WASHING PROCESS

Abstract: Washing items are washed simultaneously with softening washing water comprising alkali metal ion and at least one of carbonate ion and bicarbonate ion. The washing water before being softened is obtained by electrolyzing an aqueous solution of sodium hydrogencarbonate having a pH of 9.5 or more and an electric conductivity of 150mS/m or more. The softened washing water has a total hardness of 40ppm or less.

Description: FIELD OF THE INVENTION The present invention relates to a new washing process suitable to washing clothes, tableware, medical equipments and washing hands, etc. BACKGROUND OF THE INVENTION Surfactant, such as chemicals and soap, have been heretofore been used for washing clothes, tableware, medical equipment, toilets, etc., however, there have been problems of causing chapping hands when washing, a safety issue on body by residual detergent on washing items, and residual harmful substances after a treatment of discharging water, etc. Inventors of the present invention have proposed a so-called non-detergent washing method by using electrolyzed water as disinfectant detergent (JP-A-8071131). It utilizes a protein removing effect of alkaline electrolytic water obtained by electrolyzing water comprising electrolyte and a disinfection effect of acid electrolytic water, which have been widely noticed as substitution of conventional chemicals and surfactant. When applying such a kind of detergent to purposes of washing clothes and dishes, etc., it is on the assumption to have detergency comparable to or more excellent than the conventional detergent has. It is necessary, when designing detergent, to construct in terms of washing mechanism what kind of property should be a controlling factor. It is also required to be harmless to human body even if a user takes it by mistake, to be safe not to cause chapped skin when touched by hands and to be easily handled. Furthermore, it is required that the waste water containing the detergent after washing clothes and dishes, etc. excels in being easily handled able to be discharged as it is to the living environment without any special treatment, that is, excels in easy treatment of discharged water. EP-A-0 419 036 discloses a process according to the preamble of claim 1, wherein the washing water, which contains a conventional detergent, is softened by adding in solution sodium carbonate, among others. JP-A-9250079 discloses a process of cleaning textile products wherein, for the purpose of causing little soil redeposition and decreased staining of washing tub with soap scum, water containing 1-1,000ppm of a builder is used as washing water. EP-A-0 503 889 discloses a method of preparing water for, among others, washing applications by electrodialysis using NaHCO 3 as electrolyte, whereby calcium carbonate precipitates to give softened water. DISCLOSURE OF THE INVENTION An object of the present invention is to provide a washing process having detergency comparable to or more excellent than that of a washing process using conventional detergent, being low at cost, excelling in safety, being easily handled, and thereby the waste water is easily treated. The inventors of the present invention diligently studied washing mechanism and found that it was possible to obtain detergency comparable to detergent of the prior art, such as surfactant, or increased detergency by softening washing water, and with a cleanser effect and adsorptive effect of compositions produced at the time of softening the washing water. They also found that remarkable detergency was attained by softening a solution comprising alkali metal ion and carbonate ion and/or bicarbonate ion. (1) Namely, a washing process of the present invention washes items to be washed simultaneously with softening washing water comprising alkali metal ion and at least one of carbonate ion and bicarbonate ion. Mainly, calcium ion Ca 2+ and magnesium ion Mg 2+ give a negative influence on detergency. In the present invention, since the washing water comprises at least one of carbonate ion CO 3 2- and bicarbonate ion HCO 3 - , calcium ion Ca 2+ and magnesium ion Mg 2+ bond with them and the existing ratio of the calcium ion Ca 2+ and magnesium ion Mg 2+ in the washing water becomes small. Therefore, the detergency is not decreased. In addition to this, calcium carbonate CaCO 3 or magnesium carbonate MgCO 3 precipitated as a result of bonding calcium ion Ca 2+ and magnesium ion Mg 2+ with magnesium carbonate ion CO 3 2- physically removes dirt/stain by the cleansing effect and adsorption effect thereof, thus, contributes to increase the detergency.Namely, the present invention is not simply a washing method using softened water nor to soften washing water, but also to generate compositions capable of physically removing dirt/stain simultaneously with softening the water.Accordingly, when pouring the washing water comprising alkali metal ion and at least one of carbonate ion and bicarbonate ion together with washing items into the washing bath, calcium ion and magnesium ion contained in the washing water bond with the carbonate ion and bicarbonate ion to precipitate calcium carbonate and calcium bicarbonate. As a result, the washing water in the washing bath is softened and calcium carbonate, etc. having a cleansing effect and adsorption effect is generated at the same time. (2) The alkali metal ion according to the present invention is obtained by making aqueous solution of alkali metal sodium. As the alkali metal ion, potassium salt, sodium salt, lithium salt, etc. are mentioned in terms of improving detergency. Especially, potassium salt and sodium salt are preferable for being inexpensive and easy to obtain and excelling in safety and treatment of waste water. The carbonate ion according to the present invention is obtained by making an aqueous solution of alkali metal sodium carbonate, and the bicarbonate ion is obtained by making an aqueous solution alkali sodium bicarbonate. As the alkali metal sodium carbonate, for example, sodium carbonate [Na 2 CO 3 ], potassium carbonate [K 2 CO 3 ], lithium carbonate [Li 2 CO 3 ], etc. can be mentioned, and as the alkali metal sodium bicarbonate, for example, potassium hydrogencarbonate [KHCO 3 ], sodium hydrogencarbonate [NaHCO 3 ], etc. can be mentioned.The solvent for dissolving the above alkali metal ion and at least one of carbonate ion and bicarbonate ion is not specifically limited, and a variety of waters, for example, tap water, well water, soft water, refined water, pure water, or mixed water of these, etc. can be used. (3) In the present invention, the washing water before being softened has a pH of 8.5 to 12.0, preferably 9.5 to 11.0, more preferably 10.0 to 11.0. By setting the pH 8.5 or more (preferably 9.5 or more, more preferably 10.0 or more), it becomes preferable in terms of promoting to bond calcium ion and magnesium ion with carbonate ion and bicarbonate ion. By setting the pH 12.0 or less (preferably, 11.0 or less), it becomes preferable in terms of safety against chapped hands, etc. and treatment of waste water. Furthermore, in the present invention, the concentration of alkali metal ion, that of carbonate ion, and/or that of bicarbonate ion in the washing water before being softened are preferably within predetermined ranges, and such concentrations of ions can be indirectly specified by an electric conductivity (EC). Namely, the electric conductivity EC of the washing water before being softened is 100mS/m or more, more preferably 150mS/m or more. By setting the electric conductivity at such a high range, sufficient concentration of ions can be secured for invalidating Ca 2+ and Mg 2+ in the aqueous solution by bonding them with CO 3 2- and HCO 3 - .The washing water before being softened can be obtained by electrolyzing, for example, a sodium hydrogencarbonate solution. At this time, when using a water flowing type electrolyzing apparatus having a high generation performance, cathode electrolytic solution generated in a cathode chamber is preferably set to have a concentration able to be used as washing water as it is in terms of handling. While, when using a batch type electrolyzing apparatus having a low generation performance, it is preferable to generate electrolytic solution of a high concentration and to dilute the same for using in terms of reducing the generation costs. The solvent for diluting at this time is not specifically limited and easily obtainable tap water, etc. can be used. (4) In the washing process of the present invention, the process of softening the washing water comprising alkali metal ion and at least one of carbonate ion and bicarbonate ion includes a process of promoting the softening of the washing water. As such a process of promoting to soften water, a process of applying heat energy to the washing water to be softened, a process of physically stirring or airing the washing water to be softened, a process of securing time for water softening reaction by leaving the washing water to be softened still, etc. can be mentioned as examples.By applying heat energy to the washing water, for example, by heating the washing water or generating the washing water under a high temperature state, an activity level of ions becomes high, the reaction of calcium ion and magnesium ion with carbonate ion and bicarbonate ion is promoted, and water softening is completed in a short period of time.Also, when performing stirring or airing, a collision frequency between ions mechanically increases, so the reaction between magnesium ion and carbonate ion and/or bicarbonate ion is promoted and water softening is also completed in a short period of time by this. Also, other than these forcible processes, a sufficient reaction time can be secured by leaving the washing water still and thereby water softening can be promoted, as well. (5) The total hardness of the softened washing water is 35ppm or less, preferably 15ppm or less, more preferably 10ppm or less. By setting the total hardness within this range, further increase of detergency can be expected. (6) In the present invention, in order to reduce the total hardness in a short time to further increase the detergency, it is preferable to add coagulation agent or chelating agent to the above softened washing water having a reduced total hardness. It is because, by adding the coagulation agent or chelating agent at this timing, the reduction of the total hardness can be attained in a short time. As the coagulation agent, for example, aluminum sodium sulfate (sodium alum), etc. can be mentioned, and as the chelating agent, EDTA, zeolite, etc. are mentioned as examples. Also, in order to reduce the total hardness in a short time for further increased detergency, it is preferable to add fatty acid to the above softened washing water having a reduced total hardness. It is because, by adding fatty acid at this timing, reduction of the total hardness can be attained in a short time. As the fatty acid, oleic acid, etc. can be mentioned as an example. A timing of adding the coagulation agent, chelating agent or fatty acid is not specifically limited, however, preferably, it is added when the total hardness of the washing water becomes 40ppm or lees (preferably 15ppm or less, more preferably 10ppm or less). BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic structural view of a washing apparatus for carrying out an embodiment of the process of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION The reference number 4 in FIG. 1 indicates a washing bath and the reference number 5 indicates a faucet of water supply. Tap water is supplied from the faucet 5 to the washing bath 4 via a pipe 41, and the tap water is supplied and stopped by operating a solenoid valve 42 provided to the pipe 41. The operation of the solenoid valve 42 is carried out by an instruction signal from a main control system (main micro-computer) outside the figure. A batch type electrolyzing cell 1 is built in in this washer and a pair of electrode plates 31 and 32 are provided putting a diaphragm (for example, a cation exchange film) between them. Then, an anode electrode is applied to the electrode plate 31 and a cathode electrode is applied to the electrode plate 32, respectively from a micro computer (sub-control system) 6 via a switch outside the figure. The electrolytic solution generated in a cathode chamber 13a being provided with the cathode electrode plate 32 is supplied to the washing bath 4 via a pipe 7a being provided with a solenoid valve 8a. In the same way, the electrolytic solution generated in an anode electrode chamber 13b being provided with the anode electrode plate 31 is supplied to the washing bath 4 via a pipe 7b being provided a solenoid valve 8b. The control of opening/closing of the solenoid valves 8a and 8b is carried out by an instruction signal from the micro computer 6. A pipe 43 branched from the pipe 41 of the above faucet 7 is provided with a solenoid valve 44, and further branched on the downstream side, and supplies the tap water respectively to the cathode chamber 13a and anode chamber 13b of the electrolyzing cell 1. Also, an electrolyte adding apparatus 9 for adding electrolyte to the respective pipes to the cathode chamber 13a and anode chamber 13b is provided, and a predetermined amount of electrolyte, such as sodium hydrogencarbonate, is supplied to the tap water introduced to the cathode chamber 13a and anode chamber 13b by driving a pump 91. Note that the control of opening/closing of the solenoid valve 44 provided to the pipe 43 and driving/stopping of the pump 91 of the electrolyte adding apparatus 9 are carried out by an instruction signal from the micro computer 6. Furthermore, a sensor 10 is provided in the cathode chamber 13a for measuring a pH and EC, and an output signal (pH and EC values) from the sensor 10 is sent to the micro computer 6. In such a washer, the solenoid valve 44 is opened first to supply tap water to the cathode chamber 13a and anode chamber 13b, and the pump 91 is driven at the same time to add electrolyte to the tap water to the cathode chamber and the anode chamber. Then, a voltage is applied to the both electrode plates 31 and 32 and the electrolyzation continues until the pH value and the EC value of the electrolytic solution in the cathode chamber 13a measured by the sensor 10 respectively become predetermined values or more. When the pH value and the EC value by the above sensor 10 become predetermined values or more, applying of voltages is stopped, an instruction from the micro computer of the washer is waited for opening the solenoid valves 8a and 8b, and electrolytic solution at the cathode side generated in the cathode chamber 13a is supplied to the washing bath 4. The washing water is automatically added to the washing bath 4 in this way, so washing items are put in and usual washing is carried out. When discharging the waste water after washing, a discharging valve 45 of the washing bath 4 is open. Prior to that, however, the electrolytic solution at the anode side may be supplied to the washing bath 4 by opening the solenoid valve 8b to sterilize the laundry and at the same time to neutralize the discharged water. Note that the electrolytic solution generated at the anode side generated in the anode chamber 13b may be kept as it is without being supplied to the washing bath 4 or may be discharged as it is. Also, in addition to this, by preparing a means to measure the total hardness inside the washing bath 4 (or by providing a timer instead of this for measuring a predetermined time to be passed), coagulation agent, chelating agent or fatty acid may be added from the adding apparatus 20 when the total hardness reaches to a predetermined value. A washing process of the present invention will be explained based on a specific embodiment below. Example 1 A batch type electrolyzing apparatus 1 shown in FIG. 1 was used, after respectively supplying 1 liter of tap water (municipal tap water in Fujisawa city, pH 7.6, EC 17.5mS/m, calcium hardness 55ppm, total hardness 75ppm, water temperature 3.4°C) to the both electrolyzing chambers 13a and 13b, 36g of sodium hydrogencarbonate (NaHCO 3 ) was respectively added to the cathode camber 13a and anode chamber 13b, a voltage was applied so as to flow a constant current of 15A to the both electrode plates, and electrolyzation was carried out for 30 minutes. Note that a cation exchange film was used as a diaphragm and the distance between the electrode plates 31 and 32 was set 5mm. Note that a pH was measured by using a pH meter (trade name of D-13, manufactured by Horiba Ltd.), an EC was measured by using an EC meter (trade name of CM-14P, manufactured by TOA Corporation) and a hardness was measured by using a hardness meter (trade name of WAD-Ca, manufactured by Kyoritu Physical and Chemical Research Institute, measurement accuracy in color comparing mode was 5ppm). As a result, electrolytic solution at the cathode side having a pH of 10.55 and an EC of 6000mS/m or more was obtained. By diluting this by 30 times with tap water, washing water before being softened having a pH of 10.7, an EC of 196.1mS/m, a calcium hardness of 40ppm, a total hardness of 60ppm and a water temperature of 20°C was obtained. Mixed stain of china ink and olive oil, blood, cacao butter (animal and vegetable oil), red wine, and mixed stain of blood, milk and china ink were allowed to adhere to cotton fabric samples, respectively (EMPA101, 111, 112, 114, 115 and 116). The stained fabric samples were washed with a domestic washer of double bath type (trade name of ES-25E, 2.5kg type, manufactured by Sharp Corp.) for 20 minutes, spin-dried and dried by a drier. The result of a whiteness index and detergency ratio of the fabric samples after washing is shown in Table 1. Note that the "whiteness index" is an average of ten points on two sides of the artificially stained fabric measured by a whiteness index measure (trade name of CR-14, Whiteness Index Color Reader, manufactured by Minolta Co.,Ltd.). while, the "detergency ratio" as defined below was calculated. Detergency ratio % = (whiteness index of stained fabric after washing - whiteness index of stained fabric before washing) ÷ (whiteness index of unstained fabric - whiteness index of stained fabric before washing) × 100 Also, moisture type artificially stained fabrics (manufactured by The Foundation of Washing Science Association) were washed with the washing water of the present embodiment by using the same washer as the above for 20 minutes. The result of the detergency ratio of the fabrics after washing is shown in Table 2. Note that the "detergency ratio" is calculated in the same way as the above. Example 2 Other than setting the temperature of tap water for diluting by 30 times the electrolytic solution at the cathode side generated at 40°C, conditions were the same as in the Example 1. The obtained washing water before being softened had a pH of 10.5, an EC of 207.0mS/m, a calcium hardness of 40ppm, a total hardness of 60ppm and a water temperature of 40°C. The results thus obtained are shown in Table 2. Example 3 Other than leaving the obtained washing water before being softened for 6 hours, conditions were the same as in the Example 1. The obtained washing water before softening had a pH of 10.7, an EC of 205.0mS/m, a calcium hardness of 40ppm, a total hardness of 60ppm, and a water temperature of 20°C. The results thus obtained are shown in Table 2. Example 4 Other than adding 12g of EDTA 15 minutes after starting washing, conditions were the same as in the Example 1. Note that the total hardness of the water inside the bath 15 minutes after starting washing was 30ppm. The results thus obtained are shown in Table 2. Example 5 Other than adding 15cc of oleic acid 15 minutes after starting washing, conditions were the same as in the Example 1. Note that the total hardness of the water inside the bath 15 minutes after starting washing was 30ppm. The results thus obtained are shown in Table 2. Comparative Example 1 The same stained fabrics as in the Example 1 were washed using a commercially available synthetic detergent for washing (Attack, Kao Corporation) and a whiteness index and the detergency ratio were calculated. The results thus obtained are shown in Table 1. Also, moisture type artificially stained fabrics (manufactured by The Foundation of Washing Science Association) were washed in the same way as in the Example 1 using the commercially available synthetic detergent for washing in the Comparative Example 1, and the detergency ratio was calculated. The results thus obtained are shown in Table 2. Comparative Examples 2 and 3 Other than changing a pH and EC of the washing water before being softened by adjusting the electrolyzing conditions, conditions were the same as in the Example 1. The results thus obtained are shown in Table 2. stained fabric Example 1 Comparative Example 1 whiteness index (%) detergency ratio (%) whiteness index (%) detergency ratio (%) before washing after washing before washing after washing china ink, olive oil 41.2 48.6 15.5 42.0 48.7 14.3 blood 40.4 86.1 94.0 40.8 64.6 49.4 cacao 54.0 67.1 37.4 53.6 60.9 20.6 red wine 68.7 76.6 38.9 69.4 77.0 38.8 blood, milk, china ink 36.9 50.0 25.1 37.6 49.3 22.8 before being softened after softening detergencyrati o note pH EC total hard ness total hard ness Example 1 10.7 196.1 60 30 36.5 stirring Example 2 10.5 207.0 60 30 44.4 heating Example 3 10.7 205.0 60 30 39.3 leaving still Example 4 10.7 195.3 60 0 49.0 Chelating agent Example 5 10.7 196.2 60 - 43.7 fatty acid Comp. Example 1 9.4 22.6 60 - 41.7 Comp. Example 2 8.3 114.5 60 60 27.8 Comp. Example 3 10.4 48.6 60 50 27.8 It has been confirmed from the results that a washing process of the present invention shows the cleaning effect comparable to or more excellent than that of the commercially available synthetic detergent for washing. Note that the washing water of the Examples 1 to 5 has no problems at all as to safety and treatment of the waste water after washing.

Claims: A washing process including a step of washing items to be washed simultaneously with softening washing water comprising alkali metal ion and at least one of carbonate ion and bicarbonate ion, characterized in that said washing water comprises said alkali metal ion and said at least one of carbonate ion and bicarbonate ion as essential washing action ingredient and comprises no surface-active agent as washing action ingredient, wherein the washing water before being softened has a pH of 8.5 to 12.0 and an electric conductivity of 100 mS/m or more, and in that the process includes a process of promoting the softening of the washing water until the washing water has a total hardness of 35ppm or less. The washing process as set forth in claim 1, wherein the washing water before being softened has a pH of 10.0 to 11.0 and an electric conductivity of 150 mS/m or more. The washing process as set forth in claim 1 or 2, wherein said washing water before being softened is electrolyzed aqueous solution of sodium hydrogen carbonate. The washing process as set forth in claim 1, wherein said water softening process includes a process to add coagulation agent or chelating agent after the total hardness of the washing water before being softened becomes 40ppm or less. The washing process as set forth in claim 1, wherein said water softening process includes a process to add fatty acid after the total hardness of the washing water before being softened becomes 40ppm or less.

Inventors: ARAI KAZUYOSHI, MIYAMAE KAZUHIRO, NAITOH TATSUYA, SATOH FUMITAKE, SEO TOMOKI, YANAGIHARA TOMOYUKI, ARAI, KAZUYOSHI, MIYAMAE, KAZUHIRO, NAITOH, TATSUYA, SATOH, FUMITAKE, SEO, TOMOKI, YANAGIHARA, TOMOYUKI, ARAI, Kazuyoshi, Miz Co., Ltd., MIYAMAE, Kazuhiro, Miz Co., Ltd., NAITOH, Tatsuya, Miz Co., Ltd., SATOH, Fumitake, Miz Co., Ltd., SEO, Tomoki, Miz Co., Ltd., YANAGIHARA, Tomoyuki, Miz Co., Ltd.
Applicants: MIZ CO LTD, MIZ CO., LTD.
Application year: 1999
Main classification: B08B3
IPC codes: C11D7, D06F35, C11D11, C11D3