Polypropylene resin composition for foam injection molding and foam molded article produced therefrom

Abstract

A polypropylene resin composition for foam injection molding of the present invention comprises: about 100 parts by weight of a base resin comprising about 20 to about 70 wt% of a high-melt-tension polypropylene resin and about 30 to about 80 wt% of a block polypropylene resin; and about 0.1 to about 1.5 parts by weight of a zinc compound. The polypropylene resin composition for foam injection molding exhibits excellent impact resistance, thermal insulation, surface durability, light weight, and a well-balanced combination of these physical properties.

Description

Polypropylene resin composition for foam injection molding and foam molded body produced therefrom

[0001] The present invention relates to a polypropylene resin composition for foam injection molding and a foamed molded article manufactured therefrom. More specifically, the present invention relates to a polypropylene resin composition for foam injection molding having excellent impact resistance, thermal insulation, surface durability, lightweight properties, and a balance of these physical properties, and a foamed molded article manufactured therefrom.

[0002]

[0003] Typically, since thermoplastic resins lack thermal insulation properties, when applying thermoplastic resin compositions to internal components (injection molded parts) of appliances such as refrigerators and air conditioners that require thermodynamic cycles, insulating materials such as expanded polystyrene (EPS) or expanded polypropylene (EPP) are attached. However, using additional insulating materials increases production costs due to extra material costs associated with the processing steps and longer manufacturing times, and recycling is not easy due to the use of different materials.

[0004] Furthermore, although the technology for manufacturing thermal insulation materials by foaming thermoplastic resins such as EPS and EPP using chemical foaming agents is widely used commercially, it faces problems such as low productivity due to the need for compression molding, the limitation to manufacturing only plate-shaped products, and difficulty in applying it to injection molding technology. Moreover, since the internal and surface foam structures are identical and the material has a low specific gravity, surface durability is very poor, making it difficult to apply to various fields and requiring separate surface coatings and protective films.

[0005] Therefore, there is a need to develop polypropylene resin compositions with excellent impact resistance, thermal insulation, surface durability, lightweight properties, and a balance of these physical properties.

[0006] The background technology of the present invention is disclosed in Korean Patent Publication No. 10-2014-0009470, etc.

[0007]

[0008] The objective of the present invention is to provide a polypropylene resin composition for foam injection molding that has excellent impact resistance, thermal insulation, surface durability, lightweight properties, and a balance of these physical properties.

[0009] Another objective of the present invention is to provide a foamed molded article formed from the above-mentioned polypropylene resin composition for foam injection.

[0010] Another objective of the present invention is to provide a method for manufacturing the foamed molded body.

[0011] The above and other objectives of the present invention can all be achieved by the present invention described below.

[0012]

[0013] 1. One aspect of the present invention relates to a polypropylene resin composition for foam injection. The polypropylene resin composition for foam injection comprises about 100 parts by weight of a base resin comprising about 20 to about 70 parts by weight of a high melt strength polypropylene resin and about 30 to about 80 parts by weight of a block polypropylene resin; and about 0.1 to about 1.5 parts by weight of a zinc compound.

[0014] 2. In the above 1 embodiment, the high melt strength polypropylene resin may have a melt strength of about 25 to about 45 cN as measured by Rheotens equipment.

[0015] 3. In the above 1 or 2 embodiments, the high melt strength polypropylene resin may have a melt-flow index of about 0.1 to about 10 g / 10 min, measured at 230°C and a 2.16 kg load according to ASTM D1238.

[0016] 4. In the above 1 to 3 embodiments, the block polypropylene resin may be a block polypropylene resin composed of one or more of a homopolypropylene block, an ethylene-propylene copolymer block, and a homopolyethylene block.

[0017] 5. In the above 1 to 4 embodiments, the block polypropylene resin may have a melt-flow index of about 0.1 to about 5 g / 10 min measured at 230°C and a 2.16 kg load according to ASTM D1238.

[0018] 6. In the above 1 to 5 embodiments, the zinc compound may include one or more of zinc acetylacetonate, zinc acetate, and zinc oxide.

[0019] 7. In the above 1 to 6 embodiments, the weight ratio of the block polypropylene resin and the zinc compound may be about 1:0.002 to about 1:0.04.

[0020] 8. In the above embodiments 1 to 7, the polypropylene resin composition for foam injection molding may have a notched Izod impact strength of about 20 to about 80 kgf·cm / cm of a 1 / 8" thick specimen measured according to ASTM D256.

[0021] 9. In the above 1 to 8 embodiments, the polypropylene resin composition for foam injection molding may have a thermal conductivity of about 0.04 to about 0.06 W / m·K of a foam injection molded specimen measuring 24.6 cm × 24.6 cm × 2 cm as measured according to KS M 3809.

[0022] 10. In the above 1 to 9 embodiments, the polypropylene resin composition for foam injection molding may have a total surface impact energy of about 3 to about 10 J for a foam injection molded specimen of size 10 cm × 10 cm × 2 cm measured under 5 kg, 1 m conditions according to ASTM D1709.

[0023] 11. In the above 1 to 10 embodiments, the polypropylene resin composition for foam injection molding may have a specific gravity of about 0.05 to about 0.5 calculated according to Formula 1 below:

[0024] [Equation 1]

[0025] Specific gravity = Weight of specimen / Weight of specimen submerged in water

[0026] In the above Equation 1, the specimen weight is the weight of a foam injection molded specimen with dimensions of 3 cm × 3 cm × 2 cm, and the submerged specimen weight is the weight measured when the foam injection molded specimen is completely submerged in water.

[0027] 12. Another aspect of the present invention relates to a foamed molded article. The foamed molded article is formed by physically foaming a polypropylene resin composition for foam injection according to any one of 1 to 11 using a core-back method, and is characterized by comprising a first non-foamed surface layer, an internal foamed layer, and a second non-foamed surface layer.

[0028] 13. In the above 12 embodiments, the first surface layer and the second surface layer may each have a thickness of about 0.1 to about 1 mm.

[0029] 14. In the above 12 or 13 embodiments, the internal foam layer may have a thickness of about 5 to about 50 mm.

[0030] 15. Another aspect of the present invention relates to a method for manufacturing a foamed molded article. The manufacturing method comprises the step of: placing a polypropylene resin composition for foam injection according to any one of 1 to 10 into a mold of a physical foam injection machine; and injecting nitrogen as a foaming gas into the mold, and, under conditions of a foaming gas pressure of about 80 to about 240 bar, a cylinder temperature of about 200 to about 230°C, and a mold temperature of about 60 to about 90°C, applying a holding pressure of about 300 bar for about 2 to about 10 seconds, and then proceeding the core back about 5 to about 50 mm.

[0031]

[0032] The present invention has the effect of providing a polypropylene resin composition for foam injection molding with excellent impact resistance, thermal insulation, surface durability, lightness, and balance of physical properties, a foamed molded article produced therefrom, and a method for producing said foamed molded article.

[0033]

[0034] FIG. 1 is a schematic diagram schematically illustrating a cross-section of a foamed molded body according to one embodiment of the present invention.

[0035]

[0036] The present invention will be described in detail below.

[0037] The polypropylene resin composition for foam injection according to the present invention is formed from a thermoplastic resin composition comprising (A) a high melt strength polypropylene resin; (B) a block polypropylene resin; and (C) a zinc compound.

[0038] In this specification, "a to b" indicating a numerical range is defined as "≥a and ≤b".

[0039]

[0040] (A) High melt strength polypropylene resin

[0041] A high melt strength (HMS) polypropylene resin according to one embodiment of the present invention can be applied together with block polypropylene resin and zinc compounds, etc., to improve the impact resistance, thermal insulation, surface durability, lightness, and balance of physical properties of a polypropylene resin composition for foam injection and a foam molded article, and can use a high melt strength polypropylene resin used in a conventional polypropylene resin composition for foam injection.

[0042] In a specific example, the high melt strength polypropylene resin is a polypropylene modified by introducing a long chain branch structure to the polypropylene backbone, and is a polypropylene resin in which the melt strength is increased due to the long chain structure and the tensile strength, flexural strength, and flexural modulus are improved.

[0043] In a specific example, the high melt tension polypropylene resin may have a melt tension of about 25 to about 45 cN, for example, about 30 to about 40 cN, as measured by a Rheotens device (a Rheotens 71.97 device from Geppert, Germany). Within this range, the foaming characteristics and foam cell stability of the polypropylene resin composition for foam injection molding may be excellent. Here, the melt tension can be measured by feeding the resin into a Brabender uniaxial extruder from Brabender, Germany, extruding it at about 200°C and about 50 rpm, and mounting the Rheotens device below the die. The Rheotens device is equipped with four wheels for stretching the resin, and the stretching speed is equal (0.1 s⁻¹). -1 It is uniformly accelerated by ).

[0044] In a specific example, the high melt strength polypropylene resin may have a melt-flow index of about 0.1 to about 10 g / 10 min, for example, about 0.5 to about 5 g / 10 min, measured according to ASTM D1238 under conditions of 230°C and a 2.16 kg load. Within this range, the moldability and foaming characteristics of the polypropylene resin composition for foam injection molding may be excellent.

[0045] In a specific example, the high melt strength polypropylene resin may be included in an amount of about 20 to about 70 weight%, for example, about 25 to about 65 weight%, of a base resin comprising a high melt strength polypropylene resin and a block polypropylene resin, with respect to 100 weight%. If the content of the high melt strength polypropylene resin is less than about 20 weight% of the base resin, there is a risk that the thermal insulation, foaming characteristics, foam cell stability, etc. of the polypropylene resin composition for foam injection and the foam molded article will be reduced, and if it exceeds about 70 weight%, there is a risk that the impact resistance, surface durability, etc. of the polypropylene resin composition for foam injection and the foam molded article will be reduced.

[0046]

[0047] (B) Block polypropylene resin

[0048] A block polypropylene resin according to one embodiment of the present invention can be applied together with a high melt strength polypropylene resin and a zinc compound, etc., to improve the impact resistance, thermal insulation, surface durability, lightness, and balance of physical properties of a polypropylene resin composition for foam injection and a foam molded article, and a block polypropylene resin applied to a conventional thermoplastic resin composition can be used.

[0049] In a specific example, the block polypropylene resin may be a block polypropylene resin composed of a homopolypropylene block, an ethylene-propylene copolymer block and / or a homopolyethylene block.

[0050] In a specific example, the polypropylene resin may have a melt-flow index of about 0.1 to about 5 g / 10 min, for example, about 0.2 to about 3 g / 10 min, measured according to ASTM D1238 under conditions of 230°C and a 2.16 kg load. Within this range, the mechanical strength, moldability, foaming characteristics, etc. of the polypropylene resin composition for foam injection can be excellent.

[0051] In a specific example, the block polypropylene resin may be included in an amount of about 30 to about 80 weight%, for example, about 35 to about 75 weight%, of a base resin comprising a high melt strength polypropylene resin and a block polypropylene resin, with respect to 100 weight%. If the content of the block polypropylene resin is less than about 30 weight% of the base resin, there is a risk that the impact resistance, surface durability, etc. of the polypropylene resin composition for foam injection and the foam molded article will be reduced, and if it exceeds about 80 weight%, there is a risk that the thermal insulation, foaming characteristics, foam cell stability, etc. of the polypropylene resin composition for foam injection and the foam molded article will be reduced.

[0052]

[0053] (C) Zinc compound

[0054] A zinc compound according to one embodiment of the present invention is applied together with high melt strength polypropylene resin and block polypropylene resin, etc., to improve the impact resistance, thermal insulation, surface durability, lightness, and balance of physical properties of a polypropylene resin composition for foam injection and a foam molded article.

[0055] In a specific example, the zinc compound may include one or more of zinc acetylacetonate, zinc acetate, and zinc oxide.

[0056] In a specific example, the zinc compound may be included in an amount of about 0.1 to about 1.5 parts by weight, for example, about 0.2 to about 1.2 parts by weight, specifically about 0.6 to about 1.2 parts by weight, with respect to about 100 parts by weight of the base resin. If the content of the zinc compound is less than about 0.1 parts by weight with respect to about 100 parts by weight of the base resin, there is a risk that the thermal insulation, foaming characteristics, foam cell stability, etc. of the polypropylene resin composition for foam injection and the foam molded article will be reduced, and if it exceeds about 1.5 parts by weight, there is a risk that the surface durability, injection moldability, appearance characteristics, etc. of the polypropylene resin composition for foam injection and the foam molded article will be reduced.

[0057] In a specific example, the weight ratio of the block polypropylene resin and the zinc compound (block polypropylene resin : zinc compound) may be about 1 : 0.002 to about 1 : 0.04, for example, about 1 : 0.002 to about 1 : 0.025. Within this range, the impact resistance, thermal insulation, surface durability, foaming characteristics, etc. of the polypropylene resin composition for foam injection and the foam molded article may be superior.

[0058]

[0059] A polypropylene resin composition for foam injection molding according to one embodiment of the present invention may further include additives used in conventional polypropylene resin compositions to a extent that does not impede the purpose and effects of the present invention. Examples of said additives include, but are not limited to, compatibilizers, antioxidants, impact modifiers, flame retardants, anti-dripping agents, release agents, nucleating agents, UV stabilizers, pigments, dyes, and mixtures thereof.

[0060] In a specific example, the above-mentioned compatibilizer may be a modified polyolefin, but is not limited thereto.

[0061] In a specific example, when using the above additive, the content may be about 0.001 to about 40 parts by weight, for example about 0.1 to about 10 parts by weight, with respect to about 100 parts by weight of the base resin, but is not limited thereto.

[0062]

[0063] A polypropylene resin composition for foam injection according to one embodiment of the present invention may be in the form of pellets produced by mixing the above components and melt-extruding them using a conventional twin-screw extruder at about 180 to about 320°C, for example, about 200 to about 300°C.

[0064] In a specific example, the polypropylene resin composition for foam injection molding may have a notched Izod impact strength of about 20 to about 80 kgf·cm / cm, for example, about 25 to about 70 kgf·cm / cm, of a 1 / 8" thick specimen measured according to ASTM D256.

[0065] In a specific example, the above-described polypropylene resin composition for foam injection molding may have a thermal conductivity of about 0.04 to about 0.06 W / m·K, for example, about 0.045 to about 0.055 W / m·K, of a foam injection molded specimen (foam molded specimen) measuring 24.6 cm × 24.6 cm × 0.2 cm as measured according to KS M 3809.

[0066] In a specific example, the polypropylene resin composition for foam injection molding may have a total face impact energy of about 3 to about 10 J, for example, about 4 to about 9 J, of a foam injection molded specimen measuring 10 cm × 10 cm × 2 cm under conditions of 5 kg, 1 m in accordance with ASTM D1709.

[0067] In a specific example, the polypropylene resin composition for foam injection molding may have a specific gravity calculated according to Formula 1 below of about 0.05 to about 0.5, for example, about 0.08 to about 0.4.

[0068] [Equation 1]

[0069] Specific gravity = Weight of specimen / Weight of specimen submerged in water

[0070] In the above Equation 1, the specimen weight is the weight of a foam injection specimen (foam molded specimen) with dimensions of 3 cm × 3 cm × 2 cm, and the submerged specimen weight is the weight measured when the foam injection specimen is completely submerged in water.

[0071]

[0072] The foamed molded article according to the present invention can be formed by physically foaming the above-described polypropylene resin composition for foam injection using a core-back method, and can be easily manufactured by a person skilled in the art to which the present invention belongs. Since the foamed molded article has excellent impact resistance, thermal insulation, surface durability, lightness, and a balance of these physical properties, it can be used for purposes such as injection-molded parts to prevent condensation in air circulation components of home appliances such as refrigerators and air conditioners, and sound-absorbing and sound-insulating materials to reduce noise in dishwashers.

[0073] FIG. 1 is a schematic diagram illustrating a cross-section of a foamed molded body according to one embodiment of the present invention. In the drawings, the sizes of the components constituting the invention are exaggerated for clarity of the specification and are not limited thereto. In addition, the shape of each component is not limited to the drawings and may have various shapes. As shown in FIG. 1, the foamed molded body (100) formed by physical foaming injection of the polypropylene resin composition for foaming injection using a core-back method is formed of the same material and may include an upper non-foamed first surface layer (112), an internal foamed layer (120) that foams inside, and a lower non-foamed second surface layer (114).

[0074] In a specific example, the first surface layer (112) and the second surface layer (114) are upper and lower surface portions that are not foamed during the core-back type physical foam injection molding, and each may have a thickness of about 0.1 to about 1 mm. Within this range, the surface durability, impact resistance, etc. of the foamed molded body may be excellent.

[0075] In a specific example, the inner foam layer (120) is a part that forms a foam cell by foaming inside (between the first surface layer (112) and the second surface layer (114)) when the polypropylene resin composition for foam injection is physically foamed in a core-back manner. The thickness of the inner foam layer (120) can be adjusted according to the physical foam injection conditions and the core-back conditions, and the thickness of the inner foam layer (120) may be about 5 to about 50 mm. Within this range, the thermal insulation, lightness, sound absorption, etc. of the foamed molded body may be excellent.

[0076] In a specific example, the internal foam layer (120) may have an average size of foam cells ranging from about 20 to about 400 μm. Within this range, the thermal insulation, lightness, sound absorption, etc., of the foam molded body may be excellent. Here, the average size of the foam cells is a value obtained by cutting a cross-section, measuring the cell diameter (size) of the internal foam layer (120) at least 50 times using a Scanning Electron Microscope (SEM), and then calculating the average value.

[0077]

[0078] A foamed molded body according to one embodiment of the present invention can be manufactured by a manufacturing method comprising the step of: placing the polypropylene resin composition for foam injection into the mold of a physical foam injection machine; and injecting nitrogen as a foaming gas into the mold, and, under conditions of a foaming gas pressure of about 80 to about 240 bar, a cylinder temperature of about 200 to about 230°C, and a mold temperature of about 60 to about 90°C, applying a holding pressure of about 300 bar for about 2 to about 10 seconds, and then advancing the core bag by about 5 to about 50 mm.

[0079]

[0080] The present invention is to be explained more specifically through the following examples, but these examples are for illustrative purposes only and should not be interpreted as limiting the invention.

[0081]

[0082] Examples

[0083] The specifications of each component used in the examples and comparative examples below are as follows.

[0084] (A) High melt strength polypropylene resin

[0085] High melt tensile strength polypropylene resin (Manufacturer: Lotte Chemical, Product Name: HMS-130) was used.

[0086] (B) Block polypropylene resin

[0087] Block polypropylene resin (Manufacturer: Lotte Chemical, Product Name: B-310) was used.

[0088] (C) Zinc compound

[0089] (C1) Zinc acetylacetonate (Zn(Acac)2, Manufacturer: Sigma-Aldrich) was used.

[0090] (C2) Zinc acetate (Zn(Ac)2, Manufacturer: Deoksan Science) was used.

[0091]

[0092] Examples 1 to 6 and Comparative Examples 1 to 4

[0093] After adding each of the above components in the amounts listed in Tables 1 and 2 below, a polypropylene resin composition for foam injection molding (in pellet form) was prepared by extruding at approximately 220°C. A single-screw extruder with L / D=40 and a diameter of 39.8 mm (screw rotation speed: 250 rpm, feed speed: 40 kg / hr) was used for extrusion.

[0094] Next, using a Super-Foam foam injection molding machine (manufacturer: Woojin Plaim, 360 tons), the above-mentioned polypropylene resin composition for foam injection was placed into a square mold measuring 24.6 cm × 24.6 cm × 0.23 cm, and a core bag was applied while performing physical foam injection to produce a foamed molded body. Here, nitrogen (N2) was used as the foaming gas for the physical foam injection, and the process was performed under conditions of a foaming gas pressure of approximately 90 bar, a cylinder temperature of approximately 220°C, and a mold temperature of approximately 80°C, and after applying a holding pressure of approximately 300 bar for approximately 2 to 10 seconds, a core bag of 20 mm was performed.

[0095] The physical properties of the manufactured foamed molded articles were evaluated by the following method, and the results are shown in Tables 1 and 2 below.

[0096]

[0097] Methods for measuring physical properties

[0098] (1) Notched Izod impact strength (unit: kgf·cm / cm): The notched Izod impact strength of a 1 / 8" thick specimen was measured according to ASTM D256.

[0099] (2) Thermal conductivity (unit: W / m·K): According to KS M 3809, a foam injection molded specimen measuring 24.6 cm × 24.6 cm × 2 cm was placed in a thermal conductivity analysis device (manufacturer: NETZSCH, device name: HFM 436) and the thermal conductivity was measured.

[0100] (3) Total impact energy (unit: J): According to ASTM D1709, the total impact energy of a foam injection molded specimen measuring 10 cm × 10 cm × 2 cm was measured under conditions of 5 kg and 1 m.

[0101] (4) Specific gravity: The specific gravity of the foam injection molded specimen was calculated according to the following Equation 1.

[0102] [Equation 1]

[0103] Specific gravity = Weight of specimen / Weight of specimen submerged in water

[0104] In the above Equation 1, the specimen weight is the weight of a foam injection molded specimen with dimensions of 3 cm × 3 cm × 2 cm, and the submerged specimen weight is the weight measured when the foam injection molded specimen is completely submerged in water.

[0105]

[0106] Example 1 23456(A) (Weight%) 254565454545(B) (Weight%) 7555355555555(C1) (Parts by weight) 0.20.20.20.61.2-(C2) (Parts by weight) -----0.2 Notch Izod Impact Strength 705025455332 Thermal Conductivity 0.0520.050.0480.050.050.05 Total Impact Energy 8645.86.55.5 Specific Gravity 0.240.20.180.20.20.2

[0107] * Parts by weight: Parts by weight relative to 100 parts by weight of base resin (A+B)

[0108]

[0109] Comparative Example 1234(A) (Weight%) 15754545(B) (Weight%) 85255555(C1) (Parts by weight) 0.75 0.75 0.012(C2) (Parts by weight) ---- Notched Izod Impact Strength 80 155545 Thermal Conductivity 0.07 0.04 8 0.06 5 0.05 Total Impact Energy 15282.5 Specific Gravity 0.3 20.18 0.2 20.2

[0110] * Parts by weight: Parts by weight relative to 100 parts by weight of base resin (A+B)

[0111]

[0112] From the above results, it can be seen that the polypropylene resin composition for foam injection molding of the present invention has excellent impact resistance (notched Izod impact strength), thermal insulation (thermal conductivity), surface durability (total surface impact energy), and balance of these physical properties, and has excellent lightness (specific gravity).

[0113] On the other hand, in Comparative Example 1, in which high melt strength polypropylene resin is used in an amount less than the content range of the present invention and block polypropylene resin is used in an amount greater than the content range of the present invention, it was found that thermal insulation properties, etc. were reduced and foaming rates were reduced. In Comparative Example 2, in which high melt strength polypropylene resin is used in an amount greater than the content range of the present invention and block polypropylene resin is used in an amount less than the content range of the present invention, it was found that impact resistance, surface durability, etc. were reduced. Additionally, in Comparative Example 3, in which zinc compound is used in an amount less than the content range of the present invention, it was found that thermal insulation properties, etc. were reduced and foaming rates were reduced. In Comparative Example 4, in which zinc compound is used in an amount greater than the content range of the present invention, it was found that surface durability, etc. were reduced.

[0114]

[0115] The present invention has been described above with reference to embodiments. Those skilled in the art will understand that the present invention may be embodied in modified forms without departing from the essential characteristics of the invention. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the invention is defined by the claims, not by the foregoing description, and all variations within the scope of equivalents should be interpreted as being included in the invention.

Claims

1. About 100 parts by weight of a base resin comprising about 20 to about 70 weight% of a high melt tension polypropylene resin and about 30 to about 80 weight% of a block polypropylene resin; and A polypropylene resin composition for foam injection molding characterized by comprising about 0.1 to about 1.5 parts by weight of a zinc compound.

2. A polypropylene resin composition for foam injection molding according to claim 1, characterized in that the high melt tension polypropylene resin has a melt tension of about 25 to about 45 cN as measured by a réthense device.

3. A polypropylene resin composition for foam injection molding according to claim 1 or 2, characterized in that the high melt strength polypropylene resin has a melt-flow index of about 0.1 to about 10 g / 10 min measured at 230°C and a 2.16 kg load condition in accordance with ASTM D1238.

4. A polypropylene resin composition for foam injection molding, characterized in that, in any one of claims 1 to 3, the block polypropylene resin is a block polypropylene resin composed of one or more of a homopolypropylene block, an ethylene-propylene copolymer block, and a homopolyethylene block.

5. A polypropylene resin composition for foam injection molding, characterized in that, in any one of claims 1 to 4, the block polypropylene resin has a melt-flow index of about 0.1 to about 5.0 g / 10 min as measured under conditions of 230°C and a 2.16 kg load in accordance with ASTM D1238.

6. A polypropylene resin composition for foam injection molding, characterized in that, in any one of claims 1 to 5, the zinc compound comprises one or more of zinc acetylacetonate, zinc acetate, and zinc oxide.

7. A polypropylene resin composition for foam injection molding, characterized in that, in any one of claims 1 to 6, the weight ratio of the block polypropylene resin and the zinc compound is about 1:0.002 to about 1:0.

04.

8. A polypropylene resin composition for foam injection molding according to any one of claims 1 to 7, characterized in that the polypropylene resin composition for foam injection molding has a notched Izod impact strength of about 20 to about 80 kgf·cm / cm of a 1 / 8" thickness specimen measured according to ASTM D256.

9. A polypropylene resin composition for foam injection molding according to any one of claims 1 to 8, characterized in that the thermal conductivity of a foam injection molding specimen measuring 24.6 cm × 24.6 cm × 2 cm, measured in accordance with KS M 3809, is about 0.04 to about 0.06 W / m·K.

10. A polypropylene resin composition for foam injection molding according to any one of claims 1 to 9, characterized in that the total surface impact energy of a foam injection molding specimen measuring 10 cm × 10 cm × 2 cm is about 3 to about 10 J, measured under conditions of 5 kg and 1 m in accordance with ASTM D1709.

11. A polypropylene resin composition for foam injection molding according to any one of claims 1 to 10, characterized in that the specific gravity of the polypropylene resin composition for foam injection molding is about 0.05 to about 0.5 as calculated according to Formula 1 below: [Equation 1] Specific gravity = Weight of specimen / Weight of specimen submerged in water In the above Equation 1, the specimen weight is the weight of a foam injection molded specimen with dimensions of 3 cm × 3 cm × 2 cm, and the submerged specimen weight is the weight measured when the foam injection molded specimen is completely submerged in water.

12. A polypropylene resin composition for foam injection according to any one of claims 1 to 11 is formed by physical foam injection using a core-back method, and A foamed molded body characterized by comprising a first non-foamed surface layer, an internal foamed layer, and a second non-foamed surface layer.

13. A foamed molded article according to claim 12, wherein the first surface layer and the second surface layer each have a thickness of about 0.1 to about 1 mm.

14. A foamed molded article according to claim 12 or 13, characterized in that the internal foam layer has a thickness of about 5 to about 50 mm.

15. A polypropylene resin composition for foam injection according to any one of claims 1 to 11 is placed into a mold of a physical foam injection machine; and A method for manufacturing a foamed molded article, characterized by comprising the step of injecting nitrogen as a foaming gas into the mold, applying a holding pressure of about 300 bar for about 2 to about 10 seconds under conditions of a foaming gas pressure of about 80 to about 240 bar, a cylinder temperature of about 200 to about 230°C, and a mold temperature of about 60 to about 90°C, and then injecting while advancing the core bag by about 5 to about 50 mm.

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