Note: Descriptions are shown in the official language in which they were submitted.
CA 02412240 2002-12-30
REDUCED MIaTING OVEN CI:EANER
Field of the Invention
The invention relates to aqueous alkaline cleaners that
can be used to remove stubborn soils from food preparation
units, and aqueous acidic cleaners that are used to remove
soils from hard surfaces such as floors and walls. In
particular, the invention relates to aqueous alkaline
materials that can be applied, in the form of an aerosol or
pump spray, onto stubborn soils present in food preparation
units such as gas or electrically heated ovens, microwave
ovens, toaster ovens, etc. The term oven includes ovens,
deep fryers, grills and hoods.
Background of the Invention
Acidic and alkaline cleaning compositions for hard
surfaces have been used for many years to remove stubborn
soils from a variety of surfaces found in household and
institutional locations. Such soils include inorganic soils
and sails derived from organic sources, such as fats, oils,
proteins and carbohydrates, which can form hard tenacious
deposits on a variety of surfaces including ceramic,
stainless steel, concrete, tile and metal food preparation
surfaces. Typical inorganic solids comprise insoluble
materials derived from the hardness components of service
water including substantially insoluble salts of calcium,
magnesium, iron, manganese, etc. Such inorganic salts can be
combined in some cases with organic residues which can form
large, difficult to remove soil deposits. These soils can be
unsightly, can take the form of large deposits of charred or
baked-on residue, or large areas of white insoluble soap scum
or hardness deposits. These soils can also promote or
support the growth of microorganisms that can under certain
circumstances contaminate food or other contaminatable
materials or surfaces.
A variety of cleaning compositions have been developed to
deal with the tenacious organic and organic/inorganic matrix
soils common in a variety of surfaces. One particularly
useful form of cleaner is an aqueous alkaline cleaner
CA 02412240 2002-12-30
2 -
commonly delivered from a pressurized aerosol or pump spray
device. These types of cleaners have great utility for a
variety of surfaces because the material can be delivered by
spray to vertical, overhead or inclined surfaces or to
surfaces having a complex curved or convoluted surface while
achieving substantially complete coverage of the surface with
the spray-on liquid cleaner. Acid spray-on cleaners are also
known for removing basic inorganic soils and are becoming
more common.
One substantial problem that arises with such spray-on
materials relates to an airborne mist or finely divided
aerosol generated during the spraying process. The aqueous
liquid is converted by the action of propellant or pump
action into a spray that is accompanied by a finely divided
aerosol or mist. The spray portion contacts and remains on
the target surface, while a substantial proportion of the
aerosol can remain suspended in the atmosphere.
Such aqueous compositions having a strong acid or strong
base cleaning component in the form of a finely divided
aerosol or mist can cause respiratory distress in the user.
Upon breathing the finely divided aerosol or mist, a very
strong and irrepressible choking response is seen in most
individuals that come in contact with irritating proportions
of the aerosol produced by typical spray-on cleaners. The
choking response is inconvenient, reduces cleaning efficiency
in a variety of applications and in sensitive individuals can
cause asthma attacks, respiratory damage, or other discomfort
or injury.
To alleviate, to some degree, the choking response, some
products have been formulated with reduced quantities of the
strongly alkaline or strongly acid cleaning components to
reduce the choking response. Strong caustic has been
replaced by reduced alkalinity bases such as bicarbonate or
by solvent materials. The reduction in concentration or
substitution of these materials can often reduce the cleaning
activity and effectiveness of the material when used.
Crotty et al., United States Patent No. 3,644,210, teach
CA 02412240 2002-12-30
3
an alkaline cleaning material useful for removing burnt-on,
baked-on food and grease from cooking surfaces comprising
substantial proportions of alkali metal hydroxide in an
aqueous cleaning base. Eisen, United States Patent No.
3,7?9,933, teaches an aqueous alkali metal cleaning
composition using clay and organic thickening materials.
Mukai et al., United States Patent No. 3,813,343, teach oven
cleaning compositions containing an amine or ammonia base
combined with dimethyl sulfoxide solvent and other
compositions. Wise et al., United States Patent No.
3,829,387, teach caustic cleaning compositions containing
substantial proportions of sodium hydroxide, clay thickeners,
and solvents in an aqueous base. Dillarstone et al., United
States Patent No. 4,214,915, and Canadian Patent No.
1,523,491, teach oven cleaning compositions using as a base
sodium carbonate and sodium bicarbonate in an aqueous
cleaning material. Culshaw, United States Patent No.
4,676,920, teaches a thickened viscous scouring material
using surfactants, abrasives and solvents for soil removal.
De Buzzaccarini, United States Patent No. 4,767,563, teach
liquid scouring cleaning compositions using solvents,
abrasives and surfactants for soil removal from hard
surfaces. Cockrell, Jr., United States Patent No. 4,877,691
(International Application No. PCT/US91/05092) teaches a
composition used to pretreat an oven to promote the
subsequent removal of hardened baked-on soils that form on
the pretreatment material. Dimond et al., Canadian Patent
No. 1,047,903, teach oven cleaning compositions having
reduced proportions of sodium hydroxide which are thickened
using a bentonite in a substantially aqueous base.
Silvester, Canadian Patent No. 1,211,674, teaches an improved
oven cleaner using sodium bicarbonate as an alkali, glycerol
as a solvent, a clay thickener in an aqueous formulation for
oven cleaning. Flannery, United Kingdom Patent No.
2,019,876, teaches an aerosol comprising sodium bicarbonate
as an oven cleaner.
The prior art taken as a whole shows that skilled
CA 02412240 2002-12-30
4 -
artisans in experimenting with improving acid and alkaline
hard surface cleaners, in particular alkaline oven cleaners,
have attempted to reduce concentrations of sodium hydroxide
to reduce the choking response. Ammonia or an organic base
has been used to replace sodium hydroxide in reduced alkaline
cleaners. Other inorganic materials, such as sodium
carbonate or sodium bicarbonate have also been used to
replace sodium hydroxide. A variety of glycol, ether or
dimethyl sulfoxide solvent material have been used to enhance
the detergent properties of the reduced alkaline materials
using organic surfactants.
The prior art taken as a whole has attempted to replace
sodium hydroxide to reduce choking response but does not
recognize that the choking properties of these cleaners is
related to the particle size of the aerosol. For this
reason, no attempt has been made in the prior art to
formulate to adjust the particle size of the aerosol to
reduce respiratory distress or choking reflex.
Brief Description of the Invention
We have found that either aqueous strong acid or aqueous
strong base cleaning compositions that are used in a spray-on
format can be made non-choking by producing a formulation
that when sprayed results in the creation of an airborne
aerosol or mist having a mean particle size greater than
about 170 pm, preferably greater than about 200 yam. The
materials of the invention produce little or no small
particle aerosol. The concentration of small particle
airborne aerosol from a mean particle size greater than 200
~m is not sufficient to cause respiration difficulty.
Aerosol sprays, either propellant driven or pump driven,
create a spray pattern of the aqueous liquid that contacts
the target surface. Some spray nozzles produce a greater
proportion of small particle airborne aerosol than others.
The major proportion of the liquid resides in large sprayed
deposits which contact and remain on a target surface. A
small proportion becomes an airborne aerosol or mist. The
CA 02412240 2002-12-30
_
mist or aerosol particle size, discussed above, relates to
the mist created during the spray action and is not directed
to the material sprayed which remains in contact with the
target surface. Any spray pattern created during spraying
5 operations will contain an array of large and small spray
particles which do not become airborne and are transported
directly to and remain in place on the treated surface. We
are not concerned with the proportion of the spray that
remain on the target surface. We are primarily concerned
only with the portions of the sprayed material that take the
form of a small particle size aerosol or mist that can remain
suspended in or transported by the atmosphere for a
substantial period of time at least 5 seconds, typically 30
seconds to 10 minutes after spraying.
The improved compositions of the invention comprise
aqueous materials comprising a strong acid or a strong base,
an organic surfactant, an organic polymeric thickener, and a
variety of other useful optional ingredients. The cleaners
of the invention can be packaged in pressurized aerosol spray
units using commonly available pressure containers, aerosol
valves and aerosol propellants. The cleaners of the
invention can be used in a pump spray format using a pump
spray head and a suitable container. The materials are
typically applied to hard surfaces containing difficult
inorganic, organic, or matrix-blended soils. Such soils
include baked-on or carbonized food residues. Other surfaces
can contain soils derived from substantially insoluble
hardness components of service water. The enhanced cleaning
compositions of the invention rapidly remove such soils
because the cleaners have a unique combination of cleaning
ingredients combined with thickeners that can rapidly remove
the soils but resist formation of an amount of mist or
aerosol during application that can cause respiratory
distress. For the purpose of this application, the terms
"aerosol" and "mist" refer to airborne dispersions of small
particles comprising the cleaning composition that can remain
suspended or dispersed in the atmosphere surrounding a
CA 02412240 2002-12-30
6
cleaning site for at least 5 seconds, more commonly 30
seconds to 10 minutes. We have found in our research that
the respiratory distress or involuntary choking response
caused by the inhalation of such mist, depending on the
irritation capacity of the cleaning components, is inversely
proportional to the particle size of the aerosol or mist. We
have found that strongly irritating, strongly acidic or basic
materials are increasingly irritating as the mean particle
size drops below about 200 um and mildly irritating materials
tend to become irritating as the mean particle size drops
below about 170 Nm. However, any sprayable composition can
be rendered at worse, mildly irritating if the mean particle
size of its aerosol or mist created upon spraying is
maintained at greater than 200 um, preferably greater than
210 Nm.
Detailed Description of the Invention
The sprayable aqueous cleaning compositions of the
invention typically comprise either a strong acid or strong
base in combination with an organic surfactant, and an
effective organic thickener material in an aqueous
composition. The compositions of the invention can contain a
variety of other optional ingredients recited below.
Strong Base
The liquid aqueous cleaner compositions of the invention
can contain a strong base material or a source of alkalinity
which can be an organic source or an inorganic source of
alkalinity. For the purposes of this invention, a source of
alkalinity also known as a basic material is a composition
that can be added to an aqueous system and result in a pH
greater than about 7. Organic sources of alkalinity are
often strong nitrogen bases including, for example, ammonia,
monoethanol amine,, monopropanol amine, diethanol amine,
dipropanol amine, triethanol amine, tripropanol amine, etc.
One value of using the monoalkanol amine compounds relates to
the solvent nature of the liquid amines. The use of some
substantial proportion of a monoethanol amine, monopropanol
CA 02412240 2002-12-30
7
amine, etc. can provide substantial alkalinity but can
also provide substantial solvent power in combination
with the other materials in the invention. The source
of alkalinity can also comprise an inorganic alkali.
The inorganic alkali content of the spray-on cleaners of
the invention is preferably derived from sodium or
potassium hydroxide which can be used in both liquid
(about 10-60 wt% aqueous solution) or in solid (powder,
flake or pellet) form. The preferred form of the alkali
metal base is commercially available sodium hydroxide
which can be-obtained in aqueous solution at
concentrations of about 50 wto and in a variety of solid
forms of varying particle size and shapes. Other
inorganic alkalinity sources are soluble silicates such
as sodium metasilicate or soluble phosphate.
The strong base may comprise about 1 to about 20
wto of the composition, preferably about 1 to about 15
wto of the composition. The strong base may comprise an
organic base as described above, an inorganic base such
as an alkali metal hydroxide as described above, or a
mixture thereof. If a mixture is used the weight ratio
of alkali metal hydroxide to organic base may be, for
example, about 1 to about 10, preferably about 1 to 5
parts alkali metal hydroxide per part of organic base.
Strong Acid
The aqueous cleaning compositions of the invention
can contain as a primary cleaning agent about 1 to 20
wt% of an acid composition that can typically be a
strong acid or a strong acid combined with a weak acid.
For the purposes of this invention, an acid material is
a composition that can be added to an aqueous system and
result in a pH less than about 7. Strong acids that can
be used in the aqueous cleaners of the invention include
acids which substantially dissociate in an aqueous
solution (strong acid) such as hydrochloric acid,
sulfuric acid, trichloroacetic acid, trifluoroacetic
acid, nitric acid and others. "Weak" organic and
CA 02412240 2002-12-30
8
inorganic acids can be used in the invention as a
component of the acid cleaner. Weak acids are acids in
which the first dissociation step of a proton from the
acid canon moiety does not proceed essentially to
completion when the acid is dissolved in water at
ambient temperatures at a concentration within the range
useful to form the present cleaning composition. Such
inorganic acids are also referred to as weak
electrolytes as the term is used in the text book
Quantitative Inorganic Analysis, I. M. Koltoff et al.,
published by McMillan Co., Third Edition, 1952, pp. 34-
37. Most common commercially available weak organic and
inorganic acids can be used in the invention. Examples
of weak organic and inorganic acids include phosphoric
acid, sulfamic acid, acetic acid, hydroxy acetic acid,
citric acid, benzoic acid, tartaric acid, malefic acid,
malic acid, fumaric acid and the like. We have found in
certain applications that mixtures of strong acid with
weak acid or mixtures of a weak organic acid and a weak
inorganic acid with a strong acid can result in
surprisingly increased cleaning efficiency. Such acid
cleaners tend to be most effective to clean basic
organic and inorganic soils. The soil most commonly
cleaned using acid cleaners involves the soils resulting
from the precipitation of hardness components of service
water with cleaning compositions or food soils that can
precipitate in the presence of calcium, magnesium, iron,
manganese or other hardness components. Such soils
include dairy residue, soap scum, saponified fatty acids
or other marginally soluble anionic organic species that
can form a soil precipitate or matrix when combined and
contacted with divalent hardness components of service
water.
Surfactant
The aqueous cleaning compositions of the invention
can contain an organic surfactant composition. ?anionic,
nonionic, cationic or amphoteric surfactants car. be
CA 02412240 2002-12-30
9
used. Surfactants can comprise about 0.01 to about 5
wt% of the composition if the composition is alkaline
and about 1 to about 20 wto of the composition if the
composition is acidic. Anionic materials that can be
used in the aqueous compositicns of the invention are
surfactants containing a large lipophilic moiety and a
strong anionic group. Such anionic surfactants contain
typically anionic groups selected from the group
consisting of sulfonic, sulfuric or phosphoric,
phosphonic or carboxylic acid groups which when
neutralized will yield sulfonate, sulfate, phosphonate,
or carboxylate with a cation thereof preferably being
selected from the group consisting of an alkali metal,
ammonium, alkanol amine such as sodium, ammonium or
triethanol amine. Examples of operative anionic
sulfonate or sulfate surfactants include alkylbenzene
sulfonates, sodium xylene sulfonates, sodium
dodecylbenzene sulfonates, sodium linear tridecylbenzene
sulfonates, potassium octyldecylbenzene sulfonates,
sodium lauryl sulfate, sodium palmityl sulfate, sodium
cocoalkyl sulfate, sodium olefin sulfonate.
Nonionic surfactants carry no discrete charge when
dissolved in aqueous media. Hydrophilicity of the
nonionic is provided by hydrogen bonding with water
molecules. Such nonionic surfactants typically comprise
molecules containing large segments of a polyoxyethylene
group in conjunction with a hydrophobic moiety or a
compound comprising a polyoxypropylene and
polyoxyethylene segment. Polyoxyethylene surfactants
are commonly manufactured through base catalyzed
ethoxylation of aliphatic alcohols, alkyl phenols and
fatty acids. Polyoxyethylene block copolymers typically
comprise molecules having large segments of ethylene
oxide coupled with large segments of propylene oxide.
These nonionic surfactants are well known for use in
this art area.
The lipophilic moieties and cationic groups
CA 02412240 2002-12-30
_
comprising amino or quaternary nitrogen groups can
provide surfactant properties to surfactant molecules.
As the name implies to cationic surfactants, the
hydrophilic moiety of the nitrogen bears a positive
5 charge when dissolved in aqueous media. The soluble
surfactant molecule can have' its solubility or other
surfactant properties enhanced using low molecular
weight alkyl groups or hydroxy alkyl groups. Cationic
surfactants can be used in the acidic or basic
10 compositions of the invention. One preferred cationic
surfactant material is an oxygen containing amine
compound such as an amine oxide. The preferred class of
cationic surfactants include tertiary amine oxide
surfactants. Tertiary amine oxide surfactants typically
comprise three alkyl groups attached to an amine oxide
(N~O). Commonly the alkyl groups comprise two lower (C1_
4) alkyl groups combined with one higher C6_z4 alkyl
groups, or can comprise two higher alkyl groups combined
with one lower alkyl group. Further, the lower alkyl
groups can comprise alkyl groups substituted with
hydrophilic moiety such as hydroxyl, amine groups,
carboxylic groups, etc. Preferred amine oxide materials
for the invention comprise dimethylcetylamine oxide,
dimethyllaurylamine oxide, dimethylmyristylamine oxide,
dimethylstearylamine oxide, dimethylcocoamine oxide,
dimethyldecylamine oxide, and mixtures thereof.
Amphoteric surfactants can be useful in the
invention. Amphoteric surfactants contain both an
acidic and a basic hydrophilic moiety in the structure.
These ionic functions may be any of the ionic or
cationic groups that have just been described previously
in the sections relating to anionic or cationic
surfactants. Briefly, anionic groups include
carboxylate, sulfate, sulfonate, phosphonate, etc. while
the cationic groups typically comprise compounds having
amine nitrogens. Many amphoteric surfactants also
contain ether oxides or hydroxyl groups that strengthen
CA 02412240 2002-12-30
11
their hydrophilic tendency. Preferred amphoteric
surfactants of this invention comprise surfactants that
have a cationic amino group combined with an anionic
carboxylate or sulfonate group. Examples of useful
amphoteric surfactants include the sulfobetaines, N-
coco-3,3-aminopropionic acid and its sodium salt, n-
tallow-3-amino-dipropionate disodium salt, 1,1-
bis(carboxymethyl)-2-undecyl-2-imidazolinium hydroxide
disodium salt, cocoaminobut.yric acid, cocoaminopropionic
acid, cocoamidocarboxy glycinate, cocobetaine.
Preferred amphoteric surfactants for use in the
compositions of the invention include
cocoamidopropylbetaine and cocoaminoethylbetaine.
AcLueous Compatible Solvents
The cleaner materials of the invention can contain
a compatible solvent. Suitable solvents are soluble in
the aqueous cleaning composition of the invention at use
proportions. Preferred soluble solvents include lower
alkanols, lower alkyl ethers, and lower alkyl glycol
ethers. These materials are colorless liquids with mild
pleasant odors, are excellent solvents and coupling
agents and are typically miscible with aqueous cleaning
compositions of the invention. Examples of such useful
solvents include methanol, ethanol, propanol,
isopropanol and butanol, isobutanol, ethylene glycol,
diethylene glycol, triethyl_ene glycol, propylene glycol,
dipropylene glycol, mixed ethylene-propylene glycol
ethers. The glycol ethers include lower alkyl (C1_8
alkyl) ethers including propylene glycol methyl ether,
propylene glycol ethyl ether, propylene glycol propyl
ether, dipropylene glycol methyl ether, dipropylene
glycol ethyl ether, tripropylene glycol methyl ether,
ethylene glycol methyl ether, ethylene glycol ethyl
ether, ethylene glycol butyl ether, diethylene glycol
methyl ether, diethylene glycol butyl ether, ethylene
glycol dimethyl ether, ethylene glycol monobutyl ether,
and others. The solvent capacity of the cleaners can be
CA 02412240 2002-12-30
12
augmented by using monoalkanol amines.
Thickeners or Viscosit~r Modifiers
The compositions of the invention require the
presence of a material that will provide a composition
that is thixotropic, in other words the material when
left undisturbed (in a shear mode), retains a high
viscosity. However, when sheared, the viscosity of the
material is substantially but reversibly reduced. After
the shear action is removed, the viscosity returns.
These properties permit the application of the material
through a spray head. When sprayed from an aerosol
container using a propellant, the material undergoes
shear as it is drawn up a feed tube into a aerosol spray
~ head under the influence of the pressure of a propellant
or is sheared by the action of a pump in a pump action
sprayer. In either case, the viscosity must drop to a
point such that substantial quantities of the material
can be applied using the spray devices used to apply the
material to a soiled surface.. However, once the
material comes to rest on a soiled surface, the
materials should regain high viscosity to ensure that
the material remains in place on the soil. Preferably,
the material can be applied to a surface resulting in a
substantial coating of the material that provides the
cleaning components in sufficient concentration to
result in lifting and removal of the hardened or baked-
on soil. While in contact with the soil on vertical or
inclined surfaces, the thickeners in conjunction with
the other components of the cleaner prevent dripping,
slumping or other movement of the material under the
effects of gravity. The material should be formulated
such that the viscosity of the material is adequate to
maintain contact between substantial quantities of the
film of the material with the soil for at least a
minute, preferably five minutes or more.
A variety of well known organic thickener materials
are known in the art. Preferred thickeners for use in
this invention are natural polymers or gums derived from
CA 02412240 2002-12-30
:L 3
plant or animal sources. Such materials are often large
polysaccharide molecules having substantial thickening
capacity.
A substantially soluble organic thickener, such as
an organic polymer thickener, is used to provide
thixotropy to the compositions of the invention. This
organic thickener typically comprises about 0.01 to
about 5 wto, preferably about 0.01 to about 2 wt% of the
composition for basic compositions and about 0.01 to
about 10 wt% of the composition for acidic compositions.
The preferred thickeners have some substantial
proportion of water solubility to promote easy
removability. Examples of soluble organic polymer
thickeners for the aqueous compositions of the invention
comprise carboxylated vinyl polymers such as polyacrylic
acids and sodium salts thereof, boric acid,
diethanolamide, coco-diethanolamide, coco-
monoethanolamide, stearic-diethanolamide, ethoxylated
cellulose, hydroxyethyl styrylamide, oleic-
diethanolamide, stearic-monoethanolamide, cetyl alcohol,
steroyl alcohol, polyacrylamide thickeners, ethanol
glycol disterate, xanthan compositions, sodium alginate
and algin products, hydroxypropyl cellulose,
hydroxyethyl cellulose, and other similar aqueous
thickeners that have some substantial proportion of
water solubility. Preferred thickeners for use in the
alkaline composition of the invention are xanthan
thickeners sold by the Kelco Division of Merck under the
tradenames KELTROL, KELZAN AR, KELZAN D35, KELZAN S,
KELZAN XZ, and others. Such xanthan polymers are
preferred due to their high water solubility, and great
thickening power. Compositions of the invention can be
made with small concentrations of xanthan thickeners yet
remain substantially water soluble or dispersible using
aqueous cleaners or mild aqueous detergent compositions.
The preferred thickeners for acid compositions of
the invention comprise polyvinyl alcohol thickeners
CA 02412240 2002-12-30
14
having a molecular weight greater than about 20,000.
The polyvinyl alcohol preferably has a degree of
hydrolysis (mole-o- of acetate removal from the -OH
function) of greater than about 870, and is most
preferably fully hydrolyzed (greater than 98.5 molo
acetate removal from the -OH function). Preferred
thickeners for inorganic alkaline cleaners include
xanthan gum derivatives. Xanthan is an extracellular
polysaccharide of xanthomonas campestras. Xanthan is
made by fermentation based on corn sugar or other corn
sweetener by-products. Xanthan comprises a poly beta-
(1~4)-D-Glucopyranosyl backbone chain, similar to that
found in cellulose. Aqueous dispersions of xanthan gum
and its derivatives exhibit novel and remarkable
rheological properties. Low concentrations of the gum
have relatively high viscosity which permit it
economical use and application. Xanthan gum solutions
exhibit high pseudoplasticity, i.e. over a wide range of
concentrations, rapid shear thinning occurs that is
generally understood to be instantaneously reversible.
Non-sheared materials have viscosity that appears to be
independent of the pH and independent of temperature
over wide ranges. Preferred xanthan materials include
crosslinked xanthan materials. Xanthan polymers can be
crosslinked with a variety of known covalent reacting
crosslinking agents reactive with the hydroxyl
functionality of large polysaccharide molecules and can
also be crosslinked using divalent, trivalent or
polyvalent metal ions. Such crosslinked xanthan gels
are disclosed in United States Patent No. 4,782,901.
Suitable crosslinking agents for xanthan materials
include metal canons such as A1+3, Fe+3, Sb+3, Zr+4 and
other transition metals, etc. Known organic
crosslinking agents can also be used. The preferred
crosslinked xanthan agent of the invention is KELZAN AR,
a product of Kelco, a divi:~ion of Merck Incorporated.
CA 02412240 2002-12-30
KELZAN AR is a crosslinked xanthan that provides a
thixotropic cleaner that can produce large particle size
mist or aerosol when sprayed.
Sequestrant
5 The thickened materials of the invention can
contain an organic or inorganic sequestrant or mixtures
of sequestrants. Organic sequestrants such as citric
acid, the alkali metal salts of nitrilotriacetic acid
(NTA), EDTA, alkali metal gluconates, polyelectrolytes
10 such as a polyacrylic acid, and the like can be used
herein. The most preferred sequestrants are organic
sequestrants such as sodium gluconate due to the
compatibility of the sequestrant with the formulation
base.
15 The present thickened cleaning materials will also
comprise an effective amount of a water-soluble organic
phosphonic acid which has sequestering properties.
Preferred phosphonic acids include low molecular weight
compounds containing at least two anion-forming groups,
at least one of which is a phosphonic acid group. Such
useful phosphonic acids include mono-, di-, tri- and
tetra-phosphonic acids which can also contain groups
capable of forming anions under alkaline conditions such
as carboxy, hydroxy, thio and the like. Among these are
phosphonic acids having the formulae:
R1N [ CHzPO3H2] 2 or RzC ( P03H2 ) 20H,
wherein Rl may be - [ (lower) alkylene] N [CH2PO3H2] 2 or a
third CH2P03H2 moiety; and wherein R2 is selected from the
group consisting of C1C6 alkyl.
The phosphonic acid may also comprise a low
molecular weight phosphonopolycarboxylic acid such as
one having about 2-4 carboxylic acid moieties and about
1-3 phosphonic acid groups. Such acids include 1-
phosphono-1- methylsuccinc acid, phosphonosuccinic acid
and 2-phosphonobutane-1,2,4-tricarboxylic acid.
Other organic phosphonic acids include 1-
hydroxyethylidene-1,1-diphosphonic acid (CH3C(P03H2)zOH),
CA 02412240 2002-12-30
1 Ei
available from Monsanto Industrial Chemicals Co., St.
0
Louis, MO as bequest 2010, s, 58-62% aqueous solution;
amino [tri (methylenephosphoni.c acid) I (N [CHzP03H2] a) ,
0
available from Monsanto as bequest 2000, a 50o aqueous
solution; ethylenediamine [tetra(methylene-phosphonic
0
acid)] available from Monsanto as bequest 2041, a 900
solid acid product; and 2-phosphonobutane-1,2,4-
tricarboxylic acid available from Mobay Chemical
Corporation, Inorganic Chemicals Division, Pittsburgh,
PA as Bayhibit AM, a 45-50% aqueous solution. It will
be appreciated that, the above-mentioned phosphonic
acids can also be used in the form of water-soluble acid
salts, particularly the alkali metal salts, such as
sodium or potassium; the ammonium salts or the alkylol
amine salts where the alkylol has 2 to 3 carbon atoms,
such as mono-, di-, or tri- ethanolamine salts. If
desired, mixtures of the individual phosphonic acids or
their acid salts can also be used. Further useful
phosphonic acids are disclosed in U.S. Patent No.
4,051,058, the disclosure of which is incorporated by
reference herein.
The present compositions can also incorporate a
water soluble acrylic polymer which can act to condition
the wash solutions under end-use conditions. Such
polymers include polyacrylic acid, polymethacrylic acid,
acrylic acid-methacrylic acid copolymers, hydrolyzed
polyacrylamide, hydrolyzed polymethacrylamide,
hydrolyzed acrylamidemethacrylamide copolymers,
hydrolyzed polyacrylonitrile, hydrolyzed
polymethacrylonitrile, hydrolyzed
acrylonitrilemethacrylonitrile copolymers, or mixtures
thereof. Water-soluble salts or partial salts of these
polymers such as the respective alkali metal (e. g.
sodium or potassium) or ammonium salts can also be used.
The weight average molecular weight of the polymers is
from about 500 to about 15,000 and is preferably within
the range of from 750 to 10,000. Preferred polymers
CA 02412240 2002-12-30
17
include polyacrylic acid, the partial sodium salt of
polyacrylic acid or sodium polyacrylate having weight
average molecular weights within the range of 1,000 to
6,000. These polymers are commercially available, and
methods for their preparation are well-known in the art.
For example, commercially-available water-
conditioning polyacrylate solutions useful in the
present cleaning solutions include the sodium
polyacrylate solution, Colloid 207 (Colloids, Inc.,
0
Newark, NJ); the polyacrylic acid solution, Aquatreat
AR-602-A (Alco Chemical Corp., Chattanooga, TN); the
polyacrylic acid solutions (50-650 solids) and the
sodium polyacrylate powders (m.w. 2,100 and 6,000) and
0
solutions (45% solids) available as the Goodrite K-700
series from B.F. Goodrich Co.; and the sodium- or
partial sodium salts of polyacrylic acid solutions (m. w_
0
1000-4500) available as the Acrysol series from Rohm
and Haas_
The present invention can also incorporate
sequestrants to include materials such as, complex
phosphate sequestrants, including sodium
tripolyphosphate, sodium hexametaphosphate, and the
like, as well as mixtures thereof. Phosphates, the
sodium condensed phosphate hardness sequestering agent
component functions as a water softener, a cleaner, and
a detergent builder. Alkali metal (M) linear and cyclic
condensed phosphates commonly have a MzO:Pz05 mole ratio
of about 1:1 to 2:1 and greater. Typical polyphosphates
of this kind are the preferred sodium tripolyphosphate,
sodium hexametaphosphate, sodium metaphosphate as well
as corresponding potassium s<~lts of these phosphates and
mixtures thereof. The particle size of the phosphate is
not critical, and any finely divided or granular
commercially available product can be employed.
Sodium tripolyphosphate is a preferred inorganic
hardness sequestering agent for reasons of its ease of
availability, low cost, and high cleaning power. Sodium
CA 02412240 2002-12-30
18
tripolyphosphate acts to sequester calcium and/or
magnesium cations, providing water softening properties.
It contributes to the removal of soil from hard surfaces
and keeps soil in suspension. It has little corrosive
action on common surface materials and is low in cost
compared to other water conditioners. Sodium
tripolyphosphate has relatively low solubility in water
(about 14 wt%) and its concentration must be increased
using means other than solubility. Typical examples of
such phosphates being alkaline condensed phosphates
(i.e. polyphosphates) such as sodium or potassium
pyrophosphate, sodium or potassium tripolyphosphate,
sodium or potassium hexametaphosphate, etc.
Metal Protector
The compositions of the invention can contain a
material that can protect ferrous metal from corrosion.
Such metal protectors include for example sodium
gluconate and sodium glucoheptonate. The corrosion
inhibitor can comprise about 0_01 to about 5 wt% of the
composition.
In addition to the recited components of the
compositions of the invention there may also be present
adjuvant materials for hard surface cleaning. Such
adjuvant materials may include foam enhancing agents,
foam suppressing agents (when desired), preservatives,
antioxidants, pH adjusting agents, perfumes, colorants,
or pacifying or pearlescent agents, builder salts,
cosolvents and other useful well understood material
adjuvants.
The materials of the invention are commonly applied
to soiled surfaces using a pressurized aerosol or
aerosol pump spray. In pressurized aerosol application,
the compositions of the invention are combined with a
aerosol propellant and packaged in a metal high pressure
container. Typical propellants include lower alkanes
such as propane, butane, nitrous oxide, carbon dioxide,
and a variety of fluorocarbons. Pressurized aerosol
CA 02412240 2002-12-30
I9
containers typically include a spray head, valve and dip
tube that reaches to the opposite end of the contai::er
to ensure that the entire contents of the container is
dispensed through the action of the propellant. when
the valve is opened (depressed), the propellant pressure
forces liquid into the dip tube and through the aerosol
spray head. At the spray head exit, a spray pattern is
created by the geometry of the aerosol valve which
directs the material onto the soiled surface. Aerosol
containers, dip tubes, propellants and spray valves are
well understood commercial technology. Pump spray
devices commonly comprise a container spray head valve
pump and dip tube. Actuating the pump causes a piston
to travel in a cylinder filled with compositions of the
invention. The piston motion forces the composition
through an aerosol valve cau:~ing the spray to adhere to
a soiled surface. Once the piston raaches its full
travel path, the piston is rc=turned by a spring action
to its original position causing the cylinder to fill
with additional quantities of the spray material through
a valve opening. As the piston is again pressed through
the cylinder the valve closes preventing the exit of any
of the solution from the cylinder. The pump spray can
deliver substantial quantities of the material onto the
soiled surface.
The materials of the invention can be made by
combining the ingredients in an aqueous diluent using
commonly available containers and blending apparatus. A
preferred method for performing the composition of the
invention includes introducing into a stirred production
vessel, a quantity of the deionized water followed by
the organic thickener material used to provide
thixotropic properties to the compositions of the
invention. After the thickener is fully solubilized,
the other ingredients of the invention can be added in
any order.
The following examples, experiments and data
CA 02412240 2002-12-30
provide a basis for understanding the nature of the
invention and include a best mode.
Experimental
A. Cleaning Capacity
5 The following preparation was tested for cleaning
using a hood and grill soil test or a Crisco test.
Hood and Grill Soil Test
This test is meant to simulate a cleaner's ability
to remove polymerized oils from institutional hoods,
10 ovens, and grills.
A 2.5 gram sample of Mazola brand corn oil is
spread evenly onto a 35.5 cm by 35.5 cm (14 inch by 14
inch) sheet of stainless steel. The sheet is heated at
200°C for three hours. The heating procedure causes the
15 oil to polymerize to a tenacious varnish-like yellow
film.
A composition's cleaning ability is measured
relative to a standard formulation. One gram samples of
the test formulation and the standard are placed onto
20 the polymerized film using a dropper. This is done at
room temperature. The time required for the
compositions to cause the film to loosen is recorded.
By loosen is meant that the film wrinkles and lifts from
the stainless steel surface to the point where it is
removed by running tap water. over the sheet.
Crisco Test
This test is meant to simulate a cleaner's ability
to remove freshly deposited, non-polymerized oils and
greases from hard surfaces found in institutional
kitchens. A one gram sample of Crisco brand all-
vegetable shortening is sere ad evenly onto a 25.5 cm by
25.5 cm (10 inch by 10 inch) glass door of a laboratory
hood.
A composition's cleaning ability is measured
relative to a standard formulation. A test formulation
is sprayed onto the soil through an Affa Sprayer No.
5910BA. Five sprays are used in a "domino" pattern.
CA 02412240 2002-12-30
21
After the fifth spray, the composition is allowed to
remain in contact with the soil for one minute before
wiping. A Scott brand laboratory Soft Cote Wipe is used
to wipe off the soil. Following the wipe, one
additional spray is applied t:o the surface and a new
wipe is used to, again, wipe the surface. The efficacy
of the cleaner is measured during the one minute after
the initial spray and after each wiping. A satisfactory
test formulation emulsifies and lifts the soil during
the one minute, and leaves a grease free surface after
wiping. In particular, the surface should be clean and
streak free after the second wipe.
Example 1
Into an appropriately sized metallic container
equipped with a stirring apparatus is charged 3071.4
grams of deionized water. Slowly into the agitated
water is placed 7.57 grams of KELZAN AR, a crosslinked
xanthan gum manufactured by Kelco, a division of Merck
Co. After the KELZAN solution is uniform, 340.65 grams
of a 50 wt% active aqueous solution of sodium hydroxide
is slowly added to the thickened water. The sodium
hydroxide is followed by 75.7 grams of cocoamidopropyl-
betaine (30o active) and 18.92 grams of sodium lauryl
ether sulfate (60 wt% active aqueous solution). The
solution was stirred until uniform and 60.56 grams of
sodium gluconate followed by 18.9 grams of a Clo-lz
alkyldimethyl amine oxide (300) was introduced into the
solution followed by 5.67 grams of d-limonene fragrance
and 185.46 grams of butyl cellosolve. Lastly, 0.12 gram
of a mixed dye was added to the solution.
The composition of Example 1 was tested for its
ability to clean common greasy soil. A 25.5 cm x 25.5
cm (10 inch x 10 inch) area of glass was coated with 1
gram of Crisco brand shortening. Formula I was diluted
to 50 wto and was sprayed on such 10 inch x l0 inch
sample of grease. The 50 wt% diluted concentration cut
CA 02412240 2002-12-30
22
the grease cleanly. The material, in a hood and grill
soil test, when applied to hood and grill soil samples,
removed 100% of the soil in 3 minutes, 25 seconds. Both
neat and 50 wt% active dilutions of the material
S produced non-choking mists when sprayed_ In performing
the spray tests of the materials of the invention, a
spray head known as Affa Sprayer No. 5910BA, was
selected. The selection of the spray head was made
because the spray generated by this spray head was known
to be most irritating when used with highly alkaline or
highly acidic cleaning compositions. Any reduction in
the production of irritating mists or aerosols obtained
with this spray head would be a significant proof of the
ability of the compositions to reduce production of
irritating mists or aerosols in a worse case scenario.
Examples 2A-C
Inctredient Weight Percent
2A 2B 2C
Water 83.05 83.65 81.85
Xanthan (KELZAN AR) 0.2 0.0 0.2
Sodium Hydroxide
(50 wt% active aqueous) 9.0 9.0 9.0
Coco Amido Propyl
Betaine (30% active) 2.0 2.0 2.0
Sodium Gluconate 1.0 1.0 1.0
Lauryl Ether Sulfate 0.5 - -
(60o active)
Clo-lz Dimethylamine Oxide 0.5 0.5 0.5
(30% active)
Monoethanolamine 3.0 3.0 -
d-limonene (fragrance) 0.15 0.15 0.15
Butyl Cellosolve - - 5.0
Dye 0.005 - -
CA 02412240 2002-12-30
23 _
A test of the Example 2B at a 50 wto active
dilution in water resulted in a 1000 cleaning of the
Crisco test sample.
Testing on hood and grill soil gave the following
results.
Time Exposure o Removal Time of
Lift
Example 2B 2:55 97 2:20
Example 2C 2:25 100 2:04
The data shown in conjunction with Examples 1 and 2
demonstrate the cleaning capacity of the compositions of
the invention. Both the Crisco tests and the hood and
grill soil tests show that soils commonly encountered in
the food preparation environment can be rapidly and
substantially completely removed using the cleaning
compositions of the invention. The formulations of the
invention that are reduced misting do not suffer any
loss of cleaning capacity for improvement in respiratory
compatibility.
B. Particle Size Analysis and Surface Tension Results
- Caustic Formulas
Particle size analysis test formulations were
dispensed through an aerosol misting sprayer (Affa
Sprayer No. 5910BA) into a Malvern Instruments Particle
Sizer model INDP.
Surface tensions were evaluated on a Kruss D-12
autotensiometer using a Du Nouy ring at 25°C.
The irritating effect of the test formulations were
evaluated by spraying the test formulations into a
laboratory sink with the same aerosol misting sprayer as
used for the particle size analysis and having the
person doing the spraying inhale the air over the sink
and record the level of irritation on a 0-5 scale with 0
being no irritation and 5 being very irritating.
CA 02412240 2002-12-30
24
Examples 3A-C
The caustic formulations evaluated are as follows:
Ingredient Weight
Percent
Formula 3A 3B 3C
Water to 1000 to 100% to 1000
KELZAN AR 0.2 0.2 -
NaOH (50% aqueous) 9.0 9.0 9.0
Monoethanolamine
(99o active) 3.0 3.0 3.0
Coco Amido Propyl
Betaine (30% 2.0 - 2.0
active, aqueous)
Clz-14 dimethyl
amine oxide (300 0.5 - 0.5
active, aqueous)
Sodium Gluconate 1.6 1.6 1.6
Test Results are as follows:
Formula Irritation Median Particle Surface
Tension
Rating Micrometers Dynes/cm
3A 1 206.5 29.1
3B 1 212.1 52.5
3C 5 107.9 31.7
The level of irritation for formula 3A is rated as
a 1. This is not complete elimination of irritation,
but a significant reduction. Compared to a similar
formula (3C) made without thickener a substantial
improvement has been achieved. Likewise the level of
irritation for the formula (3B) made with KELZAN AR but
without surfactants is also I. The formulation (3C)
without KELZAN AR but with surfactants is rated at an
irritation level of 5. The surface tension results do
CA 02412240 2002-12-30
not appear to correlate with the level of irritation.
Formula (3C) has a low surface tension but is very
irritating, while formula (3A) has a similar surface
tension but shows a greatly reduced level of irritation_
5 Formula 3B is low in irritation but has increased
surface tension. The level of irritation does correlate
to particle size. Highly irritating formulation 3C has
a median particle size of 107.9 micrometers, while the
two reduced irritation formulas have a larger mean
10 particle size of 206.5 and 212.1 micrometers. We
believe the KELZAN AR holds the water droplets together
and mitigates the fine mist that gets into the air and
causes the irritation.
CA 02412240 2002-12-30
26 -
C. Particle Size Analysis and Surface Tension Results
- Acid Formulas
Examples 4A-D
The acidic formula tions aluated
ev are as
follows:
Ingredient Weiaht
Percent
Formula 4A 4B 4C 4D
Water to 1000 to 1000 to 1000 to 1000
Polyvinyl alcohol(PVA) 0.3 0.5 0.3 -
(high molecular weight
fully hydrolyzed 350)
Phosphoric acid (750) 11.625 11.625 11.625 11.625
Citric acid (500) 4.875 4.875 4.875 4.875
Butyl carbitol 4_000 4.000 4.000 4.000
Nonyl phenol ethoxylate 1.000 1.000 - 1.000
(9.5 mole)
Clz_14 dimethyl 3.500 3.500 - 3.500
amine oxide (300)
Test results are as fol lows_
Formula Irritation Median Particle Surface
Tension
Rating Micrometers Dynes /cm
4A 0 259_9 32.3
4B 0 250.3 32.3
4C 3 126.9 34.6
4D 3 165.1 32.1
The level of irritation for the complete formulas
(4A and 4B) made with 0.3 and 0.5o PVA is rated as zero.
Again this rating correlates with particle size and not
surface tension. The particle size results obtained
with formula 4C indicates that it is the combination of
surfactant and PVA that increases the mean particle
size.
The data above suggest that with mean particle sizes
above 200 micrometers that the irritating mist is
greatly reduced. All of the data above were with
CA 02412240 2002-12-30
_.
27
concentrated formulas that are known to be quite
irritating.
We have demonstrated that the cleaning compositions
of the invention which include a highly alkaline
material or a highly acid material as an active cleaning
component in conjunction with other cleaning ingredients
in a thickened aqueous material provides excellent soil
removal properties. We have further shown that the
irritating effects of mists or aerosols generated using
the compositions of the invention in a spray device, can
be substantially removed if the material sprayed results
in a median particle size that is greater than 200 Vim.
The thickened materials of the invention do not lose any
cleaning capacity once formulated to produce a low
particle size aerosol or mist..
The invention resides in the claims hereinafter
appended.
