JP2008063587A - Process for producing highly rigid polypropylene resin and blow molded product using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To develop a highly rigid polypropylene resin having good draw-down resistance, manufacturing large sized blow molded parts which are lightweight and excellent in rigidity, dimensional stability and heat resistance, and to provide a blow molded product made of the polypropylene resin, suitably used especially in large-sized parts for automobiles, for example, bumpers, bumper beams, seat backs, instrument panels and the like. <P>SOLUTION: This process for producing the highly rigid polypropylene resin comprises a multi-stage polymerization method in which propylene polymers having different intrinsic viscosity [η] respectively are produced in first and second stages using a stereoregular catalyst, and further a propylene-ethylene copolymer is produced in a third stage. A blow molded product made of the highly rigid polypropylene resin produced by the method is also provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a highly rigid polypropylene resin and a blow molded article using the same. More specifically, a method for producing a high-rigidity polypropylene resin with good draw-down resistance that can produce large blow parts that are lightweight and have excellent rigidity, dimensional stability, and heat resistance, and the high-rigidity polypropylene-based resin. In particular, the present invention relates to a blow molded article suitably used for bumpers such as automobile bumpers and bumper beams.

  Conventionally, polypropylene resins have been molded into products having a desired shape by various molding methods such as extrusion molding, injection molding, and blow molding as general-purpose resins. Among these molding methods, the blow molding method is advantageous in that the mold is inexpensive and simplification of the process by integral molding is possible. It has been actively used for molding. In this case, a polypropylene resin is often used as a material from the viewpoint of specific gravity, rigidity, dimensional stability, heat resistance, and the like.

However, in general polypropylene resins, the drawdown resistance or rigidity required for blow molding is not always satisfactory, and various improvements have been attempted so far.
For example, Patent Document 1 proposes a method of obtaining a polypropylene resin with improved drawdown properties by producing a propylene homopolymer and a propylene-ethylene copolymer at a specific intrinsic viscosity and composition ratio. However, such a polypropylene-based resin, on the other hand, has insufficient rigidity when formed into a molded product, and further improvements have been desired. Further, techniques such as improvement of rigidity by multistage polymerization and a nucleating agent (Patent Document 2) and improvement of drawdown resistance and rigidity by specific multistage polymerization and nucleating agent (Patent Document 3) are also disclosed.

  However, in these technologies, although rigidity and drawdown resistance are improved to some extent, when trying to mold a so-called large blow part of about 5 kg or more, the drawdown resistance is insufficient and it becomes impossible to mold. If the product thickness distribution is not uniform, there is a problem that a satisfactory product cannot be obtained. For this reason, when molding a large blow molded product of 5 kg or more, the fact is that the drawdown is eliminated by blending a polyethylene resin such as high-density polyethylene with the polypropylene resin. However, since the blending of high-density polyethylene significantly reduces the rigidity of the resin, an inorganic filler such as talc is actually added to this.

   In any case, the original properties of polypropylene resin are lost due to the blending of polyethylene resin and talc, and the pinch-off strength in blow molding is particularly low. At the same time, the appearance of a resin capable of forming a large blow-molded product with polypropylene itself is desired. This is a problem that must be solved not only from the technical aspect but also from the social situation of recycling of molded products.

Japanese Patent Publication No. 63-36609 Japanese Patent Publication No. 3-74264 Japanese Unexamined Patent Publication No. 63-213547

  The purpose of the present invention is to develop a high-rigidity polypropylene-based resin with good draw-down resistance that is capable of manufacturing a large blow part that is lightweight and has excellent rigidity, dimensional stability, and heat resistance in such a situation. In addition, an object of the present invention is to provide a blow molded article made of this polypropylene resin, particularly suitable for large parts for automobiles such as bumpers, bumper beams, seat backs, instrument panels and the like. is there.

  The inventors of the present invention have made extensive studies to develop a high-rigidity polypropylene-based resin having the above-mentioned preferable properties and a blow molded article comprising the same. As a result, it has been found that a polypropylene resin produced under specific conditions by three-stage polymerization of a propylene polymer and a propylene-ethylene copolymer can achieve the object. The present invention has been completed based on such findings.

That is, this invention provides the manufacturing method and blow molding of the following highly rigid polypropylene-type resins.
1. Intrinsic viscosity measured in decalin at 135 ° C by propylene polymerization with propylene polymer and propylene-ethylene copolymer using a stereoregular catalyst containing lactones in the first stage at 50-70 ° C. Propylene polymer having [η] of 0.5 to 3.5 deciliter / g is produced at a rate of 60 to 80% by weight of the total polymerization amount, and propylene is polymerized at 50 to 70 ° C. in the second stage. Propylene polymer having an intrinsic viscosity [η] measured in decalin at 5 ° C. of 3.5 to 5.5 deciliter / g is produced at a rate of 10 to 20% by weight of the total polymerization amount. Copolymerization of propylene and ethylene at 65 ° C., intrinsic viscosity [η] measured in decalin at 135 ° C. is 3.5 to 5.5 deciliter / g, and ethylene unit content is 40 to 75% by weight Propile of - the method of producing a high rigidity polypropylene resin, characterized in that the production of ethylene copolymers by 3-stage polymerization to produce a proportion of 8-15% by weight of the total polymerization amount.
2. The high-conductivity of 1 above, wherein the stereoregular catalyst comprises a transition metal halide, an organoaluminum compound, and a lactone, and contains 0.01 to 10 mol of lactone with respect to 1 mol of the transition metal halide. Manufacturing method of rigid polypropylene resin.
3. The method for producing a high-rigidity polypropylene resin according to 2 above, wherein the lactone is γ-lactone and / or ε-lactone.
4). A blow molded article made of a high-rigidity polypropylene-based resin produced by the above methods 1 to 3.
5. The above blow molded product used for bumpers for automobiles.

By the method of the present invention, it is possible to produce a high-rigidity polypropylene-based resin having good drawdown resistance and capable of producing a large-sized blow part that is lightweight and has excellent rigidity, dimensional stability, and heat resistance.
The blow molded article obtained from the highly rigid polypropylene resin of the present invention is particularly suitably used for large parts for automobiles, for example, bumpers such as bumpers and bumper beams, seat backs, instrument panels and the like.

As a method for producing the polypropylene resin of the present invention, a method of producing a propylene polymer and a propylene-ethylene copolymer by multistage polymerization is used.
In this multistage polymerization method, a stereoregular catalyst is used to produce propylene polymers having different intrinsic viscosities [η] in the first stage and the second stage, respectively, and in the third stage, a propylene-ethylene copolymer is produced. A method of generating is used.

  Examples of the stereoregular catalyst used in the multistage polymerization include a transition metal halide, an organoaluminum compound, and a lactone that is added to obtain a polymer having a wide molecular weight distribution with improved stereoregularity. Can be mentioned.

Here, as the transition metal halide, a halide of titanium is preferable, and titanium trichloride is particularly preferable. Examples of the titanium trichloride include those obtained by reducing titanium tetrachloride by various methods, and further by ball mill treatment and / or solvent washing (for example, washing with an inert solvent or an inert solvent containing a polar compound). Activated, titanium trichloride or titanium trichloride eutectic (eg, TiCl ₃ · 1/3 AlCl ₃ ) is further co-mixed with amines, ethers, esters, sulfur, halogen derivatives, organic or inorganic nitrogen or phosphorus compounds, etc. A pulverized product can be used. Also, a titanium halide supported on a magnesium-based carrier can be used.

Moreover, as an organoaluminum compound, general formula (I)
AIR _n X _3-n (I)
[Wherein, R represents an alkyl group having 1 to 10 carbon atoms, X represents a halogen atom, and n represents a number satisfying 0 <n ≦ 3. ]
The compound represented by these can be mentioned.
Specific examples of such organoaluminum compounds include dimethylaluminum chloride, diethylaluminum chloride, ethylaluminum sesquichloride, ethylaluminum dichloride, triethylaluminum and the like. These aluminum compounds may be used alone or in combination of two or more. Moreover, this organoaluminum compound is normally used in the ratio of 1-100 mol with respect to 1 mol of halides of the said transition metal.

Furthermore, examples of the lactone include, for example, the general formula (II)

[Wherein R ¹ and R ² each represent a hydrogen atom or a hydrocarbon group such as a saturated aliphatic, unsaturated aliphatic, alicyclic, or aromatic group having 20 or less carbon atoms, and they are the same or different from each other. M represents an integer of 2 to 8. ]
The thing represented by is mentioned.

  Examples of the lactones include γ-lactones such as γ-butyrolactone, γ-valerolactone, γ-caprolactone, γ-caprolactone, γ-laurolactone, γ-palmilactone, and γ-stearolactone, δ- Examples include valerolactone, δ-lactone such as δ-caprolactone, ε-lactone such as ε-caprolactone, β-lactone such as β-propiolactone and dimethylpropiolactone. Among these lactones, γ-lactone and ε-lactone are preferable, and γ-butyrolactone, γ-caprolactone and ε-caprolactone are particularly preferable. These lactones may be used alone or in combination of two or more. The lactones are generally used at a ratio of 0.01 to 10 moles with respect to 1 mole of the transition metal halide.

  In the multistage polymerization, in the first stage, propylene is polymerized at 50 to 70 ° C., and a propylene polymer having an intrinsic viscosity (135 ° C. in decalin) [η] of 0.5 to 3.5 deciliter / g is obtained. It is good to produce | generate in the ratio of 60 to 80 weight% of the total polymerization amount. When the intrinsic viscosity [η] of this propylene polymer is less than 0.5 deciliter / g, the impact strength of the resulting polypropylene resin is low, and when it exceeds 3.5 deciliter / g, the discharge rate during blow molding is low. May decrease. Furthermore, if the amount produced is less than 60% by weight, the rigidity of the resulting polypropylene resin is insufficient, and if it exceeds 80% by weight, the impact strength may be lowered.

  Next, in the second stage, propylene is polymerized at 50 to 70 ° C., and a propylene polymer having an intrinsic viscosity (135 ° C. in decalin) [η] of 3.5 to 5.5 deciliter / g is total polymerization amount. It is good to produce | generate in the ratio of 10 to 20 weight%. When the intrinsic viscosity [η] of this propylene polymer is less than 3.5 deciliter / g, the impact strength of the resulting polypropylene resin is low, and when it exceeds 5.5 deciliter / g, the discharge rate during blow molding decreases. There is a case. Moreover, if the production amount is less than 10% by weight, the rigidity of the obtained polypropylene resin is insufficient, and if it exceeds 20% by weight, the impact strength may be lowered.

  In the third stage, propylene and ethylene are copolymerized at 45 to 65 ° C., the intrinsic viscosity (135 ° C. in decalin) [η] is 3.5 to 5.5 deciliter / g, and ethylene units A propylene-ethylene copolymer having a content of 40 to 75% by weight is preferably produced at a rate of 8 to 15% by weight of the total polymerization amount. When the intrinsic viscosity [η] of this propylene-ethylene copolymer is less than 3.5 deciliter / g, the impact strength of the resulting polypropylene resin is low, and when it exceeds 5.5 deciliter / g, the discharge rate during blow molding May decrease. Moreover, when the production amount is less than 8% by weight, the impact strength of the obtained polypropylene resin is low, and when it exceeds 15% by weight, the rigidity may be lowered. Further, in the propylene-ethylene copolymer, when the ethylene unit content is less than 40% by weight, the impact strength of the obtained polypropylene resin is low, and when it exceeds 75% by weight, the rigidity may be lowered. The ethylene unit content can be determined by measuring an infrared absorption spectrum.

In addition, adjustment of the intrinsic viscosity [η] of the polymer in each step can be performed by appropriately changing the concentration of a molecular weight regulator such as hydrogen. The pressure in the polymerization reaction is usually selected in the range of normal pressure to 30 kg / cm ² G, preferably 1 to 15 kg / cm ² G in each stage.

Furthermore, as a polymerization format, for example, a method of continuously using three or more polymerization tanks, a method of batch-wise using one or more polymerization tanks, and further, these continuous methods and batch-type A method performed in combination with a method can be applied. Moreover, there is no restriction | limiting in particular about the polymerization method, For example, any methods, such as suspension polymerization, solution polymerization, and gas phase polymerization, are employable.
When a solvent is used, examples of the solvent include aliphatic hydrocarbons such as heptane and hexane, alicyclic hydrocarbons such as cyclohexane, and aromatic hydrocarbons such as benzene and toluene. These solvents may be used alone or in combination of two or more.
The polypropylene resin of the present invention thus obtained has good drawdown resistance, is lightweight, and can provide a large blow part having excellent rigidity, dimensional stability, and heat resistance.

  The polypropylene resin produced by the method of the present invention has a melt index [MI] measured at a temperature of 230 ° C. and a load of 2,160 g according to JIS K-7210 of 0.1 to 1.2 g / 10 min. It is preferable to be in the range. When this MI is less than 0.1 g / 10 min, the discharge amount during blow molding is remarkably reduced, and the productivity is deteriorated. On the other hand, if it exceeds 1.2 g / 10 minutes, large blow molding becomes impossible. A more preferable range of MI is 0.2 to 1.0 gram / 10 minutes from the viewpoint of moldability.

Further, in the polypropylene resin, the relationship between the elongation viscosity [Y (Pas)] and the MI is preferably expressed by the formula 2.0 × 10 ⁵ × MI ^−0.68 ≦ Y ≦ 8.0 × 10 ⁵ × MI ^−0.68.
More preferably, 2.3 × 10 ⁵ × MI ^−0.68 ≦ Y ≦ 4.8 × 10 ⁵ × MI ^−0.68
It satisfies. When Y is less than 2.0 × 10 ⁵ × MI ^−0.68 , the parison drawdown during blow molding is severe, and blow molding of large blow molded products of 5 kg or more becomes difficult. On the other hand, when Y exceeds 8.0 × 10 ⁵ × MI ^−0.68 , the extrusion characteristics deteriorate and the appearance of the molded product is inferior.
The elongational viscosity [Y (Pas)] was measured by using a stretching rheometer (for example, manufactured by Iwamoto Seisakusho Co., Ltd.) and standing a rod-shaped sample having a diameter of 3 mm and a length of 20 cm in silicone oil at 175 ° C. for 15 minutes It is a value measured under conditions of a temperature of 175 ° C., a strain rate of 0.05 sec ⁻¹ , and a strain of 2.0.

The blow-molded product of the present invention comprises various additives as desired, such as soft elastomers, modified polyolefins, antioxidants, heat stabilizers, weather stabilizers, inorganic or organic fillers, and nucleating agents. It is obtained by blending an agent, an antistatic agent, a chlorine scavenger, a slip agent, a flame retardant, a colorant and the like, and blow molding. There is no restriction | limiting in particular about the blow molding method, The method conventionally used in the blow molding of polypropylene resin can be used.
The blow molded article of the present invention is lighter in weight and has rigidity, dimensional stability, and heat resistance compared to a blow molded article obtained by blow molding polypropylene that contains a large amount of inorganic fillers such as talc that are generally used in the past. In particular, it is suitably used for bumpers such as automobile bumpers and bumper beams.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
The melt index [MI] and elongational viscosity [Y] of the polypropylene resin are determined according to the method described in the specification, the ethylene unit content is measured by infrared absorption spectrum, the tensile elastic modulus is JIS K7113, the Izod impact value. (−20 ° C.) was determined according to JIS K7110.
In addition, the intrinsic viscosity [η] of the polymer in each stage is a value measured in decalin at 135 ° C.

Example 1
An autoclave with a stirrer having an internal volume of 10 liters was charged with 4 liters of n-heptane, 5.7 mmol of diethylaluminum chloride, 0.7 g of titanium trichloride and 0.2 ml of ε-caprolactone.
Next, while maintaining the liquidus temperature at 60 ° C., the above-described propylene is continuously added so that the hydrogen and the reaction pressure measured so that the produced propylene polymer has a predetermined intrinsic viscosity and the reaction pressure is 9 kg / cm ² G. The first stage polymerization was carried out with stirring for 90 minutes. Thereafter, unreacted propylene was removed, and while maintaining the temperature at 60 ° C., hydrogen and propylene weighed were continuously supplied so that the reaction pressure became 7 kg / cm ² G, and the second stage for 40 minutes. Was polymerized.
Further, while maintaining the temperature at 57 ° C., a mixture of propylene and ethylene and metered hydrogen were continuously supplied so that the reaction pressure was 5 kg / cm ² G, and the third stage polymerization was performed for 30 minutes. Went.
After adding n-butanol to the polymerization product and stirring at 65 ° C. for 1 hour to decompose the catalyst, a white powdery polypropylene resin was obtained through the steps of separation, washing and drying.
Table 1 shows the intrinsic viscosity [η] and polymerization amount of the polymer obtained in each stage. The physical properties of the polypropylene resin are shown in Table 2.

Example 2
In Example 1, polymerization was performed in the same manner as in Example 1 except that the intrinsic viscosity [η] and the polymerization amount of the polymer in each stage were changed as shown in Table 1. The results are shown in Table 2.

Example 3
In Example 1, polymerization was performed in the same manner as in Example 1 except that the intrinsic viscosity [η] and the polymerization amount of the polymer in each stage were changed as shown in Table 1. The results are shown in Table 2.

Example 4
To the polymer obtained in Example 1, 0.1% by weight of methylenebis (2,4-di-tert-butylphenol) acid phosphate sodium salt was added as a nucleating agent to obtain a polypropylene resin. The physical properties of this product are shown in Table 2.

Comparative Examples 1 and 2
To an autoclave with a stirrer having an internal volume of 10 liters, 5 liters of dehydrated n-hexane was added, and 1.0 g of diethylaluminum chloride and 0.3 g of titanium trichloride were added.
Propylene is continuously supplied to the autoclave so that the liquid phase temperature is maintained at 65 ° C. and hydrogen and the reaction pressure are measured so that the produced propylene polymer has a predetermined intrinsic viscosity and the reaction pressure is 9 kg / cm ² G. Then, the first polymerization was carried out with stirring for 90 minutes. Thereafter, unreacted propylene was removed, and the liquidus temperature was lowered to 50 ° C. Next, since the temperature was maintained at 50 ° C. and the pressure was 9 kg / cm ² G, weighed hydrogen and propylene were continuously supplied, and the second stage polymerization was performed for 40 minutes.
Further, a propylene-ethylene mixture and metered hydrogen were supplied while maintaining the temperature at 50 ° C., and the third stage polymerization was performed for 30 minutes. Subsequently, unreacted gas was removed, 50 ml of n-butanol was added to the polymerization product, and the mixture was stirred at 65 ° C. for 1 hour to perform catalytic decomposition. Thereafter, a white powder polymer was obtained through a separation step, a washing step, and a drying step. Polymerization was carried out by changing the intrinsic viscosity [η] and polymerization amount of the polymer obtained in each polymerization stage as shown in Table 1. The physical properties of the polypropylene resin are shown in Table 2.

Comparative Example 3
In Example 1, polymerization was carried out in the same manner as in Example 1 except that ε-caprolactone was not added as a catalyst component. The intrinsic viscosity [η] and polymerization amount of the polymer at each stage are shown in Table 1, and the physical properties of the polypropylene resin are shown in Table 2.

Comparative Example 4
In Example 1, polymerization was performed in the same manner as in Example 1 except that the intrinsic viscosity [η] and the polymerization amount of the polymer in each stage were changed as shown in Table 1. The results are shown in Table 2.

Comparative Example 5
As the two-stage polymerization, the amount of polymerization in the first stage was increased and the polymerization was carried out according to Example 1. The intrinsic viscosity [η] and polymerization amount of the polymer at each stage are shown in Table 1, and the physical properties of the polypropylene resin are shown in Table 2.

Comparative Example 6
After adding a predetermined antioxidant to the mixture having the following composition, the mixture was kneaded at a set temperature of 200 ° C. and a screw rotation number of 800 using a different-direction biaxial kneader (manufactured by Kobe Steel, 2FCM). . At this time, the temperature of the melt was 250 ° C. After forming a strand with an extruder, it was granulated with a pelletizer to produce a composite material for a bumper beam, and its physical properties were measured. The results are shown in Table 2.
Polypropylene (ethylene content; 5 wt%, MI; 0.9 g / 10 min) 70 wt%
High density polyethylene (HLMI: 3.8 g / 10 min) 20% by weight
Talc 10% by weight
Here, HLMI represents MI measured under conditions of a temperature of 190 ° C. and a load of 21.6 kg.

Examples 5-8, Comparative Examples 7-12
Bumper beams for automobiles (1) were used under the molding conditions and temperature conditions shown below, using polypropylene resins obtained by scaling up according to the conditions of Examples 1 to 4 and Comparative Examples 1 to 6. , 400 × 100 × 100 mm, weight 5 kg) and truck bumper (2,100 × 400 × 70 mm, weight 7.2 kg). However, the bumper for trucks was molded only for Example 8.

〔Molding condition〕
Molding machine: 90mmφ
Screw: 90mmφ
Die: 100mmφ
Accumulator: 15 liters (car bumper beam)
25 liters (truck bumper)
Clamping pressure: 60ton
Screw rotation speed: 40rpm
Motor load: 115A

(Temperature conditions)
Cylinder No. 1: 230 ° C
No. 2: 210 ° C
No. 3: 190 ° C
No. 4: 190 ° C
Crosshead No. 1: 190 ° C
No. 2: 190 ° C
No. 3: 190 ° C
Dice No. 1: 190 ° C
No. 2: 190 ° C
Molding cycle: 200 sec
Mold temperature: 28 ℃
Resin temperature: 225 ° C

(1) Formability, (2) Thickness distribution, Appearance, (3) Product rigidity, (4) Discharge amount, (5) Pinch-off strength, and (6) Impact resistance for automotive bumper beams and truck bumpers A comprehensive evaluation was conducted. The results are shown in Tables 3-5. However, the results in Table 3 are values for Example 8, and Tables 4 and 5 are obtained for the formation of bumper beams for automobiles.
In addition, the measurement of each item followed the following.

(1) Formability Necessary parison length / parison heavy object [bumper beam: 1,900 mm / 10 kg, bumper: 2,600 mm / 15 kg] is injected from the accumulator, and the parison length is 5 seconds until the mold is tightened. change;
L / Lo <1.10 ◎ Good 1.10 ≦ L / Lo ≦ 1.15 ○ Slightly good L / Lo> 1.15 × Poor
Lo: Parison chief at the end of injection
L: Parison length 5 seconds after the end of injection

(2) Thickness distribution Thickness measurement of each cross section: Thickness fluctuation 10% or less ◎ Good
Thickness variation greater than 10% and less than 20% ○ Slightly good
Greater than 20% wall thickness variation × Defect

(3) Product rigidity (climbing rigidity, 100kg)
Compare deformation with steel
○; ≦ 3mm (equal to or less than steel)
×;> 3 mm (larger than steel)

(4) Discharge performance The discharge amount per hour was measured; it was shown by comparison with the case of using the composite material of Comparative Example 6 by a blow 90 mmφ extruder.
◎; superior to composite materials
○: Almost equivalent to composite material

(5) Pinch-off strength In the blow-molded product, only the inside of the parison is fused at the time of mold clamping to form a fused portion called a pinch-off portion. Since this pinch-off portion is likely to be a starting point of breakage, it is necessary to improve its fusion property particularly in structural parts and strength parts. Therefore, the fusion strength of the pinch-off part was evaluated by the following method.
Using the resin obtained in each of Example 4 and Comparative Example 6, a bottle having a predetermined shape was formed by blow molding, and a strip-shaped test piece having a width of 20 mm was cut out from the bottom so as to include a pinch-off portion in the width direction. . Cutouts (notch blades; R = 2.0) were made at both ends of the pinch-off part of the obtained test piece so that the width of the pinch-off part was 10 mm.
This test piece was tested at a tensile speed of 50 mm / min using a tensile tester (INSTRON 1125, manufactured by INSTRON, USA).
The yield strength and breaking energy obtained were used as indicators of pinch-off strength. That is, the larger these values, the better the fusing property. The yield strength is indicated by the value of the maximum stress in the stress-strain curve, and the breaking energy is the value of [(stress) × Δ (strain)] in the stress-strain curve, and the strain value ranges from 0 to the breaking point. It is represented by a value obtained by integrating between the strain values at, and can be simply represented by the area between the obtained stress-strain curve and the horizontal axis.

(6) Impact resistance About the bumper beam obtained by blow-molding using the resin obtained in each of Example 4 and Comparative Example 6, the Federal Motor Vehicle Safety Standards (abbreviated as FMVSS) PART The pendulum test (Pendulum test) based on 581 was performed. That is, a bumper beam was attached to a bogie with a weight of 1000 kg, and an impact ridge with a weight of 1000 kg was collided at a speed of 5 mph / hour (about 8 km / hour) to obtain a relationship between the generated load and the amount of deformation. The collision point was the central part of the bumper beam. The test temperature was set to a high temperature (50 ° C.), a normal temperature (23 ° C.), and a low temperature (−10 ° C., −30 ° C.) in consideration of mounting on an actual vehicle. The evaluation was performed based on the maximum deformation amount and the presence or absence of cracks.

The comprehensive evaluation in Table 4 also considers the results of pinch-off strength and impact resistance shown in Table 5.
Table 5 shows that Example 8 has a fusion strength that is about 1.7 times the yield strength and about 10 times the breaking energy compared to Comparative Example 12. In the pendulum test, the excellent impact resistance of Example 8 is considered to be due to a significant improvement in the fusion strength of the pinch-off part.

Claims (5)

  Intrinsic viscosity measured in decalin at 135 ° C by propylene polymerization with propylene polymer and propylene-ethylene copolymer using a stereoregular catalyst containing lactones in the first stage at 50-70 ° C. Propylene polymer having [η] of 0.5 to 3.5 deciliter / g is produced at a rate of 60 to 80% by weight of the total polymerization amount, and propylene is polymerized at 50 to 70 ° C. in the second stage. Propylene polymer having an intrinsic viscosity [η] measured in decalin at 5 ° C. of 3.5 to 5.5 deciliter / g is produced at a rate of 10 to 20% by weight of the total polymerization amount. Copolymerization of propylene and ethylene at 65 ° C., intrinsic viscosity [η] measured in decalin at 135 ° C. is 3.5 to 5.5 deciliter / g, and ethylene unit content is 40 to 75% by weight Propile of - the method of producing a high rigidity polypropylene resin, characterized in that the production of ethylene copolymers by 3-stage polymerization to produce a proportion of 8-15% by weight of the total polymerization amount.   The stereoregular catalyst comprises a transition metal halide, an organoaluminum compound, and a lactone, and contains 0.01 to 10 moles of lactone with respect to 1 mole of transition metal halide. The manufacturing method of the highly rigid polypropylene resin of description.   The method for producing a high-rigidity polypropylene resin according to claim 2, wherein the lactone is γ-lactone and / or ε-lactone.   A blow molded article made of a high-rigidity polypropylene resin produced by the method according to claim 1.   The blow molded product according to claim 4, which is used for bumpers for automobiles.