JP5052491B2 - Polypropylene resin composition and blow molded article comprising the same - Google Patents

Description

  The present invention relates to a polypropylene resin composition and a blow molded article comprising the same, and more specifically, a polypropylene resin composition having low density, good draw-down resistance, high physical properties, and excellent pinch-off strength, and a blow resin comprising the same. It relates to a molded body.

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 used as a blow molding material for a long molded body, a problem that the thickness of the molded product becomes non-uniform due to draw-down 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.

Recently, it has been required to provide paintability and high impact resistance to the molded body, and ethylene / α-olefin copolymer rubber is added to the molding material, and rigidity heat resistance is imparted. Therefore, 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, Patent Document 5, and Patent Document 6). 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. Development of technology 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 JP 2007-231136 A

  In view of the above-mentioned conventional problems, an object of the present invention is a polypropylene resin composition having low density, good drawdown resistance, high physical properties, and excellent in pinch-off strength, and a blow molded article comprising the same, particularly a large blow molding To provide a body.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors are composed of a propylene homopolymer having a Mw / Mn of 5 to 20 and a propylene homopolymer having a Mw / Mn smaller than that of the propylene homopolymer. When specific ethylene polymer resin components are blended into polypropylene resin material and the content ratio of each component is optimized, the balance between melt tension and melt spreadability is maintained, and low density and good draw resistance The present invention has been completed by finding that a polypropylene resin composition having excellent properties and high physical properties and excellent pinch-off strength can be obtained, and that it can be easily molded even with a large and complex blow molded article.

That is, according to 1st invention of this invention, with respect to 100 mass parts of polypropylene resin materials which consist of the following component (A) 30-60 mass% and the following component (B) 40-70 mass%, the following A polypropylene resin composition for blow molding comprising 10 to 25 parts by mass of the component (C) is provided.
Component (A): a propylene homopolymer (A1) having an Mw / Mn of 5 to 20, or a propylene / ethylene block copolymer (A2) having the propylene homopolymer portion and the propylene / ethylene copolymer portion Component having a melt flow rate (230 ° C., 2.16 kg load) of 2 g / 10 min or less and a flexural modulus of 900 to 1500 MPa (B): Mw / Mn of 1 to 9 and propylene alone A propylene homopolymer (B1) smaller than Mw / Mn of the polymer (A1), or a propylene / ethylene block copolymer (B2) having a propylene homopolymer portion and a propylene / ethylene copolymer portion, and having a melt flow rate (230 ° C. , 2.16 kg load) is 0.03 to 3 g / 10 min, and the flexural modulus is 1800 to 26. Component intended 0 MPa (C): melt flow rate (190 ° C., 2.16 kg load), 0.1 to 0.5 g / 10 min, a density 0.953~0.970g / cm ^3, and flexural modulus , 900-1600 MPa ethylene polymer resin

According to the second invention of the present invention, the propylene homopolymer (B1) of component (B) or the propylene homopolymer part is obtained by homopolymerizing propylene in at least two stages, Of the polymer parts produced at each stage, when the intrinsic viscosity of the polymer part with the highest molecular weight is [η] H and the intrinsic viscosity [η] L of the polymer part with the lowest molecular weight is [η] H, There is provided a polypropylene resin composition for blow molding, wherein [η] L satisfies the relational expression (1).
3.0 ≦ [η] H− [η] L ≦ 6.5 (1)

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

  According to the present invention, a polypropylene resin composition having low density, good drawdown resistance, high physical properties, and excellent pinch-off strength, which is a performance necessary for obtaining a blow-molded product, particularly a large blow-molded product. You can get things. The polypropylene resin composition of the present invention is suitable for blow molding and has a desired shape and physical properties, such as a construction machine, agricultural machine roof, bonnet, trunk side trim, heat resistant duct, and bumper. Such as automobile members, pallets, construction materials (large panels), large foam blow materials, large sheets, foam members and the like can be easily manufactured.

1. Polypropylene resin composition The polypropylene resin composition of the present invention has the following components (A) 30 to 60% by mass and the following component (B) 40 to 70% by mass with respect to 100 parts by mass of the polypropylene resin material. The component (C) is contained in an amount of 10 to 25 parts by mass.
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 propylene homopolymer (A1) or a propylene / ethylene block polymer (A2) having the propylene homopolymer and a propylene / ethylene copolymer. In addition to this, the propylene homopolymer (A1) also includes a propylene-based copolymer in which a comonomer such as ethylene or 1-butene is copolymerized within a range that does not significantly impair the effects of the present invention. The amount of comonomer is less than 1% by mass.

In the propylene homopolymer (A1), the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) obtained by gel permeation chromatography (GPC) measurement is 5 to 20, preferably 6. -15, more preferably 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 is performed and the logarithmic value of the elution volume and molecular weight is approximated by a quadratic equation, and the molecular weight of the sample is 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 = −3.767, and 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 component (A) 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, so the melting point is 155 to 170 ° C. It is preferable.
Here, melting | fusing point means the peak of the endothermic curve obtained by a differential scanning calorimeter (DSC). For example, a DSC7 model manufactured by PerkinElmer Co., Ltd. is used, and a sample of about 10 mg is heated to 230 ° C. at a temperature increase rate of 20 ° C./min, held for 3 minutes, and then cooled at a rate of 5 ° C./min The temperature is lowered to 0 ° C., 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.

On the other hand, the propylene / ethylene block copolymer (A2) is preferably a copolymer of 40 to 99% by mass of a propylene homopolymer portion and 1 to 60% by mass of a propylene / ethylene copolymer portion. The propylene homopolymer portion of the propylene / ethylene block polymer (A2) has the same structure as the propylene homopolymer (A1).
The proportion of the propylene homopolymer portion relative to the entire propylene / ethylene block polymer (A2) is preferably from 60 to 95 mass%, more preferably from 70 to 93 mass%. The proportion of the propylene / ethylene copolymer portion is preferably 5 to 40% by mass, more preferably 7 to 30% by mass.

  The melt flow rate (230 ° C., 2.16 kg: hereinafter referred to as MFR) of the component (A) used in the present invention is 2 g / 10 minutes or less, preferably 1.5 g / 10 minutes or less, more preferably 0.1 to 0.5 g / 10 min. When MFR is too high, drawdown resistance will fall. Here, MFR is measured based on JIS K7210 (230 degreeC, 2.16kg load).

  The flexural modulus of the component (A) used in the present invention is 900 to 1500 MPa, preferably 1000 to 1500 MPa, and more preferably 1100 to 1500 MPa. If it is less than the lower limit, the rigidity is lowered, and if it exceeds the upper limit, the impact strength is lowered. Here, the flexural modulus is measured at 23 ° C. according to JIS-K7171.

(2) Component (B)
The component (B) is either a propylene homopolymer (B1) or a propylene / ethylene block copolymer (B2) having the propylene homopolymer and a propylene / ethylene copolymer.
In addition to the propylene homopolymer, the propylene homopolymer (B1) used in the present invention includes a propylene copolymer in which comonomers such as ethylene and 1-butene are copolymerized within a range that does not significantly impair the object of the present invention. The amount of comonomer is less than 1% by mass.

In the propylene homopolymer (B1), the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) obtained by the GPC measurement is 1 to 9, preferably 3 to 8, more preferably 4 ~ 7. When Mw / Mn is less than the lower limit, the drawdown 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 propylene homopolymer of the component (A), preferably 1 or less, more preferably 2 or more. It is small, more preferably 3 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 propylene homopolymer of component (A), the balance between the drawdown resistance and the pinch-off strength becomes insufficient.

  The MFR (230 ° C., 2.16 kg) of the component (B) used in the present invention is 0.03 to 3 g / 10 minutes, preferably 0.1 to 2 g / 10 minutes, more preferably 0.2 to 1 g. / 10 minutes. 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. MFR is measured by the method described above.

  The flexural modulus of the component (B) used in the present invention is 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 strength is lowered. Here, the flexural modulus is measured by the method described above.

  The component (B) used in the present invention has a 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, so the melting point is 155 to 170 ° C. Is preferable, and 157 to 169 ° C is more preferable. Here, the melting point is measured by the method described above.

The propylene homopolymer (B1) used in the present invention is obtained by homopolymerizing propylene in at least two stages, and among the polymer (polymer) parts produced in each stage, the highest molecular weight is obtained. When the intrinsic viscosity of the polymer (polymer) part is [η] H and the intrinsic viscosity [η] L of the polymer (polymer) part having the lowest molecular weight, [η] H and [η] L are expressed by the relational expression (1 ) Is preferably satisfied.
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. If 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 addition, when polymerizing in three or more stages, it is preferable that the portions of each polymer (polymer) are in an amount close to an equivalent amount, and a high molecular weight polymer (high molecular weight polymer) and a low molecular weight polymer (low molecular weight polymer). ) Is 0.5 to 1.5, more preferably 0.75 to 1.25. Within this range, good melt fluidity is obtained and kneading during granulation is also good.

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

The propylene homopolymer (B1) according to the present invention can be produced by polymerizing propylene in multiple stages in the presence of the following catalyst, but is not limited to this method.
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) in the present invention is characterized in that the difference in intrinsic viscosity between the highest molecular weight polymer (polymer) and the lowest molecular weight polymer (polymer) is relatively large. In determining the polymerization conditions for each polymerization step, the highest molecular weight polymer (polymer) is obtained in the absence of a chain transfer agent such as hydrogen to obtain the lowest molecular weight polymer (polymer). The stage is preferably carried out in the presence of sufficient chain transfer agent.

In the propylene homopolymer (B1) of the present invention, the relationship between the isotactic pentad fraction (P) and 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 measured by a method using 13C-NMR described in Macromolecules, 925-926 (1973), and the isotactic pentad fraction is an isotactic pentad fraction in a propylene polymer molecular chain. The tactic fraction. 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 the 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 partial polymerization step and a propylene / ethylene / random copolymer partial polymerization step.
In the propylene homopolymer partial 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 partial polymerization step and the propylene / ethylene random copolymer partial polymerization step is not particularly limited. The properties of the propylene homopolymer portion are determined by measuring the properties of the propylene homopolymer obtained by separately performing only the propylene homopolymer partial polymerization step.

  The proportion 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.

(3) Component (C)
The ethylene polymer resin used as the component (C) in the present invention is a low MFR, high density ethylene polymer resin.

  Component (C) controls the MFR and density of the entire ethylene polymer resin to control the drawdown resistance of the polypropylene resin composition of the present invention, the surface appearance of the extruded parison / molded body (such as rough surface) and physical properties. It has the characteristic of being expressed and maintained at a practically satisfactory level.

  The MFR (190 ° C., 2.16 kg) of the component (C) used in the present invention is 0.1 to 0.5 g / 10 minutes, preferably 0.1 to 0.4 g / 10 minutes, more preferably 0.00. 1 to 0.3 g / 10 min. If it is less than the lower limit, the surface appearance of the extruded parison or the molded product is deteriorated, and if it exceeds the upper limit, the drawdown resistance is lowered. Here, MFR is measured based on JIS K7210 (190 degreeC, 2.16kg load).

The density of the component (C) used in the present invention is 0.953 to 0.970 g / cm ³ , preferably 0.955 to 0.970 g / cm ³ , more preferably 0.960 to 0.968 g / cm ^3. It is. If it is less than the lower limit, the rigidity is lowered, and if it exceeds the upper limit, the impact strength is lowered. Here, the density is measured by an underwater substitution method in accordance with JIS-K7112.

The bending elastic modulus (Olsen bending elastic modulus) of the component (C) used in the present invention is 900 to 1600 MPa. 1100-1500 MPa is more preferable. If the pressure is less than 900 MPa, the rigidity is lowered, and if it exceeds 1600 MPa, the impact strength tends to be lowered. Here, the flexural modulus is measured at 23 ° C. according to JIS-K7106.

  130-138 degreeC is preferable and, as for melting | fusing point of the component (C) used in this invention, 134-137 degreeC is more preferable. If it is less than the lower limit, the rigidity tends to decrease, and if it exceeds the upper limit, the impact strength tends to decrease. Here, the melting point is measured by the method described above.

As for the melt tension (190 degreeC) of the component (C) used in this invention, 7-14g is preferable and 8-13g is more preferable. If it is less than 7 g, the draw-down resistance is lowered, and if it exceeds 14 g, the surface appearance of the extruded parison or molded product tends to deteriorate.
Here, the measurement of the melt tension is carried out using a Capillograph manufactured by Toyo Seiki Co., Ltd., and the resin is put into a cylinder having a diameter of 10 mm heated to a temperature of 190 ° C. The resin extruded from an orifice having a length of 8 mm is taken up at a speed of 4.0 m / min and measured.

The component (C) used in the present invention can be obtained by mainly polymerizing ethylene using various known catalysts such as a Ziegler catalyst, a Phillips catalyst, and a metallocene catalyst. For example, in general, transition metal compounds such as titanium and zirconium, Ziegler catalysts composed of magnesium compounds, Phillips catalysts typified by chromium oxide-based catalysts, and transition metal compounds such as zirconium, hafnium, and titanium are at least one cyclopenta. Polymerization is carried out using a metallocene catalyst having a dienyl group or a substituted cyclopentadienyl group as a polymerization catalyst.
In the polymerization, ethylene is polymerized alone, or one or more comonomers selected from ethylene and an α-olefin having 3 to 18 carbon atoms are copolymerized so as to have a predetermined density. Representative examples of the α-olefin to be copolymerized include propylene, 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene and the like.
The component (C) in the present invention can be used by mixing these ethylene homopolymers or ethylene / α-olefin copolymers alone or appropriately.

(4) 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 arbitrary component, for example, other polyolefins such as butene polymer resin, 4-methylpentene-1 polymer resin, thermoplastic resins such as polyamide and polyester, ethylene / α-olefin. Rubbers and elastomers such as copolymer rubber, conjugated diene copolymer rubber and styrene / conjugated diene copolymer rubber, inorganic fillers, antioxidants, UV absorbers, light stabilizers, foaming agents, lubricants, lubricants, Examples thereof include various additives such as a plasticizer, a thickener, an antistatic agent, a flame retardant, 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.

The foaming agent is effective for reducing the weight of a polypropylene resin composition and a blow molded article comprising the same, improving rigidity and dimensional characteristics, and the like. Specific examples include azodicarbonamide, benzenesulfonyl hydrazide, toluenesulfonyl hydrazide, barium azodicarboxylate, hydrazodicarbonamide, carbon dioxide gas, nitrogen gas, butane and the like.
As the antioxidant, for example, a phenol-based antioxidant or a phosphorus-based antioxidant can be used.
Of these, phenolic antioxidants are preferred, and specific examples thereof include tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate, 1,1,3-tris (2-methyl- 4-hydroxy-5-t-butylphenyl) butane, octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, pentaerythrityl-tetrakis [3- (3,5-di- t-butyl-4-hydroxyphenyl) propionate], 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, 3,9-bis [2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl] -2,4,8,10 tetraoxaspir [5,5] undecane can be mentioned 1,3,5-tris (4-t-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid.

(5) Compounding amount of components The compounding amounts of the components (A) to (C) are as follows. That is, 10-25 mass parts of components (C) are included with respect to 100 mass parts of polypropylene resin materials which consist of 30-60 mass% of components (A) and 40-70 mass% of components (B).
The amount of component (A) is preferably 35 to 55 mass%, more preferably 40 to 55 mass%, and the amount of component (B) is preferably 45 to 65 mass%, more preferably 45 to 55 mass%. 60% by mass. When the blending amount of the component (B) in the polypropylene resin material composed of the components (A) and (B) is less than the lower limit, the heat resistance rigidity, the extensibility during molding and the pinch-off strength of the polypropylene resin composition of the present invention are lowered. If the upper limit is exceeded, impact strength and the like tend to decrease.
The compounding amount of the component (C) is preferably 10 to 20 parts by mass, more preferably 10 to 15 parts by mass with respect to 100 parts by mass of the polypropylene resin material composed of the component (A) and the component (B). If the amount of the component (C) is too small, the drawdown resistance is lowered. On the other hand, if it is too much, the spreadability, heat resistance rigidity, and pinch-off strength at the time of molding are lowered. In addition, these components (A), component (B), and component (C) may be used in combination of two or more of each component as long as they are within the above-mentioned characteristics.
Moreover, since the compounding quantity of a component (D) changes with kinds, it cannot unconditionally specify, but if it is a foaming agent, it is 0 with respect to 100 mass parts of polypropylene resin materials which consist of a component (A) and a component (B). 0.01 to 10 parts by mass.
Furthermore, the compounding quantity of antioxidant can be 0.01-1 mass part with respect to 100 mass parts of polypropylene resin materials which consist of a component (A) and a component (B). If the amount is less than this amount, the heat aging resistance of the product is not sufficient. On the other hand, if the amount is excessive, not only is it uneconomical but also discoloration and bleeding problems occur.

2. Production of Polypropylene Resin Composition The polypropylene resin composition of the present invention contains the above components (A) to (C) and, if necessary, further contains other components (D), such as a high-speed mixer, It is generally obtained by heat-melt kneading using a conventional mixing kneader such as a Banbury mixer, continuous kneader, single or twin screw extruder, roll, Brabender plastograph and the like. At this time, a granulation method is usually employed.
As a result, the melt tension at 190 ° C. is 15 g or more, good draw-down resistance, melt ductility (50 m / min or more), low density (0.93 g / cm ³ or less), rigidity (1500 MPa or more) ), A deflection temperature under load (HDT) (120 ° C. or higher) and a pinch-off strength retention (85% or higher) are obtained.

  Since the polypropylene resin composition of the present invention has a good balance between melt tension and melt spreadability, it can be suitably used for extrusion molding. Examples of extrusion molding include blow (hollow) molding, sheet molding, and profile extrusion molding, and are particularly suitable for blow (hollow) molding and sheet molding.

3. Blow Molded Product The polypropylene resin composition of the present invention thus obtained is molded into a blow molded product by an ordinary blow molding machine. 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.
The large blow molded article is suitably used for parts and products such as pallets, automobile bumpers, construction machinery, agricultural machinery roofs, bonnets, engine covers, fenders, exterior panels and trunk side trims.
Further, the polypropylene resin composition of the present invention is also suitable for sheet molding (extrusion molding other than blow molding). For example, the polypropylene resin composition is molded by a normal sheet molding machine and is a large foam sheet, an interior member (deck board, Used for parts and products such as tonneau cover).

  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. Evaluation method (1) Density (unit: g / cm ³ ): Measured using the method described above.
(2) MFR (unit: g / 10 min): Measured using the method described above (230 ° C., 2.16 kg load, where component (C) = 190 ° C., 2.16 kg load).
(3) Mw / Mn: Measured using the method described above.
(4) Polymerization ratio: measured using the method described above.
(5) Intrinsic viscosity [η]: measured using the method described above.
(6) Isotactic pentad fraction (P): measured using the method described above.

(7) Melt tension (unit: g): measured using the method described above (190 ° C.). Use as an index of resistance to drawdown.
(8) Drawdown resistance: A panel with a length of 1.8m, a width of 0.9m, and a weight of 9kg is molded at 190 ° C using a DA-100 type large blow molding machine manufactured by Placo. Measure the lower thickness and upper thickness of the molded body. When the ratio of the upper wall thickness to the lower wall thickness of this molded body is 0.8 to 1.0, it is good, and those having a thickness of less than 0.8 or poorly formed or unmoldable are bad.
(9) Melt spreadability (unit: m / min): Using a Toyo Seiki Capillograph, put the resin in a cylinder with a diameter of 10 mm heated to 190 ° C., and push the molten resin at a pushing speed of 10 mm / min. A resin extruded from an orifice having a diameter of 2.095 mm and a length of 8 mm is taken out at a speed of 4.0 m to 200 m / min, and the speed at which the molten resin breaks is measured to obtain an index of parison extensibility.

(10) Flexural modulus (unit: MPa): measured using the method described above. (Polypropylene resin composition = JIS-K7171 compliant, component (C) = JIS-K7106 compliant)
(11) Deflection temperature under load (HDT, unit: ° C.): Measured under the condition of 0.45 MPa in accordance with JIS-K7191-2.
(12) Pinch-off strength (unit:%): bottom of a 500 cc round bottle having a bottom wall thickness of 1.0 mm, molded under molding conditions of a resin temperature of 200 ° C. using an IPB-10A small blow molding machine manufactured by IHI Using a test piece punched into a dumbbell shape so as to include a pinch-off portion, the breaking strength at a tensile speed of 10 mm / min is measured. The retention rate is calculated with the value measured using a test piece punched into a dumbbell shape not including the pinch-off portion as 100%. If this value is 85% or more, market practicality is good, and if it is less than 85%, it is judged as poor.

In the examples and comparative examples, the following resins were used.
2. Material (1) Component (A)
(A) -1: Propylene-polymerized with a Ziegler-based catalyst, having a propylene homopolymer portion of Mw / Mn 8.6, an MFR of the whole polymer of 0.5 g / 10 min, and a flexural modulus of 1200 MPa. Ethylene block copolymer (A) -2: Polymerized with a Ziegler catalyst, has a propylene homopolymer portion of Mw / Mn4.5, MFR of the whole polymer is 2.5 g / 10 min, and flexural modulus is 1700 MPa propylene / ethylene block copolymer (A) -3: polymerized with a Ziegler-based catalyst, having a propylene homopolymer portion of Mw / Mn 9.0, MFR of the whole polymer being 2.5 g / 10 min , Propylene / ethylene block copolymer (A) -4 having a flexural modulus of 1150 MPa: a propylene homopolymer polymerized with a Ziegler catalyst and having Mw / Mn 7.0 Has a minute, the entire polymer MFR of 0.5 g / 10 min, bending propylene-ethylene block copolymer elastic modulus is 1200MPa

(2) Component (B)
(B) -1: Polymerized with a Ziegler catalyst, the propylene homopolymer part is a three-stage polymerization product, each stage polymerization ratio is 35/33/32, and each [η] is 2.0 / 3 0.7 / 5.8, Mw / Mn 6.0, isotactic pentad fraction 0.967, MFR of the whole polymer 0.5 g / 10 min, and flexural modulus 2300 MPa. Propylene / ethylene block copolymer (B) -2: Polymerized with a Ziegler catalyst, the propylene homopolymer part is a three-stage polymer product, each stage polymerization ratio is 35/33/32, and each [η] is 1.5 / 3.7 / 6.2, Mw / Mn 8.0, isotactic pentad fraction 0.967, MFR of the whole polymer 0.5 g / 10 min, flexural elasticity The rate is 1700 MPa Propylene / ethylene block copolymer (B) -3: polymerized with a Ziegler catalyst, the propylene homopolymer part is a three-stage polymer product, each stage polymerization ratio is 35/33/32, and each [η ] 0.9 / 3.7 / 7.0, Mw / Mn 10.0, isotactic pentad fraction 0.967, and MFR of the whole polymer is 0.5 g / 10 min. Propylene / ethylene block copolymer with a flexural modulus of 1500 MPa

(3) Component (C)
(C) -1: an ethylene polymer resin having an MFR (190 ° C., 2.16 kg load) of 0.3 g / 10 min, a density of 0.965 g / cm ³ , and a flexural modulus (Olsen flexural modulus) of 1250 MPa. (C) -2: an ethylene polymer resin having an MFR (190 ° C., 2.16 kg load) of 0.3 g / 10 min, a density of 0.945 g / cm ³ , and a flexural modulus (Olsen flexural modulus) of 800 MPa.

[Example 1]
Component (A): MFR 0.5 g / 10 min propylene / ethylene block copolymer (A-1), Component (B): Propylene / ethylene block copolymer (B-1), Component (C): Ethylene heavy Table 1 together with 0.08 parts by mass of pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] using a coalesced resin (C-1) After mixing at a ratio and mixing with a mixer, the mixture was melt-kneaded with a twin screw extruder, the strand was extruded at an extrusion temperature of 200 ° C., cooled and granulated. The obtained pellets were evaluated by various evaluation methods. The results are shown in Table 1.

[Examples 2-3]
The ratio of A-1 and B-1 was changed to the ratio shown in Table 1, or the ratio of C-1 to A-1 and B-1 was changed, and evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

[Example 4]
Evaluation was conducted in the same manner as in Example 3 except that A-4 was used as the component (A). The results are shown in Table 1.

[Comparative Example 1]
Using A-1 alone as the component (A), pellets were obtained without blending the components (B) and (C), and evaluated by various evaluation methods. The results are shown in Table 2.

[Comparative Examples 2 and 3]
Evaluation was performed in the same manner as in Example 1 except that the ratio of A-1 and B-1 was changed to the ratio shown in Table 2 without using the component (C). The results are shown in Table 2.

[Comparative Example 4]
Evaluation was performed in the same manner as in Example 3 except that the component (B) was not used. The results are shown in Table 2.

[Comparative Example 5]
Evaluation was carried out in the same manner as in Example 1 except that the blending ratio of A-1 and B-1 was changed and the amount of C-1 was increased. The results are shown in Table 2.

[Comparative Example 6]
Evaluation was performed in the same manner as in Example 3 except that C-2 was used as the component (C). The results are shown in Table 2.

[Comparative Examples 7 and 8]
Evaluation was conducted in the same manner as in Example 3 except that A-2 or A-3 was used as the component (A). The results are shown in Table 2.

[Comparative Example 9]
Evaluation was conducted in the same manner as in Example 4 except that B-2 was used as the component (B). The results are shown in Table 2.

[Comparative Example 10]
Evaluation was conducted in the same manner as in Example 3 except that B-3 was used as the component (B). The results are shown in Table 2.

From the above results, the composition of the present invention has a specific range of a propylene / ethylene block copolymer having an MFR of 2 g / 10 min or less and a propylene / ethylene block copolymer and an ethylene polymer resin having a smaller Mw / Mn. Are used together in a quantity ratio of low density (0.90 to 0.91 g / cm ³ ), melt tension of 15 g or more, good draw-down resistance, melt ductility of 50 m / min or more, It can be seen that a polypropylene resin composition having a high rigidity (1500 MPa or more), a high HDT (120 ° C. or more), a high pinch-off strength (85% or more), and a good molded appearance is obtained (Examples) 1-3).

On the other hand, in the comparative example, any of the components (A), (B), and (C) does not satisfy the conditions of the present invention or the blending amount is deviated as described below, so that polypropylene having desired physical properties is obtained. A resin composition is not obtained.
1. Ingredient (A) (MFR 0.5 g / 10 min) alone does not provide resistance to drawdown. (See Comparative Example 1)
2. Even if an appropriate amount of component (B) (MFR 0.5 / 10 min) is blended with component (A) (MFR 0.5 g / 10 min), if component (C) is not blended, a drop-down resistance can be obtained. Absent. (See Comparative Example 2)
3. If component (A) (MFR 0.5 g / 10 min) is not blended with an appropriate amount of component (B) (MFR 0.5 / 10 min) and component (C) is not blended, the heat resistance rigidity is good, Drawdown property cannot be obtained. (See Comparative Example 3)
4). Even if only a suitable amount of component (C) is blended with component (A) (MFR 0.5 g / 10 min), the resistance to draw-down is good, but the heat-resistant rigidity cannot be obtained. (See Comparative Example 4)
5. When component (C) is added excessively to component (A) (MFR 0.5 g / 10 min) and component (B), the draw-down resistance is good, but the flexural modulus and pinch-off strength are reduced. (See Comparative Example 5)
6). Even if component (B) is added to component (A) (MFR 0.5 g / 10 min), component (C) is outside the characteristic range of the present invention (MFR 0.3 g / 10 min, density 0.945 g / cm ^3). ), The drag-down resistance and pinch-off strength can be maintained, but the rigidity decreases. (See Comparative Example 6)
7). Even if the component (B) and the component (C) are in appropriate amounts, the component (A) is outside the characteristic range of the present invention (Mw / Mn 4.5, MFR 2.5 g / 10 min; Mw / Mn 9.0, MFR 2.5 g / 10 minutes), the parison spreadability, the heat resistance rigidity and the pinch-off strength are good, but the draw-down resistance cannot be obtained. (See Comparative Examples 7 and 8).
8). Furthermore, when the magnitude relationship between Mw / Mn of component (A) and Mw / Mn of component (B) is reversed, the pinch-off strength decreases (Comparative Example 9).
9. On the other hand, if Mw / Mn of the component (B) is excessive, the pinch-off strength is lowered and the rigidity is also lowered (Comparative Example 10).

  The polypropylene resin composition of the present invention and the blow molded article comprising the polypropylene resin composition have low density, good draw-down resistance, high physical properties and high pinch-off strength, and thus are, for example, large blow molded articles having a complicated shape. It can be suitably used for machine parts, agricultural machine roofs, bonnets, trunk side trims, heat-resistant ducts, bumpers, and other automobile members, pallets, construction materials (large panels), large foam blowers, large sheets, foam members and the like.

Claims (3)

10 to 25 parts by mass of the following component (C) is included with respect to 100 parts by mass of the polypropylene resin material consisting of 30 to 60% by mass of the following component (A) and 40 to 70% by mass of the following component (B). A polypropylene resin composition for blow molding .
Component (A): a propylene homopolymer (A1) having an Mw / Mn of 5 to 20, or a propylene / ethylene block copolymer (A2) having the propylene homopolymer portion and the propylene / ethylene copolymer portion Component having a melt flow rate (230 ° C., 2.16 kg load) of 2 g / 10 min or less and a flexural modulus of 900 to 1500 MPa (B): Mw / Mn of 1 to 9 and propylene alone A propylene homopolymer (B1) smaller than Mw / Mn of the polymer (A1), or a propylene / ethylene block copolymer (B2) having a propylene homopolymer portion and a propylene / ethylene copolymer portion, and having a melt flow rate (230 ° C. , 2.16 kg load) is 0.03 to 3 g / 10 min, and the flexural modulus is 1800 to 26. Component intended 0 MPa (C): melt flow rate (190 ° C., 2.16 kg load), 0.1 to 0.5 g / 10 min, a density 0.953~0.970g / cm ^3, and flexural modulus , 900-1600 MPa ethylene polymer resin The propylene homopolymer (B1) or the propylene homopolymer part of the component (B) is obtained by homopolymerizing propylene in at least two stages, and among the polymer parts produced in each stage, the molecular weight When the intrinsic viscosity of the highest polymer part is [η] H and the intrinsic viscosity of the polymer part having the lowest molecular weight is [η] L, [η] H and [η] L satisfy the relational expression (1). The polypropylene resin composition for blow molding according to claim 1.
3.0 ≦ [η] H− [η] L ≦ 6.5 (1) A blow molded article obtained by molding the polypropylene resin composition for blow molding according to claim 1 or 2 with a blow molding machine.