Note: Descriptions are shown in the official language in which they were submitted.
- LO~ TEMPE:E~ATUI~: CLEA~ `R FOR M13TAL SUR~ACES
FIEI D OF THE INV~NTION
This invention relates to a composi-tion and a
process for cleaning metal surfaces and more particularly
relates to an aqueous alkaline cleaning solution containing
a corrosion inhibitor which deters or inhibits etching of
the ~etal sur~ace.
The invention will be described in connection
with the cleaning of tin-plated surfaces, such as tin cans,
which are soiled with organic lubricants that are applied
to the tin surface as drawing aids during cold forming
operations. qlhe invention has, never-theless, broader
applicability.
Cleaning is essential as a preliminary to many
surface finishing operations. It is normally required,
for example, prior to corrosion preventive treatments and
prior to the application of oxganic finishes to the surface,
and is especially important in the case of metal surfaces
to which organic materials have been recently applied as an
aid to cold forming. These materials must be removed in
order to obtain a surface suitably receptive to an organic
or inorganill finish.
- One example of the need for such cleaning is
in the manufacture of two-piece, tin-plated, drawn and
ironed cans. C:Lrcular blanks of tin-plated steel, which,
due to the high cost of tin, generally have only a thin
layer of tin plating, are first cupped and then passed
through several drawing dies to iron the cup in order to
~' ,
form a unitary side wall and can bottom slructure. A can
produced by this process may be characterized as a thin-
walled, thick-bottomed container having a generally uniform
wall thickness, Such cans will be referred to herein as "DI"
(drawn and ironed) cans~ These forming operations are assis-
ted and the dies and metallic surEace protected by the
application of lubricants to the tin-plate surface prior to
or during the forming operation. rrhe lubricants that are
deposited on the tin surface usually consist of various types
of mineral and vegetable oils and heavy metal soaps. Since
it is desired to have a clean surface in order to assure
adhesion of a subsequently applied sanitary lacquer and/or
decorative varnish, the cleaning step after forming is
critical to a successful manufacturing process.
A serious problem with DI tin-plated containers
is that the drawing operation stretches the tin-plate surface,
thereby exposing somé of the underlying meta~ which ex-
posure may lead to corrosion. The underlying metal may be
a ferrous metal, such as iron, iron alloys, and a wide
variety of steels.
A problem with cleaners for tin-plate has been
to obtain a cleaner that will provide a water-break-free
surface without unduly etching the tin and without promoting
corrosion of the underlying metal. A water-break-free surface
is a surface that is sufficiently freed of ~ubricants,
soil, and other contaminants so that it will maintain a
continuous film of water.
3~ 7( ~ L~
Etching results ~rom chemical attack of the
cleaner on the tin surface and results in a rouyhened and
dull surface. Furthermore, etching removes a portion of
the corrosion protectlve tin from the surface, thereby de-
grading the anti-corrosion qualities of the surface and
aggravating the problem of corrosion due to exposure of
the underlying metal. Where a smooth, shiny surface is
desired, such as in the case of a beverage can, etching
and/or corrosion is clearly undesirable.
Another problem with cleaners for tin-plate has
been that they do not protect against conditions on the
processing line where, after drawing and ironing and
cleaning, line stoppage can expose the cleaned cans to the
cleaner for prolonged periods of time. This prolonged
exposure can lead to corrosion of the underlying surface
exposed due to stretching or due to etching, thereby ren-
dering the contalners unacceptable for use. Additionally,
any corrosion and blemishes on the surface will adversely
affect the adhesion of any conversion coating or sanitary
lacquer coating that is applied thereafter.
Alkaline cleaners, such as aqueous solutions of
alkali metal salts of silicates, phosphates, carbonates
and borates, which have been found to be most suitable
for producing the desired water-break-free surface, possess
the undesirable tendency to etch the surface. It has pre-
viously been discovered that the addition of certain com-
pounds to the aqueous alkaline cleaning solutions will help
to inhibit etching of the tin surface under the alkaline
conditions employed,
REPORTED DEVELOP~NTS
Inhibitors, such as the alkali metal salts of
chromates, dichromates and, to a lesser extent, silicates,
have previously been added to the aforementioned aqueous
alkaline solutions to inhibit etching of the tin surface.
The resultant cleaners have generally been applied at
temperatures in excess of 150F. Complete protection of
the tin surface from etching is not always possible with
such inhibitors, especially at a pH above about 12, since
the attack of the alkaline compound on the tin surface
tends to increase with increasing pH. Such cleaners having
a pH below about 12 have less tendency to attack the tin
surface and, hence, the well-known inhibitors are more
effective, but the cleaning action of these lower pH
cleaners is usually slow, making it necessary to treat the
tin surface for a prolonged period of time to effect
cleaning. Additionally, when a chromium compound is used
as the inhibitor, there are problems with toxicity and
environmentally objectionable plant effluents.
A number of patents have been directed to com-
positions and processes for cleaning tin surfaces. The
cleaners disclosed in these patents are applied at tempera-
tures of at least 140F and thus may be characterized as
high temperature cleaners.
U.S. Patent No. 2,836,566 describes a cleaning
composition for tin sur aces that, when added to water,
comprises an aqueous solution of an alkaline metal meta-
silicate; a water-soluble copper salt selected from the
grollp consisting of sulfate, chloride, acetate and
cyanidei an amine selected from the group consisting of
'7~
-
1,3-diamino butane, monoethanolamine, 2-amino-2-methyl
l-propanol and triethanolamine; and soda ash. The solu-
tions have a pH above about 11.8. One example dlscloses
that the tin surface may be cleaned by immersion in the
solution at boiling temperature within a 15-minute period.
The solution temperature and the cleanin~jtime
are economically disadvantageous due to the energy require-
ments for maintaining a cleaning solution at boiling tem-
perature concurrent with the requirement that the object
to be cleaned be immersed for about 15 minutes. Additionally,
the requirement of a copper salt, including copper cyanide,
presents waste disposal and toxicity problems tha-t add to
the cost of the cleaning process employing these solutions
and makes them undesirable for use on beverage cans and the
like. Furthermore, it is possible that when using a solu-
tion containing a copper salt, some copper will be plated
on tne tin surface. This is objectionable since the copper
may be visible and a uniform shiny tin surface is generally
preferred by, for example, manufacturers who purchase cans
to be filled with beverages.
U. S. Patent No. 3,8~8,783 discloses a cleaning
composition that, when added to water, forms an aqueous
solution for cleaning tin-plated ferrous metal surfaces.
Tne aqueous solution contains an alkali metal metasilicate,
a condensed phosphate selected from the group consisting of
tripolyphosphate and pyrophosphate, and borax. The alkali
metal metasilicate is said to increase the detergency of
the solution and to provide added protection of the surface
from corrosion prior to conversiGn coating.
-5-
The cleaning solutions are applied to the surface
for fifteen seconds to about one minute at temperatures of
from about 150 to 190F. The preferred temperatures is
from about 150 to 170F. The pH is maintained at a level
within the range of from about 9.0 to about 10.15. A11
of the examples disclose solutions having a pH less ~han
10 and a temperature of at least 160F.
The solutions do possess certaln disadvantages.
The primary disadvantage is that the solutions must be
applied at temperatures in excess of 150F and thus re-
quire a greater energy expenditure and therefore cost more
to use than would a significantly lower-temperature cleaner.
Furthermore, both borates and phosphates may present environ-
mental problems and, hence, may present plant effluent
treatment problems.
U. S. Patent No. 4,094,701 discloses a process
for cleaning a tin surface without substantially etching
the tin. The process comprises contacting the surface with
an aqueous alkaline solution containing an alkaline compo-
nent which may be an al~ali metal borate, carbonate, phos-
phate, hydroxide, oxide, silicate, or mixtures thereof;
one or more surfactants; and, as an inhibitor, an organic
tannin. The object to be cleaned is sprayed with the
solution at elevated temperature for about one to about two
minutes. The pH of the cleaner is at least 9, preferably
between 10 and 13, and most preferably between 10 and 10.5.
Higher pH values tend to gradually inactivate the tannin.
The patent teaches that temperatures of 140F and upwards
will normally be employed when the cleaner is adjusted to
the preferred pH range. Thus, the patent teaches employing
-6-
~ ~7(~
.
.
the cleaner disclosed therein a-t temperatures in excess
of 140F and at pH values between 9 and 10.5.
The patent discloses i:hat alkali metal ~orates
and phosphates may be used. Both borates and phosphates
may present en~ironmental problems and, hence, may present
plant effluent treatment problems. While the patent dis-
closes a cleaning solution that may be used for cleaning
tin surfaces, without etching, at -temperatures below
boiling and for periods of time less than two minutes,
the use of temperatures in excess of 140F is still
economically disadvantageous.
Thus, there still exists the need for a compo-
sition that may be used effectively on tin surfaces to
produce water-break-free surfaces without etching the tin
at lower temperatures than previously, effectively employed
when applied for periods of about one minute or less and
for periods of time longer th~ have previously been dis-
closed for use without etching in order to realize a sig-
nificant cost savings, reduce the possiblity of etching
and corrosion during line stoppàge, and minimize the ex-
penditure of energy, without the use of components presently
known to be environmentally objectionable.
OBJECTS O~ T~lE INVENTION
It is, therefore, an object of the present
invention to provide compositions, solutions, and a process
for cleaning tin surfaces and,particularly, tin-plated
metal surfaces, so that they are water-break-free without
etching the tin and to do so at lower temperatures than
have heretofore effectively been employed, and without the
use of components presently known to be environmentally
objectionable.
I
,
It is a particular object of the present invent.ion
to provide a low -temperature aqueous alkaline solu-tion for
cleaning tin-plated me-tal surfaces so -tha-t they are wa-ter-
break~free without etching of the -t:in.
It is a fur-ther objec-t of -the present invention -to
provide cleaning compositions and a process for -their use for
cleaning tin-plated metal surfaces at low temperatures -to
produce a water-break-free surface without e-tching the tin.
SU~MARY OF THE INVENTION
In accordance wi-th one aspect of this invention, there
is provided a process for cleaning tin surfaces to subs-tantially
remove soil, lubricants or other con-taminants therefrom without
visibly etching the tin surface by applying to said tin surface
an aqueous alkaline cleaning solu-tion having a pH of about 11
-to about 13 and comprising an alkaline component in an amount
effective to substantially remove said contaminants from the
tin surface and an inhibitor, in an amoun-t effective to inhibi-t
etching of the surface, selected from the group consisting of
substituted benzenes having at least two hydroxy .substituents,
quinones and substituted quinones.
In accordance with ano-ther aspect of this invention,
there is provided an aqueous cleaning solution having a pH of
about 11 to about 13 for cleaning -tin surfaces to subs-tantially
remove soil, lubricants or other contaminan-ts therefrom without
visibly etching the tin surface, at temperatures between about
100F -to about 130F, and comprising an alkaline component,
in an amount effective to substantially remove from the tin
surface contaminants thereon, and an inhibitor, in an amount
effective to inhibit e-tching of the surface, selected from
the ~roup consisting of quinones, substituted quinones, and
substituted benzenes having at least two or more hydroxy
substituents in the ortho, para, meta, symmetric or assymmetric
~.,.,,~ 1
~ ~7~
configura-tions.
DETAILED DESCRIPTION OF THE INVENTION
. . _
The alkaline component in the cleaning solu-tion
useful in the process and composition of this invention
may be any of the compounds known to
- 8a -
.~17()~
the art that produces an alkaline solution when dissolved in water. Prefer-
ably the alkaline component is applied in the form of a compound selected
from the group consisting of alkali metal hydroxides, carbonates and sili-
cates, ammonium hydroxides and carbonates, and mixtures thereof. Particul-
arly preferred as the alkaline component is a mixture of sodium carbonate,
sodium metasilicate and a compound selected from the group consisting of
sodium hydroxide and potassium hydroxide.
The alkaline component is present in the cleaning solution in an
amount effective to substantially remove soil, lubricants or other such COTI-
taminants. Generally, more of the alkaline component will be required whenthe solution is applied at higher temperatures and less will be required
when the solution is applied at lower temperatures. Preferably, the amount
of alkaline component in the solution will be at least about 2 g/l, and more
preferably will be about 3 g/l to about 5 g/l. Greater concentrations may
be employed but the benefit to be gained thereby is generally not signifi-
cant.
The cleaning solution will generally have a pH value within the
range of abou~ 11 to about 13 and may preferably have a pll value within the
range of about 12 to about 12.8. The pH is determined at a solution tempera-
ture of about 27C.
The inhibitor of the cleaning solution useful in the process ofthis invention is a compound selected from the group consisting of sub-
stituted benzenes having at leas* two or more hydroxy substituents, quinones,
and substituted quinones. A mixture of inhibitors can also be used.
Exemplary substituents in the benzene ring include, in addition to hydroxy,
halo, alkyl, carboxy, nitro, cyano and alkoxy. Such substituents are also
exemplary of substituents of the substituted quinone.
Exemplary quinones and substituted quinones useful as inhibitors
in the practice of this invention include 1,2-benzoquinone and 1,4-benzo-
quinone and the substituted quinones according to Formulae II and III.
1 ~ 3
~ ormula II
1~
Rl J~o
ll I Pormula III
R
R3
wherein:
Rl, R2, R3 and R~ are hydrogen, alkyl, alkoxy, hydroxy7 halo, nitro,cyano, or carboxyl; or Rl and R2 form an alkyldienyl group and, together
with the qui~one ring to which they are attached, form a napthaquinone.
Exemplary substituted benzene inhibitors, of particular interest
in the composition of this invention, include polyhydroxybenzenes, such as~
catechol, resorcinol, 1,4-dihydroquinone, 1,2,~-trihydroxybenzene, 1,3,5-
trihydroxybenzene and l,2,4,5-tetrahydroxybenzene.
Preferred inhibitors for use in the process of this invention in-
clude 3,~,5-trihydroxybenzoic acid7 1,2,3-benzene triol and dihydroxy-
benzenes and quinones, such as~ 1,4-benzenediol and l,~-benzoquinone.
The inhibitor is added in an amount effective to inhibit etching
of the surface. Generally, as the concentration of the alkaline component
increases, the concentration of the inhibitor required will also increase.
Also, as will be discussed below,~since "soft" water tends to ba more corro-
sive than "hard'l water, a greater concentration of inhibitor will generally
be required when the cleaning solutions are formulated using soft water than
will be required when formulated with hard waterO Preferably, the amount of
inhibitor in the solution will be at least about 0.02 g/l, and more prefer-
ably will be about 0.02 g/l to about 0.0~ g/l. Concentrations greater than
-10-
~ t7(~
0.06 g/l may be effectively employed but the resultant increase in
cost is not generally offset by a greater inhibition of etching.
It has been discovered that the addition of a poly~
electrolyte to tile cleaning solu~ions of the invention provides a
solution that may be effectively employed regardless of the hard-
ness of the water used to formulate the solution without generally
experiencing precipitation of the calcium and magnesium ions that
cause water hardness. Such precipitation is a problem since it
may result in sediment that may, for example, clog spray nozzles
when spraying is the chosen method of application.
-lOa-
~ ~'7(.~
Polyelectrolytes are high molecular weight
electrolytes of either natural orlgin, such as proteins,
or of a synthetic nature, such as polymerized organic
acids. Since the polyelectrolytes in solution do
not dissociate to give a uniform distribution of positive
and negative ions, as do simple electrolytes, the ions of
one sign are bound to the polymer chain. Thus, Eor
instance, the negative charges may be in the polymer chain,
and only positive ions will be free to diffuse through the
solvent.
Hardness is a characteristic of water
generally accepted to represent the total concentration
of calcium and magnesium ions. Other polyvalent cations
that are seldom present in more than trace amounts may
also contribute to hardness. Determination of hardness
may be made by titration as set forth in "Standard Methods
of Test for Hardness in Water", Designation D 1126-67
(Reapproved 1974) published by the American Society for
Testing and Materials. Hardness may be given in parts
per million (ppm) of calcium carbonate e ~ valent. The higher
the value, the greater the hardness. Water hardness
may vary greatly from one plant site to another.
Generally, water havlng a hardness of less than about
100 ppm may be considered "soft" whereas water having a
hardness above about 100 ppm may be considered "hard".
In scme coastal regions the hardness may be only about
50 ppm to about 100 ppm and may increase to about 300 ppm
where the water runs at some point through limestone
deposits. In some areas of the midwest, the hardness
may be about 400 ppm to about 500 ppm. Precipitation
~ 3~ ~ ~
will generally be experienced to a greateT extent as the hardness
of the water increases. As hardness decreases, the water may tend
to become more corrosive. Therefore, a polyelectrolyte is prefer-
ably, but optionally added to the cleaning solutions of the pre-
sent invention.
Tlle polyelectrolyte, when aclded, may be any of the com-
po~mds known to the art to prevent precipitation o-f the minerals
that cause water hardne$s. If a polyelectrolyte is selected that
does not contain phosphate, certain advantages may be realized.
An important advantage is that the plant effluent will not contain
phosphates since phosphates may be considered environmentally
objectionable. Additionally, the allcali metal tripolyphosphates,
which have previously been employed, may have the deleterious
effect of promoting etching or detinning. Thus, polyelectrolytes
preferred for use in the cleaning solutions of the present inven-
tion are polyelectrolytes such as Gantrez, S-95*, manufactured by
GAF Corporation, and Tamol 960*, manufactured by Rohm and Haas
Company. These polymers do not promote detinning and may inhibit
etching to some extent.
Ihe polyelectrolyte, when added, is preferably added in
an amount effective to substantially prevent precipitation of the
calcium and magnesium ions that are the primary cause of water
hardness. Generally, greater amounts of polyelectrolyte will be
required when the hardness of the water is high than when the
hardness of the water is low. Preferably, the amount of poly-
electrolyte will be at least about 0.1 g/1 and more preferably
from about 0.1 g/1 to about 1 g/1. Concentrations
*Trade Mark
-12-
7v~ L F
in excess of l g/1 may be present in the cleaning solutions
but, generally, higher concentrations will not result in
a significant improvement in the desired effect.
It is preferred but not essential to add one or
more surfactants to the aqueous alkaline cleaning~solutions
of the present invention. Additionally, when a surfactant
is added that is not a low foaming surEactant/ a defoaming
agent is desirably added~ A defoamer is desirable in such
a case since foaming can present a serious problem to a
commercial operation in that it may delay or shut down the
cleaning line. Such materials enhance the performance of
the cleaning solution but are not the essence of the invention
since they are used to perform functions essentially similar
to the function they perform in prior art solutions. The
presence or absence of surfactants has been found to have
no noticeable effect as far as inhibiting or promoting the
etching of a tin surface by the cleaning solution.
:
Exemplary of the surfactants and wetting agents
that can be employed in the cleaning solutions are ethoxy-
lated straight chained alcohols and octyl or nonyl phenoxy
polyethoxyethanol. Generally, nonionic surfactants are pre-
ferred since they are low foaming~
-13-
~-
~.a~7(,),~
When s~rfactants are added, it is preferred that
the cleaning solutions contain at least about 0.2 g/1 of
one or more surfactants. A particularly preferred amount
is from about 0.2 9/1 to about 0.5 g/l.
Tin surfaces may be c]eaned by contacting the sur-
face with the aqueous alkaline c:leaning solutions of the
present invention for a time and at a temperature effective
to remove soil, lubricants or other such surface contaminants
therefrom without visibly etching the tin surface. Generally,
the solution temperature will be at least about 100F. A
preferred range is from about 100~ to about 130F, and more
preferably from about 115F to about 125F. The temperature
employed may tend to be higher for solutions having low
concentrations of alkaline components than for solutions
having higher concentrations of alkaline components. Thus,
the treatment temperature may tend to vary somewhat inversely
with the pH of the cleaning solution.
The time of treatment will generally depend on
the method of application. A preferred method of appli-
cation is spraying and when this method is used the treat-
ment time will tend to decrease as the spraying pressure
increases. ~eans for spraying as presently known in the
art generally operate at spraying pressures of about 25 psi
to about 35 psi and treatment times of about 40 seconds to
about one minute may be sufficient to produce a water-
break-free surface. I~eans for spraying at pressures of
.~ a ~
60 psi to 100 psi are known but no-t generally used at
present and may employ effective tre.atment times of
about 1 to 5 seconds. Spraying is merely exemplary of
the methods of application. Any conventional means known
to the art may be used to contact the tin-plated surface
with the cleaning solution.
The treatment time will also tend to increase
the longer the interval between manufacture of the tin-
plated metal article and the cleaning thereof. With
drawn and ironed tin-plated steel cans, an interval of as
little as fifteen minutes may noticeably result in an
increased cleaning time. Additionally, the treatment
time may vary depending on the type of lubricant used in
the manufacturing process; some lubricants being more readily
removed than others.
Application times of up to about 30 minu~es have
been employed for purposes of determining the extent to
which the present cleaning solutions will inhibit etching
of the tin and it has been determined that a tin-plated surface
may be contacted with the present solutions for up to about
30 minutes without etching the tin. In actual practice,
however, it is contemplated that the shortest time effec-
tive to produce a water-break-free surface without etching
the tin will be employed in applying the present compositions
to the tin surface to be cleaned in order to realize the
greatest cost efficiency. After the tin surface is
treated with the cleaning composition, the surface will
generally be rinsed at least once with tap water and then may be
rinsed with deionized water and dried at elevated temperature,
preferably from about 350 to about 400F.
Thus, surprisingly, the present compositions,
when formulated as an aqueous alkaline cleaning solution
and contacted with a tin-plated me-tal surface for a
period as long as about 30 minutes, will not visi~ly etch the
tin. The present solutions, therefore, provide signifi-
cantly increased protection against etching and corrosion
over the prior art solutions in the event of line stoppage
or similar such prolonged exposures to the cleaning solu-
tions. Additionally, whereas the prior art solutions
have required temperatures in excess of 140F in order to
effectively clean the tin surface to produce a water-
break-free surface withoutvisibly etching the tin, the present
cleaning solutions may be effectively employed at tempera~
tures as low as at least about 100F and may preferably
be employed at temperatures of from about 100F to about
130F. Thus, significant savings in energy costs may be
realized using the solutions of the present invention,
which solutions may be effectively applied at temperatures
as much as 40 degrees less than those of the prior art
solutions to produce water-break-free tin-plated surfaces
that are not visibly etched.
The cleaner of the present invention may be
formulated as an aqueous concentrate or as a solid cleaning
composition to be added to water to produce the aqueous
alkaline cleaning solutions of the present invention.
As an aqueous concentrate the cleaner is formu-
lated such that when the aqueous concentrate is added to
water at a concentration of about 0.5% to about 2% by
volume it produces an aqueous alkaline cleaning solution
having a pH of about 11 to about 13 for cleaning tin surfaces
to substantia:Lly remove soil, lubricants or other contaminants
-16~
therefrom without visibly etching the tin surface, even at low
solution temperatures, and comprises an alkaline component in
an amount effective to substantially remove said contaminants
from the tin surface, and an inhibitor ln an amount effective
to inhibit etching of the surface. The inhibitor is a
compound as defined above. The concentrate may preferably
be added to water at a concentration of about 1~ to about
2~ by volume.
The alkaline cornponent, as defined above, may
preferably comprise up to about 770 grams per liter of
the concentrate and more preferably may be present at
from about 250 to about 500 grams per liter of the
concentrate. The inhibitor may preferably comprise at
least about 2 grams per liter of concentrate and more
preferably may be present at from about 2 to about 6
grams per liter of the concentrate.
- The concentrate may optionally contain a poly-
electrolyte and/or one or more surfactants. The poly-
electrolyte, as defined above, may preferably be added
in an amount effective to substantially prohibit precipi-
tation of the calcium and magne-sium ions that are the
primary cause of water hardness, and more preferably may
be added at from about 1~ to about 20 grams per liter of
concentrate.
- As a solid cleaning composition the cleaner is
formulated such that ~hen '~he solld cleanins composition
is added to water at a concentration of from about 3 g/l
to about 7 g/1 it produces an aqueous alkaline cleaning
solution having a pH of about 11 to about 13 for cleaning
tin surfaces to substantially remove soil, lubricants or
-17-
't~
other contaminants therefrom without visibly etching the tin
surface, even at low solution temperatures, and comprises
an alkaline component in an amount effective to substantially
remove said contaminants rom the tin surface, and an
inhibitor in an amount effective to inhibit etching of the
surface. The inhibitor is a compound as defined ab~ove.
The cleaning composition may preferably be added to water
at a concentration of about 4.6 g/l to about 6.7 g/l.
The alkaline component, as defined above, may
preferably comprise at least about 15% by weight of the
composition. The inhibitor may preEerably comprise at
least about 0.1% by weight of the composition. A particu-
larly preferred concentration is from about 0.5~ to about
2% by weight of the composition.
The composition, as defined above, may optionally
contain a polyelectrolyte in an amount effective to sub-
stantially prevent precipitation of the calcium and mag-
nesium ions that are the primary cause of water hardness.
A preferred concentration for the polyelectrolyte is from
0% to about 10% by weight of the composition and more
preferably from about 3% to about-10% by weight of the
composition.
The cleaning composition may optionally contain,
as diluents and the like, compounds that may be characterti~ed
as inert with respect to any possible positive or negative
influence on the cleaning and non-etching properties of the
cleaning solutions of the invention. Exemplary of such
compounds is sodium sulphate.
-18-
The following examples present illustrative
but non-limiting embodiments of the present invention.
Examples
In each of the following examples, sets of drawn
and ironed tin-plated steel cans (hereinafter, DI cans) were
contacted with the cleaning solution of the particular ex-
ample. The cans were used within 24 hours of manufacture
and were not treated in any way prior to being contacted
with the cleaning solutions of the invention.
Cleaning compositions were prepared having the
concentrations of components indicated in Table I. Each com-
position is identified by a number and a subscript "c".
A specific amount, in grams, of each composition as indicated
in Table II was then added to 6 liters of water to produce
aqueous alkaline cleaning solutions having the concentrations
of components indicated in Table III. Each cleaning solution
is identified by the number of the composition used in its
formulation along with the subscript "sl'. Surfactants were
added in the concentrations indicated in Table III.
The chosen method of contacting the sets of cans
with the cleaning solution in each example was spraying.
The solutions were sprayed at about 25psi for the times and
at the temperatures defined in each example. The cans were
then rinsed with water and visually observed for etching
and appearance.
--19--
'1 ~'71~49L
.
~" t~t~
., oo oo o
X X . X . .X X
~ t~t~
,, X X Xo~ X X
t o o o
o X . X X . .X X
~ Ln
o~ . X X X . X
o o ~ Ln ~
,_ ~, o o~t
oo ~ X X X ~~ ~t Ln X
.,,
3 ~ X X X ~ ~X Ln X
0\o ~ X X X ~t o X Ln X
tn
z ~ ~
o
H Ln ' X X X 'X X X X
E~ ~ cn
o
~,, oLn
g ~ X X X X ~Ln X Ln X
Hl O ~ cr, X X ~ cs~ X xt X
Ln ~ a-
N X X X X X
L~n ~t
~ t~~O
at Oo ~Ln a~
' X X ~ ~ X X
Ln
al R
O :~.rl at
~t ~ ~d
al._~ td h S
o.1~ o o R u~R h O
h O 3 ~ a~ ~ ~
N ,C CJ 13 ~1 Lr~ O
~1 ~ O o o oa~
o l a~ atai h ~n h
R ~ a~
Ln ~ o~ o ~ h .
z s:~ ~ ~ ~ ~o ~ ~ ~R ~
O a ~ ~ Z Z Z o~d ~n
~o
c~
-20-
n
+
~l o
,~,
v u~
+
~ o
o. +
~o
r~
v~ +
cl~
v ~ +
z c:: o
O ~r
H
H O U
+
O ~ O ' .~::
O d'
C.) cn aJ Q
V ~ + ~~0
Q ~ a~ 1 0
1-1 ~ UlV ~7
O ~I.LI
V ~ + ~~ O
u~) ,~ JJ .a
3 ~1
In ~ O
V + r ra
v ~ u~
Ul u
U~ ~ n
~r aJ ~
O ~ ~
H V ~ 0a~ U
H ~ V V
~ U~
m co
É~ V ~ + = '
`I + ~
V
~:
~ ~ .
o a
~l
-1 3 ~:
U~ ~ L~
o ~ ~ a~ -
~ O N ~1
E ~
O to ~ 3
V ~ ~ O
O ~ C~
E~
la J~
U O
,
!
~ ~J 1~ N
u, ~ cn
N X X O X ~-1 ~ X X O X X
51 ~1 ~) N
CO 00 Ci>
X X X O ~ ~ X X O X X
X O X X ~ ~ X X O X X
O oo C0 ~D N t~
O X X X ~ ~ O O X X O
-
O
Z ~n . .. .
H CO o X X X N ~1 N O X X O
O O N
U~ Ul . . . .
~ O X X X ~ ~t X O X O X
¢
V~ ~ ~ ~
~_~ V O X X X ~ ~X O X O X
U.l ~t 1"
H o N t-l
_l U~ . . .
U~ O X X X L~ X X X X X
o ~ X X X X ~ ~ X O X X
H O ooL~
¢ u)
O X X X~I N X O X X
O
U~ .
O X X X~1 ~ X O X X O
O ooU~ ~ .
O X X X ~ l X O X X O
;~ ~
rl
o a~ ~0 0 ~ ~rl
o
~d h S ~ h
:S S 4 u~ Lf~ O R 5-
O ~ O gR u~R ~1 ~ O ~ O
R ~ rl o ~
~ ) O O O L~ h i o
VJ h ~ N N~ h ~ ,i
ho ~ ~ ~ t~ U~ h
I I ~ ~~: I~') O ~ N ~ ~ ~ 4-1 3
~1IJ~ rT~ ' ~ ~ ~~ ~
Z.C e~ .Y O N t`l ~1 R ~ h ~I cd ~ u~
~ ~~ O ~ O ~ O ~ ~ ¢
O ~ ~ ~ ~1 ¢ ~; Z Z D~ c~ P~
o
-22-
~ ~ '7(~
~, X o X
X o X
N
O >~ O X
_(
oo ~D
N
b~ 1~
Zo CO Vl o X O
H
o
~ ~` X X X ~1
H
cZ~ `D
~D X X X ~
Z r~
H O
X X o ~1
a~ ~
r~ U~ Vl
X X O ..
~ ~ 1
H X :'C
~ ~ I~
N X X ~
~ I`_
X X O ~
.9 Y
:~
h O ~ ~ O t~ ~
4~ 0 X~ H O O
~, O ~ ~ ~ h ~ h
0~ ~ I ~ r~
~ l
¢ ~0 ~ d ~ ~
c~ t.) ~ ' h t~ ~ ~: a
U~C~ 4~ o ~ O O O
1 h P~ ~ o ~1 ~4 ~
Z h U)h ~d h ~H ~ ,t ~l o
c~ ~ ~~ P~ m U~ ~`
z
-22a-
.
Example 1
Sets of DI cans were sprayed, one set per solution,
with cleaning solutions ls, 2s~ 3s and 4s' for 10 minutes
at 123F. The results are sumrnarized in Table IV.
TABLE IV
Cleaning Solution Observation of Result
1 No detinning; water-break-
s free cans; bright, rust-free
surface
2s No detinning; water-break-
free cans; bright, rust-free
surface
3s No detinning; water-break-
free cans; bright, rust-free
surface
4s Severe detinning
Example 2
Sets of DI cans were sprayed, one set per test,
with cleaning solution 55for the times and at the tempera-
tures indicated and the results are summarized in Table V.
-23-
7( ~
.
TABLE V
Solution Treatment Observed
Temperature Time Result
125F 1 minute No detinning;
bright, rust-free
surface; water-
break-free cans
125F 30 minutes No~detinning;
bright, rust-free
surface; water-
break-free cans
127F 1 minute No detinning;
bright, rust-free
surface; water-
break-free cans
127F 30 minutes No detinning;
bright, rust-free-
surface; water-
break-free cans
Example 3
Sets of DI cans were sprayed w-th cleaning solutions
65, 7s~ 8S~ and 9s~ one set per test, for the tlmes and at
the temperatures indicated. The results are summarized in
Table VI.
TABLE VI
Cleaning Solution Treatment Observed
Solution Temperature Time Result
6s 120 1 minute No detinning;
bright, rust-free
- surface; water-break
free cans
7s 120 1 minute No detinning; bright,
rust-free surface; water-
break-free cans
120 1 minute No detinning; bright,
rust-free surface; water-
break-free cans
9s 1.20 1 minute No detinning; bright,
rust~free surface; water-
break-free cans
-24-
-
.
T~BLE VI (cont'd)
Cleaning Solution Treatment Observed
Solution Temperature Time Result
~s 120 15 minutes No detinning; bright,
rust-fxee surface; water-
break-~ree cans
9s 120 30 minutes No detinnlng; bright,
rust-free surface; wa-ter-
break-free cans
9s 124 1 minute No detinning; briyht,
rust-free surface; water-
break-free cans
9s 124 15 minutes No detinning; bright,
rust-free surface; water-
break-free cans
9s 124 30 minutes No detinning; bright,
rust-free surface; water-
break free cans
Example 4
Sets of DI cans were sprayed with cleaning solu-tions
10S, 11S, and 12SI one set per test, for the times and at the
temperatures indicated. The results are summarized in ~able VII.
: TABLE VII
Cleaning Solution Treatment Observed
Solution Temperature Time Result
105 125F 1 minute No detinning; bright,
rust-free surface; water-
break-free cans
lls 125F 1 minute No detinning; bright,
rust-free surface; water-
break-free cans
- 12S 125F 1 minute No detinning; bright,
rust-free surface; water-
break-free cans
105 125F 30 minutes No detinning; bright,
rust-free surface; water-
break-free cans
115 125F 30 minutes No detinning; bright,
rust-free surface; water-
break-free cans
-25- .
i
3.~
.
TABLE VII (cont'd)
Cleaning Solution Treatment Observed
Solution Temperature Time Result
12s 125F 30 minutes No detinning; bright,
rust-free surface; water-
break-free cans
105 150F 1 minute No detinning; bright,
rust~free surface; water-
break-free cans
llS 150F 1 minute No detinning; bright,
rust-free surface; water-
break-free cans
125 150F 1 minute No detinnlng; bright,
rust-free surface; water-
break-free cans
0s 150F 30 minutes No detinning; bright,
rust-free surface; water-
break-free cans
llS 150F 30 minutes No detinning; bright,
rust-free surface; water-
break-free cans
12S 150F 30 minutes No detinning; bright,
rust-free surface; water-
break-free cans
Example 5
Aqueous concentrates were prepared having the
concentrations of components indicated in Table VIII. These
concentrates are designated 13 aq and 14 aq.
Aqueous alkaline cleaning solutions 135 and 145
were formulated, respectively, by diluting 11.4 milliliters
of aqueous concentrate 13 aq to 1 liter with tap water and by
diluting 10 milllliters of aqueous concentrate 14 aq to 1 liter
with deionized water. Surfactants were added in the concentrations
indicated. The cleaning solutions had the concentrations of
components indicated in Table VIII.
-26-
r -
~4
Z ~G~
O ~H ~ O X O ~ X X
E ~ J N O O ,-~
o
z
¢
LLl U) ~ X o~ ~ ~ ~ O
C~ ~ ~ ~ ~ O O O O
~D
U~
~ ~ ~ X U) X X X
z
H LLl
H o, O X O n O X X X
~ ¢ ~ ~ ~
~1
¢ ';
h h ~S ~
~0
~¢ a~
h ct
:S h ~ ~
h
H r1 cl l O
h t~ O~ O ~ ~h; 3 ~ ~ ~
q O ~ ~, N ~ V ~d V ~d
~r~ h V ~H O ~H O
~ V ~ h ~ h ,J~
O O C~ ~ O
~ ~ ~ U~
U~ ~ ~ V~h h I ~ ~ ~) h ~
Z a.~ * h Vu~S ~ V h V ~ ~d
~1 ~ :~ ~ ~)I a~ N ~0~ a~ . ,~
Z; r1 ~ O r~ r-l O V4~ 1
O ~ ~ ~ o u~ ~Il~ ~ ~~d ~d g h ~ ~
rY ~ N - ~ ~ H ~ h ~ 4 1 ~S h
O H O ~ td Z~ ~ O ~ ~1 O ~
~ ¢ ~ ~ Z _H 1~ ~~'7Ct~ ~ Cl ~ P~ *
-27-
o~
Sets of DI cans were sprayed with cleaning solutions 13s and 14S,
one set per test, for the times and at the temperatures indicated. The re-
sults are summarized in Table IX.
*ABLE IX
Cleaning Solution Treatment Observed
Solution Temperature Time Result
13 120F 1 minute No detinning; bright,
rust-free surface; water-
break-free cans
145 120F 1 minute No detinning; bright,
rust-free surface; water-
break-free cans
135 124F 30 minutes No detinning; bright,
rust-free surface; water-
break-free cans
135 128F 30 minutes No detinning; bright,
rust-free surface; water-
break-free cans
Example 6
Cleaning solutions 15S~ 165, and 175 were prepared using tap water
and having the concentrations of components indicated in Table X. Solution
175 does not contain an inhibitor and thus, like cleaning solution 4s in
Example 1, is presented for purposes oF comparison.
T~BLE X
COMPONENT CLEANING SOLUTION ~g/l)
155 16S 17s
Inhibitor
1,4-dihydroxybenzene 0.05 0.05 X
Alkaline Compound
2 iO3 4.33 4.33 4 33
Polyelectrolyte
Tamol 960 (manufactured by Rohm
and Haas Company) 0.67 0.47 0.67
-28-
-
TABLE X (cont'd)
COMPONENT CLE~ING SOLUTION (g/l)
15S 165 175
Surfactant
Poly-Tergent S-505-LF
~manufactured by Olin Corp.) 0.42 0.42 0.42
pH 12.4 12.4 12.4
Sets of DI cans were sprayed with cleaning solutions
15S, 165, and 17S, one set per test, at solution temperatures
of 124F for the times indicated. The results are sumrnarized
in Table XI.
TABLE XI
Cleaning Treatment Observed
Solution Time Result
5s 1 minute No detinning; bright,
rust-free surface; water
break-free cans
165 1 minute No detinning; bright,
- rust-free surface; water-
break-free cans
1 minute Spotty whitening;
some detinning
155 30 minutes No detinning; bright,
rust-free surface; water-
breaX-free cans
165 30 minutes No detinning; bright,
rust-free surface; water- I
- break-free cans
175 30 minutes Badly mottled dark
surface; severe detinning
~.
-29-
,
