JPH04120145A - Resin composition for blow-molded bumper beam - Google Patents

Abstract

PURPOSE:To provide the title composition excellent in rigidity, impact resistance, mechanical properties such as pinch-off strength, dimensional accuracy, drawdown resistance etc., comprising a specific polypropylene-based resin and talc with both specified mean particle size and mean aspect ratio. CONSTITUTION:The objective composition of low specific gravity, excellent in recycling potential and cost performance comprising (A) 70-99wt.% of a polypropylene-based resin composed of (1) a propylene homopolymer <=1.0g/10min in melt index and >=93% in isotactic pendant fraction and (2) a propylene-ethylene copolymer <=1.0/10min in melt index, <=15wt.% in ethylene unit content and >=93% in the isotactic pendant fraction for the propylene homopolymerized domain and (B) 1-30wt.% of talc <=10mu in mean size and 3-20 in mean aspect ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a novel resin composition for blow-molded bumper beams, more specifically, mechanical properties such as rigidity, impact resistance, and pinch-off strength, dimensional accuracy, and drawdown resistance. The present invention relates to a low specific gravity resin composition for blow-molded bumper beams that has excellent moldability such as deep drawability, recyclability, and cost performance.

BACKGROUND OF THE INVENTION Conventionally, bumper beams for automobiles have been made of metal, but in recent years they have been made of plastic for the purpose of weight reduction, rust prevention, and formability.

Examples of plastic bumper beams include (1)
Those made by sheet-molding polypropylene containing glass fiber mantle, (2) high-density polyethylene, (3) polypropylene, (4) Xenoy (manufactured by GE, trade name, polybutylene terephthalate/polycarbonate alloy), etc. Products made by blow molding engineering resins are known.

However, sheet molding of glass fiber mat-containing polypropylene (1) and blow molding of engineering resin (4) inevitably have high specific gravity and high cost. In particular, blow molded engineering resins (4) lack chemical resistance and
Recycled products have the disadvantage that drawdown resistance and deep drawability are significantly reduced, making them unsuitable for industrial use. In addition, products made by blow molding high-density polyethylene (2) and polypropylene (3) are low in cost, but their dimensional accuracy and deformation resistance during the pendulum test are insufficient, so they are not always satisfactory. .

Problems to be Solved by the Invention The present invention overcomes the drawbacks of conventional plastic molding materials for bumper beams, and improves rigidity, impact resistance,
The purpose is to provide a plastic blow molding material for bumper beams with low specific gravity that has excellent mechanical properties such as pinch-off strength, dimensional accuracy, moldability such as drawdown resistance and deep drawability, recyclability, and cost performance. It has been done.

Means for Solving the Problems As a result of intensive research to develop a plastic blow molding material for bumper beams, the inventors of the present invention have determined that talc is added to a specific polypropylene resin or a mixture of it and high-density polyethylene. It has been discovered that a resin composition containing the following amounts provides a bumper beam with extremely excellent performance, and based on this knowledge, the present invention has been completed.

That is, the present invention provides (a) (b) melt index 1.0yl 10 minutes or less and isotactic penta 7
Propylene homopolymer with a 1 fraction of 93% or more, and (b) propylene with a melt index of 1.0yl 10 minutes or less, an ethylene unit content of 15% by weight or less, and an isotactic pentad fraction of the propylene homopolymerization part of 93% or more. - 70 to 99% by weight of at least one polypropylene resin selected from ethylene copolymers; (b) 1 to 30% by weight of talc having an average particle diameter of 10 μm or less and an average aspect ratio of 3 to 20; A resin composition for a blow-molded bumper beam and a part of its component (a) have (a') a melt index of 0.19/10 minutes or less, and A = Z s. / Z +.

(ZID and Z50 in the formula are values at constant strain rate elongational viscosity of 10 sec and 5 Qsec, respectively, at a measurement temperature of 150°C and a strain rate of sail 05 sec-'), which is in the range of 2 to 20. The present invention provides a resin composition for a blow-molded bumper beam, in which high-density polyethylene is replaced in an amount not exceeding 30% by weight based on the total amount.

The present invention will be explained in detail below.

In the composition of the present invention, the polypropylene resin of component (A) may be a propylene homopolymer or a propylene-based resin.
Ethylene copolymers are used. The melt index of this polypropylene resin is 1.0 g/l 0 min or less, preferably 0.0 g/l 0 min or less, more preferably 0.6 yl l 0 min or less, particularly preferably 0.0 g
/10 minutes or less, and if the melt index exceeds 1.09/10 minutes, molding properties such as drawdown resistance and deep drawability deteriorate.

Further, the isotactic pentad fraction of the propylene homopolymer and the isotactic pentad fraction of the propylene homopolymer portion of the propylene-ethylene copolymer are 93% or more, preferably 95% or more, more preferably 9
It needs to be 7% or more. If the isotactic pentad fraction is less than 93%, the rigidity is insufficient,
Moreover, the amount of deformation during the pendulum test is large, and the object of the present invention cannot be fully achieved. The isotactic pentad fraction referred to in the present invention refers to the isotactic pentad fraction of A.
[Macromolecules J Vol. 8, No. 9]
1 following the method published on page 25 (1973).
It refers to the isotactic fraction of pentad units in a polypropylene molecular chain measured by 3C-NMR, that is, the fraction of propylene monomer units in which five propylene monomer units are continuously bonded.

Regarding the assignment of peaks, it was done based on the correction board of the above-mentioned document described in "Macromolecules J Vol. 8, p. 687 (1975). Specifically, +3C -mmmm in the total absorption peak in the methyl carbon region of the NMR spectrum
The isotactic pentad unit is determined by the intensity fraction of the peak. 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 cotylene units in the propylene-ethylene copolymer needs to be 15% by weight or less, preferably 10% by weight or less, and more preferably 5% by weight or less. When this content exceeds 15% by weight, the rigidity tends to decrease and the amount of deformation during the pendulum test tends to increase.

In the composition of the present invention, as the polypropylene resin of the component (a), the propylene homopolymer of the component (a) may be used, or the propylene-ethylene copolymer of the component (b) may be used. or a mixture thereof may be used.

In the composition of the present invention, the high-density polyethylene as component (a'), which is optionally used as a part of component (a), is
Melt index is 0.1g/10min or less, preferably 07yl l 0min or less, more preferably 0.00
g/10 minutes or less. When the melt index exceeds 0.1 g/10 minutes, there is a tendency for moldability such as drawdown resistance and deep drawability to deteriorate.

Furthermore, the high-density polyethylene of the component (a') has A=
Z. /Z,.

(Zl. and Z in the formula are values at constant strain rate extensional viscosity of 10 sec and 5 Q sec, respectively, at a measurement temperature of 150°C and a strain rate of 0.05 sec-'). ~20, preferably 3~IO
It is necessary that the number is more preferably in the range of 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 extrusion properties will deteriorate.

The talc used as component (b) in the composition of the present invention has an average particle diameter of 10 pm or less, preferably 5 μm or less, more preferably 2 μm or less, and an average aspect ratio of 3 to 20, preferably 7 to 20, or more. Preferably l
It is necessary to be in the range of 0 to 20. When the average particle diameter exceeds 10 μm, deep drawability, rigidity, impact resistance, 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. is large, and the object of the present invention cannot be fully achieved.

The content of component (a) in the composition of the present invention is 70 to 99
% by weight, preferably from 75 to 95% by weight, more preferably from 80 to 90% by weight, and optionally a portion thereof, based on the total weight of the composition, in an amount not exceeding 30% by weight, preferably from 3 to 25% by weight. %, particularly preferably from 5 to 20% by weight of component (a'). Also, (b)
The content of the components should be in the range 1 to 30% by weight, preferably 5 to 25% by weight, particularly preferably 10 to 20% by weight. Inclusion of component (a') can further improve deep drawability, but if this amount exceeds 30% by weight based on the total amount of the composition, pinch-off strength, high-temperature rigidity, and dimensional accuracy will decrease.

Furthermore, if the content of component (b) is less than 1% 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 weight percentage is exceeded, pinch-off strength, deep drawability, and impact strength will decrease.

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

The composition of the present invention includes, for example, component (a), component (a'), (
b) It can be prepared by melt-kneading the ingredients and inorganic fillers and various additives used as desired using a -shaft kneader, twin-shaft kneader, multi-shaft kneader, Banbury mixer, etc. can. At this time, there are no particular restrictions on the melt mixing conditions, but if a kneading machine other than the Banbury mixer is used, the resin used is of a high viscosity type, so the resin will deteriorate due to heat generation due to shearing during kneading, making it difficult to draw down. Since the properties tend to decrease, it is desirable to set conditions that suppress the resin temperature as much as possible (maximum temperature 250°C). To do this, the kneading temperature should be around 190 to 230°C (set temperature) and the resin pressure in the cylinder should be kept as low as possible. It is advantageous to suppress it.

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 polypropylene resin or a mixture of it and high-density polyethylene, and talc. It can provide a low specific gravity bumper beam with excellent mechanical properties and dimensional accuracy, and has features such as excellent formability such as drawdown resistance and deep drawability, recyclability, and cost performance. .

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, - Specific gravity and flexural modulus are determined as film physical properties, drawdown resistance, pinch-off strength, and deep drawability are determined as blow properties, and the state of material failure and failure state of pinch-off part are determined by pendulum test. Evaluation was made by determining the maximum 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 37 + * + i and a core diameter of 33 mm,
Blow molding was performed under the conditions of a cylinder temperature of 230°C, a mold temperature of 40°C, and a parison weight of 340g.

(1) Drawdown resistance The drawdown ratio between the length of the parison immediately after injection and the length of the parison 15 seconds after injection was calculated using the following formula, and the drawdown resistance was determined (see Figure 1) Drawdown ratio = L, /L L: Parison length after 15 seconds Lo: Parison length evaluation conditions immediately after injection Parison weight: 34h Parison length immediately after injection: 40cra Resin temperature
: 230"C! ±5℃ (2) Pinch-off strength 120 x ] A bending test piece (length 3 cm, width 2 cm) shaped like a 20 x 200 mm Iffff square pin and with the pinch-off part that occurs at the bottom of the square bottle in the center was (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: 5mWl/min Span = 401 Full scale = lO~50J21? (3) Deep drawability The ratio of the wall thickness of the corner part (5R) to the wall thickness of the center part of the square bottle used for pinch-off strength evaluation was calculated using the following formula, and the deep drawability was determined (Figure 4). reference).

Deep drawability (%)-T'(+x+m)/T(mm)X
100 Pendulum Test A bumper beam was molded under the following molding conditions.

In addition, the mold length during molding is 2,000+in, the date is the product 6-8 kg, the burr is 9-12 kg, and the parison length is 2.
．． 100m+m.

The product length is 600 mm.

Molding conditions Molding machine: 90mm" blow molding machine Screw: 90mm' Die: 300+i+m" Maccumulator = 25Q Mold clamping pressure: 60TON Screw revolution speed: 4Qrpm Motor load: 115A Temperature conditions Cylinder No. I: 230°C No. 2:
210°C No. 3: 190°C No. 4: 190°C Crosshead No.: 190°C No. 2: 190°C No. 3: 190°C Die No. 1: 190°C No. 2: 190°C Molding cycle: 330sec Mold temperature: 28°C Resin temperature =225℃ Bumper beam [without fascia] is attached to the car body (1
260 kg), and the amount of deformation and fracture state were determined using a pendulum tester. 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: 2.5m1le/hr Vehicle weight
: 1,260 kg Impact position: Center impact test temperature; Room temperature Product weight: 6 to 8 J1 g Pendulum weight: 1280 to 9 (5) Material destruction Visually observed the fracture of the insert bolt part and the occurrence of crank as shown in Figure 7. .

(6) Pinch-off portion fracture The pinch-off portion was visually observed for breakage as shown in FIG.

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

Table [■] Near isotactic pentad fraction table (note) A = Z so/Z ro (Z 5oSZ10:
Table 4 Examples 1 to 3 Comparative Example 11 Polypropylene resins of the types shown in Table 4 and talc were mixed in the proportions shown in Table 4, and heated at about 230°C using a kneader. Various resin compositions were prepared by melt-kneading and pelletizing.

Regarding the thus obtained resin composition, -grain quality and blow characteristics were determined, and a pendulum test was conducted. The results are shown in Table 4.

Examples 4 to 11, Comparative Examples 3 to 15 Approximately 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, M of the polypropylene blend in Example 7
l is 0.7gl l 0 min, ethylene unit content is 2.5
vt% (I) is 96%.

In addition, in Comparative Example 12, Xenoy1 was used as the resin.
Comparative Example 1 using 402B (manufactured by GE, trade name, polybutylene terephthalate/polycarbonate alloy)
In No. 3, a recycled product of Xenoy 1402B was used as the resin. Furthermore, in Example 11, Example 4
Uses recycled products.

Regarding the use of recycled products, please refer to Parison's approx. [3Qw
After t% of the generated paris was pelletized by a crusher, only the pellets were fed to a blow molding machine.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram for determining drawdown resistance, 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 a case where a bumper beam is attached to the vehicle body in order to carry out the 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, 1 is a parison, 2 is a pinch-off part, 3 is a test piece cutting point in a square bottle, 4 is a cutting test piece, 5 is a bumper beam, 6 is a car body, 7 is a pendulum testing machine, 8 is an impact ridge, 9 is an insert bottle, IO is a crack occurrence part, 11 is a fracture occurrence part, 12 is a tear at a pinch-off part, T is a part of the wall thickness at the center, T' is a part thickness at a corner,
ΔD is the displacement amount of the upper rear surface, wrinkles are the length of the parison immediately after injection, and L is the length of the parison 15 seconds later.

Claims (1)

[Scope of Claims] 1 (a) (a) A propylene homopolymer with a melt index of 1.0 g/10 minutes or less and an isotactic pentad fraction of 93% or more, and (b) a melt index of 1.0 g/10 at least one polypropylene resin selected from propylene-ethylene copolymers with an ethylene unit content of 15% by weight or less and an isotactic pentad fraction of the propylene homopolymerization part of 93% or more. (b) average particle diameter of 10 μm or less and average aspect ratio of 3
A resin composition for a blow-molded bumper beam, comprising 1 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 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 is substituted in an amount not exceeding .