Note: Descriptions are shown in the official language in which they were submitted.
~ CA 02246339 1998-08-13
WO 97129859 PCT/EP97/00524
A Process for Cleaning Beverage Bottles
This invention relates to a process for cleaning bottles, more particu-
larly plastic bottles, in bottle cleanin~3 machines.
In known processes, returnable bottles for beverages are cleaned in
bottle cleaning machines using additive-containing sodium hydroxide which
has been heated to as high as 85~C. In summer in particular, the returnable
bottles contain a large number of microorganisms when they come back
empty from the consumer. Such bottles are often exposed for several days
or even weeks to temperatures favorable to the growth of the microorganisms.
Yeasts thus have the opportunity to proliferate and to ferment any residual
beverage while molds form Alawns~ in the bottle.
To remove most of the mold, the bottles are rinsed with water
(preliminary cleaning) and then cleaned in liquor baths with about 1.5%
caustic soda heated to 50-85~C. However, this cleaning operation is not
sufficient to remove all the microorganisms and mold. For this reason, it is
well-known that complexing agents, for example EDTA (ethylenediamine
tetraacetic acid) and/or NTA (nitrilotriacetate), can be added to the liquor
baths so that molds are satisfactorily removed in the case of glass bottles.
However, in the cleaning of refillable plastic bottles, for example of
PET (polyethylene terephthalate), the use of liquor baths to which complexing
agents, such as those mentioned above, have been added is not successful.
After the cleaning cycle, unacceptable residues of mold and dead yeast cells
remain behind on the surfaces of the PET bottles.
Accordingly, the problem addressed by the present invention was to
achieve thorough and satisfactory removal of microorganisms and molds and,
in particular, complete separation of the mold lawn from the plastic surfaces
in the cleaning of glass bottles and, in particular, plastic bottles consisting
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preferably of polycarbonate, polyethylene naphthalate (PEN) or- above all -
of PET in bottle cleaning machines.
According to the invention, this problem has been solved by the
process mentioned at the beginning which is characterized in that a cleaning
formulation containing available oxygen is allowed to act on the bottles. It hassurprisingly been found that, where available oxygen is added to the cleaning
formulation, an excellent cleaning result is obtained after only a few minutes.
By Aavailable oxygen@ is meant oxygen which can be eliminated in reactive
(atomic) form from an oxygen carrier. Examples of available oxygen carriers
are perborates, percarbonates and, in particular, hydrogen peroxide.
It is specifically pointed out that the invention is not directed to
disinfection by destruction of the mold and microorganisms, but ratherto the
mechanical separation and removal of these particular contaminants.
The cleaning formulation containing available oxygen can be applied
to or introduced into the bottles in various ways. Spray tubes are preferably
used for this purpose. In one embodiment, the cleaning formulation
containing available oxygen is sprayed onto and/or into the bottles, particu-
larly during the preliminary cleaning phase. An optimal combination of
cleaning-active available oxygen and spraying mechanism is achieved in this
way.
In selecting the composition of the cleaning formulation, it has proved
to be of advantage for the cleaning formulation, which normally contains 0.5
to 5% and, more particularly, 1 to 4% of caustic soda, to contain 0.001 to 2%,
preferably 0.005 to 1.5% and more preferably 0.1 to 1% of available oxygen.
The cleaning formulation may additionally contain surfactants, namely
anionic, cationic and/or nonionic surfactants, for example sugar surfactants,
which facilitate or improve the separation of the microorganisms and, in
particular, the mold lawn. In another advantageous embodiment, the cleaning
formulation contains complexing agents, for example polyacrylates,
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WO 97/29859 3 PCT/EP97/00524
tripolyphosphates, organic phosphonates; chelating carboxylates, for example
citrates, maleates, gluconates, EDTA and/or NTA, and terpenes and/or
solvents, for example alcohols or dimethyl sulfoxide. These additional
ingredients may be present in the cleaning formulation either separately or in
combination. These additional ingredients improve the cleaning performance
of available oxygen.
The invention is not confined to application of the cleaning formulation
containing available oxygen to or into the bottles through spray tubes. Other
ways of contacting the bottles with the cleaning formulation may also be used.
Thus, in another embodiment of the invention, the cleaning formulation
containing available oxygen is added to the liquor bath of the bottle cleaning
machine, more particularly by continuos introduction of cleaning formulation
into the liquor feed line of the bottle cleaning machine.
In this case, too, the concentration of available oxygen in the liquor
bath should be from 0.001 to 2% and is preferably is from 0.005 to 1.5% and
more preferably from 0.1 to 1%.
The temperature of the cleaning formulation should be in the range
from 40 to 90~C and is preferably in the range from 50 to 80OC. These
preferred temperature ranges also apply where the cleaning formulation
containing available oxygen is applied by the spray method mentioned above.
In anotherfavorable embodiment, the cleaning formulation containing
available oxygen is allowed to act on the bottles for 0.5 to 10 minutes,
preferablyfor 1 to 8 minutes and more preferablyfrom 2 to 7 minutes. These
exposure times app!y b~~th in cases whgFQ~he~l~aningfQrmw!a~ c~taining
available oxygen is applied in the liquor bath and where it is applied by
spraying.
To stabilize available oxygen, the cleaning formulation preferably
contains one or more complexing agents, for example phosphoric acid,
tripolyphosphate and/or sodium diphosphate.
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Most modern bottle washing machines use a combination of spraying
and steeping. The bottles are placed in so-called baskets and transported
through several treatment zones in which they are treated for certain times.
In the spraying section, the bottles with their openings facing downwards are
treated with a concentrated spray jet.
In the steeping section, the bottles are completely immersed in the
liquor steeping bath and transported through the liquor treatment zone.
Spraying with the cleaning formulation containing available oxygen can take
place either in only one liquor zone, for example in liquor I spraying, or in
several liquor zones, for example in liquor 1, liquor 11, liquor 111 spraying. The
liquor baths generally contain NaOH and a cleaning additive. In addition, the
described cleaning formulation containing available oxygen is added. Such
impurities as label remains, soil, glue constituents and the like are also
present.
The cleaning additives are frequently acidic solutions which, after
addition to the alkaline cleaning liquor, form the corresponding salts which in
turn develop a cleaning-active effect.
