US 3770641 A
Description (OCR text may contain errors)
United States Patent Int. Cl. Clld 17/04 US. Cl. 25290 8 Claims ABSTRACT OF THE DISCLOSURE In the packaging of multi-component systems wherein at least one component alone and/or in excessive proportion to other components can be topically hazardous or otherwise detrimental, but can be rendered harmless when properly mixed with other components, the improvement that comprises incorporating in at least one of the components to be combined an indicator providing a characteristic color when exposed to an excess of said detrimental component and losing said characteristic color upon elimination of excess of said detrimental component. In instances where multi-component systems contain more than one individually detrimental component with such detrimental characteristics being overcome in proper mixing thereof, there should be present a separate colorimetric indicator of excess for each such detrimental component. The improvement is particularly adapted for use with multi-component systems which are packaged in containers having compartments separated by means permitting mixing of the components to homogeneity within the container prior to use, and with the outer container having translucent to transparent qualities sufficient to permit viewing of the colorimetric indicator means as components are being mixed.
This application is a continuation-in-part of application Ser. No. 169,518 filed Aug. 5, 1971 which in turn is a continuation of application Ser. No. 758,663 filed Sept. 10, 1968, both now abandoned.
BACKGROUND OF THE INVENTION There has been extensive and increasing adoption in recent years of multi-component chemical systems intended to be mixed by the user just prior to use to provide an end product of predetermined properties. Such multi-component systems are frequently packaged in flexible-walled multi-compartment containers which may be divided by rupturable diaphragms, removable clamps, or the like, to permit co-mingling of the several components within a still unruptured outer container. This type of packaging has found considerable use in varied fields including, without limitation, thermosetting resin systems, systems for preparing warm soap and lather compositions, systems for plaster and cement, systems of a non-resinous nature, such as cake mixes and related food product, and-other consumer items in which dilferent components must be maintained separate from each other in storage, and mixed just prior to use.
With products of this type and kind the careful proportioning of components in the packaging thereof can assure predictable desired results when the components are properly mixed. It is up to the consumer or user, however, to carry out the critical mixing step, and it frequently happens that through inexperience or carelessness mixing is not carried to a sufiicient extent before using the product. The results of such improper mixing can 3,770,641 Patented Nov. 6, 1973 detrimentally affect the properties of the particular prod not. For example, a cake produced from a poorly blended mix may be of poor texture or flavor; a plaster or plastic mass may develop areas of differing hardness when setting, and the like.
In addition, however, improper mixing whereby local excesses remain of one or more reactive components can create a potential hazard to the user due to the caustic, toxic, or otherwise harmful or topically hazardous nature of the free reactive component or components. In thermosetting resin systems, for example, the free hardening or curing agent can frequently be of a toxic or irritating nature. Likewise in exothermic and acid-base reactions suitable for preparing hot soaps and lathers incomplete mixing which might leave high local concentrations of either acid or base could be harmful to the user, if applied to body parts on which properly mixed soap or lather would be entirely safe.
It appears, therefore, that present practices in the packaging and distribution of multi-component systems in multi-compartment containers leaves much to be desired from the standpoint of both realization of intended quality of products produced from such systems, and safety to the user in handling systems which contain potentially harmful components.
THE INVENTION In accordance with the present invention the problems above mentioned can be overcome by employing colorimetric means for indicating a free or excess concentration of a potentially detrimental component with the characteristic color being distinctly altered as the excess concentration of such detrimental component is eliminated. Such colorimetric means suitably comprise indicators having characteristic color changes in the presence and absence of acids, bases, reducing agents, oxidizing agents, or other reactive materials of a topically hazardous or otherwise potentially detrimental nature.
When the components intended to co-act or react with such potentially detrimental material are themselves nondetrimental, a single indicator means may be sufiicient. In some systems involving acid-base reactions, oxidizing agent-reducing agent reactions and the like two or more reactive components may, in the free state, he of a potentially detrimental nature; and in such instances there should be a separate indicator means responsive to each of the potentially detrimental materials. In such situations the ideal result is to provide essentially no color at the point of neutrality or complete reaction between the several reactive components. At the same time in any mixing operation such as an acid-base reaction mixture there may be numerous swings to the acid or base side in any particular location Within a mass before final equilibrium or neutrality is reached throughout a thoroughly mixed mass.
The invention can be applied and practiced in various ways. With separately packaged materials which are measured out and mixed in a suitable container, the colorimetric indicator can tell the user not only when mixing is complete, but also when there has been an inadvertent error in measuring which results in an excess of a potentially harmful component, in which instance the color indicator persists even after complete mixing.
The latter possibility is also a factor in packaging intended to automatically discharge reactive components in predetermined proportions. Thus, for example, the current trend in aerosol packaging involves the use of separate containers of reactive components which are collectively discharged and mixed under the action of gas pressure. In the event of malfunctioning of the valve or proportioning mechanism the discharged material may not contain the intended proportion of reactive components. One example of this is the hot lather shave dispensers wherein components providing an exothermic reaction in separate compartments are mixed in the discharge thereof. When properly proportioned to completely interreact, such exothermic reactants can be quite harmless, yet one or more of the components, if present in excess, may be detrimental or topically hazardous to the user. With a colorimetric indicator present a distinctly different color in the discharged material (from the white or other intended color) can clearly indicate to the user that the particular quantity of discharged material is unfit for use.
Selection of the appropriate colorimetric indicator will depend upon the particular detrimental component or components present in a system and the reactivity thereof with various dyes and indicators. Acids and alkalies, if present in excess in a product can frequently be detrimental, and with such materials conventional indicators can be employed. For example, a small amount of phenolphthalein which changes from red at about pH 10 to colorless at about pH 8.2 is a good indicator for excess alkali. Methyl Orange, which is red at about pH 3.1 and light yellow at about pH 4.4 is a good indicator for excess acid. In a system containing both acid and alkali these two indicators can be present, in which event the absence of any red color (and presence of a pale yellow color) indicates an essentially neutral mixture, with no local excesses of either acid or base.
In a system containing both acid and base it is also possible, if color in the final mixture is not objectionable, to employ a single indicator such as litmus which changes from red at about pH 4.5 to blue at about pH 8.3. A properly blended mixture will have a purplish color, and the appearance of any spots or streaks of red or blue indicates local excesses of acid or base respectively.
The following examples are presented to show typical adaptations of the present invention, but it is to be understood that these examples are given by way of illustration and not of limitation.
Example I of mixing. In this time the temperature rose to 80 C.,
and the final pH was 6.3, confirming the colorimetric indication of absence of free caustic. The resulting warm detergent when mbbed between the hands produced a rich lather with good cleaning properties.
Example II The procedure described in Example I was repeated except that in addition to the phenolphthalein 3 drops of Methyl Orange indicator was also added to the aqueous solution. When the flake NaOH was added, and the mixture stirred with a thermometer a pink color developed at the bottom and a more reddish color at the top with an almost colorless zone between. The colorless zone grew larger with continued mixing until in about 30 seconds all trace of pink or red color disappeared. At this point the temperature had risen to 80 C. and the pH was about 6.3. In contrast to the essentially white or colorless product in Example I this product was a pale yellow or eggshell color due to the small amount of Methyl Orange indicator present, but this trace of color was not objectionable and was in distinct contrast to the intense color of the unmixed acid and alkali zones.
The temperature rise from C. to 80 C., which is generated by both the heat of solution of the NaOH and the heat of reaction with the citric acid, is very beneficial particularly since it takes place in such a short time interval. Actually a temperature of C. is topically hazardous as it is too hot for handling, or immediate application to the hands, and any desired smaller temperature rise can be obtained by reducing the amounts of NaOH and citric acid while maintaining the same proportions. If the proportions are appreciably varied and an excess of NaOH or citric acid is present, the final mixture will retain a pink or red color respectively providing a visual indication of improper mixing and the presence of a detrimental component in the product.
Example III The procedure of Example II was repeated except that the initial aqueous solution was diluted to only 15 ml., and the NaOH was first dissolved in 5 ml. of water and the two solutions combined with stirring. This time the temperature rose to about 70 C. Essentially the same results are obtained when the initial solution is diluted to only 10 ml. and the NaOH separately dissolved in 10 ml. of water. In both instances the temperature rise is due solely to the heat of reaction, as the NaOH is already in solution.
Example IV Separate solutions of citric acid and detergent with indicator and of NaOH prepared as described in Example III (with the water equally divided between the two solutions) are used to fill separate compartments of flexible heat scalable plastic containers having transparent walls and a rupturable diaphragm between the two compartments using 1 ml. of solution in each compartment. The compartment containing the citric acid is red due to the presence of the indicators in this solution. When a filled container is stressed to rupture the diaphragm, and the container manipulated in the fingers to move the contents back and forth, the color becomes a mixture of areas of red, pink and pale yellow, with the red and pink gradually disappearing. When all trace of red or pink color has disappeared, the mixing is complete and the warm detergent product is safe and ready for use. At this time the container can be ruptured, as for example, by pulling on a conventional tear strip, making available a practical quantity of warm detergent solution for a oneuse hand cleaner or the like.
Example V The procedure of Example IV is repeated using a divided container of larger size so that the liquids fill only about one quarter of the volume of the compartments. When the diaphragm is now ruptured and the container manipulated, the mixing operation also combines air with the mixture generating a heavy lather in which the disappearance of pink or red color again indicates the point of complete mixing. The resulting warm lather is an effective shaving lather.
The texture of the discharged lather can be further enhanced by providing in the container wall a fine mesh screen member with a removable cover or tear strip. Forcing the rather coarse lather (large bubbles) through the fine mesh screen breaks up the bubbles to a very fine texture not unlike that generated by a shaving brush.
Example VI The procedure of Example IV is repeated placing the two solutions in separate compartments of a divided pressure container of the aerosol type equipped with a mixing valve and appropriate foam discharge, and using compressed nitrogen as the pro ellent. Since the two liquids are mixed at a uniform rate and with considerable agitation by the propellent, the resulting foam is pale yellow or essentially colorless. If there is any malfunctioning of the valve, however, leading to improper feed of the two liquids, the foam has a pink or red color giving a clear warning to the operator that the foam being discharged is unfit for use.
As the two solutions are mixed in uniformly fed small streams with the propellent providing ample mixing agitation, the reaction is substantially instantaneous and complete, with each aliquot of generated foam receiving the same amount of exothermic heat. Thus the desired mass of foam, whether large or small, is mixed to an essentially uniform temperature.
The foregoing examples show adaptation of the princi- .rples of the present invention to typical mixing in open containers, closed containers and closed pressurized containers in which the internal pressure is utilized to discharge quantities of a mixture. It will be understood that the procedures described in these examples can be applied to the preparation of various products from mixtures of two or more components, at least one of which in the free state or in excess in the product can be detrimental, provided a suitable dye or indicator is available having a significant color change in moving from the presence to the absence of a free excess of the detrimental component. It will also be understood that the heating, beneficial in preparing warm detergent products and lathers in the foregoing examples, is illustrative of various secondary effects which can be realized in the properly blended product. With proper selection of reactants, for example, the product can be one characterized by controlled cooling, with the cooling action supplied by substances such as potassium bromide, potassium aluminum sulfate or sodium borate, for which dissolution in water is an endothermic reaction.
Quite apart from such secondary reactions or benefits, however, the colorimetric means for assuring proper mixing of two or more components is of distinct advantage, particularly in view of the rapidly expanding use of multicomponent containers having means to permit mixing of the combined contents. It is, of course, desirable that the container in which such mixing is being accomplished have walls which are suificiently transparent so that color and color changes in the mixture can readily be viewed from outside the container. In this way proper mixing of the components can be assured in advance of opening the container. If an opaque container is used, however, and when product is mixed at the point of discharge in the manner described in Example VI, the presence of telltale color in the discharged product will warn the operator of improper mixing.
Various changes and modifications in the indicator means for consumer mixing of multi-component systems as herein described may occur to those skilled in the art, and to the extent that such changes and modifications are embraced by the appended claims, it is to be understood that they constitute part of the present invention.
1. A multi-component system consisting essentially of a plurality of components sufficiently reactive with each other as to require physical separation during storage and homogeneous mixing just prior to use, one of said components being selected from the group consisting of toxic or topically hazardous substances of acidic reaction and toxic or topically hazardous substances of basic reaction prior to mixing, the amounts of said substance and an other component reactive therewith being such that a homogeneous mixture of said components is not toxic or topically hazardous, and one of the components of said system including a pH indicator in an amount to provide a characteristic color in the presence of free amounts of said toxic or topically hazardous substance and a distinct color change in the absence of free amounts of said substance, thereby visually signalling when mixing of said components has reached a homogeneous and non-toxic or non-topically hazardous state.
2. A multi-component system as defined in claim 1 wherein said toxic or topically hazardous component in the free state provides a basic reaction and the indicator employed is phenolphtalein, whereby the mixture contains areas of pink coloration so long as free amounts of the toxic or topically hazardous component persist and becomes free of any pink coloration when adequate mixing has eliminated free amounts of said toxic or topically hazardous component.
3. A multi-component system as defined in claim 1 wherein said toxic or topically hazardous component in the free state provides an acidic reaction and the indicator is Methyl Orange, whereby the mixture contains areas of red coloration so long as free amounts of the toxic or topically hazardous component persists and becomes free of any red coloration when. adequate mixing has eliminated free amounts of said toxic or topically hazardous component.
4. A multi-component system as defined in claim 1 wherein said system contains two components which may be toxic or topically hazardous in the free state and separate indicators are included in said system providing separate characteristic colors when exposed to excesses of said toxic or topically hazardous components and a substantial color change when the mixture is free of such excesses.
5. A multi-component system as defined in claim 4 wherein the two toxic or topically hazardous components are characterized as providing, in the free state, basic and acidic reactions, respectively, and the indicators employed are phenolphthalein and Methyl Orange providing pink and red coloration in areas containing free amounts of said basic and acidic components, respectively, and absence of any pink and red coloration When free amounts of said basic and acidic components have been eliminated.
6. A multi-component system as defined in claim 5 wherein acidic and basic components are employed in amounts to provide a useful elevation of temperature in the resulting mixture.
7. A multi-component system as defined in claim 6 wherein said system contains water and a detergent, and the resulting mixture comprises a free foaming, warm detergent product.
8. A multi-component detergent system as defined in claim 7 wherein the acidic and basic reactive components are retained in separate compartments of a container and means is provided for combining said components just prior to a need for such warm detergent product.
References Cited UNITED STATES PATENTS Re. 17,383 7/1929 Englund 252-173 2,502,881 4/1950 Parker 252-- 2,615,847 10/1952 Thompson 252-161 2,663,692 12/1953 COrso et a1 252408 2,994,664 8/1961 Wachter 252-90 3,042,621 7/1962 Kirschenbauer 252-1883 3,240,396 3/1966 Friedenberg 252-90 3,475,239 10/ 1969 Fearon et a1 252-1883 2,876,935 3/ 1959 Lindberg 222- OTHER REFERENCES Rose: The Cond. Chem. Dict. vol. 6, Reinh'old Pub. (30.. pp. 603604.
Smith: College Chemistry, 1946, Appleton-Century Co. Inc., p. 269.
WILLIAM E. SCHULZ, Primary Examiner US. 01. x11. 252-1883, 408