroxyl benzophenone, benzotriazoles, and combinations thereof.

[0064] The above effect pigment may include one or more selected from the group consisting of aluminum, brass, and mica that exhibit a metallic texture.

[0065] The above organic or inorganic pigments may include organic pigments including phthalocyanine-based pigments having lightfastness and / or inorganic pigments including titanium dioxide, carbon black, and pigment masterbatch.

[0066] A polypropylene resin composition according to one embodiment of the present disclosure may comprise, based on 100 weight% of the total resin composition, 0.1 to 0.5 weight% of the phenolic acid inhibitor, 0.1 to 0.5 weight% of the phosphorus-based antioxidant, 0.1 to 0.5 weight% of the lubricant, 0.5 to 5 weight% of the effect pigment, and 0.1 to 3 weight% of the organic or inorganic pigment, but is not limited thereto.

[0067] Next, a molded article according to another embodiment of the present disclosure will be described. Another embodiment of the present disclosure may provide a molded article obtained by double injection molding a polypropylene resin composition and a recycled resin composition according to one embodiment of the present disclosure described above. Specifically, the molded article may include a surface layer formed of the polypropylene resin composition and an inner layer formed of the recycled resin composition. The molded article may be an unpainted molded article that does not require separate painting.

[0068] The melt index (MI) of the recycled resin composition according to one embodiment of the present disclosure may be 10 to 35 g / 10 min (190°C, 2.16 kg), specifically 20 to 30 g / 10 min (190°C, 2.16 kg), and is not limited thereto as long as the purpose of the present disclosure can be achieved.

[0069] According to one embodiment of the present disclosure, the melt index of the polypropylene resin composition may be greater than the melt index of the recycled resin composition. When this is satisfied, flow marks are minimized, and the phenomenon in which the polypropylene resin composition is consumed before the recycled resin composition or mixed by jetting at the end of the mold can be prevented.

[0070] The specific gravity of the above recycled resin composition measured according to ISO 1183 may be 1.00 to 1.10, specifically 1.03 to 1.05, and is not limited thereto as long as the purpose of the present disclosure can be achieved.

[0071] The above recycled resin composition may have a recycled End-of-Life Vehicle (ELV) content of 50% by weight or more, 60% by weight or more, or 70% by weight or more based on the total weight of the recycled resin composition.

[0072] Preferred embodiments and comparative examples of the present disclosure are described below. However, the following examples are merely preferred embodiments of the present disclosure, and the present disclosure is not limited to the following examples.

[0074] Examples 1, 2 and Comparative Examples 1 to 3

[0075] The components listed in Table 1 below were fed into a mixer in the amounts specified and mixed, and then the mixture was fed into an extruder and melt-kneaded to prepare a resin composition.

[0076] Examples Comparative example 1 2 1 2 3 Ethylene-propylene block copolymer 50 50 50 50 70 1st ethylene-α-olefin copolymer - 10 15 20 10　 Second ethylene-α-olefin copolymer 20 10 5 - 10 Polypropylene-silicon masterbatch 3 3 3 3 3 Weapon filler 30 30 30 30　 10　 Processing preparation 0.4 0.4 - - - functional additives Phenol-based acid repellents 0.1 0.1 0.1 0.1 0.1 Ingye Sanbangje 0.1 0.1 0.1 0.1 0.1 lubricant 0.2 0.2 0.2 0.2 0.2 Gloss pigment 3 3 3 3 3 pigment 0.5 0.5 0.5 0.5 0.5

[0078] The compositional components of the items listed in Table 1 above and the characteristics of each component are shown below.

[0079] <Composition>

[0080] (1) Polypropylene resin

[0081] An ethylene-propylene block copolymer with a melt index of 110 g / 10 min (230℃, 2.16 kg), a density of 0.91 g / cm³, a heat distortion temperature of 125℃, and an ethylene content of 3.0~5.0 wt% was used.

[0082] (2) Ethylene-α-olefin copolymer

[0083] The first ethylene-α-olefin copolymer had a density of 0.875 g / cm³, a melt index of 3 g / 10 min (190°C, 2.16 kg), and a Mooney viscosity of 11, and the second ethylene-α-olefin copolymer had a density of 0.860 g / cm³, a melt index of 0.3 g / 10 min (190°C, 2.16 kg), and a Mooney viscosity of 47.

[0084] (3) Scratch-resistant additive

[0085] A masterbatch composed of 50 wt% polypropylene and 50 wt% ultra-high molecular weight (UHMW) siloxane resin was used.

[0086] (4) Inorganic filler

[0087] Talc with an average particle size range of 3.0 to 7.0 µm was used.

[0088] (5) Functional additives

[0089] The components and characteristics of the above-mentioned functional additive are described below.

[0090] 1) Lubricant: Ethylene bis Stearamid was used as a stearcene-based compound. The lubricant has the function of reducing shear stress generated during the preparation of the composition. In addition to ethylene bis Stearamid, Magnesium Stearate and Calcium Sterate may be used.

[0091] 2) Antioxidant: Basf’s Irganox 1010 was used as a phenolic antioxidant, and Basf’s Irgafos 168 was used as a phosphorus-based antioxidant. It has the function of preventing quality degradation caused by oxidation and thermal decomposition during manufacturing or use.

[0092] 3) Effect pigment: As an aluminum-based effect pigment, an aluminum pigment with an average particle size of 5 to 95 μm containing 20 to 30 weight percent of PP or Wax as a carrier was used, and it has optical properties such as reflectivity, visual refractive power, and light interference, which can produce a metallic luster.

[0093] 4) Organic / Inorganic Pigments: Titanium dioxide was used to achieve a white (bright) color, and High Black Carbon was used to achieve a black (dark) color.

[0094] (6) Processing aid

[0095] The processing aid used was BYK's MAX P product.

[0096] <Physical Property Evaluation>

[0097] The results of measuring physical properties of the resin compositions of the above examples and comparative examples, and specimens produced by injection molding the resin compositions using an injection molding machine and leaving them at room temperature, are shown in Table 2 below. The measurement method for each measurement item is as follows.

[0098] In addition, the results of measuring the physical properties of the recycled resin composition and the specimen prepared from the recycled resin composition in the same way as above are shown in Table 3 below.

[0099] (1) Flow Mark: A specimen was injected in a 1.5T combustible mold with a thin cavity thickness to check for the presence of non-uniform shapes around the weld line and on the outer edge of the specimen under a light source.

[0100] (2) Melt index: Measured at 230°C and 2.16 kg according to ISO 1133.

[0101] (3) Specific gravity: Measured according to ISO 1183.

[0102] (4) Tensile yield strength: Measured according to ISO 527.

[0103] (5) Flexural modulus: Measured according to ISO 178.

[0104] (6) IZOD impact strength: Measured at room temperature according to ISO 180.

[0105] (7) Heat deflection temperature: The heat deflection temperature (HDT) was measured according to the method specified in ISO 75.

[0106] (8) Shrinkage rate: Using ASTM tensile specimens, the difference between the initial length and the length after shrinkage was measured after 24 hours or more following injection, and measured in units of 1 / 1000.

[0107] (9) Die Swell Ratio: Evaluated by an accredited institution.

[0108] Examples Comparative example 1 2 1 2 3 Melt index (g / 10min) 230℃, 2.16kgf 47 52 55 58 49 specific gravity 1.1 1.1 1.1 1.1 0.97 Tensile yield strength (Mpa) 17.7 18 18.7 19 17.5 Flexural modulus (Mpa) 1,900 1,950 2,005 2,100 1,420 Izod impact strength (kJ / m²) 2 ) 37 35 33 29 40 Heat distortion temperature 0.45 Mpa (°C) 105 107 108 110 88 Shrinkage rate (1 / 1000) 6.6 6.8 6.9 7.1 9.5 Die Swell Ratio(240℃) 1.8 1.6 1.5 1.4 1.6

[0109] Recycled resin composition Melt index (g / 10min) 230℃, 2.16kgf 24 specific gravity 1.05 Tensile yield strength (Mpa) 23 Flexural modulus (Mpa) 2,200 Izod impact strength (kJ / m²) 2 ) 5.5 Heat distortion temperature 0.45 Mpa (°C) 117 Shrinkage rate (1 / 1000) 12

[0110] Referring to Tables 2 and 3 above, the resin composition according to the embodiment of the present disclosure had a lower shrinkage rate compared to the recycled resin composition. In addition, it was confirmed that the low melt index minimizes shear stress generated in the mold cavity, and the high viscoelasticity due to the large Die Swell Ratio allows for immediate diffusion and contact with the mold cavity during double injection. Meanwhile, Comparative Example 3 had a low content of inorganic additives and did not add processing aids, resulting in a relatively higher shrinkage rate and a lower melt index compared to Example 2. Therefore, it was confirmed that the polypropylene resin composition of the present disclosure is suitable for the surface layer of double injection because it facilitates flow when recycled material is used in the inner layer, thereby preventing the occurrence of flow marks on the molded product.

[0112] The features, structures, effects, etc. described in the above-described embodiments are included in at least one embodiment of the present disclosure and are not necessarily limited to only one embodiment. Furthermore, the features, structures, effects, etc. exemplified in each embodiment may be combined or modified and implemented in other embodiments by a person skilled in the art to which the embodiments belong. Accordingly, details regarding such combinations and modifications should be interpreted as being included within the scope of the present disclosure.

Claims

Claim 1 A polypropylene resin composition comprising 30 to 80 weight% of a polypropylene-based resin; 5 to 30 weight% of an ethylene-α-olefin copolymer; 1 to 5 weight% of a scratch-resistant additive; 5 to 35 weight% of an inorganic filler; and 0.1 to 0.5 weight% of a processing aid. Claim 2 A polypropylene resin composition according to claim 1, wherein the polypropylene-based resin is a polypropylene homopolymer, an ethylene-propylene block copolymer, or a mixture thereof. Claim 3 In claim 1, the polypropylene resin composition is a polypropylene resin having a melt index (MI) of 40 to 120 g / 10 min (230°C, 2.16 kg). Claim 4 A polypropylene resin composition according to claim 1, wherein the ethylene-α-olefin copolymer is a copolymer of at least one α-olefin selected from ethylene and α-olefins having 3 to 10 carbon atoms. Claim 5 A polypropylene resin composition according to claim 4, wherein the α-olefin comprises one or more selected from the group consisting of propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, and 1-octene. Claim 6 In claim 1, the ethylene-α-olefin copolymer is a polypropylene resin composition having a melt index (MI) of 0.1 to 20 g / 10 min (230°C, 2.16 kg). Claim 7 In claim 1, the ethylene-α-olefin copolymer is a polypropylene resin composition having a Mooney viscosity of 10 to 50 and a degree of crystallinity of 1 to 20. Claim 8 In claim 1, the above-mentioned scratch-resistant additive is a siloxane masterbatch, a polypropylene resin composition. Claim 9 A polypropylene resin composition according to claim 1, wherein the inorganic filler comprises one or more selected from the group consisting of talc, calcium carbonate, clay, whiskers, kaolin, barium sulfate, olastonite, mica, clay, magnesium hydroxide, titanium oxide, carbon black, glass bubbles, and glass fibers. Claim 10 A polypropylene resin composition according to claim 1, further comprising one or more functional additives selected from the group consisting of antioxidants, ultraviolet absorbers, nucleating agents, coupling agents, dispersants, lubricants, slip agents, flame retardants, effect pigments, organic or inorganic pigments, heat stabilizers, weather stabilizers, and antistatic agents. Claim 11 A polypropylene resin composition according to claim 10, wherein the antioxidant comprises one or more selected from the group consisting of phenolic antioxidants and phosphorus-based antioxidants. Claim 12 A polypropylene resin composition according to claim 11, comprising 0.1 to 0.5 weight% of the phenolic acid inhibitor, 0.1 to 0.5 weight% of the phosphorus-based antioxidant, 0.1 to 0.5 weight% of the lubricant, 0.5 to 5 weight% of the effect pigment, and 0.1 to 3 weight% of the organic-inorganic pigment. Claim 13 A molded article obtained by double injection molding the polypropylene resin composition and the recycled resin composition of claim 1.

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