JPH04126755A - Resin composition for blow-molded bumper beam - Google Patents

Abstract

PURPOSE:To obtain the title inexpensive composition excellent in drawdown resistance, pinch-off characteristics, etc., by incorporating a specific propylene- ethylene copolymer or its blend with a high-density polyethylene with each specified amount of a rubbery elastomer and talc. CONSTITUTION:The objective composition can be obtained by incorporating (A) 40-93wt.% of a propylene-ethylene copolymer <=1g/10min in melt index, 1-15wt.% in ethylene unit content and >=92% in the isotactic pentad fraction of the propylene homopolymerized domain with (B) 2-15wt.% of a rubbery elastomer 3X10<4>-1X10<6> poise in the complex viscosity at a frequency of 0.01 Rad/sec and (C) 5-30wt.% of talc <=5mum in mean particle size and 3-20 in mean aspect ratio. Where appropriate, part of the component A, i.e., <=30wt.% of the total amount of the component. A may be replaced by a high density polyethylene <=0.1g/10min in melt index and 2-20 in the parameter A defined by the formula.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a novel resin composition for blow-molded bumper beams, and more particularly, a novel resin composition for blow-molded bumper beams. The present invention also relates to a resin composition for blow-molded bumper beams that has excellent recyclability and complies with the US 5m1le/hr pendulum standard.

BACKGROUND OF THE INVENTION Conventionally, bumper beams for automobiles have been made of metal, but in recent years, there has been a shift to plastics for the purpose of weight reduction, rust prevention, and formability.

Examples of plastic bumper beams include (1)
High-density polyethylene, (2) polypropylene, (3) Xenoy (manufactured by GE, trade name, polybutylene terephthalate/polycarbonate alloy), (
4) Those made by blow molding a talc-containing polypropylene composite material, (5) Stamped Root (polypropylene-impregnated glass fiber mat), and (6) SMC are known.

On the other hand, recently there has been an increasing demand for low-cost bumper beams that meet the strict standards of the US 5m1le/hr pendulum test. However, the above (1
Blow molded high-density polyethylene () and polypropylene (2) are low cost, but have the disadvantage of insufficient strength;
Blow-molded materials have the drawbacks of high material cost and poor recyclability.

In addition, although the blow-molded talc-containing polypropylene composite material (4) is low cost, it has the drawback of low low-temperature impact strength, and the methane bubble sheet (5) and SMC (6) are It is inevitable that the costs will be high.

Problems to be Solved by the Invention The present invention overcomes the drawbacks of conventional plastic molding materials for bumper beams, and achieves low cost, blow-down properties such as drawdown resistance, pinch-off properties, deep drawability, etc., and recyclability. In addition to being excellent in quality, the US 5m1le/
This was done with the purpose of providing a plastic molding material for bumper beams that complies with the HR pendulum standards.

Means for Solving the Problems The present inventors have conducted extensive research to develop a plastic blow molding material for bumper beams having the above-mentioned favorable properties. It has been discovered that a resin composition containing a specific rubber-like elastic material and talc in predetermined proportions in a mixture with density polyethylene is suitable for the purpose, and based on this knowledge, the present invention has been developed. I was able to complete it.

That is, the present invention provides (a) a melt index of 1.0;
g/10 min or less, a propylene-ethylene copolymer with an ethylene unit content of 1 to 15% by weight and an isotactic pentad fraction of 92% or more in the propylene homopolymerization part from 40 to
93% by weight, and (b) the frequency is 0.01 Rad/sec.
2 to 15% by weight of a rubber-like elastic body with a complex viscosity of 3X 10' to 1X105 voids, and (c) an average particle size of 5μ
Talc 5-30 m or less and average aspect ratio 3-20
% by weight, and a part of its (a) component (a') has a melt index of 0.1 g/10 minutes or less, and the formula % formula % (210 and 2. are the values at a constant strain rate elongational viscosity of 10 sec and 59 sec, respectively, at a measurement temperature of 150° C. and a strain rate of 0.05 sec-'), and the parameter A is in the range of 2 to 20. The object of the present invention is to provide a resin composition for a blow-molded bumper beam, in which the resin composition is replaced with not more than 30% by weight based on the total amount of .

The present invention will be explained in detail below.

In the composition of the present invention, the propylene-ethylene copolymer used as component (a) has a melt index of 1.09/10 min or less, preferably 0.0 g/lO min or less, more preferably 0.6 g/10 min. It is necessary that the melt index is 1.0g/10 or less.
If it exceeds 10 minutes, drawdown resistance, deep drawability, and low-temperature impact strength will decrease.

Further, the isotactic pentad fraction of the propylene homopolymer portion of the propylene-ethylene copolymer needs to be 92% or more, preferably 94% or more, and more preferably 96% or more. If the isotactic pentad fraction is less than 92%, the rigidity is insufficient and the amount of deformation during the pendulum test is large, so that the object of the present invention cannot be fully achieved. The isotactic pentad fraction in the present invention is defined by A. Zambe.
[Macromolecules (Mac
romolecules) J Volume 8,! 925 pages (
13C-NMR according to the method published in 1973).
It is the isotactic fraction of pentad units in a polypropylene molecular chain, that is, the fraction of propylene monomer units in which five consecutive propylene monomer units are men-bonded. However, regarding peak assignment, [Macromolecules (Macro6
1ecules) J Volume 8, Page 687 (1975
This was done based on the correction board of the above-mentioned document described in 2010). Specifically, the number of units is determined by the intensity fraction of the mmmm peak among the total absorption peaks in the methyl carbon region of the 13C-NltR spectrum. The value of the isotactic pentad fraction in the present invention is the value of the crystalline polymer as it is, and is not the value of the polymer after being subjected to treatments such as extraction and fractionation.

Furthermore, the content of ethylene units in the propylene-ethylene copolymer is 1 to 15% by weight, preferably 2 to 1% by weight.
It is necessary that the amount is 0% by weight, more preferably in the range of 3 to 7% by weight. If the content is less than 1% by weight, the low-temperature impact strength will be insufficient, and if it exceeds 15% by weight, the rigidity will decrease and the amount of deformation during the pendulum test will tend to increase.

In the composition of the present invention, the propylene-ethylene copolymer as the component (a) may be used alone or in combination of two or more, and the propylene-ethylene copolymer as the component (a) may be used in combination without impairing the object of the present invention. A propylene homopolymer may also be used in combination within a certain range. Further, in some cases, a portion of the component (a) may be added in an amount not exceeding 30% by weight, preferably 3% by weight, based on the total amount of the composition.
(in an amount of ~20% by weight, more preferably 3-15% by weight)
Component a'), ie high density polyethylene, may be substituted.

If the amount of component (a') exceeds 30% by weight, pinch-off strength, high temperature rigidity and dimensional accuracy will decrease. In addition, when high-density polyethylene as component (a') is not used, a propylene-ethylene copolymer as component (a) with a melt index of 5 g/10 minutes or less may be used. desirable.

The high density polyethylene of component (a') has a melt index of 0-1 g/10 minutes or less, preferably 0.07 g
/10 minutes or less, more preferably 0.04g/10 minutes or less. When the melt index exceeds 0.19/10 minutes, there is a tendency for drawdown resistance, deep drawability, and low-temperature impact strength to decrease.

Furthermore, the high-density polyethylene of the component (a') is A
-Zso/Zr.

(In the formula (7) Z, and Zso are the measurement temperature of 150°C
The parameter A defined by the constant strain rate elongational viscosity at 10 sec and 50 sec at a strain rate of 0.05 sec-' is 2 to 20, preferably 3 to 1.
It needs to be in the range of 0, more preferably 4 to 8. If the value of A is less than 2, the formability such as drawdown resistance and deep drawability will be insufficient, and if it exceeds 20, the pinch-off strength and extrusion properties will decrease.

In the composition of the present invention, the component (b) has a complex viscosity of 3X10 at a frequency of 0.0IRad/sec.
'~lX10' poise, preferably 6X10'~7x1
A rubber-like elastomer having a poise of 0.04 to 4.04 poise is used, preferably in the range of 9X1O' to 4X10' poise. If this complex viscosity is less than 3XlO'poise, drawdown resistance, deep drawability, and low-temperature impact strength are insufficient;
If the poise is exceeded, dispersion becomes insufficient and a thickening effect cannot be obtained, resulting in a decrease in drawdown resistance, as well as a tendency for deep drawability and low-temperature impact strength to decrease.

The rubber-like elastic body of component (b) is not particularly limited as long as it satisfies the above conditions, but EPR is preferred.

In the composition of the present invention, the talc used as component (c) has an average particle diameter of 5 μm or less and an average aspect ratio of 3 to 20, preferably 7 to 20, more preferably 10 to 20. is necessary. When the average particle size exceeds 5 μm, deep drawability, rigidity, low-temperature impact strength, and pinch-off strength tend to be insufficient, and when the average aspect ratio is less than 3, the rigidity is poor and the amount of deformation during the pendulum test is low. If it exceeds 20, the pinch-off strength and low-temperature impact strength will decrease.

The content of component (a) in the composition of the present invention is 40 to 93
% by weight, preferably 50 to 90% by weight, more preferably 60 to 85% by weight, and as described above, if desired, a portion thereof may be added in an amount not exceeding 30% by weight based on the total amount of the composition. It can be replaced by component (a') in an amount of preferably 3 to 20% by weight, more preferably 3 to 15% by weight. In addition, the content of component (b) is 2 to 15% by weight,
It is preferably in the range of 2 to 12% by weight, more preferably 2 to 8% by weight. If the content of component (b) is less than 2% by weight, the low-temperature impact strength will be insufficient, and if it exceeds 15% by weight, the pinch-off strength will decrease and the amount of deformation during the pendulum test will increase.

Furthermore, the content of component (c) needs to be in the range of 5 to 30% by weight, preferably 5 to 25% by weight, and more preferably 5 to 20% by weight. If the content of component (c) is less than 5% by weight, the rigidity and dimensional accuracy will be poor, and the amount of deformation during the pendulum test will be large, making it impossible to fully achieve the object of the present invention. If the content exceeds 30% by weight, the pinch-off strength will be poor. , deep drawability and impact strength are reduced.

The composition of the present invention may optionally contain other thermoplastic resins, such as maleic anhydride-modified polyolefins and acrylic acid-modified polyolefins, and inorganic fillers other than talc, as long as the required physical properties are not impaired. Calcium carbonate, mica, glass fiber, etc. and various additives,
For example, antioxidants, ultraviolet absorbers, heat stabilizers, lubricants, flame retardants, colorants, etc. may be included.

The composition of the present invention includes, for example, component (a), component (a'), (
Component b), component (C), and inorganic fillers and various additives used as desired are melt-kneaded using a -shaft kneader, twin-shaft kneader, multi-shaft kneader, Banbury mixer, etc. It can be prepared by At this time, there are no particular restrictions on the melting mixing conditions, but Banbury mixer
When using a kneading machine other than the above, the resin used is of a high viscosity type, so the resin is likely to deteriorate due to shear heat generation during kneading, and the drawdown resistance is likely to decrease. A temperature of 250°C (250°C) is desirable, and for that purpose the kneading temperature should be 190-230°C
It is advantageous to keep the resin pressure within the cylinder as low as possible (preset temperature).

A desired bumper beam can be produced by blow molding the resin composition obtained in this manner according to a known method.

Effects of the Invention The resin composition for blow-molded bumper beams of the present invention is composed of a specific propylene-ethylene copolymer or a mixture thereof with high-density polyethylene, a rubber-like elastic body, and talc, and is low-cost. and US 5m1le/hr
In addition to being able to provide a bumper beam that complies with the pendulum standard, it also has features such as excellent blowing properties such as drawdown resistance, pinch-off properties, and deep drawability, as well as excellent recyclability.

Examples Next, the present invention will be explained in more detail with reference to examples.
The present invention is not limited in any way by these examples.

Regarding the resin composition, the bending elastic modulus is determined as the grain property, the drawdown resistance, pinch-off strength, and deep drawability are determined as the blow properties, and the material fracture state, the fracture state of the pinch-off part, and the maximum Evaluation was made by determining the amount of deformation.

The blow characteristic evaluation method and pendulum test method are shown below.

Evaluation of blow characteristics: Using a die with a die diameter of 37mm and a core diameter of 33mm, cylinder temperature 230℃, mold temperature 40℃, parison weight 3
Blow molding was performed under the condition of 40 g.

(1) Drawdown resistance The drawdown ratio of the parison length immediately after injection and the parison length 15 seconds after injection was calculated using the following formula, and the drawdown resistance was determined (see Figure 1) Drawdown ratio - LO/ L L: Parison length after 15 seconds Lo: Parison length evaluation conditions immediately after injection Parison weight: 340g Parison length immediately after injection: 40cwr Resin temperature
: 230°C ± 5°C (2) Pinch-off strength A 112-square bottle with dimensions of 120 x 120 x 200 mm was molded, and a bending test piece (length g cm, width 2 crn) was made with the pinch-off part that occurs at the bottom of the square bottle in the center. (See Fig. 2), and its strength was determined by the following equation by performing an autograph three-point bending test as shown in Fig. 3.

Autograph measurement conditions Bending speed: 5 mm/min Span: 4011111 Full scale: 10 to 50 kg (3) Wall thickness of the corner part (5R) relative to the wall thickness of the center part of the square bottle used for deep drawability pinch-off strength evaluation The deep drawability was determined by calculating the ratio using the following formula (see Figure 4).

Deep drawability (%) - T'(+++m)/T(+u+)X1
00 Pendulum Test A bumper beam was molded under the following molding conditions.

The length of the mold during molding was 2,000 mm, the date was 6-8 J2Sl, the weight was 9-12 kg, and the length of the parison was 2.100 mm.

The product length is 1,600 mm.

Molding conditions Molding machine: 90mm" Hollow molding machine Screw: 90mm' Die: 300mm' Maccumulator 225Q Mold clamping pressure: 60TON Screw revolution speed: 40rpm Motor load: 115A Temperature condition Cylinder No. 1: 230℃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℃ Molding cycle: 330sec Mold temperature: 28℃ Resin temperature: 225℃ Bumper beam [without skin (7 Asia)] Vehicle body (1
400 (9), and the amount of deformation and fracture state were determined using a pendulum testing machine. Fig. 5 is an explanatory diagram of the pendulum test, and Fig. 6 shows the cross-sectional shape of the bumper beam.

(4) Amount of Deformation In a pendulum test, the amount of displacement of the upper rear surface of the bumper beam (ΔD in FIG. 5) was determined under the following evaluation conditions.

Evaluation conditions Hitting speed = 5rnile/hr Body weight: 1400 to 9 Hitting position: Center hitting test temperature Knee 30°C Product weight Near kg Pendulum weight + 140072'9 (5) Material destruction Insert bolt part as shown in Figure 7 The state of destruction and crack occurrence was visually observed.

(6) Pinch-off portion fracture t1g8 The state of tear in the pinch-off portion as shown in Figure 8 was visually observed.

Further, the properties of the polypropylene resin, high density polyethylene, EPR, and talc used as raw material components of the resin composition are shown in Tables 1, 2, 3, and 4, respectively.

Table 1 (Note') Ml: Melt Index CI] Near-Isotactic Bentuft Fraction Table 2 Table 3 (Note) Complex viscosity is the value at a frequency of 0.0 I Rad/sec.

Table 4 Example L 2, Comparative Example L 2 Polypropylene resin of the type shown in Table 5, EPR, and talc were mixed in the proportions shown in Table 5, and heated at about 230°C using a kneader. Various resin compositions were prepared by melt-kneading and pelletizing.

Regarding the resin composition thus obtained, - film properties and blowing characteristics were determined, and a pendulum test was conducted. The results are shown in Table 5.

Examples 3 to 14, Comparative Examples 3 to 14 Each component of the type and amount shown in Table 5 was mixed with a kneader for about 2
A resin composition was prepared by melt-kneading and pelletizing at 30°C. Regarding this material, - film physical properties and blowing characteristics were determined, and a pendulum test was conducted to evaluate its performance. The results are shown in Table 5.

In addition, the Ml of the polypropylene blend in Example 11 was 0.6 g/10 min, and the ethylene unit content was 4.3.
wt% (I) is 96%.

In addition, in Comparative Example 13, Xenoy1 was used as the resin.
Comparative Example 1 using 402B (manufactured by GE, trade name, polybutylene terephthalate/polycarbonate alloy)
In No. 4, a recycled product of Xenoy 1402B was used as the resin. Furthermore, in Example 13, Example 3
Uses recycled products. Regarding the use of recycled products, the parison generated in an amount of about 60 wt % was crushed into pellets by a crusher, and only the pellets were supplied to a blow molding machine.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the drawdown resistance test, Figure 2
The figure is a perspective view of a square bottle showing where the specimen was cut to determine pinch-off strength. An explanatory diagram showing the wall thickness of the center part and the corner part of a square bottle. Figure 5 is an elevational view (a) and a plan view (b) of the case where a bumper beam is attached to the vehicle body in order to conduct a pendulum test. ), Figure 6 is a front view (a) and cross-sectional view (b) of the bumper beam attached to the vehicle body, Figure 7 is a perspective view showing the state of material failure of the bumper beam in the pendulum test, and Figure 8 is the pendulum test. It is a perspective view showing the destroyed state of the pinch-off part of the bumper beam in . In the figure, l is the parison, 2 is the pinch-off part, 3 is the test piece cutting point in the square bottle, 4 is the cutting test piece, 5 is the bumper beam, 6 is the car body, 7 is the pendulum testing machine, 8 is the impact ridge, 9 is the insert bottle, 10 is the crank occurrence part, 11 is the fracture occurrence part, 12 is the tear in the pinch-off part, T is the wall thickness of the center part, T' is the wall thickness of the corner part, ΔD is the displacement of the upper rear surface, Lo is the length of the parison immediately after injection, and L is the length of the parison after 15 seconds. Patent applicant Idemitsu Petrochemical Co., Ltd.

Claims (1)

[Scope of Claims] 1(a) A propylene-ethylene copolymer having a melt index of 1.0 g/10 min or less, an ethylene unit content of 1 to 15% by weight, and an isotactic pentad fraction of the propylene homopolymerization part of 92% or more. 40 to 93% by weight of a polymer; (b) 2 to 15% by weight of a rubber-like elastic body having a complex viscosity of 3 x 10^4 to 1 x 10^5 poise at a frequency of 0.01 Rad/sec; (c) Average particle diameter 5μm or less and average aspect ratio 3~
A resin composition for a blow-molded bumper beam comprising 5 to 30% by weight of talc. 2. A part of component (a) in the composition according to claim 1 has (a') a melt index of 0.1 g/10 minutes or less,
and formula A=Z_5_0/Z_1_0 (Z_1_0 and Z_5_0 in the formula are measured temperature 150
30% by weight based on the total amount of high-density polyethylene in which the parameter A defined by the constant strain rate elongational viscosity at 10 sec and 50 sec at a strain rate of 0.05 sec^-^1 is in the range of 2 to 20. A resin composition for blow-molded bumper beams, which comprises replacing the resin composition in an amount not exceeding .