Note: Descriptions are shown in the official language in which they were submitted.
LOW-FOAMING NONIONIC SURFACTANT FO~
MACHINE DISHWASHING DETERGENT
Back~round of th _ nVentloD
1. Field of the Invention
This invention relates to machine dishwashing
detergent compositions and related processes.
- 2 Descri tion of the Prior Art
P
In the art of cleaning compositions for use in
cleaning hard surfaces, particularly the art of cleaning
tableware and other ood-soiled utensils in machine dish-
washers, the problem of excessive foam buildup in the machineduring operation as the result of high food soil concentra-
tions has been largely solved by the use of alkyl phosphate
ester defoamers such as monostearyl acid phosphate as dis-
closed in U. S. 3,314,891. Prior to such disclosure, machine
dishwashing compositions had the tendency to foam excessively
and/or leave undesirable spots and streaks on dishes and
glassware. The low foaming nonionic surfactants containèd in
such detergent compositions were ineffective in both removing
food soil and providing suitable foam control where the
aqueous cleaning solution became contaminated with foam
generating protein soils such as egg soil and soil from
; various milk products.
The generation of such foams is particularly
~; insidious in that the cleaning action of the machine dish-
washer depends to a large extent upon the effective suppres-
sion of foam generation during operation. Without ef~ective
~ foam suppression, ~he mechanical cleaning action of the
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.. . .
r
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. ` . .
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machine dishwasher is reduced as the result of foam buildup in
the aqueous cleaning solution so that the aqueous washing
fluid which is normally impelled against the tableware in the
machine dishwasher is less effective in cleaning because it is
forced against the tableware at reduced pressure.
An indication of the various kinds of nonionic
surfactants utilized in such machine dishwashing compositions
can be found in the above patent and in U.S. 3,359,207.
General disclosures of nonionic surfactants can be found in
U.S. 2,677,700, U. S. 2,979,528, and U. S~ 3~036,118. Low
foaming washing and cleaning agents for use in machine dish-
washing are also disclosed in U. S. 3,382,176. More recently,
machine dishwashing detergent compositions based upon a
non-phosphate salt builder have been disclosed in British
1,325,645; Canadian 941,707; U~S. 3,899,436; U.S. 4,127,496;
and U.S. 4,092,258.
Recently a new series of nonionic surfactants has
been disclosed, certain members of which possess relatively
low cloud points as measured in a one percent aqueous solution.
Such surfactants are suggested for use in the formulation of
machine dishwashing detergents and generally for use where a
defoamer is necessary. These new nonionic surfactants are
termed TETRONIC~ R polyols and are produced by the sequential
block polymerization of ethylene oxide and propylene oxide
utilizing, as polymerization initiator, a propoxylated
ethylenediamine sold under the trademark QUADROL~ The
-
36
TETRONIC~ R polyols were introduced to the trade in September,
1978.
In no one of the above prior art references is there
disclosed the use of a novel homogeneous blend of a conven-
tional low foaming nonionic surfactant and a second nonionic
surfactant wherein said second surfactant is characterized by
a relatively low cloud point, i.e., about 10C to about 20C
in a 1 percent aqueous solution. Said blend is useful in
formulating machine dishwashing detergents which are capable
of effectively controlling foaming during dishwasher operation
caused by protein soil contamination.
_ummary of the Invention
Novel low foaming nonionic surfactants are dis-
closed which are useful in formulating machine dishwashing
`` detergents. The use of a novel homogeneous blend of sur-
factants permits the elimination of the conventionally used
alkyl phosphate ester, the prior art defoamer component of
conventional machine dishwashing detergents which is im-
miscible with most conventional low-foaming nonionic sur-
factants~ The machine dishwashing detergents of the invention
are useful when formulated with phosphate or non-phosphate
builders and other conventional adjuvants utilized in the
` formulation of machine dishwashing detergentsO Because of
the relatively low cloud point of one of the components of
the nonionic surfactant blend, the machine dishwashing deter-
gents of the invention can be utilized over a wide range of
operating conditions. Wash water temperatures as low as 100~F
~ -3-
:'
.
~ 3~
and as high as 180F and detergent concentrations o~ 0.2 to
about 1 percent by weight can be utilized.
Description of the Preferred Embodiments
The novel nonionic surfactant blend of the invention
useful in the preparation of machine dishwashing detergents of
the invention contains a homogeneous mixture of nonionic
surfactants comprising at least one conventional nonionic
surfactant possessing low fo~ming characteristics and a second
nonionic surfactant characterized by relatively low cloud
point and a total molecular weight generally of about 500 to
about 25,000. The proportion of surfactants in said blend is
about 10 to about 90 percent by weight of each of the sur-
factants, preferably about 25 to about 75 percent by weight of
each of the surfactants.
The Conventional Nonionic Surfactant
! The conventional nonionic surface active agents
which are advantageously employed in the nonionic surfactant
blends and machine dishwashing detergent compositions of the
invention can be the polyoxyalkylene adducts of hydrophobic
bases wherein the oxygen/carbon atom ratio in the oxyalkylene
portion of the molecule is greater than 0.40. Those composi-
tions which are condensed with hydrophobic bases to provide
a polyoxyalkylene portion having an oxygen/carbon atom ratio
greater than 0.40 include ethylene oxide, butadiene dioxide
and glycidol, mixtures of these alkylene oxides with ea~h
o~her and with minor amounts of propylene oxide, butylene
oxide, amylene oxide, styrene oxide, ~nd other higher molecular
weight alkylene oxides. Ethylene oxide, for example, is
condensed with the hydrophobic base in an amount sufficient to
impart water dispersibility or solubility and surface active
properties to the molecule being preparedO The exact amount
of ethylene oxide condensed with the hydrophobic base will
depend upon the chemical characteristics of the base employed
and is readily apparent to those of ordinary skill in the
art relating to the synthesis of oxyalkylene surfactant
condensates.
Typical hydrophobic bases which can be condensed
with ethylene oxide in order to prepare nonionic surface
active agents include mono- and polyalkyl phenols, polyoxy-
propylene condensed with a base having from about 1 to 6
carbon atoms and at least one reactive hydrogen atom, fatty
acids, fatty amines, fatty amides and fatty alcohols.
The hydrocarbon ethers such as the benzyl or lower alkyl
ether of the polyoxyethylene surfactant condensates are also
advantageously employed in the compositions of the invention.
Among the suitable nonionic surfactants are the
polyoxyethylene condensates of alkyl phenols having from
about 6 to 20 carbon atoms in the alkyl portion and from about
5 to 30 ethenoxy groups in the polyoxyethylene radical. The
alkyl substituent on the aromatic nucleus may be octyl,
diamyl, n-dodecyl, polymerized propylene such as propylene
tetramer and trimer, isooctyl nonyl, etc. The benzyl ethers
of the polyoxyethylene condensates of monoalkyl phenols impart
--5--
v
good properties to the compositions of the invention. A
typical product corresponds to the formula:
C8H17 ~ OCH2cH2)1sOcH2c6H5
Higher polyalkyl oxyethylated phenols corresponding to the
formula.
R ~ tCH2CH20)nH
Rl ;~ I
wherein R is hydrogen or an alkyl radical having from about 1
to 12 carbon atoms, R1 and R2 are alkyl radicals having
from about 6 to 16 carbon atoms and n has a value from about
10 to 40, are also suitable as nonionic surfactants. A
typical oxyethylated polyalkyl phenol is dinonyl phenol
condensed with 14 moles of ethylene oxide.
- Other suitable nonionic surface-active agents are
co-generic mixtures of conjugated polyoxyalkylene compounds
containing in their structure at least one hydrophobic
oxyalkylene chain in which the oxygen/carbon atoms ratio is
greater than 0.40.
Polymers of oxyalkylene groups obtained from
propylene oxide, butylene oxide, amylene oxide, styrene
20 oxide, mixtures of such oxyalkylene groups with each other
and with minor amounts o polyoxyalkylene groups obtained
fr~m ethylene oxide, butadiene dioxide, and glycidol are
-6-
~ 3~
illustrative of hydrophobic alkylene chains having an
oxygen/carbon atoms ratio not exceeding 0.40. Polymers having
oxyalkylene groups obtained from ethylene oxide, ~utadiene
dioxide, glycidol, mixtures of such oxyalkylene groups with
each other and with minor amounts of oxyalkylene groups
obtained from propylene oxide, butylene oxide, amylene oxide
and styrene oxide are illustrative of hydrophilic oxyalkyl-
ene chains having an oxygen/carbon atom ratio greater than
0.40.
Among the conjugated polyoxyalkylene compounds which
can be used in the compositions of the invention are those
which correspond to the formula:
Y(c3H6o)n(c2H4o)mH
wherein Y is the residue of an organic compound having from
about 1 to 6 carbon atoms and one reactive hydrogen atom, n
has an average value of at least about 6.4 as determined by
hydroxyl number and m has a value such that the oxyethylene
portion constitutes about 20 to 90 weight percent of the
molecule. These surface active agents are more particularly
described in U. S. Patent No. 2,677,700, incorporated herein
by reference.
Other con~ugated polyoxyalkylene surface active
: agents which are most advantageously used in the composi-
tions of the invention correspond to the formula:
Y[ (C3H60)n(C2H40)mH]x
:
~ 3~
wherein Y is the residue of an organic compound having from
about 2 to 6 carbon a~oms and containing x reactive hydrogen
atoms in which x has a value of at least 2, n has a value
such that the molecular weight of the polyoxypropylene
hydrophobic base is at least about 900 and m has a value
such that the oxyethylene content of the molecule is from
about 20 to 90 weight percent. Compounds falling within the
scope of the definition for Y include, for example, propylene
glycol, glycerine, pentaerythritol, trimethylolpropane,
ethylene diamine and the like. As already noted, the oxy-
propylene chains optionally, but advantageously, contain
small amounts of ethylene oxide and the oxyethylene chains
contain small amounts of alkylene oxides such as propylene
oxide and butylene oxide. These compositions are more par-
ticularly described in U. S. 2,674,619 .
Additional conjugated polyoxyalkylene surface active
agents which are advantageously used in the compositions of
this invention correspond to the formula:
P[(c3H6o)n(c2H4omH]x
wherein P is the residue of an organic compound having from
about 8 to 18 carbon atoms and containing x reactive hydrogen
atoms in which x has a value of 1 or 2, n ha~ a value such
hat the molecular weight of the polyoxypropylene portion
--8--
L36
is at least about 58 and m has a value such that the oxy-
ethylene content of the molecule is from about 10 to 90
weight percent and the formula:
P[(C2H4)n(C3~6)mH]x
wherein P is the residue of an organic compound having from
about 8 to 18 carbon atoms and containing x reactive hydrogen
atoms in which x has a value of 1 or 2, n has a value such
that the molecular weight of the polyoxyethylene portion is
at least about 44 and m has a value such that the oxypropylene
content of the molecule is from about 10 to 90 weight percent.
In either case the oxypropylene chains may contain optionally,
but advantageously, small amounts of ethylene oxide and the
oxyethylene chains may contain also optionally, but advan-
tageously, small amounts of alkylene oxides such as propylene
oxide, butylene oxide and higher alkylenè oxides containing up
to 18 carbon atoms in the alkyl chains.
Thus, cogeneric mixtures of conjugated polyoxy-
alkylene compounds containing in their structure the residue
of an active hydrogen-containing compound and at least one
hydrophobic chain of units selected from the group consisting
of oxypropylene and oxypropylene-oxyethylene units in which
the oxygen/carbon atom ratio does not exceed 0.40 and at least
one hydrophilic chain of units selected from the group con- :
sisting of oxyethylene and oxyethylene-oxypropylene units in
which the oxygen/carbon atom ratio is greater than 0.40 are
suitable nonionic surface active agents.
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.. . . .
Further suitable nonionic surface active agents
are the polyoxyethylene esters of higher fatty acids having
from about 8 to 22 carbon atoms in the acyl group and from
about 8 to 30 ethenoxy units in the oxyethylene portion~
Typical products are the polyoxyethylene adducts of rosin
acids, lauric, stearic and oleic acids and the like. Addi-
tional nonionic surface active agents are the polyoxyethylene
condensates of higher fatty acid amines and amides having from
about 8 to 22 carbon atoms in the fatty alkyl or acyl group
and about 10 to 30 ethenoxy units in the oxyethylene portion.
Illustrative products are coconut oil fatty acid amines and
amides condensed with about 10 to 30 moles of ethylene oxide.
Other suitable polyoxyalkylene nonionic surface
active agents are the alkylene oxide adducts of higher
aliphatic alcohols and thioalcohols having from about 8 to
22 carbon atoms in the aliphatic portion and about 3 to 50
oxyalkylene units in the oxyalkylene portion. Typical
products are synthetic fatty alcohols, such as n-decyl,
n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-hexadecyl,
n-octadecyl and mixtures thereof condensed with 3 to 50
moles of ethylene oxide; a mixture of normal fatty alcohols
condensed with 8 to 20 moles of ethylene oxide and capped
with benzyl halide or an alkyl halide; a mixture of normal
fatty alcohols condensed with 10 to 30 moles of a mixture of
ethylene and propylene oxides: a mixture of several fatty
alcohols condensed sequentially with 2 to 20 moles of ethylene
oxide and 3 to 10 moles of propylene oxide, in either order;
-10-
-
~.~41~9L3G
or a mixture of normal fatty alcohols condensed with a mixture
of propylene and ethylene oxides, in which the oxygen/carbon
atom ratio is less than 0.40, followed by a mixture of
propylene and ethylene oxides in which the oxygen/carbon atom
ratio is grater than 0.40, or a linear secondary alcohol
condensed with 3 to 30 moles or ethylene oxide, or a linear
secondary alcohol condensed with a mixture of propylene and
ethylene oxides, or a linear secondary alcohol condensed with
a mixture of ethylene, propylene, and higher alkylene oxides.
Within the broad disclosure of U.S. Patent No.
2,674,619 , nitrogen-containing polyoxyalkylene composi-
tions are included which are more particularly described in
U.S. Patent 2,979,528 . These surfactants possess a
unique feature , namely the ability to disperse lime
soaps formed by fatty acid soaps in hard water
and thus are particularly suitable for use in the surfactant
blend of the invention. These compositions are prepared in
much the same way as those disclosed above and more particu-
larly in accordance with the procedure disclosed in UOS.
2,674,619 but instead of propylene glycol as initiator, a
reactive hydrogen compound containing nitrogen is utilized.
Generally, the nitrogen-containing reactive hydrogen com
pound has up to about six, inclusive, carbon atoms. When
the nitrogen-containing reactive hydrogen compound is so
; defined, there still remains a reasonably broad group of
such compounds which can be used. Ammonia, primary amines,
alkylene polyamines, alkanolamines, heterocyclic nitrogen
. .
, -1 1-
compounds are examples of the classes of nitrogen-containing
reactive hydrogen compounds which can be used.
Thus, primary amines having not over six carbon
atoms such as methylamine, ethylamine, propylamine, bu~yl-
amine, amylamine, hexylamine and aniline are satisfactory.
Alkylene polyamines, especially aliphatic primary diamines,
having not over six carbon atoms are the preferred reactive
hydrogen compounds since the highest fabric detergency values
have been obtained when these were used. These include
ethylenediamine, diethylenetriamine, triethylenetetramine,
tetraethylenepentamine, hexamethylenediamine, phenylenediamine
and the like. Alkanolamines having not over six carbon atoms
can be used such as monoethanolamine, diethanolamine, tri-
ethanolamine, isopropanolamine, tri(2-propanol)amine, 2-amino-
1-butanol, N-butyl-di(2-propanol)amine and the like. Further-
more, heterocyclic nitrogen compounds containing a hetero N
atom can be employed, such as piperazine, 2-methylpiperazine,
2,5-dimethylpiperazine, imidazimidazole, pyrazolidine,
pyrazolidone, hydantaoin, dimethylhydantoin and the like.
Hydroxyl amine and the hydroxylamine derivatives and amino-
phenol and aminophenol derivatives can also be used.
Useful nitrogen-containing nonionic surfactanSs are
mixtures of conjugated polyoxypropylene-polyoxyethylene
compounds based on a nitrogen-containing reactive hydrogen
compound wherein chains of oxypropylene groups having a
defined molecular weight are attached to the nucleus of the
reactive hydrogen compound at the sites of the reactive
-12-
~a41~43G
hydrogen atoms and wherein chains of oxyethylene groups are
attached to the end of the oxypropylene chains. The composi~
tions are prepared by condensing propylene oxide with a
nitrogen-containing reactive hydrogen compound and sub-
sequently condensing ethylene oxide with the propylene oxide-
reactive hydrogen compound condensate.
The collective molecular weight of the oxypropylene
chains attached to the nitrogen-containing reactive hydrogen
compound must be at least about 900 and can range up to about
25,000 or higher. Since the reactive hydrogen compound
employed is one having not more than about six carbon atoms,
it is not sufficiently hydrophobic in and of itself so that a
detergent would be obtained by simply condensing ethylene
oxide with the reactive hydrogen compound. Therefore, the
hydrophobic element of the surfact active compositions of the
invention neces-qarily is found in the defined oxypropylene
chains. These compositions rely on the hydrophobic oxy-
propylene chain just as do the compositions of U.S. 2,674~619,
but distinguish over the general broad class of compositions
disclosed in U.S. 2,674,619 by virtue of the specific class
of reactive hydrogen compounds employed. The advantages
set forth hereinabove are obtained when the compositions have
oxypropylene chains having a molecular weight of at least
about 900 and up to 25rO00. The preferred detergent composi-
tions are obtained when the molecular weight of the oxy-
propylene chains is in the range of about 1000 to 15,000.
This molecular weight is for the molecular weight of the
-13-
oxypropylene chains themselves and does not include the
molecular weight of the particular reactive hydrogen compound
employed.
It is to be noted that it is not necessary to use
pure propylene oxide in producing the oxypropylene chains of
the detergent compositions, although this is preferred. Small
amounts, for example up to about S weight percent, of ethylene
oxide can be included in the propylene oxide employed to
prepare the hydrophobic reactive hydrogen compound-propylene
oxide condensate without significant alteration of the deter-
gent properties of the final composition In this connection,
the ethylene oxide subsequently condensed with the hydrophobic
propylene oxide-reactive hydrogen compound condensate can also
contain small amounts, such as up to about 5 weight percent,
of propylene oxide without significant alteration of the
detergent properties of the compositions of the invention.
It is further to be noted that when molecular
weisht is stated in this specification and claims, unless
otherwise noted, there is meant the average theoretical
molecular weight which equals the total of the grams of the
alkylene oxide employed per mol of reactive hydrogen compound.
It is well recognized in the field of alkylene oxide chemistry
that the polyoxyalkylene compositions one obtains by con-
densing an alkylene oxide with a reactive hydrogen compound
are actually mixtures of compounds rather than a single
molecular compound. The mixture contains closely related
homologues wherein the statistical average number of vxy-
alkylene groups equals the number of mols of the alkylene
-14-
oxide employed and the individual members in the mixture
contain varying numbers of oxyalkylene groups. Thus, the
compositions of this invention are "mixtures" of compounds
which are defined by molecular weight of the polyoxyalkylene
chains and weight percent of oxyethylene groups.
The nitrogen-containing nonionic surfactants
contain chains of oxyethylene groups attached to the oxy-
propylene chains. The amount of ethylene oxide employed is
such that the oxyethylene groups constitute about lO to 90
weight percent of the final composition. Compositions having
outstanding detergent properties are obtained when the weight
percent of oxyethylene groups falls within this range.
Excellent fabric detergency values at 90F have been obtained
in such compositions having from about 25 to 55 weight percent
of oxyethylene groups.
The Second Nonionic Surfactant
.
The second nonionic surfactant component of the
surfactant blend of the invention is prepared usinq an
initiator which can include the nitrogen-based initiators of
U.S. 2,979!528 , but is more broadly defined to
include other initiators (l) having about 2 to
.~ , . .
about 6 carbon atoms and at least 2, preferably 2 to about
6, active hydrogen atoms or (2) having about 6 to about 18
carbon atoms, preferably about 9 to about 11 carbon atoms and
at lest one active hydrogen atom, preferably about 1 to about
6 active hydr.ogen atoms. For instance, hexyl alcohol, octyl
alcohol, stearyl alcohol, ethylene diamine, triethylene
-15-
.
.
diamine, hexamethylene diamine and the like, ethylene glycol,
propylene glycol, trimethylol propane, pentaerythritol, and
erythritol can be utilized as initiators. The second nonionic
surfactant has a relatively low cloud point (1 percent by
weight aqueous solution).
One significant difference between the surfactants
of U.S. 2,979,528 and those used as the second sur~actant
in the novel blend of surfactants disclosed herein is the
sequence in which the block polymer is formed of hydrophilic
and hydrophobic alkylene oxides. The conjugated polyoxy-
ethylene-polyoxypropylene block copolymers can be prepared in
much the same way as the pol~mers of U.S. Patent No. 3,036,118
by first oxyethylating an initiator compound and subsequently
oxypropylating the resulting compound to produce the non-ionic
surface-active agent, as more completely described in U.S.
3,036,118 .
Useful polyoxyalkylene surfactants having a cloud
point in a 1 weight percent aqueous solution of about 10C to
about 30C, preferably about 10C to about 25C, and most
preferably about 15C to about 25C~ which can be blended with
a conventional low-foaming nonionic surfactant have the
formulas:
Y[(Eo/A)m(A)nHlx
Y[(A)o(Eo)m(A)nH]x II
Y[(A)o(Eo/A)m(A)nH]x III
Y[(E/A)m(E/A)n)H]x IV
-16-
. '
wherein EO represents ethylene oxide which is present in the
surfactant polymer in the proportion of about 5 to about 60
percent, preferably about 5 to about 25 percent, and most
preferably about 5 to about 15 percent by weight; Y represents
the nucleus of an active hydrogen-containing organic compound
having a functionality x and (1) about 2 to about 6 carbon
atoms and at least two reactive hydrogen atoms or (2) abut 7
to about 18 carbon atoms and at least one reactive hydrogen
atom; A represents a lower alkylene oxide selected from the
group consisting of propylene oxide, butylene oxide, tetra-
hydrofuran or mixtures thereof; EO/A represents a mixture of
ethylene oxide and a lower alkylene oxide in which EO and A
are present in the proportions by weight of 5 to 95 to 95 to 5
percent; wherein up to 25 percent by weight of A is reacted
directly with said organic compound either alone (in formulas II
' and III) or in admixture with ethylene oxide (in formulas I
and IV) and 75 percent by weight or more of A is subsequently
reacted to produce said polymer: m, n and o are integers in-
dividually selected such that said polymer has an average total
molecular weight generally of about 500 to about 25,000; and
wherein said conventional nonionic surfactant and said second
nonionic surfactant are each generally present in the individ-
ually selected proportion of about 10 to about 90 percent,
preferably 25 to about 75 percent, by weight.
Other polyoxyalkylene ~urfactants having a cloud
point in a 1 weight percent aqueous solution of about 10C to
` about 20C and preferably about 15C to about 20~C, are also
-17-
,.:
useful in blends with conventional low-foaming nonionic
surfactants. These have the formula:
Y [ (E)m(A)nH] X V
where Y, EO, A, m, n, x, molecular weight and useful propor-
tions are as defined herein for formulas I-IV.
It has been found that certain of these so-called
"reverse" polyoxyalkylene block copolymers as defined above,
are particularly suitable both as wetting agents and as
defoaming agents for proteinaceous soils encountered in
machine dishwashing. Useful surfactant compositions result
where the proportion of ethylene oxide utilized is about 5 to
about 60 percent, preferably about 5 to a~out 25 percent by
weight of the polymer and the total molecular weight of the
polymer is generally about 500 to about 25,000, preferably
about 1500 to about 20,000, and most preferably about 2500 to
about 10,000. Especially preferred are such polymers prepared
using an initiator compound characterized as an organic
compound having 2 to about 6 carbon atoms and at least two
rea~tive hydrogen atoms, most preferably, 4 to about 6 re-
active hydrogen atoms and 2 nitrogen atoms. Representativeuseful initiators, besides those listed above, include di-
ethylene triamine, triethylene tetramine, and tetraethylene
pentamine.
The Builder Salts
The automatic dishwashi~g detergents to which
surfactant compositions of the invention are added in order to
-18-
3~
reduce foaming of aqueous solutions thereof in the presence of
raw egg soil generally contain 20 to 80 weight percent of an
alkaline condensed phosphate salt such as tetrasodium pyro-
phosphate and those polyphosphates of the calcium and
magnesium ion sequestering type whose Na2O/P2Os ratios
range from 1:1 to 1.67:1 and 20 to 80 weight percent of an
alkaline detergent salt such as sodium carbonate, sodium
bicarbonate and mixtures thereof, di and trisodium ortho-
phosphate, sodium metasilicate, sodium sequisiicate, borax and
sodium borate. In addition, these detergents often include
5 to 50 weight percent chlorinated trisodium phosphate. A
mixture of lithium hypochlorite or chlorinated cyanuric acid
and trisodium phosphate can be used in place of chlorinated
trisodium phosphate. An automatic dishwashing detergent of
this type can be prepared by adding an aqueous silicate
solution to substantially anhydrous sodium tripolyphosphate
and subsequently adding chlorinated trisodium phosphate
thereto under the conditions as dessribed in U.S. Patent
No. 3,359,207 .
Highly alkaline dishwashing detergents containing
no silicates can attack, etch, and darken aluminum utensils.
Some of these formulations also have a destructive action
on over-the-glaze dish patterns. Suitable proportions of
silicates in the dishwashing formulations help overcome these
difficulties. The silicate used in the compositions of the
present invention is preferably solid granular sodium meta-
silicate, a commercially available material. In the broader
--19--
.... ~, t
.
aspects of the invention, sodium silicates in which the mole
ratio of SiO2:Na2O are more than 1:1, e.g., 2:1 or 3:2:1,
may be used in place of the sodium metasilicate. The sodium
silicate generally constitutes from about 20 percent to about
80 percent of the final composition and preferably from about
20 percent to about 40 percent.
Organic sequestering agents can be used in the
detergent compositions of the present invention in place of
inorganic phosphate salts. Suitable sequestering agents
include the various aminocarboxylates, including ethylenedi-
amine tetraacetates (soluble salts, e.g., Na, K, etc.),
nitrilotriacetates, and the like.
Alternatively to the use of phosphate bulders,
any of the water-soluble metal salts of citric acid can be
used in the practice of the present invention. However, all
salts do not serve with equal effectiveness, and the alkali
metal salts, particularly the sodium and potassium citrates,
are preferred. There are three COOH radicals on the citric
acid molecule. Commercial "sodium citrate" is fully neu-
tralized and is more accurately described as trisodium citrate.Trisodium citrate is available as white crystals or granular
powder. It is odorless, stable in air, and has a pleasant
saline taste. Each molecule of trisodium citrate dihydrate
loses two molecules of water of hydration when heated to
150C. Commercial potassium citrate also exists as white
-20-
crystals or powder. It is normally available as the mono-
hydrate (as contrasted to sodium citrate which exists as the
dihydrate).
As used in the present invention, the amount of
citrate employed will be within the range of 20 to 80 weight
percent on a dry basis (expressed as trisodium citrate).
Water of hydration can be considered to be part of the salt.
More usually, the amount of citrate (whether hydrated or not)
employed will be from 20 to 40 weight percent.
If desired, mixtures of citrates can be used~
Although it is not preferred, a citrate can be formed in situ
from, for example, the combination of citric acid with sodium
or potassium hydroxide. The use of a pre-formed alkali metal
citrate or a mixture thereof is particularly preferred with
dry blended solid detergents.
The combination of the citrate and the condensed
phosphate salt (e.g., sodium tripolyphosphate) appears to
result in enhanced activity, and the total of the citrate and
the condensed phosphate salt will be in the range of 20 to 80
weight percent on a dry basis and will generally not exceed 65
weight percent (dry basis) of the total composition. Ex-
cellent results can be obtained from the combination of sodium
tripolyphosphate and sodium citrate when the ratio on a dry
weight basis of polyphosphate to citrate is less than about
2:1 but greater than about 0.05:1, i.e., 1:2 to 20:1 citrate:-
polyphosphate. One method for formulating a detergent
composition of this invention is to modify the machine dish-
washing detergent formula by replacing more than one-third of
the condensed phosphate salt with citrate; provided, of
course, that the condensed phosphate content is reduced below
35 percent on a dry weight basis.
Although the alkali metal citrates can be chelating
agents and are known to have some water conditioning effects,
these compounds are not particularly effective sequestering
agents at alkaline pH levels. Nor are the citrate5 themselves
known to be particularly outstanding in performing the variety
of functions, in addition to sequestering attributed to sodium
tripolyphosphate ~buffering, de-flocculation, solubilizing or
peptizing, etc.).
However, one-third, one-half, or even nine-tenths or
more of the polyphosphate can be replaced by citrate with
little or no significant loss in overall performance character-
istics of the detergent composition. Although this invention
is not bound by any theory, it appears that so long as suf-
ficient condensed alkali metal phosphate is present to main-
tain a threshold effect, the citrate is an effective sub-
stitute for the remainder of the polyphosphate that would
normally be present in a machine dishwashing detergent.
However, partial replacement of condensed alkali metal phos-
phate with other carboxylic acid salt water conditioning
agents (e.g., gluconate salts) does not appear to provide the
same performance as the partial replacement with citrates.
When citrates are formed in situ from citric acid in
compositions of the present invention, either solid or dis-
solved citric acid can be u-~ed. Commercially available
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aqueous citric acid solutions at concentrations of about 25 to
40 percent by weight are suitable.
The Chlorine Releasin~_A~ents
Another ingredient of the detergent compositions of
this invention is an active chlorine-containing compound. The
active chlorine-containing compound imparts germicidal and
bleaching action to the detergent compositions. Active
chlorine-containing compounds which may be employed in ac-
cordance with this invention include chlorinated trisodium
phosphate, trichlorocyanuric acid, sodium salt of dichloro-
cyanuric acid, potassium salt of dichlorocyanuric acid, o-
sodium hypochlorite and 1,3-dichloro-5,5-dimethylhydantoin~
Based on 100 parts of detergent composition, 5 to 50 parts of
active chlorine-containing compound may be employed. If
chlorinated trisodium phosphate is employed, then from 10 to
25 parts of the chlorine compound are preferred since the
amount of chlorine available in chlorinated trisodium phos-
phate is only 0.325 part per part of compound. Much higher
amounts of chlorine are available in the chlorinated cyanuric
acids and, therefore, when they are employed from five to ten
parts of active chlorine compound are preferred.
Test Methods
The foam characteristics of the detergent composi-
tions were measured by observing the rate of rotation of the
perforated spray arm of an automatic dishwashing machine
during the washing cycle in which raw egg soil and/or milk
soil and detergent were present in definitive quantities. The
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rate of rotation of the spray arm is, of course, inversely
proportional to the amount of foam present. In each of the-
subsequent examples, foam evaluation was carried out in a
Hobart Kitchen Aid dishwasher. The procedure followed was to
turn on the machine and, after part of the water had been
added, turn off ~he machine and add the detergent composition
and additives, if any, and 15 cc. of raw egg and/or 15 grams
of milk soil. The dishwasher was then turned on again and the
balance of the water added. The water was at a temperature of
about 120~ or about 140F. After the washing cycle started,
the rate of rota~ion of the perforated spray arm was measured
from the first to the second minute and from the third to the
fourth minute. In the presence of excess foam, the rotor arm
stopped or the foam overlowed. A spray arm rotation of about
70 r.p.m. or more is indicative that foam formation is being
subsequently depressed.
The following examples illustrate the various
aspects of the invention but are not intended to limit its
SCOp@. Where not otherwise specified throughout this specifi-
cation and claims, temperatures are given in degrees centi-
grade and parts, percentages, and proportions are by weight.
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9L3~
Example 1
A machine dishwashing detergent was prepared
utilizing a blend of two nonionic surfactants for a total
weight of 3 percent of surfactant, tetrasodium pyrophosphate
35 percent by weight, sodium tripolyphosphate 20 percent by
weight, sodium metasilicate pentahydrate 10 percent by weight,
chlorinated trisodium phosphate 20 percent by weight, and
water 12 percent by weight. A conventional 3600 molecular
weight heteric polyol was employed. This is prepared by
condensing a mixture of ethylene oxide and propylene oxide in
a weight ratio of ethylene oxide to propylene oxide of 9:1
with a 2700 molecular weight condensation product of tri-
methylolpropane and a mixture of propylene oxide and ethylene
oxide in a weight ratio of propylene oxide to ethylene oxide
of 9:1. The second nonionic surfactant was a block polyol
having a molecular weight of about 8000 prepared by condensing
a mixture of ethylene oxide and propylene oxide in a weight
ratio of propylene oxide to ethylene oxide of 9:1 with the
tetrafunctional initiator N,N,N',N'-tetrakis(~-hydroxypropyl)-
ethylenediamine. The proportion of the conventional sur-
factant to the second surfactant is 9:1 by weight.
The detergent is prepared by blending an aqueous
mixture of the surfactant with the phosphate ingredients. The
blending can be accomplished in any manner such as by pouring
or spraying. By combining the phosphate ingredient with the
surfactant, ehe hydration of the phosphate occurs in the
presence of the surfactant which is simultaneously absorbed by
4~6
the phosphate ingredient. This also protects the surfactant
from the action of the metasilicate and the chlorinated
compound which are subsequently added. Thereafter, the sodium
metasilicate pentahydrate is added while the mixture is
constantly mixing. Next, the detergent mixture is reduced to
any desired particle size by any conventional means such as
crushing, grinding and, preferably, screening. Generally,
when the mixture i5 screened, a 5~mesh to 25--mesh screen is
used, as this size particle is most appropriate for automatic
machine dishwashing operations. Chlorinated trisodium phos-
phate is next added to the screened mixture. Alternatively,
this compound can be added together with the sodium meta-
silicate pentahydrate. Preferably, the chlorinated trisodium
phosphate is added when no moisture is present and therefore,
it is desirable to add the chlorinated trisodium phosphate
subsequent to the addition of the sodium metasilicate penta-
hydrate.
The dishwasher detergent was evaluated at a concen-
tration of 0.3 percent by weight in accordance with the
procedure described above utilizing an automatic dishwashing
machine in which raw egg soil and milk soil were successivel;y
utilized in measured amounts~ The water temperature was
maintained in one test at 120F and in a second test at 140F.
The test results indicate fair performance for the machine
dishwashing detergent of Example 1 at either 120F or 140F
water temperatures.
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4L3~
Example 2
Example 1 was repeated except that the surfactant
component was a blend of the second surfactant of Example 1
with the conventional surfactant of Example 1 in the respec-
tive weight proportion of 9:1. Evaluation of the detergent
composition utilizing an automatic dishwashing machine in
accordance with the above procedure indicated the detergent
provided excellent foam suppression and excellent detergency.
Example 3
The machine dishwashing detergent of Example 1
was prepared except that the surfactant blend was an equal
parts by weight mixture of the conventional surfactant of
Example 1 and the second surfactant of Example 1. Evaluation
in accordance with the procedure above in a machine dishwasher
resulted in a rating of excellent at both 140 and 120F water
temperature conditions.
Example 4
The conventional nonionic surfactant of Example 1
was blended with the second surfactant of Example 1 in the
respective weight proportion of 9:1 and utilized together with
a non-phosphate builder to prepare a machine dishwashing
detergent. The nonionic surfactant blend was utilized in the
amount of 5 percent by weight and blended with 30 percent by
weight sodium citrate, 20 percent by weight sodium carbonate,
30 percent by weight sodium metasilicate pentahydrate, 11
percent by weight sodium sulfate, and 4 percent by weight
chlorinated cyanurate. The mixture was reduced to appropriate
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particle size using a 25 mesh screen and evaluated as a
machine dishwashing detergent in accordance with the procedure
described above wherein milk soil and egg soil were utilized
in measured amounts for comparative testing of the effective-
ness of the machine dishwashing detergent. Evaluation using a
water temperature of 120F or 140F indicates fair performance
in a machine dishwasher.
Example 5
Example 4 was repeated using the surfactant blend of
Example 4 in the proportion of 1 part by weight of the conven-
tional nonionic surfactant of Example 4 with 9 parts by weight
of the second surfactant of Example 4. Evaluation in a
machine dishwasher in accordance with the procedure described
above, indicates excellent performance both at a water tempera-
. ture of 120F and 140F.
Example 6
Example 4 was repeated except that the weight ratioof conventional nonionic surfactant to the second surfactant
was 1:1 by weight. Evaluation utilizing a machine dishwa~her
in accordance with the procedure described above indicates
excellent performance both at water temperatures of 120F and
140F.
xample 7
(Control - Forming No Part Of This ~nvention)
The machine dishwashing detergent of Example 1 was
prepared except that the surfactant utilized was a blend of
the conventional nonionic surfactant of Example 1 in the
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~1~8~3~;
amount of 97 parts by weight with 3 parts by weight of mono-
stearyl-acid phosphate, the preparation of which i8 described
in U.S. 3,314,891 . Evaluation oE this detergent in
a machine dishwasher utilizing .the procedure described
above both at a water temperature of 120F
and 140F utilizing a concentration of the detergent in water
of 0.3 percent by weight resulted in a determination that the
detergent provides excellent results in foam control and
detergency at both operating temperatures.
Examples 9-11
Examples 1-3 were repeated substituting a detergent
similar to the second nonionic detergent except having a
molecular weight of about 5000. Performance evaluation both
at 120F and 140F water temperatures in a machine dishwasher
in accordance with the procedures described above, resulted in
similar determinations for foam control and detergency as
reported for Examples 1-3, i.e., the performance of Example 9
was similar to that of Example 1, Example 10's performance was
similar to that of Example 2, etc.
In the following tables, there are tabulated the
results of the evaluation of certain of the detergents pre
pared in the Examples utilizing a machine dishwasher in
accordance with the procedure described above. Table I lists `
the performance at a water temperature of 120F and Table II
lists the performance of detergents utilized at a water
temperature of 140F. In all evaluations, the concentration
of detergent in the water was 0.3 percent by weight.
.
Table I
Machine Dishwasher Evaluation
(Water Temperature - 120F; Concentration of
Detergent 0.3 Percent by Weight)
Spray Arm SPeed (rpm)
Example No Soil i7~ lk Soil
1 79 62 60
3 86 72 7
7 (control) 70 56
8 (control) 86 71 73
Table II
Machine Dishwasher Evaluation
(Water Temperature - 140F Concentration of
Detergent 0.3 Percent by Weight)
Spray Arm Speed (rpm)
_Example No Soil Egg Soil Milk Soil
1 78 57 62
3 85 73 73
7 (control) 66 50 53
8 (control) 84 73 70
While this invention has been described with
reference to certain specific embodiments, it will be recog-
nized by those skilled in the art that many variations are
possible without departing from the scope and spirit of the
invention and it will be understood that it is intended ko
cover all changes and modifications of the invention dis-
closed herein for the purposes o illustration which do not
constitute departures f rom the spirit and scope of the
invention.
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