Water-indicating paste composition

Abstract

A visual indicator paste composition capable of undergoing a detectable color change upon contact with an aqueous liquid is provided. The paste composition comprises an indicator dye capable of changing color in a pH range of about 3 to about 11; an inorganic base capable of reacting with water to convert to a more basic substance; a liquid carrier (e.g., a polyalkylene glycol carrier); optionally, a gelling agent, such as silica gel; and a proton-donating compound, such as a carboxylic acid or organic sulfonic acid. The paste composition is particularly adapted for detecting water levels at the bottom of tanks and distribution systems containing fuels, such as gasoline, by undergoing a distinct, detectable color change without bleeding or spillage upon contact with aqueous liquids when applied to a measurement probe. The paste composition exhibits extended shelf life and improved water resistance.

Description

Technical Field

[0001] The present invention relates to a stabilized visual indicator paste composition and its use for detecting the presence, particularly the level, of an aqueous liquid when mixed with a hydrocarbon, such as gasoline, oil or other fuel and petroleum fractions. More particularly, the present invention relates to a stabilized visual indicator paste composition that can undergo a color change upon contact with an aqueous liquid that may be present in small amounts as a separate phase in hydrocarbon storage tanks, delivery vehicles, distribution systems, etc. The composition of the present invention is used for determining the water level at the bottom of gasoline storage and transport tanks in order to determine the amount of water present in a tank that is partially filled with hydrocarbon, and is particularly adapted for use when the water contains oxygenated components such as ethers and alcohols.

Background Art

[0002] Pastes compositions capable of detecting the level or presence of water have been disclosed in the prior art.

[0003] For example, U.S. Patent No. 4,699,885 discloses a visual indicator paste composition that produces a detectable color change upon contact with an aqueous liquid, the composition comprising a water-soluble indicator dye capable of changing color in a pH range of about 7 to 11, and an insoluble inorganic base in the form of a caustic powder dispersed in a liquid carrier that can absorb water but does not leach rapidly by water or hydrocarbon. Chinese Patent Application Publication No. CN103173206 discloses a similar paste composition. However, it has been found that the water indicator pastes disclosed in the said applications may change color during storage due to the introduction of trace amounts of water from one or more sources. Thus, water may enter the paste when high humidity conditions exist during the manufacture or storage of the paste, or may be absorbed by the paste while the container is open each time the user applies the paste. In addition, water may be introduced together with raw materials used during the formulation of the paste, such as the liquid carrier.

[0004] U.S. Patent No. 4,717,671 describes a visual indicating paste composition similar to the composition disclosed in U.S. Patent No. 4,699,885. The composition achieves an extended shelf life and improved water resistance by including a moisture suppressing amount of a boron-containing compound, such as a borate ester, that is miscible or soluble in a polyalkylene glycol carrier and can be hydrolyzed upon contact with water to yield boric acid or a salt thereof. The inventors report that "all attempts to use other added organic compounds including acids, anhydrides, salts, oxides, molecular sieve adsorbents, and active metal compounds in place of such boron-containing compounds have failed."

[0005] U.S. Patent No. 6,376,250B1 describes the incorporation of aluminum isopropoxide as a water scavenger into a visual indicating paste composition that includes a liquid carrier that is a high molecular weight polyol, a caustic powder selected from alkaline earth oxides, a gelling agent, a surfactant, a filler, an indicator dye, and a neutral dye.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0007] Despite the foregoing developments, there remains a need for alternative methods of effectively stabilizing water-indicating paste compositions against the adverse effects of small amounts of moisture that such paste compositions may come into contact with as a result of repeated exposure to the ambient atmosphere during manufacture, storage, and / or repeated opening of the containers in which they are stored over a period of time. [Means for solving the problem]

[0008] Embodiments of the present invention provide stabilized visual indicating pastes that exhibit extended shelf life and improved water resistance, while at the same time being characterized by low solubility in aqueous liquids and hydrocarbons and good adhesion to the substrate to which they are applied. Other aspects of the present invention include methods of making such stabilized visual indicating pastes.

[0009] In another embodiment of the present invention, a measurement probe having a stabilized visual indicating composition coated thereon is provided that is useful for determining the level of aqueous liquids (e.g., water or liquids containing water in combination with oxygenated ingredients, such as alcohols and ethers) at the bottom of hydrocarbon-containing tanks and distribution systems. Methods of utilizing such probes to measure the level of such aqueous liquids in containers are also provided.

[0010] It has now been discovered that paste compositions comprised of (i) an indicator dye capable of changing color in a pH range between about 3 and about 11, (ii) an inorganic base (typically dispersed in one or more polyalkylene glycol-based liquid carriers), and (iii) an optional gelling agent, when containing relatively small amounts of one or more proton-donating compounds having a pKa of 12 or less, exhibit significantly improved shelf life and water resistance compared to pastes lacking such proton-donating compounds. This discovery was particularly surprising in light of the teachings of U.S. Patent No. 4,578,357, in which attempts to stabilize similar paste compositions against the adverse effects of water using acids such as adipic acid and stearic acid were unsuccessful.

Mode for Carrying Out the Invention

[0011] According to the present invention, any proton-donating compound having a pKa of 12 or less, or a combination of such proton-donating compounds, can be used as a stabilizer in the paste composition of the present invention. According to other embodiments, the pKa of the proton-donating compound is 11 or less, 10 or less, 9 or less, or 8 or less. In other embodiments, it is preferable that the pKa of the proton-donating compound is -3 or more, -2 or more, -1 or more, or 0 or more. For example, the pKa of the proton-donating compound may be in the range of -3 to 12, -2 to 10, or 0 to 8. When the proton-donating compound can donate two or more protons (for example, in the case of a dicarboxylic acid such as citric acid), the pKa used herein refers to the lowest pKa value, i.e., pKa1. The pKa of a compound can be determined by conventional methods known in the art, and many different information sources describing the pKa of known compounds are readily available.

[0012] In certain other embodiments of the present invention, it may be advantageous for the proton-donating compound or a combination of such compounds to be completely miscible or soluble with respect to the liquid carrier (for example, polyalkylene glycol) component of the paste composition.

[0013] According to certain aspects of the present invention, the proton-donating compound is at least partially water-soluble. However, preferably, the water-solubility of the proton-donating compound is limited (i.e., the proton-donating compound is not freely soluble in water in any proportion). For example, the proton-donating compound may have a solubility of at least 0.01 g / L or at least 0.05 g / L in water at 25°C. In other examples, the proton-donating compound may have a solubility of 75 g / L or less or 60 g / L or less in water at 25°C.

[0014] The proton-donating compound is preferably an organic compound, such as an organic acid. Acids suitable for the purposes of the present invention include, but are not limited to, carboxylic acids (organic compounds containing one or more -COH groups) and organic sulfonic acids (organic compounds containing one or more -SOH groups). The organic acid may be an aliphatic organic acid (meaning that the acid functional group is substituted on an aliphatic carbon atom) or an aromatic organic acid (meaning that the acid functional group is substituted on an aromatic carbon atom). It is also possible to use organic acids containing one or more aliphatic moieties and one or more aromatic moieties.

[0015] Examples of suitable proton-donating compounds useful in the present invention include, but are not limited to, C4 to C24 aliphatic carboxylic acids, including C6 to C24 aliphatic monocarboxylic acids (which may be saturated or unsaturated, linear or branched, or contain one or more aliphatic ring structures) and C4 to C8 aliphatic dicarboxylic acids (which may be saturated or unsaturated, linear or branched), as well as C6 to C18 alkylated arylsulfonic acids (i.e., compounds in which a C6 to C18 alkyl group and a sulfonic acid group are attached to an aromatic ring, e.g., a benzene ring), such as nonanoic acid, dodecylbenzenesulfonic acid, adipic acid, succinic acid, and combinations thereof.

[0016] A proton-donating compound, or a combination of proton-donating compounds, is used in the paste composition in an amount sufficient to exhibit a desired level of stabilization or inhibition against moisture. At the same time, such an amount should not be excessive enough to inhibit the ability of the paste composition to change color when used for the intended purpose of detecting an aqueous liquid within a desired period (typically less than 1 minute when contacted with such an aqueous liquid at 25°C). Therefore, according to certain embodiments, the paste composition contains at least one proton-donating compound in an amount effective to stabilize the paste composition against color change when the paste composition is exposed to air at 25°C and 70% relative humidity for at least 10 minutes. In a further embodiment, the paste composition is composed of at least one proton-donating compound in an amount effective to allow the paste composition to exhibit a color change within 1 minute or within 30 seconds after contact with pure water at 25°C. In certain embodiments of the present invention, both of the aforementioned criteria may be satisfied (i.e., the paste composition contains at least one proton-donating compound in an amount effective to both stabilize the paste composition against color change when the paste composition is exposed to air at 25°C and 70% relative humidity for at least 10 minutes and allow the paste composition to exhibit a color change within 1 minute or within 30 seconds after contact with pure water at 25°C). Generally, the proton-donating compound may be present in the paste composition of the present invention at a concentration in the range of about 0.01% to about 5% based on the total mass of the paste composition. The amount of the proton-donating compound may be appropriately adjusted based on factors such as the specific proton-donating compound selected, the pKa value of the proton-donating compound, and the type and amount of the inorganic base.

[0017] According to certain embodiments, at least one first inorganic base and at least one proton-donating compound are present in an amount effective to make the mass ratio of the first inorganic base to the proton-donating compound from 1:1 to 100:1. According to other embodiments, at least one proton-donating compound is present in the paste composition in a stoichiometric excess relative to the total amount of water and the second inorganic base present when the paste composition is prepared.

[0018] The stabilized visual indicator paste composition of the present invention changes color generally within about 60 seconds or within about 30 seconds, usually within about 5 to 15 seconds, depending on the indicator dye used, upon contact with water or an aqueous liquid, i.e., a liquid containing water, such as an oxygenated hydrocarbon containing water, at 25°C. The oxygenated hydrocarbon may be selected from, for example, lower alcohols, illustratively methanol, ethanol, tertiary butyl alcohol, secondary butyl alcohol and mixtures thereof; lower polyols, such as alkylene glycols, and lower ketones, such as acetone and methyl tertiary butyl ether. The term "aqueous liquid" is used herein to designate a substance having chemical properties similar to such water, as distinguished from an "oily liquid" that does not cause a color change in the composition of the present invention, i.e., a fuel, petroleum or hydrocarbon oil. The aqueous liquid mentioned above may contain up to about 95% oxygenated hydrocarbon and typically can be obtained from the use of oxygenated components leaching from hydrocarbons into the aqueous layer, such as in gasoline. According to certain embodiments, the aqueous liquid is in the form of a homogeneous liquid or solution in which water is dissolved or solubilized in one or more non-aqueous components, such as oxygenated components, or one or more non-aqueous components are dissolved or solubilized in water.

[0019] The indicator dyes used in the paste composition of the present invention are preferably water-soluble dyes and are readily available as fine anhydrous crystalline powders from commercial sources. Generally, the dye particles exhibit a diameter of about 200 microns or less. These dyes are characterized in that when the paste composition is brought into contact with water, they can cause a change in the color of the paste composition within a pH range of about 3 to about 11. Typically, the initially formulated paste composition is characterized by having a first pH value and a first color as a result of the color of the indicator dye at the first pH value. When the paste composition is brought into contact with an aqueous liquid, the water present in the aqueous liquid interacts with the first inorganic base (e.g., calcium oxide) present in the paste composition to form a second inorganic base (e.g., calcium hydroxide) that is more basic than the first inorganic base. The formation of the second inorganic base results in an increase in the pH value, i.e., the paste composition comes to exhibit a second pH value that is higher than the first pH value. The second pH value is high enough to change the color of the indicator dye from the first pH value. For example, the indicator dye may be colorless at the first pH value but blue or purple at the second (higher) pH value.

[0020] Such indicator dyes are usually used as components of the paste composition in an amount sufficient to exhibit the desired color change. Generally, such dyes may be used at a concentration in the range of about 0.05 to about 5 percent, preferably about 0.1 to about 3 percent, based on the total mass of the paste composition. Representative indicator dyes that can be used as components in the composition of the present invention include, but are not limited to, phenolphthalein, o-cresolphthalein, p-naphtholbenzein, ethyl bis(2,4-dinitrophenol)acetate, thymolphthalein, Nile blue A, cresol red, bromophenol blue, and thymol blue. The indicator dye used may be selected based on its regulatory status and / or toxicity characteristics.

[0021] The inorganic base used as a component of the visual indicator paste composition of the present invention should be one that does not dissolve or ionize to any significant extent in the liquid carrier but is readily soluble in water (either directly or as a result of reaction with water, as in the case of calcium oxide, which reacts with water to form calcium hydroxide). According to embodiments of the present invention, the inorganic base is present in the paste composition in the form of finely divided particles, e.g., as a powder. According to certain embodiments of the present invention, finely divided particles of the inorganic base may be dispersed in the liquid carrier. In general, anhydrous solid forms of alkaline earth oxides, hydroxides, or mixtures thereof, or any compounds that generate alkaline earth oxides or hydroxides in situ, such as alkaline earth hydrides, are suitable for use in the paste compositions of the present invention. These materials may be in the form of finely divided, technical-grade crystalline powders and are readily available from commercial sources. Typical inorganic bases that can be used in accordance with the present invention include calcium oxide, calcium hydroxide, strontium oxide, strontium hydroxide, barium oxide, barium hydroxide, magnesium oxide, magnesium hydroxide, and hydrides of these metals, such as calcium hydride. Alkaline earth oxides, such as calcium oxide (CaO), are particularly suitable for use in the present invention.

[0022] The selection of the inorganic base will depend, in part, on the particular indicator dye or combination of indicator dyes used in formulating the paste composition. For example, the inorganic base may be selected to impart to the initially formulated paste composition a pH at which an indicator dye also present in the paste composition is a first color (or colorless).

[0023] Generally, the inorganic base is used in a concentration ranging from about 1 to about 25 weight percent of the paste composition, preferably between about 5 and about 20 weight percent, to provide the desired water-sensitive properties characteristic of the paste composition of the present invention.

[0024] As a vehicle for the paste composition of the present invention, a liquid carrier is used that can absorb water but is not easily leached by water or by hydrocarbons with which the paste composition will come into contact during its intended use. In this context, the term "liquid carrier" refers to a carrier that is liquid at 25°C. Any organic compound, or mixture thereof, that exhibits such properties and is inert to other composition ingredients can be used. Other desirable properties of the liquid carrier are that it has a sufficiently high viscosity for a good paste consistency, a low freezing point, and does not inhibit the fairly rapid color reaction of the indicator dye, i.e., within about 2 minutes, upon contact of the paste composition with an aqueous liquid. Particularly suitable liquid carriers that can be used include aliphatic polyols, alkylene glycols, and polyalkylene glycols with a molecular weight sufficiently high to prevent dissolution of the composition in the water / hydrocarbon environment in which the visual indicator paste composition will be used. Generally, polyols, glycols, and mixtures thereof having a number-average molecular weight of at least about 75 g / mol are useful as liquid carriers in the compositions of the present invention. Exemplary polyols that can be used in the compositions of the present invention include 1,4-butanediol; 1,3-butanediol; hexylene glycol; 1,2,6-hexanetriol; and 1,6-hexanediol. Polyalkylene glycols typically contain between about 2 and 4 carbon atoms in each alkylene chain unit of the polyalkylene glycol (e.g., the alkylene chain unit may be an oxyethylene, oxypropylene, and / or oxybutylene chain unit). Exemplary polyalkylene glycols that can be used include polyethylene glycol, polypropylene glycol, polyethylene / propylene glycol (random or block), and polybutylene glycol having a number average molecular weight (as determined by gel permeation chromatography) between about 200 and about 4,000 g / mol. As will be apparent to those skilled in the art, such polyols and glycols are commercially available products and can be used alone or in mixtures with or without other conventional liquid carriers, and when used as a mixture, the mixtures are used to obtain the optimal hydrophilic / hydrophobic balance. Polypropylene glycol and polyethylene glycol are commercially available products. Combinations or mixtures with recall are used in certain embodiments of the present invention. Generally, the liquid carrier is used in an amount of at least about 40 weight percent, generally between about 50 and about 90 weight percent, based on the total weight of the paste composition. It is used in an amount between about 60 and 80 percent of the total weight of the paste composition. Polyalkylene glycols having a number average molecular weight between about 200 and 1500 g / mol (especially polyethylene glycol and polypropylene glycol, including combinations thereof) exhibit particularly desirable properties and are therefore preferred for use in the compositions of the present invention.

[0025] If desired, a gelling agent or combination of gelling agents that functions as a thickening agent and / or color stabilizer and is inert with respect to the other raw materials of the paste composition may optionally be used as an additional component of the paste composition of the present invention. The purpose of using such a gelling agent is to delay leaching and gel the composition. Any known substance that has a color other than the color that inhibits the visual detection provided by the paste composition of the present invention in its intended use and that helps to exhibit the indicated thickening properties and color stabilization can be used. Exemplary suitable gelling agents used as components of the paste composition of the present invention include inert inorganic fillers or diluents such as talc, clay, diatomaceous earth, calcium silicate, silica, fumed colloidal silica, alumina, pyrophyllite, calcite, or mixtures of these or other finely divided solid materials. Generally, when used, the gelling agent is used in an amount up to about 20 weight percent, or more, preferably between about 2 and about 15 weight percent, based on the total weight of the paste composition.

[0026] The compositions of the present invention can be prepared by conventional methods used in the art for making paste compositions. Generally, the components of the composition are conventionally fed into a mixer at room temperature and blended until a uniform, smooth paste is obtained, although it is understood that blending under elevated temperatures or other conditions conventionally used for blending pastes may also be used. Incorporation of the ingredients of the composition is readily accomplished by incorporating the ingredients individually or together by grinding, dry mixing, or blending into a liquid carrier. Thus, the inorganic base, indicator dye, proton-donating compound, and / or gelling agent, if used, may be incorporated before, simultaneously with, or after the incorporation of other ingredients into the liquid carrier. Alternatively, the proton-donating compound may be dissolved in the liquid carrier before incorporating the solid ingredients therein.

[0027] According to a preferred embodiment, the paste composition comprises: a) at least one indicator dye capable of changing color in a pH range between about 3 and about 11; b) at least one inorganic base capable of reacting with water to convert a first inorganic base to a second inorganic base that is more basic than the first inorganic base; c) at least one liquid carrier; d) optionally at least one gelling agent; and e) at least one proton donating compound having a pKa of at most 12, preferably at most 10, more preferably at most 8; The compound can be prepared by a method comprising the step of combining

[0028] In particular, such a method a) combining at least one liquid carrier, at least one indicator dye, and at least one proton donating compound to obtain a first mixture; b) combining the first mixture with at least one inorganic base to obtain a second mixture; c) optionally (but preferably) combining the second mixture with at least one gelling agent to obtain a paste composition; may include:

[0029] Water is advantageously excluded during the preparation of the paste composition. For example, the components of the paste composition may be anhydrous or essentially water-free. According to certain embodiments of the present invention, some of the components of the paste composition may be combined and dried to remove water or reduce the water content before adding additional components of the paste composition. For example, when multiple liquid carriers, such as various polyalkylene glycols, are used to formulate the paste composition, such liquid carriers may be combined and subjected to vacuum stripping with heating to reduce the water content, and then the remaining components (having a sufficiently low water content) may be added. Combining the components of the paste composition may be performed under a dry atmosphere (e.g., dry nitrogen) to prevent absorption of atmospheric moisture into the paste composition. Once the paste composition according to the present invention has been formulated, it may be transferred to a suitable sealable container that can be easily opened to allow dispensing of the paste composition and then resealed to protect the paste composition from moisture exposure. Suitable sealable containers include, for example, tubes, bottles, pails, and drums with caps constructed of suitable materials, such as plastic or metal.

[0030] It should be understood that the paste compositions of the present invention may additionally contain adjuvants well known to those skilled in the art, such as binders, water scavengers, etc. The binder may be materials such as casing gelatin, cellulose derivatives such as carboxymethyl cellulose, spent sulfite liquor, water-dispersible synthetic resins, mineral oil, or equivalent adhesives, all of which are well known in the art.

[0031] The paste compositions of the present invention may additionally comprise one or more surfactants, such as nonionic surfactants (e.g., ethoxylated nonylphenol surfactants), typically in an amount of up to about 5% by weight (e.g., 0.1% to 4% by weight) based on the total weight of the paste composition.

[0032] One or more fillers other than the gelling agent may also be present in the paste composition. Calcium carbonate and gypsum are examples of suitable fillers.

[0033] The present invention provides an easily available and stabilized paste composition that is particularly adapted to identify the water level in a tank for hydrocarbons or other storage or distribution facilities that can be mixed with water or an "aqueous liquid" as previously defined. A particular use of the paste composition of the present invention is found in the measurement of the water level at the bottom of a gasoline storage tank that must be frequently monitored to prevent the delivery of water to the vehicle's gasoline tank. Water at the bottom of a storage or distribution facility for gasoline containing an oxygenated blending component, i.e., an alcohol or an ether, such as methanol, ethanol, tertiary butyl alcohol, methyl t-butyl ether, or a mixture thereof, may contain up to about 90 volume percent alcohol.

[0034] The paste composition according to the present invention may be used as follows to measure the level of an aqueous liquid that may be present in a container. Typically, when a hydrocarbon fuel, such as gasoline, is contaminated with an excess amount of water, phase separation of the contents of a container, such as a tank, used to store or hold the hydrocarbon fuel is observed, an aqueous liquid phase is formed at the bottom of the container, and a hydrocarbon phase (less dense than the aqueous liquid phase) is formed as a separated phase above the aqueous liquid phase. A quantity of the paste composition of the present invention can be placed as a layer (preferably, a thin, uniform layer) on at least one end of a measurement probe. The measurement probe may be elongate and have dimensions configured to reach the bottom of the container while passing through an opening at the top of the container. The measurement probe may be composed of any suitable material resistant to the contents of the container, such as wood, metal, or an engineering thermoplastic. Then, the end of the measurement probe on which the layer of the paste composition is placed can be lowered into the container through the opening of the container and through the contents of the container until it reaches the bottom of the container. When the paste composition contacts the aqueous liquid, the measurement probe is kept in contact with the contents of the container for a time effective to achieve a color change of the paste composition (typically, a period up to 1 or 2 minutes), and then withdrawn from the container and visually inspected for the color change. Since the paste composition visibly changes color only when in contact with water in the form of an aqueous liquid, the presence and depth of any aqueous phase formed in the container can be easily confirmed. If such an aqueous phase is detected, subsequent countermeasures such as sucking out the aqueous phase or emptying and cleaning the container can be taken.

[0035] Exemplary, non-limiting aspects of the present invention can be summarized as follows.

[0036] Aspect 1: A paste composition for causing a detectable color change upon contact with an aqueous liquid, a) at least one indicator dye capable of changing color in a pH range of from about 3 to about 11; b) at least one first inorganic base capable of reacting with water to convert the first inorganic base into a second inorganic base having a higher basicity than the first inorganic base; c) at least one liquid carrier; d) optionally, at least one gelling agent; e) at least one proton-donating compound having a pKa of at most 12, preferably at most 10, more preferably at most 8 A paste composition comprising.

[0037] Aspect 2: The paste composition according to aspect 1, wherein at least one proton-donating compound comprises at least one organic acid.

[0038] Aspect 3: The paste composition according to aspect 1 or 2, wherein at least one proton-donating compound comprises at least one organic acid selected from the group consisting of carboxylic acids, organic sulfonic acids, and combinations thereof.

[0039] Aspect 4: The paste composition according to any one of aspects 1 to 3, wherein at least one proton-donating compound comprises at least one organic acid selected from the group consisting of C6-C24 aliphatic carboxylic acids, C6-C18 alkylated arylsulfonic acids, and combinations thereof.

[0040] Aspect 5: The paste composition according to any one of aspects 1 to 4, wherein at least one proton-donating compound comprises at least one organic acid selected from the group consisting of nonanoic acid, dodecylbenzenesulfonic acid, and combinations thereof.

[0041] Aspect 6: The paste composition according to any one of aspects 1 to 5, wherein at least one proton-donating compound comprises at least one proton-donating compound having a solubility in water at 25 °C of from 0.01 g / L to 75 g / L.

[0042] Aspect 7: The paste composition according to any one of aspects 1 to 6, wherein at least one proton-donating compound has a pKa of at least zero.

[0043] Aspect 8: The paste composition according to any one of Aspects 1 to 7, wherein at least one proton-donating compound is present in a stoichiometric excess with respect to the total amount of water and the second inorganic base present when the paste composition is prepared.

[0044] Aspect 9: The paste composition according to any one of Aspects 1 to 8, comprising at least one proton-donating compound in an amount effective to stabilize the paste composition against color change when the paste composition is exposed to air at 25 °C and 70% relative humidity for at least 10 minutes.

[0045] Aspect 10: The paste composition according to any one of Aspects 1 to 9, comprising at least one proton-donating compound in an amount effective to enable the paste composition to exhibit a color change within 1 minute after contact with water at 25 °C.

[0046] Aspect 11: The paste composition according to any one of Aspects 1 to 10, comprising in total about 0.01 to about 5 mass percent of at least one proton-donating compound.

[0047] Aspect 12: The paste composition according to any one of Aspects 1 to 11, wherein at least one first inorganic base and at least one proton-donating compound are present in amounts effective to make the mass ratio of the first inorganic base to the proton-donating compound from 1:1 to 100:1.

[0048] Aspect 13: The paste composition according to any one of Aspects 1 to 12, wherein at least one indicator dye comprises at least one water-soluble indicator dye.

[0049] Aspect 14: The paste composition according to any one of Aspects 1 to 13, wherein at least one indicating dye comprises at least one indicating dye selected from the group consisting of o-cresolphthalein, phenolphthalein, p-naphtholbenzein, ethyl bis(2,4-dinitrophenol)acetate, thymolphthalein, Nile blue A, cresol red, bromophenol blue, and thymol blue.

[0050] Aspect 15: The paste composition according to any one of Aspects 1 to 14, wherein at least one first inorganic base comprises CaO.

[0051] Aspect 16: The paste composition according to any one of Aspects 1 to 15, wherein at least one liquid carrier comprises at least one polyalkylene glycol.

[0052] Aspect 17: A method for producing a paste composition for causing a detectable color change upon contact with an aqueous liquid, comprising: a) at least one indicating dye capable of changing color in a pH range from about 3 to about 11; b) at least one inorganic base capable of reacting with water to convert the first inorganic base to a second inorganic base that is more basic than the first inorganic base; c) at least one liquid carrier; d) optionally, at least one gelling agent; and e) at least one proton-donating compound having a pKa of at most 12, preferably at most 10, more preferably at most 8 combining steps.

[0053] Aspect 18: a) combining at least one polyalkylene glycol, at least one indicating dye, and at least one proton-donating compound to obtain a first mixture; and b) combining the first mixture with at least one inorganic base to obtain a second mixture; c) optionally combining the second mixture with at least one gelling agent to obtain a paste composition; 18. The method of embodiment 17, comprising:

[0054] Embodiment 19: The method of embodiment 17 or 18, wherein the at least one proton donating compound comprises at least one organic acid.

[0055] Embodiment 20: The method of any one of embodiments 17-19, wherein the at least one proton donating compound comprises at least one organic acid selected from the group consisting of carboxylic acids, organic sulfonic acids, and combinations thereof.

[0056] Embodiment 21: The method of any one of embodiments 17 to 20, wherein the at least one proton donating compound comprises at least one organic acid selected from the group consisting of a C6 to C24 aliphatic carboxylic acid, a C6 to C18 alkylated aryl sulfonic acid, and combinations thereof.

[0057] Embodiment 22: The method of any one of embodiments 17 to 21, wherein the at least one proton donating compound comprises at least one organic acid selected from the group consisting of nonanoic acid, dodecylbenzenesulfonic acid, and combinations thereof.

[0058] Embodiment 23 The method of any one of embodiments 17 to 22, wherein the at least one proton donating compound comprises at least one proton donating compound having a solubility in water at 25° C. from 0.01 g / L to 75 g / L.

[0059] Embodiment 24: The method of any one of embodiments 17 to 23, wherein at least one proton donating compound has a pKa of at least zero.

[0060] Aspect 25: The method of any one of aspects 17 to 24, wherein a stoichiometric excess amount of the at least one proton donating compound is used relative to the total amount of water and the second inorganic base present when the paste composition is prepared.

[0061] Aspect 26: The method according to any one of aspects 17 to 25, wherein when the paste composition is exposed to air at 25 °C and a relative humidity of 70% for at least 10 minutes, at least one proton-donating compound in an amount effective to stabilize the paste composition against color change is used.

[0062] Aspect 27: The method according to any one of aspects 17 to 26, wherein at least one proton-donating compound in an amount effective to enable the paste composition to exhibit a color change within 1 minute after being contacted with water at 25 °C is used.

[0063] Aspect 28: The method according to any one of aspects 17 to 27, wherein the paste composition contains at least one proton-donating compound in a total amount of about 0.01 to about 2 mass percent.

[0064] Aspect 29: The method according to any one of aspects 17 to 28, wherein at least one indicator dye contains at least one water-soluble indicator dye.

[0065] Aspect 30: The method according to any one of aspects 17 to 29, wherein at least one indicator dye contains at least one indicator dye selected from the group consisting of o-cresolphthalein, phenolphthalein, p-naphtholbenzein, ethyl bis(2,4-dinitrophenol)acetate, thymolphthalein, Nile blue A, cresol red, bromophenol blue, and thymol blue.

[0066] Aspect 31: A paste composition obtained by the method according to any one of aspects 18 to 30.

[0067] Aspect 32: A method for detecting an aqueous liquid in a container containing contents, the method including: contacting a measurement probe having a layer of the paste composition according to any one of aspects 1 to 16 or 31 disposed thereon with the contents of the container; withdrawing the measurement probe from the container; and visually inspecting the layer of the paste composition for a color change caused by the interaction between the paste composition and the aqueous liquid.

Example

[0068] (Example 1) 26.5 g of polypropylene glycol (molecular weight = 750 g / mol), 26.5 g of polypropylene glycol (molecular weight = 1025 g / mol), and 31.6 g of polyethylene glycol (molecular weight = 400 g / mol) were added to a round-bottom flask equipped with a stirrer, a heating mantle, and a temperature regulator, purged with nitrogen, and evacuated. It was heated to 65 °C, and a full vacuum was applied to reduce the water content to less than 300 ppm. The vacuum was stopped, and 2.0 g of o-cresolphthalein and 1.0 g of dodecylbenzenesulfonic acid were added. It was stirred at 65 °C until the solid dissolved. 7.0 g of calcium oxide was added and dispersed. 6.0 g of Cab-O-Sil® M5 fumed silica was slowly added and stirred to form a paste. The paste was off-white in color. When applied to a wooden stick and immersed in E10 gasoline containing 1 phr of water, the paste in contact with the aqueous layer changed from light purple in 2 seconds to dark purple in 15 seconds.

[0069] (Example 2) 26.5 g of polypropylene glycol (molecular weight = 750 g / mol), 26.5 g of polypropylene glycol (molecular weight = 1025 g / mol), and 31.6 g of polyethylene glycol (molecular weight = 400 g / mol) were added to a round-bottom flask equipped with a stirrer, a heating mantle, and a temperature regulator, purged with nitrogen, and evacuated. The mixture was heated to 65 °C and a full vacuum was applied to reduce the water content to less than 300 ppm. The vacuum was stopped and 0.425 g of thymol blue and 0.085 g of nonanoic acid were added. The mixture was stirred at 65 °C until the solids dissolved. 7.0 g of calcium oxide was added and dispersed. 8.0 g of Cab-O-Sil® M5 fumed silica was slowly added and stirred to form a paste. The paste was orange in color. When applied to a wooden stick and immersed in E10 gasoline containing 1 phr of water, the paste in contact with the aqueous layer changed from light blue to dark blue in 12 seconds and 25 seconds, respectively. The paste stored in a sealed sample container turned green in 30 days, but the shelf life of such a composition is expected to be much longer when the composition is prepared on a larger commercial scale under conditions where moisture can be more rigorously excluded.

[0070] (Example 3) 26.5 g of polypropylene glycol (molecular weight = 750 g / mol), 26.5 g of polypropylene glycol (molecular weight = 1025 g / mol), and 31.6 g of polyethylene glycol (molecular weight = 400 g / mol) were added to a round-bottom flask equipped with a stirrer, a heating mantle, and a temperature regulator, purged with nitrogen, and evacuated. The mixture was heated to 65 °C and a full vacuum was applied to reduce the water content to less than 300 ppm. The vacuum was stopped and 0.5 g of thymol blue and 0.44 g of adipic acid were added. The mixture was stirred at 65 °C until the solids dissolved. 7.0 g of calcium oxide was added and dispersed. 6.0 g of Cab-O-Sil® M5 fumed silica was slowly added and stirred to form a paste. The paste was orange in color. When applied to a wooden stick and immersed in E10 gasoline containing 1 phr of water, the paste in contact with the aqueous layer changed to light blue in 2 seconds.

[0071] Example 4 26.5 g of polypropylene glycol (molecular weight = 750 g / mol), 26.5 g of polypropylene glycol (molecular weight = 1025 g / mol), and 31.6 g of polyethylene glycol (molecular weight = 400 g / mol) were added to a nitrogen-purged, evacuated round-bottom flask equipped with a stirrer, heating mantle, and temperature controller. The mixture was heated to 65°C, and full vacuum was applied to reduce the water content to less than 300 ppm. The vacuum was discontinued, and 0.5 g of thymol blue and 0.36 g of succinic acid were added. The mixture was stirred at 65°C until the solids were dissolved. 7.0 g of calcium oxide was added and dispersed. 6.0 g of Cab-O-Sil® M5 fumed silica was slowly added and stirred to form a paste. The paste was orange in color. When applied to a wooden stick and immersed in E10 gasoline containing 1 phr of water, the paste turned pale blue upon contact with the aqueous layer within 2 seconds.

[0072] Example 5 26.5 g of polypropylene glycol (molecular weight = 750 g / mol), 26.5 g of polypropylene glycol (molecular weight = 1025 g / mol), and 31.6 g of polyethylene glycol (molecular weight = 400 g / mol) were added to a nitrogen-purged, evacuated round-bottom flask equipped with a stirrer, heating mantle, and temperature controller. The mixture was heated to 65°C and full vacuum was applied to reduce the water content to less than 300 ppm. The vacuum was discontinued, and 1.0 g of thymolphthalein and 1.0 g of dodecylbenzenesulfonic acid were added. The mixture was stirred at 65°C until the solids were dissolved. 7.0 g of calcium oxide was added and dispersed. 6.0 g of Cab-O-Sil® M5 fumed silica was slowly added and stirred to form a paste. The paste was off-white in color. When applied to a wooden stick and immersed in E10 gasoline containing 1 phr of water, the paste in contact with the aqueous layer turned light blue in 15 seconds and dark blue in 60 seconds.

[0073] Example 6 26.5 g of polypropylene glycol (molecular weight = 750 g / mol), 26.5 g of polypropylene glycol (molecular weight = 1025), and 31.6 g of polyethylene glycol (molecular weight = 400 g / mol) were added to a nitrogen-purged, evacuated round-bottom flask equipped with a stirrer, heating mantle, and temperature controller. The mixture was heated to 65°C and full vacuum was applied to reduce the water content to less than 300 ppm. The vacuum was discontinued, and 0.25 g of cresol red and 2.0 g of dodecylbenzene sulfonic acid were added. The mixture was stirred at 65°C until the solids were dissolved. 7.0 g of calcium oxide was added and dispersed. 6.0 g of Cab-O-Sil® M5 fumed silica was slowly added and stirred to form a paste. The paste was brown in color. When applied to a wooden stick and immersed in E10 gasoline containing 1 phr of water, the paste in contact with the aqueous layer turned light purple in 5 seconds and dark purple in 15 seconds.

[0074] Example 7 26.5 g of polypropylene glycol (molecular weight = 750 g / mol), 26.5 g of polypropylene glycol (molecular weight = 1025 g / mol), and 31.6 g of polyethylene glycol (molecular weight = 400 g / mol) were added to a nitrogen-purged, evacuated round-bottom flask equipped with a stirrer, heating mantle, and temperature controller. The mixture was heated to 65°C and full vacuum was applied to reduce the water content to less than 300 ppm. The vacuum was discontinued, and 0.2 g of bromophenol blue and 5.0 g of dodecylbenzene sulfonic acid were added. The mixture was stirred at 65°C until the solids were dissolved. 7.0 g of calcium oxide was added and dispersed. 6.0 g of Cab-O-Sil® M5 fumed silica was slowly added and stirred to form a paste. The paste was brown in color. When applied to a wooden stick and immersed in E10 gasoline containing 1 phr of water, the paste in contact with the aqueous layer turned light blue in 2 seconds and dark blue in 10 seconds.

[0075] (Example 8 (Comparison)) 26.5 g of polypropylene glycol (molecular weight = 750 g / mol), 26.5 g of polypropylene glycol (molecular weight = 1025 g / mol), and 31.6 g of polyethylene glycol (molecular weight = 400 g / mol) were added to a round-bottom flask equipped with a stirrer, a heating mantle, and a temperature regulator, purged with nitrogen, and evacuated. It was heated to 65 °C and a full vacuum was applied to reduce the water content to less than 300 ppm. The vacuum was stopped and 0.86 g of thymol blue and 0.085 g of tripropyl borate were added. It was stirred at 65 °C until the solid dissolved. 7.0 g of calcium oxide was added and dispersed. 8.0 g of Cab-O-Sil® M5 fumed silica was slowly added and stirred to form a paste. The paste was dark orange in color. When applied to a wooden stick and immersed in E10 gasoline containing 1 phr of water, the paste in contact with the aqueous layer changed from light blue in 10 seconds to dark blue in 20 seconds, and when the paste came into contact with the hydrocarbon layer above the aqueous layer, black spots were formed on the paste. The paste in a sealed sample container turned blue in one day.

[0076] This example demonstrates the beneficial effect that the paste composition according to the present invention contains a proton-donating compound. The paste composition of Example 8 contained tripropyl borate (a stabilizer taught in the prior art) but did not contain a proton-donating compound. A much shorter shelf life was observed compared to the paste composition of Example 2 having the same composition as Example 8 except containing nonanoic acid instead of tripropyl borate.

Claims

1. A paste composition for causing a color change detectable upon contact with an aqueous liquid, comprising: a) at least one indicator dye capable of changing color within a pH range of from about 3 to about 11; b) at least one first inorganic base selected from the group consisting of calcium oxide, calcium hydroxide, strontium oxide, strontium hydroxide, barium oxide, barium hydroxide, magnesium oxide, magnesium hydroxide, and hydrides of these metals, which can react with water to convert the first inorganic base to a second inorganic base more basic than the first inorganic base; c) at least one liquid carrier selected from polyols, glycols, and mixtures thereof; d) optionally, at least one gelling agent; e) at least one proton-donating compound selected from the group consisting of C6-C24 aliphatic carboxylic acids, C6-C18 alkylated arylsulfonic acids, and combinations thereof, having a pKa of at most 12. The paste composition comprising the above components.

2. The paste composition according to claim 1, wherein the at least one proton-donating compound comprises at least one organic acid selected from the group consisting of nonanoic acid, dodecylbenzenesulfonic acid, and combinations thereof.

3. The paste composition according to claim 1 or 2, wherein the at least one proton-donating compound comprises at least one proton-donating compound having a solubility in water at 25 °C of from 0.01 g / L to 75 g / L.

4. The paste composition according to any one of claims 1 to 3, wherein the at least one proton-donating compound has a pKa of at least zero.

5. The paste composition according to any one of claims 1 to 4, wherein the at least one proton-donating compound is present in a stoichiometric excess relative to the total amount of water and the second inorganic base present when the paste composition is prepared.

6. The paste composition according to any one of claims 1 to 5, comprising in total from about 0.01 to about 5 mass percent of the at least one proton-donating compound.

7. The paste composition according to any one of claims 1 to 6, wherein the at least one first inorganic base and the at least one proton-donating compound are present in amounts effective to provide a mass ratio of first inorganic base:proton-donating compound of from 1:1 to 100:

1.

8. The paste composition according to any one of claims 1 to 7, comprising at least one water-soluble indicator dye.

9. The paste composition according to any one of claims 1 to 8, wherein at least one indicator dye comprises at least one indicator dye selected from the group consisting of o-cresolphthalein, phenolphthalein, p-naphtholbenzein, ethyl bis(2,4-dinitrophenyl)acetate, thymolphthalein, Nile blue A, cresol red, bromophenol blue, and thymol blue.

10. The paste composition according to any one of claims 1 to 9, wherein at least one first inorganic base comprises CaO.

11. The paste composition according to any one of claims 1 to 10, wherein at least one liquid carrier comprises at least one polyalkylene glycol.

12. A method of making a paste composition for producing a detectable color change upon contact with an aqueous liquid, a) at least one indicator dye capable of changing color in a pH range of from about 3 to about 11, b) at least one inorganic base selected from the group consisting of calcium oxide, calcium hydroxide, strontium oxide, strontium hydroxide, barium oxide, barium hydroxide, magnesium oxide, magnesium hydroxide, and hydrides of these metals, which can react with water to convert the first inorganic base to a second inorganic base more basic than the first inorganic base, c) at least one liquid carrier selected from polyols, glycols, and mixtures thereof, d) optionally, at least one gelling agent, and e) at least one proton-donating compound selected from the group consisting of C6-C24 aliphatic carboxylic acids, C6-C18 alkylated arylsulfonic acids, and combinations thereof having a pKa of at most 12 comprising the step of combining.

13. a) combining at least one polyalkylene glycol, at least one indicator dye, and at least one proton-donating compound to obtain a first mixture; b) combining the first mixture with at least one inorganic base to obtain a second mixture; and c) optionally, combining the second mixture with at least one gelling agent to obtain a paste composition The method according to claim 12, comprising.

14. A method for detecting an aqueous liquid in a container containing a content, comprising the steps of: bringing a measurement probe having a layer of the paste composition according to any one of Claims 1 to 11 disposed thereon into contact with the content of the container; withdrawing the measurement probe from the container; and visually inspecting the layer of the paste composition for a color change caused by the interaction between the paste composition and the aqueous liquid.