Note: Descriptions are shown in the official language in which they were submitted.
CA 02193825 1996-12-23
NON-SILICATED SOFT METAL SAFE PRODUCT
FIELD OF TIC INVENTION
The present invention relates generally to stable, silicate-free, soft metal
safe,
alkaline cleaners and ore particularly, to stable, silicate-free, soft metal
safe, alkaline
cleaners comprising calcium ions and surfactants containing hydroxyl and/or
carboxylic
acid groups, as well as alpha-hydroxy carboxylic acids.
BACKGROUND OF THE IlIIVENTION
It is common practice to use sodium silicate as a corrosion inhibitor in
alkaline
cleaners. Silicate, abundant and inexpensive to produce, provides soft metals
such as
aluminum and its alloys with effective protection against corrosion. Silicate
also functions
as a builder and detergent due to its affinity for clay and other inorganic
soil particles.
For silicate to act as an effective corrosion inhibitor in alkaline cleaners,
the ratio of
SiOZ:NazO must be 1, which means that the causticity of alkaline cleaners is
kept low.
However, low alkaline cleaners do not sufficiently remove tenacious soils such
as food
soils. As a result, alkaline cleaners when formulated with silicate, have
limited use due to
their low causticity which restricts their use to light-duty cleaning only.
Lowering the
ratio of SiOz:Na20 to less than 1 by increasing the causticity, renders the
formulation
aggressive and unsafe to apply to soft metal surfaces. Furthermore, silicated
cleaners pose
severe rinsing problems due to deposition of silicate film oa metal surfaces.
In addition,
silicate deposition tends to increase on hot surfaces such as those
encountered in food
processing plants. Such deposits are unsightly and difficult to remove, and
are therefore
unacceptable in the food industry.
The principle of combining alkaline earth metal ions (e.g. Cap+, Ba2+ and
Srz+)
with certain s~u~face-active agents such as alkylpolyglucosides and/or
emphoteric
surfactants containing one or more amine groups, to inhibit the attack of
hydroxide ion on
alkali sensitive materials, has previously been reported in US Patent No.
3,553,095 in
which a detergent composition is disclosed for cleaning alkali sensitive
substrates. The
composition generally inhibits corrosion by using a mixture of metal ions
combined with
certain surfactants and specifically discloses a cleaner composition
containing sodium
hydroxide, an alkyl glucoside surfactant, a calcium source and an a-hydroxy
carboxylic
acid such as malic acid. Although the principle of the corrosion inhibiting
system set
forth in the '095 patent has proven to perform well for its intended purpose,
it is difficult
to introduce this mixture into alkaline cleaners which contain ingredients
such as caustic,
surfactants, and/or other builders, without inducing precipitation of
hydroxides of alkaline
AMENDED SHEET
tPEAIEP
CA 02193825 1996-12-23
L, i , J ~~ L
la
earth metals, disturbing the stability of the cleaners or adversely affecting
the effectiveness
of the corrosion inhibiting system.
Theoretically, protection against corrosion is based on the presence of
solvated
alkaline earth metal ions which must be kept as such or the system will lose
its
effectiveness as a corrosion inhibitor; i.e,, the formulation must coatain
builder
AMENDED SHEET
IPEAJEP
CA 02193825 2002-08-16
2
such as strong chelating agents {e.g. EDTA and its analogs) which could bind
with the
alkaline earth ions. In addition, alkaline earth metal ions such as Ca''+
precipitate under
alkaline conditions forming hydroxides such as calcium hydroxide, which is a
white
precipitate. Although it may be possible to keep the precipitate suspended in
an alkaline
formulation for a short period of time, eventually it will settle out and thus
a long shelf
life can not be achieved. (here thus remains a deed for stable, silicate-free,
soft metal
safe, alkaline cleaners.
SUMMARY OF THE INVENTION
The present invention provides stable, silicate-tree, soft metal safe,
alkaline
cleaners for heavy-duty surface cleaning. The cleaners of the present:
invention comprise
calcium ions, surfactants containing hydroxyl and/or carboxylic acid groups,
wherein the
total of the two functionalities in the surfactant is greater than or equal to
2, and alpha-
hydroxy carboxylic acids. Corrosion inhibition depends on the presence of
unchelated
alkaline earth metal ions and therefore, it is essential that these metal ions
be kept as such
to maintain corrosion inhibition. It has been surprisingly discovered that
alpha-hydroxy
carboxylic acids such as tartaric acid, are capable of keeping calcium ions in
an alkaline
solution.
According to an aspect of the present inventicm, there is provided a stable,
silicate-free, alkaline cleaner concentrate composition cornprising:
a) from about 0.1% to about 0.5% by weight calcium ion;
b) from about 1.0% to about 10.0% by weight surfactant containing
carboxylic acid, hydroxyl groups, and combinations thene.of, wherein the total
of the two
functionalities in the surfactant is greater than or equal to 2, and wherein
the surfactant is
selected from the group consisting of alkylpolyglucoside surl:actant,
amphoteric
surfactant, polycarboxyl surfactant, polyhydroxyl surfactant, and combinations
thereof;
c) from about 0.5°/. to about 7°/> by weight alpha-hydroxy
carboxylic acid;
and
d) from about 4% to about 25°/« by weight sodium hydroxide or potassium
hydroxide.
Other features and advantages of the present Invention will become apparent
from the following description and appended claims.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A stable, silicate-free, soft metal safe, alkaline cleaner is prowided. The
cleaners
of the present invention generally comprise a composition of calcium ions,
surfactants
CA 02193825 2002-08-16
2a
containing hydroxyl and/or carboxylic acid groups, wherein the total of the
two
functionalities in the surfactant is greater than or equal to 2, and alpha-
hydroxy
carboxylic acids. It has been surprisingly found that alpha-hydroxy carboxylic
acids are
capable of keeping calcium ions in an alkaline solution. While not intending
to be bound
by theory, it is believed that the calcium ions, surfactants and alpha-hydroxy
carboxylic
acids act together to provide a protective film on soft metal surfacf;s,
thereby achieving
stable, soft metal safe, heavy-duty alkaline cleaners.
The composition of the present invention comprises from about 0.1% to about
0.5% calcium ion, from about 1.0% to about 10.0% sunfactani containing
carboxylic acid
andlor hydroxyl groups, wherein the total of the two functionalities in the
surfactant is
greater than or equal to 2, and from about 0.5°/> to about 7°~~>
alpha-hydroxy carboxylic
acid. (All percentages herein are percentages by weight, unless - _
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otherwise indicated). A preferned composition of the present invention
comprises
from about 0.2% to about 0.4% calcium ion, from about 3% to about 7%
surfactant
and from about 2°~ to about 4% alpha-hydroxy carboxylic acid.
The calcium ions of the present invention are preferably obtained from
soluble calaum salts including but not limited to, calcium acetate and other
non
corrosive calcium salts. The surfactant of the present invention is generally
selected
from the group consisting of alkylpolyglucoside surfactants where alkyl is C6
to C18,
amphoteric surfactants containing one or two carboxylic groups and having a
carbon
chain of at least 10 carbon atoms and preferably having hydroxyl groups,
polycarboxyl surfactants, polyhydroxyl surfactants and combinations thereof.
In a
preferred composition, the surfactant is a alkylpolyglucoside surfactant,
amphoteric
surfactant andlor combinations thereof. In addition, in a preferred
composition, the
alpha-hydroxy acid is a dicarboxylic acid where tartaric acid is most
preferred.
In addition to the compounds set forth above, the composition of the present
invention may also captain from about 4°~ to about 25% and preferably
up to about
10°~ caustic soda or caustic potash and up to about 5%, preferably from
about 1 °~
to about 3°~ solvent such as alcohols, glycol ethers or hydrotropes
such as xylene
and toluene sulfonates. Additionally, up to about 5°~6 and preferably
from about 1 °~
to about 3% nonionic surfactant may be added for foam enhancing, wetting and
detergency. Examples of preferred nonionic surfactants include alcohol
alkoxylates,
alkylphenol alkoxylates, and amine oxides such as alkyl dimethylamine oxide or
bis(2-hydroxyethyl)alkylamine oxide where alkyl is a straight chain HC of 10
to 18
carbon atoms, or a combination thereof with a HLB of at least about 11. In the
case
of high retention cleaners, to enhance foam and foam retention, up to about 5%
and
preferably from about 1 % to about 3% anionic surfactant, tolerant to calcium
ions
may be added. Examples of suitable anionic surfactants include alkali metal
salts
of alkyl sulfates and alkyl ether sulfates where alkyl is at least C10 and the
number
of alkylene oxide groups is from 2 to 4.
Chemical structures of representative surfactants of the present invention are
set forth below.
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Alkylpolyglucoside Surfactants:
CHZOH
~O
doff OR
H O
OH
n
Where R is a linear alkyl chain between C6 to C18 and n is the degree of
polymerization
(1.1-3),
Arnphoteric Surfactants:
CH=Cht=Ca0'
H=CHzC00'
C"t~i~",T1HCH=CH=O!-! C~iy~,~HHCH~CH=GOOH
O CHzCI~tzOi~l p ~l-IzCli=COO.
RC-hIHCFisCfizNHI~CH=COO' RC-NHCH:CI~is~l-JCHzCFi~OpHzCHzGpp-
where n is 8 to 18.
Examples of suitable amphoteric surtactants include capryloamphopropionate,
available under the tradename Monateric'-'~" CYNA-50, disodium lauryl B-
iminOdipropivnate, available under the tradename Monateric 1188M and
cocoamphocarboxypropionate, available under the tradename Monateric CEM-38.
The cleaners of the present invention may be applied in the form of either
foam
or gel-like foam (high retention cleaners), depending on the type of
surfactants present
in the system. The cleaners described herein are to be used at
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concentration levels of about 1 % to about 8% v/v, depending on the level and
type of
soils to be removed. In a preferred embodiment, the maximum working
concentration
should not exceed 8% v/v. In addition, the amount of solids in a preferred
composition
of the present invention is at least 15%. Moreover, in a highly preferred
composition of
the present invention, the corrosion rate at 4% w/w, does not exceed 0.1
mm/yr, under
ASTM test method G-31.
It will be appreciated that the compositions of the present invention may be
used
in any appropriate cleaning situation including but not limited to industrial
and
institutional external cleaners, clean in place (CIP), bottle washing,
pasteurizers, cooling
water systems, hard surfaces cleaners, dishwashing and laundry. It will also
be
appreciated that the composition of the present invention may be varied
according to
the desired characteristics of the cleaning composition.
By "soft metal" as used herein is meant alkaline sensitive metals including
but
not limited to aluminum, zinc, tin, lead and alloys thereof, and siliceous
compositions
including but not limited to glass and porcelain. By "alkaline cleaners" as
referred to
herein is meant a cleaner having a causticity as Na20 of at least 3.0%. The
standard
for the term "stable" as used herein is meant stable, i.e. functional for its
intended
purpose, under the following conditions: room temperature for at least six
months, 50°C
(120°F) for at least one month, 5°C (40°F) for at least
one month and freeze/thaw stable
for at least three cycles.
The following examples will further illustrate the preparation and performance
of
the preferred compositions in accordance with the present invention. However,
it is to
be understood that these examples are given by way of illustration only and
are not a
limitation of the present invention. In the following examples, the term
"part" or "parts"
means parts by weight, unless otherwise noted.
EXAMPLE 1
A mixture of 73.6 parts soft water, 1.0 part calcium acetate, 3.5 parts alkyl
polyglucoside(alkyl = C6 - C,e, HLB = 13.1), 3.0 parts tartaric acid, 16.5
parts caustic
soda (50% solution), and 2.4 parts myristyl dimethylamine oxide was mixed in a
vessel
equipped with an agitator. The ingredients must be added one at a time and
mixed
thoroughly before each addition. The finished product was a transparent and
homogenous liquid.
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EXAMPLE 11
A mixture of 69.8 parts soft water, 1.0 part calcium acetate, 3.5 parts alkyl
polyglucoside(alkyl = C4 - C", HLB = 13.1 ), 3.0 parts tartaric acid, 16.5
parts caustic
soda (50% solution), 2.4 parts myristyl dimethylamine oxide, 1.8 parts sodium
lauryl
sulfate, and 2.0 parts dipropylene glycol methyl ether was mixed in a vessel
equipped with an agitator in the same manner as in EXAMPLE 1. The finished
product was a clear and homogenous liquid.
EXAMPLE III
A mixture of 61.6 parts soft water, 1.0 part calcium acetate, 3.5 parts alkyl
polyglucoside(alkyl = Cs - C", HLB = 13.1 ), 3.0 parts tartaric acid, 25.0
parts caustic
potash (45% solution), 2.4 parts myristyl dimethylamine oxide, 1.5% sodium
lauryl
sulfate, and 2.0% dipropylene glycol methyl ether was mixed in a vessel
equipped
with an agitator in the same manner as in EXAMPLE I. The finished product was
a clear and homogenous liquid.
EXAMPLE IV
A mixture of 73.2 parts soft water, 1.0 part calcium acetate, 3.0 parts
tartaric
acid, 18.0 parts caustic soda (50°~ solution), 3.0 parts
capryloamphopropionate, and
1.8 parts lauryl dimethylamineoxide was mixed in a vessel equipped with an
agitator
in the same manner as in EXAMPLE I. The finished product was a clear and
homogeneous liquid.
EXAMPLE V
A mixture of 72.8 parts soft water, 1.2 part calcium acetate, 2.5 parts alkyl
polyglucoside(alkyl = CB - C", HLB = 13.1 ), 3.0 parts tartaric acid, 16.0
parts caustic
soda (50% solution), 2.1 parts cocoamphodipropionate, and 2.4 parts lauryl
dimethylamineoxide was mixed in a vessel equipped with an agitator in the same
manner as in EXAMPLE I. The finished product was a clear and homogeneous
liquid.
EXAMPLE VI
A mixture of 72.6 parts soft water, 1.0 part calcium acetate, 3.0 parts alkyl
polyglucoside(alkyl = Ca - C,s, HLB = 13.1 ), 3.0 parts tartaric acid, 16.0
parts caustic
soda (50% solution), 2.0 parts polycarboxyl surfactant, and 2.4 parts lauryl
dimethylamineoxide was mixed in a vessel equipped with an agitator in the same
manner as in EXAMPLE I. The finished product was a clear and homogeneous
liquid.
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EXAMPLE VII
Corrosion Test Procedure: Corrosion tests have been conducted according to
ASTM method G-31. The test conditions were as follows:
Coupon dimension: 2.54 cm (1 ") a 7.62 cm (3") x 0.0635 cm (0.025")
Test solution: 4.0% wlw solution
Volume of test solutions: 800 ml
Temperature: ambient temperature
Test duration: 48 hours
Container: 896 mls (32 oz) wide-mouth French Bottle, loosely
capped
Position of test coupon: suspended in test solution
Two types of aluminum coupons were used for testing, SIC Grade (99.0% pure
aluminum), the most commonly found aluminum alloy in Europe and A 3003 H14
(97.1 % pure aluminum, bare surface), the most widely used general purpose
aluminum
alloy in North America.
Test Results: In Table I, the aluminum coupon is SIC grade (99.0% pure
aluminum). Table I shows corrosion rates of high alkaline (causticity as %
Na20)
cleaners of the present invention (the cleaners of Example I and II) and in
comparison
with that of a commercial, low alkaline cleaner.
TABLE I
Actives
in the
Conoentrat:es
Corrosion
Sample CausticityA S10= Corrosion Rate
as A Na=O inhibitors mmlyr.
~6 Ca~'IA APG'
Example 6.1 - 0.25/3.5 0.028
I
Example $.1 - 0.25/3.5 0.031
II
Commercial 3.5 ~ - ! ' ~ 11.07
1 ~
*APG = alkylpolyglucoside
In Table II, aluminum coupon is A 3003 H14 (Q-Panel). Table II shows corrosion
rates and surface appearance for cleaners of the present invention (the
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-$-
cleaners of Example II and III) in comparison with a commercial, silicated,
soft metal
safe cleaner.
TABLE II
Actives Corrosion
fn the
Concentrates
Corrosion
inhibiting
Sample system Cornosion
Causticitye of
A Si0 this Rate A
as / Na=O= PPsamnce
invention,(mmlyr)
% Cai'/
% APG'
clean,
Example 6.1 - 0.25/3.5 0.0135 shinny
II
surface
clean,
Example 6.1 - 0.25/3.5 0.0165 shinny
III
surface
Commercial 3.5 - - 11.79 brownish
I
surface
grayish
with
white film
Commercial 5.1 3.2 - 0.0545 all
II
over (silicate
film)
'APG = alkylpolyglucoside
In Table III, the aluminum coupon is A3003 H14 (Q-Panel). Table III shows
corrosion rates and surface appearance for cleaners of the present invention
(the
cleaners of Examples IV and V) in comparison to commercial silicated cleaners.
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TABLE 111
Surfactants)Corrosion
used in
Causticity
Sample as a~ conjunctionCorrosion
Na=O
with calciumRate Appearance
ion (mmlyrj
Example g,g Capryloampho-0.13 clean,
IV shinny
propionate suria~
Example 5.9 Cocoampho-0.0~ clean,
V shinny
dipropionate surface
slightly
Commercial5.1 % SiOs 0.141 grayish
II = 3.2 with
white
Tilm
The foregoing discussion discloses and describes merely exemplary
embodiments of the present invention. One skilled in the art will readily
recognize from
such discussion, and from the accompanying claims, that various changes,
modifications and variations can be made therein without departing from the
spirit and
scope of the invention as defined in the following claims.
