Note: Descriptions are shown in the official language in which they were submitted.
2046973
DISHWASHING DETERGENT COMP08ITION
FIELD OF THE INVENTION
This invention relates to liquid dishwasher
detergent emulsions and more particularly detergent
emulsion having high alkalinity, high levels of
sequestrant and high temperature stability.
BACKGROUND OF THE INVENTION
Dishwasher detergent compositions are commonly
provided in the form of a solid or a liquid which may be
a slurry, an emulsion or a solution. Such detergents are
formulated for use in household, industrial or
institutional type dishwashers. It is appreciated that
formulations for household dishwashers are of relatively
low alkalinity with suitable levels of surfactant and
various types of sheeting agents. However with
industrial and institutional type dishwashers, the
formulations are considerably more concentrated in the
active ingredients to achieve dishwashing cycles within
the one to two minute range. Solids are the most
suitable medium to incorporate high levels of active
ingredients, because liquid stability is not of concern.
Very high levels of alkalinity and surfactant can be
incorporated into solid detergents. However, dissolution
rates can be a problem particularly with shorter cycle
machines. Granular powders are suited for better
dissolution, but inherently include problems with respect
to dispensing within institutional dishwashing machines.
Metering of powders can be done by machine or manually.
The powders are not always properly dispensed within the
machine for proper cleaning effectiveness during the
short cycle of the machine. Systems designed to meter
powders are very expensive and can only be justified for
use on large industrial or institutional dishwashing
machines.
Liquid forms of dishwasher detergents are preferred
from the standpoint of metering the necessary dose of
detergent into the machine for each cycle and for their
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2 2046973
rates of dissolution in wash water. The problem with
liquid dishwasher detergents is, however, long term
stability. There is considerable difficulty
incorporating high levels of alkalinity and surfactant in
5 a liquid detergent while maintaining flowability and
composition concentration uniformity. One form of liquid
detergent which is popular and has high levels of
alkalinity and surfactants is the slurry. Examples of
slurries are disclosed in United States Patents 4,215,004
and 4,597,889. Partially esterified maleic acid
copolymers are used to stabilize the slurries containing
solid particulate forms of surfactant and/or alkalinity
agents or other active agents. Slurries can, however, be
too viscous for dispensing into institutional type
15 dishwashing machines. Elaborate electronic pumping and
metering system are required to ensure a consistent
dosing of the required amount of dishwasher detergent
liquid into the machine for each cycle.
An aqueous built liquid detergent is disclosed in
20 United States Patent 4,082,684. The detergent includes a
maleic anhydride copolymer partially esterified with a
nonionic surfactant and sodium tripolyphosphate as the
sequestrant. It has been found, however, that the
esterified maleic anhydride polymers are not sufficiently
25 effective to stabilize liquid compositions having high
levels of alkalinity, surfactant and sequestrant,
particularly nonionic surfactants. In this patent, the
formulation is at a pH of 11 which is adjusted by use of
potassium hydroxide. The potassium hydroxide is used to
neutralize the maleic anhydride polymer and the fatty
acid soap. The aqueous built detergent composition is of
fairly high viscosity in the range of 550 to 14
000 centipoise.
A stable detergent emulsion including a nonionic
35 surfactant is disclosed in applicant's United States
Patent 4,826,618. Emulsions are preferred for dispensing
in various types of dishwashers because of their
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3 2046973
flowability and dissolution rates. The emulsion of this
patent is stabilized by the use of a polymeric phase
stabilizer. The stabilizer is prepared by the
polymerization of an unsaturated acrylic acid or a short
chain polycarboxylate in an aqueous alkaline media in the
presence of a nonionic surfactant. Suitable amounts of
unsaturated acrylic acid or short chain polycarboxylate
are admixed in aqueous media together with a nonionic
surfactant and a suitable chemical initiator to begin and
maintain polymerization reaction. Hence the nonionic
surfactant is incorporated into the polymer chain as
differentiated from maleic acid copolymers which are
partially esterified with a nonionic surfactant.
Although the compositions of that patent are suitable for
use in dishwashers, the combined high alkalinity, high
level of sequestrant and high temperature stability of a
detergent emulsion including a nonionic surfactant cannot
always be achieved in the emulsion.
In accordance with the invention disclosed in
applicant's United States Patent 5,176,297, it is desired
to have a dishwasher composition having all of the above
properties so that the dishwasher detergent liquid may be
dispensed within the dishwasher by way of a dispenser
which is mounted inside the dishwasher. Hence the
emulsion has to be stable at the high operating
temperatures of institutional type dishwashers which may
be in the range of 35 to 85C.
SUMMARY OF THE INVENTION
According to an aspect of the invention, a liquid
dishwasher detergent emulsion having high alkalinity,
high levels of sequestrant and high temperature stability
comprises:
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~ ~ ... .;
2046973
i) 4 to 25% w/w of an alkali metal hydroxide
suitable for use in a dishwasher;
ii) 0.2 to 5% w/w of a low foaming free nonionic
surfactant;
iii) 0.5 to 3% w/w of a polyacrylic acid suitable
for enhancing sheeting action on non-porous surfaces;
iv) 15 to 30% w/w of a potassium polyphosphate
sequestering composition enriched in tripolyphosphate and
comprising minimal amounts of ortho and long-chain forms
of polyphosphates to facilitate thereby solubility of
said potassium polyphosphate in water;
v) 2 to 6% w/w of a polymeric emulsion stabilizer
for said free nonionic surfactant, the polymeric emulsion
stabilizer being a chemically associated polycarboxylic
acid polymer and a nonionic surfactant formed by
polymerization of said nonionic surfactant with a
polymerizable reactant selected from the group consisting
of acrylic acid, polyacrylic acid, copolymers of acrylic
acid and an ethylenically unsaturated polycarboxylic acid
or an anhydride thereof, copolymers of ethylenically
unsaturated polycarboxylic acid or anhydride thereof with
a non-carboxy containing ethylenically unsaturated
monomer, said nonionic surfactant and said reactant being
polymerized in an aqueous media;
vi) 0 to 15% w/w of a sequestering agent to enhance
hard water sequestering characteristics of said potassium
polyphosphate; and
vii) water to make up the balance of composition to
100% w/w.
According to another aspect of the invention, a
method of formulating a liquid dishwasher detergent
emulsion to provide a detergent having high alkalinity,
high levels of sequestering agent and high temperature
stability, said method comprising the following steps
wherein each step concentrations are based on % w/w of
said formulated emulsion:
~ 5 2~6973
i) mixing together 2 to 6% w/w of the following to
form a mixture of (a) an aqueous solution of a
polymeric emulsion stabilizer for said free nonionic
surfactant wherein said stabilizer is a chemically
associated polycarboxylic acid polymer and a
nonionic surfactant formed by polymerization of said
nonionic surfactant with a polymerizable reactant
selected from the group consisting of acrylic acid,
polyacrylic acid, copolymers of acrylic acid and an
ethylenically unsaturated polycarboxylic acid or an
anhydride thereof, copolymers of ethylenically
unsaturated polycarboxylic acid or anhydride thereof
with a non-carboxy containing ethylenically
unsaturated monomer, said nonionic surfactant and
said reactant being polymerized in an aqueous media;
and (b) an aqueous solution of 0.5 to 3% w/w of a
polyacrylic acid suitable for enhancing sheeting
action on non-porous surfaces;
ii) adjusting pH of said mixture to within the
range of 8.5 to 9.5 by adding 4 to 25% w/w of an
alkali metal hydroxide suitable for use in a
dishwasher;
iii) adding to said mixture of step ii) with
adequate stirring, 0.2 to 5% w/w of active nonionic
surfactant;
iv) cooling said mixture of step ii) or iii)
before, after or during addition of said nonionic
surfactant to a temperature below cloud point
temperature of said mixture when it includes said
free nonionic surfactant;
v) mixing together the following to form a second
mixture: (a) 15 to 30% wtw of active potassium
polyphosphate sequestering composition enriched in
tripolyphosphate and comprising minimal amounts of
ortho and long-chain forms of polyphosphates to
facilitate thereby solubility of said potassium
2046973
polyphosphate in water; and (b) remaining alkali metal
hydroxide;
vi) forming said emulsion by mixing said mixture of
step iv) with said mixture of step vi).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
It is generally recognized that superior cleaning of
tableware, which includes dishes, flatware, glasses,
cups, mugs and the like, can be achieved by dishwasher
machines. The principal reason for the advantage that
the dishwasher machine has over hand washing is that
considerably stronger detergents and more effective rinse
aids may be used in the dishwasher. Dishwashers can
operate at considerably higher wash water temperatures
and water rinse temperatures to achieve effective
cleaning of the tableware within a one or two minute
cycle. Normally, highly alkaline dishwasher detergents
are used to obtain meaningful cleaning and rinsing.
However, highly alkaline detergents are normally in
powder form for the reasons already discussed: The
formulation, according to this invention, provides
however a liquid detergent emulsion which can be readily
dispensed by a suitable dispenser to provide for a
controlled release for each dishwasher cycle of the
necessary amount of dishwasher detergent emulsion. A
suitable dispenser for this type of emulsion is that
defined in the aforementioned applicant's U.S. Patent
5,176,297.
It is generally understood that detergent emulsions
including particularly nonionic surfactants are unstable,
especially when any attempt is made to provide in
combination a high alkalinity, high sequestering
detergent emulsion which can withstand high temperatures.
The dispenser, as identified in applicants, co-pending
application, is mounted within the dishwasher. The
emulsion contained in the dispenser must retain its
integrity during the time it is in the container of the
dispenser to ensure dispensing of a consistent
,j ~ / ~,.. .
~ 7 2`~46973
concentration of emulsion components for each cycle of
the dishwasher. Applicants have discovered that by a
judicious selection of components for the detergent
emulsion a stable emulsion system is provided which meets
the demands of high alkalinity and high sequestering
properties. Accordingly, the emulsion of this invention
provides the combined functions of detergent action and
rinse agent action to deliver the necessary performance
in a variety of dishwasher machines, particularly
dishwasher machines which are used in small service
organizations which cannot justify large electronically
controlled systems. Another significant advantage of the
emulsion formulation of this invention is that it is able
to accommodate a range in water hardness from soft water
to very hard water by virtue of the inclusion of high
levels of sequestering agent. At a 0.2% use
concentration, the composition is capable of sequestering
up to 175 ppm of CaCO3. This is important in the area of
"low end" dishwashers systems as used in small
enterprises where it is not commercially effective to
control hardness of the water supply.
It has been discovered by the applicants that the
emulsion system of this invention is capable of
incorporating the desired high levels of alkalinity and
sequestering agent by use of a polymeric emulsion
stabilizer for the free nonionic surfactant in the system
and a potassium polyphosphate comprising minimal amounts
of ortho and long-chain forms of polyphosphates to
facilitate thereby solubility of the potassium
polyphosphate in water. By use of these two components,
the necessary amounts of alkali metal hydroxide, low
foaming free nonionic surfactant, polyacrylic acid
sheeting agents and as needed additional sequestering
agents can be incorporated into a liquid dishwasher
detergent emulsion having stability even at high
temperatures which would be experienced within a
dishwasher.
8 2046973
The following discussion of the formulation of this
invention provides concentrations of the various
components. The concentration ranges are based on
percent weight of the component per weight of the final
dishwasher detergent emulsion. It is understood that
where concentration percentages are provided for the
components, they are based on the amount of active
material unless stated otherwise.
To accomplish the high levels of alkalinity in the
dishwasher detergent emulsion, anywhere from 4 to 25% w/w
of an alkali metal hydroxide suitable for use in a
dishwasher is provided. According to a preferred aspect
of the invention, the alkali metal hydroxide may be
selected from the group consisting of sodium hydroxide,
and potassium hydroxide and mixtures thereof. The
especially preferred hydroxide is potassium hydroxide.
Within the stated broad range for the hydroxide, the
preferred concentration of the hydroxide is in the range
of 4 to 20% w/w.
To enhance the detergency of the composition, a
defoaming free nonionic surfactant is used in the
composition. The term "free" as used herein
distinguishes the nonionic surfactant component of the
composition from the nonionic surfactant which is
incorporated in the polymeric emulsion stabilizer defined
in more detail hereinafter. The concentration range for
the surfactant is from 0.5 to 5% w/w with a preferred
range of 0.5 to 2% w/w. It is readily appreciated that a
variety of nonionic surfactants are suitable for use in
dishwashers. Such surfactants may be selected from the
group consisting of linear alcohol ethoxylates, block
copolymers of ethylene oxide and propylene oxide,
alkaline oxide adducts of polyhydric compounds, alkyl
aryl oxalates and amine polyglycol condensates.
Preferred nonionic surfactants may be linear alcohol
ethoxylates or block copolymers of ethylene oxide and
propylene oxide. A preferred ethoxylate is that
9 2046973
manufactured and sold by BASF under the trademark
PLURAFAC LF403. This ethoxylate is a liquid in its
concentrated form with a cloud point of 40C. Its pH at
5% concentration in water is 7 with a density at 23C of
0.94.
Another preferred form of nonionic surfactant is
that sold under the trademark INDUSTROL N-3 by BASF. The
surfactant is an ethylene oxide and propylene oxide block
copolymer with a cloud point of 28 to 33C., an HLB value
of 4.3 to 4.4 and a pH in a 2.5% solution of 5.5 ; 0.7.
An example of an amine polyglycol condensate is the
product Triton CF-32 (trade-mark) sold by Rohm and Haas.
The material is 95% active with a Brookfield viscosity of
550 cps at 25C. Its cloud point for a 1% solution is in
the range of 20-27C.
As is understood by those skilled in the art,
polyacrylic acids are useful in dishwasher detergents to
enhance sheeting action on non-porous surfaces, such as
tableware. The range of the polyacrylic acid is from 0.5
to 3% w/w with a preferred concentration range of 0.5 to
1.5% w/w. There are a variety of polyacrylic acids
suitable for use in dishwasher detergents. Such
polyacrylic acids have a molecular weight in the range of
2000 to 4500 with a preferred molecular weight of about
4500. Preferred polyacrylic acids for use in this
detergent composition are available from Rohm and Haas
under the trademark ACUSOL. Two preferred ACUSOL
compositions are ACUSOL 420 and ACUSOL 445. ACUSOL 420
has an average molecular weight of 2000 with partial
sodium salt and 20% neutralized. The concentrate has a
specific gravity at 25C of 1.104 and a pH of 3.8 as a
concentrate. Total solids in the commercially available
composition is 54% with a Brookfield viscosity at 25C of
725 + 100 cps. The ACUSOL 445 has an average molecular
weight of 4500 with partial sodium salt and 20%
neutralized. The concentrate has total solids of 48%
with a density of 9.2 pounds per gallon at 25C. The pH
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of the concentrate is 4 and a Brookfield viscosity at
25C of 800 cps.
In view of the emulsion being used in environments
where the water hardness cannot be controlled or it is
not commercially feasible to control water hardness, it
is desirable to have high levels of polyphosphate
sequestrant in the emulsion. To ensure a stable
emulsion, it has been found that a potassium
polyphosphate is preferred which is enriched in
tripolyphosphate. The potassium polyphosphate comprises
minimal amounts of ortho and long-chain forms of
polyphosphate. This feature facilitates solubility of
the potassium polyphosphate in water and hence in the
emulsion system. In addition, the majority of
tripolyphosphate considerably enhances the cleaning
performance of the composition. A preferred potassium
polyphosphate is available from FMC under the trademark
RAPISOL. The polyphosphate is in granular form having a
P205 % by weight of 47. The granular composition has very
low levels of ortho-phosphate of 0 to 4% with little if
any of the long chain forms of polyphosphates which are
insoluble and should be removed before formulation or
after the formation of the emulsion. As is appreciated,
these long chain forms of polyphosphates are insoluble
and thereby affect the emulsions long term stability and
forms a sediment in the parlact. Removal of the long
chain form may be accomplished by filtration with before
or after formation or by centrifugation before
formulation. The pH of the polyphosphate composition as
a 1% solution is in the range of 9 to 9.6. The
solubility of the polyphosphate in grams per kilogram of
water is:
at 10C - 2780
at 25C - 1930
at 50C - 2160
The polyphosphate has a density in grams per cc ranging
from 0.6 to 0.9.
11 21~6973
.
The concentration of the potassium polyphosphate in
the emulsion is very high and may range from 15 to 30%
w/w. The preferred concentration of the potassium
polyphosphate in the emulsion is in the range of 15 to
25% w/w. As is appreciated by those skilled in the art
in building a detergent composition, there is a balance
in the respective amounts of alkali metal hydroxide and
polyphosphate used in the composition. This balance is
generally in the form of the greater the concentration of
the polyphosphate, the lower the concentration of the
alkali metal hydroxide. For example, for an upper limit
of the polyphosphate, the lower limit of the metal
hydroxide is used and vice-versa.
In order to stabilize the emulsion of the nonionic
surfactant in the system, a suitable polymeric emulsion
stabilizer is employed. According to a preferred aspect
of the invention, a useful polymeric emulsion stabilizer
is defined in applicant's issued United States patent
4,826,618 dated May 2, 1989. The emulsion stabilizer is
suitable for stabilizing the free nonionic surfactant in
the liquid composition. The stabilizer is a
polycarboxylic acid polymeric backbone chemically
associated with a nonionic surfactant. The polymeric
backbone is selected from the group consisting of
polyacrylic acid, copolymer of acrylic acid and an
ethylenically unsaturated polycarboxylic acid or
anhydride thereof, copolymers of ethylenically
unsaturated polycarboxylic acid or anhydride thereof with
a non-carboxylic containing ethnically unsaturated
monomer. The stabilizer may be the reaction product of
acrylic acid, polycarboxylic acid and mixtures thereof
polymerized in the presence of a water soluble nonionic
surfactant. The concentration of the polymeric emulsion
stabilizer in the composition is in the range of 2 to 6%
w/w with a preferred concentration in the range of 4 to
5% w/w.
Preferred polymeric emulsion stabilizer is composed
2046973
12
of acrylic acid groups polymerized in a head to tail
manner with one or more branch points along the polymer
chain. Some of the branch points consist of acrylic acid
chains while the other branch points consist of linear
alcohol ethoxylate or nonylphenol ethoxylate attached to
the backbone by a carbon-carbon bond near the hydroxyl
end of the surfactant.
Preferred polymeric emulsion stabilizers are
available from Diversey Corp. and identified by terms B-
35 and B-36. The B-35 stabilizer is distinguished from
the B-36 stabilizer on the basis of the surfactant used
in the polymerization step. In the B-35 stabilizer, the
linear alcohol ethoxylate is incorporated into the chain
whereas in the B-36 stabilizer, the nonylphenol
ethoxylate is incorporated into the chain.
The polymeric emulsion stabilizers may be made in
accordance with the details of the process provided in
applicant's United States Patent 4,826,618. For
convenience, however, a brief outline of
the process is as follows.
The polymeric emulsion stabilizer employed in the
present invention is produced by admixing a reactant
compound selected from the group consisting of
unsaturated acrylic acids, polycarboxylic acids and
mixture thereof in water at concentrations between about
5 percent by weight and about 40 percent by weight based
on the total weight of the solution.
The reactant compound is, generally, selected from
the group consisting of acrylic acid, polyacrylic acid,
copolymers of maleic anhydride and methylvinyl ether,
copolymers of maleic anhydride and ethylene, copolymers
of maleic anhydride and styrene, copolymers of acrylic
and maleic anhydride, and mixtures thereof. Preferably,
the reactant compound is selected from the group
consisting of acrylic acid, polyacrylic acid and mixtures
thereof. Where polyacrylic acid is employed it generally
has a molecular weight below about 500,000. The
2046973
- 13
polyacrylic acid generally has a molecular weight below
about 40,000 to about 200,000; preferably below 50,000.
Suitable polyacrylic acids are commercially available
from B.F. Goodrich under the trade-mark GOODRITE K-722.
Also admixed in the solution is a nonionic
surfactant present in an amount between about 0.4 and
about 45 percent, by weight. The amount of nonionic
surfactant added to the solution and adapted to be
chemically associated with the polycarboxylate polymer to
be formed can vary. The nonionic surfactant adapted to
be bound preferably is selected from the group consisting
of alcohol ethoxylates, alkyl aryl ethoxylates, products
of the condensation reaction of ethylene oxide and
propylene oxide, and ethylenediaminetetraacetate, adducts
of ethylene oxide and propylene oxide, ethoxylated-
propoxylated phosphate esters, alkylene oxide adducts of
polyhydric compounds and mixtures thereof. Preferably,
the surfactant employed is an alcohol ethoxylate or an
alkyl aryl ethoxylate and mixtures thereof. An example
of one class of compounds which can be employed
successfully in the preparation of the modified polymeric
emulsion stabilizer is the nonylphenol ethoxylates.
The nonionic surfactant chosen for preparation of
this polymeric emulsion stabilizer generally has a cloud
point between about room temperature and about 212=F
(about 25C to about 100C); preferably between about
180F and about 200F (about 82C and about 93C). In
general, where surfactants having cloud points in the
higher portion of the preferred range are employed,
higher temperatures and increased surfactant
concentrations can be employed effectively. Where
surfactants having lower cloud point values are employed,
lower reaction temperatures and decreased surfactant
concentrations can be used.
2û~6973
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14
Initiation of polymerization may occur by a variety
of methods. Generally, a chemical compound is added to
the solution as an initiating agent. The amount of
chemical initiator used in polymerization is related to
the molecular mass of the polymer to be generated. The
polymeric emulsion stabilizers, employed in the detergent
emulsion of the present invention, preferably, have
molecular mass between about 5000 and about 200,000. To
obtain a polymer having a molecular mass in this range
initiator, in an amount between about 0.1 and about 2.5
percent by weight based on the total solution
concentration can be used.
The chemical initiator used is selected from the
group consisting of alkali metal persulfates, ammonium
persulfate, azobis-(isobutyronitrile), t-butyl
hydro-peroxide and mixtures thereof. Such initiators are
commonly referred to as oxidizing agents. Coupled
initiators may also be successfully employed in the
production of the polymeric emulsion stabilizer.
Suitable coupled initiator include one of the
above-mentioned oxidizing agents coupled with a reducing
agent selected from the group consisting of hydrogen
peroxide, alkali metal bisulfites, and mixtures thereof.
Preferably, the reducing agent is selected from the group
consisting of sodium bisulfite, hydrogen peroxide, and
mixtures thereof.
The polymerization reaction preferably occurs in
acidic aqueous media having a pH between about 2 and
about 6. To achieve and maintain the pH at the desired
level, alkali metal hydroxides may be added to partially
neutralize the carboxylic acid present in solution. Such
agents are preferably selected from the group consisting
of alkali metal hydroxides and mixtures thereof. In the
preferred embodiment, sodium hydroxide is employed.
Polymerization generally occurs at a reaction
temperature between about 100F and about 190F over a
period of between about 30 minutes and 24 hours. The
2046973
polymer produced is water soluble and is present in an
aqueous solution and is capable of stabilizing emulsions
containing nonionic surfactants. Without being bound to
any theory, it is believed that the polymer produced has
a polycarboxylate backbone with approximately 1 to 5
percent by weight nonionic surfactant associated
chemically therewith. The polymeric emulsion stabilizer
is, preferably, maintained in an aqueous medium at a
concentration between about 1 and about 40 percent by
weight polymer and is employed herein as the aqueous form
thereof.
The hard water sequestering properties of the
potassium polyphosphate may be enhanced by use of
additional sequestering agents which may be optionally
provided in the composition. Concentrations of the
sequestering agents when used may be up to 15% w/w with a
preferred concentration in the range of up to 10 to 13%
w/w. Suitable sequestering agents, which enhance the
sequestering properties of the polyphosphate, include
trisodium nitrilotriacetate and tetrasodium methylenedi-
aminetetraacetate dihydrate. The trisodium
nitrilotriacetate (NTA Nas) is available from several
sources which include BASF, W.R. Grace & Co. (Organics
Chemical Division) and Monsanto Canada Inc. The percent
actives in the commercially available composition is a
minimum of 40% of NTANa3 with a chelating activity in the
range of 156 mg CaCO3 per gram. The pH of a 1% solution
of the NTANa3 is 11 to 12.
The tetra sodium ethylenediaminetetra acetate
dihydrate (EDTA) is commercially available from Clough
Chemical Company Limited under the trademark QUESTAL
Special. The percent actives in the commercial
composition is in the range of 41% with a specific
gravity of 1.32. The pH of the 1% solution is in the
range of 11.6 with a cv of 12.7.
Water, as used in the aqueous solutions of the
composition and as added during formulation, is
`- 2046973
16
preferably softened water to avoid depletion of
sequestering agents. By softened water, it is intended
to cover water that has minimal calcium and magnesium
ions. If desired, it is appreciated that de-ionized
S water may be used instead of softened water for the
formulation.
To achieve optimum stability for the liquid
dishwasher detergent emulsion of this invention, the
order in which the components of the detergent are
combined is significant. It has been found by
experimentation that the emulsion stabilizer in
combination with the polyacrylic acid should be
neutralized to a pH in the range of 8.5 to 9.5 before the
addition of the nonionic surfactant. Although the need
to adjust the pH is not fully understood and not wishing
to be bound to the following, it is theorized that the
addition of the alkali metal hydroxide causes ionization
of the carboxylic groups of the emulsion stabilizer as
well as the polyacrylic acid. Hence the polymeric
emulsion stabilizer becomes a polyelectrolyte, where
negative charges on adjacent carboxylic groups repel one
another which leads to a stretching of the molecule.
This stretched polymer molecule in conjunction with the
added nonionic surfactant forms a mixed micelle. Should
the pH be increased to a level greatly in excess of 9.5,
the higher alkalinity attacks the nonionic surfactant as
a competitive reaction to the micelle formation.
Although in theory this is thought to be an explanation
for the stability achieved, it has been determined
through experimentation that neutralization of the acidic
stabilizer and polyacrylic acid to a pH in the range of
8.5 to 9.5 significantly enhances the stability of the
subsequently formed emulsion.
A second aspect in forming the emulsion is the order
in which the prepared mixtures of emulsion stabilizer,
polyacrylic acid, nonionic surfactant and the second
mixture of potassium polyphosphate, remaining alkali
- 17 2~469~3
metal hydroxide and sequestering agent is present. The
second mixture is considerably larger in volume to form
the preferred droplet size and thereby make a stable
emulsion. It has been found that the first mixture is
added to the second mixture with adequate stirring or
agitation to form the stable emulsion.
A third aspect of the process which greatly enhances
the formation of a stable emulsion is cooling of the
first mixture to below the cloud point of the mixture
when it includes the nonionic surfactant. As is
appreciated, the cloud point of the first mixture will
vary in accordance with the nonionic surfactant used and
its concentration in the first mixture. For preferred
components of the first mixture, it has been found that
the cloud point is in the range of 9 to 14C at a pH in
the range of 9.0 to 9.5. Cooling of the second mixture
is optional before combining the first mixture with the
second mixture in forming the emulsion. Absence of
cooling of the first mixture results in a poor emulsion
which does not have sufficient stability for long term
storage and use particularly at the high operating
temperatures of a dishwasher.
The preferred method of formulating the liquid
dishwasher detergent emulsion of this invention to
provide an emulsion having high alkalinity and high
levels of sequestering agent which is stable at high
temperatures is as follows:
1. an aqueous solution of the polymeric emulsion
stabilizer of the selected type and at an
active concentration of 2 to 6% w/w is mixed
with an aqueous solution of the desired
polyacrylic acid solution.
2. this acidic mixture is neutralized to a pH in
the range of 8.5 to 9.5 preferably 9 using a
suitable alkali metal hydroxide, preferably
potassium hydroxide.
- 2046973
18
3. the mixture is then cooled to a temperature
below the cloud point of the mixture when it
includes the free nonionic surfactant.
4. to this cooled mixture the free nonionic
surfactant is then added. It is appreciated,
however, that cooling may be affected
alternatively after the nonionic surfactant is
added to the neutralized composition or during
the addition of the nonionic surfactant. This
constitutes the first mixture.
5. a second mixture is formed by mixing the
potassium polyphosphate with the remaining
alkali metal hydroxide, preferably potassium
hydroxide with a suitable sequestering
enhancing agent if used. The potassium
polyphosphate is optionally filtered to remove
any insoluble long chain polyphosphates before
inclusion in the mixture.
6. due to the heat of reaction in adding the
remaining potassium hydroxide to the potassium
polyphosphate, the second mixture is optionally
cooled to maintain approximately room
temperature. This constitutes the second
mixture which is of a volume greater than the
first mixture.
7. to form the emulsion, the second mixture is
agitated at a sufficient rate to form an
emulsion as the first mixture is added to the
second mixture.
8. after complete addition of the first mixture,
the resultant formulation is agitated for the
desired length of time to form the stable
emulsion. For example, by use of a suitable
blade mixer, stirring for approximately 15 to
20 minutes after completion of addition of the
first mixture to the second mixture forms a
suitable stable emulsion.
2046973
.. 19
9. optionally the emulsion is filtered to remove
any insoluble long chain polyphosphates before
the emulsion is packaged.
The following examples set out various formulations
for a variety of applications to demonstrate the range of
components of the formulated emulsion. Although the
following examples exemplify various preferred
compositions of the invention, it is understood that such
specific compositions are not in any way to be
interpreted as limiting the scope of the appended claims.
EXAMPLE 1
ln accordance With the following formulation method,
the compositions of Table 1 are formulated in accordance
with the following method.
1. Mix water/emulsion stabilizer/polyacrylic acid.
2. Stir between each addition.
3. Neutralize to pH 9 using KOH, 45% solution.
4. Cool mixture to below 12C.
5. Add to Mixture in (4) nonionic surfactant.
6. In a separate vessel, mix RAPISOL, 60%
(filtered)/QUESTAL Special/KOH, 45%.
7. Cool mixture from (6) to below 12C.
8. With vigorous stirring (370 rpm, blade mixer)
add mixture from (5) to mixture from (6).
9. Cooling can be removed.
10. Continue stirring approximately 15 to 20
minutes.
All of the formulations of Table 1 were stable. The
stability tests were conducted on each of the
formulations as follows. The test consisted of Freeze-
Thaw Stability, Elevated Temperature Stability and Actual
Use Temperature Cycling Stability.
Freeze Thaw StabilitY
~04 ~ 973
Each product was subjected to 3 cycles of !6 hours
(overnight) at -20C with 8 hours (day) at room
temperature. Quality of product was then checked.
Elevated Temperature Stability
Each product was subjected to storage at 40C for a
maximum of 3 months or until failure. Failure is
considered any dramatic changes in color, viscosity or
the homogeneity of the product.
Actual Use Temperature Cycling Stability
To determine a product's stability, it is best to
attempt to simulate the environments to which the
products of these examples will be exposed. The
formulations of Example 1 and the following Examples were
placed in a Hobart~ AM12 machine. The formulations were
in 100 ml jars. The machine was then put through 45
complete wash cycles. There was a half hour rest time
between every 5 cycles of the total 45 cycles. The
product was then allowed to cool after the 45 cycles were
completed and the stability of emulsion evaluated.
In each of the above tests for the formulations, one
consideration for a stable emulsion is that it
demonstrate homogeneity after the test. As set out in
the Temperature Stability tests, failure for any of the
tests was considered to be any dramatic changes in color,
viscosity or the homogeneity of the product.
- 20~6973
21
TABLE 1
Formulations B C D E F
Water 44 39 34 29 24 20
5- B35 stabilizer 4 4 4 4 4 4
Plurafac LF403
Rapisol, 60% (filtered) 36 36 36 36 36 36
KOH, 45% 11 11 11 11 11 11
NTA-150 0 5 10 15 20 24
10 - Acrysol LMW45X 4 4 4 4 4 4
EXANPLE 2
In accordance with the formulation method and
stability test of Example 1, the compositions of Table 2
were made to form stable emulsions.
TABLE 2
Formulations _ B C D E F G H
Water 22 23 22 21 20 20.8 31 22
B35 stabilizer 5 4 4 4 4 32 4 4
Acrysol LMW45X 2 2 3 4 4 4 4 2
Plurafac LF403
Rapisol, 60% (filtered) 36 36 36 36 36 36 36 36
KOH, 45% 10 10 10 10 10 11 10 11
NTA-150 (4.5%) 24 24 24 24 24 24 24 24
EXAMPLE 3
In accordance with the formulation method and
stability test of Example 1, the compositions of Table 3
were made to form stable emulsions.
TABLE 3
Formulations _ B C D E F G H
Water 11 7 11.2 716 10.2 9.2 13
B35 stabilizer 4 8 4 4 0 5 6 4
Acrysol LMW45X 4 4 4 4 4 4 4 2
Industrol N-3 1 0.8 1 0
Rapisol, 60% (filtered) 36 36 36 37 36 36 36 36
KOH, 45% 11 11 11 11 11 11 11 11
Questal Special (42.8%) 33 33 33 36 33 33 33 33
EXAMPLE 4
In accordance with the formulation method and
stability test of Example 1, the compositions of Table 4
were made to form stable emulsions.
20469~3
22
TABLE 4
Formulations _ B C D E
Water 4 92 8.2 7.211
B35 stabilizer 4 4 5 6 4
Acrysol LMW45X 4 4 4 4 2
Industrol N-3 1 0.8 0.8 0.8
Rapisol, 60% (filtered) 36 36 3636 36
KOH, 45% 46 46 46 46 46
EXAMPLE 5
In accordance with the formulation method and stability
test of Example 1, the compositions of Table 5 were made to
form stable emulsions.
TABLE 5
Formulations _ B C D E F
Water 11 12 10.2 9.2 7 13
B35 stabilizer 4 4 5 6 4 4
Acrysol LMW45X 4 4 4 4 4 2
Plurafac LF403 1 0.8 0.8 0.8
Rapisol, 60% (filtered) 36 36 36 36 37 36
KOH, 45% 11 11 11 11 11 11
Questal Special 33 33 33 33 36 36
EXANPLE 6
In accordance with the formulation method and stability
test of Example 1, the compositions of Table 6 were made to
form stable emulsions.
TABLE 6
Formulations _ B C D
Water 9 92 8.2 11
B35 stabilizer 4 4 5 4
Acrysol LMW45X 4 4 4 2
Plurafac LF403 0.8 0.8
Rapisol, 60% (filtered) 36 36 36 36
KOH, 45% 46 46 46 46
Although preferred embodiments of the invention are
described herein in detail, it will be understood by
those skilled in the art that variations may be made
thereto without departing from the spirit of the
invention or the scope of the appended claims.
