JPH07110915B2 - Blow molding bumper beam resin composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel resin composition for blow molding bumper beam, and more particularly, to low cost and blow characteristics such as drawdown resistance, pinch-off characteristics, and deep drawability. The present invention also relates to a resin composition for blow-molded bumper beams, which is excellent in recyclability and conforms to the US 5 mile / hr pendulum standard.

2. Description of the Related Art Conventionally, automobile bumper beams have been made of metal, but in recent years, they have been shifting to plastics for the purpose of weight reduction, rust prevention and shaping.

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

On the other hand, recently, there is an increasing demand for a low cost bumper beam that complies with the strict standards of the US 5 mile / hr pendulum test. However, blow molding of the high density polyethylene of (1) and polypropylene of (2) has a drawback that the strength is insufficient although the cost is low, but the blow of Xenoy of (3) is difficult. Molded products have the drawbacks of high material cost and poor recycling properties.

Further, although the blow molding of the talc-containing polypropylene-based composite material of (4) is low cost, it has the drawback of low low temperature impact strength, and the stampable sheet of (5) and SMC of (6) are total. The cost is inevitable.

DISCLOSURE OF THE INVENTION The present invention overcomes the drawbacks of the conventional plastic molding materials for bumper beams, and is low cost and has blowdown characteristics such as drawdown resistance, pinch-off characteristics, and deep drawing characteristics, and recycling. It has been made for the purpose of providing a plastic molding material for a bumper beam which is excellent in properties and conforms to the US 5 mile / hr pendulum standard.

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to develop a plastic blow molding material for bumper beams having the above-mentioned preferable properties, and as a result, have identified a specific polypropylene-ethylene copolymer or a high density polyethylene thereof. For a mixture with
It was found that a resin composition containing a specific rubber-like elastic body and talc in a predetermined ratio can meet the purpose, and based on this finding, the present invention has been completed.

That is, the present invention provides (a) melt index 1.0 g / 1
0 minutes or less, ethylene unit content of 1 to 15% by weight, and isotactic pentad fraction of propylene homopolymer of 92%
With the above propylene-ethylene copolymer 40 to 93 wt%,
(B) Complex viscosity at frequency of 0.01 Rad / sec is 3 × 10 ⁴
~ 1 x 10 ⁶ poise rubber-like elastic body 2-15% by weight,
(C) Average particle size of 5 μm or less and average aspect ratio of 3 to
A resin composition for blow molding bumper beam, which comprises 5 to 30% by weight of 20 talc, and a part of the component (a) thereof (a ') having a melt index of 0.1 g / 10 min or less and a formula A = Z _50. / Z ₁₀ (Z ₁₀ and Z ₅₀ in the formula are measured temperature 150 ° C, strain rate 0.05s
The constant A strain-elongation viscosity of ec ^-1 is a value at 10 seconds and 50 seconds respectively) and the parameter A defined in the range of 2 to 20 is substituted in an amount not exceeding 30% by weight based on the total amount of high-density polyethylene. A resin composition for blow molding bumper beam is provided.

Hereinafter, the present invention will be described in detail.

In the composition of the present invention, the propylene-ethylene copolymer used as the component (a) has a melt index
1.0 g / 10 minutes or less, preferably 0.8 g / 10 minutes or less, more preferably 0.6 g / 10 minutes or less, it is necessary that the melt index exceeds 1.0 g / 10 minutes, drawdown resistance, Deep drawability and low temperature impact strength decrease.

Further, the isotactic pentad fraction of the propylene homopolymer of the propylene-ethylene copolymer needs to be 92% or more, preferably 94% or more, more preferably 96% or more. If the isotactic pentad fraction is less than 92%, the rigidity is insufficient and the amount of deformation in the pendulum test is large, so that the object of the present invention cannot be sufficiently achieved. The isotactic pentad fraction as used in the present invention means the ray ratio. A. Zambelli et al., "Macromolecules," No. 8
Volume, page 925 (1973)
Isotactic fraction in pentad units in the polypropylene molecular chain measured by ¹³ C-NMR, ie,
It is the fraction of propylene monomer units in which five propylene monomer units are continuously meso-bonded. However, regarding the attribution of peaks, "Macromolecules (Macr
o molecules) ”, vol. 8, page 687 (1975). Specifically, ¹³
The isotactic pentad unit is measured by the intensity fraction of the mmmm peak in all the absorption peaks in the methyl carbon region of the C-NMR 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 the treatments such as extraction and fractionation.

Further, the content of ethylene units in the propylene-ethylene copolymer needs to be in the range of 1 to 15% by weight, preferably 2 to 10% by weight, more preferably 3 to 7% by weight. If this 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 tends to increase.

In the composition of the present invention, the propylene-ethylene copolymer of the component (a) may be used alone or in combination of two or more, and does not impair the object of the present invention. You may use together a propylene homopolymer in the range. Further, in some cases, a part of the component (a) is not more than 30% by weight based on the total amount of the composition, preferably 3 to.
20% by weight, more preferably 3 to 15% by weight of (a ')
It may be replaced by a component, high density polyethylene. When the amount of the component (a ') exceeds 30% by weight, the pinch-off strength, high temperature rigidity and dimensional accuracy are deteriorated. When the high density polyethylene as the component (a ') is not used, it is desirable to use a propylene-ethylene copolymer having the melt index of 0.5 g / 10 minutes or less as the component (a). .

The high-density polyethylene as the component (a ') has a melt index of 0.1 g / 10 minutes or less, preferably 0.07 g / 10 minutes or less,
More preferably, it should be 0.04 g / 10 minutes or less. If the melt index exceeds 0.1 g / 10 minutes, the drawdown resistance, deep drawability and low temperature impact strength tend to decrease.

Furthermore, the high-density polyethylene of the component (a ') has the formula A = Z ₅₀ / Z ₁₀ (wherein Z ₁₀ and Z ₅₀ are a measurement temperature of 150 ° C. and a strain rate of 0.05 s.
ec ^-1 constant strain rate elongational viscosities at 10 and 50 seconds respectively) parameter A defined by 2 to 20, preferably 3 to 1
It should be 0, more preferably in the range of 4-8. If the value of A is less than 2, molding processability such as drawdown resistance and deep drawability is insufficient, and if it exceeds 20, the pinch-off strength and the extrusion property deteriorate.

In the composition of the present invention, the component (b) has a frequency of
A rubber having a complex viscosity at 0.01 Rad / sec in the range of 3 × 10 ⁴ to 1 × 10 ⁶ poise, preferably 6 × 10 ^{4 to} 7 × 10 ⁵ poise, and more preferably 9 × 10 ⁴ to 4 × 10 ⁵ poise. Elastic body is used. If this complex viscosity is less than 3 × 10 ⁴ poise, drawdown resistance, deep drawability and low temperature impact strength are insufficient, and if it exceeds 1 × 10 ⁶ poise, dispersion is insufficient and a thickening effect is obtained. As a result, the drawdown resistance decreases, and the deep drawability and low temperature impact strength also tend to decrease.

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

The talc used as the component (c) in the composition of the present invention has an average particle size of 5 μm or less and an average aspect ratio of 3 to 20, preferably 7 to 20, and more preferably 10 to 20.
Must be within the range. The average particle size is 5 μm
When the average aspect ratio is less than 3, the 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 in the pendulum test is large. The purpose cannot be fully achieved, and if it exceeds 20, the pinch-off strength and low temperature impact strength decrease.

The content of the 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. Parts can be replaced by component (a ') in an amount of not more than 30% by weight, preferably 3 to 20% by weight, more preferably 3 to 15% by weight, based on the total weight of the composition. Also,
The content of the component (b) is 2 to 15% by weight, preferably 2 to 12
It should be in the range of wt%, more preferably 2 to 8 wt%. When the content of the component (b) is less than 2% by weight, the low temperature impact strength is insufficient, and when it exceeds 15% by weight, the pinch-off strength decreases and the deformation amount in the pendulum test increases.

Further, the content of the component (c) needs to be in the range of 5 to 30% by weight, preferably 5 to 25% by weight, more preferably 5 to 20% by weight. If the content of the component (c) is less than 5% by weight, the rigidity and dimensional accuracy are poor, and the amount of deformation in the pendulum test is large, so that the object of the present invention cannot be sufficiently achieved. ,
Deep drawability and impact strength decrease.

The composition of the present invention, as long as the required physical properties are not impaired, if desired, other thermoplastic resins, such as maleic anhydride-modified polyolefin and acrylic acid-modified polyolefin, further inorganic fillers other than talc, for example Calcium carbonate, mica, glass fiber and various additives,
For example, an antioxidant, an ultraviolet absorber, a heat stabilizer, a lubricant, a flame retardant, a coloring agent and the like may be contained.

The composition of the present invention comprises, for example, component (a), component (a ′),
A uniaxial kneading machine, a biaxial kneading machine, a component (b), a component (c) and an inorganic filler or various additives used as desired are added.
It can be prepared by melt-kneading using a multi-screw kneader, Banbury mixer or the like. At this time, the melt-kneading conditions are not particularly limited, but when a kneading machine other than a Banbury mixer is used, the resin used is a high-viscosity type, so deterioration of the resin occurs due to shear heat generation during kneading, and drawdown resistance Since the temperature tends to decrease, it is desirable to set the condition that the resin temperature is suppressed as much as possible (maximum temperature 250 ℃). For that, the kneading temperature is 190 to 230 ℃ (set temperature)
It is advantageous to minimize the resin pressure in the cylinder as much as possible.

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

The blow-molded bumper beam resin composition of the present invention is composed of a specific propylene-ethylene copolymer or a mixture thereof and a high-density polyethylene, a rubber-like elastic body, and talc at a low cost. In addition, it is possible to provide a bumper beam that complies with the US 5 mile / hr pendulum standard, and it has features such as excellent drawdown resistance, pinch-off characteristics, deep drawability, and other blow characteristics and recyclability.

EXAMPLES Next, the present invention will be described in more detail with reference to Examples.
The invention is in no way limited by these examples.

For the resin composition, flexural modulus was determined as a general physical property, drawdown resistance, pinch-off strength and deep drawability were determined as blow characteristics, and further, by a pendulum test, a material fractured state, a pinch-off portion fractured state and maximum deformation. It was evaluated by determining the amount.

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

Evaluation of blow characteristics Using a die having a die diameter of 37 mm 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 340 g.

(1) the draw-down ratio of the parison length and the parison length after 15 seconds immediately after drawdown resistance injection calculated by the following equation to determine the drawdown resistance (see FIG. 1) Drawdown ratio = L ₀ / LL: Length of parison after 15 seconds L ₀ : Length of parison immediately after injection Evaluation condition Parison weight: 340g Length of parison immediately after injection: 40cm Resin temperature: 230 ℃ ± 5 ℃ (2) Pinch-off strength 120 × 120 × Bending test piece (length 8c
m, width 2 cm) was created by cutting (see FIG. 2), and its strength was determined by the following equation by performing an autograph three-point bending test as shown in FIG.

Autograph measurement conditions Bending speed: 5mm / min Span: 40mm Full scale: 10 to 50kg (3) Deep drawability Ratio of the corner (5R) wall thickness to the center bottle wall thickness used for pinch-off strength evaluation Was calculated by the following formula to determine the deep drawability (see FIG. 4).

Deep drawability (%) = T ′ (mm) / T (mm) × 100 Pendulum test A bumper beam was molded under the following molding conditions. In addition,
The mold length at the time of molding is 2,000 mm, the date is 6 to 8 kg, the burr is 9 to 12 kg, the parison length is 2,100 mm, and the product length is 1,600 mm.

Molding conditions Molding machine: 90mm ^φ Hollow molding machine Screw: 90mm ^φ Die: 300mm ^φ Macu mulator: 25l Mold clamping pressure: 60TON Screw rotation speed: 40rpm Motor load: 115A Temperature condition Cylinder No 1: 230 ℃ No 2: 210 ℃ No 3: 190 ℃ No 4: 190 ℃ Crosshead No 1: 190 ℃ No 2: 190 ℃ No 3: 190 ℃ Die No 1: 190 ℃ No 2: 190 ℃ Molding cycle: 330sec Mold temperature: 28 ℃ Resin temperature : 225 ℃ bumper beam [without skin (facia)] body (14
(00 kg) and the amount of deformation and the state of breakage were determined by a pendulum tester. FIG. 5 shows an explanatory view of the pendulum test, and FIG. 6 shows a sectional shape of the bumper beam.

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

Evaluation conditions Impact speed: 5mile / hr Body weight: 1400kg Impact position: Center impact test temperature: -30 ℃ Product weight: 7kg Pendulum weight: 1400kg (5) Material destruction Destruction or crack of insert bolt part as shown in Fig. 7 The generation state was visually observed.

(6) Destruction of pinch-off portion The broken state of the pinch-off portion as shown in FIG. 8 was visually observed.

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

Examples 1 and 2 and Comparative Examples 1 and 2 Polypropylene resins of the types shown in Table 5 were mixed with EPR and talc in the proportions shown in Table 5, and melt-kneaded at about 230 ° C. using a kneader. Then, various resin compositions were prepared by pelletizing.

With respect to the resin composition thus obtained, general physical properties and blow characteristics were determined, and a pendulum test was conducted. The results are shown in Table 5.

Examples 3 to 14 and Comparative Examples 3 to 14 Each type and amount of each component shown in Table 5 was used to prepare about 23
The resin composition was prepared by melt-kneading at 0 ° C. and pelletizing. The general physical properties and blow characteristics of this product were determined, and a pendulum test was performed to evaluate its performance. The results are shown in Table 5.

Incidentally, the MI of the polypropylene blend in Example 11
Is 0.6 g / 10 minutes, ethylene unit content is 4.3 wt%, [I] is 96
%.

Further, in Comparative Example 13, Xenoy 1402B (G
A polybutylene terephthalate / polycarbonate alloy manufactured by E Co., Ltd. was used, and in Comparative Example 14, a recycled product of Xenoy 1402B was used as the resin. Furthermore, in Example 13, the recycled product of Example 3 was used. Regarding the use of recycled products, burr generated by about 60 wt% of parison was crushed into pellets by a crusher, and then only the pellets were supplied to a blow molding machine.

[Brief description of drawings]

FIG. 1 is an explanatory view for obtaining drawdown resistance, and FIG.
The figure is a perspective view of a square bottle showing a cutting location of a test piece for obtaining the pinch-off strength, FIG. 3 is an explanatory view of a three-point bending test for obtaining the pinch-off strength, and FIG. 4 is a drawing for deep drawability. FIG. 5 is an explanatory view showing the center wall thickness and the corner wall thickness of the square bottle, and FIG. 5 is an elevation view (a) and a plan view (b) when a bumper beam is attached to a vehicle body for carrying out a pendulum test. FIG. 6 is a front view (a) and a cross-sectional view (b) of a bumper beam attached to a vehicle body, FIG. 7 is a perspective view showing a material destruction state of the bumper beam in a pendulum test, and FIG. 8 is a pendulum test. It is a perspective view which shows the destruction state of the pinch-off part of a bumper beam. In the figure, reference numeral 1 is a parison, 2 is a pinch-off portion, 3 is a test piece cutting location in a square bottle, 4 is a cutting test piece, 5 is a bumper beam, 6 is a vehicle body, 7 is a pendulum tester, 8 is an impact ridge, 9 Is an insert bottle, 10 is a crack occurrence portion, 11 is a fracture occurrence portion, 12 is a pinch-off portion breakage, T is the center wall thickness, T'is the corner wall thickness, ΔD
Is the upper rear surface displacement, L ₀ is the length of the parison immediately after injection,
L is the length of the parison after 15 seconds.

Claims (2)

[Claims] 1. A propylene-ethylene copolymer having a melt index of 1.0 g / 10 minutes or less, an ethylene unit content of 1 to 15% by weight, and an isotactic pentad fraction of a propylene homopolymer of 92% or more. ~ 93 wt%, (b)
Complex viscosity at frequency of 0.01 Rad / sec is 3 × 10 ⁴ to 1 ×
A blow-molded bumper beam resin composition comprising 2 to 15% by weight of a rubber-like elastic body of 10 ⁶ poise and (c) 5 to 30% by weight of talc having an average particle size of 5 μm or less and an average aspect ratio of 3 to 20. Wherein Z ₁₀ in at a part of the component (a) in the composition according to claim 1 (a ') a melt index 0.1 g / 10 minutes or less, and wherein A = Z ₅₀ / Z ₁₀ (formula And Z ₅₀ are measured temperature 150 ℃, strain rate 0.05s
The constant A strain-elongation viscosity of ec ^-1 is a value at 10 seconds and 50 seconds respectively) and the parameter A defined in the range of 2 to 20 is substituted in an amount not exceeding 30% by weight based on the total amount of high-density polyethylene. Blow molding bumper beam resin composition.