U.S. patent application number 10/512583 was filed with the patent office on 2006-03-16 for polymer for fuel tanks.
Invention is credited to Michel Walter Ghislain Lequeux, Francois Neuray, Fabian Siberdt.
Application Number | 20060054513 10/512583 |
Document ID | / |
Family ID | 28685979 |
Filed Date | 2006-03-16 |
United States Patent
Application |
20060054513 |
Kind Code |
A1 |
Lequeux; Michel Walter Ghislain ;
et al. |
March 16, 2006 |
Polymer for fuel tanks
Abstract
A fuel tank for a vehicle is disclosed, comprising at least one
component which is blow-moulded multimodal poly-ethylene having a
polydispersity M.sub.w/M.sub.n of at least 4, formed of at least
two blocks, each having a polydispersity M.sub.w/M.sub.n of less
than 4.
Inventors: |
Lequeux; Michel Walter
Ghislain; (Brussels, BE) ; Neuray; Francois;
(Vise, BE) ; Siberdt; Fabian; (Brussels,
BE) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER;LLP
901 NEW YORK AVENUE, NW
WASHINGTON
DC
20001-4413
US
|
Family ID: |
28685979 |
Appl. No.: |
10/512583 |
Filed: |
April 10, 2003 |
PCT Filed: |
April 10, 2003 |
PCT NO: |
PCT/EP03/03791 |
371 Date: |
October 26, 2004 |
Current U.S.
Class: |
206/.6 ;
264/454 |
Current CPC
Class: |
C08F 210/16 20130101;
B60K 15/03177 20130101; C08F 110/02 20130101; C08F 2500/01
20130101; C08F 210/14 20130101; C08F 2500/19 20130101; C08F 2500/19
20130101; C08F 2500/07 20130101; C08F 2500/04 20130101; C08F
2500/13 20130101; C08F 2500/13 20130101; C08L 23/0815 20130101;
C08L 53/00 20130101; C08F 110/02 20130101; C08F 297/083 20130101;
C08L 23/0815 20130101; C08L 23/06 20130101; C08L 2666/06 20130101;
C08F 2500/12 20130101; C08L 2666/06 20130101; C08F 2500/04
20130101; C08F 2500/12 20130101; C08F 10/02 20130101; C08L 2666/02
20130101; C08L 53/00 20130101; C08L 23/06 20130101; C08F 210/16
20130101; C08F 2500/02 20130101 |
Class at
Publication: |
206/000.6 ;
264/454 |
International
Class: |
B65B 3/00 20060101
B65B003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 26, 2002 |
EP |
02077189.5 |
Claims
1. Fuel tank for a vehicle comprising at least one component which
is a blow-moulded multimodal polyethylene resin having a
polydispersity M.sub.w/M.sub.n of at least 4, formed of at least
two blocks, each having a polydispersity M.sub.w/M.sub.n of less
than 4.
2. Fuel tank for a vehicle comprising at least one component which
is a blow-moulded multimodal polyethylene resin, wherein the
polyethylene has a creep deformation at 80.degree. C. of no more
than 2.4%, and a Charpy impact at -40.degree. C. of at least 15
kJ/m.sup.2.
3. Fuel tank according to claim 2, wherein the polyethylene resin
has a creep resistance at 80.degree. C. of no more than 2.3%.
4. Fuel tank according to claim 2 or 3, wherein the polyethylene
resin has a Charpy impact at -40.degree. C. of at least 20
kJ/m.sup.2.
5. Fuel tank according to claim 1, wherein the polyethylene resin
is bimodal.
6. Fuel tank according to claim 1, wherein the polydispersity of
the polyethylene resin is at least 5.
7. Fuel tank according to claim 1, wherein an unformulated
polyethylene resin, before the incorporation of any additives, has
a density of from 930 to 965 kg/m.sup.3.
8. Fuel tank according to claim 1, wherein a high load melt index
(HLMI) of the polyethylene resin is between 2 and 7 g/10 min.
9. Fuel tank according to claim 1, wherein .mu..sub.0 of the
polyethylene resin, the viscosity at a shear rate of 1 s.sup.-1
with a conical die having a ratio of length to internal diameter of
0.3:1, is at least 2.5.times.10.sup.6 dPa.s.
10. Fuel tank according to claim 1, wherein of the polyethylene
resin is bimodal and comprises 20-80% of a high molecular weight
block, and 70-30% of a low molecular weight block.
11. Fuel tank according to claim 10, wherein the low molecular
weight block is a homopolymer of ethylene.
12. Fuel tank according to claim 10, wherein the high molecular
weight block is a copolymer of ethylene and one or more of butene,
pentene, hexene and octene.
13. Fuel tank according to any one of claims 10 to 12, wherein the
Melt Index (MI.sub.2) of the low molecular weight block is less
than 500.
14. Fuel tank according to claim 10, wherein the high load melt
index (HLMI) of the high molecular weight block is between 0.001
and 2.
15. Fuel tank according to claim 10, wherein at least the high
molecular weight block of the polyethylene resin is made using a
metallocene catalyst, and the polydispersity of the polyethylene
resin is between 5 and 9.
16. Fuel tank according to claim 15, wherein both blocks of the
polyethylene resin are made using a metallocene catalyst.
17. Fuel tank according to claim 1, wherein the polyethylene resin
is made using a Ziegler-Natta catalyst, and the polydispersity
thereof is between 10 and 18.
Description
[0001] The present invention relates to an automobile fuel tank
comprising polyethylene and to the manufacture of such a tank.
[0002] Automobile fuel tanks comprising high density polyethylene
are known. Such fuel tanks are required to exhibit high safety
performance, particularly with regard to fire resistance and impact
resistance. They are required to meet minimum statutory industry
specified performance criteria both with respect to creep
resistance when the tank is subjected to a fire, and crash test
resistance when the tank is subjected to an impact. An automobile
fuel tank for use in Europe is required to have a fire resistance
and an impact resistance both complying with the respective
standards defined in ECE34, Annex 5. In order to meet these
standards, known blow moulded automobile fuel tanks are required to
have a minimum wall thickness of at least 3 mm so as to provide
sufficient impact strength and creep resistance for the fuel tank
as a whole. An automobile fuel tank composed of polyethylene
typically has a volume of up to about 100 litres, or even greater.
Given the requirement for such volumes in combination with the need
for progressively lower wall thicknesses, this places a high demand
on the physical properties of the walls of the tank, both following
manufacture and when used. Thus the walls of the fuel tank are
required not to warp or shrink following the manufacture thereof,
and are required to have a precisely defined shape and rigidity
during use. Accordingly a fuel tank is required to have a good
environmental stress crack resistance, good creep resistance and
also good impact resistance.
[0003] JP 06172594 discloses a polyethylene composition suitable
for blow-moulding into a gasoline tank, which comprises a blend of
a high molecular weight polymer and a low molecular weight polymer
made using a Ziegler catalyst. Ziegler catalysts have a variable
comonomer content with molecular weight, and a usually have a broad
molecular weight distribution, generally significantly greater than
4.
[0004] WO 97/02294 and WO 95/11264 both discloses a bimodal HDPE
resin in which the low molecular weight component is produced using
a metallocene catalyst, and the high molecular weight component
produced using a non-metallocene catalyst. Although the resins a re
intended for use as films, they are said to be suitable for
blow-moulding into containers a fuel tank is given as one example
of a container. However no indication is given as to whether the
physical property requirements for automobile fuel tanks discussed
above would be satisfied by this resin. The non-metallocene part of
the catalyst can be expected to produce a high molecular weight
component having a variable comonomer content with molecular
weight, and also a broad molecular weight distribution, probably
greater than 4. This would be expected to result in a resin having
poor impact properties.
[0005] We have found that it is possible to obtain blow-moulded
vehicle fuel tanks having improved properties with a polyethylene
prepared using a multimodal catalyst which produces individual
blocks having a relatively narrow molecular weight
distribution.
[0006] Accordingly in a first aspect, the present invention
provides a fuel tank for a vehicle comprising at least one
component which is blow-moulded multimodal polyethylene having a
polydispersity M.sub.w/M.sub.n of at least 4, formed of at least
two blocks, each having a polydispersity M.sub.w/M.sub.n of less
than 4. Preferably the blow-moulded component forms one or more of
the walls of the tank. By "multimodal" polyethylene is meant
polyethylene having at least two components of different molecular
weights and compositions (ie comonomer content).
[0007] The polydispersity of the injection-moulded multimodal
polyethylene is preferably no greater than 35, more preferably no
greater than 20. The most preferred range is 4-20.
[0008] In a second aspect, the invention provides a fuel tank for a
vehicle comprising at least one component which is blow-moulded
multimodal polyethylene, wherein the polyethylene has a creep
deformation at 80.degree. C. of no more than 2.4%, and a Charpy
impact at -40.degree. C. of at least 15 kJ/m.sup.2. Preferably the
polyethylene has a creep resistance at 80.degree. C. of no more
than 2.3%; preferably it has a Charpy impact at -40.degree. C. of
at least 20 kJ/m.sup.2.
[0009] In this specification, Charpy impact is defined as the
impact as assessed by notched Charpy tests performed at -40.degree.
C. on specimens taken from 4 mm compressed plates according to
ISO179/1EA. Creep resistance is defined as that assessed by tensile
strength measurements preformed at 80.degree. C. under 2.5 Mpa on
ISOB1A specimens machined from 2 mm thick compressed plates.
[0010] The polyethylene is preferably bimodal: by "bimodal" is
meant two components of different molecular weights, one having a
higher relative molecular weight than the other of the two
components and compositions (ie comonomer content).
[0011] The unformulated polyethylene resin, before the
incorporation of any additives, preferably has a density of from
930 to 965 kg/m.sup.3. If following injection moulding the density
is lower than 930 kg/m.sup.3, then the creep resistance of the
component may be insufficient for use in an automobile fuel tank.
If the density is higher than 965 kg/m.sup.3, then the walls of the
tank may be too brittle, resulting in insufficient impact
resistance and toughness. In this specification, the density of the
polyethylene is measured according to ISO 1183. Resins used in fuel
tanks typically contain about 0.5wt % of carbon black, which
increases the density compared with unformulated resin by less than
1 kg/m.sup.3.
[0012] The high load melt index (HLMI) of the resin is preferably
between 1 and 10, more preferably between 2 and 7 g/10 min. HLMI is
measured using the procedures of ASTM D 1238 at 190.degree. C.
using a load of 21.6 kg.
[0013] For blow-moulding, an important parameter of the resin is
its viscosity at low shear rate. Accordingly it is preferred that
the value of .mu..sub.0, the viscosity at a shear rate of 1
s.sup.-1, with a conical die having a ratio of length to internal
diameter of 0.3:1, is at least 2.5.times.10.sup.6 dPa.s, preferably
at least 3.times.10.sup.6 dPa.s.
[0014] The bimodal polyethylene preferably comprises 20-80% of a
high molecular weight block, and 70-30% of a low molecular weight
block. Most preferred is 35-65% of the high molecular weight block,
and 65-35% of the low molecular weight block. The low molecular
weight block is preferably a homopolymer of ethylene, but may also
be a copolymer. The high molecular weight block is preferably a
copolymer of ethylene and one or more of butene, pentene, hexene
and octene. The Melt Index (MI.sub.2) of the low molecular weight
block is preferably less than 500, more preferably less than 100
g/10 min. MI.sub.2 is measured using the procedures of ASTM D 1238
at 190.degree. C. using a load of 21.6 kg. The HLMI of high
molecular weight block is preferably between 0.001 and 2, more
preferably between 0.01 and 0.7; its density is preferably less
than 950, more preferably less than 940 kg/m.sup.3.
[0015] The polyethylene resin utilised in the present invention may
be made using a Ziegler-Natta catalyst. In such a case, the
Ziegler-Natta catalyst should be one capable of producing
individual blocks having polydispersities of less than 4. The
polydispersity of overall resin in such a case is preferably
between 10 and 18. Ziegler-Natta catalysts typically consist of two
main components. One component is an alkyl or hydride of a Group I
to III metal, most commonly Al(Et).sub.3 or Al(iBu).sub.3 or
Al(Et).sub.2Cl but also encompassing Grignard reagents,
n-butyllithium, or dialkylzinc compounds. The second component is a
salt of a Group IV to VIII transition metal, most commonly halides
of titanium or vanadium such as TiCl.sub.4, TiCl.sub.3, VCl.sub.4,
or VOCl.sub.3. The catalyst components when mixed, usually in a
hydrocarbon solvent, may form a homogeneous or heterogeneous
product. Such catalysts may be impregnated on a support, if
desired, by means known to those skilled in the art and so used in
any any of the major processes known for co-ordination catalysis of
polyolefins such as solution, slurry, and gas-phase. In addition to
the two major components described above, minor amounts of other
compounds (typically electron donors) may be added to further
modify the polymerisation behaviour or activity of the
catalyst.
[0016] It is preferred that at least the high molecular weight
block, and preferably both blocks, of the polyethylene resin are
made using a metallocene catalyst, in which case the polydispersity
of the resin is preferably between 5 and 9. It is believed that the
improved properties of the fuel tanks are due to the fact that
metallocene catalysts have a generally constant comonomer content
as molecular weight varies.
[0017] Metallocenes may typically be represented by the general
formula:
(C.sub.5R.sub.n).sub.yZ.sub.x(C.sub.5R.sub.m)ML.sub.(4-y-l)
[0018] Where (C.sub.5R.sub.n).sub.y and (C.sub.5R.sub.m) are
cyclopentadienyl ligands, [0019] R is hydrogen, alkyl, aryl,
alkenyl, etc. [0020] M is a Group IVA metal [0021] Z is a bridging
group, [0022] L is an anionic ligand, and [0023] y is 0, 1 or 2, n
and mare from 1 to 5, x is 0 or 1.
[0024] The most preferred complexes are those wherein y is 1 and L
is halide or alkyl. Typical examples of such complexes are bis
(cyclopentadienyl) zirconium dichloride and bis(cyclopentadieniyl
zirconium dimethyl. In such metallocene complexes the
cyclopentadienyl ligands may suitably be substituted by alkyl
groups such as methyl, n-butyl or vinyl. Alternatively the R groups
may be joined together to form a ring substituent, for example
indenyl or fluorenyl. The cyclopentadienyl ligands may be the same
or different. Typical examples of such complexes are
bis(n-butylcyclopentadienyl)zirconium dichloride or his
(methylcyclopentadienyl)zirconium dichloride.
[0025] Examples of such complexes may be found in EP 129368 and EP
206794 the disclosures of which are incorporated herein by
reference.
[0026] Another type of metallocene complex is constrained geometry
complexes in which the metal is in the highest oxidation state.
Such complexes are disclosed in EP 416815 and WO 91/04257 both of
which are incorporated herein by reference. The complexes have the
general formula: ##STR1## wherein:
[0027] Cp* is a single .eta.5-cyclopentadienyl or
.eta.5-substituted cyclopentadienyl group optionally covalently
bonded to M through -Z-Y-- and corresponding to the formula:
##STR2## wherein each R is independently hydrogen or a moiety
selected from halogen, alkyl, aryl, haloalkyl, alkoxy, aryloxy,
silyl groups, and combinations thereof of up to 20 non-hydrogen
atoms, or two or more R groups together form a fused ring system;
[0028] M is zirconium, titanium or hafnium bound in an .eta.5
bonding mode to the cyclopentadienyl or substituted
cyclopentadienyl group and is in a valency state of +3 or +4;
[0029] each X is independently hydride or a moiety selected from
halo, alkyl, aryl, silyl, germyl, aryloxy, alkoxy, amide, siloxy,
and combinations thereof (e.g. haloalkyl, haloaryl, halosilyl,
alkaryl, aralkyl, silylalkyl, aryloxyaryl, and alkyoxyalkyl,
amidoalkyl, amidoaryl) having up to 20 non-hydrogen atoms, and
neutral Lewis base ligands having up to 20 non-hydrogen atoms;
[0030] n is 1 or 2 depending on the valence of M; [0031] Z is a
divalent moiety comprising oxygen, boron, or a member of Group 14
of the Periodic Table of the Elements; and [0032] Y is a linking
group covalently bonded to the metal comprising nitrogen,
phosphorus, oxygen or sulfur, or optionally Z and Y together form a
fused ring system.
[0033] Most preferred complexes are those wherein Y is a nitrogen
or phosphorus containing group corresponding to the formula
(--NR.sup.1) or (--P R.sup.1) wherein R.sup.1 is C.sub.1-C.sub.10
alkyl or C.sub.6-C.sub.10 aryl and wherein Z is SiR''.sub.2,
CR''.sub.2, SiR''.sub.2 SiR''.sub.2, CR''.dbd.CR'' or GeR''.sub.2
in which R'' is hydrogen or hydrocarbyl.
[0034] Most preferred complexes are those wherein M is titanium or
zirconium.
[0035] Further examples of metallocene complexes are those wherein
the anionic ligand represented in the above formulae is replaced
with a diene moiety. In such complexes the transition metal may be
in the +2 or +4 oxidation state and a typical example of this type
of complex is ethylene bis indenyl zirconium (II) 1,4-diphenyl
butadiene. Examples of such complexes may be found in EP 775148A
and WO 95/00526 the disclosures of which are incorporated herein by
reference.
[0036] For example the complexes may have the general formula:
##STR3## wherein: [0037] R' each occurrence is independently
selected from hydrogen, hydrocarbyl, silyl, germyl, halo, cyano,
and combinations thereof, said R' having up to 20 non hydrogen
atoms, and optionally, two R' groups (where R' is not hydrogen,
halo or cyano) together form a divalent derivative thereof
connected to adjacent positions of the cyclopentadienyl ring to
form a fused ring structure; [0038] X is a neutral .eta..sup.4-
bonded diene group having up to 30 non-hydrogen atoms, which forms
a .pi.-complex with M; [0039] Y is --O--, --S--, --NR*--, --PR*--;
[0040] M is titanium or zirconium in the +2 formal oxidation state;
[0041] Z* is SiR.sub.2, CR*.sub.2, SiR*.sub.2SiR*.sub.2,
CR*.sub.2CR*.sub.2, CR*.dbd.CR*, CR.sub.2SiR*.sub.2, or GeR*.sub.2;
wherein: [0042] R* in each occurrence is independently hydrogen, or
a member selected from hydrocarbyl, silyl, halogenated alkyl,
halogenated aryl, and combinations thereof, said R* having up to 10
non-hydrogen atoms, and optionally, two R* group from Z* (when R*
is not hydrogen), or an R* group from Z* and an R* group from Y
form a ring system.
[0043] We have found that by utilising the above-described resins,
it is possible to obtain blow-moulded fuel tanks having excellent
fire resistance and creep resistance, and also satisfactory impact
properties. The the above resins can also be used in rotomolding
processes and for thermoformed fuel tanks; preferred resins having
a low viscosity at a low shear rate, such as those made using
metallocene catalysts, are particularly suitable.
EXAMPLES
Examples 1-20
Preparation of Polyethylene Bimodal Resin by Flake Blending
A: Bench Scale Preparation of the Low Molecular Weight (LMW)
Polyethylene Fraction
[0044] Under a stream of dry nitrogen gas 1.8 millimole of
tri-isobutyl aluminium (TIBAL) and 1800 ml of isobutane-were
introduced into a dry autoclave reactor having a volume of 5 litres
and provided with an agitator. The temperature was raised to
80.degree. C., and after pressure stabilisation hydrogen gas was
added. Ethylene gas was then introduced until a partial pressure of
ethylene of 10.times.10.sup.5 Pa was achieved. The amount of
hydrogen previously introduced into the autoclave reactor was
selected so as to obtain the desired final gas phase molar ratio of
hydrogen to ethylene (H.sub.2/C.sub.2 molar ratio).
[0045] The polymerisation was then started by flushing the solid
catalyst A, ethylene bis (4,5,6,7-tetrahydro-1-indenyl) zirconium
dichloride (prepared in accordance with the method of Brintzinger
as published in the Journal of Organometallic Chemistry 288 (1995)
pages 63 to 67), into the autoclave with 200 ml of isobutane. The
temperature, partial pressure of ethylene, and the H.sub.2/C.sub.2
ratio were kept constant over the polymerisation period. The
reaction was stopped by cooling and then venting the reactor. The
low molecular weight polyethylene was then collected from the
reactor.
[0046] The detailed polymerisation conditions are specified in
Table 1.
B: Bench Scale Preparation of the High Molecular Weight (HMW)
Polyethylene Fraction
[0047] The process for preparing the high molecular weight fraction
was the same as that for preparing the low molecular weight
fraction specified above in Example A, except that instead of
adding hydrogen after raising the temperature to 80.degree. C.,
varying amounts of 1-hexene comonomer were added and a different
amount of ethylene was introduced, in order to obtain the desired
ethylene partial pressure and C.sub.6.sup.=/C.sub.2 ratio. The high
molecular weight ethylene-hexene copolymer obtained was collected
from the reactor.
[0048] The detailed polymerisation conditions are specified in
Table 1.
C: Preparation of the Polyethylene Resin Blend
[0049] In order to prepare the bimodal resin, the desired quantity
of the low molecular weight polyethylene fraction obtained in
Example A above was blended with the desired quantity of the high
molecular weight ethylene-hexene copolymer obtained in Example B
together with Irganox B225 antioxidant commercially available from
CIBA Speciality Chemicals. The resulting blend was pelletised in an
extruder (APV Baker under the trade name MP19TC25). The details of
the blending recipes are specified in Table 2. TABLE-US-00001 TABLE
1 polymerisation conditions LMW block HMW block H.sub.2/C2 C2 1-
gas partial hexene phase pressure content Ex. ratio (bar) (g) 1
3290 16 24 2 1960 18 20 3 1790 6 6 4 3290 18 50 5 1960 14 27 6 1570
14 20 7 1580 4 6 8 1830 10 18 9 1020 18 20 10 1790 6 10 11 1030 16
24 12 1030 4 6 13 1830 12 18.7 14 1690 12 26.8 15 1190 6 10 16 1330
18 50 17 1020 14 27 18 1190 12 18.7 19 1330 12 27
[0050] TABLE-US-00002 TABLE 2 Proportions and properties of blocks
of polymer for flake blending LMW block HMW block MI.sub.2 HLMI
g/10 Density Mw g/10 Density Mw Ex. wt % min g/cm.sup.3 kDa wt %
min g/cm.sup.3 kDa 1 55 207 971.5 24.6 45 0.02 921.3 607 2 54 57
968.6 33.0 46 0.03 922.0 566 3 44 35 966.8 36.9 56 0.22 929.8 335 4
54 207 971.5 24.6 46 0.03 916.5 566 5 53 57 968.6 33.0 47 0.04
919.7 515 6 55 16.9 965.2 43.6 45 0.04 921.5 524 7 38 25 966.0 39.9
62 0.61 931.5 256 8 50 41 967.8 35.6 50 0.08 922.5 438 9 60 4.7
960.4 58.3 40 0.03 922.0 566 10 43 35 966.8 36.9 57 0.28 927.1 314
11 64 2.2 958.6 69.3 36 0.02 921.3 607 12 46 2.2 958.6 69.3 54 0.61
931.5 256 13 48 41 967.8 35.0 52 0.12 922.4 453 14 50 44 968.1 35.6
50 0.08 920.2 393 15 50 2.8 960.0 35.0 50 0.28 927.1 441 16 58 8.5
963.0 65.6 42 0.03 916.5 314 17 58 4.7 960.4 51.0 42 0.04 919.7 566
18 55 2.8 960.0 58.3 45 0.12 922.4 515 19 54 8.5 963.0 65.6 46 0.07
919.8 393 Note: molecular weights in the above Table are
calculated. We have found that at low molecular weights (below
100,000) the polydispersity of the resin is approximately 3,
increasing to a value of approximately 3.25 at higher molecular
weights up to 700,000. The spread of polydispersities around these
values is approximately +/-0.5.
[0051] TABLE-US-00003 TABLE 3 Properties of bimodal polymer
MI.sub.5 HLMI g/10 g/10 Density .mu.0 .mu.2 Ex. min min g/cm.sup.3
dPa.s dPa.s Mn Mw Mz MWD 1 0.24 12.3 951.5 2390400 161000 19.6
236.4 914.8 12.1 2 0.17 7.6 950.5 3013300 191800 24.6 257.5 1012
10.5 3 0.16 4.8 948.4 29.6 228.0 758.2 8.2 4 0.30 12.9 947.1
2307100 155900 18.9 228.3 910.0 9.3 5 0.17 6.0 946.9 3210600 201100
25.6 247.9 901.3 8.9 6 0.18 5.4 947.2 3129000 211700 34.0 247.2
849.5 9.1 7 0.26 6.2 945.9 33.8 202.0 645.9 7.3 8 0.16 4.8 946.5
3434800 215000 27.3 240.3 804.9 8.6 9 0.16 4.4 947.7 3155309 228600
38.5 252.6 879.6 7.4 10 0.19 5.4 945.5 30.3 216.9 671.7 7.2 11 0.23
4.9 946.8 2641700 221000 43.0 235.1 834.3 5.5 12 0.27 5.5 945.1
42.7 192.4 562.2 4.5 13 0.13 4.1 945.2 28.4 254.0 857.6 8.93 14
0.16 5.4 944.9 3192400 211300 28.3 245.6 836.2 8.68 15 5.2 944.5
46.5 199.3 568.8 4.29 16 0.24 6.0 943.6 2644000 200500 38.6 234.9
819.6 6.09 17 0.20 5.0 945.2 3011900 219800 41.2 237.5 793.9 5.76
18 0.18 4.0 944.3 3571300 241700 46.6 232.0 715.3 4.98 19 0.20 5.0
943.8 2995700 218700 39.1 228.9 727.8 5.86 Notes: .mu.0 = Viscosity
at shear rate of 1s.sup.-1 with a 0.3/1 ratio die. .mu.2 =
Viscosity at shear rate of 100 s.sup.-1 with a 0.3/1 ratio die.
Physical Properties for Fuel Tank Use
[0052] For the various physical property evaluations, compressed
plates of varying thicknesses were formed as follows. Polymer flake
was loaded into a picture-frame mould and brought in contact with
the plates of a hot press, which were rapidly heated up to
190.degree. C. at a pressure of 20 bar. The sample was held at
those conditions for approximately 5 minutes. The pressure was
increased to 80 bar in order to force the polymer to flow out
through the shape of the frame. After 5 minutes, pressure was
released and the temperature was decreased at a rate of 15.degree.
C./min down to 35.degree. C. The plates thus obtained were stored
at room temperature for at least 7 days before being submitted to
any mechanical tests.
[0053] Impact properties were assessed by notched Charpy tests
performed at -40.degree. C. on specimens taken from 4 mm thick
compressed plates according to ISO179/1EA.
[0054] Creep resistance was assessed by tensile strength
measurements performed at 80.degree. C. under 2.5 Mpa on ISOB1A
specimens machined from 2 mm thick compressed plates.
[0055] Environmental stress crack resistance (ESCR) was determined
by FNCT performed at 50.degree. C. under 7 Mpa stress on 6.times.6
mm specimens taken from compressed plates.
[0056] The results of the above tests are shown in Table 4, and a
plot of Charpy vs Creep is given in FIG. 1, showing the boundaries
of the properties defined in the second aspect of the invention.
For commercial purposes, an acceptable value of Charpy impact is
greater than 5 kJ/m.sup.2. An acceptable value of Creep is less
than 2.4%, and an acceptable ESCR as determined by FNCT is greater
than 35 hours.
[0057] As shown in Table 4, it can be seen that all the resins of
the invention satisfy these basic requirements. However, a
significant number of the above Examples have a Charpy impact of
greater than 15 kJ/m.sup.2, as defined in the second aspect of the
invention, which makes them significantly superior to commercial
resins used in fuel tank applications such as X and Y in FIG. 4.
Several resins have. Charpy values greater than 20 kJ/m.sup.2 and
Creep values less than 2.3%, as is preferred in the second aspect
of the invention. TABLE-US-00004 TABLE 4 Properties of bimodal
polymer for fuel tank application Charpy Creep FNCT Example
kJ/m.sup.2 % hours 1 6.54 2.36 >120 2 7.43 2.37 >120 3 23.8
2.13 >120 4 7.29 2.27 >120 5 16.08 2.17 >163 6 24.45 2.21
>163 7 23.3 2.36 -- 8 9.86 1.95 >163 9 29.33 2.10 >163 10
13.86 2.30 -- 11 32.66 2.03 >163 12 25.77 2.16 63 13 24.04 2.33
>160 14 9.75 2.02 >160 15 24.29 2.09 >160 16 8.0 2.25
>190 17 26.63 -- >190 18 30.25 -- >190 19 10.54 2.30
>190
* * * * *