Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02311998 2000-06-20
CAUSTIC STABLE NONIONIC SURFACTANT COMPOSITIONS
AND METHODS FOR THEIR USE
1. Field of the Invention.
The invention relates to surfactant compositions containing a caustic
ingredient
and surfactant and methods for their use. The caustic stability of the
composition is
enhanced by providing a nonionic surfactant containing an alkylene oxide
homopolymer
or copolymer moiety and terminal tertiary hydroxyl groups.
2. Background of the Invention.
Nonionic surfactants are o$en components in formulations containing highly
caustic ingredients such as sodium hydroxide or potassium hydroxide. If
specific
blending procedures that avoid the intimate contact of nonionic surfactant
with caustic are
not followed, the nonionic surfactant is subject to extreme discoloration and
sometimes
degradation to the extent that important performance functions, such as
defoaming, are
lost. The caustic stability of a nonionic surfactant can be improved by
providing a
nonionic surfactant that has an alkyl group capping the terminal hydroxyl
groups of the
2 0 nonionic surfactant. Nevertheless, currently available nonionic
surfactants, including
those having an alkyl group capping the terminal hydroxyl groups, do not have
sufficient
caustic stability to be optimally useful in such applications. Furthermore,
the alkyl group
CA 02311998 2000-06-20
capped nonionic surfactants are more expensive to manufacture than the
nonionic
surfactants of the current invention.
Mori, U.S. 4,703,114, has disclosed polyethers with a tertiary alcohol moiety
at
the terminal end. The polyethers are less reactive than conventional
polyethers when
preparing polyurethane resins. Le-Khac, U.S. 5,545,601, discloses a polyether
that has
tertiary hydroxyl groups, which are useful as part of an improved double metal
cyanide
catalyst system.
Neither Mori nor Le-Khac teach, nor do they suggest, the caustic stable
compositions of the current invention. They also fail to teach methods of
using the
compositions of the current invention to improve the caustic stability of
surfactant
compositions. Furthermore, they do not teach or suggest methods for defoaming
based
on using the novel compositions of the current invention.
3. Summary of the Invention.
According to the present invention, a surfactant composition is provided
having
improved caustic stability, the surfactant composition comprising a caustic
material and a
nonionic surfactant comprising an alkylene oxide homopolymer or copolymer
moiety and
terminal hydroxyl groups, wherein at least 70% of the terminal hydroxyl groups
are
tertiary hydroxyl groups. Preferably, at least 85% of the terminal hydroxyl
groups are
tertiary hydroxyl groups.
3 0 There is also provided, according to the present invention, a nonionic
surfactant
comprising the reaction product of a nonionic intermediate and isobutylene
oxide wherein
the nonionic intermediate comprises an alkylene oxide homopolymer or a
copolymer of
two or more different alkylene oxide monomers and has a first hydroxyl number,
wherein
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CA 02311998 2000-06-20
the reaction product has a second hydroxyl number, and wherein said second
hydroxyl
number is at least 70% lower in comparison to said first hydroxyl number.
Preferably, this is done by reacting the nonionic intermediate with sufficient
isobutylene oxide so that at least about 70% of the terminal hydroxyl groups
will be
tertiary hydroxyl groups. The nonionic surfactant of the invention exhibits an
advantageous stability in a caustic or alkaline environment.
The present invention also provides, in one embodiment, nonionic surfactant
compositions resistant to degradation in a caustic environment that comprise
alkylene
oxide polymers wherein the terminal hydroxyl groups are tertiary. In another
embodiment, there is provided a method for improving the caustic stability of
surfactant
compositions by incorporating a nonionic surfactant comprising an alkylene
oxide
homopolymer or copolymer and tertiary terminal hydroxyl groups. Finally, there
is
provided a method for defoaming alkaline aqueous solutions involving adding a
nonionic
surfactant to the solution, wherein the surfactant comprises nonionic
defoaming agents
that have been modified so that they contain tertiary terminal hydroxyl
groups.
4. Detailed Description of a Preferred Embodiment of the Invention.
The novel compositions of the invention are based on a nonionic surfactant
having an alkylene oxide homopolymer or copolymer moiety and terminal tertiary
hydroxyl groups. Preferably, at least 70% of the terminal hydroxyl groups on
the
nonionic surfactant will be tertiary hydroxyl groups. It is more preferred
that at least 85%
of the terminal hydroxyl groups be tertiary, and most preferred that they be
at least 90%
tertiary hydroxyl groups. The nonionic surfactant having terminal hydroxyl
groups can
be added to a composition comprising caustic materials to produce a caustic
stable
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CA 02311998 2000-06-20
surfactant composition. Alternatively, the tertiary hydroxyl group-containing
nonionic
surfactant can be used in a defoaming composition-the nonionic surfactant
being
resistant to breakdown in a caustic environment and thus maintaining its
efficacy over
time in the caustic environment.
Nonionic surfactants useful in the invention can be prepared by reacting a
nonionic intermediate with a monomer that will result in tertiary groups being
incorporated into the nonionic surfactant. Examples of suitable monomers
include
isobutylene oxide, 1,1,2-trimethylethylene oxide, 1,1,2,2-tetramethylethylene
oxide, 2,2-
dimethyloxetane, diisobutylene oxide, and alpha-methylstyrene oxide. For
reasons of
availability and cost, isobutylene oxide is preferred. In that case, the
nonionic surfactant
is the reaction product of a nonionic intermediate and isobutylene oxide.
One preferred nonionic intermediate comprises an alkylene oxide homopolymer.
Non-limiting examples of nonionic surfactants in this class include
polyethyleneoxide
and polypropyleneoxide as well as alcohol initiated ethylene oxide polymers,
commonly
referred to as ethoxylated alcohols. Another preferred nonionic intermediate
comprises a
copolymer of two or more different alkylene oxide monomers. Useful alkylene
oxides
can be selected from the group consisting of ethylene oxide, propylene oxide
1,2-butylene
oxide, 2,3-butylene oxide, 1,2-hexylene oxide, and styrene oxide. Higher alkyl
epoxides
such as those with 5 or more carbon atoms can also be useful.
3 0 Nonionic intermediates can be characterized by a hydroxyl number. The
hydroxyl
number is determined according to ASTM method E326-96. In the method, terminal
hydroxyl groups are esterified with phthalic anhydride. The excess phthalic
anhydride is
hydrolyzed, and the acid is titrated with sodium hydroxide. The hydroxyl
content is then
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CA 02311998 2000-06-20
calculated by difference. The method is not suitable for determination of
tertiary
hydroxyl groups, because the tertiary hydroxyl groups do not react with the
phthalic
anhydride reagent. For a general discussion, see Thomas M. Schmitt, Analysis
of
Surfactants, (Marcel Dekker 1992) pp. 64-65 and references cited therein.
Nonionic surfactants useful in the invention can be made by reacting the
nonionic
intermediate with isobutylene oxide, so that the isobutylene monomers are
added to the
ends of the polyalkyleneoxide chains of the nonionic intermediate, thus
creating tertiary
terminal hydroxyl groups. The nonionic surfactant thus comprises an alkylene
oxide
homopolymer or copolymer moiety (corresponding to the polyoxyalkylene chains
of the
nonionic intermediate) and terminal hydroxyl groups (corresponding to the
tertiary
hydroxyl groups incorporated by addition of the monomers to the end of the
polyoxyalkylene chains). The tertiary hydroxyl groups do not react with the
hydroxyl
number reagent, and so do not contribute to the measured hydroxyl number.
Therefore,
when the hydroxyl number of the tertiary terminated nonionic surfactant is
measured, the
observed hydroxyl number will be lower in comparison to that of the nonionic
intermediate. For example, if half of the terminal primary or secondary
hydroxyl groups
of the nonionic intermediate are reacted with isobutylene oxide, then the
measured
hydroxyl number will be about 50% lower in comparison to that of the nonionic
intermediate. It can be seen that the reduction in hydroxyl number is an
indication of the
3 0 extent of incorporation of the isobutylene oxide units. Thus,
determination of the
hydroxyl number is one way of measuring the tertiary hydroxyl group
incorporation into
the nonionic surfactant of the invention. The tertiary group content can also
be directly
CA 02311998 2000-06-20
determined by reaction with hydrogen bromide according to ASTM method E567-76
(1986).
It is preferred that the nonionic surfactant of the invention exhibit a
hydroxyl
number that is lower by at least about 70% in comparison to that of the
nonionic
intermediate. Preferably, the hydroxyl number will be lower by at least about
85%.
Thus, the nonionic surfactant is the reaction product of a nonionic
intermediate and
isobutylene oxide, wherein the nonionic intermediate comprises an alkylene
oxide
homopolymer or a copolymer of two or more different alkylene oxide monomers
and has
a first hydroxyl number, wherein the reaction product has a second hydroxyl
number, and
wherein said second hydroxyl number is at least 70% lower in comparison to
said first
hydroxyl number.
To make the nonionic intermediate, a compound having active hydrogens is used
as a starter molecule, onto which the alkylene oxides are polymerized. Active
hydrogens
are those that will react with the basic catalyst and the alkylene oxides to
undergo
polymerization. Examples well known in the art include the hydrogen on
functional
groups such as -OH, -NHR, -SH, -COOH, and -C(O)NHR, where R is hydrogen,
alkyl,
aryl, or aralkyl. Thus, suitable starter molecules include alcohols, amines,
mercaptans,
carboxylic acids, carboxylic amides, and mixtures thereof. The starter
molecules can be
monofunctional, or they can be difunctional, trifunctional, or higher
functional, or they
3 p can be mixtures of the above. They can have from 1 to up to about 50
carbon atoms, and
preferably have from 1 to about 24 carbon atoms.
Suitable alcohols useful as starter molecules can be either monomeric or
polymeric, and can be monofunctional or polyfunctional. Mixtures of alcohols
can also
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CA 02311998 2000-06-20
be used. Monomeric alcohols include mono-alcohols, diols, triols, and higher
functional
alcohols, and may be aliphatic or aromatic. Non-limiting examples include mono-
alcohols such as methanol, ethanol, phenol, octylphenol, nonylphenol, decyl
alcohol,
dodecyl alcohol, stearyl alcohol, and oleyl alcohol; diols such as ethylene
glycol,
propylene glycol, 1,3-propanediol, neopentylglycol, 1,2-butanediol, and 1,4-
butanediol;
triols such as glycerol and trimethylolpropane; tetrols such as
ditrimethylolpropane and
pentaerythritol; and higher functional alcohols such as sorbitol, glucose,
fructose, and
sucrose. Other suitable alcohols are those which also contain an amino group.
Examples
are triethanolamine, N,N-dialkylalkanolamines, and tripropanolamine.
Polymeric alcohols are also useful in the present invention. Polymeric
alcohols
are polymers that have a multiple hydroxyl functionality. The most commonly
used
polymeric alcohols are the oligomers and polymers of ethylene oxide and
propylene
oxide. Oligomers include diethylene glycol, triethylene glycol, tetraethylene
glycol,
dipropylene glycol, and tripropylene glycol. Polymers include polyethylene
glycol and
polypropylene glycol. Other polymeric alcohols would include any polyether
polyol
made by polymerization of an alkylene oxide or mixture of alkylene oxides onto
a starter
molecule. That is, any polyether polyol, may be used anew as a starter
molecule in a
subsequent base catalyzed polymerization reaction to form a polyoxyalkylene
intermediate.
3 0 Amines and alkylamines may also be used as starter molecules. They may be
monoamines, diamines, triamines, or higher functional amines. They may be
aliphatic or
aromatic. Examples include ethylamine, aniline, dodecyl amine, decyl amine,
oleyl
7
CA 02311998 2000-06-20
amine, isopropyl amine, ethylene diamine, toluene diamine, propane diamine,
triethylene
diamine, and tetraethylene triamine.
Starter molecules may have both -OH and -NHR groups. Examples include
alkanolamines such as N-isopropylethanolamine, propanolamine, and
dipropanolamine.
Useful carboxy functional starter molecules include molecules with the general
formula X-R-COOH, where R is an alkyl or alkenyl group having about 8 to 20
carbon
atoms, and X is either a hydrogen (in which case the starter molecule is a
monocarboxylic
acid) or a carboxyl group (in which case the starter molecule is a
dicarboxylic acid).
Examples include decanoic acid, dodecanoic acid, oleic acid, stearic acid,
palmitic acid,
adipic acid, dodecanedioic acid, hexadecanedioic acid, and the like.
N-alkyl fatty amides may also be used as starter molecules. In this case, they
have
the general formula R-C(O)NHR', where R is an alkyl group having 8 to 20
carbon atoms
and where R' is hydrogen or an alkyl, aryl, hydroxyalkyl, or aralkyl groups
having 2 to
20 carbon atoms. Examples are the fatty acid ethanolamides, which have both a -
OH and
a -C(O)NHR' functionality.
As mentioned above, the nonionic intermediate can be a copolymer of two or
more different alkylene oxides. A preferred nonionic intermediate comprises
two or more
blocks of polyalkyleneoxide adjacent to or in series with one another, wherein
adjacent
blocks differ from one another in the relative mole fraction of the alkylene
oxide
3 0 monomers in the block. The blocks can be heteric, or they can consist
essentially of a
single alkylene oxide. Alkylene oxides useful in forming the nonionic
intermediate
include but are not limited to ethylene oxide, propylene oxide, 1,2-butylene
oxide, 2,3-
butylene oxide, 1,2-hexylene oxide, and styrene oxide. Higher alkyl epoxides
such as
8
CA 02311998 2000-06-20
those with 5 or more carbon atoms can also be useful. The number of blocks and
the
relative composition of the blocks are to be chosen according to the
properties desired in
the surfactant of the invention. The sizes of the blocks and the relative
composition can
be varied to affect the surface tension, dispersing power, cloud point,
solubility in water,
relative hydrophobicity, and other physical properties, as is known by one
skilled in the
relevant art.
The nonionic intermediate can comprise blocks made from essentially all
ethylene
oxide or essentially all propylene oxide. In this case, the blocks consist of
polyoxyethylene and polyoxypropylene, respectively. For example, diblock
surfactants
made from a nonionic intermediate comprising a polyoxyethylene block and an
adjacent
polyoxypropylene block are useful in the invention, as are triblock nonionic
intermediates
comprising, in series, a polyoxyethylene block, a polyoxypropylene block, and
another
polyoxyethylene block. Alternatively, the triblock nonionic intermediate can
comprise,
in series, a polyoxypropylene block, a polyoxyethylene block, and another
polyoxypropylene block. Suitable triblock nonionic intermediates are
commercially
available from BASF Corporation as the Pluronic~ surfactants.
Examples of diblock nonionic intermediates useful in the invention are the
alcohol
initiated diblock polymers, where the alcohol starter molecule has 1 to about
24 carbon
atoms, preferably 6 carbons or greater, onto which is polymerized a first
block with a first
3 0 alkylene oxide composition, followed by a second block with a second
alkylene oxide
composition. Another class of useful nonionic intermediates is the alcohol
initiated
triblock polymers, where the alcohol starter molecule has 1 to about 24 carbon
atoms,
9
CA 02311998 2000-06-20
preferably 6 carbons or greater, onto which is polymerized a first block with
a first
alkylene oxide composition, followed by a second block with a second alkylene
oxide
composition, followed by a third block with a third alkylene oxide
composition. The size
and relative composition of the first, second, third, and subsequent blocks
are chosen
according to the properties desired in the surfactant. Typically, the blocks
comprise from
1 to about 80, preferably from 1 to about 30 alkylene oxide units, and can
comprise a
single alkylene oxide or a heteric mixture of alkylene oxides. A useful class
of
surfactants can be made when the first block consists essentially of ethylene
oxide, and
the second block consists essentially of propylene oxide. Another useful class
of
surfactants is obtained when the first block consists essentially of propylene
oxide, and
the second block consists essentially of ethylene oxide.
The surfactants of the invention, which have at least 70% terminal tertiary
hydroxyl groups, have surprisingly been found to be stable in alkaline aqueous
solutions,
and stable when in direct contact with caustic materials. Thus, they can be
combined
with a variety of these materials, either as dry admixtures or as aqueous
solutions.
Among these materials are alkali metal hydroxides, alkali metal carbonates,
alkali metal
bicarbonates, alkali metal triphosphates, alkali metal phosphates, and alkali
metal
silicates. Other examples of caustic materials include the alkaline earth
metal salts of the
anions listed above. Such alkaline materials are typically used in cleaning
and other
3 0 compositions. Examples of such compositions can be found in The Chemical
Formulary,
vol. XXXIII, H. Bennett ed. (Chemical Publishing Company, New York 1996), pp.
172-
175, the disclosure of which is hereby incorporated by reference. The
invention thus
provides surfactants, defoamers, and other functional additives that can
advantageously
CA 02311998 2000-06-20
be used together with the caustic materials present in typical cleaning
compositions
without diminution of the additives' effectiveness over time.
Thus, the caustic stability of surfactant compositions containing a caustic
material
is improved when the surfactant composition incorporates a nonionic surfactant
as
described above. A method for improving the caustic stability of such
compositions
comprises providing a surfactant composition containing a caustic material and
a
s~factant, and substituting, for the surfactant of the composition, a nonionic
surfactant
comprising an alkylene oxide homopolymer or copolymer moiety and terminal
hydroxyl
groups, wherein at least 70% of the terminal hydroxyl groups are tertiary
hydroxyl
groups.
Typically, in the compositions of the present invention, the surfactant will
be
present at a level of from about 0.1 to about 20%, preferably from about 0.5
to about 10%
by weight of the composition. When the composition is a powder composition,
the
caustic material will generally comprise most, and can comprise essentially
all of the
remainder, so that the caustic material is up to about 99.5% of the total
weight. Aqueous
surfactant compositions of the present invention likewise will comprise from
about 0.1 to
about 20%, preferably from about 0.5 to about 10% of the nonionic surfactant
by weight,
but water can be as high as 80% by weight, with the caustic material
preferably
comprising most, if not essentially all of the rest. Typically, these
compositions are used
3 0 in cleaning at a dilution of about 1 to about 16 ounces per gallon of
water.
In particular, low foaming surfactants or surfactants with defoaming
properties
can be prepared according to the invention. Such low foamers or defoamers can
be
advantageously used in highly alkaline environments with the result that the
low foaming
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CA 02311998 2000-06-20
property or the defoaming effectiveness does not diminish over time. Thus,
another
embodiment of the invention provides a method for defoaming alkaline aqueous
systems
by providing as a defoaming agent a nonionic surfactant made as described
above. As
used here and in the claims, the terms "defoaming" and "defoaming agent" are
intended
to cover low foaming and low foaming agents as well, respectively.
A useful defoamer comprises a nonionic intermediate that is a triblock
surfactant,
onto which isobutylene oxide is polymerized as described above. Suitable
defoamers can
be obtained when the triblock surfactants have number average molecular
weights of
between 1000 and 15000, preferably between 1000 and 6500, and most preferably
between 1000 and 5000. The percent by weight of polyoxyethylene in the
triblock
surfactant is less than about 50%, preferably less than about 30%. Suitable
defoamers in
this class are available commercially, for example, as Pluronic~ surfactants,
sold by
BASF Corporation. Especially useful are the triblock surfactants that comprise
an inner
block of polyoxyethylene and two outer blocks of polyoxypropylene. These
surfactants
are also commercially available from BASF Corporation as the Pluronic~ R
series of
surfactants.
Other useful defoamers include alcohol initiated diblock and triblock
polyoxyalkylenes, such as the Plurafac~, Poly-Tergent~, or Macol~ surfactants,
commercially available from BASF Corporation. Useful surfactants in this
series range
3 0 in number average molecular weight of from about 340 to about 5000. The
polyoxyethylene content of these surfactants will generally be below about 55
% by
weight.
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CA 02311998 2000-06-20
F.X~1MPT ,F
Protein Soil Defoaming Tests
The background of the use of these tests can be found in LR. Schmolka and T.M.
Kaneko, "Protein Soil Defoaming in Machine Dishwashers," J.Am. Oil Chem. Soc.,
45,
No. 8, pp. 563-566 (1968).
The object of these tests is to study the effects of milk and egg soils upon
the
foam control performance of a dishwasher detergent. The conditions and
equipment used
in these tests are as follows:
The dishwasher is a KitchenAid, Model LJMP-4, equipped with an electronic
counter with a graph recorder for measuring the rotations of the machine
dishwasher's
spray arm and a thermocouple for monitoring the wash solution temperature in
the sump.
(An electric counter and dial thermometer can be substituted for the graph
recording
system and thermocouple.)
The egg soil used in the defoaming tests is 15 ml stirred, raw, whole egg.
The detergent sample size to be tested is 20g.
Once the operating temperature is reached, the spray arm rotation rate in
revolutions per minute (rpm) is recorded for the main wash cycle in the
following
manner. As the dishwasher door is closed, the electronic counter, which
indicates the
number of revolutions made by the spray arm, is turned on along with a graph
recorder
which permanently records the revolutions per minute throughout the test. The
rpm of
3 0 the spray arm at the first minute and the second minute are obtained from
the graph. The
average of the two is used as the spray arm rotation rate. The readings in rpm
are
13
CA 02311998 2000-06-20
inversely proportional to the amount of foam produced. Hence, the higher the
reading,
the better the milk, egg, or soil foam control of the detergent
Example 1
This is about a 3200 molecular weight triblock copolymer of ethylene oxide and
propylene oxide with about 25% by weight of polyethylene oxide and a hydroxyl
number
of 35. The terminal hydroxyl groups are mostly secondary.
Example 2
This is a commercially available alkyl capped alcohol oxyalkylate surfactant
recommended for caustic stability.
Example 3
To a suitable reaction vessel was added 150 grams of the product of Example 1.
It is a triblock copolymer of ethylene oxide and propylene oxide having a
hydroxyl
number of 35. Then, 1.60 grams of potassium t-butoxide was added and the
mixture
heated to 105°C. After one hour, a total of 10.2 grams of isobutylene
oxide was added
slowly dropwise. After 20 hours, the reaction mixture was cooled to
90°C, and 0.45
grams of acetic acid was added in one portion. The hydroxyl number of the
product was
3, indicating 92% reaction of primary and secondary hydroxyl groups.
Samples for evaluating caustic stability were made by adding 0.60 grams of the
products of Examples 1, 2, and 3, respectively, directly to 19.40 grams solid
sodium
3 0 hydroxide beads and mixing thoroughly. The samples were placed in an oven
at 100°F
and periodically evaluated for discoloration and protein soil defoaming.
Protein Soil Defoaming Evaluation
14
CA 02311998 2000-06-20
The foam characteristics of the Samples were determined by measuring the spray
arm rotation of an automatic dishwashing machine during a washing cycle in
with raw
egg soil was present. The machine was started and allowed to fill partially
with water,
stopped, the sample and 15 grams of raw egg soil added, then started and
allowed to fill
completely. The water temperature was about 100°F. After the washing
cycle magnetic
sensor started, the spray arm rotation was measured and expressed as a
percentage
relative to the rotation rate measured with water only. This spray arm
efficiency is
abbreviated in the table as "SAE."
SAMPLE PLE
OF EXAM
TIME 1 2 3
(WEEKS)
COLOR SAE COLOR SAE COLOR SAE
0 WHITE 97 WHITE 71 WHITE 100
2 LIGHT 72 WHITE 73 WHITE 100
BROWN
4 BROWN --- WHITE 71 WHITE 100
6 BROWN --- WHITE 68 WHITE 98
It is seen that the Sample of Example 1 discolors over a period of weeks,
turning
from the original white to brown by 4 weeks. Concomitant with the discoloring,
the
Sample also diminishes in defoaming effectiveness, as shown by the decrease in
SAE
from 97 to 72 in only two weeks.
By contrast, it is seen that the Sample of Example 3, which differs from
Example
3 0 1 only in that it contains about 92% terminal tertiary hydroxyl groups,
exhibits stability
over the six-week period of the test, in that the color does not change from
the original
white, and the SAE remains high. It is thus seen to be equivalent in color
performance to
CA 02311998 2000-06-20
the Sample of Example 2, which is a commercially available caustic stable
surfactant. It
is also seen that the defoaming effectiveness of Example 3 is just as stable
over time as
that of Example 2, and is, in fact, at a higher level.
16
