RINSE METHOD

Abstract: Rinsing of smooth surfaces with water containing rinse aid is performed by a rinse solution, which is prepared just prior to use by dilution of a very concentrated rinse aid containing at most 30 % by weight water. Transport and storing of diluted rinse aid and deterioration of the effect of the rinse aid is avoided. Method and composition are described.

Description: RINSE METHOD After mechanical cleaning of smooth surfaces, for instance car enamel, restaurant tableware etc., usually a water rinse with an added rinse aid is used to get a bright, shining and spotless surface without streaking and filming. Rinses with other purposes exist, for instance, disinfection with chlorine containing solutions such as sodium hypochlorite solutions. Such types of rinses are beyond the scoop of this application. Hot water, which is used in dish washing machines and in many automobile washing facilities, gives faster evaporation and shorter drying time. The rinse aid should give fast and even sheeting action. In most dish washing machines and many automobile washing facilities hot water is generated in a so-called super-heater or percolator. Usually liquid rinse aids are delivered as a concentrate with 20 to 30% active material and 70 to 80% water. Sometimes rinse aids are delivered as cast cakes, which are gradually dissolved by a water jet directed against the cake. To make this possible, the components of the rinse aid must be adjusted to the method of manufacturing. Restrictions with regard to suitability for casting and slow, gradual and uniform leaching of the cake may cause that rinse aid effects, with regards to good sheeting action, must come in second place. Thus, liquid rinse aids are preferred. Often spotting of the rinsed surfaces occurs after drying despite addition of rinse aid. Then the drying effect is often judged as bad. Some common approaches are to try to remedy this problem by changes in the composition of the rinse aid, increasing the amount of rinse aid, increasing the amount of rinsing water and prolonging the mixing time at the final dilution to use solution. Usually rinse aid is added as early as possible, as one believes that a long mixing time is an advantage towards getting an even distribution in the rinsing water. Usually liquid rinse aid is added by using diaphragm pumps giving intermittent dosing. According to PCT/US93/03775, WO 94/18880, Ecolab Inc. rinse aid in cake form is used. The cake is leached by spraying with water to prepare a concentrate. The obtained solution is fed into a container placed in contact with the hot dish washing solution and, by that measure, heated to such a high temperature that micro organisms are killed or, at least, are not able to reproduce themselves. Besides earlier mentioned restrictions with respect to the composition of the rinse aid this dissolving method gives large variations in concentration as the cake's size and surface qualities change during the dissolution. These variations are equalized by that one simultaneously prepares concentrate for several rinses. This means that a concentrate with a low concentration of rinse aid will be kept at high temperature during a much longer time than the mentioned passage through a super heater. As will become obvious from this description, the purpose of this invention is to reduce deterioration of the rinse aid caused by prolonged storage in diluted state and at high temperature. According to PCT/US94/03194, WO 94/24253, Ecolab Inc. use is made of a combination of alkylene oxide modified sorbitol fatty acid ester and a defoaming agent. The alkylene oxide modified sorbitol fatty acid ester is a nonionic surface active agent. Several different defoaming agents, including fatty acids, fatty acid esters, phosphoric acid esters, sulfonated compounds and alkyl sulfates are, mentioned. Many of these compounds have anionic type of surface activity. High concentrations of active material are mentioned, but a closer scrutiny of the description including the examples shows, that this refers to cast cakes used in analogous way as the ones of the PCT application mentioned above. For liquid products the upper limit for active material is clearly less than 30% by weight. Water contents surpass 70%. See example 4 and table IV! US patent No. 5,273,677 refers to a rinse aid compounded of a low foaming surface active agent, a solubility improving system for the low foaming surface active agent and an anionic dispersion agent. As useful dispersion agents phosphate esters, sulphosuccinates, sodium naphtalene, alkyldiphenyloxide sulfonic acid and their salts are cited. No use examples for other anionic surface active agent than the sodium salts of alkyldifenyloxide sulfonic acid are presented. The aid may be composed as a liquid mixture containing 15 to 50% water. No nitrogen containing anionic surface active agents are mentioned. No recommendations for diluting to use solution are given. Surprisingly it has now been found, that changes in methods for mixing and addition of rinse aid may decrease required amounts of rinse aid and rinse water and ameliorate the rinsing result to eliminate spotting and streaking. Simultaneously sheeting action and drying become faster. This new method is radically different from current methods. According to this new method a liquid rinse aid, which is water-free or contains just small amount of water (0 to 30% by weight water, preferably less, for instance 0 to 20% by weight, 0 to 10% by weight or most preferred 0 to 5% by weight), is mixed with the rinse water just before use. The very concentrated rinse aid may be diluted either via an intermediate dilution to a 2 to 50% mixture or directly to a use solution containing 0.0005 to 0.5% by weight active material. By use solution it is meant the finally diluted solution used for the rinse. At predilution the storage time after dilution should be limited so that prediluted solution does not need to be stored more than 24 hours, preferably not more than 8 hours, and especially preferred 1 to 4 hours. This refers to storing at ambient temperature or less. If the storing temperature is higher, the storage should be limited to one hour at most, preferably to 10 to 30 minutes. Observations in automobile wash facilities show that a rinse aid according to example 2 below, which has been diluted by mixing 5 liters of the aid to 25 liters premix and then stored at ambient temperature initially has very high efficiency. Already after 24 hours the aid has lost enough efficiency to make the difference obvious even without possibilities of direct comparison. After 48 hours the efficiency becomes so low that complaints are more frequent than acceptances. The rinse aid should be added to the rinse water so that a fairly constant concentration during the entire rinsing time is maintained. This can be done by using a pump giving constant flow, for instance a hose pump. The rate of addition is adjusted so that an in time evenly distributed flow is obtained during the entire time of rinse water delivery. Further improvements may be obtained if the rinsing is done with softened water. Still better results may be obtained if rinsing is done with de-ionized water, for instance water treated by reverse osmosis (RO.). No confirmed theory exists, which can explain the dramatic improvement obtained by the new method. However, we interpret the results to mean that rinse aids at water dilution initially form an unstable micro-emulsion, which then gradually converts to a coarser and more stable emulsion. If the unstable micro-emulsion is spread over the surface, which is rinsed, before the conversion to a stable emulsion has had to time to become grave, the micro- emulsion will be broken at the surface proper. The fine distribution in the micro- emulsion gives a continuous layer of rinse aid on the surface. The ideal is said to be a mono-molecular layer. The new method approaches this ideal. On the other hand, if the conversion has had time to make the stable emulsion particles the most common species large parts of the rinse aid will run off, without positive effect on the drying, and small water puddles form on the surface. After drying the rinse aid in those drops will remain and give spotting, streaking and filming. Increased amounts of rinse aid often make the situation worse. This hypothesis is supported by observations showing that a concentrate of rinse aid (less than 30% water by weight) at mixing with water initially forms a completely clear liquid. This happens no matter if the dilution is done to for instance 20% active or to 0.001% active material. After a certain time, a few minutes to some hours, a manifest haziness starts to appear. The conversion is very fast at high dilution and substantially slower at smaller dilution. High temperature leads to faster development of the haziness. Tests have shown that the impairment of the sheeting action of the rinse aid runs in parallel to the increasing haziness. A prepared use solution has its optimum effect at immediate use. Already one or two-hour storage causes a manifest impairment. After storing over night the solution has very low efficiency although it does not show any obvious instability. At predilution to, for instance, a 25% by weight intermediate solution and final dilution just before use the shelf-life is better and some effect may remain even after some months storage of the intermediate solution. As the impairment of the sheeting action obviously is connected to water dispersion the water content in the concentrate should be kept very low. Tests show that no grave influence can be observed at comparatively short storing (some months) and moderate storage temperatures if the water content is below 30% by weight. For reasons of safety, lower contents are preferred, for instance 20, 10 or even better 5% by weight. Alcohol does not cause the same negative effect and may with advantage be used as viscosity adjusting additive if required. Small amounts of water improve the dissolution rate. Thus completely water free products are less preferred if no special regard can be taken to dissolving at compounding and addition. For instance, a device, for use at predilution of a rinse aid according to the invention, may comprise an ejector pump, which aspires and mixes a super-concentrate, containing less than 30% by weight water and more than 40% by weight active material, with water to a 2 to 10% solution, in a small container of some liters serving as pump sump for the diluted rinse aid solution and devices for adding the rinse aid solution to the hot water after the super-heater and just before the rinse nozzles. The container should be as small as possible, so as not to be inconvenient and so that long storage periods are avoided. This device is suitable for dish washing machines. Dosing may be done via a dosing pump, which, in its simplest form, may with advantage be a hose pump with adjustable rotation rates. In automobile wash plants, where tap water is used for the rinse, a corresponding arrangement with a small container for predilution and addition just before the spreading nozzles can be used. If the pressure is sufficiently high in the water pipe, so that a small pressure drop before the nozzles can be accepted, addition of the prediluted rinse aid via siphon action may be an useful alternative. However, a preferred alternative is to use a high pressure pump to get higher pressure and a more even distribution of rinse water over the entire surface of the automobile. Here it is better if the rinse aid is mixed in before the pump. A suitable arrangement consists of a small container holding the quantity of rinse water needed for one automobile. The preparation of use solution for the rinsing starts automatically at a suitable signal from the wash process. Such a signal can be taken from opening the front door, prepayment to start the wash machine, when the wash machine starts moving or from another suitable moment of the wash process. Between washes the preparation container is left empty. The preparation can be done as described above for dilution. This new method has required development of new rinse aids adjusted to fit the method. Compositions differing from conventional rinse aids with respect to reduced water content only often form gelatinous lumps at dilution. Such lumps are difficult to disperse. Common for the new compositions is that no conventional hydrotropic substances, such as toluene, xylene or cumene sulfonates, with high water solubility are used. Instead hydrophobic, low foaming nonionic surface active agents of modern types with good qualities regarding biological degradation are combined with fatty acid esters and/or solvents and an ionic surface active agent with good qualities as emulsifiers. The ionic surface active agent should contain nitrogen atoms and may be cationic, which is preferred concerning automobile wash plants, or anionic, which may be suitable at use in dish washing machines. Ampholyte and/or zwitterionic surface active agents may be used but are more expensive. An especially suitable group is anionic surface active agents that contain nitrogen atoms. En typical representative for this group is sodium lauryl sarcosinate. The basic qualities of these surface active agents are not sufficiently strong to make them ampholytic or zwitterionic surface active agents. However, the nitrogen group is carrying a partial cationic charge, which allows the surface active agents to stick to surfaces much better than, for instance the anionic surface active agents used according to US 5,273,677. Therefore they contribute in a positive way to the sheeting action, in contrast to the mentioned other anionic surface agents, which have a mainly negative effect with respect to good sheeting action. Especially suitable nonionic surface active agents for combining with anionic surface active agents are fatty alcohols, which have been ethoxylated and propoxylated. In compositions with cationic surface active agents short chain ethoxylated fatty alcohols may be suitable. The proportion between the content of nonionic surface active agent and ionic surface active agent changes dependent on the use and if the ionic surface active agent is anionic or cationic. In compositions with anionic surface active agent intended for rinsing after machine dish washing the nonionic part is predominant and may be more than 95% by weight of the surface active agent combination. A suitable proportion of nonionic surface active agent to anionic surface active agent may be from 4:1 to 40:1. In agents with cationic surface active agent intended for rinsing after an automatic car wash the cationic part is predominant. A suitable proportion cationic surface active agent to nonionic surface active agent may be from 3:1 to 40:1. A suitable composition for use after machine dish washing contains 60 to 95% by weight of low foaming nonionic surface active agent of the type fatty alcohol ethoxy/propoxylate and 1 to 10% by weight of anionic surface active agent of the sarcosinate type and 0 to 30% by weight water. In cationic products for automobile washing solvents of the white spirit and non- aromatic white spirit may be present. If this type of product is used for machine dish washing the mentioned solvents should be replaced wholly or partly by fatty acid esters. Such compositions may be used for automobile washing, too, but are more expensive than solvent containing products. Composition containing cationic surface active agents should be made weakly acid to reinforce their cationic character. Example 1. A restaurant dish washing machine consumed 10 to 12 liters per week of a rinse aid containing 25% active material. This corresponds to 2.5 to 3 kilos 100% rinse aid. 0.5 ml rinse aid per liter rinse water was used. Thus, the content of water free rinse aid became 0.0125% by weight. The rinse aid was dosed by a diaphragm pump. The addition took place before the super-heater. The equipment was completed with a 2 liters container and a hose pump. The container was filled with diluted rinse aid by an ejector pump, connected to a water pipe. The pump aspired rinse aid from a can containing a rinse aid solution with 96% by weight water free material. A hose pump was connected to the container to feed rinse aid to the supply pipe for hot rinse water from the super-heater to the rinse nozzles in a continuous flow during the entire rinsing time (about 20 sec). A new rinse aid, suitable for this new method, was developed. This aid contains: Water 4.5 % by weight Ethanol/isopropanol 5% by weight MIRAVON B 79 R 26% by weight MIRAVON B 12 DF 60% by weight ORAMIX L30 4.5% by weight MIRAVON™ and ORAMIX™ are registered trade marks. MIRAVON B 79 R and MIRAVON B 12 DF are two different varieties of biologically easily degradable, low foaming, nonionic surface active agents and consist of short chained fatty alcohols, which have been ethoxylated and propoxylated. ORAMIX L30 stands for sodium lauryl sarcosinate. The consumption of rinse aid could be cut down to about 1 liter 96% agent per week, i.e. to about 0.96 kilos, which corresponds to one third of earlier consumption. Simultaneously the rinse result became much better. No tendencies to streaking could be seen. Tests have shown that the more even distribution of rinse aid may admit cutting down the amount of rinse water from about 6 liters to about 4 liters per basket tableware. This means that the costs of rinse water and heating of rinse water are reduced by one third. Simultaneously a further saving of rinse aid with one third is obtained as compared with the new method carried through with an unchanged rinse water volume. As the costs for installation of the new dosing equipment are low, the installation will soon generate economic gains, besides the large improvement with respect to the rinsing result. Simultaneously the consumption of chemicals and, in the complete variety, water and energy for heating the water will decrease. Example 2. An automatic automobile wash plant used, for each wash, about 10 liters rinse water containing 0.3% sheeting action aid, the active components of which comprised nonpolar solvents and surface active agents. The content of active material in the concentrate was about 30 % by weight. Thus, the consumption for each washed automobile was 36 g concentrate corresponding to 10.8 g active material. The rinse aid was added before the percolator and heated with the rinse water. The result of the rinsing was judged as less satisfactory as the sheeting action was bad with spotting, streaking and filming as consequences. The sheeting action aid was exchanged against some different newly developed compositions containing 15 to 35% cationic surface active agent of the type quaternary soya/cocosamidoamine, 1 to 5 % hydrophobic nonionic surface active agent(C11 , 3EO) and 30 to 75% nonpolar solvent consisting of nonaromatic white spirit and fatty acid esters. Simultaneously the method for adding the rinse aid was changed. When the wash process started a container provided with a floating body was filled with a suitable quantity water and rinse aid for the rinsing of one automobile (8 to 15 liters). At preparation rinse aid was drawn from a can by siphon effect caused by the added water. From the container the water was pumped to the rinse nozzles and spread over the automobile. The quantity rinse aid was cut down to 2 to 3 g per automobile calculated as the sum of surface active agents and nonpolar solvents. No comparison between different new compositions was done, but the rinsing results with the new method were compared with earlier results and constantly judged as much better, despite the fact that the dosing had been reduced to less than 30% of the earlier one.

Claims: Patent claims 1. Method for rinsing smooth surfaces with water containing rinse aid characterized by that the rinse solution is prepared in direct connection to the use by dilution of a liquid, very concentrated rinse aid containing at most 30% by weight water, so that the time during which the diluted rinse aid may be influenced by dilution and/or high temperature is reduced to at most 24 hours, preferably at most 8 hours, and especially preferred at most 1 hour, and high costs for transport and storing of diluted rinse aid are avoided. 2. The method of claim 1 characterized by that the liquid, very concentrated rinse aid is prediluted to 2 to 20% by weight active material (calculated as the sum of surface active agents and nonpolar solvents) and that the prediluted rinse solution is added to the rinse water in a continuous stream during the entire rinsing time. 3. The method of claim 1 characterized by that the very concentrated rinse aid is direct-diluted to use solution in batches which are volume adjusted for direct use. 4. The method of claim 2 and 3 characterized by that the dilution of the very concentrated rinse aid is done via an ejector pump, for introducing the rinse aid, connected to a water supply system and that the diluted rinse aid is stored in between in a pump sump. 5. Rinse aid intended for use at the method of claim 1 characterized by that it is liquid and contains a combination of one or more hydrophobic nonionic surface active agents and a nitrogen containing ionic surface active agent, which may be anionic, amfolytic, zwitterionic or cationic and may be direct-diluted to use solution from a super concentrate with at most 30% by weight water.

Inventors: ERIKSSON TORD GEORG, ERIKSSON, TORD, GEORG
Applicants: ERIKSSON TORD GEORG, ERIKSSON, TORD, GEORG
Application year: 1998
Main classification: A47L15
IPC codes: A47L15, C11D1