CA2502423C - Acidic cleaning method for machine dishwashing - Google Patents
Acidic cleaning method for machine dishwashing Download PDFInfo
- Publication number
- CA2502423C CA2502423C CA2502423A CA2502423A CA2502423C CA 2502423 C CA2502423 C CA 2502423C CA 2502423 A CA2502423 A CA 2502423A CA 2502423 A CA2502423 A CA 2502423A CA 2502423 C CA2502423 C CA 2502423C
- Authority
- CA
- Canada
- Prior art keywords
- acid
- cleaning solution
- tableware
- aqueous cleaning
- acidic aqueous
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 238000004140 cleaning Methods 0.000 title claims abstract description 97
- 238000000034 method Methods 0.000 title claims abstract description 60
- 230000002378 acidificating effect Effects 0.000 title claims abstract description 47
- 238000004851 dishwashing Methods 0.000 title claims abstract description 17
- 239000002689 soil Substances 0.000 claims abstract description 10
- 230000003472 neutralizing effect Effects 0.000 claims abstract description 3
- 239000002253 acid Substances 0.000 claims description 28
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 23
- 239000002351 wastewater Substances 0.000 claims description 16
- 239000000203 mixture Substances 0.000 claims description 13
- 239000000126 substance Substances 0.000 claims description 13
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims description 12
- RGHNJXZEOKUKBD-SQOUGZDYSA-N D-gluconic acid Chemical compound OC[C@@H](O)[C@@H](O)[C@H](O)[C@@H](O)C(O)=O RGHNJXZEOKUKBD-SQOUGZDYSA-N 0.000 claims description 10
- AEMRFAOFKBGASW-UHFFFAOYSA-N Glycolic acid Chemical compound OCC(O)=O AEMRFAOFKBGASW-UHFFFAOYSA-N 0.000 claims description 10
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 10
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 claims description 10
- 238000005507 spraying Methods 0.000 claims description 9
- AFVFQIVMOAPDHO-UHFFFAOYSA-N Methanesulfonic acid Chemical compound CS(O)(=O)=O AFVFQIVMOAPDHO-UHFFFAOYSA-N 0.000 claims description 8
- 150000007513 acids Chemical class 0.000 claims description 7
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 6
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 6
- 235000011007 phosphoric acid Nutrition 0.000 claims description 6
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 claims description 5
- RGHNJXZEOKUKBD-UHFFFAOYSA-N D-gluconic acid Natural products OCC(O)C(O)C(O)C(O)C(O)=O RGHNJXZEOKUKBD-UHFFFAOYSA-N 0.000 claims description 5
- 239000004063 acid-resistant material Substances 0.000 claims description 5
- 239000003513 alkali Substances 0.000 claims description 5
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 5
- 235000019253 formic acid Nutrition 0.000 claims description 5
- 239000000174 gluconic acid Substances 0.000 claims description 5
- 235000012208 gluconic acid Nutrition 0.000 claims description 5
- IIACRCGMVDHOTQ-UHFFFAOYSA-N sulfamic acid Chemical compound NS(O)(=O)=O IIACRCGMVDHOTQ-UHFFFAOYSA-N 0.000 claims description 5
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 4
- WNLRTRBMVRJNCN-UHFFFAOYSA-N adipic acid Chemical compound OC(=O)CCCCC(O)=O WNLRTRBMVRJNCN-UHFFFAOYSA-N 0.000 claims description 4
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 claims description 4
- 229940098779 methanesulfonic acid Drugs 0.000 claims description 4
- 239000007921 spray Substances 0.000 claims description 4
- 238000005406 washing Methods 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 claims description 3
- 239000007788 liquid Substances 0.000 claims description 3
- 150000007524 organic acids Chemical class 0.000 claims description 3
- 235000005985 organic acids Nutrition 0.000 claims description 3
- 150000003009 phosphonic acids Chemical class 0.000 claims description 3
- RTBFRGCFXZNCOE-UHFFFAOYSA-N 1-methylsulfonylpiperidin-4-one Chemical compound CS(=O)(=O)N1CCC(=O)CC1 RTBFRGCFXZNCOE-UHFFFAOYSA-N 0.000 claims description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 2
- 229920002125 Sokalan® Polymers 0.000 claims description 2
- KDYFGRWQOYBRFD-UHFFFAOYSA-N Succinic acid Natural products OC(=O)CCC(O)=O KDYFGRWQOYBRFD-UHFFFAOYSA-N 0.000 claims description 2
- 235000011054 acetic acid Nutrition 0.000 claims description 2
- 239000001361 adipic acid Substances 0.000 claims description 2
- 235000011037 adipic acid Nutrition 0.000 claims description 2
- 150000001335 aliphatic alkanes Chemical class 0.000 claims description 2
- JFCQEDHGNNZCLN-UHFFFAOYSA-N anhydrous glutaric acid Natural products OC(=O)CCCC(O)=O JFCQEDHGNNZCLN-UHFFFAOYSA-N 0.000 claims description 2
- KDYFGRWQOYBRFD-NUQCWPJISA-N butanedioic acid Chemical compound O[14C](=O)CC[14C](O)=O KDYFGRWQOYBRFD-NUQCWPJISA-N 0.000 claims description 2
- XBDQKXXYIPTUBI-UHFFFAOYSA-N dimethylselenoniopropionate Natural products CCC(O)=O XBDQKXXYIPTUBI-UHFFFAOYSA-N 0.000 claims description 2
- 239000006260 foam Substances 0.000 claims description 2
- 229910052500 inorganic mineral Inorganic materials 0.000 claims description 2
- 239000004310 lactic acid Substances 0.000 claims description 2
- 235000014655 lactic acid Nutrition 0.000 claims description 2
- 239000011707 mineral Substances 0.000 claims description 2
- 150000007522 mineralic acids Chemical class 0.000 claims description 2
- DUWWHGPELOTTOE-UHFFFAOYSA-N n-(5-chloro-2,4-dimethoxyphenyl)-3-oxobutanamide Chemical compound COC1=CC(OC)=C(NC(=O)CC(C)=O)C=C1Cl DUWWHGPELOTTOE-UHFFFAOYSA-N 0.000 claims description 2
- 229910017604 nitric acid Inorganic materials 0.000 claims description 2
- 235000019260 propionic acid Nutrition 0.000 claims description 2
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims 3
- WPYMKLBDIGXBTP-UHFFFAOYSA-N benzoic acid Chemical compound OC(=O)C1=CC=CC=C1 WPYMKLBDIGXBTP-UHFFFAOYSA-N 0.000 claims 2
- 239000005711 Benzoic acid Substances 0.000 claims 1
- LSNNMFCWUKXFEE-UHFFFAOYSA-M Bisulfite Chemical compound OS([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-M 0.000 claims 1
- OFOBLEOULBTSOW-UHFFFAOYSA-N Propanedioic acid Natural products OC(=O)CC(O)=O OFOBLEOULBTSOW-UHFFFAOYSA-N 0.000 claims 1
- 235000010233 benzoic acid Nutrition 0.000 claims 1
- VZCYOOQTPOCHFL-UPHRSURJSA-N maleic acid Chemical compound OC(=O)\C=C/C(O)=O VZCYOOQTPOCHFL-UPHRSURJSA-N 0.000 claims 1
- 239000011976 maleic acid Substances 0.000 claims 1
- 235000006408 oxalic acid Nutrition 0.000 claims 1
- VZCYOOQTPOCHFL-UHFFFAOYSA-N trans-butenedioic acid Natural products OC(=O)C=CC(O)=O VZCYOOQTPOCHFL-UHFFFAOYSA-N 0.000 claims 1
- 239000000243 solution Substances 0.000 abstract description 45
- 239000007864 aqueous solution Substances 0.000 abstract description 2
- 238000012360 testing method Methods 0.000 description 19
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 17
- 239000000654 additive Substances 0.000 description 7
- 239000003599 detergent Substances 0.000 description 6
- 229920002472 Starch Polymers 0.000 description 3
- 239000003929 acidic solution Substances 0.000 description 3
- 230000000996 additive effect Effects 0.000 description 3
- 238000009472 formulation Methods 0.000 description 3
- 239000013505 freshwater Substances 0.000 description 3
- WQYVRQLZKVEZGA-UHFFFAOYSA-N hypochlorite Chemical compound Cl[O-] WQYVRQLZKVEZGA-UHFFFAOYSA-N 0.000 description 3
- 238000006386 neutralization reaction Methods 0.000 description 3
- 235000019698 starch Nutrition 0.000 description 3
- 239000008107 starch Substances 0.000 description 3
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 2
- 235000003166 Opuntia robusta Nutrition 0.000 description 2
- 244000218514 Opuntia robusta Species 0.000 description 2
- 150000008044 alkali metal hydroxides Chemical class 0.000 description 2
- 229910052910 alkali metal silicate Inorganic materials 0.000 description 2
- 239000012670 alkaline solution Substances 0.000 description 2
- 239000000969 carrier Substances 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 235000013305 food Nutrition 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 239000010409 thin film Substances 0.000 description 2
- CYXGBTZYTXLVDN-UHFFFAOYSA-N 1-octoxyphosphonoyloxyoctane Chemical compound CCCCCCCCOP(=O)OCCCCCCCC CYXGBTZYTXLVDN-UHFFFAOYSA-N 0.000 description 1
- HZAXFHJVJLSVMW-UHFFFAOYSA-N 2-Aminoethan-1-ol Chemical compound NCCO HZAXFHJVJLSVMW-UHFFFAOYSA-N 0.000 description 1
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 1
- 229920002261 Corn starch Polymers 0.000 description 1
- 241000196324 Embryophyta Species 0.000 description 1
- 244000269722 Thea sinensis Species 0.000 description 1
- 235000011941 Tilia x europaea Nutrition 0.000 description 1
- GSEJCLTVZPLZKY-UHFFFAOYSA-N Triethanolamine Chemical compound OCCN(CCO)CCO GSEJCLTVZPLZKY-UHFFFAOYSA-N 0.000 description 1
- 239000013543 active substance Substances 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 229910000288 alkali metal carbonate Inorganic materials 0.000 description 1
- 150000008041 alkali metal carbonates Chemical class 0.000 description 1
- -1 alkali metal hypochlorite Chemical class 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 239000003637 basic solution Substances 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 239000012459 cleaning agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 239000008139 complexing agent Substances 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 239000008120 corn starch Substances 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- ZBCBWPMODOFKDW-UHFFFAOYSA-N diethanolamine Chemical compound OCCNCCO ZBCBWPMODOFKDW-UHFFFAOYSA-N 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000000975 dye Substances 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 150000002169 ethanolamines Chemical class 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 239000004519 grease Substances 0.000 description 1
- 150000004679 hydroxides Chemical class 0.000 description 1
- 239000003112 inhibitor Substances 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 239000004571 lime Substances 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 150000003016 phosphoric acids Chemical class 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 102000004169 proteins and genes Human genes 0.000 description 1
- 108090000623 proteins and genes Proteins 0.000 description 1
- 239000000700 radioactive tracer Substances 0.000 description 1
- 230000001953 sensory effect Effects 0.000 description 1
- 239000003352 sequestering agent Substances 0.000 description 1
- 235000019832 sodium triphosphate Nutrition 0.000 description 1
- 238000010561 standard procedure Methods 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- UNXRWKVEANCORM-UHFFFAOYSA-I triphosphate(5-) Chemical compound [O-]P([O-])(=O)OP([O-])(=O)OP([O-])([O-])=O UNXRWKVEANCORM-UHFFFAOYSA-I 0.000 description 1
- 238000004065 wastewater treatment Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
- C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
- C11D7/00—Compositions of detergents based essentially on non-surface-active compounds
- C11D7/02—Inorganic compounds
- C11D7/04—Water-soluble compounds
- C11D7/06—Hydroxides
-
- C—CHEMISTRY; METALLURGY
- C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
- C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
- C11D7/00—Compositions of detergents based essentially on non-surface-active compounds
- C11D7/02—Inorganic compounds
- C11D7/04—Water-soluble compounds
- C11D7/08—Acids
-
- C—CHEMISTRY; METALLURGY
- C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
- C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
- C11D7/00—Compositions of detergents based essentially on non-surface-active compounds
- C11D7/22—Organic compounds
- C11D7/26—Organic compounds containing oxygen
- C11D7/265—Carboxylic acids or salts thereof
-
- C—CHEMISTRY; METALLURGY
- C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
- C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
- C11D7/00—Compositions of detergents based essentially on non-surface-active compounds
- C11D7/22—Organic compounds
- C11D7/34—Organic compounds containing sulfur
-
- C—CHEMISTRY; METALLURGY
- C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
- C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
- C11D2111/00—Cleaning compositions characterised by the objects to be cleaned; Cleaning compositions characterised by non-standard cleaning or washing processes
- C11D2111/10—Objects to be cleaned
- C11D2111/14—Hard surfaces
-
- C—CHEMISTRY; METALLURGY
- C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
- C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
- C11D2111/00—Cleaning compositions characterised by the objects to be cleaned; Cleaning compositions characterised by non-standard cleaning or washing processes
- C11D2111/40—Specific cleaning or washing processes
- C11D2111/44—Multi-step processes
Landscapes
- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Wood Science & Technology (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Emergency Medicine (AREA)
- Detergent Compositions (AREA)
- Cleaning By Liquid Or Steam (AREA)
Abstract
The process of continuous machine dishwashing, which can be carried out in single-tank or multi-tank machines, is improved by the machine-operated process disclosed. This is achieved, in particular, by treatment of the tableware at least in one process step with an acidic cleaning solution and in another process step with an alkaline cleaning solution, comprising the steps of: a) applying an acidic aqueous cleaning solution to the at least partly soiled tableware and b) removing the acidic aqueous solution and the soil in one or more following steps, the at least one alkaline treatment taking place before and/or after the acidic treatment and the alkaline and at least acidic aqueous cleaning solution at least partially neutralizing one another.
Description
Patent Application ACIDIC CLEANING METHOD FOR MACHINE DISHWASHING
This invention relates to a machine dishwashing process for cleaning tableware or other surfaces soiled with food remains. More particularly, the object of the invention is to improve the continuous or discontinuous process of machine dishwashing which may be carried out both in single-tank and in multi-tank machines.
In conventional dishwashing processes, food-soiled tableware, including, for example, trays, cutlery and glasses smeared with lipstick residues, is sprayed or squirted with water in a prewash zone or prewash cycle, i.e. before the actual washing process. This water is cold or preheated fresh water, cooling water from a vapor condensation process, but generally overflow water of a wash liquor which is generally sprayed under low pressure through relatively large spray arm openings on to the tableware. After this prewash zone or prewash cycle, the tableware enters the actual wash zone or wash cycle where it is sprayed with wash liquor.
The wash liquor usually consists of water with a temperature of about 50°C to 65°C to which a cleaner is added. In order to remove grease, starch, dyes and protein with sufficient reliability, detergents in powder or liquid form, for example, are added to the water, so that about 0.1 to 0.3% by weight of active washing substances are present in the _ cleaning solution. The resulting wash liquor is usually sprayed on to the articles to be cleaned through differently arranged nozzles. The soil on the tableware is thus removed or at least swollen or softened and partially dissolved. In a following clear-wash zone or clear-wash cycle,
This invention relates to a machine dishwashing process for cleaning tableware or other surfaces soiled with food remains. More particularly, the object of the invention is to improve the continuous or discontinuous process of machine dishwashing which may be carried out both in single-tank and in multi-tank machines.
In conventional dishwashing processes, food-soiled tableware, including, for example, trays, cutlery and glasses smeared with lipstick residues, is sprayed or squirted with water in a prewash zone or prewash cycle, i.e. before the actual washing process. This water is cold or preheated fresh water, cooling water from a vapor condensation process, but generally overflow water of a wash liquor which is generally sprayed under low pressure through relatively large spray arm openings on to the tableware. After this prewash zone or prewash cycle, the tableware enters the actual wash zone or wash cycle where it is sprayed with wash liquor.
The wash liquor usually consists of water with a temperature of about 50°C to 65°C to which a cleaner is added. In order to remove grease, starch, dyes and protein with sufficient reliability, detergents in powder or liquid form, for example, are added to the water, so that about 0.1 to 0.3% by weight of active washing substances are present in the _ cleaning solution. The resulting wash liquor is usually sprayed on to the articles to be cleaned through differently arranged nozzles. The soil on the tableware is thus removed or at least swollen or softened and partially dissolved. In a following clear-wash zone or clear-wash cycle,
2 the soaked or softened soil and food remains are removed with water.
At the same time, the wash liquor is rinsed off. In the following rinse cycle, the rinse water usually consists of fresh water and a rinse agent, which generally ensures that only a very thin film of water is left on the tableware and can drain off or evaporate in following drying zones.
The requirements which institutional and domestic dishwashing machine are expected to satisfy are different. Depending on the particular type and the application involved, institutional dishwashing machines usually comprise several tanks arranged in succession, from which rinse and wash liquor is sprayed onto the tableware to be cleaned as it passes through the machine. The tanks are generally arranged on the cascade principle, the rinse and wash liquor passing successively through the tanks from the outlet end to the inlet end of the tableware.
Fresh water is generally fed into the machines at the outlet end. The required amount of detergent is dosed into at least one wash tank also known as the dosing tank. The dosing of detergent normally takes place automatically depending on the conductivity or the pH of the wash liquor or optionally by means of a dosing pump controlled by a timer or clock.
Several components may also be separately dosed. For example a basic lye solution based on an aqueous alkali metal hydroxide solution may be introduced first. If required, one or more additives may be added to this basic solution. Normally, the dosage of these additives is either proportional to the addition of the basic lye or is controlled by a timer. If desired, the additives may be dosed according to the advance cycle of the chain carrying the tableware to be washed through the machine. In addition, additives can also be dosed or the additive concentration increased by determining the amount of additive in the basic lye by sensory detection of a tracer present in the additive.
As explained in EP 282 214, a problem which often occurred in the past was that, in regular conventional cleaning, periodic thorough
At the same time, the wash liquor is rinsed off. In the following rinse cycle, the rinse water usually consists of fresh water and a rinse agent, which generally ensures that only a very thin film of water is left on the tableware and can drain off or evaporate in following drying zones.
The requirements which institutional and domestic dishwashing machine are expected to satisfy are different. Depending on the particular type and the application involved, institutional dishwashing machines usually comprise several tanks arranged in succession, from which rinse and wash liquor is sprayed onto the tableware to be cleaned as it passes through the machine. The tanks are generally arranged on the cascade principle, the rinse and wash liquor passing successively through the tanks from the outlet end to the inlet end of the tableware.
Fresh water is generally fed into the machines at the outlet end. The required amount of detergent is dosed into at least one wash tank also known as the dosing tank. The dosing of detergent normally takes place automatically depending on the conductivity or the pH of the wash liquor or optionally by means of a dosing pump controlled by a timer or clock.
Several components may also be separately dosed. For example a basic lye solution based on an aqueous alkali metal hydroxide solution may be introduced first. If required, one or more additives may be added to this basic solution. Normally, the dosage of these additives is either proportional to the addition of the basic lye or is controlled by a timer. If desired, the additives may be dosed according to the advance cycle of the chain carrying the tableware to be washed through the machine. In addition, additives can also be dosed or the additive concentration increased by determining the amount of additive in the basic lye by sensory detection of a tracer present in the additive.
As explained in EP 282 214, a problem which often occurred in the past was that, in regular conventional cleaning, periodic thorough
3 cleaning steps could not be completely dispensed with, even when relatively large amounts of detergents were used. The purpose of this thorough cleaning is to remove coatings of, in particular, water-insoluble starch which have built up over time, but which are not immediately visible to the eye. During this thorough cleaning, the articles, preferably the tableware, are occasionally treated with wash liquor containing several times the usual concentration of active substances. This causes considerable pollution of the wastewater. As already stated, EP 282 214 tackled this problem. An attempt was made by improving cleaning performance to reduce labor, the consumption of water and chemicals and hence environmental pollution and, at the same time, to achieve satisfactory cleaning. EP 282 214 attempts to solve the problem by spraying a highly concentrated cleaning formulation onto the soiled articles, followed by a contact phase, after which the cleaning solution and soil are removed in one or more following steps.
As explained, EP 282 214 mentions reducing pollution of the wastewater as an essential aim of the invention. However, on closer examination of the process as a whole, it becomes clear that an essential aspect of the pollution of wastewater was not taken into account. In the treatment of wastewater, it is usually imperative for the wastewater to have a certain pH before or during treatment in corresponding treatment plants. This pH is generally close to the neutral point of water according to the nature of the treatment. Depending on legislation, there are even country-specific wastewater regulations which stipulate a particular pH for wastewater. All this means is that more chemicals have to added to neutralize strongly acidic or strongly alkaline wastewater before further treatment. In other words, whilst the chemicals saved in the cleaning process according to EP 282 214 no longer pollute the wastewater, more chemicals still have to be used at a later stage to neutralize the wastewater flowing off before the water
As explained, EP 282 214 mentions reducing pollution of the wastewater as an essential aim of the invention. However, on closer examination of the process as a whole, it becomes clear that an essential aspect of the pollution of wastewater was not taken into account. In the treatment of wastewater, it is usually imperative for the wastewater to have a certain pH before or during treatment in corresponding treatment plants. This pH is generally close to the neutral point of water according to the nature of the treatment. Depending on legislation, there are even country-specific wastewater regulations which stipulate a particular pH for wastewater. All this means is that more chemicals have to added to neutralize strongly acidic or strongly alkaline wastewater before further treatment. In other words, whilst the chemicals saved in the cleaning process according to EP 282 214 no longer pollute the wastewater, more chemicals still have to be used at a later stage to neutralize the wastewater flowing off before the water
4 PCT/EP2003/012366 treatment. EP 282 214 takes no account at all of this problem. On the contrary, throughout the disclosure of EP 282 214 only alkaline detergents are mentioned and recommended. In column 3, line 15 onwards, the cleaning agents to be used are explicitly discussed. In particular, from column 3, line 24, it is disclosed that, for example, alternately spraying with high alkalinity and then with lower alkalinity could have advantages. It is then explained that a further advantage of the system is that chemicals which are usually incompatible, for example oxidizing agents, such as hypochlorite, with water treatment substances, such as NTA for example, can be used alongside one another in the process. Further down in column 3, line 42 onwards, it is stated that various substances are known to improve penetration and to help soften and remove the soil. In addition, EP 282 214 A1 states that a basic formulation will typically contain an alkalinity source and a sequestrant source. On the bases of formulations such as these, it is possible to cater for special problems such as, for example, tea stains or other residues which may be found on tableware. After reading these passages from EP 282 214, and also after reading the following Example in column 4, line 3 onwards, the expert would inevitably conclude that it is normal to carry out processes of this kind with alkaline compositions - all the more so as it used to be the standard procedure.
As explained, however, the problem arises in practice that the wastewaters produced have a high pH because of the high levels of alkalinity attributable - depending on the process - to large quantities of alkaline cleaning solutions and/or to high concentrations of alkaline detersive substances. Accordingly, it is also necessary (and indeed often even stipulated in wastewater regulations), particularly when following the teaching of EP 282 214, for the alkalinity used for the cleaning process to be neutralized with acids to a certain pH either before or during treatment of the wastewater.
Accordingly, the problem addressed by the present invention was to provide a process which, firstly, would solve the cleaning problem posed by EP 282 214 without the need for thorough cleaning. Secondly and as a limitation with respect to EP 282 214, the problem addressed
As explained, however, the problem arises in practice that the wastewaters produced have a high pH because of the high levels of alkalinity attributable - depending on the process - to large quantities of alkaline cleaning solutions and/or to high concentrations of alkaline detersive substances. Accordingly, it is also necessary (and indeed often even stipulated in wastewater regulations), particularly when following the teaching of EP 282 214, for the alkalinity used for the cleaning process to be neutralized with acids to a certain pH either before or during treatment of the wastewater.
Accordingly, the problem addressed by the present invention was to provide a process which, firstly, would solve the cleaning problem posed by EP 282 214 without the need for thorough cleaning. Secondly and as a limitation with respect to EP 282 214, the problem addressed
5 by the invention was to minimize the time and effort involved in neutralization before or during treatment in wastewater treatment plants.
At the same time, care would be taken where possible to ensure that applicational requirements with regard to equipment and other factors would be satisfied.
The present invention relates to a process for continuous or discontinuous machine dishwashing, in which the tableware is treated at least in one process step with an acidic cleaning solution and, in another process step, with an alkaline cleaning solution, comprising the steps of a) applying an acidic aqueous cleaning solution to the at least partly soiled tableware and b) removing said acidic aqueous cleaning solution and the soil in one or more following steps, the at least one alkaline treatment taking place before and/or after the acidic treatment and the alkaline and at least one acidic aqueous cleaning solution at least partially neutralizing one another.
In the process according to the invention, the acidic cleaning solution mentioned contains one or more acids selected from the mineral and/or organic acids. In a particularly preferred embodiment, at least one acid is present which is selected from sulfuric acid, nitric acid, phosphoric acid, formic acid, acetic acid, propanoic acid, glycolic acid, citric acid, malefic acid, lactic acid, gluconic acid, alkanesulfonic acid, amidosulfonic acid, succinic acid, glutaric acid, adipic acid, phosphonic acids, polyacrylic acids or mixtures thereof and, in a most particularly embodiment, from formic acid, glycolic acid, gluconic acid, amidosulfonic acid or the alkanesulfonic acids, more particularly methanesulfonic acid
At the same time, care would be taken where possible to ensure that applicational requirements with regard to equipment and other factors would be satisfied.
The present invention relates to a process for continuous or discontinuous machine dishwashing, in which the tableware is treated at least in one process step with an acidic cleaning solution and, in another process step, with an alkaline cleaning solution, comprising the steps of a) applying an acidic aqueous cleaning solution to the at least partly soiled tableware and b) removing said acidic aqueous cleaning solution and the soil in one or more following steps, the at least one alkaline treatment taking place before and/or after the acidic treatment and the alkaline and at least one acidic aqueous cleaning solution at least partially neutralizing one another.
In the process according to the invention, the acidic cleaning solution mentioned contains one or more acids selected from the mineral and/or organic acids. In a particularly preferred embodiment, at least one acid is present which is selected from sulfuric acid, nitric acid, phosphoric acid, formic acid, acetic acid, propanoic acid, glycolic acid, citric acid, malefic acid, lactic acid, gluconic acid, alkanesulfonic acid, amidosulfonic acid, succinic acid, glutaric acid, adipic acid, phosphonic acids, polyacrylic acids or mixtures thereof and, in a most particularly embodiment, from formic acid, glycolic acid, gluconic acid, amidosulfonic acid or the alkanesulfonic acids, more particularly methanesulfonic acid
6 or mixtures thereof.
The aqueous acidic cleaning solution to be sprayed on in accordance with the invention preferably contains as further components a corrosion inhibitor and/or a typical complexing agent which, in a particularly preferred embodiment, is selected from the phosphonic acids, more particularly dioctyl phosphonic acid.
In another preferred embodiment of the process according to the present invention, the acidic cleaning solution contains between 0.01 and 10% by weight of one or more detersive substances, based on the cleaning solution. In a particularly preferred embodiment, the acidic cleaning solution mentioned contains less than 0.9% by weight, more particularly less than 0.8% by weight and, in a most particularly preferred embodiment, less than 0.5% by weight of one or more detersive substances, based on the cleaning solution.
The exact conditions also depend on the more precise practical circumstances and the performance requirements the process is expected to meet. For example, if there is a risk of corrosion where the acid concentration in the acidic cleaning solution is too high through plant-specific circumstances in practice, then it is advisable to use weakly acidic cleaning solutions with an active acid content of less than 0.9% by weight, preferably less than 0.8% by weight and more particularly less than 0.5% by weight. Depending on machine parameters, weakly acidic cleaning solutions may also have the advantage that the consumption of the lye baths into which the possibly acidic solution is carried over is not too high.
Apart from the performance-related requirements, when the process is considered as a whole, this procedure also leads to a reduction in pollution of the wastewater, in contrast to EP 282 214, because of the partial neutralization. As a result, less effort is involved before further treatment of the wastewater.
The aqueous acidic cleaning solution to be sprayed on in accordance with the invention preferably contains as further components a corrosion inhibitor and/or a typical complexing agent which, in a particularly preferred embodiment, is selected from the phosphonic acids, more particularly dioctyl phosphonic acid.
In another preferred embodiment of the process according to the present invention, the acidic cleaning solution contains between 0.01 and 10% by weight of one or more detersive substances, based on the cleaning solution. In a particularly preferred embodiment, the acidic cleaning solution mentioned contains less than 0.9% by weight, more particularly less than 0.8% by weight and, in a most particularly preferred embodiment, less than 0.5% by weight of one or more detersive substances, based on the cleaning solution.
The exact conditions also depend on the more precise practical circumstances and the performance requirements the process is expected to meet. For example, if there is a risk of corrosion where the acid concentration in the acidic cleaning solution is too high through plant-specific circumstances in practice, then it is advisable to use weakly acidic cleaning solutions with an active acid content of less than 0.9% by weight, preferably less than 0.8% by weight and more particularly less than 0.5% by weight. Depending on machine parameters, weakly acidic cleaning solutions may also have the advantage that the consumption of the lye baths into which the possibly acidic solution is carried over is not too high.
Apart from the performance-related requirements, when the process is considered as a whole, this procedure also leads to a reduction in pollution of the wastewater, in contrast to EP 282 214, because of the partial neutralization. As a result, less effort is involved before further treatment of the wastewater.
7 In another preferred embodiment of the process according to the invention, the acidic aqueous cleaning solution is allowed to act on the tableware and the soil for a certain contact time (during which spraying stops), the contact time preferably being 2 to 100 seconds, more preferably 5 to 100 seconds and most preferably 8 to 25 seconds. In another preferred embodiment, the tableware is not intentionally sprayed during the contact time.
In another preferred embodiment, the acidic aqueous cleaning solution is sprayed onto the tableware as a fine, gentle mist-like liquid spray.
In another preferred embodiment of the process according to the invention, the acidic cleaning solution is applied to the tableware as foam.
It is pointed out at this juncture that other forms of application may also be considered and that the success of the method does not depend on the form of application alone. For example, the cleaning solution could also be applied to the tableware in droplet form or by the Ecolab process known commercially as thin film cleaning (TFC).
Depending on the form of application, appropriate nozzles or alternative aids are preferably used. In the practical application of the process according to the invention, the acidic cleaning solution is preferably applied before the final rinse cycle or the final rinse zone.
Another preferred embodiment of the process according to the invention is characterized in that the treatment with the acidic cleaning solution is preceded by an alkaline treatment of the tableware of which the pH is a particularly preferred embodiment is above 10. In another preferred embodiment, the treatment with the acidic cleaning solution is followed by an alkaline treatment of the tableware. In a most particularly preferred embodiment, however, the tableware is subjected in all to at least three cleaning steps, the treatment with the acidic cleaning solution being preceded and followed by an alkaline treatment of the tableware.
It should be further explained that, where least two alkaline steps occur in the process according to the invention, the alkaline step taking place earlier in the process sequence - in a particularly preferred embodiment - has a lower pH than the alkaline step taking place later in the process sequence. This is advantageous in order to minimize consumption in an acidic step taking place between the two alkaline steps mentioned.
In a preferred embodiment of the alkaline treatment mentioned in the process according to the invention, the tableware comes into contact with one or more aqueous cleaning solutions containing between 0.1 and 4% by weight of an alkali carrier, preferably a hydroxide selected from sodium hydroxide, potassium hydroxide or mixtures thereof.
Other preferred alkali carriers - in addition to or instead of hydroxides selected from sodium and potassium hydroxide - include, for example, alkali metal silicates, ethanolamines, such as triethanolamine, diethanolamine and monoethanolamine, and also alkali metal carbonates of an alkali carrier, preferably a hydroxide selected from sodium or potassium hydroxide. Other alkali carriers may of course also be used because it is principally a matter of increasing the pH.
The present invention also relates to an institutional dishwashing machine comprising. several tanks which are arranged adjacent one another in known manner on the cascade principle and from which rinse or wash liquor is sprayed onto the tableware and then drains back into the tanks, the tanks intended for one or more acidic cleaning steps in the operation of the process according to the invention being made of acid-resistant material and/or lined with acid-resistant material.
In addition, the present invention relates to a single-tank washing machine, for example a domestic dishwasher, which can be used in a process according to the invention and which is made of and/or lined with acid-resistant material, more particularly in the places where it comes in to contact with acidic cleaning solutions.
The process of the invention has the further advantage that mineralic deposits on glass and dishes, like lime deposits, which are soluble in acidic solution are removed.
Example 1:
Cleaning of dinner plates in a Krefft~ single-tank dishwashing machine For each test, 10 new, dry dinner plates were soiled with starch at room temperature by a standardized test method. To this end, a ca. 6%
aqueous composition containing corn starch was cooled to 75°C after boiling and was applied to each plate with a brush in a quantity of ca. 4 ml. The plates thus treated were left to stand for at least 3 hours and then dried at ca. 100°C for 16 hours. After the plates had cooled, comparison tests were carried out in a Krefft~ single-tank dishwashing machine according to the following scheme:
a) Cleaning for 1 minute with a 0.3% by weight aqueous solution of a standard alkaline detergent which remains constant (ca. 17% by weight alkali metal hydroxide, 14% by weight tripolyphosphate and 1.5% by weight alkali metal hypochlorite and ca. 1 % by weight alkali silicate and the remainder water).
b) Whole-surface spraying of the plates area using different kinds of spray-on solutions - of which the composition is described in more detail in Table 1 - for the various tests.
c) Allowing the spray-on solution applied to act for 30 seconds.
d) Cleaning for 2 minutes with a solution according to a).
The cleaning solutions and spray-on solutions were prepared with softened water. The cleaning temperature in the Krefft° single-tank dishwashing machine was 60°C.
6 tests were first carried out to the described scheme, the composition of cleaning solutions a) and d) being maintained and only the spray-on solution being varied from test to test.
5 Cleaning was evaluated by scoring on a scale of 1 ( = no visible sign of cleaning) to 10 (= complete removal of soil).
The results of the 6 tests are se out in Table 1.
Table 1:
10 Cleaning results in tests to the described scheme, only the spray-on solution being varied from test to test.
Test Spray~on solution Evaluation of cleaning performance 1 1% NaOH 4.6 2 0.3 gll Perzym (= enzyme-containing1.2 product) 3 0.4% methanesulfonic acid 9.0 4 0.7% by weight methanesulfonic9.5 acid 5 1% by weight methanesulfonic9.5 acid 6 Water 1.2 As can be seen from Table 1, by far the best cleaning results were achieved in tests 3 to 5 where a solution of methanesulfonic acid was used as the spray-on solution. Accordingly, the cleaning principle in this very advantageous case consisted in cleaning first with alkaline solution, then with acidic solution and, after that, with alkaline solution again.
Further investigations showed that similar results could also be obtained with other acids. Particularly emphasis is placed in this regard on the organic acids: formic acid, glycolic acid, gluconic acid, amidosulfonic acid or other alkanesulfonic acids, more particularly with an alkane chain of 1 to 4 C atoms.
As can be seen from this simple test arrangement, it is possible by alternating the pH to achieve excellent cleaning results in practice, even with acid concentrations of less than 0.5% by weight of active acid.
It is also clear that, by using lower acid concentrations, there is a reduction in the undesirable partial neutralization in the cleaning process, for example because of residues of cleaning solution adhering to the tableware which are treated in the next step with a cleaning solution of opposite pH.
Example 2:
Test in a conveyor dishwasher machine Meiko GSM
The following test was made in a conveyor dishwasher machine Meiko GSM~' The tests were carried out with soiled dishes from a cantine. The conditions in the Meiko GSM dishwashing machine were as follows:
As cleaner Perclin~ Intensiv Flussig (1,5 g/I; 3,2 mS/cm) was used. In the machine softened water in an amount of 500 I/h was used. The acid content was 1,4 to 1,5% phosphoric acid. The machine had a built in spraying system with a spraying amount of 36 I/h and a pressure of 4 bar.
Table 2 shows the cleaning results dependant from the different pH-values in the different bars.
Table 2 pH-Value Cleaning Time Bath 1 Bath 2 Bath 3 Result Start 10,7 10,6 10,7 6 10 10,2 10,4 10,6 6 20 9,8 10,3 10,5 5,5 9,7 10,2 10,4 5,5 40 9,6 9,9 10,3 3,5 50 9,5 9,5 10,3 2 60 9,4 9,5 10,3 In the further tests, a dripping plate was installed in the bars with a spraying system to prevent that acid is running into the alkaline wash tanks. Furthermore, the concentration of the acid was reduced to 1 phosphoric acids. All other parameters were not changed. The results are shown in table 3.
Table 3 pH-Value Cleaning Time Tank 1 Tank 2 Tank 3 Result Start (without10,5 10,5 10,6 0,5 acid) Start (with10,5 10,5 10,6 9 acid) min 10,5 10,5 10,6 9 min 10,4 10,4 10,7 7 min 10,1 10,4 10,5 3,5 min 10,0 10,4 10,4 4 min 10,4 10,4 10,8 5,5 min 10,0 10,3 10,5 5 min 10,2 10,5 10,8 5 90 min 9,9 10,2 10,4 6 120 min 9,8 10,3 10,4 5,5 120 min 9,8 10,3 10,4 0 (without acid) 10 From table 2 and 3 can be seen that a very good cleaning result is only achieved if the pH-value of the first step is at minimum 10 or higher. The cleaning performance with the acid step is always higher than without the acid step. This can be seen at the beginning and at the end of the test. Furthermore, it can be seen that a higher concentration of the phosphoric acid causes a better cleaning performance.
Example 3:
pH-relation between the first and third tank of Meiko GSM
To find the best pH-relation from the first and the third tank for the Meiko GSM, a test with two Krefft° single-tank dishwasher was performed.
In the first machine a pH was adjusted with NaOH, a second pH was adjusted in the second Krefft~ dishwashing machine. The water was softened with pH of 9,8 and the temperature was 60° C in both machines. The first step was one minute cleaning followed by a spraying step with a 1 % phosphoric acid and a contact time of 30 seconds and an additional cleaning step of two minutes. Results are shown in the following table 4.
Table 4 pH Krefft 1 pH Krefft 2 Cleaning Result 9,8 12 8 12 9,8 6 11 11 6,5 From the table can be seen that it seems to be the best to start with a pH-value of about 11 and the acid step and follow then with an alkaline step which is higher in alkalinity than the first one.
In another preferred embodiment, the acidic aqueous cleaning solution is sprayed onto the tableware as a fine, gentle mist-like liquid spray.
In another preferred embodiment of the process according to the invention, the acidic cleaning solution is applied to the tableware as foam.
It is pointed out at this juncture that other forms of application may also be considered and that the success of the method does not depend on the form of application alone. For example, the cleaning solution could also be applied to the tableware in droplet form or by the Ecolab process known commercially as thin film cleaning (TFC).
Depending on the form of application, appropriate nozzles or alternative aids are preferably used. In the practical application of the process according to the invention, the acidic cleaning solution is preferably applied before the final rinse cycle or the final rinse zone.
Another preferred embodiment of the process according to the invention is characterized in that the treatment with the acidic cleaning solution is preceded by an alkaline treatment of the tableware of which the pH is a particularly preferred embodiment is above 10. In another preferred embodiment, the treatment with the acidic cleaning solution is followed by an alkaline treatment of the tableware. In a most particularly preferred embodiment, however, the tableware is subjected in all to at least three cleaning steps, the treatment with the acidic cleaning solution being preceded and followed by an alkaline treatment of the tableware.
It should be further explained that, where least two alkaline steps occur in the process according to the invention, the alkaline step taking place earlier in the process sequence - in a particularly preferred embodiment - has a lower pH than the alkaline step taking place later in the process sequence. This is advantageous in order to minimize consumption in an acidic step taking place between the two alkaline steps mentioned.
In a preferred embodiment of the alkaline treatment mentioned in the process according to the invention, the tableware comes into contact with one or more aqueous cleaning solutions containing between 0.1 and 4% by weight of an alkali carrier, preferably a hydroxide selected from sodium hydroxide, potassium hydroxide or mixtures thereof.
Other preferred alkali carriers - in addition to or instead of hydroxides selected from sodium and potassium hydroxide - include, for example, alkali metal silicates, ethanolamines, such as triethanolamine, diethanolamine and monoethanolamine, and also alkali metal carbonates of an alkali carrier, preferably a hydroxide selected from sodium or potassium hydroxide. Other alkali carriers may of course also be used because it is principally a matter of increasing the pH.
The present invention also relates to an institutional dishwashing machine comprising. several tanks which are arranged adjacent one another in known manner on the cascade principle and from which rinse or wash liquor is sprayed onto the tableware and then drains back into the tanks, the tanks intended for one or more acidic cleaning steps in the operation of the process according to the invention being made of acid-resistant material and/or lined with acid-resistant material.
In addition, the present invention relates to a single-tank washing machine, for example a domestic dishwasher, which can be used in a process according to the invention and which is made of and/or lined with acid-resistant material, more particularly in the places where it comes in to contact with acidic cleaning solutions.
The process of the invention has the further advantage that mineralic deposits on glass and dishes, like lime deposits, which are soluble in acidic solution are removed.
Example 1:
Cleaning of dinner plates in a Krefft~ single-tank dishwashing machine For each test, 10 new, dry dinner plates were soiled with starch at room temperature by a standardized test method. To this end, a ca. 6%
aqueous composition containing corn starch was cooled to 75°C after boiling and was applied to each plate with a brush in a quantity of ca. 4 ml. The plates thus treated were left to stand for at least 3 hours and then dried at ca. 100°C for 16 hours. After the plates had cooled, comparison tests were carried out in a Krefft~ single-tank dishwashing machine according to the following scheme:
a) Cleaning for 1 minute with a 0.3% by weight aqueous solution of a standard alkaline detergent which remains constant (ca. 17% by weight alkali metal hydroxide, 14% by weight tripolyphosphate and 1.5% by weight alkali metal hypochlorite and ca. 1 % by weight alkali silicate and the remainder water).
b) Whole-surface spraying of the plates area using different kinds of spray-on solutions - of which the composition is described in more detail in Table 1 - for the various tests.
c) Allowing the spray-on solution applied to act for 30 seconds.
d) Cleaning for 2 minutes with a solution according to a).
The cleaning solutions and spray-on solutions were prepared with softened water. The cleaning temperature in the Krefft° single-tank dishwashing machine was 60°C.
6 tests were first carried out to the described scheme, the composition of cleaning solutions a) and d) being maintained and only the spray-on solution being varied from test to test.
5 Cleaning was evaluated by scoring on a scale of 1 ( = no visible sign of cleaning) to 10 (= complete removal of soil).
The results of the 6 tests are se out in Table 1.
Table 1:
10 Cleaning results in tests to the described scheme, only the spray-on solution being varied from test to test.
Test Spray~on solution Evaluation of cleaning performance 1 1% NaOH 4.6 2 0.3 gll Perzym (= enzyme-containing1.2 product) 3 0.4% methanesulfonic acid 9.0 4 0.7% by weight methanesulfonic9.5 acid 5 1% by weight methanesulfonic9.5 acid 6 Water 1.2 As can be seen from Table 1, by far the best cleaning results were achieved in tests 3 to 5 where a solution of methanesulfonic acid was used as the spray-on solution. Accordingly, the cleaning principle in this very advantageous case consisted in cleaning first with alkaline solution, then with acidic solution and, after that, with alkaline solution again.
Further investigations showed that similar results could also be obtained with other acids. Particularly emphasis is placed in this regard on the organic acids: formic acid, glycolic acid, gluconic acid, amidosulfonic acid or other alkanesulfonic acids, more particularly with an alkane chain of 1 to 4 C atoms.
As can be seen from this simple test arrangement, it is possible by alternating the pH to achieve excellent cleaning results in practice, even with acid concentrations of less than 0.5% by weight of active acid.
It is also clear that, by using lower acid concentrations, there is a reduction in the undesirable partial neutralization in the cleaning process, for example because of residues of cleaning solution adhering to the tableware which are treated in the next step with a cleaning solution of opposite pH.
Example 2:
Test in a conveyor dishwasher machine Meiko GSM
The following test was made in a conveyor dishwasher machine Meiko GSM~' The tests were carried out with soiled dishes from a cantine. The conditions in the Meiko GSM dishwashing machine were as follows:
As cleaner Perclin~ Intensiv Flussig (1,5 g/I; 3,2 mS/cm) was used. In the machine softened water in an amount of 500 I/h was used. The acid content was 1,4 to 1,5% phosphoric acid. The machine had a built in spraying system with a spraying amount of 36 I/h and a pressure of 4 bar.
Table 2 shows the cleaning results dependant from the different pH-values in the different bars.
Table 2 pH-Value Cleaning Time Bath 1 Bath 2 Bath 3 Result Start 10,7 10,6 10,7 6 10 10,2 10,4 10,6 6 20 9,8 10,3 10,5 5,5 9,7 10,2 10,4 5,5 40 9,6 9,9 10,3 3,5 50 9,5 9,5 10,3 2 60 9,4 9,5 10,3 In the further tests, a dripping plate was installed in the bars with a spraying system to prevent that acid is running into the alkaline wash tanks. Furthermore, the concentration of the acid was reduced to 1 phosphoric acids. All other parameters were not changed. The results are shown in table 3.
Table 3 pH-Value Cleaning Time Tank 1 Tank 2 Tank 3 Result Start (without10,5 10,5 10,6 0,5 acid) Start (with10,5 10,5 10,6 9 acid) min 10,5 10,5 10,6 9 min 10,4 10,4 10,7 7 min 10,1 10,4 10,5 3,5 min 10,0 10,4 10,4 4 min 10,4 10,4 10,8 5,5 min 10,0 10,3 10,5 5 min 10,2 10,5 10,8 5 90 min 9,9 10,2 10,4 6 120 min 9,8 10,3 10,4 5,5 120 min 9,8 10,3 10,4 0 (without acid) 10 From table 2 and 3 can be seen that a very good cleaning result is only achieved if the pH-value of the first step is at minimum 10 or higher. The cleaning performance with the acid step is always higher than without the acid step. This can be seen at the beginning and at the end of the test. Furthermore, it can be seen that a higher concentration of the phosphoric acid causes a better cleaning performance.
Example 3:
pH-relation between the first and third tank of Meiko GSM
To find the best pH-relation from the first and the third tank for the Meiko GSM, a test with two Krefft° single-tank dishwasher was performed.
In the first machine a pH was adjusted with NaOH, a second pH was adjusted in the second Krefft~ dishwashing machine. The water was softened with pH of 9,8 and the temperature was 60° C in both machines. The first step was one minute cleaning followed by a spraying step with a 1 % phosphoric acid and a contact time of 30 seconds and an additional cleaning step of two minutes. Results are shown in the following table 4.
Table 4 pH Krefft 1 pH Krefft 2 Cleaning Result 9,8 12 8 12 9,8 6 11 11 6,5 From the table can be seen that it seems to be the best to start with a pH-value of about 11 and the acid step and follow then with an alkaline step which is higher in alkalinity than the first one.
Claims (19)
1. A process for continuous or discontinuous machine dishwashing, in which the tableware is treated at least in one process step with an acidic cleaning solution and, in another process step, with an alkaline cleaning solution, comprising the steps of a) applying an acidic aqueous cleaning solution before the final rinse cycle or the final rinse zone to the at least partly soiled tableware and b) removing the acidic aqueous cleaning solution and the soil in one or more following steps, the at least one alkaline treatment taking place before and/or after the acidic treatment and the alkaline and at least one acidic aqueous cleaning solution at least partially neutralizing one another.
2. A process as claimed in claim 1, characterized in that the acidic aqueous cleaning solution contains one or more acids selected from the mineral and/or organic acids.
3. A process as claimed in claim 2, characterized in that at least one acid is present which is selected from sulfuric acid, nitric acid, phosphoric acid, formic acid, acetic acid, propanoic acid, glycolic acid, citric acid, maleic acid, lactic acid, gluconic acid, alkane sulfonic acid, amidosulfonic acid, succinic acid, glutaric acid, adipic acid, oxalic acid, benzoic acid, phosphonic acids, polyacrylic acids or mixtures thereof.
4. A process as claimed in claim 3, characterized in that at least one acid is present which is selected from formic acid, glycolic acid, gluconic acid, amidosulfonic acid or the alkanesulfonic acids, more particularly methanesulfonic acid or mixtures thereof.
5. A process as claimed in one or more of claims 1 to 4, characterized in that the acidic aqueous cleaning solution contains between 0.01 and 10% by weight of one or more detersive substances, based on the cleaning solution.
6. A process as claimed in claim 5, characterized in that the acidic aqueous cleaning solution contains less than 0.9% by weight, preferably less than 0.8% by weight and more preferably less than 0.5% by weight of one or more detersive substances, based on the cleaning solution.
7. A process as claimed in one or more of claims 1 to 6, characterized in that the acidic aqueous cleaning solution is allowed to act on to the tableware and the soil for a certain contact time (during which spraying stops), the contact time of this aqueous cleaning solution with the tableware preferably being 2 to 100 seconds, more preferably 5 to 100 seconds and most preferably 8 to 25 seconds.
8. A process as claimed in claim 7, characterized in that the tableware is not intentionally sprayed during the contact time.
9. A process as claimed in claims 1 to 8, characterized in that the acidic aqueous cleaning solution is sprayed onto the tableware as a fine, gentle, mist-like liquid spray.
10. A process as claimed in one or more of claims 1 to 8, characterized in that the acidic aqueous cleaning solution is applied to the tableware as foam.
11. A process as claimed in claim 9 or 10, characterized in that the acidic aqueous cleaning solution is applied through suitable nozzles.
12. A process as claimed in one or more of claims 1 to 11, characterized in that the treatment with the acidic aqueous cleaning solution is preceded by an alkaline treatment.
13. A process as claimed in claim 12, characterized in that an aqueous cleaning solution having a pH above 10 is used for the alkaline treatment of the tableware.
14. A process as claimed in one or more of claims 1 to 13, characterized in that the treatment with the acidic aqueous cleaning solution is followed by an alkaline treatment of the tableware.
15. A process as claimed in one or more of claims 12 to 14, characterized in that the tableware is subjected in all to at least three cleaning steps, an alkaline treatment of the tableware being carried out before and after the treatment with the acidic aqueous cleaning solution.
16. A process as claimed in one or more of claims 12 to 15, characterized in that, during the alkaline treatment, the tableware is contacted with one or more aqueous cleaning solutions which contain between 0.1 and 4% by weight of an alkali carrier, preferably a hydroxide selected from sodium hydroxide, potassium hydroxide or mixtures thereof.
17. A process as claimed in one or more of claims 1 to 16, characterized in that the pH of the wastewater produced by the process is below 12, preferably below 11.
18. An institutional dishwashing machine comprising several tanks which are arranged adjacent one another in known manner on the cascade principle and from which rinse or wash liquor is sprayed onto the tableware and then drains back into the tanks, characterized in that the tanks intended for one or more acidic cleaning steps in accordance with the invention with one or more claims 1 to 17 are made of and/or lined with acid-resistant material.
19. A single-tank washing machine, for example a domestic dishwasher, which is suitable for the process claimed in one or more of claims 1 to 15 and which is made of and/or lined with acid-resistant material, more particularly in the places where it comes in to contact with acidic cleaning solutions.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE10257391.3 | 2002-12-06 | ||
DE10257391A DE10257391A1 (en) | 2002-12-06 | 2002-12-06 | Continuous or discontinuous machine dishwashing of soiled tableware comprises applying acidic aqueous cleaning solution to soiled tableware and performing alkaline treatment before and/or after acidic treatment |
PCT/EP2003/012366 WO2004052564A1 (en) | 2002-12-06 | 2003-11-06 | Acidic cleaning method for machine dishwashing |
Publications (2)
Publication Number | Publication Date |
---|---|
CA2502423A1 CA2502423A1 (en) | 2004-06-24 |
CA2502423C true CA2502423C (en) | 2010-08-03 |
Family
ID=32336137
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA2502423A Expired - Lifetime CA2502423C (en) | 2002-12-06 | 2003-11-06 | Acidic cleaning method for machine dishwashing |
Country Status (7)
Country | Link |
---|---|
EP (1) | EP1567289B2 (en) |
AT (1) | ATE362807T2 (en) |
AU (1) | AU2003279362B2 (en) |
BR (1) | BR0316171A (en) |
CA (1) | CA2502423C (en) |
DE (2) | DE10257391A1 (en) |
WO (1) | WO2004052564A1 (en) |
Families Citing this family (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US8092613B2 (en) | 2002-05-31 | 2012-01-10 | Ecolab Usa Inc. | Methods and compositions for the removal of starch |
WO2005068598A1 (en) * | 2003-12-18 | 2005-07-28 | Ecolab Inc. | Methods and compositions for the removal of starch |
US8426349B2 (en) * | 2009-05-26 | 2013-04-23 | Delaval Holding Ab | Chlorinated alkaline pipeline cleaner with methane sulfonic acid |
DE102011017294A1 (en) | 2011-04-15 | 2012-10-18 | Meiko Maschinenbau Gmbh & Co. Kg | Transport dishwasher with special treatment zones |
WO2012160498A2 (en) | 2011-05-20 | 2012-11-29 | Ecolab Usa Inc. | Acid formulations for use in a system for warewashing |
EP2792737A1 (en) * | 2011-05-20 | 2014-10-22 | Ecolab USA Inc. | Non-phosphate detergents and non-phosphoric acids in an alternating alkali/acid system for warewashing |
US9357898B2 (en) | 2011-12-13 | 2016-06-07 | Ecolab Usa Inc. | Method of separating chemistries in a door-type dishmachine |
ES2750872T3 (en) | 2011-12-13 | 2020-03-27 | Ecolab Usa Inc | Dishwashing method |
WO2016179009A1 (en) * | 2015-05-07 | 2016-11-10 | Cryovac, Inc. | Container washing and detergent for use thereof |
US11421191B1 (en) | 2018-11-15 | 2022-08-23 | Ecolab Usa Inc. | Acidic cleaner |
WO2024164162A1 (en) * | 2023-02-08 | 2024-08-15 | Ecolab Usa Inc. | A low-temperature, caustic dishware sanitizing method |
Family Cites Families (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE1628632C3 (en) * | 1966-11-26 | 1980-10-09 | Henkel Kgaa, 4000 Duesseldorf | Process for machine washing of dishes |
DE1703441A1 (en) * | 1968-05-21 | 1971-12-09 | Bosch Hausgeraete Gmbh | Dishwasher |
DE3532552A1 (en) * | 1985-09-12 | 1987-03-12 | Henkel Kgaa | METHOD FOR ADJUSTING A PH AREA IN THE WASTE WATER AND DEVICE FOR CARRYING OUT THE METHOD |
DE3707366A1 (en) * | 1987-03-07 | 1988-09-15 | Diversey Gmbh | METHOD FOR THE CONTINUOUS OR DISCONTINUOUS MACHINE CLEANING OF CLEANING UTENSILS |
DE4113024A1 (en) * | 1991-04-20 | 1992-10-22 | Henkel Kgaa | METHOD FOR THE MACHINE CLEANING OF Crockery |
TW338713B (en) * | 1995-09-06 | 1998-08-21 | Sharp Kk | A dishwasher |
US5879469A (en) * | 1997-01-06 | 1999-03-09 | Deeay Technologies Ltd. | Dishwashing method and detergent composition therefor |
WO2000046329A1 (en) * | 1999-02-05 | 2000-08-10 | Unilever Plc | Dish washing process and compositions relating thereto |
WO2002031095A1 (en) * | 2000-10-10 | 2002-04-18 | Johnsondiversey, Inc. | A detergent composition and method for warewashing |
DE10127919A1 (en) * | 2001-06-08 | 2002-12-19 | Ecolab Gmbh & Co Ohg | Washing processes, for removing mineral or starch deposits in industrial or domestic dishwashers is effected with both alkaline and acidic stages |
-
2002
- 2002-12-06 DE DE10257391A patent/DE10257391A1/en not_active Ceased
-
2003
- 2003-11-06 WO PCT/EP2003/012366 patent/WO2004052564A1/en active IP Right Grant
- 2003-11-06 AU AU2003279362A patent/AU2003279362B2/en not_active Ceased
- 2003-11-06 BR BR0316171-4A patent/BR0316171A/en not_active Application Discontinuation
- 2003-11-06 EP EP03772309.5A patent/EP1567289B2/en not_active Expired - Lifetime
- 2003-11-06 CA CA2502423A patent/CA2502423C/en not_active Expired - Lifetime
- 2003-11-06 DE DE60314007.6T patent/DE60314007T3/en not_active Expired - Lifetime
- 2003-11-06 AT AT03772309T patent/ATE362807T2/en active
Also Published As
Publication number | Publication date |
---|---|
EP1567289B2 (en) | 2017-06-07 |
BR0316171A (en) | 2005-09-27 |
WO2004052564A1 (en) | 2004-06-24 |
DE60314007D1 (en) | 2007-07-05 |
AU2003279362A2 (en) | 2004-06-30 |
EP1567289B1 (en) | 2007-05-23 |
EP1567289A1 (en) | 2005-08-31 |
AU2003279362A1 (en) | 2004-06-30 |
DE10257391A1 (en) | 2004-06-24 |
AU2003279362B2 (en) | 2009-03-12 |
CA2502423A1 (en) | 2004-06-24 |
DE60314007T2 (en) | 2008-01-24 |
DE60314007T3 (en) | 2017-10-12 |
ATE362807T2 (en) | 2007-06-15 |
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