Note: Descriptions are shown in the official language in which they were submitted.
71483-16
BACKGROUND OF THE INVENTION
1. Field of the Invention -
This invention relates to the cleaning of aluminum
surfaces, particularly drawn and ironed aluminum canscontaining lubricant contaminants, using an alkaline
composition.
2. ~tatement of the Related Art -
Containers of aluminum and aluminum alloys are
manufactured by a drawing and forming operation, com-
monly referred to as drawing and ironing. This opera-
tion results in the deposition of lubricant and forming
oil contaminants on the surfaces of the container. In
_-15 addition, residual a].uminum fine contaminants are depo-
sited on the surfaces, with relatively larger quan-
tities pre~ent on the inside surface of the container.
Prior to processing the container9, e.g. conver-
ion coating and sanitary lacquer deposition, the sur-
-20 faces of the containers must be c]ean and free of
waterbreaks, ~o that no contaminants remain on the sur-
_1_ i~
Case 1~87A
.
faces which will interEere with further processing of thecontainers.
Compositions currently used commercially for cleaning
such aluminum containers are aqueous sulfuric acid solutions
containing hydrofluoric acid and one or more surfactants. Such
cleaning solutions are quite effective and have many advantages.
However, there are also some disadvantages associated with such
acid cleaning compositions. For example, such compositions
are capable of dissolving stainless steel and other iron alloy
equipment commonly utilized in the container cleaning lines.
Also, hydrofluoric acid and fluorides present in spent cleaning
baths and rinse water present an environmental problem in
their disposition.
Alkaline cleaning solutions have been formulated in the
past to try to overcome the above problems, but such alkaline
solutions have instead raised new serious problems of their own
which have mitigated against their commercial use. For example,
when cleaning solutions employing alkali metal hydroxides were
tried, extensive and irregular etching of the aluminum containers
occurred, rendering the containers commercially unacceptable.
Other alkaline cleaning solutions have also been tried
with varying success. For example sritish Patent 2,102,838B
disclosed an alkaline cleaner comprising: 0.5 to 3 grams/liter
(g/1) of an alkali metal hydroxide (such as NaOH); 1 to 5 g/l of
an alkali metal salt of ethylenediaminetetraacetic acid (such as
sodium EDTA); 0.1 to 10 g/l of at least one anionic, cationic, or
nonionic surfactant (such as an anionic surfactant believed to be
composed of two parts of a modified polyethoxylated straight chain
alcohol
-- 2 --
, . ....
~%~
and one part of a linear alkyl succinate, optionally
combined with an alkali metal salt of
2-butoxyethoxyacetate); and optionally further con-
taining 0.6 to 1.3 g/l of an aluminum sequestering
agent (such as sodium glucoheptonate). It may be noted
that the EDTA in this composition does not function as
an aluminum sequestering agent, because of the alkaline
pH of the composition.
While the compositions of the above applications
were excellent aluminum can cleaners, resulting in cans
with virtually no waterbreaks, problems arose when a
production line was interrupted for any length of time
beyond a few minutes. It was found that cans that
stood without after-rising for any length of time deve-
loped severe ~staining, par~içularly at those pointswhere the cans were in contact with each other. Even
the slightest such stain would make the cans unusable,
since they appeared blemished, even aPter subsequent
coating. While most can cleaning operations are by
spraying with a cleaner for a short time such as 10 to
60 seconds, it was also found that times of 60 to 120
seconds, which are occasionally employed, mieht also
result in staining. Additionally, it was found that
where there wasl an usually large amount of lubricant
contaminant, such as more than about 1.5 g/l, the
cleaner was less effective.
A number of patents or published patent applica-
tions disclose alkaline or neutral cleaning com-
positions for metal surfaces, including the following:
3o
U.S. 3,975,215-Rodzewich, assigned to Amchem
Products, Inc.
U.S. 3,888,783-Rodzewich, assigned to Amchem,
Products, Inc.
--3--
~.~9~
U.S. 4,093,566~ assigned to the United States of
America
Japanese 53/149,130, assigned to Nihon Parkerizing
Japanese 51/149,830, assigned to Matsushita Elc.
Ind.
Japanese 50/067,726, assigned to Kurita Water Ind.
Japanese 48/103,033, assigned to Nittan Co., Ltd.
Prior art acid cleaning compositions for cleaning
aluminum surfaces are disclosed in U.S.
4,124,407-Binns, U.S. 4,116,853-Binns, U.S.
~,009,115-Binns, and U.S. 3,969,135-King.
U.S. 4,477,290 assigned to Pennwalt, describes an
alkaline aluminum cleaner having a minimum amount of 6
g/l of NaOH or KOH, which is far in excess of a
desirable amount and will cause smutting. The solu-
tions are stated as having a pH of about 13. Chelating
(sequestrant) agents including sorbitol, gluconic acid,
and glucoheptoic acid are disclosed. A composition of
.6 to 2 g/l of tetrapotassium pyrophosphate, 0.5 to 1.8
g/l of sodium g~uconate, and 0.5 to 1.8 g/l of KOH is
also disclosed, although no EDTA or surfactant is pre-
sent.
SIJMMARY OF THE INVENTION
The invention affords compositions and methods for
cleaning aluminum, particularly aluminum cans con-
taminated with lubricants and other oils, aluminum
fines, etc. The compositions are in the nature of both
initial cleaners and replenisher cleaners, as well as
concentrates used in formulating these cleaners.
The alkaline aluminum-cleaning compositions of
this invention are employed in aqueous cleaning baths,
whose pH must be 11.0 or higher, preferably in the
5range 11.0 to 12.5, most preferably 11.5 to 12.3. The
compositions may be either in powder-form or in the
form of an aqueous concentrate solution. Both powder
and aqueous solution may be in a single component
package, or may have two or three components.
10The ingredients of the inventive compositions
comprise the following:
(a) an alkali metal salt of ethylenediamlnetetraace-
tic acid (EDTA) or of nitrilotriacetic acid (NTA) or a
combination of these salts; present in the bath in 0.1
15to 8.0 g/l (grams per liter), preferably 0.3 to 5.0
g/l, most preferably 1.5 to 3.0 g/l;
(b) at least one surfactant; present in the bath in
0.1 to 10 g/l, preferably 0.2 to 3.0 g/l; and
(c) at least one inorganic alkali metal phosphate;
20present in the bath in 0.1 to 20 g/l, preferably 2.0 to
10.0 g/l, most preferably 4.0 to 8.0 g/l.
It is usually necessary to raise the pH of the
cleaning bath to at least the critical value of 11.0,
for which purposle one optionally should include in the
25powder or aqueous concentrate:
(d) at least one alkali metal hydroxide; present in
the bath in an amount necessary to achieve the desired
pH of above 11, preferably in an amount of up to 5 g/l.
Further optional ingredients are:
30(e) a second inorganic salt; which may be present in
the bath in an amount in g/l up to one-half the amount
of inorganic alkali metal phosphate (ingredient c)
which is present; and/or
(f) a second aluminum sequestering agent (other than
35ingredient a); which may be present in 0 to 10 g/l,
--5--
~..29~
preferably 0.5 to 10 g/l, most preferably 0.6 to 1.3
g/l .
Because the compositions of this invention are
used primarily for cleaning aluminum cans in a produc-
tion line~ and in the final form of an aqueous cleaningsolution into which the unfinished cans are dipped, or
with which they are sprayed, quantities of ingredients
are stated in terms of grams per liter of the complete
aqueous cleaning solution. Because of the nature of the
various composition ingredients, they may be added to
the aqueous cleaning bath individually, all at once, or
in any combinations.
Where the ingredients are added in their essen-
tially dry (powder) form, they are generally physically
compatible with each other, although where a liquid
surfactant is used, it may be advantageous to add it
separately. Adding powder-form ingredients has the
advantage of lighter weight in transportation, since
the water is absent. However, powders usually must be
premixed with water for ease of addition.
In a preferred embodiment, the ingredients are
added in the form of aqueous solutions. Advantages of
using such solutions are ease of handling, bulk storage
capability, andl the avoidance of premixing. The at
least one surfactant may tend to separate from the
other liquid ingredients, in which instance it simply
should be added separately.
Because the pH of the cleaning bath is critical,
variations in pH (caused by extraneous factors such as
the ambient pH of the bath water) must be capable of
adjustment~ The easiest way to adjust the pH is by
varying the amount of alkali metal hydroxide. For this
reason, it generally is advantageous to add the alkali
metal hydroxide separately. Thus, a two-component or
even three--component composition package is generally
--6--
9~
advantageous, although a one-component composition package is
feasible.
Other -than in the operating examples, or where o-therwise
indicated, all numbers expressing quantities of ingredien-ts,
reaction conditions, or defining ingredient parameters used
herein are understood as modified in all ins-tances by the
term "about".
DETAILED DESCRIPTION OF THE INVENTION
The alkali metal salt of either the e-thylenediami-
netetraacetic acid or nitrilotriacetic acid is preferably a
sodium salt, although potassium and lithium salts can also be
employed. The salt is preferably the di-, tri-, or, in the
ease of ethylenediaminetetraacetic acid the tetra-alkali metal
salt, a mixture of such salts can be used. The mono-alkali
metal sal-t can be used, but tends to be somewhat less soluble in
the concentrates of the invention. In general, the alkali metal
salts of the ethylenediaminetetraacetic acid and the nitrilo-
triacetic acid can be substituted, one for the other, on a
mol per mol basis.
The surfactant can be anionic, cationic or nonionic
and combinations of two or more surfactants can be employed.
Examples of surfactants that can be used in the cleaning
solutions of the present invention are disclosed in columns 6 and
7 of United States Patent ~,116,853-Binns.
The following speclfic surfactants and/or combinations
thereof are preferred in the practice of the invention.
(A) nonylphenoxy polyethoxy e-thanol (sold by Rohm and
Haas Co. under the trade mark "Trlton" N 100).
(B) a modified polyethoxy adduct (sold by Rohm and
-- 7 --
~1 ~9~
Haas Co. under the trademar~ "Triton" CF 76).
(C) a nonionic believed to be an alkyl polyethoxy-
lated ether tsold by Jefferson Chemical Co. under the
trademark "Surfonic" LF 17).
5(D) an anionic believed to be comprised of two
parts of a modified polyethoxylated straight chain
alcohol and one part of a linear alkyl succinate (sold
by Rohm and Haas Co. under the trademark "Triton"
DF-20).
10(E) a nonionic believed to be a modified ethoxy-
lated straight chain alcohol (sold by BASF Wyandotte
Corp. under the trademark "Plurafac" D-25).
(F) a nonionic believed to be an ethoxylated
abietic acid derivative + 15 E.O. (sold by Hercules,
0 15Inc. under the trademark "Surfactant AR 150").
(G) a nonionic believed to be a block copolymer of
about 90~ polyoxypropylene and about 10~ polyoxyethy-
lene (sold by BASF Wyandotte Corp. under the trademark
"Pluronic" 31R1).
20(H) a combination of (D) with an alkali metal salt
of 2-butoxyethoxyacetate (preferably sodium, although
potassium and lithium may be employed).
Various combinations of the above surfactants (A)
through (H) may be used, some of which are preferred.
25Thus, a combination of (A) and (C) is most preferred,
while a preferred combination is (A) and (B) Other
useful combinations are (C) and (F), and (H). When any
combination of surfactants is employed, it is preferred
that each surfactant is present in 0.1 to 5 g/l, in the
30cleaning solution. A defoamer may also be present.
The above preferred surfactants and surfactant com-
binations are in fact much preferred for use in the
present cleaning solutions based on their ability, par-
ticularly when an aluminum sequestering agent is also
35present, to contribute to preventing discoloration
--8--
0~.~
(staining) of those aluminum cans that stand wet with
the cleaning solution during periods of line stoppage.
It is believed that this is because the surfactants wet
the can surfaces sufficient to prevent the formation of
a meniscus between the cans or at least to reduce any
such meniscus in size. However, with the inorganic
salts according to this invention added to the cleaning
solution, the staining problem appears to be obviated
regardless of the surfactant.
The second aluminum sequestering agent optionally
(but preferably) included in the cleaning solutions of
the invention can be any compound known for its ability
to sequester aluminum in aqueous alkaline solution.
Examples of such compounds include sorbitol, an alkali
metal (e.g. sodium) gluconate, an alkali metal (e.g.
sodium) glucoheptcnate, and an alkali metal (e.g.
sodium) tartrate, with sorbitol and sodium glucohep-
tonate being preferred.
The useful inorganic alkali metal phosphates are
sodium tripolyphosphate, sodium pyrophosphate, sodium
hexametaphosphate, trisodiumphosphate, sodium
phosphate monobasic, and sodium phosphate dibasic as
well as corresponding potassium and lithium salts.
Any of the phosphate salts or their combinations,
which are critical to this invention, may be used. In
descending order of preference, these salts are (a)
tripolyphosphates, (b) pyrophosphates, (c) hexame-
taphosphates or trisodium phosphates, and (d) all of
the remaining salts. The sodium salts are always pre-
ferred, aLthough the potassium salts and even thelithium salts may also be used.
The second inorganic salts which optionally may be
used include sodium carbonate, sodium nitrate, sodium
sulfate, sodium alurninate, and corresponding potassium
or lithium salts.
~l.X9~
The alkali metal hydroxide which is used herein if
necessary to adjust the pH of the composition to
within the required ranges, may be sodium hydroxide
(caustic soda), potassium hydroxide (potash), lithium
hydroxide, or their mixture. Sodium hydroxide is pre-
ferred. Where potassium hydroxide is used, the amounts
of other ingredients may be reduced, although still
within the above parameters. It may also be necessary
to increase the pH while a production line is running,
in order to prevent staining in case of line stoppage.
This can be done by titering the hydroxide addition
upward, starting from a minimal amount, until accep-
tably clean cans are obtained. Since the ingredients do
not react with each other prior to their cleaning of
the aluminum surfaces, they may be added all together,
individually, or in any combination. Thus, a preferred
concentrate is a two-package combination, the first
package containing all ingredients except the alkali
metal hydroxide and the second package containing the
hydroxide with, optionally, some or all of the inorga-
nic salt. When the cleaning solution is prepared from
the concentrate, water is added to the first package so
that the various ingredients therein are in the con-
centration rangles set forth herein and the second
package containing the alkali metal hydroxide is
dissolved in the water before, after, or simultaneously
with the first package if necessary to adjust the pH to
at least 11, preferably 11 to 12.5, more preferably
11.5 to 12.3. When it is desired to include all ingre-
dients in a ~ingle concentrate package, it may bestirred or shaken just prior to rnetering a given amount
or it may be supplied in containers small enough so
that the entire container content is used at once.
The processes of the invention comprise contacting
the aluminum or aluminum alloy surfaces to be cleaned
-10-
~ ~9~
with the aqueous cleaning compositions of the invention
using any of the contacting techniques known in the
art, such as conventional spray or immersion methods,
spraying being preferred.
The temperature of the cleaning composition should
be maintained within the range 80 to 150F ( 27 to 66
C), preferably 90 to 140F ( 32 to 60C), most pre-
ferably 100 to 130F (38 to 55C).
The treatment time may vary 7 depending upon the
nature of the aluminum production line. Such times are
generally 10 to 120 seconds, preferably 10 to 60
seconds.
Following the cleaning step, the aluminum surfaces
are rinsed with water to remove the cleaning solution.
The aluminum surface may then be treated with coating
solutions or siccative finish coating compositions well
known to the art. Also, prerinses of the aluminum sur-
faces with water prior to the cleaning step is some-
times beneficial in reducing the amount of contaminants
that would otherwise enter the cleaning bath.
Spent cleaning solutions and rinse waters present
few problems in their safe disposition. For example,
the alkali metal salts of ethylenediaminetetraacetic
acid are readilyloxidized to environmentally relatively
harmless components by treatment of the spent cleaning
solutions with small quantities of peroxides such as
hydrogen peroxide. To render any alkali metal
hydroxide which is present harmless, water containing
hydrochloric acid can be added until a pH of about 7 is
obtained.
~.~g$~
EXAMPLES
The following examples, although not intended to
be limiting, are illustrative of this invention
5In all of the following exa~nples, the alkaline
hydroxide was NaOH used in a constant ratio of 1 g/l,
the EDTA was sodium EDTA used in a constant ratio of
2.5 g/l, and the aluminum sequestering agent was sodium
glucoheptonate and was always present in a rat.io of 1
10g/l. The inorganic and phosphate salts were varied, as
were their amounts. Some tests were run without any
salts, for comparison purposes. (See Examples C-1 to
C-7) The surfactant used in all of these tests was a
combination of 3:5 parts of (A) and (C), althouth the
15 amounts used were varied. Inone comparative test, no
surfactant was used and the inorganic salt was sodium
tripolyphosphate. While this composition had some uti-
lity, the amount of tripolyphosphate had to be
increased to the point where it could not be dissolved
20in the make-up concentrate and therefore had to be
added as a separate solution. (see Example 2).
Each of the baths were run in a laboratory
carrousel washer with a prewash of water at 145F (63C)
for 30 seconds with a 20 second blow-off and a wash at
25135F (57C) fo~ 15 seconds followed by a 30 second
blow-off.
Test Criteria
The tests were all run on two-part 3004 alloy alu-
30minum cans (without tops) which had been drawn and
ironed and which were covered with aluminum fines and
drawing oils. The cans were treated in circular
groupings of fourteen cans, ~o that each can was in
constant contact with at least two other cans.
35The percentage of waterbreak free surface (~ WFS)
-12-
~l.29~
was determined as follows. A~ter the can~ are treated
and washed, they are dipped into a saturated sodium
sulfate bath kept at 150F (66C). After excess water
runs off ~10 seconds) they are flash dried in an oven
at 300C. Where waterbreak is evident on a can, the sur-
face will be clear of salt (i.e. silver). Where the
surface is waterbreak free, it will be covered with a
coating of salt, and will appear white. The percentage
of white to silver may be determined visually, with an
optical scanner, or by any other means. 100~ means
that the surface is completely white (i.e. waterbreak
free). This test is extremely rigorous, and a percen-
tage of at least 70~ is needed to be within the scope
of this invention, at least 80~ being preferred, and at
least 90~ being most preferred. An acceptable test
result means that a can will be waterbreak free for
most practical purposes, in a production line.
The stain (blemish) is usually brown and may be
measured visually or by a suitable scanning device.
Once such device is a "Stain Scanner" which measures
the amount of light reflected off a can dome. Light is
transmitted by means of optical fibers to a chamber,
where it is reflected off a can to a photovoltaic cell.
The intensity of the reflected light is proportional to
the brightness of the can surface. A millevolt meter
is used to measure the output of the photovoltaic cell.
The light is adjusted to a standard with a variable
rheostat. The standard in this instance i3 300 mv.
After the cans are washed and allowed to dry, a reflec-
tance measurement is taken. The bath used to treat thecans is then poured into the (concave) dome of the can.
It is then heated in an oven at 200C for 5 minutes.
The cans are then rinsed and dried. A second reflec-
tance measurement is then taken and the result compared
with the first. The differential (dSS) determines the
-13-
~..X9~
amount of stain. The result must not be a negative
number, which would indicate staining. The most
desireable result for stain prevention is 0 or close to
0, indicating little or no change.
Foaming may be a problem with some cleaner com-
positions. When aluminum cans are sprayed, the residue
solution is collected in a tank below the suspended
cans. This residue solution is then recirculated to
the sprayers, in a continuing operation. An excess of
foaming (i.e. over the top of the tank) may result in a
loss of treating composition as well as undesireable
contamination. The control of foaming is therefore
very desireable. To test for foaming a single can
washer was used. It was filled with 4 l of cleaning
bath solution, and the temperature set at 135F
(57C). The bath was sprayed for the indicated time
and the foam level was recorded in liters of foam.
After 10 minutes of spraying, the foam was allowed to
decay for 10 minutes and the level was again recorded.
-14-
~.~9~o~
Examples 1-29 (including comparative) Sodium tripo-
lyphosphate was used as the nonorganic salt.
TABLE I
¦ Example¦ TPP ¦ Surfactant¦ ~ WBF ¦ dSS¦ Foamin~
¦ (g/l)¦ (g/l) ¦ ¦ ¦ lmin¦ 3min¦ 5min¦ 10min¦ 10min Decay
¦ C-1 ¦ 0 ¦ 1.2S ¦ 23.6 ¦ -23 ¦ .5 ¦ 1.1 ¦ 1.4 ¦ 2.4 ¦ 1.0
C-2 1 0 1 3.75 1 4~.5 1 -29 1 .8 1 1.6 1 2.0l2.6 1 .8
C-3 1 0 1 6.25 1 60.5 1 -36 1 3.4 1 *
C-4 1 0 1 7.5 1 78.6 1 -36 1 5.1 1 *
C-5 1 0 1 8.75 1 82.9 1 -34 1 3.8 1 *
C-6 1 0 1 1205 1 73.3 1 -36 1 1.8 1 2.9 1 3.6 1 4.1 1 .2
C-7 1 0 1 15.0 1 57.7 1 -37 1 .9 1 .5 1 .4 1 .4 1 .1
8 _ 1 4 1 1.25 1 81.2 1 +1 1 .5 1 1.0 1 1.2 1 1.8 1 .8
9 ¦ 4 ¦ 2.5 ¦ 89.9 ¦ +1l1.1 ¦ 2.1 ¦ 2.6 ¦-3.1 ¦ - .8
10 1 4 1 5.0 1 88.3 1 +2 1 3.8 1 *
11 1 4 1 7.5 1 93.9 1 +0 1 .8 1 2.2 1 2.5 1 2.6 1 .2
12 1 4 1 8.75 I g2.0 1 +3 1 .4 1 1.2 1 1.6 1 2.0 1 .2
13 1 4 1 10.0 1 90.3 1 +1 1.4 1 .3 1 .3 1 .4 1 .1
14 ¦ 4 ¦ 12.5 1 88-3 ¦ +3 ¦.ll ¦ .2 ¦ .2 ¦2 ¦ .1
15 ¦ 4 ¦ 15.0 ¦ 76.3 ¦ +4 ¦.2 ¦ .2 ¦ .2 ¦_ .2 ¦ 0
16 ¦ 8 ¦ 1.25 ¦ 84-3¦ +8 ¦ .8 ¦ 1.3 ¦ 1.6 ¦ 2.2 ¦ .8¦ 17 ¦ 8 ¦ ? 5 ¦ 90~5 ¦ +8 ¦2.1 ¦ 4.1 ¦ 5.8 ¦6.2 ¦ .4
! 18 1 8 1 3.7~5 193-6 1+9 l 3.4 l *
19 1 8 1 6.25 1 95.71 +8 1 2 1 .4 1 .4 1.4 1 0
1 20 1 8 1 8.75 1 92.21 +6 1 .2 1 .2 1 .2 1.2 1 0
¦ 21 ¦ 8 ¦ 10.0 ¦ 96.5 ¦ +8 ¦.2 ¦.2 ¦ .2 ¦ .2 ¦ 0
22 ¦ 12 ¦ 1.25 ¦ 90-4¦ +5 ¦ 7 ¦ 1-5 ¦ 1.7 ¦ 2.8 ¦ .7
23 ¦ 12 ¦ 2.5 ¦ 93.4 ¦ +7 ¦2.6 ¦6.3 ¦ #
24 1 12 1 5.0 1 93.6 1 -~5 1.2 12 1 .? I .2 1 0
¦ 25 ¦ 12 1 7.5 ¦ 93.5 ¦ +5 ¦.2 ¦.2 ¦ .2 ¦ .2 ¦ 0
26 ¦ 16 ¦ 1.25 ¦ 91.2¦ +5 ¦ 1.0 ¦2.1 ¦ 2.8 ¦ 3.5 ¦ .4
27 ¦ 16 ¦ 2.5 1 95-4 1 +9 ¦2-8 ¦ * l l l
1 28 1 16 1 5.0 1 94.0 1 ~9 1.2 1 .2 1.2 1 .2 1 0
¦ 29 ¦ 20 ¦ 0 ¦ 81.8 ¦ +5 ¦.5 ¦ .8 ¦1.0 ¦1.8 ¦ 0
* over top at 2 min.
# over top at 4 min.
-15-
~2~
Examples 30 to 58 (includin~ comparative) Various other
nonorganic salts were used.
_ABLE 2
¦Example¦ salt(amount g/l) ¦~ WBF ¦ dSS ¦ Foa~in~ l
¦ lmin¦ 3min¦ 5min¦ 10 min¦
¦C-30 ¦ sodium carbonate 4 ¦ 83.1 ¦ -20 ¦ 2.5 ¦5.1 ¦ 7.0 ¦ (a)¦~-31 ~ sodium carbonate 4 ¦ 83.2 ¦ -19 ¦ 1 3¦2.5 ¦ 7.9 ¦ 3.4¦C-32 ¦ sodium carbonate 12 1 96-3 ¦ -15 ¦ .7 ¦1.5 ¦ 1.9 ¦ 2.1
¦C-33 ¦ sodium carbonate 12 1 93.4 ¦ -10 ¦ .1 ¦ .1 ¦ .1 ¦ .1
¦C-34 ¦ sodium
¦ ¦hexametaphosphate 4 ¦ 80.0 l -3 ¦ .8 ¦1.5 ¦ 2.0 ¦ 2.3
¦ 35 ¦ ~ " " 4 ¦ 88.0 ¦ 0 ¦ 4.7 I(b) ¦
36 1 ~ 12 1 80.2 1 ~2 1 1.5 1 2.7 1 3.5 1 4.3
1 37 1 ~ - 12 ¦ 86.5 ¦ +4 ¦ 3-4 ¦(c) ¦_
¦C-38 ¦ sodium nitrate 4 ¦ 84.3 ¦ -36 ¦ 1.7 ¦ 3.5 ¦ 4 5 ¦ 5-7
¦C-39 ¦sodium nitrate 4 ¦ 89.2 ¦ -41 ¦ 3-8 ¦(b) ¦
¦C-40 ¦ sodium nitrate 12 ¦ 60.2 ¦ -41 ¦ 3-5 ¦7-1 ¦ (d~ ¦
¦C-41 ¦ sodium nitrate 12 1 78.7 ¦ -44 ¦ .7¦ 1.3 ¦ 1.9 ¦ 2.1¦C-42 ¦ sodium sulfate 4 ¦ 57-9 ¦ -25 ¦ 1.7¦ 3.5 ¦ 4.7 ¦ 6.4
¦C-43 ¦ sodium sulfate 4 ¦ 72.8 ¦ -25 ¦ 3.5¦ 1.2 ¦ (e) ¦
¦C-44 ¦ sodium sulfate 12 ¦ 58.6 ¦ -26 ¦ 2.5¦ 5.6 ¦ (f) ¦
¦C-45 ¦ sodium sulfate 12 1 73.2 ¦ -35 ¦ .2¦ .2 ¦ .2 ¦ .1
¦ 46 ¦tetrasodium
¦ ¦pyrophosphate 4 ¦ 9-3 1 +7 ¦ 1-3¦ 2-5 ¦ 3-2 ¦ 4-0
47 I " " 4 1 97.1 1 +12 1 4.5 1 (g) I
¦ 48 ~ 12 ¦ 94.0 ¦ ~11 ¦ 2.6 ¦6.9 ¦ (h) ¦
1 " ~ 12 1 96.8 1 +14 1 .2 1 .2 1 .2 1 .2
~-51 ¦trisodium phosphate 4 ¦ 97 1 ¦ -17 ¦ 2.1¦4.9 ¦ 6.8 ¦ (i)¦C-52 Itrisodium phosphate 4 ¦ 92.3 ¦ -23 ¦ 2.8¦4.3 ¦ 5.1 ¦ 5.9¦ 53 ¦trisodium phosphate12 ¦ 97.3 ¦ +5 ¦ 2.1¦ 2.8 ¦ 3.9 ¦ 4.5
¦ 54 ¦trisodium phosphate12 ¦ 96.1 ¦ 0 ¦ 1 ¦ 1 ¦ 1 ¦ l
¦C-55 ¦ sodium aluminate 4 ¦ 64.3_ ¦ -21 ¦ .5 ¦ 1.1 ¦ 1.5 ¦ 2.3¦C-56 ¦ sodium aluminate 4 ¦ 47.0 1 _ 6 ¦ 1.6 ¦ 2.9 ¦ 3.9 ¦ 6.4
¦C-57 ¦ sodium aluminate 12 1 55.4 ¦ -20 ¦ .5¦ 1.1 ¦ 1.1 ¦ 1.9
¦C-58 ¦ sodium aluminate 12 ¦ 79.9 ¦ -11 ¦ 2¦ 3 ¦ 3 ¦ 3
(a)over top at 6 min (b) over top at 2 min (c)over top at 2.25 min
(d)over top at 3.25min (e)over top at 4min (f) over top at 5min.
(g) over top at 3 min (h) over top at 3.5 min(i) over top at 9 min.
-16-
Evaluation of Test Results
As will be seen from Table 1, all examples
according to this invention (nos. 8 - 29) showed
excellent to acceptable stain test results, where all
examples without any inorganic phosphate salts (C-1 to
C-7) showed severe staining. Furthermore, as can be
seen by comparing the ~ ~BF for a given amount of sur-
factant, the results are always better when the inorga-
nic phospate salt is included for example, taking the
best result for the absence of the inorganic phosphate
salt (Ex. C-5) in which the surfactant is present in
8.75 g/l~ and comparing this result with Examples 12
and 20, it can be seen that the results according to
this invention are always superior. In fact, the com-
positions acording to this invention may employ lesssurfactant, replacing it partially with the lower cost
inorganic phosphate salt, which is a great advantage.
An interesting observation is that excessive foaming
without the inorganic phosphate salt starts at a sur-
factant level of 6.25 (Ex. C-3) and continues through a
level of 8.75 (Ex. C-5). In striking and desireable
contrast, the excessive foaming with the inorganic
salt is of a much shorter range, as indicated in
Examples 10, 18, 23, and 27, and occurs at much lower
surfactant levels. This permits, the addition of
larger amounts of surfactants (when the inorganic
phosphate salts are present) to overcome specific pro-
duction problems which may occur. Particularly
striking is that Ex. 29, which used no surfactant at
all, achieved a satisfactory ~ WBF and dSS/ Thus, the
surfactant may be eliminated entirely, although then it
is preferred that it be used in 1 to 3 g/l quantities.
Table 2 demonstrates that only some inorganic
salts are useful for this invention. All of the salts
in Table 2 were chosen because they were thought likely
to be effective. However, as can be seen, those labeled
comparative examples (sodium carbonate, sodium nitrate,
sodium sul~ate, and sodium aluminate) produced severe
staining. Marginally acceptable salts include triso-
dium phosphate (which i9 aoceptable in larger amounts),and sodium hexametaphosphate (which gave mixed results
at lower amounts). Clearly, the tetrasodium
pyrophosphate produced excellent staining results, and
is less preferred than the sodium tripolyphosphate only
because the latter is more soluble. It should be noted
that the salts in the comparative examples were all
satisfactory in the foaming tests, and it may therefore
be possible to employ them in admixture with the salts
according to this invention, especially where such
admixtures are cost effective.
It is of course, known in the art that the initial
make-up cleaner composition has all ingredients in the
desired quantities, but that these ingredients are con-
sumed in differing proportions. Thus, when the
cleaner solution is replenished, the ingredients are
added in proportions different from the initial solu
tion, so that the initial ingredient proportions are
maintained.
All of the above examples are directed to showing
that using the compositions of this invention will
avoid the serious problem of staining caused when the
can cleaning production line is stopped while the cans
are in contact with the cleaning solution. The
following examples demonstrate that the cleaning com-
position of this invention also produces superiorcleaning results.
-18-
~ ~9~
CLE~NING EXAMPLES
In order to demonstrate that the inventive alka-
line aluminum-cleaning composition not only avoided
problems but also cleaned aluminum cans satisfactorily,
5 the compositions disclosed in Table 3, below, were pre-
pared and used to clean aluminum can blanks. The
pre~ash was at a temperature of 120F (49C) for 30
seconds, followed by a wash with the following com-
positions at 120F (49C) for 35 seconds, and then by a
rinse with deionized water at ambient temperature. All
ingredients below are in g/l.
Table 3
¦Example ¦TPP ¦ EDTA ¦NTA ¦seq. ¦ surf. ¦ NaOH
l l ¦ Na Salt ¦Na Salt ¦agnt.¦ ¦present¦
¦C-59 ¦ 4 ¦ 8 ~ 1 1 I no
¦ 60 ¦ 4 ¦2. 5 1 ~ 1 ¦ yes
¦ 61 1 4 I _ ¦ 1.65 ¦ 1 ¦ 1 ¦ yes
L
¦ pH ¦ Reflectivity
¦ ¦ interior¦ exterior¦ ~WBF ¦
¦ 10 - 751 201 ¦ 356 ¦ 98 - 4 ¦
¦ 12.0 ¦ 245 ¦ 369 ¦ 99.7 ¦
1 12.0 1 240 1 369 1 99.4
In comparative example C-59 the pH was below the
minimum of 11 required according to the invention. As a
result, the interior reflectivity value was too low,
indicating that the can was not clean enough. The base
line reflectivity value~ were 169 for interior and 329
for exterior. At an interior reflectivity of above 235,
35 there was no visible signs of fines, indicating that
- 1 9 -
-
the can was acceptably clean. The interior reflectivity
of example C-59 was completely unacceptable. The par-
ticular can blanks tested were obtained from National
Can Co., Piscataway, New Jersey, U.S.A. It should be
noted that the acceptable interior reflectivity value
will vary for each type of can configuration, each type
of production equipment, ambient water, cleaning con-
ditions, and the like. Therefore this value should be
taken only as a comparative for identical cans tested
under identical conditions. The exterior reflectivity
values were acceptable for all three examples. The
secondary sequestrant (seq.) used was sorbitol. The
surfactant (surf.) used was a combination of A and C in
a weight ratio A:C of 3:5. Although the pH in example
C-59 was too low with the use of 8 g/l of EDTA Na salt,
this amount may be enough where the ambient water has a
sufficiently high pH to result in a cleaning bath pH of
at least 11. The EDTA Na salt and NTA Na salt were each
present in the equimolar amount of .006 mols. As can be
seen, both of these salts gave acceptable results.
-20-
