Title of Invention	METHOD OF CONDITIONING THE SURFACE OF A LITHO-SHEET OR LITHO-STRIP CONSISTING OF AND ALUMINIUM ALLOY
Abstract	The invention relates to a method of conditioning the surface of a work piece, in particular of a litho- strip or litho-sheet, consisting of an aluminium alloy. The object of the invention to provide a method for conditioning the surface of a work piece and a work piece consisting of an aluminium alloy enabling an increasing manufacturing speed in surface roughening while maintaining a high quality of the electro-chemical grained surface of the work piece with relative low effort related to facility equipment, is solved in that the method of conditioning comprises at least the step of degreasing the surface of the work piece with a degreasing medium, wherein the aqueous degreasing medium contains at least 1,5 to 3 % by weight of a composite of 5 - 40 % sodium tripolyphosphate, 3 - 10 % sodium gluconate, 3 - 8 % of a composite of non-ionic and anionic surfactants and optionally 0,5 to 70 % soda, preferably 30 - 70 % soda, wherein sodium hydroxide is added to the aqueous degreasing medium such that the concentration of sodium hydroxide in the aqueous degreasing medium is 0, 01 to 5 % by weight, preferably 0, 1 to 1,5 % by weight, more preferably 1 to 2,5 % per weight .

Title of Invention

METHOD OF CONDITIONING THE SURFACE OF A LITHO-SHEET OR LITHO-STRIP CONSISTING OF AND ALUMINIUM ALLOY

Abstract

The invention relates to a method of conditioning the surface of a work piece, in particular of a litho- strip or litho-sheet, consisting of an aluminium alloy. The object of the invention to provide a method for conditioning the surface of a work piece and a work piece consisting of an aluminium alloy enabling an increasing manufacturing speed in surface roughening while maintaining a high quality of the electro-chemical grained surface of the work piece with relative low effort related to facility equipment, is solved in that the method of conditioning comprises at least the step of degreasing the surface of the work piece with a degreasing medium, wherein the aqueous degreasing medium contains at least 1,5 to 3 % by weight of a composite of 5 - 40 % sodium tripolyphosphate, 3 - 10 % sodium gluconate, 3 - 8 % of a composite of non-ionic and anionic surfactants and optionally 0,5 to 70 % soda, preferably 30 - 70 % soda, wherein sodium hydroxide is added to the aqueous degreasing medium such that the concentration of sodium hydroxide in the aqueous degreasing medium is 0, 01 to 5 % by weight, preferably 0, 1 to 1,5 % by weight, more preferably 1 to 2,5 % per weight .

Full Text	Method for cleaning an aluminium workpiece The invention relates to a method of conditioning the surface of a work piece, in particular of a litho-strip or litho-sheet, consisting of an aluminium alloy. Work pieces such as strips or sheets consisting of an aluminium alloy are often surface treated after finishing rolling to prepare them for the next manufacturing step. In particular strips or sheet for lithographic printing are conditioned to achieve a predetermined surface roughness in a subsequent graining process. Litho-strips or sheets are usually degreased after finishing rolling. As known from the US-patent specification US 5,997,721, degreasing respectively cleaning of the surface is done in one step by anodising the aluminium alloy sheet with AC current in an acidic electrolyte bath. Another way to degrease or clean aluminium slivers is known from the German patent DE 43 17 815 C1 namely the use of an alkaline medium. But from the use of alkaline, media it is known that they do not remove every features of the subsurface microcrystalline layer, in particular oxide particles, which are present on or near the surface of the rolled aluminium strips. However, prior electro-chemical graining the litho-strips are usually subjected to sodium hydroxide in a pre- treatment to degrease and clean the surface again, which process together with the electro-chemical graining is herein further called surface roughening process of litho- strips. In principle surface roughening is done by the manufacture of lithographic printing plates. Due to the increasing manufacturing speed of surface roughening of the litho-strips time for the pre-treatment of the surface of the litho-strips and for the electro-chemical graining decreases. It has been found that due to the increasing manufacturing speed the pre-treatment with sodium hydroxide is not sufficient enough to remove all contaminants from the surface of the litho-strip. As a consequence, the results in electro-chemical graining are not stable and surface defects occur on electro-chemically grained litho-strips or sheets. However, a reduction of the manufacturing speed causes higher production costs for lithographic printing plates. Furthermore, methods of conditioning the surface of a litho-strip including two steps require relative high expenses related to facility equipments. Hence, it is an object of the invention to provide a method for conditioning the surface of a work piece and a work piece consisting of an aluminium alloy enabling an increasing manufacturing speed in surface roughening and maintaining at the same time a high quality of the grained surface of the work piece with relative low effort related to facility equipment According to a first teaching of the present invention the above mentioned object is solved by a method of conditioning the surface of an aluminium work piece consisting of an aluminium alloy, which method comprises at least the step of degreasing the surface of the work piece with a degreasing medium, wherein the aqueous degreasing medium contains at least 1,5 to 3 % by weight of a composite of 5 - 40 % sodium tripolyphosphate, 3 - 10 % sodium gluconate, 3 - 8 % of a composite of non- ionic and anionic surfactants and optionally 0,5 % to 70 % soda, preferably 30 - 70 % soda, wherein sodium hydroxide is added to the aqueous degreasing medium such that the concentration of sodium hydroxide in the aqueous degreasing medium is 0,01 to 5 % by weight, preferably 0,1 to 1,5 % by weight, more preferably 1 to 2,5 % by weight. It has been surprisingly found that the combination of the use of the degreasing medium together with added sodium hydroxide ensures an increased manufacturing speed during surface roughening including electro-chemical graining with sufficient results despite of the fact that oxide particles are not removed completely during degreasing. The reason for the good results is seen in the fact that due to the addition of sodium hydroxide the degreasing medium has an increased pickling rate which removes more aluminium from the surface at the same time. In combination with the described pre-treatment of for example litho-strips it has been surprisingly found that the electro-chemical graining process of litho-strips can be done with a lower charge entry therefore enabling a higher manufacturing speed. While the addition of 0,1 % to 1,5 % by weight sodium hydroxide is suitable even for lower manufacturing speeds during degreasing, with the addition of 1 % to 2,5 % by weight sodium hydroxide highest manufacturing speeds during degreasing are achievable ensuring at the same time high manufacturing speeds during plate manufacturing, i.e. during electro- chemical graining. The optional addition of soda in an amount of 0,5 - 70 %, preferably 30 to 70 % by weight allows to control pH-value of the degreasing medium. According to a preferred embodiment of the invention the time of application of the degreasing medium to the surface of the aluminium work piece is at maximum 1 to 7 s, preferably at maximum 2 to 5 s. These application times ensure high production speeds at the same time ensuring that the oxide islands can easily be removed by surface roughening. To increase pickling effect of the degreasing medium the temperature of the degreasing medium is 50 to 85 °C, preferably 65 °C to 75 °C. More preferably, the pH-value of the aqueous degreasing medium is from 10 to 14, preferably 10 to 13,5. According to a next advantageous embodiment, the work piece is a strip or a sheet, in particular a litho-strip or a litho-sheet. In this case the necessary electro- chemical graining process for manufacturing litho-strips or litho-sheets can be accomplished thoroughly within less time and the printing plate manufacturing speed can be increased. Furthermore, the charge entry needed can be reduced while providing a fully grained strip or sheet surface. More preferably, the inventive conditioning method is accomplished subsequent the manufacturing of a strip, in particular a litho-strip, and the conditioned strip is reeled on a coil. In this case a coil of a conditioned litho-strip can be provided comprising an optimum performance in further surface roughening processes used to manufacture lithographic printing plates. According to a second teaching of the present invention the above mentioned object is solved by a work piece consisting of an aluminium alloy conditioned by the inventive method. As outlined before, the inventive work piece provides a cleaned surface with an optimum performance for a subsequent electro-chemical graining process. More preferably, the work piece is a strip or a sheet, in particular a litho-strip or a litho-sheet. Litho-strip or sheets are produced for lithographic printing plates and differ from "normal" sheets due to the aluminium alloy they consist of and their specific thickness, which is typically less than 1 mm, preferably 0,14 to 0,5 mm, more preferably 0,25 to 0,3 mm. Furthermore, the surface of litho-strips and sheets has to be prepared for a roughening process, since manufacturing of lithographic printing plates generally comprises an electro-chemical graining process to prepare the surface of the lithographic printing plates for the printing process. With the inventive sheets or strips, in particular with the inventive litho-sheets or litho-strips, the necessary electro-chemical graining of the surface can be accomplished in shorter time with a reduced charge entry. Beside an optimised surface of the inventive work piece the mechanical features and an improved graining structure during electro-chemical graining can be provided if the aluminium alloy of the work piece is one of the aluminium alloys AA1050, AA1100, AA3103 or AlMgO,5. These aluminium alloys provide the mechanical strength needed for lithographic printing plates while enabling due to the low amount of alloying constituents a homogeneous graining of the surface. However, work pieces consisting of other aluminium alloys may provide the same advantages. According to a more preferably embodiment of the inventive work piece the aluminium alloy contains the following alloying constituents in percent by weight: impurities each less than 0,005 % in sum max. 0,15 %, rest Al or impurities each less than 0,005 % in sum max. 0,15 %, rest Al or impurities each less than 0,005% in sum max. 0,15 %, rest Al. Work pieces consisting of one of the three aluminium alloys and conditioned with the inventive method have state of the art mechanical and graining properties, in particular if the work pieces are litho-strips which are grained electro-chemically after conditioning. It was surprisingly observed that in particular the latter aluminium alloys conditioned with the inventive conditioning method show a higher sensitivity in subsequent surface roughening processes. As a result despite of the inventive single step conditioning method, which reduces the expenses for the conditioning equipment significantly, an increase in plate manufacturing speed for litho-strips and sheets is achievable. There are a lot of possibilities to develop further the invention. Hereunto it is refer to the dependent claims of claim 1 and claim 6 as well as to embodiments of the invention in combination with the drawings. The drawings show in Fig. 1 a microscopic view of the surface of a litho-strip degreased conventionally and Fig. 2 a microscopic view of the surface of a litho-strip degreased with the inventive method. To verify the inventive method four strips made of two different aluminium alloys were tested on the one hand with different degreasing parameters and on the other with different strip velocities during electro-chemical graining on different plate manufacturing lines. The different aluminium alloys have the following compositions of alloying constituents in weight percent: alloy A: impurities each less than 0,005 % in sum max. 0,15 %, rest Al. alloy B: impurities each less than 0,005 % in sum max. 0,15 %, rest Al Litho-strips made from the aluminium alloys mentioned above where tested with regard to their graining behaviour on industrial plate manufacturing lines. For the inventive examples the degreasing medium used contains at least 1,5 to 3 % by weight of a composite of 5 to 40 % sodium tripolyphosphate, 3 to 10 % sodium gluconate, 30 to 70 % soda and 3 to 8 % of a composite of non-ionic and anionic surfactants, with an addition of sodium hydroxide in the amount of 1 % by weight. The comparative examples were degreased with the same conditions without the addition of sodium hydroxide to the degreasing medium. The results of the examples are shown in table 1 with TDegr as the temperature during degreasing, tDegr the contact time of the degreasing medium with the strip surface and vGraining the velocity of the strips in the plate manufacturing lines, i.e. the velocity during electro- chemical graining. Strip 1 and 2 produced from one mother strip were tested on the same plate manufacturing line. The same applies to strip 3 and 4. The different values of VGraining for strip 1,2 and strip 3,4 are caused by different characteristics of the plate manufacturing lines. As can be derived from table 1 the litho-strips degreased with the inventive method generally show a good appearance after electro-chemical graining even if the graining velocity was increased. However, litho-strips degreased with the inventive method show even better graining results, because the surface of the litho-strip grained with the inventive method have a finer, more homogeneous and more shallow graining structure. This graining structure provides improved printing characteristics of the inventive litho-strips. Additionally, the inventive method provides said improved graining structure even at higher manufacturing speeds, as can be derived from the results of strip 1 and strip 2. Strip 1 degreased conventionally shows merely good appearance results after electro-chemical graining at a graining velocity of 50 m/min. However, strip 2 degreased with the inventive method allows 55 m/min graining velocity. The different graining structures of the conventional and inventive degreasing method are shown in Fig. 1 and Fig. 2. Fig. 2 shows, as already mentioned, a microscopic view of the surface of a litho-strip consisting of the aluminium alloy A degreased with the inventive method after electro-chemical graining. Fig. 1 shows the graining result of the same litho-strip degreased conventionally. The graining pattern achieved with the inventive method is finer and more shallow compared to the graining pattern achieved with a conventionally degreased litho-strip. As a result, the printing characteristics of the inventive litho-strips are improved significantly. The present embodiments of the invention has been achieved by the addition of 1 % per weight sodium hydroxide. It is expected that a higher concentration of sodium hydroxide combined with an decreased contact time of the strip with the degreasing medium will lead to similar results. C L A I M S 1. Method of conditioning the surface of an aluminium work piece consisting of an aluminium alloy, in particular of a litho-sheet or litho-strip, which method comprises at least the step of degreasing the surface of the work piece with a degreasing medium, wherein the aqueous degreasing medium contains at least 1,5 to 3 % by weight of a composite of 5 - 40 % sodium tripolypnosphate, 3 - 10 % sodium gluconate, 3 - 8 % of a composite of non-ionic and anionic surfactants and optionally 0,5 - 70 % soda, preferably 30 - 70 % soda, wherein sodium hydroxide is added to the aqueous degreasing medium such that the concentration of sodium hydroxide in the aqueous degreasing medium is 0,01 to 5 % by weight, preferably 0,1 to 1,5 %, more preferably 1 to 2,5 % by weight, 2. Method according to claim 1, wherein the time of application the degreasing medium is at maximum 1 to 7 s, preferably at maximum 2 to 5 s. 3. Method according to claim 1 or 2, wherein the temperature of the degreasing medium is 50 to 85 °C, preferably 65 °C to 75 °C. 4. Method according to claim 1 to 3, wherein the pH-value of the aqueous degreasing medium is from 10 to 14, preferably 10 to 13,5. 5. Method according to claim 1 to 4, wherein a litho- strip is conditioned and the conditioning is accomplished subsequently to manufacturing, respectively rolling of the strip whereby the conditioned strip is reeled on a coil. 6. Method according to claim 1 to 5, wherein the aluminium alloy is one of the aluminium alloys AA1050, AA1100, AA3103 or AlMgO,5. 7. Method according to claim 1 to 5, wherein the aluminium alloy contains the following alloying constituents in percent by weight: impurities each less than 0,005 % in sum max. 0,15 %, rest Al or impurities each less than 0,005 % in sum max. 0,15 %, rest Al or impurities each less than 0,005 % in sum max. 0,15 %, rest Al. The invention relates to a method of conditioning the surface of a work piece, in particular of a litho- strip or litho-sheet, consisting of an aluminium alloy. The object of the invention to provide a method for conditioning the surface of a work piece and a work piece consisting of an aluminium alloy enabling an increasing manufacturing speed in surface roughening while maintaining a high quality of the electro-chemical grained surface of the work piece with relative low effort related to facility equipment, is solved in that the method of conditioning comprises at least the step of degreasing the surface of the work piece with a degreasing medium, wherein the aqueous degreasing medium contains at least 1,5 to 3 % by weight of a composite of 5 - 40 % sodium tripolyphosphate, 3 - 10 % sodium gluconate, 3 - 8 % of a composite of non-ionic and anionic surfactants and optionally 0,5 to 70 % soda, preferably 30 - 70 % soda, wherein sodium hydroxide is added to the aqueous degreasing medium such that the concentration of sodium hydroxide in the aqueous degreasing medium is 0, 01 to 5 % by weight, preferably 0, 1 to 1,5 % by weight, more preferably 1 to 2,5 % per weight .

Full Text

Method for cleaning an aluminium workpiece
The invention relates to a method of conditioning the
surface of a work piece, in particular of a litho-strip or
litho-sheet, consisting of an aluminium alloy.
Work pieces such as strips or sheets consisting of an
aluminium alloy are often surface treated after finishing
rolling to prepare them for the next manufacturing step.
In particular strips or sheet for lithographic printing
are conditioned to achieve a predetermined surface
roughness in a subsequent graining process. Litho-strips
or sheets are usually degreased after finishing rolling.
As known from the US-patent specification US 5,997,721,
degreasing respectively cleaning of the surface is done in
one step by anodising the aluminium alloy sheet with AC
current in an acidic electrolyte bath. Another way to
degrease or clean aluminium slivers is known from the
German patent DE 43 17 815 C1 namely the use of an
alkaline medium. But from the use of alkaline, media it is
known that they do not remove every features of the
subsurface microcrystalline layer, in particular oxide
particles, which are present on or near the surface of the
rolled aluminium strips.
However, prior electro-chemical graining the litho-strips
are usually subjected to sodium hydroxide in a pre-
treatment to degrease and clean the surface again, which
process together with the electro-chemical graining is
herein further called surface roughening process of litho-

strips. In principle surface roughening is done by the
manufacture of lithographic printing plates. Due to the
increasing manufacturing speed of surface roughening of
the litho-strips time for the pre-treatment of the surface
of the litho-strips and for the electro-chemical graining
decreases. It has been found that due to the increasing
manufacturing speed the pre-treatment with sodium
hydroxide is not sufficient enough to remove all
contaminants from the surface of the litho-strip. As a
consequence, the results in electro-chemical graining are
not stable and surface defects occur on electro-chemically
grained litho-strips or sheets. However, a reduction of
the manufacturing speed causes higher production costs for
lithographic printing plates.
Furthermore, methods of conditioning the surface of a
litho-strip including two steps require relative high
expenses related to facility equipments.
Hence, it is an object of the invention to provide a
method for conditioning the surface of a work piece and a
work piece consisting of an aluminium alloy enabling an
increasing manufacturing speed in surface roughening and
maintaining at the same time a high quality of the grained
surface of the work piece with relative low effort related
to facility equipment
According to a first teaching of the present invention the
above mentioned object is solved by a method of
conditioning the surface of an aluminium work piece
consisting of an aluminium alloy, which method comprises
at least the step of degreasing the surface of the work
piece with a degreasing medium, wherein the aqueous
degreasing medium contains at least 1,5 to 3 % by weight

of a composite of 5 - 40 % sodium tripolyphosphate,
3 - 10 % sodium gluconate, 3 - 8 % of a composite of non-
ionic and anionic surfactants and optionally 0,5 % to 70 %
soda, preferably 30 - 70 % soda, wherein sodium hydroxide
is added to the aqueous degreasing medium such that the
concentration of sodium hydroxide in the aqueous
degreasing medium is 0,01 to 5 % by weight, preferably
0,1 to 1,5 % by weight, more preferably 1 to 2,5 % by
weight.
It has been surprisingly found that the combination of the
use of the degreasing medium together with added sodium
hydroxide ensures an increased manufacturing speed during
surface roughening including electro-chemical graining
with sufficient results despite of the fact that oxide
particles are not removed completely during degreasing.
The reason for the good results is seen in the fact that
due to the addition of sodium hydroxide the degreasing
medium has an increased pickling rate which removes more
aluminium from the surface at the same time. In
combination with the described pre-treatment of for
example litho-strips it has been surprisingly found that
the electro-chemical graining process of litho-strips can
be done with a lower charge entry therefore enabling a
higher manufacturing speed. While the addition of 0,1 % to
1,5 % by weight sodium hydroxide is suitable even for
lower manufacturing speeds during degreasing, with the
addition of 1 % to 2,5 % by weight sodium hydroxide
highest manufacturing speeds during degreasing are
achievable ensuring at the same time high manufacturing
speeds during plate manufacturing, i.e. during electro-
chemical graining. The optional addition of soda in an
amount of 0,5 - 70 %, preferably 30 to 70 % by weight
allows to control pH-value of the degreasing medium.

According to a preferred embodiment of the invention the
time of application of the degreasing medium to the
surface of the aluminium work piece is at maximum 1 to 7
s, preferably at maximum 2 to 5 s. These application times
ensure high production speeds at the same time ensuring
that the oxide islands can easily be removed by surface
roughening.
To increase pickling effect of the degreasing medium the
temperature of the degreasing medium is 50 to 85 °C,
preferably 65 °C to 75 °C.
More preferably, the pH-value of the aqueous degreasing
medium is from 10 to 14, preferably 10 to 13,5.
According to a next advantageous embodiment, the work
piece is a strip or a sheet, in particular a litho-strip
or a litho-sheet. In this case the necessary electro-
chemical graining process for manufacturing litho-strips
or litho-sheets can be accomplished thoroughly within less
time and the printing plate manufacturing speed can be
increased. Furthermore, the charge entry needed can be
reduced while providing a fully grained strip or sheet
surface.
More preferably, the inventive conditioning method is
accomplished subsequent the manufacturing of a strip, in
particular a litho-strip, and the conditioned strip is
reeled on a coil. In this case a coil of a conditioned
litho-strip can be provided comprising an optimum
performance in further surface roughening processes used
to manufacture lithographic printing plates.

According to a second teaching of the present invention
the above mentioned object is solved by a work piece
consisting of an aluminium alloy conditioned by the
inventive method. As outlined before, the inventive work
piece provides a cleaned surface with an optimum
performance for a subsequent electro-chemical graining
process.
More preferably, the work piece is a strip or a sheet, in
particular a litho-strip or a litho-sheet. Litho-strip or
sheets are produced for lithographic printing plates and
differ from "normal" sheets due to the aluminium alloy
they consist of and their specific thickness, which is
typically less than 1 mm, preferably 0,14 to 0,5 mm, more
preferably 0,25 to 0,3 mm. Furthermore, the surface of
litho-strips and sheets has to be prepared for a
roughening process, since manufacturing of lithographic
printing plates generally comprises an electro-chemical
graining process to prepare the surface of the
lithographic printing plates for the printing process.
With the inventive sheets or strips, in particular with
the inventive litho-sheets or litho-strips, the necessary
electro-chemical graining of the surface can be
accomplished in shorter time with a reduced charge entry.
Beside an optimised surface of the inventive work piece
the mechanical features and an improved graining structure
during electro-chemical graining can be provided if the
aluminium alloy of the work piece is one of the aluminium
alloys AA1050, AA1100, AA3103 or AlMgO,5. These aluminium
alloys provide the mechanical strength needed for
lithographic printing plates while enabling due to the low
amount of alloying constituents a homogeneous graining of

the surface. However, work pieces consisting of other
aluminium alloys may provide the same advantages.
According to a more preferably embodiment of the inventive
work piece the aluminium alloy contains the following
alloying constituents in percent by weight:

impurities each less than 0,005 % in sum max.
0,15 %, rest Al
or

impurities each less than 0,005 % in sum max.
0,15 %, rest Al
or

impurities each less than 0,005% in sum max.
0,15 %, rest Al.
Work pieces consisting of one of the three aluminium
alloys and conditioned with the inventive method have
state of the art mechanical and graining properties, in
particular if the work pieces are litho-strips which are
grained electro-chemically after conditioning. It was
surprisingly observed that in particular the latter
aluminium alloys conditioned with the inventive
conditioning method show a higher sensitivity in
subsequent surface roughening processes. As a result
despite of the inventive single step conditioning method,
which reduces the expenses for the conditioning equipment
significantly, an increase in plate manufacturing speed
for litho-strips and sheets is achievable.
There are a lot of possibilities to develop further the
invention. Hereunto it is refer to the dependent claims of
claim 1 and claim 6 as well as to embodiments of the
invention in combination with the drawings. The drawings
show in
Fig. 1 a microscopic view of the surface of a
litho-strip degreased conventionally and

Fig. 2 a microscopic view of the surface of a
litho-strip degreased with the inventive
method.
To verify the inventive method four strips made of two
different aluminium alloys were tested on the one hand
with different degreasing parameters and on the other with
different strip velocities during electro-chemical
graining on different plate manufacturing lines. The
different aluminium alloys have the following compositions
of alloying constituents in weight percent:
alloy A:

impurities each less than 0,005 % in sum max.
0,15 %, rest Al.
alloy B:

impurities each less than 0,005 % in sum max.
0,15 %, rest Al
Litho-strips made from the aluminium alloys mentioned
above where tested with regard to their graining behaviour
on industrial plate manufacturing lines.
For the inventive examples the degreasing medium used
contains at least 1,5 to 3 % by weight of a composite of
5 to 40 % sodium tripolyphosphate, 3 to 10 % sodium
gluconate, 30 to 70 % soda and 3 to 8 % of a composite of
non-ionic and anionic surfactants, with an addition of
sodium hydroxide in the amount of 1 % by weight. The
comparative examples were degreased with the same
conditions without the addition of sodium hydroxide to the
degreasing medium. The results of the examples are shown
in table 1

with TDegr as the temperature during degreasing, tDegr the
contact time of the degreasing medium with the strip
surface and vGraining the velocity of the strips in the plate
manufacturing lines, i.e. the velocity during electro-
chemical graining. Strip 1 and 2 produced from one mother
strip were tested on the same plate manufacturing line.
The same applies to strip 3 and 4. The different values of
VGraining for strip 1,2 and strip 3,4 are caused by different
characteristics of the plate manufacturing lines.
As can be derived from table 1 the litho-strips degreased
with the inventive method generally show a good appearance
after electro-chemical graining even if the graining
velocity was increased. However, litho-strips degreased
with the inventive method show even better graining
results, because the surface of the litho-strip grained
with the inventive method have a finer, more homogeneous
and more shallow graining structure. This graining
structure provides improved printing characteristics of
the inventive litho-strips. Additionally, the inventive
method provides said improved graining structure even at
higher manufacturing speeds, as can be derived from the
results of strip 1 and strip 2. Strip 1 degreased
conventionally shows merely good appearance results after
electro-chemical graining at a graining velocity of
50 m/min. However, strip 2 degreased with the inventive
method allows 55 m/min graining velocity.
The different graining structures of the conventional and
inventive degreasing method are shown in Fig. 1 and
Fig. 2. Fig. 2 shows, as already mentioned, a microscopic
view of the surface of a litho-strip consisting of the
aluminium alloy A degreased with the inventive method
after electro-chemical graining. Fig. 1 shows the graining

result of the same litho-strip degreased conventionally.
The graining pattern achieved with the inventive method is
finer and more shallow compared to the graining pattern
achieved with a conventionally degreased litho-strip. As a
result, the printing characteristics of the inventive
litho-strips are improved significantly.
The present embodiments of the invention has been achieved
by the addition of 1 % per weight sodium hydroxide. It is
expected that a higher concentration of sodium hydroxide
combined with an decreased contact time of the strip with
the degreasing medium will lead to similar results.

C L A I M S
1. Method of conditioning the surface of an aluminium
work piece consisting of an aluminium alloy, in
particular of a litho-sheet or litho-strip, which
method comprises at least the step of degreasing the
surface of the work piece with a degreasing medium,
wherein the aqueous degreasing medium contains at
least 1,5 to 3 % by weight of a composite of 5 - 40 %
sodium tripolypnosphate, 3 - 10 % sodium gluconate,
3 - 8 % of a composite of non-ionic and anionic
surfactants and optionally 0,5 - 70 % soda, preferably
30 - 70 % soda, wherein sodium hydroxide is added to
the aqueous degreasing medium such that the
concentration of sodium hydroxide in the aqueous
degreasing medium is 0,01 to 5 % by weight,
preferably 0,1 to 1,5 %, more preferably 1 to 2,5 % by
weight,
2. Method according to claim 1, wherein
the time of application the degreasing medium is at
maximum 1 to 7 s, preferably at maximum 2 to 5 s.
3. Method according to claim 1 or 2, wherein
the temperature of the degreasing medium is 50 to
85 °C, preferably 65 °C to 75 °C.

4. Method according to claim 1 to 3, wherein
the pH-value of the aqueous degreasing medium is from
10 to 14, preferably 10 to 13,5.
5. Method according to claim 1 to 4, wherein a litho-
strip is conditioned and the conditioning is
accomplished subsequently to manufacturing,
respectively rolling of the strip whereby the
conditioned strip is reeled on a coil.
6. Method according to claim 1 to 5, wherein the
aluminium alloy is one of the aluminium alloys AA1050,
AA1100, AA3103 or AlMgO,5.
7. Method according to claim 1 to 5, wherein the
aluminium alloy contains the following alloying
constituents in percent by weight:

impurities each less than 0,005 % in sum max.
0,15 %, rest Al
or

impurities each less than 0,005 % in sum max.
0,15 %, rest Al
or

impurities each less than 0,005 % in sum max.
0,15 %, rest Al.

The invention relates to a method of conditioning the surface of a work piece, in particular of a litho- strip or litho-sheet, consisting of an aluminium alloy. The object of the invention to provide a method for conditioning the surface of a work piece and a work piece consisting of an aluminium alloy enabling an increasing manufacturing speed in surface roughening while maintaining a high quality of the electro-chemical grained surface of the work piece with relative low effort related to facility equipment, is solved in that the method of conditioning comprises at least the step of degreasing the surface of the work piece with a degreasing medium, wherein the aqueous degreasing medium contains at least 1,5 to 3 % by weight of a composite of 5 - 40 % sodium tripolyphosphate, 3 - 10 % sodium gluconate, 3 - 8 % of a composite of non-ionic and anionic surfactants and optionally 0,5 to 70 % soda, preferably 30 - 70 % soda, wherein sodium hydroxide is added to the aqueous degreasing medium such that the concentration of sodium hydroxide in the aqueous degreasing medium is 0, 01 to 5 % by weight, preferably 0, 1 to 1,5 % by weight, more preferably 1 to 2,5 % per weight .

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http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=rHXMYEHHGYBMH+YGuS2D5w==&loc=wDBSZCsAt7zoiVrqcFJsRw==

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Patent Number

272431

Indian Patent Application Number

4886/KOLNP/2008

PG Journal Number

14/2016

Publication Date

01-Apr-2016

Grant Date

31-Mar-2016

Date of Filing

02-Dec-2008

Name of Patentee

HYDRO ALUMINIUM DEUTSCHLAND GMBH

Applicant Address

ETTORE-BUGATTI-STR.6-14 51149 KOLN

Inventors:

#	Inventor's Name	Inventor's Address
1	BERNHARD KERNIG	HONINGER WEG 145 50969 KOLN
2	HENK-JAN BRINKMAN	NECKARSTRASSE 40 53175 BONN

PCT International Classification Number

B41N 1/08,C23G 1/22

PCT International Application Number

PCT/EP2007/055586

PCT International Filing date

2007-06-06

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	06115002.5	2006-06-06	EPO