JP2011126940A - White polypropylene resin composition and automobile exterior part obtained using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a white polypropylene resin composition that is excellent in a balance among properties as well as in heat discoloration resistance and stain resistance and has a good injection molding property, and an automobile exterior part using the same. <P>SOLUTION: The white polypropylene resin composition comprises the following components (a) to (g). Component (a): 50-65 wt.% of a crystalline propylene block copolymer satisfying a specific requirement. Component (b): 10-30 wt.% of an ethylene/α-olefin copolymer elastomer having an MFR of 0.2-10 g/10 min and a density of 0.860-0.870 g/cm<SP>3</SP>. Component (c): 5-20 wt.% of talc. Component (d): 1-2 wt.% of an ethylene/ethyl acrylate copolymer having an ethyl acrylate constituting unit content of 10-20 wt.%. Component (e): 0.02-0.1 wt.% of a sulfur-based antioxidant. Component (f): 1-3 wt.% of a titanium oxide particle having a particle size of 0.05-2 μm. Component (g): 0.2-1.0 wt.% of polyethylene having a density of at least 0.94 g/cm<SP>3</SP>. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a white polypropylene resin composition and an automobile exterior part using the same, and more specifically, a white polypropylene resin composition having excellent physical property balance, heat discoloration resistance and stain resistance, and good injection molding processability. And an automobile exterior part using the same.

Conventionally, exterior members for automobiles have been painted because they are used outdoors. The painting process requires a lot of equipment and the cost of the paint, so it is important to develop an original material that will not be painted. However, since the coating is not performed, the material itself is required to have surface characteristics equal to or higher than those of the coated product, and it is necessary to have excellent stain resistance and heat discoloration resistance.
For example, Patent Document 1 discloses a resin composition for injection-molded bodies comprising a propylene polymer having specific properties and titanium oxide. Since such a composition contains titanium oxide when used as a raw material, it is said that the composition is excellent in warp characteristics, plasticization characteristics, and weather resistance.

  Patent Documents 2 to 4 disclose polypropylene resin compositions containing an ethylene-acrylic acid copolymer. Such a composition is effective for improving the paintability due to the polar group of the ethylene-acrylic acid copolymer, and does not take into consideration the surface characteristics as the original parts.

Further, Patent Documents 5 to 6 disclose a polypropylene resin composition containing an ethylene / ethyl acrylate copolymer, and Patent Document 7 discloses a polypropylene resin composition containing an ethylene / vinyl acetate copolymer. Has been. Such materials are considered to be used as original parts and are said to have improved dirt resistance.
However, the polypropylene resin compositions proposed in Patent Documents 5 to 7 are generally inferior in heat discoloration, and discoloration tends to be noticeable in white parts colored with a white pigment such as titanium oxide. For example, when a vehicle in which the original part is incorporated into the body as an exterior part (bumper, etc.) is stored in an environment at room temperature or higher, the degree of discoloration of the original part is large, resulting in a difference in color between the original part and the body. There's a problem.

  Under such circumstances, a white polypropylene resin composition that eliminates the problems of the prior art and is suitable as a material for automobile exterior parts, has excellent physical property balance, heat discoloration resistance, stain resistance, and good injection molding processability. There is a need to develop things.

Japanese Patent Laid-Open No. 11-80455 JP-A-5-43722 JP-A-6-122775 Japanese Patent Laid-Open No. 9-3270 JP 2006-321907 A JP 2006-321914 A JP 2007-45897 A

  In view of the above-mentioned problems of the prior art, the object of the present invention is a white polypropylene resin that is suitable as a material for automobile exterior parts and has excellent physical property balance, heat discoloration resistance and stain resistance, and good injection molding processability. The object is to provide a composition and an automobile exterior part using the composition.

  In order to solve the above-mentioned problems, the present inventors have made various studies, and as a result, specific crystalline propylene-based block copolymers, ethylene / α-olefin copolymer elastomers having specific properties, specific By combining ethylene / ethyl acrylate copolymer (EEA), polyethylene having a specific density, sulfur-based antioxidant, talc, and titanium oxide particles, stain resistance and heat discoloration resistance compared to conventional materials The inventors have found that a white propylene-based resin composition exhibiting performance with an excellent balance can be obtained, and have completed the present invention.

That is, according to the first invention of the present invention, a white polypropylene resin composition comprising the following components (a) to (g) is provided.
Component (a): Crystalline propylene-based block copolymer satisfying the following requirements (i) to (iv): 50 to 65% by weight
(I) MFR is 20 to 120 g / 10 min. (Ii) MFR of crystalline homopolypropylene part is 50 to 300 g / 10 min. (Iii) Ratio of ethylene-α-olefin copolymer part is 5 to 30 wt. % (Iv) The ethylene content of the ethylene-α-olefin copolymer part is 30 to 55% by weight. Component (b): MFR is 0.2 to 10 g / 10 min, and the density is 0.860 to 0.870 g. / Cm ³ ethylene / α-olefin copolymer elastomer 10 to 30% by weight
Ingredient (c): Talc 5-20% by weight
Component (d): Ethylene acrylate copolymer having an ethyl acrylate structural unit ratio of 10 to 20% by weight 1-2% by weight
Ingredient (e): Sulfur-based antioxidant 0.02 to 0.1% by weight
Component (f): Titanium oxide particles having a particle size of 0.05-2 μm 1-3 wt%
Component (g): Polyethylene having a density of 0.94 g / cm ³ or more 0.2 to 1.0% by weight

  Moreover, according to 2nd invention of this invention, the exterior member for motor vehicles characterized by shape | molding using the white polypropylene resin composition which concerns on 1st invention is provided.

  According to a third aspect of the present invention, there is provided an automotive exterior member according to the second aspect, wherein the automotive exterior component is a bumper.

  The white polypropylene resin composition of the present invention is excellent in balance of physical properties, heat discoloration resistance and stain resistance, and has good injection molding processability, and is a resin composition suitable as an automotive exterior member. Target value is extremely high.

The polypropylene resin composition of the present invention includes (a) a crystalline propylene block copolymer, (b) an ethylene / α-olefin copolymer elastomer, (c) talc, (d) an ethylene / ethyl acrylate copolymer. (E) a sulfur-based antioxidant, (f) titanium oxide particles, and (g) polyethylene.
Below, the component of a polypropylene resin composition, the preparation method of a polypropylene resin composition, a shaping | molding method, a use, etc. are demonstrated in detail.

[I] Component of polypropylene resin composition (1) Crystalline propylene block copolymer (a)
The crystalline propylene block copolymer (hereinafter sometimes abbreviated as component (a)) used in the polypropylene resin composition of the present invention is obtained by sequentially polymerizing a crystalline homopolypropylene portion and an ethylene / propylene copolymer portion. A propylene / ethylene block copolymer obtained by satisfying the following characteristics (i) to (iv).

(I) MFR
The melt flow rate (MFR) of the entire crystalline propylene-based block copolymer (a) is 20 to 120 g / 10 minutes, preferably 25 to 100 g / 10 minutes, more preferably 30 to 80 g / 10 minutes. It is. When the MFR is less than 20 g / 10 minutes, the moldability is inferior, and when it exceeds 120 g / 10 minutes, the impact strength and the tensile elongation are lowered. Here, MFR is a value measured at 230 ° C. under a 2.16 kg load in accordance with JIS K7210.

(Ii) Homopolypropylene part The MFR of the homopolypropylene part of the crystalline propylene-based block copolymer (a) is 50 to 300 g / 10 minutes, preferably 60 to 200 g / 10 minutes. If the MFR is less than 50 g / 10 minutes, the moldability is inferior, and if it exceeds 300 g / 10 minutes, the impact strength and tensile elongation are lowered.

(Iii) Ratio of ethylene / propylene copolymer part The ratio of the ethylene / propylene copolymer part of the crystalline propylene block copolymer (a) is based on the sum of the crystalline homopolypropylene part and the ethylene / propylene copolymer part. 5 to 30% by weight, preferably 10 to 25% by weight. When the ratio of the ethylene / propylene copolymer part is less than 5% by weight, the impact strength is lowered, and when it exceeds 30% by weight, the rigidity is lowered.

(Iv) Ethylene content of ethylene / propylene copolymer part The ethylene content of the ethylene / propylene copolymer part of the crystalline propylene-based block copolymer (a) is 30 to 55% by weight, preferably 35 to 50% by weight. It is. When the ethylene content is less than 30% by weight, the impact strength is lowered, and when it exceeds 55% by weight, the impact strength is lowered.

  The crystalline propylene-based block copolymer (a) used in the present invention is preferably produced by slurry polymerization, bulk polymerization, or gas phase polymerization using a highly stereoregular catalyst. Examples of the highly stereoregular catalyst include a catalyst in which an organic aluminum compound is combined with a solid component formed by bringing magnesium chloride into contact with titanium tetrachloride, an organic hydride, and an organic silane compound. As the polymerization method, either batch polymerization or continuous polymerization can be employed.

  In the polypropylene resin composition of the present invention, the compounding amount of the crystalline propylene block copolymer (a) is 50 to 65% by weight, preferably 55 to 60% by weight. When the blending amount of component (a) is less than 50% by weight, the rigidity is insufficient, and when it exceeds 65% by weight, the balance between impact strength and rigidity is deteriorated.

(2) Ethylene / α-olefin copolymer elastomer (b)
The ethylene / α-olefin copolymer elastomer (hereinafter sometimes abbreviated as component (b)) used in the polypropylene resin composition of the present invention improves impact resistance and has good moldability, Used for the purpose of developing physical properties and shrinkage characteristics. In the ethylene / α-olefin copolymer elastomer, the α-olefin copolymerized with ethylene is not particularly limited, but preferably includes 1-octene and 1-butene. The ethylene / α-olefin copolymer elastomer need not be one kind, and may be a mixture of two or more kinds.

  The ethylene / α-olefin copolymer elastomer has an MFR measured at 230 ° C. of 0.2 to 10 g /, preferably 0.4 to 6 g /. When the MFR deviates from the above range, the appearance becomes poor or the impact property becomes insufficient.

The ethylene / α-olefin copolymer elastomer has a density of 0.860 to 0.870 g / cm ³ , preferably 0.860 to 0.868 g / cm ³ . Density is less than 0.860 g / cm ³ has insufficient stain resistance of the propylene resin composition, the impact resistance is insufficient if the density exceeds 0.870 g / cm ^3. The density is measured according to JIS K7112.

  In the polypropylene resin composition of the present invention, the blending amount of the ethylene / α-olefin copolymer elastomer (b) is 10 to 30% by weight, preferably 15 to 25% by weight. When the amount of component (b) is 10% by weight or less, the impact strength is insufficient, and when it exceeds 30% by weight, the rigidity is inferior and unsuitable.

(3) Talc (c)
Talc used in the polypropylene resin composition of the present invention (hereinafter sometimes abbreviated as component (c)) is used for the purpose of improving rigidity, adjusting dimensional stability, and the like.
Although talc (c) is not specifically limited, Preferably it is 1.5-15 micrometers. The talc is first manufactured by, for example, pulverizing raw talc with an impact pulverizer or micron mill type pulverizer, or further pulverizing with a jet mill or the like and then adjusting the classification with a cyclone or micron separator. To do.
In addition, talc may be surface-treated with various metal soaps, paraffin wax, polyethylene wax or their modified products, organic silane, organic borane, organic titanate, etc., and the apparent specific volume is 2.50 ml / g or less. You may use what is called compression talc. The average particle size of the talc is a value measured using a laser diffraction / scattering particle size distribution meter, and as a measuring device, for example, Horiba LA-920 type is preferable because of its excellent measurement accuracy.

  In the polypropylene resin composition of the present invention, the amount of talc (c) is 5 to 20% by weight, preferably 8 to 15% by weight. When the amount of component (c) is 5% by weight or less, rigidity and heat resistance are insufficient, and when it exceeds 20% by weight, impact strength and appearance are inferior and unsuitable.

(4) Ethylene / ethyl acrylate copolymer (EEA) (d)
The ethylene / ethyl acrylate copolymer (EEA) (hereinafter sometimes abbreviated as component (d)) used in the polypropylene resin composition of the present invention has an ethyl acrylate structural unit ratio of 10 to 20% by weight. Yes, preferably 13 to 18% by weight. When the ratio of the ethyl acrylate structural unit is lower than 10% by weight, the compatibility between EEA and other components becomes high, and the migration of EEA to the component surface is small, resulting in insufficient stain resistance. When the content is larger than 20% by weight, the compatibility is poor and the physical properties are greatly adversely affected.

  In the polypropylene resin composition of the present invention, the blending amount of the ethylene / ethyl acrylate copolymer (EEA) (d) is 1 to 2% by weight, preferably 1 to 1.8% by weight. When the compounding amount of the component (d) is out of this range, the stain resistance is deteriorated or the rigidity is lowered.

(5) Sulfur-based antioxidant (e)
The sulfur-based antioxidant used in the polypropylene-based resin composition of the present invention (hereinafter sometimes abbreviated as component (e)) is not particularly limited, but is preferably dilauryl-3,3′-thiodipropio. And dimyristyl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropionate, and the like.

  In the polypropylene resin composition of the present invention, the amount of the sulfur-based antioxidant (e) is 0.02 to 0.1% by weight, preferably 0.04 to 0.75% by weight. When the amount of component (e) is 0.02% by weight or less, the heat discoloration is inferior, and when it is 0.1% by weight or more, the weather resistance is lowered. In addition, when a sulfur-based antioxidant is not used and only another antioxidant, for example, a phosphorus-based antioxidant is used, the heat discoloration is inferior.

(6) Titanium oxide particles (f)
The titanium oxide particles used in the polypropylene resin composition of the present invention (hereinafter sometimes abbreviated as component (f)) are not particularly limited, but the crystal structure is either a rutile type or an anatase type crystal structure. May be. A rutile type having excellent weather resistance is preferred. In addition, titanium oxide may be surface-treated with Al ₂ O ₃ , SiO ₂ , ZnO or the like in order to improve dispersibility in the use medium and weather resistance in the production process.
Moreover, the particle size of the titanium oxide particles is 0.05 to 2 μm. By setting the particle size within this range, the coloring power, hiding power, etc. are improved.

  In the polypropylene resin composition of the present invention, the compounding amount of the titanium oxide particles (f) is 1.0 to 3% by weight, preferably 1.0 to 2% by weight. When the blending amount of the component (f) is 1.0% by weight or less, the coloring power and the concealment degree are inferior, and when it is 3% by weight or more, the rigidity is lowered, which is not preferable.

(7) Polyethylene (g)
The polyethylene used in the polypropylene resin composition of the present invention (hereinafter sometimes abbreviated as component (g)) is an ethylene / α-olefin copolymer or an ethylene homopolymer. Density polyethylene (f) is, 0.94 g / cm ³ or more, preferably 0.945 g / cm ³ or more, particularly preferably 0.950~0.970g / cm ^3. When the density of the component (g) is out of the above range, the appearance and scratch resistance are inferior, which is inappropriate. Here, the density is a value measured according to JIS K7112.

  In the polypropylene resin composition of the present invention, the blending amount of polyethylene (f) is 0.2 to 1.0% by weight, preferably 0.3 to 0.8% by weight. When the blending amount of polyethylene (f) is 0.2% by weight or less, the stain resistance is poor, and when it is 1.0% by weight or more, the rigidity is adversely affected.

(8) Other ingredients (arbitrary ingredients)
In the propylene-based resin composition of the present invention, the following optional components are included in addition to the above components (a) to (g) in order not to impair the effects of the present invention or to further improve the performance. Can be blended. Specifically, antioxidants, antistatic agents, light stabilizers, ultraviolet absorbers, nucleating agents, flame retardants, dispersants, lubricants, neutralizing agents, and the like can be given.

[II] Production and molding of propylene-based resin composition (1) Production method The propylene-based resin composition used in the present invention is prepared by combining the above components (a) to (g) with the conventionally known methods. It can be manufactured by blending and mixing at a blending ratio and melt-kneading.
Melt-kneading is carried out using a normal kneader such as a single-screw extruder, twin-screw extruder, Banbury mixer, roll mixer, Brabender plastograph, kneader, etc. A resin composition is obtained.
In this case, it is preferable to select a kneading and granulating method capable of improving the dispersion of each component, and it is usually performed using a twin-screw extruder. In this kneading and granulation, the above-mentioned components may be kneaded at the same time, and each component may be divided and kneaded in order to improve the performance, that is, for example, first part of the propylene polymer. Alternatively, a method of kneading the whole and the elastomer and then kneading and granulating the remaining components may be employed.

(2) Molding method The propylene-based resin composition of the present invention can be used for molding by various known methods. For example, various molded products can be obtained by molding by injection molding (including gas injection molding), injection compression molding (press injection), extrusion molding, hollow molding, calendar molding, or the like. Of these, injection molding and injection compression molding are more preferable.

[III] Use of propylene-based resin composition The propylene-based resin composition of the present invention is excellent in dirt resistance, balance of physical properties, and excellent in injection molding processability. It has sufficient performance for practical use as a white exterior member such as bumper, rocker molding, side molding, over fender, back door, garnish, etc.

  EXAMPLES The polypropylene resin composition of the present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples and comparative examples. The raw materials and test methods / evaluation methods used in Examples and Comparative Examples are as follows.

[I] Evaluation method (1) MFR: Based on JIS K7210, it was performed at 230 ° C. and a load of 2.16 kg.
(2) Flexural modulus (unit: MPa): Measured at 23 ° C. according to JIS K7203.
(3) Izod (IZOD) impact strength (unit: J / m ² ): measured at −30 ° C. according to JIS K7110.
(4) Dirt resistance: A 350 mm × 100 mm × 3.0 mmt flat plate test piece produced by injection molding is inclined outdoors at a ground angle of 45 ° with respect to the 350 mm side, and is set outdoors with the evaluation surface facing southward. It was exposed to natural weather for a certain period. By using a long test piece, it was made clear that the trace of raindrops due to rain on the surface of the test piece where dust and oil adhered and accumulated, became dirty. The dirt adhesion test piece obtained by outdoor exposure was washed under running water with a sponge containing a commercially available vehicle washing solution, and the residue of the dirt was evaluated according to the following criteria by visual appearance.
◎ Soil removal almost completely ○ Soil residue can be recognized but sufficiently removed × Stain residue is noticeable (5) Heat-resistant discoloration: 100 mm x 100 mm x 3.0 mmt flat sheet prepared by injection molding in an oven adjusted to 100 ° C After exposure for 500 hours, the hue (YI) was measured. The measurement was carried out with Nippon Denshoku SE2000.

[II] Raw material (1) Crystalline propylene block copolymer [component (a)]
The propylene / ethylene block copolymers (a-1) to (a-5) shown in Table 1 were used.
(2) Ethylene / α-olefin copolymer elastomer [component (b)]
The ethylene / α-olefin elastomers (b-1) to (b-2) shown in Table 2 were used.
(3) Talc [component (c)]
The following (c-1) was used as the component (c).
c-1: LMS200 (manufactured by Fuji Talc, average particle diameter determined by LA920: 6 μm)
(4) Ethylene / ethyl acrylate copolymer (EEA) [component (d)]
As the component (d), the following (d-1) was used.
d-1: Commercially available ethylene-ethyl acrylate copolymer (EEA-1) (weight% of ethyl acrylate copolymer part is 15%)
(5) Sulfur-based antioxidant [component (e)]
The following (e-1) to (e-2) were used as the component (e).
e-1: A commercially available sulfur-based antioxidant was used. (DSTP manufactured by API Corporation)
e-2: A commercially available phosphorous antioxidant was used (Ilfaphos 168 manufactured by Ciba Japan).
(6) Titanium oxide [component (f)]
The following (f-1) was used as component (f).
f-1: Commercially available titanium oxide particles having a particle size of 0.1 μm (Taibak CR-90 manufactured by Ishihara Sangyo)
(7) Polyethylene [component (g)]
As the component (g), the following (g-1) was used.
g-1: a commercially available polyethylene having a density of 0.958 g / cm ³ (manufactured by Nippon Polyethylene Co., Ltd., HJ490D)

(Examples 1-3, Comparative Examples 1-6)
After the components shown in Table 3 were dry blended with a super mixer at the ratio shown in Table 3, a twin screw extruder (KTX44, manufactured by Kobe Steel) was used under conditions of an extrusion temperature of 200 ° C. and a discharge rate of 35 kg / h. Used and melt-kneaded. In addition, as a heat stabilizer at the time of melt-kneading, 0.1 part by weight of Irganox 1010 was added with respect to 100 parts by weight of the composition. Table 4 shows the evaluation results.

As is apparent from Tables 3 and 4, in Examples 1 to 3, which satisfy all the requirements of the present invention, a molded article having good moldability, physical properties, stain resistance and excellent heat discoloration was obtained. .
On the other hand, Comparative Examples 1 to 6 that do not satisfy all or part of the requirements defined in the present invention are inferior to those of the Examples, have good moldability, physical properties, stain resistance, and excellent heat discoloration. No molded product was obtained.

  As is clear from the above, the polypropylene resin composition of the present invention is a white polypropylene resin composition that is excellent in stain resistance and excellent in mechanical properties and injection moldability. As a material, it has sufficient performance for practical use and can be used industrially.

Claims (3)

A white polypropylene resin composition comprising the following components (a) to (g).
Component (a): Crystalline propylene-based block copolymer satisfying the following requirements (i) to (iv): 50 to 65% by weight
(I) MFR is 20 to 120 g / 10 min. (Ii) MFR of crystalline homopolypropylene part is 50 to 300 g / 10 min. (Iii) Ratio of ethylene-α-olefin copolymer part is 5 to 30 wt. % (Iv) The ethylene content of the ethylene-α-olefin copolymer part is 30 to 55% by weight. Component (b): MFR is 0.2 to 10 g / 10 min, and the density is 0.860 to 0.870 g. / Cm ³ ethylene / α-olefin copolymer elastomer 10 to 30% by weight
Ingredient (c): Talc 5-20% by weight
Component (d): Ethylene acrylate copolymer having an ethyl acrylate structural unit ratio of 10 to 20% by weight 1-2% by weight
Ingredient (e): Sulfur-based antioxidant 0.02 to 0.1% by weight
Component (f): Titanium oxide particles having a particle size of 0.05-2 μm 1-3 wt%
Component (g): Polyethylene having a density of 0.94 g / cm ³ or more 0.2 to 1.0% by weight   An exterior part for an automobile, which is molded using the white polypropylene resin composition according to claim 1.   The automotive exterior component according to claim 2, wherein the automotive exterior component is a bumper.