NO152014B - DOUBLE DISHWASH - Google Patents

Description

The invention relates to a liquid dishwashing liquid with improved cleaning performance. More particularly, the invention relates to an aqueous washing-up liquid which is particularly suitable for manual cleaning of plates, glasses, kitchen utensils, cutlery and the like. The liquid washing-up liquid according to the invention contains juice of a citrus fruit, e.g. lemon juice.

Liquid detergent compositions containing lemon juice are known in the art. US Patent No. 3,650,968 describes cleaning agents for removing fish odors, which comprise 30-80% by weight water, 0.1-35% by weight detergent and 0.1-15% by weight citrus juice (lemon juice). These liquid detergent mixtures, however, have very poor washing-up properties and therefore cannot be used satisfactorily for cleaning plates, glasses, kitchen utensils, cutlery and the like.

It is an aim of the invention to provide an effective liquid washing-up agent which is also particularly effective against difficult dirt, e.g. from plates, pots and pans and other kitchen utensils.

By "difficult dirt" is meant here the difficult end of

the dishwashing spectrum, e.g. burnt-in proteins and starch dirt.

These and other purposes of the invention, which will appear

of the following, can be obtained by combining an organic synthetic surfactant system of two surfactants as defined below, with a citrus juice in an amount of 5-50

% by weight, based on the whole mixture. Any juice of a citrus fruit belonging to the general class of citrus fruits

can be used, eg: sweet oranges (citrus sinensis); sour or bitter oranges (citrus auranticum); tangerines (citrus reticulata); grapefruit (citrus paradisi); pumelos (citrus grandis); lemons (citrus limon); lime (citrus aurantifolia); lemons (citrus medica); papeda (citrus hystrix) and trifoliate oranges (citrus trifoliata), although lemon juice will be preferred in connection with the invention because it has been established with regard to consumer acceptability.

Unless otherwise stated, the percentages of fruit juice given in this description refer to single strength fruit juice. The term "single strength" is used here to indicate the average strength of juice squeezed from the fruit. If concentrated juices are used, these will be indicated by designating the strength factor, e.g. as "4x concentrate".

The products according to the invention are therefore especially made for general use for conventional dishwashing. They can be used in the concentrated aqueous form or in the conventional, highly diluted dishwashing operation, and which provide a good cleaning effect combined with a consumer-acceptable foam level and foam stability.

Consequently, the aqueous washing-up liquid according to the invention, which has a pH value of 5.5-10, comprises an organic surfactant system and a citrus juice, and this washing-up liquid is characterized in that it consists essentially of

a) 5-50% by weight of citrus juice of single strength, or an equivalent amount of a juice of multiple strength, b) 15-43% by weight of an organic synthetic surfactant system consisting of 1) 60-90% by weight calculated on the surface-active system, of a first surface-active agent selected from the group consisting of water-soluble C 6 -g alkylbenzenesulfonates and C 0 -n alkyl polyethoxy sulfates having 1-25 ethoxy groups;

and

2) 10-40% by weight, calculated on the surface-active system, of another surface-active agent selected from the group consisting of Co Q — z _ u-alkyl polyethoxy sulfates with 1-25 ethoxy groups, amine oxides with a C^0_2g~alkyl group and two C- L_4-alkyl- or -hydroxyalkyl groups, and Cg_24~ alkanol- or -alkylphenol ethoxylates with 5-30 ethoxy groups, under the condition that both the surface-active agents (1) and (2) cannot be Cg_20-alkylpolyethoxysulfates with 1-25 ethoxy groups, the surface-active agents, if they are ion-active, is present in the form of its alkali metal salts, ammonium salts, lower alkanolamine salts or lower alkylamine salts, c) commonly used solubilizing compounds and 0-80% by weight of water.

Examples of non-ionic water-soluble condensation products obtained by condensation of 5-30 mol of an alkylene oxide with 1 mol of an organic hydrophobic compound are: a) the condensates of ethylene oxide with aliphatic straight-chain or branched, primary or secondary alcohols with more than 8 carbon atoms , e.g. those derived from tallow or coconut fatty acids, containing 5-20 ethylene oxide groups, and branched C^-C^ alcohols condensed with 5-20 ethylene oxide groups; b) the condensates of ethylene oxide with alkylphenols, in which the phenols may be mono- or polyalkylated and the total number of carbon atoms in the side chain or chains is 5-18. Specific examples are the condensates of 1 mol of nonylphenol with 8-15 mol of ethylene oxide; c) the condensates of ethylene oxide with fatty acid esters, preferably monofatty acid esters of the sugar alcohols, sorbitol and mannitol oil d) polyethene oxyesters obtained by reaction of ethylene oxide with carboxylic acid, the latter being natural fatty acids or synthetic fatty acids made from oxidized paraffin wax having 8-20 carbon atoms, or alkylbenzo- or naphthenic acids having 5-18 carbon atoms in the alkyl chain; e) the condensation products of fatty acylalkanolamides of the type C7_17-alkyl-CO-NHC2H4OH, C7_17-alkyl-CO-N(C2H4OH)2 with ethylene oxide; f) the condensation ion products of C₆₆₆ alkyl, C₆₆₆-alkenyl and C₆₆₆ alkylarylamines with ethylene oxide. A specific example is

the condensation product of 1 mole of a dodecylamine with 9-12 moles of ethylene oxide.

Specific examples of amine oxides are dimethyldodecylamine oxide, diethyltetradecylamine oxide, bis-(2-hydroxyethyl)dodecylamine oxide and dimethyl-2-hydroxydodecylamine oxide.

It has been discovered that the surfactant system defined above can be used effectively in combination with citrus juice,

in particular lemon juice, in the above stated quantity ratios, for providing the desirable combined effect with regard to good washing ability, good foam performance and improved performance when it comes to difficult dirt, in particular burnt-in or dried-in proteins or starch sludge, over a wide pH range from practically acidic pH to alkaline pH, namely 5.5-10. A preferred pH range for the product according to the invention is

from 6 to 8.5, more particularly from 7 to 8.5.

Any combination of the first and second surfactants described above can be used to form the organic synthetic surfactant system in the product according to the invention.

Typical examples of surfactant systems are alkyl benzene sulphonate/alkyl polyethoxy sulphate mixtures; alkyl benzene sulfonate/alkyl polyethoxy sulfate/nonionic mixtures; alkyl sulfate/alkyl benzene sulfonate/alkyl polyethoxy sulfate mixtures and alkyl sulfate/alkyl polyethoxy sulfate/amine oxide mixtures.

As explained above, any type of citrus juice in an amount of 5-50% by weight can be used in connection with the invention, lemon, lime, orange and grapefruit juices being representative of the general class. The minimum amount of 5% by weight of citrus juice is used because the effect for lower amounts is not significant or practically zero. Although any proportion above 5% of citrus juice may be used, as far as is practical, it has been found that large amounts are not necessary to obtain the desired benefits. Also, since there is a clear drop in the increase in performance improvements with increasing juice content above 10%, and there is a rapid drop especially in the higher percentage range, the application of excessive amounts of juice will not justify the extra high costs that get involved.

50%, preferably 2 5%, is considered a convenient practical

upper limit for single-strength citrus juice in the product according to the invention, as citrus juice at concentrations above these percentages does not provide any additional benefits that would compensate for the large costs of extra citrus juice.

A citrus juice level which is particularly advantageous to use in the liquid detergent mixture according to the invention is from 5 to 10% by weight.

Citrus juices are available in the market. They are generally presented either as single-strength juices or as concentrates with different degrees of strength, i.e. from 2x concentrates and up to 10x concentrates. Lemon juice contains a number of different classes of chemical compounds including acids, sugars, amino acids, oils and trace elements. Analysis data regarding citrus juices can be found in the following literature:

a) "Chemical Constituents of Citrus Fruits", Supp. 2 (1970)

by Kefford and Chandler;

2) "Biochemistry of Fruits and their Products", Volume 1 (1970)

Oath. A. C. Hulme.

Within each class there are several different constituents which can be determined analytically. The main acid in citrus juice is citric acid, which is present in an amount of approx. 5-6% by weight.

It is not known exactly which of the constituents

is present in the citrus juice which is responsible for improving the cleaning effect, but it is believed that a synergistic effect is produced by the combination of one or more components present in the citrus juice and the active system used in the product in according to the invention.

In addition to the essential ingredients described above, the liquid detergent according to the invention may optionally contain other non-essential materials. Such optional ingredients include additional surfactants other than those specified as first and second surfactants in the organic synthetic surfactant system; building salts which can be added to speed up the cleaning and soil removal effectiveness of the surfactants in the product, e.g. phosphates, polyphosphates, phosphonates, carbonates, polyacetates and polycarboxylates; foam-producing agents, e.g. coconut fatty acid diethanolamide; hydrotropes and solubilizing agents, e.g. the lower alkanols containing 2-4 carbon atoms, especially ethanol, urea, sodium or potassium toluene sulphonate and sodium or potassium xylene sulphonate, which are generally added to induce phase stability especially in the case of mixtures with high concentrations of surfactants; preservatives; perfumes and dyes. Furthermore, if desired, acidic or alkaline substances for pH adjustment and also scouring agents can be mixed into the detergent according to the invention -

Preferred mixtures are those which contain 15-43% by weight of the organic synthetic surfactant system described above, 5-25% by weight lemon juice and approx. 15-75% by weight water. Particularly preferred are those which have an active detergent content of more than 35% by weight.

In the following, the invention shall be illustrated by means of examples:

Examples I-III

The following mixtures were made:

To determine how easy it is to clean baked-on dirt from substrates after soaking, the following half-tile comparison test method was used: Soiled substrates in the form of square enamel tiles (10 x 10 cm) are immersed in solutions of the test products (1 liter) at 0.15% concentrations. The solution is at 45°C at the start of the test and is reheated when the temperature drops to 40°C (using a small immersion coil). The tiles are examined to find the first signs that the dirt on one of them has softened, and then all are removed from the test solution and cleaned (immersion time varies between 5 and 50 min.). The cleaning is carried out for 30 seconds using a Brillo Swish sponge dipped in the relevant test solution.

Dirt and soiling method

The tests were carried out with fruit pie filling (cherry and apricot) and a mixture of flour and fruit pie filling (1:4). The pie filling is finely mashed by pressing it through a 240 µm sieve, and a fine paste is made from the flour/pie filling mixture.

The dirt is applied to the substrate by "screen printing", as two passes were used. The dirt is then burned in the middle of a large oven (Gallenkamp Oven Model OV330) for 4 minutes. The temperature must be 250°C before the soiled substrates are placed in the oven, and it is desirable that the insertion in the oven is done quickly so as to avoid the temperature falling below 220°C.

Results

These are fully reproduced in table 1 below.

Assessment was carried out by a technically trained jury, as the degree of dirt removal was graded according to the following scale:

0 = completely clean

1 = still somewhat soiled

2 = moderately soiled

3 = significantly soiled

4 = no visible cleaning.

The marks were taken as the average of 8 results for each product and control sample. Product A was used as a control sample.

From the above results, it is clear that the mixtures I, II and III according to the invention, with lemon juice,

are superior to mixtures A and B which lie outside the invention.

Example IV

The influence of the pH value was investigated by assessing the performance of the following liquid mixture in a soaking test.

Composition

Comparisons were made using the standard enamel tiles (10 x 10 cm) which were smeared with apricot pie filling/flour and baked as in Examples I-lli. Half-tile comparisons in 11.3° German hardness water were performed at 45°C.

Test products were tested randomly, and all tests were duplicated.

pH adjustments were made at 45°C using dilute sulfuric acid (0.1 M) and dilute sodium hydroxide (0.1 M), and measurement of the pH at the end of each test was also made.

A product of the above nominal composition without lemon juice was used as a control sample.

An assessment was made by a technically trained jury for

to determine the degree of dirt left on each half-tile, using the following scale:

0 = completely clean

1 = still somewhat soiled

2 = moderately soiled

3 = significantly soiled

4 = no visible cleaning

These grades were taken as an average (6 results for each test product and each control sample at each pH value),

and a dirt difference between the control sample and the test product was calculated.

The above table shows that the product according to the invention shows a clear superiority at pH 5.5, 7.0/8.5 and 10.0, the results at pH 8.5 being particularly good.

Example V

The procedure used was as follows:

1. An egg mixture was prepared by carefully mixing dried egg powder and water in a ratio of 1:1. 2. A 5 cm strip of dirt was distributed by "screen-printing" on the center of a 30 x 25 cm glass tile. 3. The tiles were baked in for 30 minutes at 200°C. Five assessments could then be carried out across each tile. At least two control

assessments were performed on each tile.

4. Five 5 cm pits were made across the tile using "<p>lasticine" strips. 6 ml of solution (0.15%) was placed in a well. Using a head covered with j-cloth and a 1.5 kg weight, the number of rubs to clean the 5 cm strip of dirt was recorded. 5. Results for the test solution were calculated as a percentage of the performance for the nearest control sample in the tile.

The results of the tests using water of 5°H are listed in the table below.

The above results clearly show how much better the products of v, according to the invention, containing respectively 5 to 50% lemon juice, are compared to the control sample when it comes to cleaning burnt eggs.

Example VI

The following compositions were compared in a standard dishwashing test for dishwashing performance as well as in a test to determine the ease of cleaning baked-on soil from substrates after soaking, using the test method described in Examples I —III.

The standard plate washing tests were carried out using the following test conditions: Product concentrations: 0.15% and 0.45% Solution temperature: 45°c

Standard sauce dirt, 5 g/plate: fat, starch, oleic and stearic acids.

The results are reproduced in the table below.

Results from the test to determine how easy it was to clean burnt-on dirt from the substrate. The grades were provided from 5 results for each product used at 0.75% concentrations.

The above results clearly show the superior properties of mixture VI according to the invention compared to mixture D according to the state of the art, both when it comes to washing dishes and performance in connection with baked-on dirt.

Examples VII-IX

The following liquid dishwashing detergent mixtures are within the scope of the invention:

Claims (3)

1. Aqueous washing-up liquid with pH 5.5-10, comprising an organic surface-active system and a citrus juice, characterized in that it essentially consists of a) 5-50% by weight of citrus juice of single strength, or an equivalent amount of a juice of multiple strength, b) 15-43% by weight of an organic synthetic surfactant system consisting of 1) 60-90% by weight, calculated on the surfactant system, of a first surfactant selected from the group consisting of water-soluble C 8-1g -alkylbenzene sulfonates and C 1-20 alkyl polyethoxy sulfates having 1-25 ethoxy groups; and 2) 10-40% by weight, calculated on the surface-active system, of another surface-active agent selected from the group consisting of C8-2Q-alkylpolyethoxysulfates with 1-25 ethoxy groups, amine oxides with one C-^Q_2g-alkyl group and two C^_4-alkyl - or -hydroxyalkyl groups, and cg_24~ alkanol- or -alkylphenol ethoxylates with 5-30 ethoxy groups, under the condition that both the surface-active agents (1) and (2) cannot be Cg_2Q<-a>alkyl polyethoxy sulfates with 1-25 ethoxy groups, the surface-active agents, if they are ion-active, are present in the form of their alkali metal salts, ammonium salts, lower alkanolamine salts or lower alkylamine salts, c) commonly used solubilizing compounds and 0-80% by weight of water. 2. Detergent mixture as stated in claim 1, characterized in that the citrus juice is present in an amount of 5-10% by weight calculated on the mixture. 3. Detergent mixture as specified in claim 1 or 2, characterized in that the pH value is 6-8.5.