CA2311998A1 - Caustic stable nonionic surfactant compositions and methods for their use - Google Patents

Abstract

There is provided a surfactant composition resistant to degradation, comprising a caustic material and a nonionic surfactant, wherein the nonionic surfactant is the reaction product of a nonionic intermediate and isobutylene oxide. The nonionic intermediate preferably comprises a copolymer of two or more alkylene oxide monomers. The reaction product has a hydroxyl number that is at least 70% lower in comparison to the hydroxyl number of the nonionic intermediate.

Description

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 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 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 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 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 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 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 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 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, 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.

175, the disclosure of which is hereby incorporated by reference. The invention thus provides surfactants, defoamers, and other functional additives that can advantageously 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 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.

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 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 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

(WEEKS) COLOR SAE COLOR SAE COLOR SAE

BROWN

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 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.

Claims (28)

1. A surfactant composition, comprising a) a caustic material, and b) 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.

2. A surfactant composition as defined in claim 1, wherein at least 85% of the terminal hydroxyl groups are tertiary hydroxyl groups.

3. A composition as defined in claim 1, wherein the nonionic surfactant b) 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.

4. A composition as defined in claim 3, wherein the second hydroxyl number is at least 85% lower in comparison to the first hydroxyl number.

5. A composition as defined in claim 4, wherein the alkylene oxide monomers are selected from the group consisting of ethylene oxide, propylene oxide, and butylene oxide.

6. A composition as defined in claim 3, wherein the 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 monomers in the block.

7. A composition as defined in claim 6, wherein the nonionic intermediate comprises adjacent blocks of polyethyleneoxide and polypropyleneoxide.

8. A composition as defined in claim 3, wherein the nonionic intermediate is a triblock copolymer of ethylene oxide and propylene oxide.

9. A composition as defined in claim 3, wherein the nonionic intermediate is selected from the group consisting of a higher alcohol initiated triblock polymer of ethylene oxide and propylene oxide, a higher alcohol initiated diblock polymer of ethylene oxide and propylene oxide, and mixtures thereof, wherein the higher alcohol is an aliphatic alcohol having 6 or more carbon atoms.

10. A composition as defined in claim 1, wherein the caustic material a) is selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, alkali metal bicarbonates, alkali metal triphosphates, alkali metal phosphates, alkali metal silicates, alkaline earth metal hydroxides, alkaline earth metal carbonates, alkaline earth metal bicarbonates, alkaline earth metal triphosphates, alkaline earth metal phosphates, alkaline earth metal silicates, and mixtures thereof.

11. A method for improving the caustic stability of surfactant compositions, composing providing a surfactant composition containing a surfactant and a caustic material 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.

12. A method as defined in claim 11, wherein at least 85% of the terminal hydroxyl groups are tertiary hydroxyl groups.

13. A method as defined in claim 11, wherein 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.

14. A method as defined in claim 13, wherein the second hydroxyl number is at least 85%
lower in comparison to the first hydroxyl number.

15. A method as defined in claim 14, wherein the alkylene oxide monomers are selected from the group consisting of ethylene oxide, propylene oxide, and butylene oxide.

16. A method as defined in claim 13, wherein the 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 monomers in the block.

17. A method as defined in claim 16, wherein the nonionic intermediate comprises adjacent blocks of polyethyleneoxide and polypropyleneoxide.

18. A method as defined in claim 16, wherein the nonionic intermediate is a triblock copolymer of ethylene oxide and propylene oxide.

19. A method as defined in claim 13, wherein the nonionic intermediate is selected from the group consisting of a higher alcohol initiated triblock polymer of ethylene oxide and propylene oxide, a higher alcohol initiated diblock polymer of ethylene oxide and propylene oxide, and mixtures thereof, wherein the higher alcohol is an aliphatic alcohol having 6 or more carbon atoms.

20. A method for defoaming alkaline aqueous solutions, comprising providing a foaming alkaline aqueous solution; and adding to the solution as a defoaming agent 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.

21. The method of claim 20, wherein at least 85% of the terminal hydroxyl groups are tertiary hydroxyl groups.

22. The method of claim 20, wherein 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.

23. A method as defined in claim 22, wherein the second hydroxyl number is at least 85%
less in comparison to the first hydroxyl number.

24. A method as defined in claim 22, wherein the alkylene oxide monomers are selected from the group consisting of ethylene oxide, propylene oxide, and butylene oxide.

25. A method as defined in claim 22, wherein the 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 monomers in the block.

26. A method as defined in claim 22, wherein the nonionic intermediate comprises adjacent blocks of polyethyleneoxide and polypropyleneoxide.

27. A method as defined in claim 26, wherein the nonionic intermediate is a triblock copolymer of ethylene oxide and propylene oxide.

28. A method as defined in claim 26, wherein the nonionic intermediate is selected from the group consisting of a higher alcohol initiated triblock polymer of ethylene oxide and propylene oxide, a higher alcohol initiated diblock polymer of ethylene oxide and propylene oxide, and mixtures thereof, wherein the higher alcohol is an aliphatic alcohol having 6 or more carbon atoms.