CA2375200A1

CA2375200A1 - Multi-shelled device for storing and transporting chemicals

Info

Publication number: CA2375200A1
Application number: CA002375200A
Authority: CA
Inventors: Hans-Ulrich Hahn; Werner Buttner; Martin Benzinger; Hans Georg Flinner
Original assignee: Individual
Current assignee: HESSENTALER CONTAINER GmbH; Merck Patent GmbH
Priority date: 1999-05-28
Filing date: 2000-05-23
Publication date: 2000-12-07
Also published as: KR20020047040A; TW492937B; CN1409678A; WO2000073154A2; EP1261523A2; AU5396600A; WO2000073154A3; DE19924650A1; JP2004513844A

Abstract

The invention relates to a device for storing and transporting chemicals, especially liquid high-purity chemicals used in the electronics industry, which has at least the following components: a) a multi-shell inner containe r comprising an inner shell which is located on the side of the stored chemica ls and which is made of an HDPE that contains no stabilizers, and comprising at least one polyethylene shell which surrounds the inner shell, and; b) a plastic transport device that does not contain any metal. The invention additionally relates to a co-extrusion method for producing a device for storing and transporting chemicals, especially liquid high-purity chemicals used in the electronics industry, whereby the method has at least the following steps: a) using blowing techniques to produce a hollow body made o f an HDPE that contains no stabilizers; b) simultaneously using blowing techniques to encase the hollow body obtained in a) with at least one polyethylene shell; c) producing a plastic container such that the hollow bo dy which is obtained in a) and which is encased by at least one polyethylene shell can be adjusted therein.

Description

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.

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.

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:

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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 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-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.

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-_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 _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.

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 ::~-,e.a~'-> r.::.: ccntac: ~ctv,~c~r. t1° :ndi~edua! lav,~r~

Claims

1. Device for storing and transporting chemicals, in particular liquid, highly-pure chemicals for the electronics industry, comprising at least the fol-lowing components:

a) a multi-shelled inner container, comprising an inner shell facing the contents, made of a polyethylene and at least one shell en-compassing the inner shell, made of polyethylenes, and b) a metal-free transport facility made of plastics, wherein the inner container of the device is made by co-extrusion, and wherein the one inner shell facing the contents is made of a stabilizer-free PE-HD.

2. Device in accordance with claim 1, wherein said stabilizer-free PE-HD is a polyethylene with a specific density ranging from 0.940 to 0.970 g/cm3.

3. Device in accordance with anyone of the preceding claims wherein said stabilizer-free PE-HD is a polyethylene with a specific density ranging from 0.942 to 0.961 g/cm3.

4. Device in accordance with anyone of the preceding claims wherein the stabilizer-free polyethylene emits at least one of the following ionic impu-rities 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, Mn <= 0.3 ng/g, Cu <= 1.5 ng/g.

5. Device in accordance with anyone of the preceding claims, wherein said metal-free transport facility is a transport box made of metal-free plastics.

6. Device in accordance with anyone of the preceding claims, wherein said metal-free transport box is made in such a way that it can completely en-compass the inner container.

7. Device in accordance with anyone of the preceding claims, wherein said device has a filling capacity of at least 200 1.

8. Co-extrusion method for the production of a device for storing and trans-porting chemicals, in particular of liquid, highly-pure chemicals for the electronics industry, comprising at least one multi-shelled inner container and at least one metal-free transport facility, as defined in claim 1, wherein the method comprises at least the following steps:

a. production of a hollow 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 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 be inserted therein.

9. Method in accordance with claim 9, wherein steps a) and b) are performed under inert-gas atmosphere.

10. Method in accordance with anyone of claims 9 or 10, wherein the con-tainer is rotation-sintered in step c).