Note: Descriptions are shown in the official language in which they were submitted.
~i:
2087409
NON-PHOSpHATE DISHWASHIN~ CQMPOSITION
AND CITRATE METHOD THEREFO~E
Field of the Invention.
The present invention generally relates to
automatic dishwashing compositions, and more
particularly to a non-phosphate dishwashing composition
where a citrate salt is preferably generated during the
composition preparation and the composition provides
cleaning performance equivalent to phosphate containing
dl~hwa~hing compositions.
Backaround o~ the Invention.
Beginning in the 1950s and early 1960s, the
foaming of streams, rivers, and so~e lakes was a
condition widely noted as approaching an ecological
crisis in the United States. Today the Environmental
Protection Agency estimates that 25% of the nation's
lakes are polluted and another 20% are threatened. ~he
Senate Majority ~eader has recently announced he plans
to introduce legislation aimed at increasing the
protection of fresh water lakes, including the
elimination of the use of phosphatss in detergents.
Lakes become cloudy when excessive phosphate pollution
from detergents and agriculture boosts the growth of
algae. Although phosphates account for only a small
percentage of phosphorous emissions overall in the
United States, detergent phosphorous is a much more
significant percentage in some highly populated areas.
20~7~Q9
The first bans on phosphates in detergent
occurred in the Great Lakes region in the 1970s when
Lake Erie, in particular, was choked with pollution.
Most recently, Pennsylvania has been acting to regulate
phosphates.
The best selling book 50 Simple ~hings You Can
Do To SaYe The Earth recommends the use of a low-
phosphate or phosphate-free detergent and ~entions that
liguid detergents are generally phosphate-free. In the
United States, bans on the use of sodium
tripolyphosphate (STPP) have boosted sales of phosphate-
free deterqents to a significant share of the domestic
market; however, phosphate continues to be the leading
"builder" in U.S. and European detergent production.
Detergent builders are substances that
increase the effectivene~s of surfactants and typically
act as water softeners and as sequestering and buffaring
agents. Because phosphates are excellent, inexpensive
builders, replacing phosphates has posed difficultie~,
particularly for certain applications and for dry
cleaning compositions. For example, although there are
a number of patents that have issued since the later
1970s describing various non-phosphate automatic
dishwasher detergent compositions, commercial
acceptability has not followed, due perhaps to
inadequate cleaning performances provided by these
alternate compositions. Also, in~reased production
expense and stability problems for granulated, non-
phosphate compositions have been encountered.
U.S. Patents 3,825,498, issued July 23, 1974,
4,203,858, issued May 20, 1980, and 4,539,144, issued
September 3, 1985, describe dishwashing compositions
that include specific polymers or polymers in particular
amounts as replacements for phosphates. Thus, the
3,825,498 patent (inventors Altenschopfer et al.)
describes a dishwashing detergent composition that
~JJ `
20s7~os
includes 5-90% by weight of a solid crosslinked or non-
crosslinked hydroxycarboxylic acid polymer and that is
said to have a particularly strong cleaninq ef~ect
against protein containing burnt scraps of food. Patent
4,203,858 ~inventor Chakrabarti) describes a dishwa~hin~
composition that includes a polyelectrolyte salt with a
molecular weight between about 500-4,000 and that i~
said to be phosphate-free and low foaming. Patent
4,539,144 (inventors de Ridder et al.) describe~ a
dishwashing composition with a small amount of
hydrolyzed polymaleic anhydride havinq an average
molecular weight of about 2S00, which is said to have
improved non-foaming, non-spotting, or non-streaking
properties.
U.S. Patents 3,941,710, issued March 2, 1976,
4,049,585, issued September 20, 1977, and 4,127,496,
issued November 28, 1978, all describe low or anti-
foaming surface active agents, typically non-ionic for
inclusion in cleaning compositions. Thus, Patent
20 3,941,710 (inventors Gilbert et al.) de~cribQs USQ of a
specific type of anionic surfactant (polyether
carboxylate) with a non-ionic surface active agent.
These surfactants are described for use with an anti-
foaming agent of a fatty acid phosphate or certain fatty
acids and together are said to permit the reduct1on of
phosphate content to not more than 15 percent. Patent
4,049,585 (inventor Heckert) discloses use of vicinal
non-terminal disulfates as low sudsing surfactants
u~eful in automatic dishwashing compositions containing
a low amount of conventional sequestering builders such
as phosphates. U.S. Patent 4,127,496 (inventor Stokes)
describes uses of non-ionic detergents with either
tetrasodium ethylenediamine tetracetate or
nitrilotriacetic acid. However, the latter, while an
ef~ective builder, has been implicated in possible
carcinogenicity.
2087409
U.S. Patent 4,162,987, issued July 31, 1979,
inventors Maguire, Jr. et al., describes automatic
dishwashing compositions with a binary enzyme system
comprising a proteolytic enzyme and an amylolytic
enzyme. Polyphosphates are suggested for inclusion as
builders in the compositions.
U.S. Patent 4,576,72~, issued March 18, 1986,
inventor Browne, discloses phosphate-free detergent
compositions for textile washing and notes that
replacements of the customary tripolyphosphate builders
have been unsatisfactory for one reason or another, with
replacement by sodium citrate requiring such a large
amount, particularly for high temperature washing, that
the costs would be unacceptable.
Summarv of the Invention.
The present invention provides a substantially
dry, water-soluble composition that is useful for hard
surface cleaning in the presence of water without the
necessity of inc~uding phosphate builders, but which
composition provides comparable cleaning performancQ to
phosphate-built compositions. A particularly preferred
embodiment is useful for automatic dishwashing and
comprises intimately admixed particles of a carbonate
salt and a citrate where the salts have a common
alkaline metal cation, an anti-redeposition agent, an
alkaline metal silicate, a non-ionic surfactant, and an
enzyme system. The inventive composition has a pH of
between about 9 to about 12 when dissolved in water
during use.
The preferred citrate of the sequestering
agent is in an amount up to about 31% of the total
composition and is formed from the carbonate salt during
preparation of the composition, which reduces the
overall cost of the product.
2087409
Detailed Descri~tion of Preferred Embodiments.
The role of builder in cleaning compositions
of this invention i9 primarily filled by a
hydroxycarboxylic acid salt which functions both as
builder and as sequestering agent. A particularly
preferred hydroxycarboxylic acid salt is a salt of
citric acid having the structure:
o OH O
Il I 11 ~
M--CCH2fCH2CM
C=O ~ ~,
M
~-~
wherein M is an alkaline metal cation, preferably sodium
or potassium. In the alkaline metal salt form, th~
citrate is stable in air and, by control of other
critical parameters for the inventive composition,
allows greater than about lZ month shelf stability for
cleaning composition embodiments of the invention.
The neutralization reaction of citric acid
with carbonate proceeds by the equation:
O OH O O OH O
Il l 11 11 1 11
2 (HOCCH2fCH2COH) + 3M2CO~ + H20 -- M--CCH2CCH2CM +
C=O C=O
OH M
[H20 and CO2]
However, the prior art conversion of citric acid to
citrate by neutralization in solution has lead to
unacceptably high costs for formulating cleaning
compositions. In one aspect of the present invention,
dry citric acid and dry carbonate, such as sodium or
, _ , , . .. .. ~
2087409
potassium carbonate, are admixed. An amount of water,
preferably limited to less than about or about S wt.~ of
th~ dry blend, is added and the thus moistened adm~xture
further mixed well. An exothermic acid/base
S neutralization reaction commences with generation of
carbon dioxide and with the citric acid being converted
to citrate. Because compositions of the invention also
include carbonate as a builder (that is, a co-builder
with the citrate) it is preferred to admix all, or most,
of the carbonate to be included in the formulation
(preferably between about 5 wt.% to about 50 wt.% before
the reaction and about 1 wt.% to about 34 wt.S after the
reaction) during this neutralization step so that the
excess carbonate helps drive the reaction and ensures
lS that all, or substantially all, the citric acid is
converted to citrate. A microscopic examination of the
re~ction products can be used to reveal the absence of
citric acid crystals at the conclusion of the reaction.
The amount of water added during the
neutralization is preferably limited so as to be ju~t
sufficient for neutralization to occur at interfaces of
the otherwise substantially dry materials. The use of
substantially dry neutralization agent, such as sodium
carbonate, reduces the water content and thus the amount
of drying. This increases ease of processing. However,
there must be sufficient water to accommodate mass
transfer considerations in order for the neutralization
to efficiently proceed.
The amount of citric acid in preparing
inventive compositions is preferably between about 5
wt.% to about 20 wt.% which results, after reaction, in
citrate in an amount from about 7.5 wt.% to about 31
wt.%.
Due to the particularly preferred in situ
preparation of citrate, intimately admixed particles of
carbonate salt and citrate having a common alkaline
,,, .. _ . . . ............ , . .. . . .. _ _ .... . . . . .. .... . .. .
20874~9
_
metal cation will be obtained for use in for~ulatin~ dry
cleaning compositions with suitable surfactant blends
for hard surface cleaning.
Suita~le surfactant blends of the invention
include a non-ionic surfactant, preferably with low
foaming properties for automatic dishwashing
applications, an anti-redeposition agent, preferably one
that also functions to chelate calcium ions, an aLkali
metal silicate, and an enzyme system having enzymatic
activity at alkaline pH. Each of these components will
now be more specifically described.
Non-Ionic Surfactant.
Preferred non-ionic surfactants, or surface
active agents, are ethylene oxide or propylene oxide
condensates. ExQmplative are the react$on products o~
benzyl chloride and ethoxylated al~yl phenol and others
as described by U.S. Patent 4,12~,496. Among the many
non-ionic surfactants that are useful in compositions of
the invention are those co~mercially available under the
trade name "Polytergent SLF-18~' (available from Olin
Chemical). Compositions of the invention preferably
include non-ionic surfactant in amounts between about 1
wt.% to about 10 wt.%.
Anti-Rede~osition Aaent.
A preferred anti-redeposition agent also
functions to chelate calcium ions or to inhibit calcium
crystal growth. During the automatic dishwashing cycle,
there is a tendency for calcium salts to precipitate,
normally as calcium carbonate crystals. This crystal
growth causes spotting and filming on glassware.
Phosphate salts can be used to inhibit calcium crystal
growth, but where a phosphate-free composition is being
prepared, it is particularly important to prevent
calcium crystal growth and to sequester calcium (and
2087409
_ _
magnesium) ions, to remove such ions from the soils
being cleaned to make the soils more soluble, and to
maintain such soils in solution for removal.
A preferred anti-redeposition agent with the
desired chelating and/or calcium crystal growth
inhibiting properties is a polyelectrolyte salt,
preferably a polyacrylyte or methacrylyte salt ha~ing a
molecular weight between about 500 to about 10,000.
- Such a polyelectrolyte must be water soluble, and a `
number of suitable anti-redeposition agents are
commercially available. Such components include, for
example Sokalan polyacrylate ~available from BASF1 and
Good-Rite polyacrylate (available from Goodrich). The
water soluble polymeric component is preferably included
in thQ inventive compositions in a range between about
1 wt.% to about 8 wt.%.
Alkali Metal Silicate. -
Silicate components prevent etching of
aluminum and glassware over repeated wash cycles.
Sodium silicate is a preferred silicate component and
also functions as an alkaline agent to saponify and
agglomerate soils. Since foods tend to be acidic,
alkalinity of the inventive composition is preferably
between about 9 to about 12, most preferably about 10 to
lO.S. Thus, the silicate and the earlier described
carbonate together function to raise the pH of inventive
compositions.
While sodium silicate is a preferred silicate
component, potassium silicate and metasilicates are also
useful. The silicate component is preferably in an
amount from about 2 wt.% to about 50 wt.~ of the
- inventive compositions.
2087409
Enzvme SYstem.
A suitable enzyme system of the present
invention includes a proteolytic enzyme and an
amylolytic enzyme, both of which must be active within
s the highly alkaline range of the compositions. Enzyme~
aid the removal of soils, and suitable enzyme system~
include the proteolytic and amylolytic, alkaline
resistant enzymes described by U.S. Patent 4,162,987.
Because, however, the enzymes could be degraded or
lo inactivated during the in s1tu reaction between citric
acid and carbonate preferred for practice of this
invention, the enzyme should be added after the
acid/base reaction has taken place and after any
agglomeration step. The actual amount of enzyme system
added to the compositions will depend, of course, upon
the specific activity o~ the enzymes. Where one m~xe~
th~ two commercially available enzymes from Novo Nordi~k
Bioindustrials (protease-Esperase 6.0T and Amala~e-
$ermamyl 60T), then typical enzyme amounts will be about
equal parts of amylase and protease in a combined range
of about 0.4 wt.% to about 4 wt.% of the total
composition.
O~tional Com~onents.
Where desired, additional builders,
sequestering agents, dyes, fragrances, oxidizing agents,
and/or chelating agents may be optionally included. For
example, particularly preferred embodiments of the
invention include minor amounts of tetrasodiu~
ethylenediamine tetracetate in amounts up to about 5
wt.%. Excipients, such as alkaline metal sulfates
andlor chlorides in amounts up to about S0 wt.%, are
desirable. Where an oxidizing agent is~ ce~sired to
assist in preventing staining on glassware~an~ film
buildup (and which may also provide some sterilization,
although the primarily sterilizing function is achieved
-;;
20~7409
by the elevated water temperature during the washing
cycle of automatic dishwashers)~ then such may be
included in amounts up to about 40 wt.% of, e.g., a
percarbonate (of which about 14% is usually A.O.).
Selected oxidizing agents must be stable in the highly
aLkaline solutions of the inventive compositions, not
adversely affect the enzymes, and should be added after
the acid/base in situ reaction to citrate. A
particularly suitable such oxidizing agent is sodium
percarbonate.
Other optional components may also be
included, so long as they are compatible with the
inventive compositions as described. Free water of the
final, shelf-ready compositions should not exceed 6
wt.%.
Compositions of the invention take the form of
dry granules that are preferably agglomerated to reduce
du~t and to standardize particles to a preferred
particle range size. When agglomerated, then the
silicate component or the polymer component may be used
as an agglomerate agent by dissolving in water and
spraying on the admixed blend. The preferred particle
size range is between about 12 mesh to about 50 mesh.
A particularly preferred embodiment of the
composition has the following formulation and forms a
solution pH when dissolved of 10.5:
,,, .. ... ....... _ ... _.. . ---
20~7409
PARTICULARLY PREFERRED EMBODIMENT
Used in Final
PreParation Fon~lation
(wt.%) (wt.~)
5 Sodium citrate 0 15
Citric Acid 9.8 o
Sodium carbonate 18.1 10
Polymer 2
(Sokalan polyacrylate,
10MW 8,000)
Sodium silicate
(15% of 47% solution)
Non-ionic surfactant 2
(Polytergent SLF.18)
15 Amalase O.5
(Termamyl 60T)
Protease ~ 5
tEsPerase 6.OT)
Na4 EDTA 0.5
20 NaCl 11
Na2So4 44.2
Free water 3.5
Example 1 describes the preparation of thi~
particularly preferred embodiment, which was then used
in spot and film performance testing as described by
Examples 2 and 3.
EXAMPLE 1
In a Marion or other type of suitable mixer
the dry citric acid and sodium carbonate were mixed
together. Excipients such as sodium sulfate and other
non-reactive ingredients were also added at this time,
but can be added during the next step or after the
reaction is complete.
Water was added to the dry blend and mixed
~ell. An exothermic acid/base reaction began to take
place~ Heat and carbon dioxide were generated, and the
citric acid was converted to sodium citrate. A
microscopic examination of the reaction products
20~7~0~
revealed the absence of citric acid crystals. This
reaction took place in the initial mixer. (All or part
of the citric acid may be added as a solution so that
the addition of water may not bé required for the
reaction to take place.)
The remaining formulation ingredients, except
enzymes, were added next. (If dry blending is selected,
then all the ingredients are mixed well to homogenize.)
If the product is to be agglomerated, a suitable
agglomerant, either silicate, or polymer will be held
back from earlier steps, dissolved in water, and sprayed
on the mixture as required. Suitable apparatus for
agglomeration include Rotary Drum (o~rien~ Fluid Bed
(Shuggi) or Twin Shell (P.X.) type mixers. After drying
the mixture to ~6% free water, the rest of the
ingredients were added and the formulation was well
mixed.
_ EXA~PLE 2
The particularly preferred embodiment, such as
described by Example 1, was compared to four
commerciallyavailable,phosphate-containingdishwashing
compositions. The test protocol was whereby clear glass
tumblers were soiled with margarine and milX. The
soiled tumblers were then washed in automatic
2S dishwashers for five cycles with the recommended dosages
of either one of the four commercially available,
phosphate-containing dishwashing compositions or with
the inventive composition (at 10 ml/cup or 20 ml/cup
recommended dosage, depending on water hardness). A
panel of six persons then graded the washed tumblers on
a scale of "4" (meaning no spots or filming) to "0"
(meaning totally covered with spots and films). The six
scores were averaged for each composition.
2~409
With water having a hardness of 150 ppm,~the
test panel following the just prescribed protocol rated
the five compositions as is shown by the data in Table
1. The test panel did not ~now which composition was
being rated.
TABLE 1
Avera~e S~otlFilm Score
Prior Art Comp. 1 3.
(40 mL/cup)
10 Prior Art Comp. 2 3.38
(4~ mL/cup)
Prior Art Comp. 3 3.46
(40 mL/cup)
Prior Art Comp. 4 2.19
15(10 mL/cup)
Inventive Comp. 3.34
(10 mL/cup)
As can be seen from the data of Table 1, the inventive
composition provided comparable results to three of the
phosphate-containingcommerciallyavailablecompositions
(and superior performance to a fourth), although the
inventive composition contained no phosphates while all
four of the commercially available comparative
2S compositions did contain phosphates.
EXAMPLE 3
A protocol analogous to that described by
Example 2 was followed except that water having an
hardness of 300 ppm was used. The same four
commercially available comparative compositions were
used (ranging in total phosphate from about 6.1 wt.% to
about 8.7 wt.%), except that the prior art composition
4 was used at the increased recommended dosage of 20
ml/cup and the inventive composition was likewise used
....... . .. .. .
2087~09
at the increased recommended dosage of 20 ml~cup. Table
2 sets out the results.
TA~LE 2
Averaae S~ot/Film Score
5 Prior Art Comp. 1 2.98
(40 mL/cup)
Prior Art Comp. 2 3.16
(40 mLlcup)
Prior Art Comp. 3 3.45
(40 mL/cup)
Prior Art Comp. 4 0.68
(20 mLlcup)
Inventive Comp. 3.35
(20 mLlcup)
As wa5 de5cribed for Example 2, the inventive
composition aga~n provided substantially comparable
results to three of the co~ercially available
compositions (and considerably superior to the fourth)
despite the wash water being relatively hard and despite
the absence of phosphates in the inventive composition.
It is to be understood that while the
invention has been described above in conjunction with
preferred specific embodiments, the description and
examples are intended to illustrate and not limit the
scope of the invention, which is defined by the scope of
the appended claims.
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