Note: Descriptions are shown in the official language in which they were submitted.
. ~
2 2 ~ 19 ~ g3l04~37
~ WO96116159
ÇT.P!~NTNG ~ .tlli)V
The present invention relates to a method of
cleA~; ng glass containers.
Many glass containers such as bottles which are
used for selling beverages, for example beer, milk or
5 soft drinks, are recycled. Before refilling, they are
washed in an industrial bottle washer. These industrial
washers conventionally consist of a multiplicity of
pockets arranged along a conveyor which conveys the
items to be washed through a tortuous path where they
lO are treated with a cleaning solution and then rinsed.
They are loaded into the pockets by an automatic
m~c~An; ~m such as a turntable. Typically, these
machines can handle from 5,000 to lO0,000 bottles per
hour, or more, depending on machine capacity.
The conventional cl~An;ng solution usually
contains about 1% by weight of sodium hydroxide and an
anti-foam agent and is applied at a temperature of around
80C. It is often applied by a soaking stage followed by
a spray stage, prior to rinsing, or else by just spraying
20 before rinsing.
Many people will~be familiar with the
phenomenon of scuffing, which produces whitish circles
or part-circles around the exterior of the bottle. It is
,
WO96/16159 2 2~ 1 g 2 1 PCT/~l55~i'37
believed that scuffing is produced partly by chemical
errosion of the glass surface by the cleaning solution
and partly by mechanical abrasion, e.g. between the
bottles themselves or between the bottles and parts of
5 the cleaning apparatus.
The aforementioned problem has now been
solved in accordance with a first aspect of the present
invention, by a method of cleaning glass containers in
a continuous-feed process, the method comprising the step
lO of applying to the containers, an aqueous composition
comprising an alkaline agent and a weak sequestrant.
Cleaning with such a composition has been
found to reduce scuffing significantly.
It should be noted that glass items (e.g.
15 drinking glasses) are often mechanically cleaned using
domestic or industrial warewashing compositions which
contain inter alia alkaline agents and sequestrants.
However, this is not in a continuous-feed process where
the aforementioned scuffing problem occurs.
Preferably, the aqueous composition contains
from 0.1% to 10% by weight of the alkaline agent, more
preferably from O.S% to 5% by weight and especially from
0.75% to 2% by weight.
Preferably also, the aqueous composition
25 contains from 50 to lO00 ppm by weight of the weak
sequestrant, more preferably from lO0 to 500 ppm by
weight and especially from 200 to 400 ppm by weight.
22~ ~9~ ~
WO96/16159 ~ 55/04537
The weak sequestrant may for example comprise
one or more agents selected from polyacrylate-type
sequestrants and phosphonate sequestrants. Preferred
polyacrylate-type sequestrants include polyacrylic acids
5 or polyacrylates, especially low molecular weight
polyacrylates, e.g. MW<10,000, e.g. Sokalan PA15 ex BASF
or Norasol LMW45 ex Norso-Haas, and maleic
anhydride/(meth)acrylic acid copolymers, e.g. Sokalan
CP5 ex BASF. Suitable phosphonate sequestrants include
10 the range sold under the "Dequest" Trade Mark, ex
Monsanto.
Suitable alkaline agents include alkali metal
hydroxides, e.g. sodium or potassium hydroxides, alkali
metal silicates, including metasilicates, e.g. sodium
15 silicate having a mole ratio of SiO2:Na2O of about
3.3:1 or less, including from about 1.8:1 to about 2.2:1
(normally referred to as sodium disilicate). Sodium
hydroxide is especially preferred. However, the
alkaline agent could comprise two or more different such
20 materials.
According to a second aspect of the invention,
there is provided an aqueous composition for continuous-
feed cleaning of glass containers, the composition
comprising from 0.5% to 10% by weight of an alkaline
25 agent and from 50 to 1000 ppm by weight of a weak
sequestrant. Particularly preferred amounts and type of
alkaline agent and weak sequestrant for such a
composition are as indicated above.
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W096/16159 PCT~5/04537
The composition used in the method of the
present invention may also contain some non-ionic
anti-foam and/or wetting agent, for example in a weight
ratio of from l:50 to l:lO relative to the weak
.5 sequestrant. It is also possible for the composition to
contain one or more other minor ingredients which are
usual in such compositions. However, often the
composition will be substantially free of other
ingredients.
Usually, the step applying the aqueous
composition to the glass containers, will be followed by
a rinsing step, preferably using water, optionally
including a rinse aid. This could be a two-stage process
using first warm, and then cold water.
The aqueous composition itself is conveniently
prepared by diluting a pre-concentrated aqueous solution
of the weak sequestrant with an aqueous solution of the
alkaline agent. The latter will normally contain all of
the alkaline agent to be present in the final solution
20 and all of the water, except for the amount contained in
the pre-concentrated aqueous solution of the sequestrant.
The method of the present invention can be
applied to the continuous-feed cleaning of any glass
containers, for example beverage containers but one
25 useful example is in the cleaning of beer bottles.
The present invention will now be explained in
further detail by way of the following non-limiting
~ W096,l6l5g ~ ~ O ~ 9 2 t ~ 5/04537
experiments:
Experiment 1
An aqueous soiution of 15% by weight weak
5 sequestrant, (being either variant (a) polyacrylate
sequestrant, i.e. Sokalan PA15 ex BASF, av MW lS00 or
variant (b) phosphonate sequestrant, i.e. Dequest 2000 ex
Monsato) was diluted in a bath with a 2% by weight
aqueous solution of sodium hydroxide contA; n; ng non-ionic
10 anti-foam agent, such that the amount of weak sequestrant
in final solution was 300 ppm by weight. The amount of
anti-foam in final solution was in the weight ratio of
2:15 relative to the sequestrant.
The final solution, in each case was applied to
15 beer bottles in an industrial bottle washing machine at a
maximum temperature of 80C, flrst in a soaking step and
then in a spray step. This cleaning process was followed
by rinsing using softened water at 40C as a first rinse
step and then cold fresh softened water as a second rinse
20 step.
Ex~eriment 2
0.3 litre Dutch standard beer bottles were
subjected to alternate mPc~n;cal and chemical
25 conditions, for both a control bottle batch and a bottle
batch subjected to chemical conditions according to the
present invention, whereafter the level of scuffing was
assessed both visually and by a charge coupled device
(CCD) camera.
The CCD camera recorded the number of non
reflective pixels on the bottle. On the basis of this
figure the bottle was classified into a scuffing
category.
The bottles were subjected to mechanical
35 conditions by placement on a 10 meter conveyor loop for
10 minutes.
~2~ 1~2 1
W096/161S9 P~ 5S,'~1~37 ~
Chem`ical control conditions consisted Of
soaking 50 control bottles in a 1% solution Of NaOH in
soft water (<1 german hardness) at 80C.
According to the present invention, the
5 chemical conditions consisted of soaking 50 bottles in
1~ solution of NaOH plus 0.2~ of the formulation A.
Formulation A:
Nitrilotrimethylene phosphonic acid 15.0
10 Sodium cumene sulphonate 3.6
Non ionic surfactant 2.0%
Distilled water rest
Every 5 cycles, 5 bottles were removed from the
15 test and visually classified in comparison to reference
bottles, wherein a cycle consisted of exposure to the
mechanical conditions for 10 minutes, followed by
exposure to the chemical conditions for 10 minutes, and
the reference bottles were beer bottles considered
20 visually acceptable by Heineken.
Visual level 5 is considered to be the m~;mllm
acceptable level for bottles.
To m; ~; m; ze thermal stress, the bottles were
exposed to a soak bath between the mechanical and
25 chemical treatments, wherein the temperature change was
limited to 35C between the respective treatments.
WO96/16159 2 2 0 1 9 2 1 PCT~P9S/04537
Table 1. Results experiment 2
Test Number of Visual level Visual level
. cycles of scuffing of scuffing
(control) (invention)
5 1 5 2
2 10 2 2
3 15 2 2
4 20 3 2
4 3
6 30 4 4
7 35 5 4
8 40 5 5
9 45 6 5
The scuffing category found by the instrumental
method correlated very well with that of the visual
assessment
20 Experiment 3
As a control, standard 0.3 litre beer bottles
were subsequently subjected to production bottlewashing
conditions.
Each test was started with 50 bottles per
25 condition to be examined.
The bottles were put into crates which were put
A at the beginning of the washing line. The bottles
followed the standard route of: decrater, bottlewasher,
filler, tunnel pasteurizer, labeling machine, crate
30 packer.
WO~6/16159 2 2 0 ~ Q 2 t P~ 55/04537
The bottles were collected from the filled
crates, emptied and reintroduced at the beginning of the
line.
The chemical treatment consisted of washing the
5 bottles in a regular bottlewasher at the conditions and
temperatures prescribed.
Every 5 cycles, 5 bottles were removed from the
test and visually classified in comp~rison to the
reference bottles as in experiment 2.
The bottles were also assessed by using the CCD
camera to determine scuffing levels as described before.
The bottlewashing conditions in the control
were:
1 + 0.1% NaOH solution, temperature 80 + 1C.
Table 2. Results control
Test Number of Number of Visual
cycles pixels scuffing level
1 5 170 2
2 10 327 2
3 15 808 2
4 20 2512 3
, 4207 4
6 30 5979 4
7 35 7789 5
8 40 9727 5
9 45 14259 6
~ wog6/l6l5g --- 2 2 0 1 9 2 1 PCT~P95/04537
g
50, 0.3 litre Dutch stAn~Ard beer bottles were
subsequently subjected to the same test production
bottlewashing conditions as above, but using the bottles
w~h;ng formulation A under the following conditions:
S 1 + 0.1% NaOH solution, 0.2 + 0.05% of
formulation A, and a temperature of 80 + 1C.
The results of this are shown in table 3.
10 Table 3.
Test Number of Number of Visual
cycles pixels scuffing level
1 5 49
2 10 195 2
3 15 492 2
4 20 1640 3
4667 4
6 30 5880 4
7 ' 35 8728 5
8 40 10229 5
9 45 10587 5
14326 6
