Note: Descriptions are shown in the official language in which they were submitted.
2~9~4~
CP-IR-468lQ
LINEAR VISCOELASTIC AQUEOUS
LIQUID AUTOMATIC DISHWASHER
DETERGENT COMP05ITION
Background of the Invention
Liquid automatic dishwasher detergent compositions, both
aqueous and nonaqueous, have recently received much attention,
and the a~ueous products have achieved commercial popularity~
The acceptance and popularity of the liquid formulations
a~ compared to the more conventional powder product~ stems
from the convenience and perfor~ance of the liquid products.
However, even the best of the currently available liquid
formulations still suffer from two major problems, product
phase instability and bottle residue, and to some extent c~p
leakage ~rom the dispenser cup of the automatic dishwashin~
machine.
Representati~e of the relevant patent art in this area,
mention i~ made of Rek, U.S. Patent 4,556,504; Bush, et al.,
U.S. Patent 4,226,736; Ulri~h, U.S. Patent 4,431,559;
Sabatelli, U.S. Patent 4,147,650; Paucot, U.S. Patent
4,n79,015; ~eikhem, U.S. Patent 4,116,849; Milora, U.S. Patent
4,521,332; Jones, U.S. Patent 4,597,889; Heile, U.S. Patent
4,512,908; Laitem, U.S. Patent ~,753,748; S~atelli, U.S.
Patent 3,579,455; Hynam, U.S. Patent 3,6~4,722: other patents
relating to thickened detergent compositions include U.S.
Patent 3,985,668; U.K. Patent Applications G~ 2,116,199A and
G~ 240,450A; U.S. Patent 4,511,487; U.S. Patent 4,752,409
, . ~,' : . . ':
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. . . -
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2~S~84~ `
(Drapier, et al.); U.S. Patent 4,801,395 (Drapier, et al.);
U.S. Patent 4,801,395 (Drapier, et al.).
The present invention provides a solution to the above
problems .
Brief Description of the Drawinqs
Figures 1-13 are rheograms, plotting elastic modules G'
and viscou~ modulus G~ as a function of applied strain, for
the compositions of Example 1, Formulations A, C, D, G, J, H,
I and K, Example 2, A and ~, Example 3, L and M and
Comparative Example 1, respectively.
Summary of the Invention
According to the present invention there is provided a
novel aqueous liquid automatic dishwasher detergent
composition. The composition is characterized by itq linear
~iscoelastic behavior, substantially indefinite stability
against phase separation or settling of dissolved or suspended
particles, low levels of bottle residue, relatively high bulk
density, and substantial absence of unbound or free water.
This unique combination of properties is achieved by virtue of
the incorporation into the aqueous mixture of dishwashing
detergent surfactant, alkali metal detergent builder salt(s)
and chlorine bleach compound, a ~mall but effective amount of
~5 high molecular weight cross-linked polyacrylic acid type
thickening agent, a physical stabilizing amount of a long
chain fatty acid or ~alt thereof, and a source of potassium
ions to pro~ide a pota~sium/sodium weight ratio in the range
.: :
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., - ;
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. .
. .
2~3~46
of from 1;2 to 45:1, such that sub~tantially all of the
detergent builder salts and other normally solid detergent
additives present in the composition are present dissolved in
the aqueous phase. The compositions are fur~her characterized
by a bulk density of at least 1.26 g/cc, such that the
density of the polymeric phase and the density of the aquéous
(continuous) phase are approximately the same.
~etailed Description of the Preferred Embodiments
The compositions of this invention are aqueous liquids
containing various cleansing active ingredients, detergent
adjuvants, structuring and thickening agents and stabilizing
components, although some ingredients may serve more than one
of these functions.
The advantageous characteristics of the compositions of
this invention, including physical ~tability, low bottle
residue, high cleaning performance, eOg. low spotting and
filming, dirt residue removal, and so on~ and superior
aesthetics, are believed to be attributed to several
interrelated factors such as low solids, i.e. undissolved
particulate content, product density and linear viscoelastic
rheology. These factors are, in turn, dependent on ~everal
critical compositional components of the formulation~, namely,
(1) the inclusion of a thickening effective ~mount of
polymeric thickening agent having high water absorption
capacity, exemplified by high molecular weight cross-linked
polyacrylic acid, (2) inclu~ion of a physical stabilizing
amount of a long chain fatty acid or salt thereof, (3)
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2~8~
potassium ion to sodium ion weight ratio K/Na in the range of
from 1:2 to 45:1, especially from 1:1 to 3:1, and (4) a
product bulk density of at least 1.26 g/cc, such that the
bulk densi~y and liquid phase densi~y are the same.
The polymeric thickening agents contribute to the linear
viscoelastic rheology of the invention compositions. As used
herein, "linear viscoelastic "or" linear viscoelasticity"
means that the elastic (storage) moduli (G') and the viscous
(loss) moduli (G") are both substantially independent of
strain, at least in an applied strain range of from 0-50~, and
preferably over an applied strain range of from 0-80~. More
specifically, a composition i8 considered to be linear
viscoelastic for purposes of this invention, if over the
9train range of 0-50~ the elastic moduli G' has a minimum
value of 100 dynes/sq.cm., preferably at least 250
dynes/sq.cm., and varies less than 500 dynes/sq.cm,
preferably less than 300 dynes/sq.cm., especially preferably
less than 100 dynes/sq.cm. Preferably, the minimum value of
G' and maximum variation o~ G~ applies over the strain range
o~ 0 to 80~. Typically, the variation in Io99 moduli G~ will
be less than that of G~. As a further characteristic of the
preferred linear viscoelastic compositions the ratio of G"/G
(tan~) is less than 1, preferably less than 0.8, but more than
0.05, preferably more than 0.2, at least over the strain range
2S of 0 to 50~, and preferably over the strain ran~e of 0 to 80~.
It should be noted in this regard that ~ strain is shear
strain xlO0.
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~9~
By way of further explanation, the elastic (storage)
modulus G~ is a measure of the energy stored and retrieved
when a strain is applied to the composition while viscous
(loss) modulus G~ is a measure to the amount of energy
dissipated as heat ~hen strain is applied. Therefore, a value
of tan~,
0.05~ tan
preferably
0.2 c tan~ ~ 0.8
means that the compositions will retain sufficient energy when
a stress or strain is applied, at least over the extent
expected to be encountered for products of this type, for
example, when poured from or shaken in the bottle, or stored
in the dishwasher de~ergent dispenser cup of an automatic
dishwashing machine, to return to its previous condition when
the stress or strain is removed. The compositions with tan
values in these ranges, therefore, will also have a high
cohesive property, namely, when a shear or strain is applied
to a portion of the composition to cause it to flow, the
surrounding portions will follow. As a result of this
cohesiveness of the subject linear viscoelastic compositions,
the compositions will readily flow uniformly and homogeneously
from a bottle when the bottle is tilted, thereby contributing
to the physical (phase) stability of the formulation and the
low bottle residue (low product loss in the bottle) which
characterizes the invention compositions. The linear
viscoelastic property also contributes to improved physical
stability against phase separation of any undissolved
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suspended particles by providing a resistance to movement of
the particles due to the strain exerted by a particle on the
surrounding fluid medium.
Also contributing to the physical stability and low
bottle residue of the invention compositions is the potassium
to sodium ion ratios in the range of 1:2 to 45:1, preferably
1:1 to 4:1, especially preferably from 1.05:1 ~o 3:1, for
example 1.1:1, 1.2:1, 1.5:1, 2:1, or 2.5:1. At these ratios
the solubility of the solid salt components, such as detergent
builder salts, bleach, alkali metal silicates, and the like,
is substantially increased gince the presence of the potassium
(K+) ions requires less water of hydration than the sodium
(Na+) ions, such that more water is available to dissolve
these salt compounds. Therefore, all or nearly all of the
normally solid components are present dissolved in the aqueous
phase. Since there is none or only a very low percentage,
i.e. less than 5~, preferably less than 3~ by weight, of
suspended solids present in the formulation there is no or
only reduced tendency for undissolved particles to settle out
~0 of the compositions causing, for example, formation of hard
masses of particles, which could result in high bottle
residues (i.e. 1099 of product). Furthermore, any undissolved
solids tend to be present in extremely small particle sizes,
usually colloidal or sub-colloidal, such as 1 micron or less,
thereby ~urther reducing the tendency for the undissol~ed
particles to settle.
A still further attribute of the invention compositions
contributing to the overall product stability and low bottle
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2~6984~
residue is the high water absorption capacity of the cross-
linked polyacrylic acid type thickening agent. As a result of
this high water absorption capaclty virtually all of the
aqueous vehicle component is held tightly bound to the polymer
matrix. Therefore, there is no or substantially no Eree water
present in the invention compositions. This absence of free
water (as well as the cohesivenesg of the composition) is
manifested by the observation tha~ when the composition is
poured from a bottle onto a piece of water absorbent filter
paper virtually no water is absorbed onto the filter paper
and, furthermore, the mass of the linear viscoelastic material
poured onto the filter paper will retain its shape and
structure until it is again subjected to a stress or strain.
As a result of the absence of unbound or free water, there is
virtually no phase separation between the aqueous phase and
the polymeric matrix or dissolved solid particles. This
characteristic is manifested by the fact ~hat when the subject
compositions are subjected to centrifugation, e.g. at 1000 rpm
for 30 minutes, there i9 no phase separation and the
composition remains homogeneous.
Xowever, it ha~ also been di~covered that linear
viscoelasticity and K/Na ratios in the above-mentioned range
do not, by themselves, a~sure long term physical stability (as
determined by phase separation). In order to maximiæe
physical (phase) stability, the dengity of the composition
should be controlled such that the bulk density of the liquid
phase is approximately the same as the bulk density of the
entire compo~ition, including the polymeric thickening agent.
2~98~6
This control and equalization of the densities is achieved,
according to the invention, by providing the composition with
a bulk density of at least 1.26 g/cc, preferably at least 1.32
g/cc, up to 1.42 g/cc, preferably up to 1.40 g/cc.
Furthermore, to achieve these relatively high bulk densities,
it is important to minimize the amount of air incorporated
into the composition (a density of 1.42 g/cc is essentially
equivalent to zero air content).
It has previously been found in connection with other
types of thickened aqueous liquid, automatic dishwasher
detergent compositions that incorporation of finely divided
air bubbles in amounts up to 8 to 10~ by volume can function
effectively to stabili2e the composition against phase
separation, but that to prevent agglomeration of or escape of
the air bubbles it was important to incorporate certain
surface active ingredients, especially higher fatty acids and
the salts thereof, such as stearic acid, behenic acid,
palmitic acid, sodium stearate, aluminum stearat~, and the
like. These surface active agents apparently functioned by
forming an interfacial film at the bubble surface while also
forming hydrogen bonds or contributing to the electrostatic
attraction with the suspended particles, such that the air
bubbles and attracted particle~ formed agglomerates of
approximately the same density as the density of the
continuous liquid phase.
Therefore, in a preferred embodiment of the present
invention, stabilization of air bubbles which may become
incorporated into the composition~ during normal processing,
2~84~
such as during various mixing steps, is avoided by post-adding
the surface active ingredients, including fatty acid or fatty
acid salt stabilizer, to the remainder of the composition,
under low shear conditions using mixing devices des~gned to
minimize cavitation and vortex formation.
As will be described in greater detail below the surface
active ingredients present in the composition will include the
main detergent surface active cleaning agent, and wlll also
preferably include anti-foaming agent and higher fatty acid or
salt thereof as a physical stabilizer.
Exemplary of the cross-linked polyacrylic acid-type
thickening agents are the products sold by B.F. Goodrich under
their Carbopol trademark, especially Carbopol 941, which i9
the mos~ ion-insensitive of this class of polymers, and
Carbopol 940 and Carbopol 934. The Carbopol resins, also
known as "Carbomer", are hydrophilic high molecular weight,
cross-linked acrylic acid polymer~ having an average
equivalent weight of 76, and the general structure illustrated
by the following formula:
/ H H
-- ~ C - C ~---
H0 - ~ O n.
Carbopol 941 ha~ a molecular weight of 1,250,000; Carbopol
940 a molecular weight of approximately 4,000,000 and Carbopol
934 a molecular weight of approximately 3,000~000. The
Carbopol resins are cross-linked with polyalkenyl polyether,
e.g. 1~ of a polyallyl ether of ~ucrose having an average of
'~
2~8~
5.8 allyl groups for each molecule of sucrose. Further
detailed information on the Carbopol resins is avallable ~rom
B.F. Goodrich, see, for example, the B.F. Goodrich catalog GC-
67, Carbopol~ Water Soluble Resins.
While most favorable results have been achieved with
Carbopol 941 polyacrylic resin, other lightly cross-linked
polyacrylic acid-type thickening agents can also be used in
the compositions of this invention. As used herein
"polyacrylic acid-type" refers to water-soluble homopolymers
of acrylic acid or methacrylic acid or water-dispersible or
water-soluble salts, esters or amides thereof, or water-
soluble copolymers of these acids of their salts, esters or
ameides with each other or with one or more other etylenically
unsaturated monomers, such as, for example, styrene, maleic
acid, maleic anhydride, 2-hydroxyethylacrylate, acrylonitrile,
vinyl acetate, ethylene, propylene, and the li~e.
The homopolymers or copolymers are characterized by their
high molecular ~ei~ht, in the range of from 500,000 to
10,000,000, preferably 500,000 to 5,000,000, especially from
1,000,000 to 4,000,000, and by their water solubility,
generally at least to an extent of up to ~ by weight, or
more, in water at 25C.
These thickening agents are used in their lightly cross-
lin~ed form wherein the cross-linking may be accomplished by
means known in the polymer arts, as by irradiation, or,
preferably, by the incorporati~n into the monomer mixture to
be polymerized of known chemical cross-linking monomeric
agents, typically polyunsaturated (e.g. diethylenically
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unsaturated) monomers, such as, for example, divinylbenzene,
divinylether of diethylene glycol, N, N'-methylene-
bisacrylamide, polyalkenylpolyethers (such as described
above), and the like. Typically, amounts of cross-linking
agent to be incorporated in the final polymer may range from
0.01 to 1.5 percent, preferably from 0.05 to 1.2 percent,
and especially, preferably from 0.1 to 009 percent, by
weight of cross-linking agent to weight of total polymer.
Generally, those skilled in the art will recognize that the
degree of cross-linking should be sufficient to impart some
coiling of the otherwise generally linear polymeric compound
while maintaining the cross-linked polymer at least water
dispersible and highly water-swellable in an ionic aqueous
medium. It is also understood that the water-swelling of the
polymer which provides the desired thickening and viscous
properties generally depends on one or two mechani~ms, namely,
conversion of the acid ~roup containing polymers to the
corresponding salts, e.g. sodium, generating negative charges
along the polymex backbon~, thereby causing the coiled
molecules to expand and thicken the aqueous solution; or by
formation of hydrogen bonds, for example, between the carboxyl
groups of the polymer and hydroxyl donor. The former
mechanism is especially important in the present invention,
and therefore, the preferred polyacrylic acid-t~pe thickening
agents will contain free carboxylic acid ~COOH) groups along
the polymer backbone. Also, it will be under~tood that the
degree of cross-linking should no~ be 90 high as to render the
cross-linked polymer completely insoluble or non-dispersible
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in water or inhibit or prevent the uncoiling of the polymer
molecules in the presence o~ the ionic aqueous system.
The amount of at least one high molecular weight, cross-
linked polyacrylic acid or other high molecular weight,
hydrophilic cross-linked polyacrylic acid-type thickening
agent to impart the desired rheological property of linear
viscoelasticity will generally be in the range of from 0.1 to
2~, preferably from 0.2 to 1.75%, ~y weight, based on the
weight of the composition, although the amount will depend on
the particular cro~s-linking agent, ionic strength of the
composition, hydroxyl donors and the like.
The compositions of thls invention must include
sufficient amount of potas~ium ions and sodium ions to provide
a weight ratio of K/Na of at least 1:2, preferably from 1:1 to
45:1, especially from 1:1 to 3:1, more preferably from 1.05:1
to 3:1, such as 1.5:1, or 2:1. When the K/Na ratio is le~s
than 1 there is less solubility of the normally solid
ingredient~ making a less transcluent composition with
acceptable cleaning per~ormance whereas when the K/Na ratio i9
more than 45, e~pecially when it is greater than 3, the
product becomes koo liquid and phase sepaxation begins to
occur. ~hen the K/Na ratio i~ more than 45, e~pecially when
it is greater than 3, the product becomes too liquid and
phase separation begin~ to occur. When the K/Na ratios become
much larger than 45, such as in all or mostly potassium
formulation, the polymer thickener loses its absorptlon
capacity and begins to salt out of the aqueous phase.
,
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2 ~
The potassium and sodium ions can be made present in the
compositions as the alkali metal cation of the detergent
builder salt(s), or alkali metal silicate or alkali metal
hydroxide components of the compositions. The alkali metal
cation may also be present in the com~ositions as a component
of an ionic detergent, bleach or other ionizable salt compound
additive, e.g. alkali metal carbonate. In determining the
K/Na weight ratios all of these sources should be taken into
consideration.
Specific examples of detergent builder salts include the
polyphosphates, such as alkali metal pyrophosphate, alkali
metal tripolyphosphate, alkali metal metaphosphate, and the
like, for example, sodium or potassium tripolyphosphate
(hydrated or anhydrous), tetrasodium or tetrapotassium
pyrophosphate, sodium or potassium hexa-metaphosphate,
trisodium or tripotassium orthophosphate and the like, sodium
or potassium carbonate, sodillm or potas~ium citrate, sodium or
potassium nitrilotriacetate, and the like. The phosphate
builders, where not precluded due to local regulations, are
preferred and mixtures of tetrapotassium pyropho~phate (TKPP)
and sodium tripolyphosphate (NaTPP) (especially the
hexahydrate) are especially preferred. Typical ratios of
NaTPP to TKPP are from 2:1 to 1:8, especially from 1:1.1 to
1:6. The total amount of detergent builder salts is
preferably from 5 to 35~ by weight, more preferably from 15
to 35~, especially from 18 to 30~ by weight of the
composition.
.
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In connection with the builder salts are optionally used
a low molecular weight noncrosslinked polyacrylates having a
molecular weight of 1,000 to 100,000, more preferably 2,000
to 80,000. A preferred low molecular weight polyacrylate is
Norasol LMW45ND manufactured by Norsoshaas and having a
molecular weight o~ 4,500. These low molecular weight
polyacrylates are employed at a concentration of 0 to 15
wt.~, more preferably 0.1 to 10 wt.%.
Other useful low molecular weight noncrosslinked polymers
are Acusol~640D provi~ed by Rohm & Haas; Norasol QR1014 from
Norsohaas having a GPC molecular weight of 10,000.
The linear viscoelastic compositions of this inventlon
may, and preferably will, contain a small, but stabilizing
e~fective amount of a long chain fa~y acid or monovalent or
polyvalent salt thereof. Although the manner by which the
fatty acid or salt contributes to the rheology and stability
of the composition has not been fully elucidated it is
hypothesized tha~ it may function as a hydrogen bonding agent
or cross-linking agent for the polymeric thickener.
The preferred long chain fatty acids are the higher
aliphatic fatty acids having from 8 to 22 carbon atoms, more
preferably from 10 to 20 carbon atoms, and especially
preferably from 12 to 18 carbon atoms, and especially
preferably from 12 to 18 carbon atoms, inclusive of the
carbon atom of the carboxyl group of the fa~ty acid. The
aliphatic radical may be saturated or unsaturated and may be
straight or branched. Straight chain saturated fatty acids
are preferred. Mixtures of fatty acids may be used, such as
14
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8 ~ ~
those derived from natural sources, such as tallow fatty acid,
coco fatty acid, soya fatty acid, mixtures of these acids,
etc. Stearic acid and mixed fatty acids, e.g. stearic
acid/palmitic acid, are preferred.
When the free acid form of the fatty acid is used
directly it will generally associate with the potassium and
sodium ions in the aqueous phase to form the corresponding
alkali metal fatty acid soap. However, the fatty acid salts
may be directly added to the composition as sodium salt or
potassium salt, or as a polyvalent metal salt, although the
alkali metal salts of the fatty acids are preferred fatty acid
salts.
The preferred polyvalent metals are the di- and tri-
valent metals of Groups IIA, IIB and IIIB, such as magn~sium,
calcium, aluminum and zinc, although other polyvalent metals,
including those of Groups IIIA, I~A, VA IB, IVB, VB, VIB VIIB
and VIII of the Periodic Table of the Elements can also be
used. Specific examples of such other pol~valent metals
include Ti, Zr, V, Nb, Mn, Fe, Co, Ni, Cd, Sn, Sb, ~i, etc.
Generally, the metals may be present in the divalent to
pentavalent state. Preferably the metal sal~s are used in
their higher oxidation states. Naturally, for use in
automatic dishwashers, as well as any other applications where
the invention composition will or may come in contact with
articles used for the handling, storage or serving of food
products or which otherwise may come into contact with or be
consumed by people or animals, the metal salt should be
selected by tak~ng into consideration the toxicity o~ the
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2 ~ 6 .~
metal. For this purpose, the alkali metal and calcium an~
magnesium salts are especially higher preferred as generally
safe food additives.
The amount of the fatty acid or fatty acid salt
stabilizer to achie~e the desired enhancement of physical
stability will depend on such factors as the nature of the
fatty acid or its salt, the nature and amount of the
thickening agent, detergent active compound, inorganic salts,
other ingredients, a~ well as the anticipated storage and
shipping conditions.
Generally, however, amounts of the fatty acid or fatty
acid salt stabilizing agents in the range of from 0 to 2.0~,
preferably 0.005 ~o 2.0~, more preferably from 0.01 to ~.0%,
provide a long term stability and absence of phase separation
15 upon standing or during transport at both low and elevated
temperatures as are required for a commercially acceptable
product.
Depending on the amounts, proportions and types of fatty
acid physical stabilizers and polyacrylic acid-type thickening
agents, the addition of the fatty acid or salt not only
increases physical stability but also provides a 3imultaneous
increase in apparent viscosity. Amounts o~ fatty acid or salt
to polymeric thickening agent in the range of from 0.005-0.4
weight percent fatty acid salt and from 0.4~1.75 weight
percent polymeric thickening agent are usually sufficient to
provide these simultaneous benefits and, therefore, the use of
these ingredients in these amounts is most preferred.
16
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In order to achieve the desired benefit from the fatty
acid or fatty acid salt stabilizer, without stabilization of
excess incorporated air bubbles and consequent excessive
lowering of the product bulk density, the fatty acid or salt
should be post-added to the formulation, preferably together
with the other surface active ingredients, including detergent
active compound and anti-foaming agent, when present. These
surface active ingredients are preferably added as an emulsion
in water wherein the emulsified oily or fatty materials are
finely and homogeneously dispersed throughout the aqueous
phase. To achieve the desired fine emulsification of the
fatty acid or fa~ty acid salt and other surface active
ingredients, it is usually necessary to heat the emulsion (or
preheat the water) to an elevated temperature near the melting
temperature of the fatty acid or its salt. For example, for
stearic acid having a melting point of 6~C-6~C, a temperature
in the range of between 50C and 70C will be used. For lauric
acid (m.p.=47C~ an elevated temperature of 35C to 50C can be
used. Apparently, at these elevated temperatures the fatty
acid or salt and other surface active ingredients can be more
readily and uniformly disperged (emulsified) in the form of
fine droplets throughout the composition.
In contrast, as will be shown in the examples which
follow, if the fatty acid is simply post-added at ambient
temperature, the composition is not linear viscoelastic as
defined above and the stability of the composition is clearly
inferior~
2~3~
Foam inhibition is important to increase dishwasher
machine efficiency and minimize destabilizing effects which
might occur due to the presence of excess foam within the
washer during use. Foam may be reduce by suitable selection
of the type and/or amount of detergent active material, the
main foam-producing component. The degree of foam is also
somewhat dependent on the hardness of the wash water in the
machine whereby suitable adjustment of the proportions of the
builder salts such as NaTPP which has a water softening
effect, may aid in providing a degree of foam inhibition.
However, it is generally preferred to include a chlorine
bleach stable foam depressant or inhibitor. Particularly
effective are the alkyl phosphoric acid esters of the formula
E~ll
OR
and especially the alkyl acid phosphate esters of the formula
HO-P-OR --
OR
In the above formulas, one or both R groups in each type of
ester may represent independently a C~2-C20 alkyl or ethoxylated
alkyl group. The ethoxylated derivatives of each type of
ester, for example, the condensation products of one mole of
ester with from 1 to 10 moles, preferably 2 to 6 moles, more
preferably 3 or 4 moles, ethylene oxide can also be used.
Some examples of the foregoing are commercially available,
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2~98~6
such as the products SAP from Hooker and LPKN-158 from
Knapsack. Mixtures of the two types, or any other chlorine
bleach stable types, or mixtures of mono- and di-esters of the
same type, may be employed. Especially preferred is a mixture
of mono- and di-C,6-CI8 alkyl acid phosphate esters such as
monostearyl/distearyl acid phosphates 1.2/1, and the 3 to 4
mole ethylene oxide condensates thereof. When employed,
proportions of 0.05 to 1.5 weight percent, preferably 0.1 to
0.5 weight percent, of foam depressant in the composition is
typical, the weight ratio of detergent active component (d) to
foam depressant (e) generally ranging from 10:1 to 1:1 and
preferably 5:1 to 1:1. Other defoamers which may be used
include, for example, the known silicones, such as available
from Dow Chemicals. In addition, it i9 an ad~antageous
feature of this invention that many of the stabilizing salts,
such as the stearate salts, for example, aluminum stearate,
when included, are also effective a~ foam killers.
Although any chlorine bleach compound may be employed in
the compositions of thi~ in~ention, such as dichloro-
isocyanurate, dichloro-dimethyl hydantoin, or chlorinated TSP,
alkali metal or alkaline earth metal, e.g. potassium, lithium,
magnesium and especially sodium, hypochlorite is preferred.
The composition should contain sufficient amount of chlorine
bleach-compound to provide 0.2 to 4.0% by weight of available
chlorine, as determined, for example by acidification of 100
parts of the composition with excess hydrochloric acid. A
; solution containing 0.2 to 4.0% by weight of sodium
~ hypochlorite contains or provides roughly the same percentage
19
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o~ available chlorine. 0.8 to 1.6~ by weight of available
chlorine is especially preferred. For example, sodium
hypochlorite (NaOCL) solution of from 11 to 13% available
chlorine in amounts of 3 to 20%, preferably 7 to 12%, can be
advantageously used.
Detergent active material useful herein should be stable
in the presence of chlorine bleach, especially hypochlorite
bleach, and for this purpose those of the organic anionlc,
amine oxide, phosphine oxide, sulphoxide or betaine water
dispersible surfactant types are preferred, the first
mentioned anionics being most pre~erred. Particularly
preferred surfactants herein are the linear or branched alkali
metal mono- and/or di-(C8-C~4) alkyl diphenyl oxide mono- and/or
di-sulphates, commercially available for example as DOWFAX
(registered trademark) 3B-2 and DOWFAX 2A-l. In addition, the
; surfactant should be compatible with the other ingredients of
the composition. Other suitable organic anionic, non-soap
surfactants include the primary alkylsulphates,
alkylsulphonates, alkylarylsulphonates and sec.-
alkylsulphates. Examples include sodium Cl0-Cl8 alkylsulphates
; such as sodium dodecylsulphate and sodium tallow
alcoholsulphate; sodium Cl0-Cl8 alkanesulphonates such as sodium
h~xadecyl-l-sulphonate and sodium Cl2-Cl8
alkylbenzenesulphonates such as sodium
dodecylbenzenesylphonates. The corresponding potassium salts
may also be employed.
As other suitable sur~actantg or detergents, the amine
oxide surfactants are typically of the structure R2RINO, in
. .
. . .
.' . ~
- , , ' , ~
2~8~1 fi
which each R represents a lower alkyl group, for instance,
methyl, and Rl represents a long chain alkyl group having from
8 to 22 carbon atoms, Eor instance a lauryl, myristyl,
palmityl or cetyl group. Instead of an amine oxide, a
corresponding surfactant phosphine oxide R2RIPO or sulphoxide
RRISO can be employed. Betaine surfactants are typically of
the structure R2RIN+R''COO-, in which each R represents a lower
alkylene group having from 1 to 5 carbon atomsO Specific
examples of these surfactants include lauryl-dimethylamine
oxide, myristyl-dimethylamine oxide, myristyl-dimethylamine
oxide, the corresponding phosphine oxides and sulpho~ide~, and
the corresponding betaines, including dodecyldimethylammonium
acetate, tetradecyldiethylammonium pentanoate,
hexadecyldimethylammonium hexanoate and the like. For
biodegradability, the alkyl groups in these surfactants should
be linear, and such compounds are preferred.
Surfactants of the foregoing type, all well known in the
art, are de~cribed, for example, in U.S. Patents 3,985,668 and
4,271,030. If chlorine bleach is not used than any of the
well known low-foaming nonionic surfactants such as
alkoxylated fatty alcohols, e.g. mixed ethylene oxide-
propylene oxide condensates of C8-C22 fatty alcohol~ can also be
used.
The chlorine bleach s~able, water dispersible organic
detergent-active material (surfactant) will normally be
present in the composition in minor amounts, generally 1~ by
weight of the composition in minor amount~, generally 1~ by
weight of the composition, although smaller or laxger amounts,
21
,
'
' , '
2~84~
such as up to 5%, such as from 0.1 to 5~, preferably form 0.3
or 0.4 to 2% by weight of the composition, may be used.
Alkali metal (e.g. potassium or sodium) silicate, which
provides alkalinity and protection of hard surfaces, such as
fine china glaze and pattern, is generally employed in an
amount ranging from 0 to 25 weight percent, preferably 5 to
15 ~eight percent, more preferably 8 to 12% in the
composition. The sodium or potassium silicate is generally
added ln the form of an aqueous solution, preferably having
Na2O:SiO2 or K20:SiO2 ratio of 1:1.3 to 1:2.8, especially
preferably 1:2~0 to 1:2.6. At this point, it should be
mentioned that many of the other component~ of this
composition, especially alkali metal hydroxide a~d bleach, are
also often added in the form of a preliminary prepared aqueous
dispersion or solution.
: In addition to the detergent active surfactant, foam
inhibitor, alkali metal silicate corrosion inhibitor, and
detergent builder salts, which all contrihute to the cleaning
performance, it is also known that the ef~ectivenes~ of the
liquid automatic dishwasher detergent compositions is related
to the alkalinity, and particularly to moderate to high
alkalinity levels. ~ccoxdingly, the compositions of this
invention will have p~ values of at least 9.5, preferably at
least 11 to as high as 14, generally up to 13 or more, and,
when added to the aqueous wash bath at a typical concentration
level of 10 grams per liter, will provide a pH in the wash
bath of at least 9, preferably at least 10, such as 10.5,
11, 11.5 or 12 or more.
22
:
'.
. " '' "' .. ` '',
. ': . ' ' " '
.. . . .
The alkalinity will be achieved, in part by the alkali
metal ions contributed by the alkali metal detergent builder
salts, e.g. sodium tripolyphosphate, tetrapotassium
pyrophosphate, and alkali metal silicate, however, it is
usually necessary to include alkali metal hydroxide, e.g. NaOH
or KOH, to achieve the desired high alkalinity. Amounts of
alkali metal hydroxide in the range of (on an active basis) of
from 0.5 to 8~, preferably ~rom 1 to 6~, more preferably from
1.2 to 4%, by weight of the composition will be sufficient to
achieve the desired pH level and/or to adjust the K/Na weight
ratio.
OthPr alkali metal salts, such as alkali metal carbonate
may also be present in the compositions in minor amounts, for
example from 0 to 4~, preferably 0 to 2~, by weight of the
composition.
Other conventional ingredients may be included in these
compositions in small amounts, generally less than 3 weight
percent, such as perfume, hydrotropic agents such as the
sodium benzene, toluene, xylene and cumene sulphonates,
preservatives, dyestuffs and pigments and the like, all of
course being stable to chlorine bleach compound and high
alkalinity. Especially preferred for coloring are the
chlorinated phythalocyanines and polysuphides of
aluminosilicate which provide, respectively, pleasing gr~en
and blue tints. TiO2 may be employed for whitening or
neutralizing off-shades.
Although for the reasons previously di~cussed excessive
air bubbles are not often desirable in the invention
23
.
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, ,, ,- .. : ,. . .
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.
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compositions, depending on the amounts of dissolved solids and
liquid phase densities, incorporation of small amounts of
finely divided air bubbles, generally up to 10% by volume,
preferably up to 4~ by volume, more preferably up to 2% by
volume, can be incorporated to adjust the bulk density to
approximate liquid phase density. The incorporated air
bubbles should be finely divided, such as up to 100 microns
in diameter, preferably ~rom 20 to 40 microns in diameter,
to assure maximum stability. Although air is the preferred
gaseous medium for adjusting densities to improve physical
stability of the composition other inert gases can also be
used, such as nitrogen, carbon dioxide, helium, oxygen, etc.
The amount of water contained in these compositions
should, of course, be neither so high as to produ~e unduly low
viscosity and fluidity, nor so low as to produce unduly high
viscosity and low flowability, linear viscoelastic properties
in either case being diminished or destroyed by increasing tan
1. Such amount is readily determined by routine
experimentation in any particular instance, generally ranging
from 30 to 75 weight percent, preferably 35 to 65 weight
percent. The water should al90 be preferably deionized or
softened.
The manner of formulating the invention compositions is
also important. ~s discussed above, the order of mixing the
~5 ingredients as well as the manner in which the mixing is
performed will generally ha~e a significant ef~ect on the
properties of the composition, and in particular on product
density ~by incorporation and stabilization of moxe or less
Z4
- '
. ' : ,
206~6
air) and physical stability (e.g. phase separation). Thus,
according to the preferred practice of this invention the
compositions are prepared by first forming a dispersion of the
polyacrylic acid-type thickener in water under moderate to
high shear conditions, neutralizing the dissolved polymer to
cause gelation, and then introducing, while continuing mixing,
the detergent builder salts, alkali metal silicate~, chlorine
bleach compound and remaining detergent additives, including
any previously unused alkali metal hydroxide, if any, other
than the surface-active compounds. All of the additional
ingredients can be added simultaneously or sequentially.
Preferably, the ingredientg are added sequentially, although
it is not necessary to complete ~he addition of one ingredient
before beginning to add the next ingredient. Furthermore, one
or more of the3e ingredients can be divided into portions and
added at different times. These mixing steps should also be
performed under modera~e to high shear rates to achieve
complete and uniform mixing. The~e mixing steps may be
carried out at room temperature, although the polymer
thickener neutralization (gelation) is usually exothermic.
The composition may be allowed to age, if necessary, to cause
dissolved or dispersed air to dissipate out of the
composition.
The remaining surface active ingredients, including the
anti-foaming agent, organic detergent compound, and fatty acid
or fatty acid salt stabilizer is post-added to the previously
formed mixture in the form of an aqueous emulsion (using from
1 to 10~, preferably from 2 to 4~ o~ the total water added to
' . ' ' - - :
,
- ,. . .
- . : . : - ..
- -. : . ,
.
2~6~
the composition other than water added as carrier for other
ingredients or water of hydration) which is pre-heated to a
temperature in the range of from Tm~5 to Tm-20, preferably
from Tm to TM-10, where Tm is the melting point temperature
of the fatty acid or fatty acid salt. For the preferred
stearic acid stabilizer the heating temperature is in the
range of 50C to 70C. However, i care is taken to avoid
excessive air bubhle incorporation during the gelatin step or
during the mixing of the detergent builder salts and other
additives, for example, by operating under vacuum, or using
low shearing conditions, or special mixing operatatus, etc.,
the order of addition of the surface active ingredients should
be less important.
In accordance wi~h an especially preferred embodiment,
the thickened linear viscoelastic a~ueous automatic dishwasher
detergent composition of this invention includes, on a weight
basis:
(a) 10 to 35%, preferably 15 to 30%, alkali metal
detergent builder salt;
(b) 0 to 25, preferably 15 to 15%, alkali metal
3ilicate;
(c) 0 to 6~, preferably 1 to 6%, alkali metal hydroxide;
(d) 0 to 5~, preferably 0.1 to 3%, chlorine bleach
stable, water-dispersible, low-foaming organic detergent
active material, preferably non-soap anionic detergent;
(e) 0 to 1.5~, preferably 0.1 to 1.5~, chlorine bleach
stable foam depressant;
26
~98~ b~
(f) chlorine bleach compound in an amount to provide
0.2 to 4~, preferably 0.8 to 1.6~, of available chlorine;
(g) at least one high molecular weight hydrophilic
cross-linked polyacrylic acid thickening agent in an amount to
provide a linear viscoelasticity to the formulation,
preferably from 0.1 to 2.0~ more preferably from 0.2 to
1.75~;
(h) a long chain fatty acid or a metal salt of a long
chain fatty acid in an amount effective to increase the
physical stability of the compositions, preferably from 0 to
2.0~, more preferably from 0.005 to 2.0%; and
(i) balance water, preferably from 30 to 75~, more
preferably from 35 to 65~; and wherein in (a) the alkali
metal polyphosphate includes a mixture of from 5 to 30%,
preferably from 12 to 22% of tetrapotassium pyrophosphate,
and from 0 to 20~, preferably from 3 to 18~ of sodium
tripolyphosphate, and wherein in the entire composition the
ratio, by weight, of potassium ions to sodium ion~ i~ from
1/2 to 3/l, preferably from 1.0/1 to 2.5/1, the compositions
having an amount of air incorporated therein such that the
bulk density of the composition is from 1.26 to 1.42 g/cc,
preferably from 1.32 to 1.40 g/cc.
The compositions will be supplied to the consumer in
suitable dispenser containers preferably formed of molded
plastic, especially polyolefin plastic, and most preferably
polyethylene, for which the invention compositions appear to
have particularly favorable slip characteristics. In addition
to their linear viscoelastic character, the compositions of
- :
.
' .' ' :
2 ~
this invention may also be characterized as pseudoplastic gels
(non-thixotropic) which are typically near the borderline
between liquid and solid viscoelastic gel, depending, for
example, on the amount of the polymeric thickener. The
invention compositions can be readily poured from their
containers without any shaking or squeezing, although
squeezable containers are often convenient and accepted by the
consumer for gel-like products.
The liquid aqueous linear viscoelastic automatic
dishwasher compositions o~ this invention are readily employed
in known manner for washing dishes, other kitchen utensils and
the like in an automatic dishwasher, provided with a suitable
detergent dispenser, in an aqueous wash bath containing an `
effective amount of the composition, generally sufficient to
fill or partially fill the automatic dispenser cup of the
particular machine being used.
The invention alRo provides a method for cleaning
dishware in an automatic dishwashing machine with an aqueou~
wash bath containing an effective amount of the liquid linear
viscoelastic automatic dishwasher detergent compo9ition as
described above. The composition can be readily poured ~rom
the polyethylene container with little or no s~ueezing or
shaking into the dispensing cup of the automatic dishwashing
machine and will be ~ufficiently viscous and cohesive to
remain securely within the di~pensing cup until shear forces
are again applied thereto, such as by the water ~pray from the
dishwashing machine.
28
.
20~8~
The invention may be put into practice in various ways
and a number of specific embodiments will be described to
illustrate the invention with reference to the accompanying
examples.
All the amounts and proportions referred to herein are by
weight of the composition unless otherwise indicated.
29
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Formulations A, B, C, D, E, G, J, and K are prepared2 ~ ~ 9 8 ~ 6
_irst forming a uni~orm dispersion of the Carbopol 941 or 940
thickener in 97~ of the water (balance). The Carbopol is
slowly added to deionized water at room temperature using a
mixer equipped with a premier blade, with agitation set at a
medium shear rate, as recommended by the manufacturer. The
dispersion is then neutralized by addition, under mixing, of
the caustic soda (50% NaOH or KOH) component to form a
thickened product of gel-like consistency.
To the resulting gelled dispersion the silicate,
tetrapotassium pyrophosphate (TKPP), sodium tripolyphosphate
TP(TPP, Na) and bleach, are added sequentially, in the order
~tated, with the mixing continued at medium shear.
Separately, an emulsion of the phosphate anti-foaming
lS agent (LPKN), stearic acid/palmitic acid mixture and detergent
(Dowfax 3B2) is prepared by adding these ingredients to the
remaining 3~ of water (balance) and heating the resulting
mixture to a temperature in the range of 50C to 70C.
This heated emulsion is then added to the previously
prepared gelled dispersion under low shear condition9, such
that a vor~ex is not formed.
The remaining formulation~ F, H and I are prepared in
essentially the same manner as described above except that the
heated emulsion of LPKN, stearic acid and Dowfax 3B2 is
directly added to the neutralized Carbopol dispersion prior to
the addition of the remaining ingredients. As a re~ult,
formulations F, H and I, have higher levels of incorporated
air and densitie~ below 1.30 g/cc.
The rheograms for the formulations A, C, D, G and ~ are
shown in figures 1-5, respecti~ely, and rheograms for
.
.
2 0 ~
formulations H, I and K are shown ln figures 6, 7 and 8
espectively.
These rheograms are obtained with the System 4 Rheometer
from Rheometrics equipped with a Fluid Servo with a 100 grams-
centimeter torque transducer and a 50 millimeter parallel
plate geometry having an 0.~ millimeter gap between plates.
All measurements are made at room temperature ~25C+1C) in a
humidity chamber after a 5 minute or 10 minute holding period
of the sample in the gap. The measurements are made by
applying a frequency of 10 radians per second.
All of the composition formulations A, B, C, D, G and J
according to the preferred embodiment of the invention which
include Carbopol 941 and stearic acid exhibit linear
viscoelasticity as seen from the rheograms of figure 1^5.
Formulatio~ E which includes Carbopol 941 but not stearic acid
showed no phase separation at either room temperature or 100F
after 3 weeks, but exhibited 10% phase separation after 8
weeks at room temperature and after only 6 weeks at 100F.
Formulation K, containing Carbopol 940 in place of
Carbopol 941, as seen from the rheogram in figure 8, exhibits
substantial linearity over the strain range of from 2~ to 50%
(G' at 1~ strain-GI at 50% strain 500 dynes/sq.cm.) although
tan 1 at a strain above 50~.
,
2~98~
Example 2
This example demonstrates the importance of the order of
addition of the surface active component premix to the
remainder of the composition on product density and stability.
The following formulations are prepared by methods A and
B:
Ingredient
Water, deionized Balance
Carbopol 941 0.5
NaO~ (50~) 2.4
Na Silicate (47.5~) 21
TKPP 15
TPP, Na 13
Bleach (1%) 7.5
LPKN 0.16
Stearic Acid 0.1
Dowfax 3B2
Method A:
The Carbopol 941 is dispersed, under medium shear rate,
using a premier blade mixer, in deionized water at ambient
temperature. The NaOH i~ added, under mixing, to neutralize
and gel the Carbopol 941 dispersion. To the thickened mixture
the following ingredients are added ~equentially while the
stirring i9 continued: sodium silicate, TKPP, TPP, and
bleach.
Separately, an emulsion is prepared by-adding the Dowfax
3B2, stearic acid and LPKN to water while mixing at moderate
shear and heating the mixture to 65C to finely disperse the
emulsified surface active inyredients in the water phase.
This emul~ion premix is then slowly added to the Carbopol
dispersion while mixing under low shear conditions without
forming a vortex. The results are shown below.
Method B:
Method A is repeated except that the heated emulsion
premix is added to the neutralized Carbopol 941 di~persion
34
.
2~6~8~
before the sodium stearate, TKPP, TPP, and bleach. The
esults are also shown below.
Method A Method B
Density (g/cc) 1.38 1.30
Stability (RT-8 weeks) 0.00~ 7.00~
Rheogram Fig. 9 Fig.10
From the rheograms of figures 9 and 10 it is seen that
both products are linear viscoelastic although the elastic and
viscous moduli G~ and G~ are higher for Method A than for
Method B.
From the results it is seen that early addition of the
surface active ingredients ~o the Carbopol gel significantly
increases the degree of aeration and lowers the bulk density
of the final product. Since the bulk density is lower than
the density of the continuous liquid phase, the liquid phase
undergoes inverse separation (a clear liquid phase forms on
the bottom of the composition). This process of inverse
separation appears to be kinetically controlled and will occur
faster as the density of the product becomes lower.
Example 3
This example shows the importance of the temperature at
which the premixed surfactant emulsion i~ prepared.
~5 Two formulations, L and M, ha~ing the same composition as
in Example 2 except that the amount of stearic acid was
increased from 0.1~ to 0.2~ are prepared ag shown in Method A
for formulation L and by the following Method C for
formulation M.
Method C
The procedure of Method A is repeated in all details
except that emulsion premix of the surface active ingredients
.
,,
. .
,
.
., - . . ~ . .
~06t~846
is prepared at room temperature and is not heated before being
~ost-added to the thickened Carbopol dispersion containing
silicate, builders and bleach. The rheogram~ for formulations
L and M are shown in figures 11 and 12, respectively. From
these rheograms it is geen that ~ormulation L is linear
viscoelastic in both G~ and G~ whereas formulation M is non-
linear viscoelastic particularly for elastic modulus G~ (G~ at
1% strain-G' at 30~ strain > 500 dynes/cm2) and also for G" (G"
at 1~ strain-G" at 30% strain ~ 300 dynes/cm2).
Formulation L remains stable after storage at RT and 100F
for at least 6 weeks whereas formulation M undergoes phase
separation.
Comparative Example 1
The following formulation is prepared without any
potassium salts:
Weight
Water Balance
Carbopol 941 0.2
NaOH (50%) 2.4
TPP, Na (50%) 21~0
Na Silicate (47.5~) 17.24
Bleach (1%) 7.13
Stearic Acid 0.1
LPKN (5%) 3.2
Dowfax 3B2 0.8
Soda Ash 5.0
Acrysol LMW 45-N 2.0
The procedure used is analogou~ to Method A of Example 2
with the soda ash and Acrysol LMW 45-N (low molecular weight
polyacrylate polymer) being added before and after,
respectively, the silicate, TPP and bleach, to the thickened
Carbopol 941 dispersion, followed by addition to the heated
surface active emul~ion premix. The rheogr~m is shown in
figure 13 and is non-linear with G"/G' (tan ~) ~ 1 over the
range of strain of from 5% to 80%.
36
, ~
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Example 4
Formulations A, B, C, D and K according to this invention
and comparative formulations F and a commercial liquid
automatic dishwasher detergent product as shown in Table 1
above were subjected to a bottle residue test using a standard
polyethylene 28 ounce bottle as used for current commercial
liquid dishwasher detergent bottle.
Six bottles are filled with the respective samples and
the product is dispensed, with a minimum of ~orce, ~n 80 gram
dosages, with a 2 minute rest period between dosages, until
flow stops. At this point, the bottle was vigorously shaken
to try to expel additional product.
The amount of product remaining in the bottle is measured
as a percentage of the total product originally filled in ~he
bottle. The results are shown below.
Bottle Residue
Formulation Residue
A R
B 10
C 6
D 5
K 7
F*
Commercial Product 20
*The sample separates upon aging
37
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~ In O O O Uol ~ o a~)
~1 r~ O ~ ~ ~1 C0 ~1 Il') N 10 t` ~'f) N
a~ O O ~iN N O O N r~r l t~ r~l ~i ~1 ~1)
Q. _ _ __ _ _ _ _ _ _ o
h Ll~ o o o In o o g
1~ In d' ~ ~ ) . . . m . r~ ~ S~
. . . .. . ~1 Ll) N .t` . N
m O O N NO O ~ _ ~J ~J
111 O ~
. I r~ ~ N ~1 a:) O O N Il ) 1~ O ~1 ~Q
O O N ~O O N ~1 ~ r~ t~ ~1 ~
~ ~--o~--~ ~ ------~ ~ ~ ~ --~
~ E~ ~ :~
~;z; E~ ~ H ~ O
w I ~0 lo ~ ¦u~ ~
x ~ m ~ o x w s H ~ ~ HO H O~o tY ~ V H O
~ V ~ P~ E~ O O ~ O ~ O ~ O ~1 ~ H H1:~1
V '¢ ~ 1 l u~ 1~ Cq-- ~ P~ U~ E~ u~-- ~ ~1: V ~ ~1
r ~3 _ ~ _ i ~ _ _ _ _ ~ _ ~ ~ m
~ , ~ . .
.
- ,.: - :
,
-
Example 6 2069~fi
The following Eormulas A and B were prepared according to the
procedure of Example 1.
Carb~pol 614 oA.9 0.9
_
NaOH (50~) 4.5 4.5
Sodium Tripolyphosphate 5.26 5.26
Potassium Tripolyphosphate 20.35 20.35
Sodium Silicate (47.5%) (1:2.3) 20.83 20.83
LPRn-158 0.16 0.16
15 Dowfax 3B2 0.8 0.8
Stearic Acid 0.005 0.01
NaOC1 (13.0~ C1) 10.13 10.13
Air Vol~ ~2 _ _
Water balance b~l~nce
I _ _ 2480 2420
I ~ _ - __ _
Brookfield viscosity at room temperature at #4 spindle at 20 rpms after
24 hours.
: 39
