Polypropylene resin composition for uncoated crash pad

Abstract

Disclosed is a polypropylene resin composition for an uncoated crash pad. The composition may include an amount of about 50 to 80 wt % of a polypropylene resin having a Polydispersity Index (PI) of about 4.5 to 6.5, a weight average molecular weight of about 200,000 to 350,000 g/mol, and an isotactic peptide fraction of about 96% or greater as measured by a C.sup.13-NMR method, an amount of about 1 to 30 wt % of rubber having a melt index of about 1 to 6 g/10 min (230° C., 2.16 Kg), an amount of about 11 to 30 wt % of an inorganic filler composed of a mixture of an amount of about 10 to 20 wt % of talc and an amount of about 1 to 10 wt % of whisker, and an amount of about 1 to 5 wt % of an anti-scratch agent, all the wt % are based on the total weight of the polypropylene resin composition.

Claims

1. A polypropylene resin composition for an uncoated crash pad, comprising: an amount of 50 to 80 wt % of a polypropylene resin having a Polydispersity Index (PI) of 4.5 to 6.5, a weight average molecular weight of 200,000 to 350,000 g/mol, and an isotactic peptide fraction of 96% or greater as measured by a C.sup.13-NMR method; an amount of 1 to 30 wt % of a rubber component having a melt index of 1 to 6 g/10 min (230° C., 2.16 Kg); an amount of 11 to 30 wt % of an inorganic filler comprising a mixture of an amount of 10 to 20 wt % of talc and an amount of 1 to 10 wt % of whisker; and an amount of 1 to 5 wt % of an anti-scratch agent, all the wt % based on the total weight of the polypropylene resin composition, wherein the polypropylene resin is a mixture of homopolypropylene and block copolypropylene, wherein the block copolypropylene has a molecular weight distribution (MWD) of 7 to 12, a melt index of 20 to 100 g/10 min (230° C., 2.16 Kg), and a weight average molecular weight of 200,000 to 350,000 g/mol, and wherein the block copolypropylene is a mixture of (i) block copolypropylene having a melt index of 20 to 40 g/10 min (230° C., 2.16 Kg) and a weight average molecular weight of 200,000 to 350,000 g/mol and (ii) block copolypropylene having a melt index of 60 to 100 g/10 min (230° C., 2.16 Kg) and a weight average molecular weight of 200,000 to 250,000 g/mol, wherein the rubber component comprises ethylene-octene (EO)-based rubber and styrene-ethylene-butadiene-styrene (SEBS)-based rubber which are mixed at a weight ratio of 1:1.

2. The polypropylene resin composition of claim 1, wherein the homopolypropylene has a molecular weight distribution (MWD) of 6 to 8, a melt index of 10 to 30 g/10 min (230° C., 2.16 Kg), and a weight average molecular weight of 200000 to 250000 g/mol.

3. The polypropylene resin composition of claim 1, wherein the talc has an average particle diameter of 0.1 to 1 μm.

4. The polypropylene resin composition of claim 1, wherein the whisker has an aspect ratio of 10 to 50 and an acicular shape.

5. The polypropylene resin composition of claim 1, wherein the polypropylene resin composition has a melt index of 25 to 43 g/10 min (230° C., 2.16 Kg), a flexural modulus of 1500 to 2300 MPa, and an Izod impact strength of 450 to 510 J/m.

6. The polypropylene resin composition of claim 1, consisting essentially of an amount of 50 to 80 wt % of a polypropylene resin having a Polydispersity Index (PI) of 4.5 to 6.5, a weight average molecular weight of 200,000 to 350,000 g/mol, and an isotactic peptide fraction of 96% or greater as measured by a C.sup.13-NMR method; an amount of 1 to 30 wt % of rubber having a melt index of 1 to 6 g/10 min (230° C., 2.16 Kg); an amount of 11 to 30 wt % of an inorganic filler including a mixture of an amount of 10 to 20 wt % of talc and an amount of 1 to 10 wt % of whisker; and 1 to 5 wt % of an anti-scratch agent, all the wt % of the components are based on the total weight of the polypropylene resin.

7. The polypropylene resin composition of claim 1, consisting of an amount of 50 to 80 wt % of a polypropylene resin having a Polydispersity Index (PI) of 4.5 to 6.5, a weight average molecular weight of 200,000 to 350,000 g/mol, and an isotactic peptide fraction of 96% or greater as measured by a C.sup.13-NMR method; an amount of 1 to 30 wt % of rubber having a melt index of 1 to 6 g/10 min (230° C., 2.16 Kg); an amount of 11 to 30 wt % of an inorganic filler including a mixture of an amount of 10 to 20 wt % of talc and an amount of 1 to 10 wt % of whisker; and 1 to 5 wt % of an anti-scratch agent all the wt % of the components are based on the total weight of the polypropylene resin.

8. A molded article comprising the polypropylene resin composition of claim 1.

9. A vehicle comprising the molded article of claim 8.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a photograph showing an exemplary surface appearance of a test specimen using an exemplary polypropylene resin composition of Example 1 according to an exemplary embodiment of the present invention; and

(2) FIG. 2 is a photograph showing the surface appearance of a test specimen using a polypropylene resin composition of Comparative Example 4 according to the present invention.

(3) Notably, the white reflections shown in the photographs of FIGS. 1 and 2 are not part of the present invention.

DETAILED DESCRIPTION

(4) As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprise”, “include”, “have”, etc. when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements and/or components but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or combinations thereof.

(5) It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g. fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles.

(6) Further, unless specifically stated or obvious from context, as used herein, the term “about” is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from the context, all numerical values provided herein are modified by the term “about.”

(7) Hereinafter, a detailed description will be given of an embodiment of the present invention.

(8) According to the present invention, a polypropylene resin composition for an uncoated crash pad may include an amount of about 50 to 80 wt % of a polypropylene resin having a PI (Polydispersity Index) of about 4.5 to 6.5, a weight average molecular weight of about 200000 to 350000 g/mol, and an isotactic peptide fraction of about 96% or greater as measured by a C.sup.13-NMR method; an amount of about 1 to 30 wt % of rubber having a melt index of an amount of about 1 to 6 g/10 min (230° C., 2.16 Kg); an amount of about 11 to 30 wt % of an inorganic filler including a mixture of an amount of about 10 to 20 wt % of talc and an amount of about 1 to 10 wt % of whisker; and an amount of about 1 to 5 wt % of an anti-scratch agent, all the wt % are based on the total weight of the polypropylene composition.

(9) In a preferred embodiment of the present invention, the polypropylene resin may include a highly crystalline polypropylene resin having a high isotactic index, crystallinity increasing with an increase in the isotactic index. Preferably, a resin having a high isotactic peptide fraction of about 96% or greater as measured by a C.sup.13-NMR method is used. Furthermore, the highly crystalline polypropylene resin has a PI (Polydispersity Index) of about 4.5 to 6.5. When the PI is less than about 4.5, a poor appearance, such as flow marks, may result. On the other hand, when the PI is greater than about 6.5, properties such as rigidity may deteriorate. The highly crystalline polypropylene resin preferably has a weight average molecular weight of about 200000 to 350000 g/mol.

(10) The highly crystalline polypropylene resin may include a mixture of homopolypropylene and block copolypropylene. For example, the homopolypropylene may have a wide molecular weight distribution (MWD) of about 6 to 8, a weight average molecular weight of about 200000 to 250000 g/mol, and/or a melt index of about 10 to 30 g/10 min (230° C., 2.16 Kg), thus enhancing rigidity. When the molecular weight distribution of the homopolypropylene is less than about 6, injection moldability may become poor. On the other hand, when the molecular weight distribution thereof is greater than about 8, rigidity may become poor. Also, when the melt index is less than about 10 g/10 min, flowability may decrease. On the other hand, when the melt index is greater than about 30 g/10 min, elasticity may decrease. Preferably, the melt index falls in the range of about 15 to 25 g/10 min (230° C., 2.16 Kg).

(11) Here, the molecular weight distribution (MWD) may be a value obtained by dividing a weight average molecular weight (Mw) by a number average molecular weight (Mn), and such a molecular weight distribution is significantly associated with processing moldability and properties. As the molecular weight distribution (MWD) is decreased, rigidity and impact resistance may be efficiently balanced, but injection moldability may decrease. On the other hand, when the molecular weight distribution (MWD) increases, injection moldability may become good but rigidity may decrease.

(12) The block copolypropylene may be a block copolypropylene obtained by copolymerizing about 85 to 90 wt % of homopolypropylene and about 10 to 15 wt % of ethylene-propylene. As such, the amount of ethylene may be in an amount of about 3 to 8 wt % based on the total amount of block copolypropylene. The block copolypropylene may have a wide molecular weight distribution (MWD) of about 7 to 12, a melt index of about 20 to 100 g/10 min (230° C., 2.16 Kg), and/or a weight average molecular weight of about 200000 to 350000 g/mol. When the molecular weight distribution of the block copolypropylene is less than about 7, impact resistance is improved but processability is deteriorated. On the other hand, when the molecular weight distribution thereof is greater than about 12, flowability may be improved but rigidity may become poor.

(13) In order to reduce flow marks that are easily observed in medium- to large-sized parts, two block copolypropylene resins having different wide molecular weight distributions and melt indexes may be mixed to thus improve an appearance. For example, a mixture of (i) block copolypropylene having a melt index of 20 to 40 g/10 min (230° C., 2.16 Kg) and a weight average molecular weight of 200000 to 350000 g/mol and (ii) block copolypropylene having a melt index of 60 to 100 g/10 min (230° C., 2.16 Kg) and a weight average molecular weight of 200000 to 250000 g/mol may be preferably used.

(14) When the melt index of the (i) block copolypropylene having a molecular weight distribution (MWD) of 7 or greater is less than about 20 g/10 min, fluidity may decrease. On the other hand, when the melt index thereof is greater than about 40 g/10 min, impact performance may decrease. Preferably the melt index may be in the range of about 25 to 35 g/10 min (230° C., 2.16 Kg).

(15) Also, when the melt index of the (ii) block copolypropylene is less than about 60 g/10 min, injection moldability may decrease. On the other hand, when the melt index thereof is greater than about 100 g/10 min, fluidity may increase but impact resistance may decrease. Preferably the melt index thereof may be in the range of about 70 to 90 g/10 min (230° C., 2.16 Kg).

(16) Preferably, the highly crystalline polypropylene resin may be prepared by mixing homopolypropylene, block copolypropylene having a melt index of about 20 to 40 g/10 min (230° C., 2.16 Kg), and block copolypropylene having a melt index of about 60 to 100 g/10 min (230° C., 2.16 Kg) at a weight ratio of about 1:1:3 to 6, or particularly, at a weight ratio of about 1:1:3.6 to 5.7.

(17) In a preferred embodiment of the present invention, in order to improve impact resistance at a low temperature (−30° C.), the rubber may be used in the form of a mixture of ethylene-octene-based rubber and styrene-ethylene-butadiene-styrene-based rubber. Preferably, ethylene-octene (EO) rubber and styrene-ethylene-butadiene-styrene (SEBS) rubber may be mixed at a weight ratio of about 1:1.

(18) When the above two rubber components are mixed, flexibility suitable for use in an uncoated crash pad may be obtained, and impact strength, such as low-temperature impact performance, may also be improved. The rubber is used in an amount of about 1 to 30 wt %. When the amount thereof is less than about 1 wt %, low-temperature impact performance may become insignificant and defects such as burrs may be generated on the surface of parts. On the other hand, if the amount thereof is greater than about 30 wt %, rigidity and heat resistance may decrease due to the use of an excess of rubber, and flow marks may be generated on the surface of parts.

(19) In a preferred embodiment of the present invention, in order to improve the rigidity of the polypropylene resin composition, the inorganic filler may be used in the form of a mixture of talc having an average particle diameter of about 0.1 to 1 μm and acicular whisker having an aspect ratio of about 10 to 50. The amount of the inorganic filler may be about 11 to 30 wt %. When the amount thereof is less than about 11 wt %, a flexural modulus may decrease. On the other hand, when the amount thereof is greater than about 30 wt %, impact resistance may decrease.

(20) Preferably, talc having an average particle diameter as small as about 0.1 to 1 μm may be suitably used in order to increase both rigidity and impact performance. When the average particle diameter of the talc is less than about 0.1 μm, dispersion may not be performed upon extrusion processing. On the other hand, when the average particle diameter thereof is greater than about 1 μm, rigidity and impact performance may decrease. Furthermore, when the amount of the talc is included in an amount less than about 10 wt %, rigidity may decrease. On the other hand, when the amount thereof is included in an amount of greater than about 20 wt %, impact strength may decrease and scratch resistance may become poor. Preferably, talc having an average particle diameter of about 0.3 to 0.7 μm may be used.

(21) In a preferred embodiment of the present invention, the whisker has an aspect ratio of about 10 to 50 and an acicular shape. When the aspect ratio of the whisker is less than about 10, the improvement in rigidity may become insignificant. On the other hand, when the aspect ratio thereof is greater than about 50, anisotropy may increase and thus post-deformation such as distortion may occur. In order to balance rigidity and dimensional stability, whisker having an aspect ratio of about 20 to 40 is preferably used. Furthermore, when the amount of the whisker is included in an amount less than about 1 wt %, rigidity may remarkably decrease. On the other hand, when the amount thereof is included in an amount greater than about 10 wt %, sufficient scratch resistance required of parts may not be obtained.

(22) In a preferred embodiment of the present invention, in order to improve scratch resistance of the uncoated crash pad, the anti-scratch agent may be used in the form of a mixture of synthetic silicone and modified polyethylene wax. The modified polyethylene wax may suitably include polyethylene wax (polyethylene-wax-graft-maleic anhydride) to which maleic anhydride may be grafted. Although a conventional anti-scratch agent is silicone M/B, in which siloxane and polyolefin are synthesized, the anti-scratch agent used in the present invention may result from simultaneous mixing of synthetic silicone and modified polyethylene wax, rather than direct synthesis of siloxane and polyolefin, thereby further improving scratch resistance.

(23) When the two components are mixed in this way, surface migration may be minimized, thus improving the appearance of the part and also maximizing scratch resistance thereof.

(24) The amount of the anti-scratch agent may suitably be about 1 to 5 wt %. When the amount thereof is less than about 1 wt %, the effect of scratch resistance may be insignificant. On the other hand, when the amount thereof is greater than about 5 wt %, a flexural modulus may decrease and thus flow marks may be generated on the surface of the part, undesirably deteriorating the aesthetic appearance.

(25) In a preferred embodiment of the present invention, the polypropylene resin composition may have a melt index of about 25 to 43 g/10 min (230° C., 2.16 Kg), a flexural modulus of about 1500 to 2300 MPa, and/or an Izod impact strength of about 450 to 510 J/m.

(26) The polypropylene resin composition according to the present invention includes, as the highly crystalline polypropylene resin, a mixture of polypropylene resins having different melt indexes and molecular weight distributions, and as the rubber, a mixture of ethylene-octene-based rubber and SEBS-based rubber, thus maximizing resin flowability to thereby effectively reduce appearance problems, such as flow marks, weld lines, and the like, ultimately exhibiting a good surface appearance. The inorganic filler comprising a mixture of talc and whisker and the anti-scratch agent comprising a mixture of synthetic silicone and modified polyethylene wax may be mixed at an appropriate ratio, thereby simultaneously improving the rigidity and impact performance of parts and the scratch resistance thereof.

(27) Moreover, the density of the polypropylene resin composition according to the exemplary embodiment of the present invention may be decreased by about 3 to 4% from about 1.04 g/cm.sup.3 to about 1.00 g/cm.sup.3 or less, whereby release from a mold may become easy. Also, the coating process may be omitted to thus realize simple processing, thereby reducing processing costs and also preventing indoor air pollution from occurring during the coating process.

EXAMPLE

(28) A better understanding of the present invention will be given of the following examples, which are not to be construed as limiting the present invention.

Examples 1 to 4 and Comparative Examples 1 to 13

(29) Respective polypropylene resin compositions were prepared through a typical process using components in the amounts shown in the following Table 5. Next, respective compositions were melt-kneaded using a twin-screw extruder and thus made into pellets, after which test specimens were manufactured using an injection molding machine.

(30) The components and properties of the materials used in the tests are shown in the following Tables 1 to 4.

(31) (1) Polypropylene

(32) TABLE-US-00001 TABLE 1 Weight Molecular Melt index average weight [g/10 min] molecular distri- Isotactic (230° C., PI* weight bution peptide Sample No. 2.16 Kg) (230° C.) [g/mol] (MWD) fraction ** PP homo-1 20 5.9 220000 7 96 to 97 PP block-1 30 4.8 300000 9.9 96 to 97 PP block-2 80 — 230000 8.7 96 to 97 PP block-3 30 4.4 250000 9.3 96 to 97 PP block-4 80 — 130000 5.3 96 to 97 *PI (Polydispersity Index) is variable, and is an index for molecular weight distribution as the cross over point of G′(loss modulus) and G″(Storage modulus) **Isotactic peptide fraction was measured by C.sup.13-NMR. *** PP homo-1: homopolypropylene *** PP block-1, 2, 3, 4: block copolypropylene resulting from copolymerizing 88 wt % of homopolypropylene and 12 wt % of ethylene-propylene

(33) (2) Rubber

(34) TABLE-US-00002 TABLE 2 Melt index [g/10 min] Density Sample No. (230° C., 2.16 Kg) [Kgf/cm.sup.3] Remark Rubber-1 2 0.86 Ethylene-octene rubber, (Xylene soluble intrinsic viscosity 1.2 to 1.5 dL/g) Rubber-2 4.5 0.89 SEBS (Styrene- ethylene-butylene- styrene copolymer elastomer) Rubber-3 10 0.87 Ethylene-octene rubber (Xylene soluble intrinsic viscosity 0.9 to 1.1 dL/g)

(35) (3) Inorganic Filler

(36) TABLE-US-00003 TABLE 3 Sample No. Type of sample Diameter [μm] Filler-1 Talc D50: 0.5 (average particle diameter) Density 2.7 g/ Filler-2 Whisker Av. Length: 15 μm, Av. Dia.: 0.5 μm Aspect Ratio: 30

(37) (4) Anti-Scratch Agent

(38) TABLE-US-00004 TABLE 4 Sample No. Type of sample Spec. Anti-scratch-1 Synthetic silicone + Synthetic silicone + modified polyethylene wax Polyethylene wax-graft- maleic anhydride Anti-scratch-2 Synthetic silica powder MI: 10 (230° C., 2.16 Kg)

(39) TABLE-US-00005 TABLE 5 Example Comparative Example No. 1 2 3 4 1 2 3 4 5 6 7 8 9 10 11 12 13 PP Homo-1 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 PP 10 10 10 10 — 10 — — 10 10 10 10 10 10 10 10 10 Block-1 PP 40 45 55 35 55 45 45 — 45 64.1 30 46 34 47.5 37 46.1 41.9 Block-2 PP — — — — — — 10 10 — — — — — — — — — Block-3 PP — — — — — — — 45 — — — — — — — — — Block-4 Rubber-1 10 10 5 15 10 10 10 10 10 0.5 18 10 10 10 10 10 10 Rubber-2 10 10 5 15 10 10 10 10 — 0.4 17 10 10 10 10 10 10 Rubber-3 — — — — — — — — 10 — — — — — — — — Filler-1 14 10 10 10 10 10 10 10 10 10 10 0 21 10 10 10 10 Filler-2 3 3 3 3 3 3 3 3 3 3 3 3 3 0.5 11 3 3 Anti- 3 2 2 2 2 — 2 2 2 2 2 2 2 2 2 0.9 5.1 scratch-1 Anti- — — — — — 2 — — — — — — — — — — — scratch-2

Test Example

(40) The test specimens of Examples 1 to 4 and Comparative Examples 1 to 13 were evaluated through the following methods.

(41) (1) Melt index (MI): Measurement was performed in accordance with ASTM D1238 under a load of 2.16 kg at 230° C. (polypropylene) and 190° C. (polyethylene).

(42) (2) Flexural modulus: Measurement was performed in accordance with ASTM D790 at room temperature, with a test specimen size of 127×12.7×6.4 mm, at a testing rate of 30 mm/min.

(43) (3) Izod impact strength: A test specimen having a size of 63.5×12.7×6.4 mm and being notched was used.

(44) (4) Scratch resistance: A 20×20 lattice pattern was scratched at 2 mm apart using an Ericsson tester, and the L value was measured before and after the evaluation of scratching (L value after scratching−initial L value), to thus calculate ΔL.

(45) (5) Part surface appearance: Whether a flow mark was generated on the surface of the part was observed with the naked eye and evaluated. (∘: good, Δ: fair (generation of some flow mark), X: poor (generation of full flow mark))

(46) TABLE-US-00006 TABLE 6 Example Comparative Example No. 1 2 3 4 1 2 3 4 5 Melt index 32 33 43 25 35 31 32 32 34 [g/10 min] (230° C., 2.16 kg) Density 1.01 0.99 0.99 0.99 1.01 1.01 1.01 1.01 1.01 [g/cm.sup.3] Flexural 2000 1900 2300 1810 2010 1980 2000 1900 1980 modulus [Mpa] Izod impact 470 480 450 490 468 470 465 465 460 strength (23° C.) [J/m] Scratch 0.3 0.2 0.2 0.2 0.4 1.5 0.5 0.5 0.5 resistance (ΔL) Part surface ◯ ◯ ◯ ◯ Δ Δ Δ X X appearance Comparative Example No. 6 7 8 9 10 11 12 13 Melt index 58 23 34 29 35 31 34 33 [g/10 min] (230° C., 2.16 kg) Density 0.99 0.99 0.98 1.07 0.97 1.05 0.99 0.99 [g/cm.sup.3] Flexural 2900 1600 1960 2400 1790 2600 1910 1810 modulus [Mpa] Izod impact 65 590 475 440 485 350 480 485 strength (23° C.) [J/m] Scratch 0.3 0.6 0.2 1.5 0.2 1.9 2.4 0.1 resistance (ΔL) Part surface Δ X Δ ◯ ◯ ◯ ◯ X appearance

(47) As is apparent from the results of Table 6, in Examples 1 to 4, flexural modulus, impact strength, scratch resistance, and part surface appearance were efficiently balanced, and satisfied all of the numerical values of properties required of uncoated crash pads. FIG. 1 shows the surface appearance of a test specimen using an exemplary polypropylene resin composition of Example 1. As shown in FIG. 1, neither flow marks nor burrs were apparently generated on the surface of the test specimen.

(48) However, in Comparative Example 1, homopolypropylene and only one kind of block copolypropylene having a wide molecular weight distribution and high melt index were used, and thus flow marks were generated on portions of the surface of the part.

(49) In Comparative Example 2, scratch performance was deteriorated due to the use of synthetic silica powder as the anti-scratch agent, and furthermore, part surface appearance was poor.

(50) In Comparative Examples 3 and 4, using the mixture of block copolypropylenes having different weight average molecular weights or molecular weight distributions, flow marks were generated on portions of the surface of the part in Comparative Example 3, and were severely generated on the entire surface of the part in Comparative Example 4. FIG. 2 shows the surface appearance of a test specimen using the polypropylene resin composition of Comparative Example 4. As shown in FIG. 2, flow marks were generated on the surface of the test specimen, resulting in a poor appearance.

(51) In Comparative Example 5, flow marks were generated on the surface of the part due to the use of ethylene-octene-based rubber having a high melt index (MI) and low intrinsic viscosity (IV) as the rubber component. In Comparative Example 6, when the amount of rubber was less than 1 wt %, impact performance deteriorated and burrs were generated on the surface of the part. As in Comparative Example 7, when the amount of rubber was greater than 35 wt %, a melt index (MI) was drastically decreased and thus flow marks were generated on the surface of the part and rigidity was lowered.

(52) In Comparative Example 8, when the amount of talc was less than 10 wt %, defects were generated on the surface of the part and rigidity was lowered. In Comparative Example 9, when the amount of talc was greater than 20 wt %, impact strength was decreased and thus scratch performance was not satisfied, and moreover, density was increased.

(53) In Comparative Example 10, when a small amount of whisker was included, product rigidity was lowered. In Comparative Example 11, when the amount of whisker was greater than 10 wt %, scratch resistance was not satisfied.

(54) In Comparative Example 12, when the amount of the anti-scratch agent was less than 1 wt %, scratch resistance was lowered. In Comparative Example 13, when the amount of the anti-scratch agent was greater than 5 wt %, stains were generated on the surface of the part.

(55) Although the various exemplary embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.