Automatic dishwashing method

Abstract

To provide an optimum cleaning method excellent in washability that keeps the inside of a preliminary cleaning apparatus sanitary in a cleaning system for automatically conducting a preliminary cleaning step through a main cleaning step.SOLUTION: An automatic tableware cleaning apparatus system equipped with a preliminary cleaning apparatus and a main cleaning apparatus each of which has a tank to store a cleaning fluid, includes a mechanism with which the cleaning fluid flows from the main cleaning apparatus to the tank of the preliminary cleaning apparatus. The cleaning fluid contains a component (A), a silicate, and a component (B), a macromolecular dispersing agent, in the cleaning step in the preliminary cleaning apparatus. The cleaning method is characterized in that the cleaning fluid has a content of the silicate (A) of 0.001 mass% or more and 0.04 mass% or less and a mass ratio (B / A) of the macromolecular dispersing agent (B) to the silicate (A) of 0.5-10.SELECTED DRAWING: None

Description

Detailed Description of the Invention [Technical field]

[0001] The present invention relates to an automatic dishwashing machine system comprising a pre-washing device and a main washing device, each of which has a tank for storing washing liquid, and a mechanism for allowing washing liquid to flow from the main washing device into the tank of the pre-washing device, and relates to a method for keeping the inside of the pre-washing device hygienic and effectively washing dishes. [Background technology]

[0002] In restaurants and cafeterias, commercial dishwashers are used to wash a large amount of dishes in a short time. In washing dishes, it is important to remove leftover food from the dishes (scraping) and to soak the dishes in hot water for a certain period of time (pre-soaking) to make the dirt easier to remove, in order to remove dirt efficiently. For this reason, in places where dishes for a large number of people are washed, such as in factory or office cafeterias, hospital washing rooms, and food service centers, a large soaking tank is installed and a system is established in which the cleared dishes are soaked for a certain period of time and then the dishes are automatically washed continuously using a conveyor-type washing machine. On the other hand, in chain restaurants and small-scale cafeterias, depending on the location, the kitchen space is narrow, so a batch-type automatic dishwasher may be used, and the pre-processing steps of scraping and pre-soaking are performed, and the pre-washed dishes are set on racks and then set in the batch-type automatic dishwasher must be performed by workers, which requires a lot of labor and is a major problem.

[0003] In order to reduce the burden on workers, even in small stores, various washer manufacturers are working on the development of washer machines that perform pre-washing automatically. For example, as shown in Patent Document 1, there is a machine that combines a washing device with a similar mechanism in front of a batch-type automatic dishwasher. In this case, since the purpose of the pre-wash washer is to scrape off leftover food and soften dirt adhering to dishes, a structure is adopted in which only hot water is circulated without adding detergent, or dishwashing water is injected from the automatic dishwasher used for main washing (hereinafter referred to as the main washing machine) into the pre-wash washer (hereinafter referred to as the pre-wash machine) to reuse the dishwashing water.

[0004] In this way, when detergent is not fed into the pre-washer, or when part of the cleaning liquid used in the main washer is fed into the tank of the pre-washer, the inside of the pre-washer becomes dirty, the hardness components of the water precipitate, causing scale to adhere, and creating an environment prone to the generation of so-called pink slime, which is a breeding ground for microorganisms, resulting in a problem that the inside of the pre-washer becomes unsanitary. In particular, in a mechanism in which part of the cleaning liquid used in the main washer is fed into the tank of the pre-washer, if the cleaning liquid is alkaline, the cleaning liquid is diluted in the pre-washer, making it more prone to scale adhesion.

[0005] Conventionally, cleaning agents for pre-washing and pre-soaking have been proposed, but since the pre-washing is assumed to be performed by a person, most of them are neutral and mainly made of surfactants, taking safety into consideration so that there is no problem even if the cleaning solution comes into contact with the person. For example, in Patent Document 2, a specific nonionic surfactant and a solvent are contained as main components in the composition, and in Patent Document 3, the pH is set to be near neutral, taking into consideration the rough hands of workers.

[0006] Furthermore, as for detergents for automatic dishwashers used in the present washing machine, detergent compositions containing an alkaline agent, a chelating agent, and a polymer, as disclosed in Patent Document 4, are generally used. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Special Publication No. 2012-511995 [Patent Document 2] JP 2018-59017 A [Patent Document 3] JP 2019-94420 A [Patent Document 4] JP 2007-332245 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, when detergents for pre-washing or pre-soaking are mainly surfactants or the cleaning liquid is neutral, there is a problem that the cleaning performance for protein stains is poor. Also, if a supply device is installed in the pre-washing machine to automatically supply the detergent for pre-washing or pre-soaking in addition to the detergent for the main washing machine, two supply devices for the detergent for the main washing machine and the detergent for the pre-washing machine are required, which is uneconomical.

[0009] Furthermore, in an automatic washing system in which the washing solution from the main washing machine is pumped from the tank of the main washing machine to the tank of a pre-washing machine and reused, if conventional detergents for automatic dishwashers are used in the main washing machine, if a sufficient concentration cannot be maintained in the pre-washing machine, the effect of the chelating agent will be weakened, causing scale to form in the pre-washing machine or the alkaline agent to be diluted, reducing its cleaning ability, causing the inside of the pre-washing machine to become dirty and unsanitary. [Means for solving the problem]

[0010] As a result of extensive research by the inventors to solve the above problems, the inventors have completed the following invention. [1] An automatic dishwashing system comprising a preliminary washing device and a main washing device, each having a tank for storing washing liquid, and a mechanism for allowing washing liquid to flow from the main washing device into the tank of the preliminary washing device, characterized in that in a washing step in the preliminary washing device, the washing liquid contains a silicate as component (A) and a polymeric dispersant as component (B), the content of the silicate of component (A) in the washing liquid is 0.001 mass% or more and less than 0.04 mass%, and the mass ratio (B / A) of the polymeric dispersant (B) to the silicate (A) is 0.5 to 10. [2] The cleaning method according to [1], wherein the molar ratio of M2O (M2O is an alkali metal oxide) and SiO2 constituting the silicate (A) is M2O / SiO2=1 to 4. [3] The cleaning method according to [1] or [2], wherein the (B) polymer dispersant is one or more selected from the group consisting of acrylic acid polymers and salts thereof, maleic acid polymers and salts thereof, acrylic acid-maleic acid copolymers and salts thereof, poly-α-hydroxyacrylic acid and salts thereof, acrylic acid-maleic acid-polyethylene glycol copolymers and salts thereof, olefin-maleic acid copolymers and salts thereof, and acrylic acid-sulfonic acid copolymers and salts thereof. [4] The cleaning method according to any one of [1] to [3], wherein a mass ratio (B / A) of the (B) polymer dispersant to the (A) silicate is 1.5 to 5. [5] An automatic dishwashing system comprising a preliminary washing device and a main washing device, each having a tank for storing washing liquid, and a mechanism for allowing washing liquid to flow from the main washing device to the tank of the preliminary washing device, wherein in a washing step in the main washing device, the washing liquid contains a silicate as component (A), a polymeric dispersing agent as component (B), and further a chelating agent as component (C), the content of the silicate as component (A) in the washing liquid is 0.005% by mass or more and less than 0.1% by mass, the content of the chelating agent as component (C) in the washing liquid is 0.01% by mass or more and less than 0.1% by mass, and the mass ratio (B / A) of the polymeric dispersing agent (B) to the silicate (A) is 0.5 to 10. Effect of the Invention

[0011] In other words, the present invention washes dishes fully automatically from the preliminary washing to the end of the main washing, or locally manually, without requiring a separate detergent supply device for the preliminary washing device.The preliminary washing device also has excellent cleaning power, particularly for protein stains, and even if the cleaning liquid from the main washing machine flows into the preliminary washing device and the detergent concentration becomes diluted, the interior of the preliminary washing device can be kept hygienic. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Next, the best mode for carrying out the present invention will be described in detail.

[0013] First, the automatic dishwashing machine system used in the present invention includes a preliminary washing device and a main washing device, and has a means for automatically or manually transferring dishes from the preliminary washing device to the main washing device. The preliminary washing device and the main washing device may be independent devices, or may be a single washing machine having multiple tanks and washing chambers, such as a multi-tank conveyor washing machine. In the case of a multi-tank conveyor washing machine, the first tank can be used as the preliminary washing device, and the second tank and subsequent tanks can be used as the main washing device. Since the dishes can be transferred in a conveyor manner, if the dishes are set on a rack or the like, the preliminary washing, main washing, and rinsing processes can be performed automatically, and washing can be completed without a person coming into contact with the washing liquid. The independent preliminary washing device may have a structure similar to that of a general automatic dishwashing machine, as in Patent Document 1, that is, it may be a device having an opening and closing door, a tank and a pump, and a means for washing dishes by a spray means. In this case, since the washing process is not an open system, a person does not come into contact with the washing liquid in the preliminary washing process. The transfer of dishes between the preliminary washing device and the main washing device is preferably automatic, but may also be performed manually, such as by an operator pushing a rack on which dishes are set. The preliminary washing device may also be an immersion tank. It is preferable that the preliminary washing device has a means for lifting up dishes and sending them to the main washing device so that people do not come into contact with the washing liquid in the immersion tank, or a means for setting dishes in a basket or rack, immersing the basket or rack in the immersion tank, and then transporting the rack or basket to the main washing machine.

[0014] Both the preliminary cleaning device and the main cleaning device preferably include a tank for storing cleaning liquid, and a mechanism for flowing the cleaning liquid from the main cleaning device into the tank of the preliminary cleaning device (hereinafter, referred to as a cleaning liquid reuse mechanism). When the preliminary cleaning device is independent, the cleaning liquid reuse mechanism may include a pump for the cleaning liquid reuse mechanism in the tank of the main cleaning device, and the cleaning liquid may be sent from the tank of the main cleaning device to the preliminary cleaning device by the pump. For example, there are cleaning devices shown in Figs. 1, 2, and 4 in JP 2004-298621 A and the cleaning device shown in Fig. 6 in JP 2012-511995 A mentioned above. In addition, a pipe may be branched from the cleaning line pipe of the main cleaning device and introduced into the tank of the preliminary cleaning device, and a part of the cleaning liquid may be sent from the cleaning line pipe to the tank of the preliminary cleaning device by water pressure when the main cleaning device is operating. For example, there is a cleaning device shown in Fig. 3 in JP 2004-298621 A. Furthermore, in cases where the preliminary washing device and the main washing device are integrated, such as in a multi-tank conveyor washer, a structure may be provided in which part of the washing liquid sprayed from the spray nozzles in the main washing device is collected and flows into the preliminary washing device. By providing such a washing liquid recycling mechanism, the main washing liquid that overflows and is discharged can be reused as part of the washing liquid in the preliminary washing device, which reduces contamination of the washing liquid in the preliminary washing device, and if the preliminary washing device has a heating means, continuous operation can prevent the temperature of the washing liquid in the preliminary washing device from dropping. In addition, there is no need for a separate device to supply cleaning agent for the preliminary washing device, which is economical.

[0015] When the cleaning liquid reuse mechanism is used, it is preferable that, as a result of the cleaning liquid of the main cleaning apparatus flowing from the main cleaning apparatus to the preliminary cleaning apparatus, the cleaning liquid in the preliminary cleaning apparatus contains a silicate as component (A) and a polymer dispersant as component (B), the content of the silicate of component (A) in the cleaning liquid is 0.001 mass % or more and less than 0.04 mass %, and the mass ratio (B / A) of the polymer dispersant (B) to the silicate (A) is 0.5 to 10.

[0016] The silicate (A) is composed of MO (MO is an alkali metal oxide) and SiO2. Preferred examples include sodium silicate and potassium silicate. The silicate is preferably present in the cleaning liquid in the preliminary cleaning device at 0.001% by mass or more and less than 0.04% by mass in terms of cleaning performance against dirt adhering to tableware and prevention of adhesion of dirt in the preliminary cleaning device. More preferably, the silicate is present at 0.002% by mass or more and less than 0.02% by mass. Even more preferably, the silicate is present at 0.003% by mass or more and 0.01% by mass. Although the silicate may be present at 0.04% by mass or more, no further improvement in performance is observed and it is economically disadvantageous. From the viewpoints of cleaning properties and inhibition of silica-derived scale, it is more preferable that the molar ratio of M2O to SiO2 constituting the silicate is M2O / SiO2=1 to 4. A molar ratio of 1 to 3 is even more preferable.

[0017] Examples of the (B) polymer dispersant include acrylic acid polymers and their salts, maleic acid polymers and their salts, acrylic acid-maleic acid copolymers and their salts, poly-α-hydroxyacrylic acid and its salts, acrylic acid-maleic acid-polyethylene glycol copolymers and their salts, olefin-maleic acid copolymers and their salts, acrylic acid-sulfonic acid copolymers and their salts, maleic acid-sulfonic acid copolymers and their salts, copolymers of acrylic acid and 2-hydroxy-3-allyloxypropanesulfonic acid and their salts, and copolymers of methyl vinyl ether and maleic acid and their salts. From the viewpoint of scale inhibition, it is preferable to use at least one selected from acrylic acid polymers and their salts, maleic acid polymers and their salts, acrylic acid-maleic acid copolymers and their salts, poly-α-hydroxyacrylic acid and its salts, acrylic acid-maleic acid-polyethylene glycol copolymers and their salts, olefin-maleic acid copolymers and their salts, and acrylic acid-sulfonic acid copolymers and their salts. From the viewpoint of preventing scale formation in the pre-cleaning device, the mass ratio (B / A) of the (B) polymer dispersant to the (A) silicate in the cleaning liquid of the pre-cleaning device is preferably 0.5 to 10. More preferably, it is 1 to 8, and even more preferably, it is 1.5 to 5. It may be 10 or more, but no further improvement in performance is observed and it is economically disadvantageous.

[0018] In order to bring the cleaning liquid of the preliminary cleaning device into the above-mentioned state, it is preferable that in the cleaning step in this cleaning device, the cleaning liquid contains a silicate as component (A), a polymeric dispersing agent as component (B), and further contains a chelating agent as component (C), the content of the silicate as component (A) in the cleaning liquid is 0.005% by mass or more and less than 0.1% by mass, the content of the chelating agent as component (C) in the cleaning liquid is 0.01% by mass or more and less than 0.1% by mass, and the mass ratio (B / A) of the polymeric dispersing agent (B) to the silicate (A) is 0.5 to 10. If the tank in the preliminary washing device does not contain any detergent at the start of operation, when the washing liquid flows from the main washing device into the tank in the preliminary washing device, the washing liquid is diluted about 100 to 20 times, depending on the amount of washing liquid that flows in. As the number of washes is increased to wash a large amount of dishes and the amount of washing liquid that flows from the main washing device into the preliminary washing device increases, the concentration of detergent in the tank of the preliminary washing device increases, and theoretically reaches a concentration that is very close to the concentration of detergent in the main washing device.

[0019] In the cleaning solution in the present cleaning device, the content of silicate (A) in the cleaning solution is preferably 0.005% by mass or more and less than 0.1% by mass, which is preferable in terms of cleaning performance in the present cleaning device, and when the cleaning solution in the present cleaning device flows into the tank of the preliminary cleaning device and is diluted there, the alkaline buffer action can suppress a decrease in the pH of the cleaning solution in the preliminary cleaning device, which is advantageous in terms of preventing adhesion of dirt in the preliminary cleaning device. The content is preferably 0.01% by mass or more and 0.08% by mass. Although it may be 0.1% by mass or more, it is disadvantageous in that it becomes difficult to rinse. In addition, when the cleaning solution in the present cleaning device flows into the tank of the preliminary cleaning device, the mass ratio (B / A) of the polymer dispersant (B) to the silicate (A) in the cleaning solution in the present cleaning device is preferably 0.5 to 10, since this will result in a similar ratio of (B / A) in the cleaning solution in the preliminary cleaning device. It is more preferably 1 to 8, and even more preferably 1.5 to 5. It may exceed 10, but no further improvement in effect can be expected, and this is economically disadvantageous.

[0020] The cleaning solution in the cleaning device preferably further contains a chelating agent as component (C). Examples of the chelating agent include sodium aminotrimethylene phosphonate, potassium aminotrimethylene phosphonate, sodium 1-hydroxyethylidene-1,1-diphosphonate, potassium 1-hydroxyethylidene-1,1-diphosphonate, sodium 2-phosphonobutane-1,2,4-tricarboxylate, potassium 2-phosphonobutane-1,2,4-tricarboxylate, sodium ethylenediaminetetramethylene phosphonate, potassium ethylenediaminetetramethylene phosphonate, sodium diethylenetriaminepentamethylene phosphonate, potassium diethylenetriaminepentamethylene phosphonate, trisodium nitrilotriacetate, tripotassium nitrilotriacetate, disodium hydroxyethyliminodiacetate, and the like. Examples of the tartrate include thorium, dipotassium hydroxyethyliminodiacetate, trisodium methylglycine diacetate, tripotassium methylglycine diacetate, tetrasodium ethylenediaminetetraacetate, tetrapotassium ethylenediaminetetraacetate, trisodium hydroxyethylethylenediaminetriacetate, tripotassium hydroxyethylethylenediaminetriacetate, tetrasodium L-glutamate-N,N-2acetate, tetrapotassium L-glutamate-N,N-2acetate, tetrasodium L-aspartate-N,N-2acetate, tetrapotassium L-aspartate-N,N-2acetate, pentasodium diethylenetriaminepentaacetate, pentasodium diethylenetriaminepentaacetate, disodium tartrate, dipotassium tartrate, and potassium sodium tartrate. Among these, trisodium nitrilotriacetate, tripotassium nitrilotriacetate, trisodium methylglycine diacetate, tripotassium methylglycine diacetate, tetrasodium ethylenediaminetetraacetate, tetrapotassium ethylenediaminetetraacetate, tetrasodium L-glutamic acid-N,N-diacetate, and tetrapotassium L-glutamic acid-N,N-diacetate are preferred from the standpoints of economy and cleaning properties.

[0021] The content of the chelating agent (C) in the cleaning solution in the cleaning device is preferably 0.01% by mass or more and less than 0.1% by mass in terms of cleaning performance in the cleaning device. More preferably, it is 0.015% by mass or more and 0.08% by mass. Although it may be 0.1% by mass or more, it is disadvantageous in that it becomes difficult to rinse.

[0022] The cleaning solution in the cleaning device may contain optional components such as surfactants, enzymes, bleaches, pH adjusters, organic acids and their salts, dyes, fragrances, metal corrosion inhibitors, disinfectants, antibacterial agents, deodorizers, antistatic agents, and antioxidants.

[0023] The washing method of the present invention does not require a separate supply device for the preliminary washing device, and even if the washing liquid from the main washing machine flows into the preliminary washing device and the detergent concentration becomes diluted, the pH of the washing liquid is prevented from decreasing, and the washing method has good cleaning properties and is excellent in suppressing scale in the preliminary washing process, making it ideal for a washing system that washes dishes fully automatically from the preliminary washing to the end of the main washing. EXAMPLES

[0024] Next, examples will be described together with comparative examples, but the present invention is not limited to these.

[0025] First, in order to prepare the composition, the components were prepared as follows. Details of each component are as follows, and the values ​​in Tables 1 to 6 indicate the pure content of each component. Unless otherwise specified, "%" refers to mass basis. Furthermore, tap water was used as water unless otherwise specified.

[0026] (A) Silicate The following molar ratios indicate M2O / SiO2 (M2O is an alkali metal oxide). Silicate 1: Sodium metasilicate (molar ratio: 1, purity: 42%) (Product name: Metakeisan Soda 9-Suien, manufactured by ADEKA Corporation) Silicate 2: Sodium orthosilicate (molar ratio: 2, purity: 65%) (Product name: Neo Ortho 65, manufactured by Koei Chemical Co., Ltd.) Silicate 3: Potassium orthosilicate (molar ratio: 2, purity: 35%) (Product name "OK-35", manufactured by Nippon Kagaku Co., Ltd.)

[0027] (B) Polymer dispersant Polymer dispersant 1: Sodium polyacrylate (Purity 45%, average molecular weight 5,500) (Product name: AQUALIC YS-100, manufactured by Nippon Shokubai Co., Ltd.) Polymer dispersant 2: Sodium salt of acrylic acid-maleic acid copolymer (Purity 35%, average molecular weight 40,000) (Product name: Acusol 505N, manufactured by ROHM & HAAS) Polymer dispersant 3: Sodium polyhydroxyacrylate (40% pure) (Product name: Pale Black 250, manufactured by Hodogaya Chemical Co., Ltd.) Polymer dispersant 4: Sodium salt of olefin-maleic acid copolymer (92% purity, average molecular weight 15,000) (Product name: “Acusol 460ND”, (Manufactured by ROHM & HAAS)

[0028] (C) Chelating agent Chelating agent 1: Trisodium nitrilotriacetate (92% pure) (Product name: Clewat PC-C3, manufactured by Nagase ChemteX Corporation) Chelating agent 2: Tetrasodium ethylenediaminetetraacetate (87% pure) (Product name: Dissolvin NA, manufactured by Nouryon) Chelating agent 3: Tetrasodium L-glutamic acid diacetate (47% pure) (Product name: Dissolvin GL-47-S, manufactured by Nouryon) Chelating agent 4: Trisodium methylglycine diacetate (40% pure) (Product name: Trilon M Liquid, manufactured by BASF)

[0029] [Examples 1 to 15, Comparative Examples 1 to 3] Performance evaluation in the preliminary cleaning device A cleaning solution (assuming a cleaning solution for use in a preliminary cleaning device) having the composition shown in Tables 1 to 4 below (the units of values ​​in each table are "mass %) was prepared, and the cleaning properties and the ability to inhibit scale formation were evaluated. The test method and evaluation criteria are as follows.

[0030] [Washability] Testing Method Appropriate amounts of each component were put into a commercial automatic dishwasher (DW-RD61, Sanyo Electric Co., Ltd.), and the compositions were adjusted in the dishwasher to the compositions shown in Tables 1 to 4, and the dishwasher was operated under the following operating conditions. The following ceramic dishes to be washed were washed in groups of 10, and the degree of dirt removal on each dish after washing was visually observed. The washing performance was evaluated according to the evaluation criteria described below. Beef tallow and egg yolk were prepared as stains, and cleaning tests were performed on each type of stain. In this test, the automatic dishwasher was treated as an independent pre-washing device.

[0031] Operating conditions Washing temperature: 40℃ Cleaning tank capacity: 50 liters Cleaning time: 20 seconds Rinse: None Beef tallow stains: Refined beef tallow was used. Egg yolk stains: Only the egg yolk was used and mixed well. Object to be cleaned: 2 g of the above soil was attached to each ceramic dish with a diameter of 10 cm, and the dish was dried at room temperature for 1 hour.

[0032] Evaluation criteria ◎: Removes more than 90% of dirt. ○: 60% or more but less than 90% of dirt removed. △: 40% to less than 60% of dirt removed. ×: Less than 40% of dirt removed.

[0033] [Scale formation suppression performance] Testing Method Using artificial hard water (total hardness: 250 mg / L as CaCO3), cleaning solutions with the compositions shown in Tables 1 to 4 were prepared, 50 ml of which was poured into a 100 ml color comparison tube and kept at 40°C for 24 hours. The amount of scale formation was then visually observed and evaluated according to the following criteria.

[0034] Evaluation criteria : Almost no scale formation. ○: Some scale formation was observed. ×: Significant scale buildup was observed.

[0035] [Table 1]

[0036] [Table 2]

[0037] [Table 3]

[0038] [Table 4]

[0039] From the evaluation results in Tables 1 to 4, it can be seen that almost good results were obtained in both the cleaning performance and the scale formation inhibition ability in Examples 1 to 15. In contrast, it can be seen that there are practical problems in at least some of the items in Comparative Examples 1 to 3.

[0040] [Examples 16 to 20, Comparative Examples 4 to 6] Cleaning tests assuming a fully automatic cleaning system Using the washing device shown in FIG. 3 of JP 2004-298621 A, tableware (objects to be washed as described below) were actually washed in the following order under the following conditions: preliminary washing, main washing, and rinsing. Note that the preliminary washing was started with hot water stored in the washing tank, and no detergent was used. In the first washing cycle, the washing liquid flows from the washing tank of the main washing device (in this case, an automatic dishwasher) into the preliminary washing device (in this case, an immersion tank), and the washing liquid is poured into the immersion tank. From the second washing cycle, a washing test was performed using tableware with stains. In the preliminary washing process, the tableware was only immersed, without scrubbing, and the tableware was moved to the main washing device by a person instead of an automatic conveying device. The washing cycle of preliminary washing, main washing, and rinsing was performed 50 times per sample (excluding the first time). The cleaning performance and the state of the immersion tank after 50 times were evaluated. A cleaning solution (assuming the cleaning solution in this washing machine) having the composition shown in Tables 5 and 6 below (the units of values ​​in each table are "mass %) was prepared and used for the test.

[0041] 〔conditions〕 (1) Cleaning target A soft-boiled egg heated in 65°C water for 30 minutes was used as stain 1, and 40g of rice, 20g of retort food (beef bowl filling, manufactured by Yoshinoya) and 5g of beef fat were thoroughly mixed to use as stain 2. 2g of each of stains 1 and 2 was then taken and evenly applied to the inside of a porcelain bowl (diameter 18cm x height 6cm) and left for 60 minutes. Ten such bowls were used in a set.

[0042] (2) Pre-cleaning Immersion tank: sink (600mm x 450mm x 300mm) Amount of pre-cleaning solution: 50 liters (adjust the drain outlet to keep the amount of solution constant) Immersion temperature: 40℃ (temperature when hot water is poured, no further heating) Immersion time: 5 minutes

[0043] (3) Main cleaning Automatic dishwasher: DW-RD61, Sanyo Electric Washing temperature: 60℃ Cleaning time: 50 seconds Cleaning tank capacity: 50 liters (4) Rinse Rinse water volume: 4 liters per rinse Rinse water temperature: 80℃ Rinse time: 10 seconds

[0044] (5) Flow rate of cleaning fluid from the main washer to the pre-cleaning device Flow rate: 2L per washing process of this washing machine

[0045] Cleaning evaluation criteria ◎: More than 90% of dirt removed in all 50 cleaning cycles. ○: More than 90% of dirt was removed in 40 to 49 out of 50 cleaning cycles. And after 1 to 10 washing cycles, more than 80% of dirt is removed. ×: Less than 80% of dirt was removed in one or more of 50 cleaning cycles.

[0046] Evaluation criteria for the condition after draining the liquid from the immersion tank and removing solid dirt after 50 times ○: There is some oil stain on the wall △: There is some dirt on the wall ×: Wall is noticeably dirty

[0047] [Table 5]

[0048] [Table 6]

[0049] From the evaluation results in Tables 5 and 6, it can be seen that Examples 16 to 20 obtained almost good results in terms of both cleaning ability and the condition of the immersion tank after 50 times. In contrast, Comparative Examples 4 to 6 have practical problems in at least some of the items.

[0050] From the results of the above examples and comparative examples, it was determined that the washing method of the present invention can optimally wash dishes in a system that washes dishes fully automatically from the preliminary washing process to the end of the main washing process, and that even if the washing liquid from the main washing machine flows into the preliminary washing device and is diluted in the preliminary washing device, the method has excellent cleaning properties and scale inhibition ability, so that the inside of the preliminary washing device can be kept hygienic.

Claims

1. A washing method for an automatic dishwashing system including a pre-washing device and a main washing device, each having a tank for storing washing liquid, and a mechanism for allowing washing liquid to flow from the main washing device to the tank of the pre-washing device without requiring a separate detergent supply device for the pre-washing device, comprising: When the operation of the automatic dishwashing machine system is started and the amount of washing liquid flowing from the main washing device to the preliminary washing device is within a range of 1 / 20 to 1 / 100 volume % of the washing liquid stored in the preliminary washing device, The cleaning liquid stored in the preliminary cleaning device contains a silicate as a component (A) and a polymer dispersant as a component (B), and the silicate (A) is M 2 O (M 2 O is an alkali metal oxide) and SiO 2 and 2 O and SiO 2 Molar ratio (M 2 O / SiO 2 ) is 1 to 4, the content of the silicate of the component (A) in the cleaning liquid is 0.001 mass% or more and less than 0.04 mass%, the (B) polymer dispersant is one or more selected from the group consisting of acrylic acid polymers and salts thereof, maleic acid polymers and salts thereof, acrylic acid-maleic acid copolymers and salts thereof, poly-α-hydroxyacrylic acid and salts thereof, acrylic acid-maleic acid-polyethylene glycol copolymers and salts thereof, olefin-maleic acid copolymers and salts thereof, and acrylic acid-sulfonic acid copolymers and salts thereof, and the mass ratio (B / A) of the (B) polymer dispersant to the (A) silicate is 0.5 to 10, The cleaning solution stored in the cleaning device contains a silicate as a component (A), a polymer dispersant as a component (B), and a chelating agent as a component (C), the (B) polymer dispersant is one or more selected from an acrylic acid polymer and its salt, a maleic acid polymer and its salt, an acrylic acid-maleic acid copolymer and its salt, a poly-α-hydroxyacrylic acid and its salt, an acrylic acid-maleic acid-polyethylene glycol copolymer and its salt, an olefin-maleic acid copolymer and its salt, and an acrylic acid-sulfonic acid copolymer and its salt, the content of the silicate of the (A) component is 0.01% by mass or more and less than 0.1% by mass, the content of the chelating agent of the (C) component is 0.015% by mass or more and less than 0.08% by mass, the mass ratio (B / A) of the (B) polymer dispersant to the (A) silicate is 0.5 to 10, A cleaning method characterized in that when the cleaning liquid flows from the main cleaning device into a tank in a preliminary cleaning device, the cleaning liquid is diluted 100 to 20 times.

2. 2. The cleaning method according to claim 1, wherein a mass ratio (B / A) of the polymer dispersant (B) to the silicate (A) is 1.5 to 5.

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