US 3592774 A
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United States Patent Oflice Int. Cl. Clld US. Cl. 252-89 Claims ABSTRACT OF THE DISCLOSURE A process for mechanical dishwashing in which the clear rinsing cycle employs a water-soluble starch degradation product and/ or sugar to obtain spot-free dishes and novel rinsing solutions.
PRIOR ART Known dishwashing methods with dishwashing machines have shown that it is most advantageous to use two cleaning agents, one in the cleaning process for thorough removal of food particles from the china pieces and a clear rinsing agent during the final rinse to obtain lustrous and dry dishes. Clear rinse agents have been used for a long time and by their surface active agents, the surface tension of the water is reduced in the final rinse which effects a film-like drainage of the water from the dishes. The said water film shall be drained off as long as possible without interruption. Any slight remaining traces of water are rapidly evaporated by the heat retained by the china from the wash step or by subsequent heating, or by ventilating, etc. The cleaned dishes then can be removed from the dishwasher in a dry and shiny condition. However, the known neutral clear rinse agents containing a surface-active agent are not able to safely prevent calcareous deposits and the development of stains with water having a high degree of hardness. Moreover, heavy foam formation may occur and interfere with the washing step.
To avoid these disadvantages, attempts have been made to acidify the clear rinse agents with inorganic acids such as phosphoric acid or organic acids such as lactic acid, tartaric acid or citric acid. These acid additives prevent an accumulation of calcium deposits from hard Water and give spot-free dishes and satisfactory clear-dry effects. However, the use of these acidified clear rinsing agents has the disadvantageous effect on the stability of porcelain glazes and glass decor. Although the acid agents alone do not cause any noticeable effect, considerable corrosion phenomena may occur when they are used in combination with alkaline cleaning agents. This is caused by the alternate alkaline and acid treatment of the decoration whereby the alkaline agent might extract silicate ions therefrom While the acid clear rinse agent might leach metallic oxides from the glaze.
OBJECTS OF THE INVENTION It is an object of the invention to provide a novel process for machine washing of dishes without spotting.
It is another object of the invention to provide a dishwashing process which will avoid calcium deposits without adversely affecting dishes.
These and other objects and advantages of the invention will become obvious from the following detailed description.
THE INVENTION The novel dishwashing process of the invention for machine washing of dishes comprises first washing dishes with an alkaline washing agent and then rinsing the washed dishes with an aqueous rinse solution containing about 0.1 to 2.0 gm. per liter of at least one neutral rinse Patented July 13, 1971 agent selected from the group consisting of water-soluble starch degradation products and sugars. The said process unexpectedly gives an outstanding luster to the dishes and avoids calcareous deposits, corrosion phenomena and foam formation. Moreover, the rinse agents have the advantage of being physiologically acceptable.
Examples of suitable rinse agents are sugars such as glucose, lactose, particularly cane sugar and beet sugar and starch degradation products by action of enzymes or acids on starch, soluble dextrins, etc. The said sugars or degradation products may be in refined form or in crude form such as baking syrup or molasses.
In dish washing cycles in which a drying step follows the rinse step, a completely satisfactory clear-dry effect is obtained by the sole use of sugars or starch degradation products in the rinsing step. For dishwashing cycles with no final drying step, it is preferred to add a non-ionic or anionic surface active agent to the rinse agent.
Examples of suitable additives to the rinse agent are non-ionic, low foaming surface active agents such as (A) adducts of ethylene oxide with fatty alcohols of 8 to 22 carbon atoms or alkyl phenols having 2 to 16 alkyl carbon atoms; (B) adducts of ethylene oxide with polypropylene oxide having a molecular weight of 500 to 2000; (C) adducts of propylene oxide to adducts of group (A) and (D) sugar esters of fatty acids of 8 to 20 carbon atoms.
The novel rinse agent concentrates of the invention are comprised of an aqueous solution of 20 to 50% by weight of at least one agent selected from the group consisting of sugars and water-soluble starch degradation products and 0 to 20% of a water-soluble organic solvent. The use of the organic solvent improves solubility of the concentrates. Examples of suitable water-soluble organic solvents are lower alkanols such as ethanol, propanol, isopropanol, etc. The concentrates can optionally contain 1 to 20% by weight of a non-ionic or anionic surface active agent. The concentrated rinsing agent may be added by manual measurement or preferably by an automatic dosing device.
In the following examples there are described several preferred embodiments to illustrate the invention. However, it should be understood that the invention is not intended to be limited to the specific embodiments.
EXAMPLE I Normally soiled dishes were cleaned in a commercial dishwashing machine having a drying cycle with an aqueous alkaline cleaning solution heated to 55 to 70 C. and containing 1.4 gm./l. of sodium tripolyphosphate, 0.56 gm./l. of sodium metasilicate and 0.04 gm./l. of potassium dichloroisocyanurate and rinsed with clear water at 60 to 70 C. and containing 0.12 gm./l. of an admixture of saccharose and molasses. The rinse water had been softened to a hardness of 1 by passing it through a cation exchanger and the dry residue amounted to 0.56 gm./l. The said washing cycle gave a satisfactory clear-dry effect.
EXAMPLE II The process of Example I was repeated with the exception that the clear rinse water contained 0.1 gm./l. of molasses and 0.01 gm./l. of a mixture of an adduct of 20 moles of ethylene oxide with one mole of nonylphenol and an adduct of first 9 moles of ethylene oxide and then 10 moles of propylene oxide with one mole of nonyl phenol. This clear rinsing composition proved satisfactory in the commercial dishwashing device of Example I and in dishwashers without a drying cycle.
EXAMPLE III Dishes were washed in a three-cycle dishwashing machine using in the first cycle an aqueous alkaline cleaning solution at 55 to 70 C. and containing 2.1 gm./l. of
3 sodium tripolyphosphate, 0.84 gm./l. of sodium metasilicate and 0.66 gm./l. of potassium dichloroisocyanurate, clear rinse water having a hardness of 16 in the second cycle and in the third cycle clear aqueous solution at 60- 70 C. and containing 0.18 gm./l. of an admixture of saccharose and molasses. After 150 cycles of washing, no calcium-containing deposits were observed on the dishes or in the machine and the clear-dry effect was perfect and there were no adverse effects on the porcelain overglaze decorations.
EXAMPLE 1V Using the procedure of Example 111, dishes were washed which used in the clear rinsing cycle a solution containing 0.15 gm./liter of molasses and 0.5 gm./liter of adduct of by weight of ethylene oxide with polypropylene glycol and having a molecular weight of 1750. Even after 150 cycles of washing, a perfect clear-dry effect was obtained with no deposits on the rinsed dishes or in the dishwasher and without any corrosion phenomena.
EXAMPLE V Water having a 16 German hardness originally and which had been hardened to a 30 German hardness by the addition of calcium chloride was used in the following rinse test in which the necessary amount of rinse water used in common household diswashers was taken from this source. The dishes were washed with an alkaline cleaning solution containing 3.5 gm. per liter of sodium tripolyphosphate, 1.4 gm. per liter of sodium metasilicate and 0.1 gm. per liter of potassium dichloroisocyanurate. The clear rinsing solution contained 0.27 gm. per liter of an admixture of saccharose and molasses to obtain a cleardry effect. After 150 cycles of washing, there were no calcareous deposits or corrosion signs on the dishes or the dishwasher.
EXAMPLE VI The process of Example V was repeated except that the clear rinse solution contained 0.31 gm. per liter of molasses and 0.08 gm. per liter of an equal mixture of the adduct of 20 moles of ethylene oxide with 1 mole of nonylphenol and the adduct of 5 moles of ethylene oxide with 1 mole of nonylphenol and the adduct of 5 moles of ethylene oxide and 13 moles of propylene oxide with 1 mole of coconut oil alcohols having 12 to 18 carbon atoms. An excellent clear-dry effect without calcareous deposits on dishes and the dishwasher and without any crazing of the porcelain overglaze decorations was noted after 150 cycles of washing.
Various modifications of the compositions and method of the invention may be made without departing from the spirit or scope thereof and it is to be understood that the invention is to be limited only as defined in the appended claims.
1. A process for machine washing of dishes comprising first washing dishes with an alkaline washing agent and then rinsing the washed dishes with an aqueous rinse solution consisting essentially of 0.1 to 2.0 gm. per liter of neutral sugar rinse agents.
2. The process of claim 1 wherein the rinse agent is selected from the group consisting of cane sugar, beet sugar and dextrin.
3. The process of claim 1 wherein the neutral rinse agent also contains 1 to 20% by weight of a low foaming nonionic surface active agent.
4. The process of claim 3 wherein the surface active agent is a sugar ester of a fatty acid of 8 to 20 carbon atoms.
5. The process of claim 3 wherein the surface active agent is a lower alkylcne oxide adduct of at least one member of the group consisting of ethylene oxide and propylene oxide.
6. The process of claim 1 wherein the neutral rinse agent is an aqueous concentrate containing 20 to by weight of the rinse agent.
7. A rinse agent concentrate for machine washing of dishes consisting essentially of an aqueous solution of 20 to 50% by weight of neutral sugar rinse agents.
8. The concentrate of claim 7 containing 1 to 20% by weight of an nonionic surface active agent.
9. The concentrate of claim 7 containing up to 20% of a lower alkanol.
10. The concentrate of claim 7 wherein the agent is selected from the group consisting of beet sugar, cane sugar and dextrin.
References Cited UNITED STATES PATENTS 3,062,878 11/ 1962 Karabinos et el. 252-89 3,074,927 1/1963 Saltman et al. 25289 3,082,172 3/1963 Temple et al. 25289 3,481,881 12/1969 Wedell 252-89 FOREIGN PATENTS 211,646 3/1966 Australia 252-89 OTHER REFERENCES Mehltretter et al. I: Sequestration of Sugar Acids, Incl. & Eng. Chem., December 1953, pp. 2782-2784.
Mehltretter et al. II: New Low Cost Sequestrants, Soap & Chem Spec., August 1969, pp. 49, 50 and 106.
LEON D. ROSDOL, Primary Examiner W. E. SCHULZ, Assistant Examiner U.S. Cl. X.R. 1342: 252--