Abstract:
A hard surface cleaning composition formulated for cleaning sub-freezing surfaces without solidifying, comprising: about 20-70 wt-% water, about 0.5-20 wt-% nonionic surfactant such as ethoxylated alkyl phenols, about 0.5-15 wt-% alkaline compound such as sodium hydroxide, about 10-60 wt-% ethylene and/or propylene glycol, and about 0.5-20 wt-% of at least one C 2-3  alcohol.

Description:
This is a continuation of application Ser. No. 07/050,623, filed May 15, 1987, now abandoned. 
    
    
     FIELD OF THE INVENTION 
     The invention relates generally to hard surface cleaning compositions and specifically to hard surface cleaning compositions formulated for cleaning sub-freezing surfaces without solidifying. 
     BACKGROUND OF THE INVENTION 
     The cleaning of sub-freezing surfaces such as the interior of a walk-in freezer is a difficult and time consuming task as the typical aqueous based cleaning compositions tend to freeze under such conditions. It is known to use a low freezing point alcohol such as ethanol as a cleaning composition which can overcome this problem but, while effective in preventing freezing of the cleaning composition, it has proven to be an ineffective cleaner. 
     The most common method of cleaning sub-freezing surfaces such as the interior of a walk-in freezer is to periodically warm up the surfaces to be cleaned to room temperature and then cleaning the room temperature surfaces with any of the typical hard surface aqueous based cleaning compositions. While effective, this method of cleaning sub-freezing surfaces is time consuming, labor intensive and can adversely affect frozen items stored therein. 
     Accordingly, a substantial need exists for a safe, inexpensive, aqueous based cleaning composition capable of effectively cleaning sub-freezing surfaces. 
     SUMMARY OF THE INVENTION 
     I have discovered an inexpensive, aqueous based cleaning composition capable of cleaning sub-freezing surfaces, which comprises: about 20-70 wt-% water, about 0.5-20 wt-% nonionic surfactant, about 0.5-15 wt-% alkaline compound, about 10-60  wt-% ethylene and/or propylene glycol, and about 0.5-20 wt-% of at least one C 2-3  alcohol. The components may be combined in any order to form the cleaning composition. 
     The cleaning composition may optionally contain an effective hardness sequestering amount of a hardness sequestrant and/or an effective defoaming amount of a silicone based defoamer. 
     Sub-freezing surfaces may be cleaned with the composition without the need to warm up the surface by simply scrubbing the sub-freezing surface with a cleaning amount of the cleaning composition and then removing the soil-containing composition from the surface. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A major portion of the cleaning composition comprises a mixture of the cosolvents, water, a C 2-3  glycol and a C 2-3  alcohol. The water/glycol/alcohol combination creates a system having a freezing point well below that of water alone, while retaining many of the attributes of an aqueous based system such as low cost, safety and ease of use. The cleaning composition contains about 20-70 wt-% water, about 10-60 wt-% glycol, and about 0.5-20 wt-% alcohol at a ratio of about 1 part water to 0.5 to 4 parts glycol to 0.1 to 1 part alcohol. 
     When the cleaning composition is intended for use around consumable goods, it is preferred to use propylene glycol as the glycol and isopropanol as the alcohol in light of their nontoxic nature. 
     The freezing point of the cleaning composition may be varied by adjusting the ratio between water, glycol and alcohol. As an aid to estimating the ratio necessary to achieve a desired freezing point the freezing points for various two-component mixtures of water and either ethanol, isopropanol, ethylene glycol or propylene glycol are provided in Tables 1-4. 
     
                       TABLE 1______________________________________Ethyl Alcohol-Water Mixtures% Alcohol  % Alcohol    Freezing PointBy Weight  By Volume    °C.                            °F.______________________________________2.5        3.13         -1.0     30.24.8        6.00         -2.0     28.46.8        8.47         -3.0     26.611.3       14.0         -5.0     23.013.8       17.0         -6.1     21.016.4       20.2         -7.5     18.517.5       21.5         -8.7     16.318.8       23.1         -9.4     15.120.3       24.8         -10.6    12.922.1       27.0         -12.2    10.024.2       29.5         -14.0    6.826.7       32.4         -16.0    3.229.9       36.1         -18.9    -2.033.8       40.5         -23.6    -10.539.0       46.3         -28.7    -19.746.3       53.8         -33.9    -29.056.1       63.6         -41.0    -41.871.9       78.2         -51.3    -60.3______________________________________ 
    
     
                       TABLE 2______________________________________Prestone-Water Mixtures*% Prestone     % Prestone   Freezing PointBy Weight By Volume    °C.                           °F.______________________________________10        9.2          -3.6     25.615        13.8         -5.6     22.020        18.3         -7.9     17.825        23.0         -10.7    12.830        28.0         -14.0    6.840        37.8         -22.3    -8.250        47.8         -33.8    -28.860        58.1         -49.3    -56.7______________________________________ *Eveready Prestone (manufactured by the National Carbon Co.), marketed fo antifreeze purposes, is 97% ethylene glycol containing fractional percentages of soluble and insoluble ingredients to prevent foaming, creepage and water corrosion in automobile cooling systems. 
    
     
                       TABLE 3______________________________________Iso-Propyl Alcohol-Water Mixtures% Alcohol    Freezing PointBy Volume    °C.       °F.______________________________________ 5           -1.7             2910           -3.3             2615           -6.1             2120           -8.3             1725           -11.1            1230           -14.4            635           -17.8            040           -18.3            -145           -18.9            -250           -20.0            -455           -21.7            -760           -23.3            -1065           -24.4            -1270           -26.7            -1675           -32.2            -2680           -41.7            -43______________________________________ 
    
     
                       TABLE 4______________________________________Propylene Glycol-Water Mixtures% Glycol     Freezing PointBy Weight    °C.       °F.______________________________________ 5           -1.1             3010           -2.2             2815           -3.9             2520           -6.7             2025           -8.9             1630           -12.8            935           -16.1            340           -20.6            -545           -26.7            -1650           -33.3            -28______________________________________ 
    
     To achieve a cost effective cleaning composition useful in substantially all situations, it is preferred to employ a water/glycol/alcohol ratio of about 1.3/1/0.2 to 1/1/0.5. 
     In addition to acting as a freezing point depressant the alcohol also acts to dissolve and suspend certain soils such as animal fats and oils and food particles. 
     To enhance the cleaning efficiency of the composition, 
     about 0.5-20 wt-% of a nonionic surfactant and about 0.5-15 wt-% of an alkaline compound may be added to the cosolvents. 
     Surfactants are a well known group of compounds having contrasting hydrophilic and hydrophobic portions which allow the compound to significantly reduce surface tension between a surface and an aqueous solvent in which the surfactant is dissolved. Nonionic surfactants are those surfactants which bear essentially no charge when dissolved or dispersed in water. While substantially any nonionic surfactant may be usefully employed in the present composition, those types typically employed in cleaning compositions include polyoxyethylenes, ethoxylated alkyl phenols, ethoxylated aliphatic alcohols, and polyalkylene oxide block copolymers. For reasons of low cost, ease of availability and effective surfactant properties, the preferred nonionic surfactants for use in the present invention are the ethoxylated alkyl phenols and the ethoxylated aliphatic alcohols. Most preferred are the C 8-10  alkyl phenols having 6 to 10 ethylene oxide units, and the C 8-15  aliphatic alcohols having 7 to 12 ethoxide units. 
     The manufacture of ethoxylated nonionic surfactants is well known as evidenced by the detailed disclosure of the manufacture and use of nonionic surfactants found in the Kirk-Othmer, Encyclopedia of Chemical Technology, 2d Ed., Vol 19, pp. 507-590. 
     Alkaline compounds useful in the present invention include any of those alkaline compounds typically employed in cleaning compositions including sodium and potassium hydroxide, monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), sodium and potassium bicarbonate, sodium and potassium sequicarbonate, sodium and potassium carbonate, sodium and potassium borate, etc. Because of their low cost, ease of availability and effective cleaning characteristics the preferred alkaline compounds for use in the present composition are the alkali metal hydroxides, MEA and TEA. 
     An effective hardness sequestering amount of a hardness sequestrant may optionally be added to the composition to remove Ca, Mg and Fe ions from the cleaning media and thereby to improve the cleaning effectiveness of the surfactant. Any of the commonly known sequestering agents such as aminopolycarboxylic acids, alpha-hydroxy acids and condensed phosphates may be incorporated into the composition. Because of their solubility and low cost, the preferred sequestering agents are the amino polycarboxylic acids such as NTA and EDTA and the hydroxy acids such as citric and tartaric acids. 
     An effective defoaming amount of a silicone based defoamer may optionally be added to the composition to simplify removal of the composition from the sub-freezing surface. Any of the well known silicone based defoamers may be utilized in the present invention including SAG 10, SAG 710, etc., (silicone defoamer sold by Union Carbide). Because of its clearance as a food grade material, the preferred silicone defoamer is SAG 710 Silicone Emulsion. 
     The cleaning composition may be manufactured by blending the individual components in any desired manner. It is, however, preferable to add the alkaline compound to the water rather than vice versa so that any heat generated by hydration of the alkaline compound may be dispersed throughout the water to prevent splattering. 
     The cleaning composition may optionally contain other components commonly found in liquid cleaning compositions such as a fragrance, a dye, etc. 
     The formulation of two typical examples of my cleaning composition are presented below to aid in a complete nonlimiting understanding of my invention. 
     
         ______________________________________Example I             Example IIComponent    Wt-%     Component    Wt-%______________________________________Water        48       Water        43MEA          3        TEA          5IPA          7.5      EDTA         5NPE 9.5.sup.1        1.5      IPA          5SAG 710.sup.2        0.002    SAG 710      0.002Propylene Glycol        40       Propylene Glycol                              40Dye          0.0006   Dye          0.0006______________________________________ .sup.1 Nonylphenol ethoxylate containing an average of 9.5 ethoxy units. .sup.2 A silicone defoamer sold by Union Carbide. 
    
     The formulation of Example I is designed to clean walk-in freezers or food storage areas maintained at about -25° to -15° F. (-32° to -26° C.) without warming or defrosting of the freezer or food storage area. The composition is applied to the surface by a means such as a mop, a sponge, a spray mechanism, etc. The composition is spread evenly over the surface to aid in soil removal. The composition is then allowed to remain in contact with the surface for a time necessary to loosen frozen soil and ice deposits which is typically between 2 to 20 minutes. For optimum results the cleaning composition is preferably left in contact with the frozen surface for about 5 to 10 minutes. The cleaning solution is then removed from the surface by means of a mop, sponge, a vacuum, etc. 
     The formulation of Example II is designed to clean subfreezing areas that have accumulated soil deposits and mineral deposits. Such areas include but are not limited to freezers, meat lockers, cold storage warehouses, etc. The method of application and contact time are substantially similar to that outlined with respect to the formulation of Example I. 
     The specification and Examples above are presented to aid in the complete nonlimiting understanding of the invention. Since many variations and embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.