Note: Descriptions are shown in the official language in which they were submitted.
CA 02375200 2001-11-26
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Multi-shelled device for storing and transporting chemicals
The invention relates to a multi-shelled device for storing and transporting
chemi-
cals, especially liquid, highly-pure chemicals for the electronics industry.
For the production of electronic components. liquid chemicals are frequently
re
to quired; a high state of purity is required of them. In particular for the
production
of highly integrated ' ' :. ~. .... ......_....;,'-,-',:~.'~ ~':_.~._ ~F
~_,~:.., :_ y
:tili.:-lW :: ~ ~ . ~. - r°yairrd
due to the ever-decreasing dimensions of these microchips produced in using
pro-
cess chemicals. In general, the purity requirements for liquid special
chemicals,
e.g. process chemicals for the electronics industry, have increased
considerably
over the past few years. It is no longer sufficient to produce chemicals with
the
required degree of purity, but it has to be ensured that the product is not
rendered
impure during transport, storing, and handling. Furthermore, safe storing and
transport has to be ensured since some of these chemicals may be aggressive or
even toxic. The accidental leaking of such chemicals, e.g. due to damage to
the
2o transport container or due to leakage, has to be excluded by highest-
possible de-
grees of certainty. For reasons of economy, only large packing drums can be
used
for delivery of liquid, highly-pure chemicals. These packing drums ought to be
designed in such a way as to prevent contamination of the container's
contents,
and as to provide protection against breakage even from rough handling by fork
lift trucks and similar equipment. In addition, the containers ought to be
easy to
produce at a low cost. They ought to be movable by means of fork lift trucks
and
other common transport equipment without transport risk.
CA 02375200 2001-11-26
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Therefore, two aspects have to be considered when choosing the material for
such
containers. First, the choice has to be directed at excluding any
contamination by
means of the container's wall material in contact with the chemical to be
trans-
ported or stored. Besides the prevention of contamination of the chemicals to
be
transported and besides the resistance against possible leaching out of the
chemi-
cals to be transported, the container also has to possess sufficient stiffness
as well
as a certain degree of elasticity, in order to ensure that the container is
pressure-
and shock-resistant and sturdy and neither has a tendency to deform nor to
crack.
Furthermore, it is desirable for the container to have a relatively large
capacity
1o and to be quickly and easily producible.
It is known from DE 196 28 653 that certain polyethylenes, especially unstabi-
lized HD-polyethylenes are well suited for the production of storing and
transport
containers for liquid, highly-pure chemicals to be used in the electronics
industry.
In particular, HD-polyethylenes with a specific density between 0.940 and
0.970
g/cm3, and especially between 0.942 g/cm3 and 0.961 g/cm3 are mentioned. This
includes in particular polyethylenes that are distributed under the trademark
Lu-
polen. Lupolen~ 6021D, Lupolen~ 5021D, Lupolen~ 4261AQ149, and Lupo-
len~ 4261AQ135 are mentioned as examples. According to this prior art, corre-
2o sponding devices were produced by welding of plates consisting of the above
materials. The welding of the correspondingly extruded plates rendered the pro-
duction of such containers time-consuming and expensive. Moreover, the quality-
maintaining properties of Lupolen~ 6021D could not be guaranteed
satisfactorily
due to the welding and the resulting welding seams. On the other hand, it has
not
yet been possible to blow-extrude mono-blow extruded transport containers with
a
volume of e.g. 2001, or the containers produced in such a way could not meet
with
the mechanical requirements of the dangerous-goods-packaging test.
CA 02375200 2001-11-26
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The specification EP 0 484 771 relates to a transport container for liquid
chemi-
cals, in particular liquid highly-pure chemicals for the electronics industry,
con-
sisting of an inner container and an outer container, wherein the inner
container
consists of an inner layer made of highly-pure additive-free polyethylene and
an
outer layer made of common additive-containing polyethylene. The inner layer
and the outer layer of the container are not connected but have a spacing
which is
Filled with gas in a preferred embodiment of the invention.
In DE 44 18 725, a mineral-oil storing tank made of polyethylene is disclosed.
The wall of the mineral-oil storing tank has an inner layer and an outer
layer. The
inner layer consist of pristine polyethylene (PPE). The outer layer consist of
a
mixture of recycling polyethylene (RPE) and pristine polyethylene (PPE). The
mineral-oil tank is formed by means of blow extrusion and of a thermo-
;...a:~~;~r~L~? ~,i..oa,,.ArP~I h~,~c ~,r~duced by co-extrusion, with an
internal layer of
PPE and an outer layer made of YPF plus fZfE.
It is one problem of the present invention to provide another device for
storing
and transporting of chemicals, in particular of highly-pure, liquid chemicals
for
the electronics industry and a corresponding method for producing a device in
accordance with the invention, meeting with the above-mentioned requirements
and, moreover, allow for simple and fast production.
This problem is solved by a device in accordance with claim 1 and a method in
accordance with claim 9. Further embodiments and advantages are stated in the
sub-claims.
Accordingly, the invention provides a device for storing and transporting
chemi-
~als, in particular liquid. highly-pure chemicals for the electronics
industry, com-
prising at least the following componecns:
CA 02375200 2001-11-26
>page3a<
a) a multi-shelled inner container, comprising an inner shell facing the
contents, made of stabilizer-free PE-HD and at least one shell en-
compassing the inner shell, made of polyethylenes, and
b) a metal-free transport facility made of plastics.
Within the scope of the present invention, stabilizer-free HD-PE is HD-PE pro-
duced without the use of the stabilizers that are normally used. Generally
used
stabilizers are in particular antioxidants that are known to the person
skilled in the
art (cf. Kunststoffe 78(2), 142 ( 1988)).
In accordance with the invention, the method of multl-layer blow extrusion or
co-
extrusion is used for producing a device for storing and transporting highly-
pure
CI;Ct711CaIS. r~CCOrdIIl~T t0 the fIlVClILIOIi, il7C illirCllani.:aii j
~~~:ari, iii~ilty-l7lifc ~n-
nermost shell made of stabilizer-free HD-PE is used on the side contacting the
CA 02375200 2001-11-26
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Chemical, while the material used for the shell encompassing the innermost
shell
can be freely chosen from known extrudeable materials, such as e.g. common
HD-PEs with a density ranging between 0.94 to 0.97 g/cm3, e.g. Lupolen~
4261AQ135 or Lupolen~ 52612, as well as the corresponding Hostalen~ prod-
s ucts. The mufti-layer blow extrusion allows to produce the inner container
of the
device in accordance with the invention in one continuous production process.
Thus, considerable cost and time savings are possible in comparison to the
weld-
ing process used until now. Moreover, the device in accordance with the
invention
is considerably more resistant to pressure and dropping than the containers
known
to until now, since it is made in one piece and does not have any welding
seams or
other weak spots. In co-extrusion, several layers of polymer melt are superim-
posed and connected inside the extrusion nozzle. Such mufti-layered nozzles
are
equipped with several inlets for the melt and one common outlet.
15 In accordance with the present invention, the mufti-shelled inner container
of the
device is placed into a metal-free transport facility made of plastics.
Preferably,
the metal-free transport device is a sold plastic transport box made of metal-
free
plastics. In another preferred embodiment, the transport box comprises an inte-
grated pallet serving as protection against damage imposed during transport.
The
2o integrated pallet also further stabilizes and supports the inner container
of the de-
vice in accordance with the invention.
Preferably, the stabilizer-free HD-PE is a polyethylene with a specific
density
ranging from 0.940 to 0.970 g/cm3, in particular from 0.942 to 0.961 g/cm3,
par-
25 ticularly preferable from 0.946 to 0.960 g/cm3; this type of polyethylene
emits
particularly minute amounts of particles as impurities.
In accordance with yet another preferred embodiment of the present invention,
the
stabilizer-free HD-PE is a polyethylene with a specific density ranging from
0.940
30 to 0.970 g/cm3, in particular from 0.942 to 0.961 g/cm3, particularly
preferable
from 0.946 to 0.960 g/cm'; this type of polyethylene emits at least one of the
fol-
CA 02375200 2001-11-26
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lowing ionic impurities according to the following list, when in contact with
basic,
neutral, and acidic, highly-pure chemicals:
Al < 60 ng/g,
Ca < 60 ng/g,
Fe < 63 ng/g,
Mg < 16 ng/g,
Ti < 4 ng/g,
Zn < 6 ng/g,
to Mn < 0.3 nglg,
Cu < 1.5 ng/g.
The non-stabilized HD-PEs are furthermore characterized by a low content of
~aa:,vt :e:nm;..:t~. ~a.~..r:~ ~'.:e~e c4:?~stance~ ~.~ emit ~arricularly
mi!~ute amounts of
ionic impurities when in contact with basic or acidic, highly-pure chemicals.
Moreover, a comparatively low amount of particles is created by interactions
be-
tween the chemicals to be stored or transported and the materials. Preferably,
the
content of particles should be as follows:
_particles of < 0.5 Vim: content < S/ml liquid,
particles of < 0.2 pm: content < SO/ml liquid,
particles of < 0.1 pm: content < 500/m1 liquid.
The HD-PE sold under the trademark Lupolen~ 4261A! 149 is particularly pre-
ferred. This substance possesses the purity required for highly-pure
chemicals.
Moreover, this material is well-suited for extrusion.
Preferably, at least one more shell of the device, preferably the outermost
shell, is
made of an extrudeable polymer or copolymer, preferably of an HD-PE with a
3o specific density ranging between 0.940 to 0.970 g/cm3, in particular from
0.942 to
0.961 g/cm3, particularly preferably from 0.946 to 0.960 g/cm3.
CA 02375200 2001-11-26
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In accordance with a preferred embodiment, the outermost layer comprises at
least
one HD-PE from the group consisting of Lupolen~ 5261 D, Lupolen~
4261AQ135, Hostalen~ GM6255, Fina~ 56020, Borealis~ 8214, Stamylan~
7731, and 7890, Daplen~ AH5493, or a mixture of two or more of this group's
HD-PEs.
In accordance with yet another preferred embodiment, the outermost layer com-
prises pigments, protecting the layer against UV light. Thus, the device is in
par-
1a ticular prevented from any damage caused by incident light occurring during
transport. The layer retains its properties regarding mechanical stability.
Prefera-
bly, the used pigment is soot; however, quartz, common master batches, and
other
common pigments such as cu-phthalocyanine or Ti02, as well as organic UV-
atabi'.:~ers ai:d h;_nhenvl ~o,,~z~ouads can be used.
In accordance with another preferred embodiment of the invention, the
outermost
layer is reinforced in order to increase the resistance against pressure,
dropping, or
shock of the device in accordance with the invention by e.g. means of glass
fibers
or addition of further mechanically stabile materials, such as polymers.
Prefera-
2o bly, platelets made of polyamide are integrated into the outermost layer in
order to
provide for this reinforcement. For this purpose, e.g. PE-composites such as
selar
can be used.
In accordance with a particularly preferred embodiment, the device consists of
two shells. The innermost shell, preferably made of Lupolen~ 4261AQ149, adds
20% to 40% to wall thickness, whereas the outermost layer correspondingly con-
tributes 60% to 80%. This configuration has proven to be particularly stable.
in accordance with another preferred embodiment, the device comprises at least
3o three layers, wherein the at least one central layer consists of waste from
the pro-
CA 02375200 2001-11-26
_7-
duction. This type of waste is so-called "clump waste", referring to those
parts
which drop off the upper and lower ends during the "final shaping" of the
device.
Preferably, the device in accordance with the invention has at least one
opening,
preferably a plurality of openings. Therein, a diameter of < 1 SO mm is
preferred
for the openings, most preferably < 70 mm. The openings serve for receiving
plunger pipes or plug stoppers. These are preferably made of one or more of
the
following materials: PE-HD, perfluor alkoxy polymers (PFA), polypropylene,
PVdF, and perfluorized polyethylene propylene (FEP).
to
The openings can be adapted by inserting special moulds into the blow mould or
by corresponding adapters of various extraction systems, such as plunger pipes
or
coupling systems. This results in a particularly low level of contamination
during
filling and/or extracting of the nrod~.;" irtc ~:~ ';.,:. .'.',a r~~;u:;;e..
In accordance with a preferred embodiment of the present invention, the device
has a filling capacity of > 200 l, preferably of > 5001. Simple and fast
production
of a device for transporting and storing highly-pure chemicals, meeting with
safety requirements, is possible due to the production by means of multi-layer
2o blow extrusion and the additional providing of a metal-free transport
facility. This
results in considerable cost and time savings.
In accordance with a preferred embodiment of the present invention, the metal-
free transport facility is designed in such a way that it can completely
encompass
the mufti-shelled inner container. Preferably, the metal-free transport
facility is a
metal-free box made of solid plastics into which the mufti-shelled inner
container
can be placed. In accordance with a preferred embodiment, the transport box is
made of an LLD-PE. Therein, the box is made in accordance with a two-layer
method, wherein both the outer layer and the inner layer are rotation-
sintered, and
3o are foamed, using an LLPD-PE granulate, interspersed with, e.g., pentane or
hex-
ane. This transport box is preferably provided with a protective cover, which
is
CA 02375200 2001-11-26
_8_
preferably made of the same material, and by means of which the transport box
can be completely sealed so that the inner container comprised therein is
totally
protected against external influences. As already mentioned, the transport
box's
interior is provided with a pallet to further stabilize it and protect the
inner con-
tamer from transport-caused damage.
The transport box is preferably made by a rotation sintering process. This
produc-
tion method results in a box which is shock-resistant and involves low
production
costs.
Furthermore, the invention relates to a co-extrusion method for producing a de-
vice for storing and transporting chemicals, in particular liquid, highly-pure
chemicals for the electronics industry, wherein the method comprises at least
the
r='1 ,,v~ "fn...,.
.' S U . J~Lyi.:
a. production of a hallow body made of a stabilizer-free HD-PE by
means of a blow method;
b. simultaneous encompassing of the hollow body from a) with at
2o least one shell made of polyethylene (co-extrusion);
c. production of a container made of plastics in such a way that the
hollow body from a), encompassed by at least one shell made of
polyethylene, can inserted therein.
Preferably, the plastification step of the method in accordance with the
present
invention is carried out under conditions of inert-gas superimposition.
Preferably,
nitrogen is used as inert gas. This means that inert gas, preferably nitrogen,
is used
as blow gas instead of air for the production by means of a blow method.
CA 02375200 2001-11-26
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The superimposition of nitrogen during the production of the device in
accordance
with the present invention causes the oxygen to be suppressed from the
surround-
ing air or is shielded from the polyethylene necessary for production, in
order to
avoid oxidative interference of the unstabilized polyethylene during the
individual
method steps. Oxidative interference may be e.g. grid obstruction due to
oxygen
molecules stored or knot formation, already mentioned.
Simple and fast production of a mufti-shelled device in accordance with the
pres-
ent invention is possible due to the method in accordance with the invention.
Ac-
to tually, only one continuous work process is required for shaping the inner
con-
tainer. Any subsequent welding of pre-fabricated plates is omitted; therefore,
the
finished device does not have any welding seams. The direct joining of the
indi-
vidual layers even during production leads to a special degree of stability
and an
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