Note: Descriptions are shown in the official language in which they were submitted.
a~, ~-~--H- ; _ . 4 -- ~ ~ ~ 1~ 0~ ~5
1'~r''~'~'~ ~ r:-'~:1
DESCRIPTION
HIGHLY RIGID PROPYLENIC RESIN AND BLOW MOLDED
ARTICLE MADE THEREFROM
TECHNICAL FIELD
The present invention relates to a highly rigid
propylenic resin and a blow molded article made therefrom.
More particularly, it pertains to a highly rigid propylenic
resin which has favorable resistance to drawdown and can
produce a large sized and lightweight blow molded part being
excellent in rigidity, dimensional stability and heat
resistance and to a blow molded article obtained therefrom
which is particularly favorably usable for bumpers such as
bumpers and bumper beams for automobiles.
BACKGROUND ART
Polypropylene as a reisn for general purpose has
heretofore been molded into a product with a desirable form
and shape by any of various molding methods including
extrusion molding, injection molding and blow molding. Of
the above-mentioned molding methods, blow molding method has
found its extensive use in molding large-sized structural
materials typified by car parts because of its advantages in
that molds therefor are inexpensive and that the production
process can be simplified by integral molding methods. In
i:his case, propylenic resin is frequently and extensively
employed as raw materials from the viewpoint of specific
gravity, rigidity, dimensional stability, heat resistance and
the like.
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2~~0~~5
However, the propylenic resin for general purpose is not
necessarily sufficient in satisfying rigidity or resistance
to drawdown which is required in blow molding and thus,
various attemps have been made to improve such properties.
There is proposed for example, in Japanese Patent Publication
No. 36609/1988 (corresponding to U.S.P. No. 4550145), a
process for producing propylenic resin improved in drawdown
property by constituting a combination of propylene
homopolymer and propylene/ethylene copolymer at a specific
intrinsic viscosity and a specific compositional ratio.
However, such propylenic resin is not sufficient in rigidity
when made into a molding, and thus further improvement has
been desired. There are also disclosed a technique of
improving the rigidity thereof by means of multistage
polymerization and a nucleating agent (refer to Japanese
Patent Publication No. 74264/1991), a technique of improving
the resistance to drawdown thereof by means of specific
multistage polymerization and a specific nucleating agent
(refer to Japanese Patent Application Laid-Open No.
213547/1988) and the like technique.
However, although these techniques improve the rigidity
and resistance to drawdown of propylenic resin to some
extent, the problems still remain unsolved in that when an
attempt is made to form a so-called large-sized blow molded
part, that is, weighing about 5 kg or more, insufficiency in
resistance to drawdown makes molding itself impossible or
makes the thickness distribution ununiform, thus resulting in
failure to produce a satisfactory molded product. Such being
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217105
the case, the actual state is that in forming a large-sized
blow molded article weighing 5 kg or more, propylenic resin
is blended with polyethylene such as high density
polyethylene to contrive to solve the problem of drawdown.
Nevertheless, the blending of high density polyethylene
greatly lowers the rigidity of the blended resin, and
therefore, an inorganic filler such as talc is actually added
to the resin.
At any rate, the characteristics inherent in propylenic
resin are lost by blending polyethylene, talc or the like and
in particular, the disadvantage that the pinch-off strength
in blow molding is extremely lowered is caused thereby.
Accordingly, it is desired to realize a specific propylenic
resin capable of forming a large-sized blow molded article
and coping with increase in weight due to the blending of
talc. The above-mentioned problems should be solved in view
of not only the technical aspect but also the social
circumstances including the recycle of molded articles.
DISCLOSURE OF THE INVENTION
Under such circumstances, it is an object of the present
invention to develop a highly rigid propylenic resin which
has favorable resistance to drawdown and can produce a large
sized, lightweight blow-molded part being excellent in
rigidity, dimensional stability and heat resistance. It is
another object to provide a blow molded article composed
thereof which is favorably usable particularly for large-
sized car parts such as bumpers, bumper beams, seat back and
instrument panels.
- 3 -
~~~'~0~~5
In order to develop a highly rigid propylenic resin
having the favorable properties as mentioned above and a blow
molded article composed thereof, intensive research and
investigation were accumulated by the present inventors. As
a result, it has been found that the above-mentioned objects
can be attained by means of a propylenic resin, especially a
propylenic resin which is obtained through the formation of a
propylene polymer and a propylene/ethylene copolymer by
multistage polymerization, said resin having a melt index
within a specific range also having a specific relationship
between said melt index and the elongational viscosity
thereof. The present invention has been accomplished by the
foregoing finding and information.
That is to say, the present invention provides a highly
rigid propylenic resin, especially a highly rigid propylenic
resin which is obtained through the formation of a propylene
polymer and a propylene/ethylene copolymer by multistage
polymerization, said resin having a melt index [MI] in the
range of 0.1 to 1.2g/10 minutes as determined at a
temperature of 230°C under a load of 2,160 g and also
satisfying a relationship between the [MI] and the
elongational viscosity ~Y(Pa~s)~, said relationship being
represented by the expression
2.0 X 105 X MI 0'68 < Y < 8.0 X 105 X MI 0'68
THE MOST PREFERRED EMBODIMENT TO CARRY OUT THE INVENTION
It is indispensable in the propylenic resin according to
the present invention that the melt index [MI] determined at
a temperature of 230°C under a load of 2,160 g in accordance
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217105
with JIS K-7210, be in the range of 0.1 to 1.2g/10 minutes.
An MI value less than O.lg/10 minutes brings about a
remarkable decrease in the throughput quantity, thus
deteriorating the productivity of the resin, whereas that
more than 1.2g/10 minutes makes it impossible to form a
large-sized blow molded article. Taking moldability etc.
into consideration, the MI is preferably in the range of 0.2
to 1.0 g/10 minutes.
In addition, the propylenic resin according to the
present invention satisfies a relationship between the MI and
the elongational viscosity [Y(Pa~s)], said relationship being
represented by the expression
2.0 X 105 X MI 0'68 ~ Y ~ 8.0 X 105 X MI 0~68
preferably
2.3 X 105 X MI 0'68 < Y < 4.8 X 105 X MI 0~68
a Y value less than 2.0 X 105 X MI 0'68 results in
severe drawdown of a parison at the time of blow molding,
making it difficult to form a large-sized blow molded article
weighing 5 kg or more, whereas that more than 8.0 X 105 X
MI 0'68 leads to deterioration of the extrusion
characteristics as well as the external appearance of the
blow molded article.
The elongational viscosity [Y(Pa~s)] is measured with a
stretch rheometer (for example, produced by Iwamoto
Manufacturing Co., Ltd.) by the use of a bar sample with c.a.
3 mm diameter and 20 cm length by allowing the sample to
stand in a silicone oil at 175°C for 15 minutes under the
conditions including 175°C temperature, 0.05 sec 1 strain
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2171005
velocity and 2.0 strain.
The process for producing the propylenic resin according
to the present invention is not specifically limited provided
that the process is capable of producing a propylenic resin
which satisfies the above-mentioned conditions. There are
usable a variety of processes, of which is preferable a
process for producing a propylene polymer and a
propylene/ethylene copolymer by multistage polymerization.
As the favorable multistage polymerization method,
mention is made of a process in which through the use of a
stereoregular catalyst, propylene polymers each having a
different intrinsic viscosity [p] from one another are
produced in the first and second stages, and a
propylene/ethylene copolymer is produced in the third stage.
Examples of the aforesaid stereoregular catalyst to be
used for the multistage polymerization include a catalyst
comprising a halogenide of a transition metal, an
organoaluminum compound and a substance to be added for
preparing a polymer having improved stereoregularity and a
broad molecular weight distribution such as a lactone.
Examples of the halogenide of a transition metal
preferably include halogenides of titanium, of which titanium
trichloride is particularly preferable. The titanium
trichloride is exemplified by that prepared by reducing
titanium tetrachloride through any of various methods; that
prepared by further activating the preceding titanium
tetrachloride through any of various methods; that prepared
by further activating the preceding titanium trichloride by
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217105
means of a treatment in a ball mill and/or solvent cleaning
(for example, cleaning with an inert solvent or an inert
solvent containing a polar compound); and that prepared by
subjecting titanium trichloride or a titanium trichloride
eutectic such as TiC13.1/3 A1C13 to a crushing treatment
together with an amine, an ether, an ester, sulfur, a halogen
derivative or an organic or inorganic nitrogen or phosphorus
compound. There is also usable a halogenide of titanium
supported on a magnesium-based carrier.
Examples of the organoaluminum compound include a
compound represented by the general formula (I)
AlRnX3-n (I)
wherein R is an alkyl group having 1 to 10 carbon atoms, X is
a halogen atom, and n is a number satisfying 0 ~ n< 3.
Specific examples of such organoaluminum compound
include dimethylaluminum chloride, diethylaluminum chloride,
ethylaluminum sesquichloride, ethylaluminum dichloride and
triethylaluminum. The organoaluminum compound may be used
alone or in combination with at least one other. It is used
in an amount of usually 1 to 100 moles per one mole of the
above-mentioned halogenide of a transition metal.
Example of lactones include a compound represented by
the general formula (II)
2171005
R
I
C
I
. . . (II)
0 C=0
wherein Rl arid R2 are each a hvdroaPn atom nr a hvc3rn~-arhnn
group having at most 20 carbon atoms and belonging to
saturated aliphatic series, unsaturated aliphatic series,
alicylic series or aromatic series, and may be the same as or
different from each other, and m is an integer from 2 to 8.
As the lactone of the general formula (II), mention is
made of Y-lactons such as Y- butyroloctone, Y-valerolactone,
Y-caproloctone, Y-capryloctone, Y-laurolactone, Y-
palmilactone, Y-stearolacton; d-lactones such as d-
valerolactone and s-caproloctone; e-lactons such as e-
caprolactone; and ~-loctones such as S-propiolactone and
dimethylpropiolactone. Of these lactones, Y-loctones and e-
lactones are preferable, and Y-butyrolactone, Y-caprolactone
and ~-caproloctone are particularly preferable. Any of these
lactones may be used alone or in combination with at least
one other. It is used in an amount of usually 0.01 to 10
moles per one mole of the above-mentioned halogenide of a
transition metal.
In the foregoing multistage polymerizaiton, it is
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217105
preferable in the first stage to carry out the polymerizaiton
of propylene at a temperature of 50 to 70°C so as to produce
a propylene polymer having an intrinsic viscosity Vin] of 0.5
to 3.5 dL (deciliter)/g (in decalin, 135°C) in an proportion
of 60 to 80$ by weight based on the whole amount of the
polymer. An intrinsic viscosity [~] of the propylene polymer
less than 0.5 dL/g brings about a low impact strength of the
propylenic resin to be produced, whereas that more than 3.5
dL/g causes a decrease in throughput quantity of the resin at
the time of blow molding, in certain cases. A proportion of
the polymer produced in the first stage less than 60$ by
weight results in insufficient rigidity of the propylenic
resin to be produced, whereas that more than 80$ by weight
gives rise to deterioration of the impact strength thereof,
in certain cases.
Next, it is preferable in the second stage to carry out
the polymerization of propylene at a temperature of 50 to
70°C so as to produce a propylene polymer having an intrinsic
viscosity Vin] of 3.5 to 5.5 dL/g (in decalin, 135°C) in a
proportion of 10 to 20% by weight based on the whole amount
of the polymer. An intrinsic viscosity Vin] of the propylene
polymer less than 3.5 dL/g brings about a low impact strength
of the propylenic resin to be produced, whereas that more
than 5.5 dL/g causes a decrease in throughput quantity of the
resin at the time of blow molding, in certain cases. A
proportion of the polymer produced in the second stage less
than 10$ by weight results in insufficient rigidity of the
propylenic resin to be produced, whereas that more than 20$
_ g _
~1~1~~
by weight gives rise to deterioration of the impact strength
thereof, in certain cases.
Moreover, it is preferable in the third step to carry
out the copolymerization of propylene and ethylene at a
temperature of 45 to 65°C so as to produce a
propylene/ethylene copolymer having an intrinsic viscosity
of 3.5 to 5.5 dL/g (in decalin, 135°C) and an ethylene
unit content of 40 to 75a by weight in a proportion of 8 to
15$ by weight based on the total amount of the polymer. An
intrinsic visocisity f~~ of the propylene/ethylene copolymer
of less than 3.5 dL/g brings about a low impact strength of
the propylenic resin to be produced, whereas that more than
5.5 dL/g causes a decrease in throughput quantity of the
resin at the time of blow molding, in certain cases. A
proportion of the copolymer produced in the third stage less
than 8$ by weight results in a low impact strength of the
propylenic resin to be produced, whereas that more than 15~
by weight gives rise to deterioration of the rigidity
thereof, in certain cases. An ethylene unit content of less
than 40$ by weight in the copolymer results in a low impact
strength of the propylenic resin to be produced, whereas that
of more than 60$ by weight leads to deterioration of the
rigidity, in certain cases. The ethylene unit content in the
copolymer can be obtained by measuring infrared absorption
spectrum.
The modulation for the intrinsic viscosity Vin] of the
polymer in each of the stages can be carried out, for
example, by properly altering the concentration of a
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_. 2 i 710 ~ 5
molecular weight modulator such as hydrogen. The pressure in
the polymerization reaction is selected in each stage in the
range of usually atmospheric pressure to 30 kg/cm2G,
preferably 1 to 15 kg/cm2G.
As the polymerization system, there are applicable a
continuous method by using at least three polymerization
vessels, a batchwise method by using at least one
polymerization vessel and a method by the combination of the
above-mentioned continuous method and batchwise method. As
the polymerization method, there are adoptable, without
specific limitation, suspension polymerization, solution
polymerization, gas-phase polymerization or the like.
As a solvent, when used, mention is made of an aliphatic
hydrocarbon such as heptane and hexane, an alicyclic
hydrocarbon such as cyclohexane and an aromatic hydrocarbon
such as benzene and toluene. Any of the solvents may be used
alone or in combination with at least one other.
The propylenic resin thus obtained according to the
present invention has favorable resistance to drawdown and
can afford a large-sized blow molded part which is
lightweight and excellent in rigidity, dimensional stability
and heat resistance.
The blow molded article according to the present
invention is produced through the blow molding of the above-
mentioned propylenic resin by blending therewith as desired,
any of additives such as soft elastomer, modified polyolefin,
antioxidant, heat resistant stabilizer, weather resistance
stabilizer, inorganic or organic filler, nucleating agent,
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2171005
antistatic agent, chlorine scavenger, slip agent, flame
retardant and coloring agent. As the blow molding method,
there is usable, without specific limitation, a method which
has been customarily employed in the blow molding of
propylenic resin.
In comparison with the blow molded article produced by
blow molding the polypropylene blended with a large amount of
an inorganic filler such as talc which has heretofore been
used in general, the blow molded article according to the
present invention is lightweight and excellent in rigidity,
dimensional stability and heat resistance, and is preferably
used particularly for bumpers including car bumpers and car
bumper beams.
In the following, the present invention will be
described in more detail with reference to examples, which
however, shall not be construed to limit the present
invention thereto.
Determinations were made of the melt index [MI ]and
elongational viscosity [Y ]of the propylenic resin by the
methods described herein, of the ethylene unit content by
measuring the infrared absorption spectrum, of the tensile
modulus according to JIS K7113, and of the Izod impact value
(at -20°C) according to JIS K7110.
The intrinsic viscosity [r~] of the polymer in each of
the stages is that measured in decalin at 135°C.
Example 1
A 10 L (liter) autoclave equipped with a stirrer was
charged with 4L of n-heptane, 5.7 mmol of diethylaluminum
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ziooo5
chloride, 0.7g of titanium trichloride and 0.2 mL
(milliliter) of e-caprolactone.
Thereafter, the autoclave was continuously fed with
hydrogen which had been weighed so as to attain a prescribed
intrinsic viscosity ~n~ of the propylene polymer to be
produced and with propylene so as to attain a reaction
pressure of 9 kg/cm2G, while the liquid-phase temperature was
maintained at 60°C, to carry out the first stage reaction
under stirring for 90 minutes. Subsequently, the unreacted
propylene was removed, and hydrogen thus weighed along with
propylene were continuously fed in the autoclave so as to
attain a reaction pressure of 7 kg/cm2G, while the
temperature therein was maintained at 60°C, to carry out the
second stage reaction for 40 minutes.
Further, the mixture of propylene and ethylene and
hydrogen thus weighed were continuously fed in the autoclave
so as to attain a reaction pressure of 5 kg/cm2G, while the
temperature therein was maintained at 57°C, to carry out the
third stage reaction for 30 minutes.
To the resultant polymerization product was added n-
butanol, and the mixture was stirred at 65°C for one hour to
decompose the catalyst and was subjected to the steps of
separation, cleaning and drying with the result that
propylenic resin in the form of white powder was obtained.
The intrinsic viscosity [r~~ and the polymerization
amount of the polymer obtained in each of the polymerization
stages are given in Table 1. Further, the physical
properties of the objective propylenic resin are given in
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~I~~~
Table 2.
Example 2
The procedure in Example 1 was repeated to carry out the
polymerization except that the intrinsic viscosity (p] and
the polymerization amount of the polymer obtained in each of
the polymerization stages were altered as shown in Table 1.
The results obtained are given in Table 2.
Example 3
The procedure in Example 1 was repeated to carry out the
polymerization except that the intrinsic viscosity [r~] and
the polymerizaiton amount of the polymer otained in each of
the polymerization stages were altered as shown in Table 1.
The results obtained are given in Table 2.
Example 4
To the polymer which had been obtained in Example 1 was
added 0.1$ by weight of sodium salt of methylenebis(2,4-di-
tert-butylphenol)acid phosphate as the nucleating agent to
form a propylenic resin. The physical properties thereof are
given in Table 2.
Comparative Examples 1 & 2
A 10 L(liter) autoclave equipped with a stirrer was
charged with 5 L of dehydrated n-hexane, 1.0 g of
diethylaluminum chloride and 0.3 g of titanium trichloride.
Thereafter, the autoclave was continuously fed with
hydrogen which had been weighed so as to attain a prescribed
intrinsic viscosity ~n~ of the propylene polymer to be
produced and with propylene so as to attain a reaction
pressure of 9 kg/cm2G, while the liquid-phase temperature was
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2171005
maintained at 65°C, to carry out the first stage reaction
under stirring for 90 minutes. Subsequently, the unreacted
propylene was removed, and the liquid-phase temperature was
lowered to 50°C.
Then, hydrogen thus weighed along with propylene were
continuously fed in the autoclave so as to maintain a
reaction pressure of 9 kg/cm2G, and a reaction temperature of
50°C, to carry out the second stage reaction for 40 minutes.
Further, the mixture of propylene and ethylene and
hydrogen thus weighed were continuously fed in the autoclave
so as to attain a reaction pressure of 9 kg/cm2G, while the
temperature therein was maintained at 50°C, to carry out the
third stage reaction for 30 minutes. Then, the unreacted gas
was removed, and to the resultant polymerization product was
added n-butanol, and the mixture was stirred at 65°C for one
hour to decompose the catalyst and was subjected to the steps
of separation, cleaning and drying with result that a polymer
in the form of white powder was obtained.
The polymerization was carried out by altering the
intrinsic viscosity fry] and the polymerization amount of the
polymer in each of the polymerization stages as given in
Table 1. Further, the physical properties of the objective
polypropylenic resin are given in Table 2.
Comparative Example 3
The procedure in Example 1 was repeated to carry out the
polymerization except that the addition of e-caprolactone as
the catalyst was omitted. The intrinsic viscosity [r~] and
the polymerization amount of the polymer in each of the
- 15 -
z~oo~~
polymerization stages are given in Table 1, and the physical
properties of the objective propylenic resin are given in
Table 2.
Comparative Example 4
The procedure in Example 1 was repeated to carry out the
polymerization except that the intrinsic viscosity [n] and
the polymerization amount of the polymer obtained in each of
the polymerization stages were altered as shown in Table 1.
The results obtained are given in Table 2.
Comparative Example 5
The procedure in Example 1 was repeated to carry out the
polymerization except that the polymerization was performed
in two stages instead of three stages and instead, the
polymerization amount in the first stage was increased. The
instrinsic viscosity [n7 and the polymerization amount of the
polymer in each of the polymerization stages are given in
Table 1, and the physical properties of the objective
propylenic resin are given in Table 2.
Comparative Example 6
The mixture having the under-mentioned composition was
incorporated with a prescribed antioxidant and thereafter was
kneaded by the use of a bidirectional twin-screw kneader
(produced by Kobe Steel Ltd., model 2FCM) at a temperature
set to 200°C at a number of screw revolutions of 800 r.p.m,
while the temperature of the resulting melt was 250°C. The
kneaded product was formed into strands by means of an
extruder, and then granulated with a pelletizer to produce a
composite material for bumper beam. The results of the
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217100
measurement of the physical properties are given in Table 2.
Polypropylene (ethylene unit content . 5o by weight,
MI . 0.9g/10 minutes)
70o by weight
High density polyethylene (HLMI . 3.8 g/10 minutes)
20% by weight
Talc 10$ by weight
where HLMI indicates MI (melt index) measured under the
conditions of 190°C temperature and 21.6 kg load.
Table 1
First Second Third
stage stage stage
polymerization polymerization polymerization
f n amount f r~ amount f n amount
l (~ by weight)1 (~ by weight)1 (~ by weight)
Example 3. 74 4. 14 4. 12
1 0 5 5
Example 2.4 74 4.5 12 4.8 14
2
Example 2.4 75 4.0 16 4.2 9
3
Examp 3. 74 4. 14 4. 12
1 a 4 0 5 5
Comp.
Examp 2. 76 5. 10 4. 14
1 a 1 9 9 6
Comp.
Examp 2. 78 7. 12 9. 10
1 a 2 4 2 4
Comp.
Examp 3. 75 4. 13 4. 12
1 a 3 0 3 5
Comp.
Examp 1. 78 4. 12 5. 10
1 a 4 5 8 3
Comp.
Examp 3. 89 - - 4. 11
1 a 5 4 2
Remarks: Comp. =Comparative
- 17 -
z ~ o ~~
Table2-1
Physical properties
of propylenic
resin
ethylene unit contentM I
((Y by weight) (g/10 minutes)
Examp 6. 0 0. 30
1 a 1
Example 6. 3 0. 60
2
Examp 6. 3 0. 80
1 a 3
Examp 6. 0 0. 30
1 a 4
Comp.
Examp 2. 9 0. 27
1 a 1
Comp.
Examp 6. 2 0. 36
1 a 2
Comp.
Examp 6. 0 0. 30
1 a 3
Comp.
Examp 4. 7 8. 50
1 a 4
Comp.
Examp 5. 3 0. 30
1 a 5
- is -
Table2-2
Physical properties
of propylenic
resin
Tensile modulusIzod impact elongational
value
(M P a ) at -20 C viscosity
Y
(kJ/m2 ) (Pa ~ s)
Example 1, 490 3.7 6.5x10 5
1
Example 1, 400 4.4 4.2x10 5
2
Example l, 520 3. 2 2. 8 X 10
3 5
Example 1, 650 3. 9 6. 8 X 10
4 5
Comp.
Examp 1, 600 3. 0 4. 2 X 10
1 a 1 5
Comp.
Examp 1. 500 3. 5 2. 8 x 10
1 a 2 5
Comp.
Examp 1. 380 3. 6 4. 0 x 10
1 a 3 5
Comp. no t
Example 1.580 3.4 measurable
4
Comp.
Exampla 1, 450 3. 9 3.1 x 10
5
Comp.
Example 1, 500 3. 5 2. 8 X 10
6 5
Examples 5 to 8 and Comparative Examples 7 to 12
Each of the propylenic resins obtained by means of scale
up and in accordance with the conditions in Examples 1 to 4
and Comparative Examples 1 to 6, respectively, was molded
into a car bumper beam (1400 X 100 X 100 mm in size and 5 kg
in weight) and a truck bumper (2100 X 400 X 70 mm in size and
7.2 kg in weight) under the molding conditions and
temperature conditions as desribed hereunder, except that
the truck bumper was produced only in Example 8.
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21710
(Molding conditions)
molding machine . 90 mm in diameter
screw . 90 mm in diameter
die . 100 mm in diameter
accumulator . 15 liter (car bumper beam)
25 liter (truck bumper)
mold clamping force . 60 ton
number of screw revolutions . 40 r.p.m,
electric motor load . 115 A
(Temperature conditions)
cylinder No. 1 . 230°C
No. 2 . 210°C
No. 3 . 190°C
No. 4 . 190°C
crosshead No. 1 190C
.
No. 2 190C
.
No. 3 190C
.
die No. 1 190C
.
No. 2 190C
.
molding cycle . 200 sec
mold temperature . 28°C
resin temperature . 225°C
Investigations were made of (1) moldability, (2)
thickness distribution and appearance, (3) product rigidity,
(4) throughput quantity, (5) pinch-off strength and (6)
impact resistance for each of the car bumper beams and truck
bumpers produced in the aforesaid manners, and overall
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21710~~
evaluations were carried out based on the investigation
results. The evaluation results are given in Tables 3 to 5,
in which Table 3 gives the results obtained in Example 8
only, while Tables 4 and 5 give the results obtained in the
production of car bumper beams.
The measurement and evaluation in each of the
investigation items were carried out according to the
following standards.
(1) Moldability
Propylenic resin for a bumper beam parison with
necessary leangth/weight of 1900 mm/10 kg and that for a
bumper parison with necessary length/ weight of 2600 mm/15 kg
were each injected from an accumulator to form a parison.
The moldability was evaluated by the variation in the length
of the parison during 5 seconds, that is, the mold closing
time.
L/Lo < 1.10 ~ Good
1.10 ~ L/Lo ~ 1.15 0 Fair
L/Lo > 1. 15 ~ Poor
where, Lo . parison length at the end of injection
L . parison length after 5 seconds from the end
of injection
(2) Thickness distribution
Thickness distribution was evaluated by measuring the
thickness of each of the cross sections of the blow molded
article.
Variation in thickness < l00 ~o Good
- 21 -
Variation in thickness > 10%, ~ 200 ~ Fair
Variation in thickness > 20% x Poor
(3) Product rigidity (rigidity for dishing at 100 kg)
Product rigidity was evaluated by comparing its
distorsion with that of a steel-made product.
3 mm in distortion (same as or smaller than the
distortion of the steel-made)
> 3 mm in distortion (larger than the distortion
of the steel-made)
(4) throughput performance
Throughput performance was evaluated by measuring the
throughput quantity per one hour by the use of a blow molding
machine of 90 mm in diameter, and by comparing the throughput
quantity thus measured with that of the composite material
used in Comparative Example 6.
Superior to the composite material
Comparable to the composite material
(5) Pinch-off strength
In the production of a blow molded article, a fusing
adhesion part which is called pinch-off part is formed at the
time of mold closing by the fusing adhesion of the inside of
a parison with each other. The pinch-off part is apt to
become a starting point of rupture or break, and thus a
structural part and a part requiring strength are needed to
be improved in the fusing adhesivity of the pinch-off part.
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2i 7i 0~5
Accordingly, the fusing adhesivity of the pinch-off part was
evaluated by the following procedure.
By the use of each of the resins that had been obtained
in Example 4 and Comparative Examples 6, a bottle having a
prescribed shape was prepared by blow molding, and a strip
test piece with 20 mm width was cut out from the bottom of
the bottle so as to include the pinch-off in the width
direction. The test piece thus obtained was notched with a
notching blade of 2.0 mm in R at both the ends of the pinch-
off part so that the pinch-off part had 10 mm width. The
test piece was tested at a tensile velocity of 50 mm/minute
by the use of a tensile test machine (produced by INSTRON
Corp. in U.S.A under the tradename INSTRON 1125). The yield
strength and rupture energy were regarded as the index of the
pinch-off strength. Specifically, the enhancement of the
fusing adhesivity increases with an increase in each of the
foregoing values. The yield strength is represented by the
maximum stress value in the stress strain diagram, while the
rupture energy is represented by the the product [(stress) x
(strain) which is obtained by integrating the stress with
respect to the strain from zero to the rupture point in the
range of the strain. For the sake of simplicity, the rupture
energy can be shown by the area which is surrounded by the
stress strain diagram and the abscissa.
(6) Impact resistance
A bumper beam which had been obtained by blow molding
each of the resins as obtined in Example 4 and Comparative
Example 6 was subjected to pendulum test in accordance with
- 23 -
Federal Motor Vehicle Safety Standards (abbreviated to FMVSS)
PART 581. Specifically, the bumper beam was fitted to a
bogie of 1000 kg in weight, and an impact ridge of 1000 kg in
weight was allowed to collide with the bumper beam at a
velocity of 5 miles/hour (about 8 km/hour) to obtain the
relation between the generated load and the distortion size
of the beam, while the place of the collision was made to the
central part of the beam. The test temperatures were each
set to a high temperature (50°C), ordinary temperature (23°C)
and a low temperature (-10°C and -30°C) taking into
consideration of the conditions under which the bumper beam
is mounted on a commercial car. The evaluation was carried
out by the maximum distortion and the occurrence of crack.
Table3
Ca.r bumper beam Truck bumper
Parison length1, 900 mn 2, 600 mm
Parison weight10 kg 15 kg
Product length1, 400 mn 2,100 mn
Product weight5 kg 7.2 kg
Moldabi 1 1. 06 1. 09
i ty
Thickness Thickness Thickness
distributionvariation < 109 variation < 10~
Rigidity Distortion: littleDistortion: little
Impact
resistance Abnormality: noneAbnormality:
none
Overall
evaluation good good
- 24 -
2171 ~~~
Table 4-1
Resin MoldabilityThickness External
used L/Lo dis appearance"
~~ution
~
0
Example Example 1.07 7
1 O O O
Example Example 1.10 15
6
2 O O O
Example Example 1.15 18
7
3 O O O
Example Example 1.06 6
8
4 O O O
Comp. Comp. 1.15 20
Example Example O D O
7 1
Comp. Comp. 1.20 22
Example Example x x O
8 2
Comp. Comp. 1.17 22
Example Example O x O
9 3
Comp. Comp. - _ _
Example Example x x x
4
Comp. Comp. 1.20 25 D
Example Example x x
11 5
Comp. Comp. 1.14 20
Example Example O O O
12 6
* 1 External appearance
O: Wrinkle or strain being hardly observed
D: Wrinkle or strain being caused to some extent
- 25 -
2171005
Table 4-2
Productthroughput Overall
~2
rigidityperformanceevaluation
Example
5
0 0 0
Example
6
O o0 O
Example
7
0 0 0
Example
8
O O O
Comp.
Exa,mp O O O
1 a 7
Comp.
Example O O
8
Comp.
Example X O D
9
Comp.
Example - 00 x
10
Comp.
Example O O x
11
Comp.
Example O O D
12
* 2 Overall
evaluation
Oo : Fully satisfying product performance requirement
O: Satisfying product performance requirement
D: Somewhat inferior to aimed product performance
x : Greatly inferior to aimed product performance
- 26 -
Table 5
Example Example 12
8
Pinch Yield strength 7 2 4 3
-of (kgf )
f
h
strengt
Rupture 9 4 9. 0
energy
(kgf ~ mn)
high maximum 5 5 7 3
temperaturedistortion
(50 C) (mm)
crack - -
P
d
l
en
u
um
test ordinary maximum 5 5 7 3
temperaturedistortion
(mn)
(23 C) crack - -
low maximum 3 8 3 7
temperaturedistortion
(-10C) (mn)
crack - -
(-30C) maximum 3 6 not
distortion measurable
(mn)
- Remarkably
crack damaged from
pinch-off
fusion
part as starting
point
In the overall evaluation in Table 4, the results of
pinch-off strength and impact resistance were taken into
consideration as well.
In addition, it has been demonstrated in Table 5 that
the yield strength in Example 8 is about 1.7 times that in
Comparative Example 12 and the fusing adhesivity in Example 8
expressed in terms of rupture energy is about 10 times that
in Comparative Example 12. It is thought that the
manifestation of the excellent impact resistant in the
- 27 -
21 l 10~~ 0 5
pendulum test in Example 8 is due to the remarkable
improvement in the fusing adhesivity of the pinch-off part.
INDUSTRIAL APPLICABILITY
The blow molded articles obtained from the highly rigid
propylenic resin according to the present invention are
favorably usable particularly for large-sized car parts such
as bumpers, bumper beams, seat back and instrument panels.
- 28 -
