JP3434631B2 - Polypropylene resin composition for automotive interior - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded article which is lightweight, has excellent rigidity, heat deformation resistance, impact resistance and moldability, and hardly causes stress whitening during molding. The present invention relates to a polypropylene resin composition that can be provided. INDUSTRIAL APPLICABILITY The present invention can be suitably used for interior parts for automobiles, mainly trims. 2. Description of the Related Art Conventionally, crystalline ethylene / propylene block copolymers have been widely used as materials for industrial parts such as home appliances and automobiles due to their excellent performance. There is a drawback that it is easy to wake up, so that the appearance of the product is degraded. As a means for improving the stress whitening, a combination of a crystalline ethylene / propylene block copolymer and a crystalline ethylene / propylene random copolymer, or a combination of polyethylene, a specific ethylene / propylene copolymer rubber, and ethylene / butene Compositions combining a copolymer rubber or a specific nucleating agent have been studied. Examples of such a polypropylene-based composition include JP-B-57-26613, JP-B-3-60342, and JP-B3-1339.
The compositions disclosed in JP-B-6-78469 and JP-B-6-55871 are exemplified. However, none of the above compositions is satisfactory from the viewpoint of high rigidity, high impact resistance, and low stress whitening. [0003] In recent years, polypropylene compositions for interior parts for automobiles, mainly trims, have been reduced in weight, increased in rigidity, increased in impact strength and easily formed. In addition, there is a demand for a material that is less likely to cause stress whitening during molding and part fitting. Therefore, the present inventors have intensively studied the composition and combination of the crystalline polypropylene resin and the combination of the crystalline polypropylene resin and the rubber component as an impact resistance improver in order to achieve the above object. As a result, by combining a crystalline ethylene-propylene block copolymer having a specific composition with a specific amount of crystalline propylene homopolymer and compounding with a specific amount of a hydrogenated block copolymer, it is lightweight and rigid. The present inventors have found that a polypropylene resin composition which can provide a molded article having excellent impact resistance and very good stress whitening resistance can be obtained, and completed the present invention. [0004] The polypropylene resin composition for automobile interiors of the present invention comprises the following components. (A) component The ethylene content is 0.5 to 10% by weight, the isotactic pentad fraction (mmmm) of the polypropylene component is 96% or more, and the melt flow rate (MFR; 230 ° C, 2160 g) is 20 to 70 g. / 10 minutes, crystalline ethylene / propylene block copolymer containing a fraction soluble in p-xylene at room temperature with an ethylene content of 50% by weight or less. (B) Component Crystalline propylene homopolymer having an isotactic pentad fraction (mmmm) of 96% or more and a melt flow rate (MFR; 230 ° C., 2160 g) of 10 to 60 g / 10 minutes. (10) to 60% by weight (C) component General formula, A-(-BA) n and / or AB (where A is monovinyl-substituted) B is a conjugated diene elastomeric polymer block, and n is an integer of 1 to 5). A polypropylene resin composition for automobile interiors, comprising 5 to 20% by weight of a polymer. It is. Hereinafter, the present invention will be described in more detail. Component (A) The crystalline ethylene / propylene block copolymer (A) used in the present invention is a crystalline propylene homopolymer (hereinafter referred to as a polypropylene component) which is polymerized in the first step. A mixture with an ethylene / propylene copolymer (hereinafter, referred to as an E / P copolymer rubber) polymerized in the second step, and a titanium trichloride and an alkylaluminum compound usually called a Ziegler-Natta catalyst. Or a composite catalyst of a magnesium compound and a titanium compound or the like. This crystalline ethylene / propylene block copolymer has an ethylene content of 0.5 to 10% by weight, preferably 1.0 to 8.0% by weight, and an isotactic pentad fraction of a polypropylene component (mmmm). Is 96% or more, preferably 97% or more, melt flow rate (MFR; 230 ° C., 2160
g) is from 20 to 70 g / 10 min, preferably from 20 to 70 g / 10 min.
~ 50/10 g. In addition, this crystalline ethylene
The propylene block copolymer contains a fraction soluble in room temperature p-xylene with an ethylene content of 50% by weight or less, preferably 35% by weight or less. The weight fraction of the fraction soluble in p-xylene at room temperature contained in the component (A) is 3 to 20% by weight, preferably 5 to 15% by weight.
When the fraction soluble in p-xylene at room temperature is less than 3% by weight, the fluidity of the composition becomes insufficient, and when it exceeds 20% by weight, the effect of improving stress whitening becomes poor. [0006] Here, the ethylene content is defined as a methyl group (-CH ₃ ) and a methylene group (-C ₃ ) in an infrared absorption spectrum obtained by subjecting a press film specimen to an infrared spectrophotometer.
It was determined by the calibration curve method using the absorbance of the characteristic absorption of H _2- ). Further, the isotactic pentad fraction is an isotactic chain in a pentad unit in a crystalline propylene molecular chain measured using 13C-NMR, and five meso-bonds in a propylene monomer unit are continuously formed. Fraction of propylene monomer units at the center of the resulting chain. Specifically, it is determined as the mmmm peak fraction in the total absorption peak of the methyl carbon region in the 13C-NMR spectrum. If the ethylene content is less than 0.5% by weight, the impact resistance of the composition will be insufficient, and if it exceeds 10% by weight, the heat deformation resistance and the surface hardness will be significantly reduced. mmmm is 9
If it is less than 6%, the rigidity and impact resistance of the composition will decrease. When the MFR is less than 20 g / 10 minutes, the fluidity of the composition is poor, and when it exceeds 70 g / 10 minutes, the effect of improving the impact resistance is poor. Here, the fraction soluble in p-xylene at room temperature is obtained by completely dissolving 5 g of the above-mentioned crystalline ethylene / propylene block copolymer in boiling p-xylene.
The temperature was lowered to 20 ° C., and left for a day and night.
Separating the xylene insolubles; Acetone 1500 in the filtrate
cc was added and the mixture was stirred to remove the polymer, filtered and dried to obtain a polymer soluble in p-xylene. The fraction soluble in p-xylene at room temperature is a component substantially equal to the E / P copolymer rubber polymerized in the second step. ethylene content of p- xylene-soluble fraction at pressing film specimen infrared spectrophotometer, a methyl group in the infrared absorption spectrum (-CH ₃ 1155cm-1) and Mechiren'n group (--CH2 -) characteristic absorption in absorbance Using Ga
It was obtained from a calibration curve of rdner *. (*
I. J. Gardner et al, Rubber C
hem and Tech. , 44, 1015, '7
1). If the content of the fraction soluble in p-xylene at room temperature exceeds 50%, the effect of improving the stress whitening resistance of the composition becomes poor. The content of the component (A) is 20 to 85% by weight, preferably 30 to 7%. If the content is less than 20% by weight, the fluidity of the composition will be insufficient, and if it exceeds 85% by weight, the effect of improving stress whitening resistance will be poor. Component (B) The crystalline propylene homopolymer of the component (B) used in the present invention is a crystalline propylene homopolymer polymerized in the first step of the prepolymerization, and is the same as the component (A). It is polymerized by a Ziegler-Natta type catalyst or a composite catalyst of a magnesium compound and a titanium compound. M of component (B)
mmm is 96% or more, preferably 97% or more.
When the thickness is less than 96 mm, the effect of improving the rigidity and the heat deformation resistance of the composition is poor. The melt flow rate of the component (B) is 10 to 60 g / 10 minutes, preferably 20 to 50 g.
/ 10 minutes. If the melt flow rate is less than 10 g / 10 minutes, the fluidity and moldability of the composition are poor, and the melt flow rate is 60 g.
If the time exceeds / 10 minutes, the impact resistance is reduced. The content of the component (B) is 10 to 60% by weight, preferably 20 to 50% by weight. When the content is less than 10% by weight, the resistance to stress whitening is not improved, and when it exceeds 60% by weight, the fluidity is reduced and the moldability is deteriorated. Component (C) The hydrogenated block copolymer of component (C) used in the present invention is represented by the general formula A-(-BA) n and / or AB
Can be obtained by subjecting the block copolymer represented by Here, in the above general formula, A is a polymer block of a monovinyl-substituted aromatic hydrocarbon, B is a polymer block of a conjugated diene elastomeric property, and n is an integer of 1-5. The monovinyl-substituted aromatic hydrocarbon as a monomer constituting the polymerization block A is preferably styrene,
-Methylstyrene, vinyltoluene and other lower alkyl-substituted styrene and vinylnaphthalene groups are also used. The conjugated diene monomer in the polymer block B is preferably butadiene or isoprene.
When butadiene is used as a single conjugated diene monomer to form the polybutadiene, it is necessary to maintain the elastomeric properties after the block copolymer is hydrogenated and the double bond is saturated. It is preferable to employ polymerization conditions in which the 1,2-microstructure in the block microstructure is 20-50%. More preferably,
The 1,2-microstructure is 35-45%. Numerous methods have been proposed for producing these block copolymers. As a typical method, for example, a method described in Japanese Patent Publication No. 23798/1976, in which a block and a lithium catalyst or a Ziegler type catalyst are polymerized in an inert solvent. The hydrogenation treatment of these block copolymers is described, for example, in JP-B-42-8704 and JP-B-43.
The method is carried out by hydrogenation in the presence of a catalyst in an inert solvent according to the methods described in JP-B-6636 and JP-B-46-20814. By these methods, at least 9 double bonds in the block copolymer
0%, preferably 95% or more is hydrogenated to obtain a hydrogenated block copolymer. The proportion of the polymerization block A in the hydrogenated block copolymer (C) is 5 to 60% by weight,
Preferably it is 10 to 40% by weight. Further, the melt index of the hydrogenated block copolymer (C) (MI: 200
° C, 5 kg) is 100 g / 10 min or less. The content of the component (C) is 3 to 20% by weight, preferably 5 to 18%.
% By weight. If the content is less than 3% by weight, the impact resistance of the composition will be insufficient, and if it exceeds 20% by weight, the rigidity and thermal deformation resistance will be significantly reduced, and the effect of improving the stress whitening resistance will be poor. Specific examples of the hydrogenated block copolymer (C) include styrene / ethylene / butylene / styrene copolymer (SEBS), styrene / ethylene / propylene / styrene (SEPS), and styrene / ethylene / propylene copolymer. (SEP) and the like, of which SEBS is preferable. In order to obtain the polypropylene resin composition for automobile interiors of the present invention, a crystalline ethylene / propylene block copolymer (A) and a crystalline propylene homopolymer (B)
And the water-added block copolymer (C) are blended with various known methods within the above range, for example, using a Henschel mixer, a V-blender, a ribbon blender, etc. In addition to the raw material supply port, a method of melting and mixing with a twin-screw extruder having a raw material supply port in a cylinder portion, a kneader, a Banbury mixer or the like, and then pelletizing can be employed. An inorganic filler component such as talc or calcium carbonate can also be used in the polypropylene resin composition for automobile interiors of the present invention within a range not incompatible with the purpose. The composition of the present invention may contain, if necessary, an antioxidant, an ultraviolet absorber, a light stabilizer, a pigment, a dispersant, a moldability improver, an antistatic agent, a lubricant, a nucleating agent, a release agent and the like. Can be added. As an antioxidant, 2,6-di-t-
Butylphenol, 2,6-di-t-butyl-4-ethylphenol, 2,6-di-t-butyl-4-n-butylphenol, 2,6-di-t-butyl-α-dimethylamino-p- Cresol, 6- (4-hydroxy-3,
5-di-t-butylaniline) -2,4-bisoctyl-thio-1,3,5-triazine, N-octadecyl-
3- (4'-hydroxy-3 ', 5'-di-t-butylphenyl) butane, tetrakis [methylene-3-
(3 ', 5'-di-tert-butylphenyl-4'-hydroxyphenyl) propionate] methane, 1,3,5-
Trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, dilaurylthiodipropiodinate and the like. As the ultraviolet absorber and the light stabilizer, 2
-Hydroxy-4-n-octoxybenzophenone, 2
-Hydroxy-4-octadecyloxybenzophenone,
4-dodecyloxy-2-hydroxybenzophenone,
2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, 1,2 , 3,4-butanetetracarboxylic acid-
Examples thereof include 1,2,2,6,6-pentamethyl-4-piperidinol tridecyl alcohol condensate. Hereinafter, the present invention will be described in detail with reference to examples. The methods for measuring physical properties in the examples are shown below. The test piece used for the measurement of the physical properties was injection-molded using a J100SAII type injection molding machine manufactured by Nippon Steel Works Co., Ltd. under the conditions of a cylinder set temperature of 230 ° C. and a mold temperature of 40 ° C. (1) Melt flow rate (MFR) Measured according to the method specified in ASTM D1238. (2) Flexural modulus (FM) It was measured by a method specified in ASTM D790. (3) Tensile yield point strength (TYS) According to the method specified in ASTM D638. (4) Heat distortion temperature (HDT) It was measured by a method specified in ASTM D648.
Fiber stress was measured at 4.6 kg / cm ² . (5) Surface hardness (RH) Measured by a method specified in ASTM D685.
The steel balls used R and the value of the evaluation was indicated on an R scale. (6) Izod impact strength (IZOD) Measured according to the method specified in ASTM D256.
The measurement was performed at 23 ° C. (7) Density (d) According to the method specified in ASTM D1505. (8) High speed impact strength (HSI) A 100 mmΦ, 1.6 mmt disk molded product was used as a test product, and a 1 inch φ round missile was dropped at −100 ° C. at a speed of 2.5 m / sec onto this disk. The fracture energy was calculated from the area of the stress-strain curve at the time of fracture. (9) Fluidity Fluidity was 2 mm thick, 10 mm wide, and 2000 mm long.
Injection molding was performed using a resin flow length measurement mold having a spiral flow path described above, and the flow length was measured and determined. (10) A DuPont impact test was performed on a disk molded product having a degree of whitening of 100Φ and 1.6 mmt, and the degree of whitening of the molded product was visually determined. [Each Component of Polypropylene Resin Composition]
The polypropylene resin compositions used in the examples and comparative examples are as shown in Table 1. [Table 1] [Impact modifiers] The impact modifiers used in Examples and Comparative Examples are as follows. R-1: a styrene / ethylene / butylene / styrene copolymer having a melt index of 9 (200 ° C., 5 kg) and a styrene content of 13% by weight (SEBS: Shell Chemical Clayton G1657). R-2: Mooney viscosity ML1 + 4 (100 ° C.) is 24,
Ethylene / propylene copolymer rubber having a propylene content of 26% (EP02P manufactured by Japan Synthetic Rubber). R-3: an ethylene / butene-1 copolymer rubber having a melt index (190 ° C.) of 4 and a butene-1 content of 20% by weight (A4085 manufactured by Mitsui Petrochemical). R-4: high-density polyethylene (Showa Denko Shorex 5050). [Others] N-1: methylene (2,4-di-t-butylpheno-
B) Acid phosphate Na salt (NA-1 manufactured by Asahi Denka)
1). [Examples 1 and 2, Comparative Examples 1 to 8] Polypropylene having the compounding formulation shown in Table 2 was mixed with a rubber component, and the following additives and pigments using a tumbler mixer.
Melt kneading was performed with a twin screw extruder, and pellets were molded into test pieces using an injection molding machine, and physical properties were tested. Additives 2,6-di-tert-butyl-4-methylphenol-tetrakis- [methylene-3- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate] methane・ Bis- (2,2,6,6-tetramethyl-4-piperidyl) sebacate pigment ・ Iron oxide ・ Titanium oxide [Table 2] Table 2 shows the results. Compared with the example, the comparative example 1 is significantly inferior in stress whitening resistance. Comparative Example 2 has significantly poor fluidity. Comparative Example 3 is inferior in rigidity and heat-resistant deformation, and Comparative Example 4 is inferior in stress whitening resistance in addition to rigidity and heat-resistant deformation. Comparative Example 5 is inferior in impact resistance and stress whitening resistance, and Comparative Examples 6 and 7 are inferior in impact resistance. Further, although the comparative example 8 is an improvement of the comparative example 3, the rigidity and the impact resistance are inferior to the examples. The polypropylene resin composition of the present invention is obtained by combining a specific crystalline ethylene / propylene block copolymer with a specific amount of a crystalline propylene homopolymer to form a specific amount of a hydrogenated block copolymer. By compounding, it is lightweight, has excellent rigidity and impact resistance, and further has improved stress whitening resistance of a molded product. In particular, it can be suitably used for all automotive interior parts, mainly trim materials, which require stress whitening resistance during molding or assembling parts.

Continuation of front page (56) References JP-A-6-179785 (JP, A) JP-A-6-329850 (JP, A) JP-A-5-132606 (JP, A) JP-A-8-302107 (JP) JP-A-8-92440 (JP, A) JP-A-9-66557 (JP, A) JP-A-8-20684 (JP, A) JP-B-6-78469 (JP, B2) (58) Field surveyed (Int. Cl. ⁷ , DB name) C08L 53/00 C08L 23/12

Claims (1)

(57) [Claims 1] (A) Component Melt flow, ethylene content 0.5 to 10% by weight, isotactic pentad fraction (mmmm) of polypropylene component 96% or more A crystalline ethylene / propylene block copolymer having a latet (MFR; 230 ° C., 2160 g) of 20 to 70 g / 10 min and containing a fraction soluble in room temperature p-xylene having an ethylene content of 50% by weight or less. ‥‥‥‥‥‥‥‥‥‥‥‥ 20-85% by weight (B) component Isotactic pentad fraction (mmmm) is 96% or more, and melt flow rate (MFR; 230 ° C., 2160 g) is 10 Crystalline propylene homopolymer having a weight of 60 g / 10 minutes {10 to 60% by weight (C) component General formula, A-(-BA) n and / or A A block copolymer represented by B (where A is a polymerization block of a monovinyl-substituted aromatic hydrocarbon, B is a conjugated diene elastomeric polymerization block, and n is an integer of 1 to 5) A polypropylene resin composition for automobile interiors, comprising 5 to 20% by weight of a hydrogenated block copolymer hydrogenated by 90% or more.