JP2009173892A - Polypropylene resin composition for extrusion molding and blow-molded article comprising the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polypropylene composition which can be used for forming automotive exterior parts such as bumpers and roofs, pallets, building materials, large blow-foamed materials, large sheets, and foamed members, is suitable for forming large blow-molded articles having complicated shapes, and has improved draw-down resistance, low density, high rigidity, and pinch-off strength. <P>SOLUTION: Provided is the polyolefin resin composition for hollow molding, characterized by comprising 100 pts.wt. of a polypropylene resin material comprising 50 to 90 mass% of the following component (a) and 10 to 50 mass% of the following component (b) [the total amount of the components (a) and (b) is 100 mass%], and 1 to 40 pts.wt. of a component (c): a hydrogenation product of a styrene-conjugated diene block copolymer. The component (a): crystalline propylene polymer resin having a melt flow rate (MFR) of ≤2 g/10 min[230°C, 21.18N], the component (b): highly crystalline polypropylene having an MFR of ≤1 g/10 min and a flexural modulus of 1,800 to 2,600 MPa. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polypropylene resin composition for extrusion molding and a blow molded article comprising the same, and more specifically, molding a large blow molded article having improved low specific gravity, rigidity, heat resistance, pinch-off strength and excellent drawdown resistance. The present invention relates to a polypropylene resin composition for extrusion molding suitable for carrying out, and a blow molded article comprising the same.

It is essential that the resin used in the extrudable form such as blow molding is excellent in resistance to drawdown. In general, polypropylene is excellent in surface quality such as heat resistance, smoothness, and gloss, but has poor draw-down resistance during extrusion molding, and particularly has a longitudinal dimension of 1.3 m or more. When it is used as a blow molding material for a long molded product, a problem that the thickness of the molded product becomes non-uniform due to drawdown becomes obvious. On the other hand, polyethylene has better drawdown resistance than polypropylene. Among these, high-density polyethylene is suitable as a blow molding material because it has even better properties, but has disadvantages inferior in heat resistance and surface quality.
Therefore, an extrusion molding material based on a resin composition of polypropylene and high-density polyethylene that complement each other with the drawbacks of polypropylene and polyethylene is used.

  In addition, recently, it has been required to impart paintability and high impact resistance to the molded body. Therefore, an ethylene / α-olefin copolymer rubber is blended into the molding material, and rigidity and Since it is required to impart heat resistance, it has been proposed to blend an inorganic filler. (See Patent Document 1 and Patent Document 2). However, since these molding materials have a low melt flow rate (MFR) of the high-density polyethylene to be used, the surface smoothness of the long molded article is not satisfactory.

In recent years, as a method for imparting surface smoothness and paint adhesion without impairing blow moldability, a hydrogenated styrene / conjugated diene block copolymer (such as SEBS) is added to polypropylene resin, or propylene is applied to the surface layer. These problems are solved by optimizing the viscosity and composition ratio of the homopolymer of ethylene and the copolymer of ethylene-propylene, and forming a multilayer hollow molding using an olefin polymer having a specific intrinsic viscosity and melt tension as the inner layer resin. Techniques have been proposed (see Patent Document 3, Patent Document 4, and Patent Document 5). However, in order to give rigidity and heat resistance, it is necessary to add an inorganic filler, and there are problems such as a decrease in pinch-off strength and an increase in specific gravity due to the addition of an inorganic filler. Technology development is required.
Japanese Patent Laid-Open No. 3-197542 Japanese Unexamined Patent Publication No. 3-59049 Japanese Patent Laid-Open No. 7-316361 JP-A-10-251465 JP 2000-334866 A

  In view of the above-mentioned conventional problems, the present invention is a polypropylene resin composition for extrusion molding suitable for molding a large blow molded product having improved low specific gravity, rigidity, heat resistance, pinch-off strength and excellent drawdown resistance. The purpose is to provide goods.

  As a result of intensive studies to solve the above problems, the present inventors have found that a crystalline propylene homopolymer having a Mw / Mn of 5 to 20 and a propylene having a Mw / Mn smaller than that of the crystalline propylene homopolymer. By using a polypropylene composition with specific characteristics that is a homopolymer of polypropylene resin material blended with a hydrogenated styrene / conjugated diene block copolymer, low density and high The inventors have found that a blow molded article having improved rigidity, heat resistance and pinch-off strength can be obtained, and have completed the present invention.

That is, according to 1st invention of this invention, with respect to 100 weight part of polypropylene resin materials which consist of the following component (a) 50-90 mass% and the following component (b) 10-50 mass%, the following 1 to 40 parts by weight of the component (c) is provided, and a polypropylene resin composition for extrusion molding is provided.
Component (a): Crystalline propylene homopolymer (a1) having an Mw / Mn of 5 to 20, or a crystalline propylene ethylene block copolymer having the crystalline propylene homopolymer portion and the propylene ethylene copolymer portion (A2) with a melt flow rate (230 ° C. 21.18 N) of 2 g / 10 min or less and a flexural modulus of 900 to 1500 MPa Component (b): Mw / Mn of 1 to 9 and the crystallinity A propylene homopolymer (b1) smaller than Mw / Mn of the propylene homopolymer (a1), or a propylene ethylene block copolymer (b2) having the propylene homopolymer portion and the propylene ethylene copolymer portion, wherein the melt flow rate (230 21.18N) is 0.03 to 3 g / 10 min, and the flexural modulus is 1800 to 260. MPa ones component (c): a hydrogenated product of a styrene-conjugated diene block copolymer.

Further, according to the second invention of the present invention, in the first invention, the propylene homopolymer of the component (b) is obtained by homopolymerizing propylene in at least two stages, and among the polymer parts produced in each stage, When the intrinsic viscosity of the polymer part having the highest molecular weight is [η] H and the intrinsic viscosity of the polymer part having the lowest molecular weight is [η] L, the relational expression (1) Is satisfied, and a polypropylene resin composition for extrusion molding is provided.
3.0 ≦ [η] H− [η] L ≦ 6.5 (1)

  On the other hand, according to 3rd invention of this invention, the blow molded object formed by shape | molding the polypropylene resin composition for extrusion which concerns on 1st or 2nd invention with a blow molding machine is provided.

  According to the polypropylene resin composition for extrusion molding of the present invention, not only the draw-down resistance at the time of blow molding is improved, but also the light weight pinch-off strength due to low density and high rigidity is remarkably excellent. Therefore, it becomes possible to obtain a blow molded body having a large and complicated shape, and is excellent for molding automobile exterior parts such as bumpers.

1. Polypropylene Resin Composition for Extrusion Molding The polypropylene resin composition for extrusion molding of the present invention is a polypropylene resin material 100 weight comprising the following component (a) 50 to 90% by mass and the following component (b) 10 to 50% by mass. 1 to 40 parts by weight of the following component (c) is included with respect to parts.
Below, each component, the physical property of a resin composition, a manufacturing method, a molded object using the same, etc. are demonstrated in detail.

(1) Component (a)
The component (a) is either a crystalline propylene homopolymer (a1) or a crystalline propylene ethylene block polymer (a2) having the crystalline propylene homopolymer and a propylene ethylene copolymer. The crystalline propylene homopolymer (a1) includes, in addition to the propylene homopolymer, a propylene copolymer in which a comonomer such as ethylene or 1-butene is copolymerized as long as the effects of the present invention are not significantly impaired. The amount of comonomer is less than 1% by mass.

In the crystalline propylene homopolymer (a1), the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) obtained by GPC measurement is 5 to 20, preferably 6 to 15, more preferably. Is 7-11. When Mw / Mn is less than the lower limit, the drawdown resistance is lowered, and when it exceeds the upper limit, the pinch-off strength is lowered. Mw / Mn is measured by gel permeation chromatography (GPC) under the following measurement conditions.
Apparatus: GPC 150C type manufactured by Waters Inc. Detector: 1A infrared spectrophotometer manufactured by MIRAN (measurement wavelength: 3.42 μm)
Column: Three AD806M / S manufactured by Showa Denko Co., Ltd. (column calibration was performed by Tosoh monodisperse polystyrene (0.5 mg / ml solution of each of A500, A2500, F1, F2, F4, F10, F20, F40, and F288) Measurement was performed and the logarithm of the elution volume and molecular weight was approximated by a quadratic equation, and the molecular weight of the sample was converted to polypropylene using the viscosity equation of polystyrene and polypropylene, where the coefficient of the viscosity equation of polystyrene is α = 0.723, log K = -3.967, polypropylene has α = 0.707, log K = -3.616.)
Measurement temperature: 140 ° C
Concentration: 20 mg / 10 mL
Injection volume: 0.2ml
Solvent: Orthodichlorobenzene Flow rate: 1.0 ml / min Viscosity formula: log [η] = log K + α × log M

The crystalline propylene homopolymer (a1) used in the present invention tends to have low heat resistance when the melting point is low, and the heating time during molding tends to be long when the melting point is high. It is preferable that it is -170 degreeC.
Here, melting | fusing point means the peak of the endothermic curve obtained by a differential scanning calorimeter (DSC). The measuring method is, for example, using a Perkin Elmer DSC7 type, and a sample of about 10 mg is heated to 230 ° C. at a temperature rising rate of 0 ° C. to 20 ° C./min, held for 3 minutes, and then 5 ° C./min. The temperature is lowered to 0 ° C. at a temperature lowering rate, held for 5 minutes, and then the peak temperature of the endothermic curve obtained when the temperature is raised to 230 ° C. at a temperature rising rate of 20 ° C./min is obtained.
The crystallinity in the crystalline propylene polymer of the present invention means that it has an endothermic peak based on crystal melting in DSC measurement, and preferably has an endotherm of 30 J / g or more.

  On the other hand, the crystalline propylene ethylene block copolymer (a2) is preferably copolymerized at a ratio of 40 to 99% by mass of the crystalline propylene homopolymer portion and 1 to 60% by mass of the propylene ethylene copolymer portion. The crystalline propylene homopolymer portion of the crystalline propylene ethylene block polymer (a2) has the same structure as the crystalline propylene homopolymer (a1). The proportion of the crystalline propylene homopolymer portion relative to the entire crystalline propylene ethylene block polymer (a2) is preferably 60 to 95 mass%, more preferably 70 to 93 mass%. Moreover, 5-40 mass% is preferable, and, as for the ratio of a propylene ethylene copolymer part, More preferably, it is 7-30 mass%.

The MFR (JIS-K7210, measured at 230 ° C. and 21.18 N load) of the component (a) of the present invention is 2 g / 10 min or less, preferably 1.5 g / 10 min or less, more preferably 0.1 ~ 0.5 g / 10 min. When MFR is too high, drawdown resistance will fall.
The flexural modulus of the component (a) of the present invention is 900-1500 MPa, preferably 1000-1500 MPa, more preferably 1100-1500 MPa. If it is less than the lower limit, the rigidity is lowered, and if it exceeds the upper limit, the impact is lowered.

(2) Component (b)
Component (b) is either a propylene homopolymer (b1) or a propylene ethylene block copolymer (b2) having the propylene homopolymer and a propylene ethylene copolymer.
The propylene homopolymer (b1) used in the present invention includes a propylene homopolymer and a propylene copolymer in which a comonomer such as ethylene and 1-butene is copolymerized as long as the object of the present invention is not significantly impaired. It is. The amount of comonomer is less than 1% by mass.

The propylene homopolymer (b1) has a ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) obtained by the GPC measurement of 1 to 9, preferably 3 to 8, more preferably 4 ~ 7. When Mw / Mn is less than the lower limit, the draw-down resistance is lowered, and when it exceeds the upper limit, the surface property of the molded product is lowered. In addition, the measurement of Mw / Mn is performed by the above-mentioned method.
Further, the value of Mw / Mn of the propylene homopolymer (b1) needs to be smaller than the value of Mw / Mn of the crystalline propylene homopolymer of the component (a), preferably 1 or more, more preferably 2 or smaller. When the value of Mw / Mn of the propylene homopolymer is equal to or higher than the value of Mw / Mn of the crystalline propylene homopolymer of component (a), the balance between the drawdown resistance and the pinch-off strength becomes insufficient.

  The propylene homopolymer (b1) used in the present invention has a tendency that the heat resistance is lowered when the melting point is low, and the heating time during molding tends to be long when the melting point is high. It is preferable that Here, the melting point is measured by the method described above.

The propylene homopolymer (b1) of the present invention is obtained by homopolymerizing propylene in at least two stages, and the intrinsic viscosity of the polymer part having the highest molecular weight (also referred to as high molecular weight polymer) among the polymer parts produced in each stage. Is [η] H and the intrinsic viscosity [η] L of the polymer part having the lowest molecular weight (also referred to as a low molecular weight polymer), [η] H and [η] L satisfy the relational expression (1). It is preferable to do.
3.0 ≦ [η] H− [η] L ≦ 6.5 (1)
More preferably, the relational expression (1) ′ is satisfied.
3.5 ≦ [η] H− [η] L ≦ 5.5 (1) ′
If it is less than the lower limit of relational expression (1), melt viscoelasticity will fall and molding processability will fall. When the upper limit is exceeded, the molecular weight disparity becomes excessive and non-uniformity increases, resulting in poor appearance such as rough skin.

When the polymerization is performed in two stages, the high molecular weight polymer is preferably 35 to 65% by mass, more preferably 40 to 60% by mass, and the low molecular weight polymer is preferably used. It is 35-65 mass%, More preferably, it is 40-60 mass%. Here, the total of the high molecular weight polymer and the low molecular weight polymer is 100% by mass. Within this range, good melt fluidity is obtained, and kneading during granulation is good, which is preferable.
In the case where the propylene homopolymer (b1) is polymerized in three or more stages, it is preferable that the amount of each polymer is close to an equivalent amount, and the amount ratio of the high molecular weight polymer to the low molecular weight polymer is 0.5. -1.5, more preferably 0.75-1.25. Within this range, good melt fluidity is obtained and kneading during granulation is also good.

Here, the polymerization ratio of the polymer at each stage is obtained from the mass balance, and the intrinsic viscosity is obtained from the intrinsic viscosity measured at 135 ° C. in the polymer tetralin solution at the end of each stage polymerization by the following formula.
W ^T _n × [η] ^T _n = W ^T _n−1 × [η] ^T _n−1 + (W ^T _n −W ^T _n−1 ) × [η] _n
Here, W ^T _n-1 is the total amount of the polymer up to the n-1 stage, W ^T _n is the total amount of the polymer up to the n stage, and [η] ^T _n-1 is n The intrinsic viscosity of the polymer at the end of the first stage polymerization, [η] ^T _n is the intrinsic viscosity of the polymer at the end of the n stage polymerization, and [η] _n is the intrinsic viscosity of the n stage polymer. n is an integer of 2 or more and does not exceed the number of all polymerization stages.

Although the example of the manufacturing method of the propylene homopolymer (b1) based on this invention is as showing below, it is not limited to this method.
It can be obtained by polymerizing propylene in multiple stages in the presence of the following catalyst. For example, an organoaluminum compound (I) such as triethylaluminum or diethylaluminum monochloride, or a reaction product (VI) of an organoaluminum compound (I) and an electron donor (a) such as diisoamyl ether is converted into titanium tetrachloride (c The solid product (II) obtained by reacting with an electron donor (a) and an electron acceptor (b), for example, titanium tetrachloride, is reacted with organoaluminum. In combination with a compound (IV) such as triethylaluminum, diethylaluminum monochloride and the like and an aromatic carboxylic acid ester (V) such as methyl p-toluate, the aromatic carboxylic acid ester (V) and the solid product (III ) Molar ratio V / III = 0.1 to 10.0.
Multi-stage polymerization can be carried out by changing the temperature, pressure, concentration of chain transfer agent such as hydrogen, etc. in stages using a single polymerization tank, such as temperature, pressure, hydrogen, etc. You may carry out using several polymerization tanks from which polymerization conditions, such as a density | concentration of a chain transfer agent differ, and combining both.
As the polymerization mode, known modes such as bulk polymerization, solution polymerization, and gas phase polymerization can be adopted. The polymerization mode of each polymerization stage may be the same or different.
The propylene homopolymer (b1) of the present invention is characterized in that the difference in intrinsic viscosity between the highest molecular weight polymer and the lowest molecular weight polymer is relatively large. The conditions are determined in the absence of a chain transfer agent such as hydrogen at the stage of obtaining the highest molecular weight polymer, and in the presence of sufficient chain transfer agent at the stage of obtaining the lowest molecular weight polymer. It is preferable.

In the propylene homopolymer (b1) of the present invention, the relationship between the isotactic pentad fraction (P) and the MFR preferably satisfies the following formula. A propylene homopolymer that does not satisfy this relational expression (2) has a flexural modulus that is difficult to satisfy the requirements of the present invention.
1 ≧ P ≧ 0.015 × log (MFR) +0.955 (2)

  Here, the isotactic pentad fraction is a pentad unit in a propylene-based polymer molecular chain measured using a method described in Macromolecules, 925-926 (1973), that is, 13C-NMR. The isotactic fraction of In other words, the fraction means a fraction of propylene monomer in which five propylene monomer units are isotactically bonded continuously. The spectral peak assignment method in the measurement using 13C-NMR described above is based on Macromolecules, 687-689 (1975). Specifically, the measurement by 13C-NMR can be carried out using a 270-MHz FT-NMR apparatus and improving the signal detection limit of 27000 times to 0.001 in terms of isotactic pentad fraction.

  Component (b) of the present invention may be a propylene ethylene block copolymer (b2) having a propylene homopolymer portion and a propylene ethylene copolymer portion. The propylene homopolymer portion in this propylene ethylene block copolymer (b2) has the same structure as the propylene homopolymer (b1).

The propylene ethylene block copolymer (b2) can be obtained by a method including a propylene homopolymer polymerization step and a propylene ethylene random copolymer polymerization step.
In the propylene homopolymer polymerization step, it is important to produce a propylene homopolymer having the same properties as the propylene homopolymer described above. The order of the propylene homopolymer polymerization step and the propylene ethylene random copolymer polymerization step is not particularly limited. The property of the propylene homopolymer portion is determined by measuring the property of the propylene homopolymer obtained by separately performing only the propylene homopolymer polymerization step.

  The ratio of the propylene ethylene copolymer portion determined as the 23 ° C. xylene soluble content is 7 mass% or less when the total amount of the propylene ethylene block copolymer (b2) is 100 mass%. When the proportion of the propylene ethylene copolymer portion exceeds 7% by mass, it becomes difficult to satisfy the requirements for flexural modulus.

Component (b) of the present invention has an MFR (measured at JIS-K7210, 230 ° C., 21.18 N load) of 0.03 to 3 g / 10 minutes, preferably 0.1 to 2 g / 10 minutes, more preferably 0. .2 to 1 g / 10 min. If it is less than the lower limit, the surface appearance of the molded product is deteriorated, and if it exceeds the upper limit, the drawdown resistance is lowered.
Component (b) of the present invention has a flexural modulus of 1800 to 2600 MPa, preferably 2000 to 2600 MPa, and more preferably 2200 to 2600 MPa. If it is less than the lower limit, the rigidity is lowered, and if it exceeds the upper limit, the impact property is lowered.

(3) Component (c): Hydrogenated product of styrene / conjugated diene block copolymer The hydrogenated product of styrene / conjugated diene block copolymer used in the present invention is a block using butadiene, isoprene or the like as the conjugated diene. This is a hydrogenated copolymer, such as styrene / ethylene / butylene / styrene (SEBS) or styrene / ethylene / propylene / styrene (SEPS), as well as hydrogenated block copolymer of styrene, butadiene and isoprene. There are things. Here, styrene derivatives such as α-methylstyrene and p-methylstyrene can also be used as styrene.

By blending a hydrogenated product of these styrene / conjugated diene block copolymers, the melt tension is improved and the drawdown resistance in hollow molding is improved, which is very effective for large-scale hollow molding. However, since this blending reduces the melt fracture rate and makes it difficult to stretch, in the case of hollow molding with a large blow ratio, such as deep-drawn shapes or complex shaped molds, it has extensibility such as parison tearing and uneven thickness of the molded product. In addition to the problem of lowering, the economical efficiency of the composition is impaired.
The hydrogenated styrene / conjugated diene block copolymer used here is not particularly limited as long as a hollow molded body that satisfies the above-mentioned requirements can be obtained, but the density in JIS-7112 is 0.00. It is preferably 90 to 0.92 g / cm ³ , a styrene content of 31 to 40% by mass, and a viscosity by the BMS0380 method of about 1.5 Pa · s.

(4) Compounding amount of component The compounding amount of the component of the said component (a)-component (c) is as follows.
That is, 1 to 40 parts by weight of the component (c) is included with respect to 100 parts by weight of the polypropylene resin material composed of 50 to 90% by weight of the component (a) and 10 to 50% by weight of the component (b).
The amount of component (a) is preferably 60 to 90% by mass, more preferably 75 to 85% by mass, and the amount of component (b) is preferably 10 to 40% by mass, more preferably 15 to 25% by mass. When the blending amount of (b) in (a) and (b) is less than the lower limit, the rigidity is lowered, and when it exceeds the upper limit, the low temperature impact is lowered.
The amount of component (c) is preferably 4 to 15 parts by weight, more preferably 6 to 10 parts by weight with respect to 100 parts by weight of the polypropylene resin material comprising component (a) and component (b). If the amount of the component (c) is too small, the drawdown resistance is lowered, while if too large, the extensibility, heat-resistant rigidity, and pinch-off strength at the time of molding are lowered.

(5) Other component (d)
In the present invention, the component (a), the component (b), and the component (c) may be blended with the other component (d) within a range that does not significantly impair the object of the present invention. it can. This component (d) is an optional component such as butene polymer resin, other polyolefins such as 4-methylpentene-1 polymer resin, thermoplastic resins such as polyamide and polyester, and conjugated diene copolymers. Other elastomers such as rubber and styrene / conjugated diene copolymer rubber, inorganic fillers, antioxidants, UV absorbers, light stabilizers, lubricants, lubricants, plasticizers, thickeners, antistatic agents, flame retardants And various additives such as a processability improver, a colorant, a nucleator, a molecular weight modifier, and a paint improver. These components may be added to the composition or may be added to each component.
Examples of the inorganic filler include talc, mica, calcium carbonate, magnesium carbonate, calcium sulfate, magnesium sulfate, barium sulfate, molybdenum sulfide, carbon black, glass fiber, carbon fiber, potassium titanate fiber, titanium oxide, clay, and kaolin. Examples thereof include plates such as alumina, silica and hollow glass spheres, needles, granules and fibers. Although the heat resistance rigidity can be improved by adding these inorganic fillers, in the present invention, there are concerns about problems such as a decrease in pinch-off strength and an increase in specific gravity, so it is desirable to reduce the amount used as much as possible. .

2. Production of Polypropylene Resin Composition for Extrusion Molding The polypropylene resin composition for extrusion molding of the present invention contains the above components (a) to (c), and if necessary, further contains other components (d). For example, it is generally obtained by heat-melt kneading using an ordinary mixing and kneading machine such as a high-speed mixer, a Banbury mixer, a continuous kneader, a single or twin screw extruder, a roll, and a Brabender plastograph. At this time, a granulation method is usually employed.
As a result, the melt tension at 230 ° C. is 10 g or more, good draw-down resistance, low density (0.93 g / cm ³ or less), high rigidity (1300 MPa or more), low temperature impact (5 kJ / m ² As described above, a composition having improved pinch-off strength retention (85% or more) can be obtained.

  Since the polypropylene resin composition for extrusion molding of the present invention is a high melt tension material, it can be suitably used for extrusion molding. As extrusion molding, hollow molding, sheet molding, profile extrusion molding, and the like are applicable. According to the hollow molding, the blow molded body described below can be produced, and the sheet molding is suitably used for the production of parts and products such as large foam sheets, interior members (deck board, tonneau cover) and the like.

3. Blow Molded Body The polypropylene resin composition for extrusion molding of the present invention obtained in this way is molded by a normal blow molding machine to become a blow molded body. In particular, the effect of the present invention is effectively exhibited when molded so as to obtain a large blow molded article having a dimension of 1.3 m or more.
Examples of the large blow molded article include parts and products such as pallets, automobile bumpers, construction machinery, roofs for agricultural machinery, bonnets, engine covers, fenders, and exterior panels, and are preferably used.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited thereto without departing from the gist thereof.

Various evaluation methods in Examples and Comparative Examples are as follows.
(1) Density (unit: g / cc): Measured by an underwater substitution method in accordance with JIS-7112.
(2) MFR (unit: g / 10 min): Measured based on test condition 14 (230 ° C .; 21.18 N) of JIS K7210.

(3) Mw / Mn is measured by gel permeation chromatography (GPC). The measurement conditions are as follows.
Apparatus: GPC 150C type manufactured by Waters Inc. Detector: 1A infrared spectrophotometer manufactured by MIRAN (measurement wavelength: 3.42 μm)
Column: Showa Denko Co., Ltd. AD806M / S 3 (column calibration is Tosoh monodisperse polystyrene (A500, A2500, F1, F2, F4, F10, F20, F40, F288 each 0.5 mg / ml solution) The logarithm of the elution volume and molecular weight was approximated by a quadratic equation, and the molecular weight of the sample was converted to polypropylene using the viscosity equation of polystyrene and polypropylene, where the coefficient of the viscosity equation of polystyrene was α = 0. .723, log K = −3.967, and polypropylene has α = 0.707 and log K = −3.616.)
Measurement temperature: 140 ° C
Concentration: 20 mg / 10 mL
Injection volume: 0.2ml
Solvent: Orthodichlorobenzene Flow rate: 1.0 ml / min Viscosity formula: log [η] = log K + α × log M

(4) Melt tension (MT) (unit: g): Using a Capillograph manufactured by Toyo Seiki Co., Ltd., the resin was put into a cylinder having a diameter of 10 mm heated to 230 ° C., and melted at an indentation speed of 10.0 mm / min. The resin extruded from an orifice having a diameter of 2.095 mm and a length of 8 mm was taken out at a speed of 4.0 m / min, and the melt tension was measured as an index of resistance to drawdown.
(5) Drawdown resistance: Automotive bumper with resin temperature of 220 ° C, length of 2.2m, width of 0.4m, and weight of 8kg using Plako DA-100 large blow molding machine When the molded body is molded, the lower thickness and the upper thickness of the molded body are measured, and the ratio of the upper wall thickness to the lower thickness of the molded body is 0.8 to 1.0, or less than 0.8 or molded A defective or unmoldable product was regarded as defective.
(6) Pinch-off strength: Molded so as to include the bottom pinch-off portion of a 500 cc round bottle having a bottom wall thickness of 1.0 mm, using an IHI IPB-10A small blow molding machine under molding conditions of a resin temperature of 200 ° C. And punched into a dumbbell shape. Using this test piece, the breaking strength at a tensile speed of 10 mm / min was measured. A value measured using a test piece punched into a dumbbell shape so as not to include a pinch-off portion was taken as 100%, and a retention rate of 85% or more was considered good and less than 85% was regarded as bad.

(7) Flexural modulus (unit: MPa): Measured at 23 ° C. in accordance with JIS-K7171.
(8) Izod (IZOD) impact strength (unit: kJ / m ² ): measured at −30 ° C. in accordance with JIS-K7110.
(9) Deflection temperature under load (HDT, unit: ° C.): Measured under the condition of 0.45 MPa in accordance with JIS-K7191-2.

In the examples and comparative examples, the following resins and fillers were used.
(1) Crystalline polypropylene resin PP1 (a1) MFR 0.5 g / 10 min block copolymer having a homo PP portion of Mw / Mn 8.6 manufactured by Nippon Polypro Co., Ltd., and its flexural modulus is 1200 MPa.
PP2 (a1) MFR 0.5 g / 10 min block copolymer having a homo PP portion of Mw / Mn 8.0 manufactured by Nippon Polypro, flexural modulus is 1400 MPa.
PP3 (a1) Nippon Polypro's MFR 2.5 g / 10 min block copolymer having a homo PP portion of Mw / Mn4.5, flexural modulus is 1700 MPa.
PP4 (a1) MFR 6.1 g / 10 min block copolymer having a homo PP portion of Mw / Mn 7.0 manufactured by Nippon Polypro, flexural modulus is 1200 MPa.
PP6 (a1) Nippon Polypro's Mw / Mn 7.0 homo PP part MFR 0.5 g / 10 min block copolymer, flexural modulus is 1200 MPa.

(2) Highly crystalline propylene composition PP5 (b1) Propylene homopolymer (manufactured by Nippon Polypro Co., Ltd.) MFR 0.5 g / 10 min, Mw / Mn 6.0, isotactic pentad fraction 0.967 The polymerization ratio is the first stage / second stage / third stage = 35/33/32 (% by mass), and [η] of each stage is the first stage / second stage / third stage = 2.0 / 3.7 / 5.8) and the flexural modulus is 2300 MPa.
PP7 (b1) Propylene homopolymer with MFR 0.5g / 10 min, Mw / Mn 8.0, isotactic pentad fraction 0.967 (manufactured by Nippon Polypro Co., Ltd.) / Third stage = 35/33/32 (mass%), [η] of each stage is the first stage / second stage / third stage = 1.5 / 3.7 / 6.2), and the flexural modulus is 1700 MPa.
PP8 (b1) Propylene homopolymer with MFR 0.5g / 10min, Mw / Mn10.0, isotactic pentad fraction 0.967 (manufactured by Nippon Polypro Co., Ltd.) / Third stage = 35/33/32 (mass%), [η] of each stage is the first stage / second stage / third stage = 0.9 / 3.7 / 7.0), and the flexural modulus is 1500 MPa.
(3) Inorganic filler talc: specific surface area 44,000 cm ² / g, average particle size 1.6 μm, particle size 10 μm or more 0.5 mass%; MgO component 33.1 mass%, SiO ₂ component 62.5 % By mass, 4.4% by mass of other components.

[Example 1]
Crystalline polypropylene (PP1) with a MFR of 0.5 g / 10 min, highly crystalline polypropylene (PP5), a density of 0.91 g / cm ³ , a styrene content of 32% by mass, and a viscosity of 1.5 Pa · s according to the BMS0380 method. Using styrene / ethylene / butylene / styrene block copolymer (SEBS) Kraton G1651, blended in the proportions shown in Table 1, mixed with a mixer, melt-kneaded with a twin-screw extruder, and the extrusion temperature reached 200 ° C. The strand was extruded, cooled and granulated. The obtained pellets were evaluated by various evaluation methods. The results are shown in Table 1.

[Examples 2 and 3]
Evaluation was performed in the same manner as in Example 1 except that the ratio of PP1 and PP5 was changed to the ratio shown in Table 1. The results are shown in Table 1.

[Example 4]
Evaluation was performed in the same manner as in Example 1 except that PP2 was used as the component (a). The results are shown in Table 1.

[Example 5]
Evaluation was performed in the same manner as in Example 2 except that PP2 was used as the component (a). The results are shown in Table 1.

[Example 6]
Evaluation was performed in the same manner as in Example 2 except that the amount of the component (c) was 10 parts by weight. The results are shown in Table 1.

[Example 7]
Evaluation was performed in the same manner as in Example 6 except that the ratio of PP1 and PP5 was changed to the ratio shown in Table 1. The results are shown in Table 1.

[Example 8]
Evaluation was performed in the same manner as in Example 2 except that PP6 was used as the component (a). The results are shown in Table 1.

[Comparative Example 1]
Crystalline polypropylene (PP1) alone having an MFR of 0.5 g / 10 min was blended as shown in Table 2, pellets were obtained by the same method as in Example 1, and evaluated by various evaluation methods in the same manner as in Example 1. The results are shown in Table 2.

[Comparative Example 2]
Evaluation was performed in the same manner as in Example 2 except that the component (c) was not used. The results are shown in Table 2.

[Comparative Example 3]
Evaluation was performed in the same manner as in Example 2 except that the amount of the component (c) was 50 parts by weight. The results are shown in Table 2.

[Comparative Example 4]
Evaluation was performed in the same manner as in Example 2 except that PP3 was used as the component (a). The results are shown in Table 2.

[Comparative Example 5]
Evaluation was performed in the same manner as in Example 1 except that the amounts of the components (a) to (c) were changed to the ratios shown in Table 1. The results are shown in Table 2.

[Comparative Example 6]
Evaluation was performed in the same manner as in Example 1 except that the component (b) was not used. The results are shown in Table 2. The bending elastic modulus and heat resistance rigidity were extremely low.

[Comparative Example 7]
Evaluation was conducted in the same manner as in Comparative Example 6 except that PP3 was used as the component (a). The results are shown in Table 2.

[Comparative Example 8]
Evaluation was conducted in the same manner as in Example 6 except that PP4 was used as the component (a) and the component (b) was not used. The results are shown in Table 2.

[Comparative Example 9]
Evaluation was performed in the same manner as in Comparative Example 6 except that 10 parts by weight of talc was added. The results are shown in Table 1. Compared to Comparative Example 6, the flexural modulus and heat-resistant rigidity were improved, but the pinch-off strength was lowered, and the effect achieved with the composition of the present invention was not obtained.

[Comparative Example 10]
Evaluation was performed in the same manner as in Example 2 except that PP4 was used as the component (a). The results are shown in Table 2.

[Comparative Example 11]
Evaluation was performed in the same manner as in Example 8 except that PP7 was used as the component (b). The results are shown in Table 1.

[Comparative Example 12]
Evaluation was performed in the same manner as in Example 2 except that PP8 was used as the component (b). The results are shown in Table 1.

From the above results, since the composition of the present invention uses SEBS and a high crystalline polypropylene composition in a specific range in an amount ratio of MFR 2 g / 10 min or less in crystalline polypropylene resin, melting at 230 ° C. tension above 10 cN, anti mud - has also down, low density (0.93 g / cm ³ or less), high rigidity (or 1300 MPa), low-temperature impact (5 kJ / ^{m 2} or more), pinch-off strength retention (85% The above composition is obtained (see Examples 1 to 8).
In contrast to this, (1) crystalline polypropylene (MFR 0.5 / 10 min) alone, and high crystalline polypropylene and SEBS are not blended to obtain a draw-down resistance (see Comparative Example 1). 2) Even if an appropriate amount of high crystalline polypropylene (PP5) is blended with crystalline polypropylene (MFR 0.5 / 10 min, PP1), no drop down resistance can be obtained without SEBS (see Comparative Example 2).
In addition, (3) When an appropriate amount of high crystalline polypropylene (PP5) is blended with crystalline polypropylene (MFR 0.5 / 10 min, PP1) and SEBS is added in a large amount (50%), the flexural modulus, HDT, and pinch-off strength are remarkably increased. (Refer to Comparative Example 3) (4) Even when a suitable amount of high crystalline polypropylene (PP5) and SEBS are blended, if the MFR of the crystalline polypropylene is 2.5 / 10 min (PP3), The draw-down property is lowered and the low temperature impact is also lowered. (See Comparative Example 4). (5) When a large amount of high crystalline polypropylene (PP5) is blended with crystalline polypropylene (PP1) with an MFR of 0.5 g / 10 min and a large amount of styrene / butylene / styrene (SEBS) is blended, the pinch-off strength decreases. (See Comparative Example 5).
Moreover, if (6) component (b) is not used, a bending elastic modulus will fall significantly (refer comparative example 6), (7) SEBS is mix | blended with a suitable quantity for crystalline polypropylene (MFR2.5g / 10min). However, the melt tension is lowered, the drawdown resistance is lowered, and the flexural modulus is also lowered (see Comparative Example 7). (8) Even if an appropriate amount of SEBS is blended with crystalline polypropylene (MFR 6.0 g / 10 min), the melt tension is lowered, the drop-down resistance is lowered, the bending elastic modulus is lowered, and the pinch-off strength is also lowered. It can be seen (Comparative Example 8).
Furthermore, (9) When an appropriate amount of SEBS is blended with crystalline polypropylene (MFR 0.5 g / 10 min) and talc is blended, the melt tension and the flexural modulus are improved, but the density is increased and the pinch-off strength is greatly reduced ( Comparative Example 9). Further, (10) Even if a suitable amount of high crystalline polypropylene (PP5) and styrene / butylene / styrene (SEBS) is blended with crystalline polypropylene, if the crystalline polypropylene is PP4 with MFR 6.0 g / 10 min, It can be seen that the drop-down resistance is reduced (Comparative Example 10).
Furthermore, it can be seen that when the magnitude relationship between (11) Mw / Mn of component (a) and Mw / Mn of component (b) is reversed, the drawdown resistance is reduced (Comparative Example 11). Moreover, it turns out that drawdown-proof property falls when Mw / Mn of (12) component (b) is excessive (comparative example 12).

Claims (3)

1 to 40 parts by weight of the following component (c) is included with respect to 100 parts by weight of the polypropylene resin material consisting of 50 to 90% by weight of the following component (a) and 10 to 50% by weight of the following component (b). A polypropylene resin composition for extrusion molding.
Component (a): Crystalline propylene homopolymer (a1) having an Mw / Mn of 5 to 20, or a crystalline propylene ethylene block copolymer having the crystalline propylene homopolymer portion and the propylene ethylene copolymer portion (A2) with a melt flow rate (230 ° C. 21.18 N) of 2 g / 10 min or less and a flexural modulus of 900 to 1500 MPa Component (b): Mw / Mn of 1 to 9 and the crystallinity A propylene homopolymer (b1) smaller than Mw / Mn of the propylene homopolymer (a1), or a propylene ethylene block copolymer (b2) having the propylene homopolymer portion and the propylene ethylene copolymer portion, wherein the melt flow rate (230 21.18N) is 0.03 to 3 g / 10 min, and the flexural modulus is 1800 to 260. MPa ones component (c): a hydrogenated product of a styrene-conjugated diene block copolymer The propylene homopolymer of component (b) is obtained by homopolymerizing propylene in at least two stages, and among the polymer parts produced in each stage, the intrinsic viscosity of the polymer part having the highest molecular weight is [η] H, the highest molecular weight. The polypropylene for extrusion molding according to claim 1, wherein [η] H and [η] L satisfy the relational expression (1) when the intrinsic viscosity of the low polymer portion is [η] L. Resin composition.
3.0 ≦ [η] H− [η] L ≦ 6.5 (1)   A blow molded article obtained by molding the polypropylene resin composition for extrusion molding according to claim 1 or 2 with a blow molding machine.