JP2730879B2 - Resin composition for blow molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel resin composition for blow molding, and more particularly to molding such as mechanical properties such as rigidity, impact resistance and pinch-off strength, dimensional accuracy, drawdown resistance and deep drawability. The present invention relates to a low-specific-gravity resin composition for blow molding having excellent processability, recyclability and cost performance.

[0002]

2. Description of the Related Art Conventionally, bumper beams for automobiles have been made of metal. However, in recent years, there has been a shift to plastics for the purpose of weight reduction, rust prevention, and imparting shapeability. Examples of the plastic bumper beam include: (1) a sheet made of glass fiber mat-containing polypropylene, (2) high-density polyethylene, (3) polypropylene, (4) Xenoy (manufactured by GE Corporation, product Name,
There are known those obtained by blow molding an engineering resin such as polybutylene terephthalate / polycarbonate alloy).

However, those obtained by sheet-forming the above-mentioned glass fiber mat-containing polypropylene (1) and those obtained by blowing-molding the engineering resin of (4) are inevitably high in specific gravity and cost. Especially (4)
Blow-molded engineering resin lacks chemical resistance, and recycled resin has drawbacks in that drawdown resistance and deep drawability are greatly reduced, making it unsuitable for industrial use. It is. In addition, the one formed by blow molding the high density polyethylene of (2) and the polypropylene of (3) is low in cost, but has insufficient dimensional accuracy and deformation resistance during pendulum test, and is not always satisfactory. Absent.

[0004]

SUMMARY OF THE INVENTION The present invention overcomes the drawbacks of the conventional blow molding resin material for blow molded articles such as bumper beams and provides mechanical properties such as rigidity, impact resistance, and pinch-off strength. It is an object of the present invention to provide a low-specific-gravity resin material for blow molding, which is excellent in dimensional accuracy, moldability such as drawdown resistance and deep drawability, recyclability, and cost performance.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to develop a resin material for blow molding having the above-mentioned preferable characteristics. As a result, a mixture of a specific polypropylene resin and high-density polyethylene has been obtained. On the other hand, it has been found that a resin composition containing talc in a predetermined ratio gives a blow-molded product such as a bumper beam having expected performance by blow molding, and based on this finding, the present invention has been completed. .

That is, the present invention relates to (a) (a) a propylene homopolymer having an isotactic pentad fraction of 93% or more, (b) an ethylene unit content of 15% by weight or less, and A polypropylene resin having at least one selected from propylene-ethylene copolymers having a tic pentad fraction of 93% or more and a melt index of 1.0 g / 10 minutes or less;
And (a ′) a melt index of 0.1 g / 10 min or less, and A = Z ₅₀ / Z ₁₀ (where Z ₁₀ and Z ₅₀ are constant strains at a measurement temperature of 150 ° C. and a strain rate of 0.05 sec ⁻¹ ). Each of the rate extensional viscosities is 10
70-99% by weight of a resin mixture composed of high-density polyethylene having a parameter A defined in the range of 2 to 20 in the range of 2 to 20 seconds, and (b) an average particle diameter of 10 μm or less and an average aspect ratio of 3 to A talc of 1 to 30% by weight, and wherein the content of the component (a ') is not more than 30% by weight based on the total amount of the composition. To provide.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the composition of the present invention, the propylene homopolymer of the component (a) may be used as the polypropylene resin of the component (a) in the resin mixture, A propylene-ethylene copolymer as a component may be used, or a mixture thereof may be used.

In the present invention, such a polypropylene resin, that is, a propylene homopolymer or a propylene-ethylene copolymer, or a mixture thereof may have a melt index of 1.0 g / 10 minutes or less, and is preferably 0.8 g / 10 min or less, more preferably 0.6 g
/ 10 minutes or less, particularly preferably 0.4 g / 10 minutes or less. If the melt index exceeds 1.0 g / 10 minutes, the moldability such as the drawdown resistance and the deep drawability is reduced.

The isotactic pentad fraction of the propylene homopolymer and the isotactic pentad fraction of the propylene homopolymerized portion of the propylene-ethylene copolymer are at least 93%, preferably at least 95%. Preferably, it needs to be 97% or more. If the isotactic pentad fraction is less than 93%, the rigidity is insufficient and the amount of deformation during the pendulum test is large, and the object of the present invention cannot be sufficiently achieved. The isotactic pentad fraction referred to in the present invention refers to A.I. "Macromolecules" No. 8 by A. Zambelli et al.
Vol., P. 925 (1973), the isotactic fraction in pentad units in the polypropylene molecular chain measured by ¹³ C-NMR, that is, five consecutive propylene monomer units. It is the fraction of propylene monomer units that are meso-bonded. However, regarding the assignment of peaks, see “Macromolecules”, Vol.
This was performed based on a corrected version of the above-mentioned document described on page 7 (1975). Specifically, the isotactic pentad unit is measured based on the intensity fraction of the mmmm peak among all the absorption peaks in the methyl carbon region of the ¹³ C-NMR spectrum. The value of the isotactic pentad fraction in the present invention is a value of the crystalline polymer as it is, not a value of the polymer after the treatment such as extraction and fractionation.

Further, the content of ethylene units in the propylene-ethylene copolymer must be 15% by weight or less, preferably 10% by weight or less, more preferably 5% by weight or less. If 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, the high-density polyethylene used as the component (a ') in the resin mixture has a melt index of 0.1 g / 10 min or less, preferably 0.07 g / 10 min or less, more preferably Is 0.0
It is necessary to be 4 g / 10 minutes or less. If the melt index exceeds 0.1 g / 10 minutes, there is a tendency that the moldability such as drawdown resistance and deep drawability is reduced.

Further, the high-density polyethylene of the component (a ') has the following formula: A = Z ₅₀ / Z ₁₀ (where Z ₁₀ and Z ₅₀ are constant at a measurement temperature of 150 ° C. and a strain rate of 0.05 sec ⁻¹ ). Each of the strain rate elongational viscosities is 10
It is necessary that the parameter A defined in the range of 2 sec. and 50 sec.) is in the range of 2 to 20, preferably 3 to 10, and more preferably 4 to 8. This A
If the value is less than 2, the moldability such as drawdown resistance and deep drawability will be insufficient, and if it exceeds 20, the extrusion characteristics will decrease.

The talc used as the component (b) in the composition of the present invention has an average particle diameter of 10 μm 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 7 μm. It is necessary to be in the range of 20, more preferably 10-20.
When the average particle diameter exceeds 10 μm, the 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 deformation amount during the pendulum test is low. Largely, the object of the present invention cannot be sufficiently achieved.

The content of the resin mixture component consisting of component (a) and component (a ') in the composition of the present invention is 70 to 70%.
99% by weight, preferably 75 to 95% by weight, more preferably 80 to 90% by weight, and the content of the component (b) is 1 to 30% by weight, preferably 5 to 25% by weight, particularly preferably 10 to 25% by weight. It must be in the range of 〜20% by weight.

In the composition of the present invention, based on the total amount of the composition, the content of the component (a ') is not more than 30% by weight, preferably 3 to 25% by weight, particularly preferably 5 to 20% by weight. It is necessary to be in the amount by weight.

Although the deep drawability can be further improved by the component (a '), if this amount exceeds 30% by weight based on the total amount of the composition, the pinch-off strength, high-temperature rigidity and dimensional accuracy decrease. If the content of the component (b) is less than 1% by weight, rigidity and dimensional accuracy are inferior, and the amount of deformation during a pendulum test is large, so that the object of the present invention cannot be sufficiently achieved. Strength,
Deep drawability and impact strength decrease.

The composition of the present invention may contain, if desired, thermoplastic resins other than the resin used in the present invention, such as maleic anhydride-modified polyolefin and acrylic acid-modified polyolefin, as long as the required physical properties are not impaired. And, inorganic fillers other than talc, such as calcium carbonate, mica, glass fiber and the like, and various additives, such as antioxidants, ultraviolet absorbers, heat stabilizers, lubricants, flame retardants, coloring agents and the like. Good.

The composition of the present invention comprises, for example, component (a)
Melting and kneading the component (a ′), the component (b), and the inorganic filler and various additives used as desired using a single-screw kneader, a twin-screw kneader, a multi-screw kneader, a Banbury mixer, or the like. Can be prepared. At this time, the melt-kneading conditions are not particularly limited, but when a kneader other than a Banbury mixer is used, the resin used is a high-viscosity type. Since the temperature tends to decrease, it is desirable to set conditions (the maximum temperature is 250 ° C.) in which the resin temperature is suppressed as much as possible. For this purpose, it is advantageous to set the kneading temperature to about 190 to 230 ° C. and to suppress the resin pressure in the cylinder as much as possible. It is.

By blowing the resin composition thus obtained in accordance with a known method, a desired blow-molded product, for example, a bumper beam or the like can be produced.

[0020]

The resin composition for blow molding according to the present invention comprises a mixture of a specific polypropylene resin and a high-density polyethylene and talc. The blow molding provides a resin composition having rigidity, impact resistance, pinch-off strength and the like. A molded article having a low specific gravity, such as a bumper beam, having excellent properties and dimensional accuracy can be provided, and is excellent in molding workability such as drawdown resistance and deep drawing property, recyclability, and cost performance.

[0021]

Next, the present invention will be described in more detail by way of examples, which should not be construed as limiting the present invention.

For the resin composition, specific gravity and flexural modulus were obtained as general physical properties, drawdown resistance, pinch-off strength and deep drawability were obtained as blow properties. Further, a pendulum test was conducted to determine the material destruction state and pinch-off portion. Evaluation was made by obtaining the fracture state and the maximum deformation amount. The evaluation method of the blow characteristics 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, a cylinder temperature of 230 ° C., a mold temperature of 40 ° C., and a parison weight of 3
Blow molding was performed under the condition of 40 g. (1) Drawdown resistance The drawdown ratio between the parison length immediately after the injection and the parison length after 15 seconds was calculated by the following equation, and the drawdown resistance was determined (see FIG. 1). Drawdown ratio = L ₀ / L L: Parison length after 15 seconds L ₀ : Parison length immediately after injection Evaluation condition Parison weight: 340 g Parison length immediately after injection: 40 cm Resin temperature: 230 ° C ± 5 ° C (2) Pinch-off strength 120 × 120 × A 1-liter square bottle of 200 mm was formed, and a bending test piece (length: 8 cm, width: 2 cm) was formed by cutting a pinch-off portion formed at the bottom of the square center (see FIG. 2), and the strength is shown in FIG. Such an autograph three-point bending test was performed, and the value was obtained by the following equation. Pinch-off strength (kg / cm) = Maximum load (kg) / thickness (cm) Autograph measurement conditions Bending speed: 5 mm / min Span: 40 mm Full scale: 10 to 50 kg (3) Deep drawability Angle used for pinch-off strength evaluation The ratio of the thickness of the corner portion (5R) to the thickness of the center portion of the bottle was calculated by the following equation 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, and the basis weight is 6-8 products.
kg, burr 9-12kg, parison length 2,100m
m, product length is 1,600 mm. Molding conditions Molding machine: 90 mmφ hollow molding machine Screw: 90 mmφ Die: 300 mmφ Accumulator: 25 liters Mold clamping pressure: 60 TON Screw rotation speed: 40 rpm Motor load: 115 A Bumper beam [no skin (fascia)] on the body (1
260 kg), and the amount of deformation and the state of destruction were determined using a pendulum tester. FIG. 5 is an explanatory view of the pendulum test, and FIG. 6 shows a cross-sectional shape of the bumper beam. (4) Deformation In the pendulum test, the amount of displacement of the upper rear surface of the bumper beam (FIG. 5D) was determined under the following evaluation conditions. Evaluation conditions Striking speed: 2.5 miles / hr Body weight: 1,260 kg Striking position: Centering Test temperature: Normal temperature Product weight: 6-8 kg Pendulum weight: 1260 kg (5) Material destruction Insert bolt as shown in FIG. The state of destruction and crack generation was visually observed. (6) Destruction of the pinch-off part The torn state of the pinch-off part as shown in FIG. 8 was visually observed. Tables 1, 2 and 3 show the properties of the polypropylene resin, high-density polyethylene and talc used as the raw material components of the resin composition, respectively.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

Examples 1 to 8 and Comparative Examples 1 to 13 Each component of the kind and amount shown in Table 4 was mixed for about 23
It was melt-kneaded at 0 ° C. and pelletized to prepare a resin composition. With respect to the resin composition thus obtained, general physical properties and blow properties were determined, and a pendulum test was performed to evaluate the performance. Table 4 shows the results. In addition,
The MI of the polypropylene blend in Example 4 is 0.7 g / 10 minutes. In Comparative Example 10, Xenoy1402B (manufactured by GE, trade name, polybutylene terephthalate / polycarbonate alloy) was used as the resin. In Comparative Example 11, Xenoy was used as the resin.
A recycled product of enoy 1402B was used. Further, in Example 8, the recycled product of Example 1 was used. About 60% by weight of parison
After the generated burrs were pelletized by a crusher, only the pellets were supplied to a blow molding machine.

[0029]

[Table 4]

Note 1) Comparative Examples 2 and 5 cannot be molded due to insufficient drawdown resistance. 2) In Comparative Example 1, molding was not possible due to insufficient drawdown resistance and deep drawability. 3) In Comparative Example 12, molding was impossible due to insufficient drawdown resistance.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for obtaining drawdown resistance.

FIG. 2 is a perspective view of a square bottle showing a test piece cutting point for obtaining a pinch-off strength.

FIG. 3 is an explanatory view of a three-point bending test for obtaining a pinch-off strength.

FIG. 4 is an explanatory diagram showing a center portion wall thickness and a corner portion wall thickness of a square bin for obtaining deep drawability.

FIG. 5 is an elevation view (a) and a plan view (b) when a bumper beam is attached to a vehicle body in order to perform 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 a bumper beam in a pendulum test.

FIG. 8 is a perspective view showing a broken state of a pinch-off portion of a bumper beam in a pendulum test.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Parison 2 Pinch-off part 3 Cut part of test piece in square bin 4 Cutting test piece 5 Bumper beam 6 Car body 7 Pendulum test machine 8 Impact ridge 9 Insert bottle 10 Crack generation part 11 Break generation part 12 Break of pinch-off part T Center part wall thickness T 'Corner thickness ΔD Upper rear displacement L ₀ Length of parison immediately after injection L Length of parison 15 seconds later

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-197541 (JP, A) JP-A-62-280252 (JP, A) JP-A-59-98157 (JP, A)

Claims (1)

(57) [Claims] (A) (a) a propylene homopolymer having an isotactic pentad fraction of 93% or more; and (b)
At least one selected from propylene-ethylene copolymers having an ethylene unit content of 15% by weight or less and an isotactic pentad fraction of 93% or more in a propylene homopolymerized part, and a melt index of 1.0 g; /
10 minutes or less of the polypropylene resin, and (a ') a melt index 0.1 g / 10 minutes or less, and _{A = Z 50 / Z 10 (} Z 10 and Z ₅₀ in the formula, measurement temperature 0.99 ° C., strain rate Each of the constant strain rate elongational viscosities of 0.05 sec ^-1
70-99% by weight of a resin mixture composed of high-density polyethylene having a parameter A defined in the range of 2 to 20 in the range of 2 to 20 seconds, and (b) an average particle diameter of 10 μm or less and an average aspect ratio of 3 to 20. A blow molding resin composition comprising 20 to 30% by weight of talc, and wherein the content of the component (a ') is not more than 30% by weight based on the total amount of the composition.