GB2143251A - Machine dishwashing detergent compositions - Google Patents

Abstract

A detergent composition suitable for washing dishes in a washing machine comprises trichloroisocyanuric acid coated with paraffin wax at a concentration of from 1 to 10% by weight of the acid, preferably having a melting point lower than 60 DEG C.

Description

SPECIFICATION Detergent compositions The present invention relates to new detergent compositions suitable for washing dishes in a washing machine, and a process for preparing them.

The washing of dishes in a machine involves both the detergent action of the washing agent and the mechanical action of water. Apart from its detergent action, the washing agent must also have a disinfectant capacity and water-softening properties. The washing agent must therefore possess strong detergence but also its composition must be such that it does not cause the formation of foams which are harmful to the mechanical action of water.This is why the washing agent compositions consist in a known manner of: a softening agent, generally chosen from the class of polyphosphates. (Among the polyphosphates used, mention can be made of sodium tripolyphosphate, sodium hexametaphosphate and sodium pyrophosphate, as well as the corresponding potassium polyphosphates); -an alkalinity-producing agent mainly consisting of a sodium metasilicate in its anhydrous form or in its pentahydrate form. (In a known manner sodium silicate may be partly replaced by sodium carbonate, sodium sulphate, or sodium hydroxide); -a non-foaming surface-active agent of the non-ionic type, chosen from the following classes of products: ethoxylated linear alcohols, condensate of ethylene oxide with propylene oxide, alkoxy amines, polyethoxyethers of fatty alcohols, ethoxylated alkylphenols, or phosphoric esters of fatty alcohols. (Preferably, for reasons of effectiveness, biodegradability and cost, a surfaceactive agent is chosen from the class of ethoxylated linear alcohols); and -a disinfectant.

The disinfectant used, which releases active chlorine, is generally a solid chlorine-based product of the chloroisocyanurate derivative type. This is most frequently a sodium or potassium salt of dichloroisocyanuric acid.

Until the present time, the following were used in practice: anhydrous sodium dichloroisocyanurate titrating at 63% of active chlorine, a sodium dichloroisocyanurate dihydrate titrating at 56% of active chlorine, anhydrous potassium dichloroisocyanurate titrating at 59% of active chlorine, potassium dichloroisocyanurate monohydrate titrating at 56% of active chlorine or calcium dichloroisocyanurate tetrahydrate titrating at 56% of active chlorine. The active chlorine is defined as being the oxidising capacity due to the positive chlorine.To understand better to what positive chlorine corresponds it should be recalled that chlorine present in the chlorinated derivatives described above is bound to a nitrogen atom and is present therein in the oxidation state + 1, that is to say Cl + During the oxidation-reduction process a Cl + ion combines with two electrons to be converted into the Cl- (chloride) state. Two equivalents of an oxidising agent are released, which correspond to 71 g of elementary chlorine although the atomic weight is only 35.5. This also means that an atom of Cl+ has the same oxidising capacity as a molecule of elementary chlorine Cl2.

Amongst the other chlorinated disinfectants of the chloroisocyanurate family, there is one which titrates at approximately 91% of active chlorine: trichloroisocyanuric acid. It would therefore be advantageous to be able to use it, given its high percentage of active chlorine.

Unfortunately, until the present time it could not be used, as it was too reactive towards the other components of the washing agent compositions, in particular towards the surface-active agents. Washing agents containing trichloroisocyanuric acid are unstable in storage and they lose significant quantities both of chlorine and of surface-active agents through mutual destruction.

A means of stabilising trichloroisocyanuric acid has now been found, in particular of stabilising it for manufacturing washing agent compositions which are stable in storage and suitable for washing dishes in a washing machine.

The present invention relates to a new stable washing agent composition suitable for washing dishes in a washing machine, containing a softening agent chosen from the polyphosphates, an alkalinity-producing agent chosen from the sodium silicates, a nonionic surface-active agent and a chloroisocyanurate derivative, characterised in that the chloroisocyanurate derivative used is trichloroisocyanuric acid coated with the aid of a paraffin wax employed in a concentration of 1 to 10% by weight relative to the weight of the acid.

It has been found that paraffin waxes were compatible with trichloroisocyanuric acid.

Moreover, when used in relatively small amounts, they make it possible to produce good stabilisation of the acid. Furthermore, they are dispersible under the washing conditions, that it to say in aqueous media at a temperature of 50 to 60"C.

The paraffin waxes consist of a mixture of solid hydrocarbons with a high molecular weight (for example C36H74) which have a melting point below 60"C and above 40"C, and a viscosity at 1 00 C below 6 centipoises. They are employed in a concentration of 1 to 10% by weight relative to the trichloroisocyanuric acid, preferably in a concentration of 3 to 5% by weight.

Above 5% difficulties appear in carrying out the coating and it is necessary to modify the conditions in order to obtain a suitable coating. The use of quantities greater than 10% does not produce an appreciable improvement in the storage stability of the washing agent compositions.

The use of quantities below 1% results in too poor a stabilisation of the acid.

The washing agent compositions which are the subject of the invention are manufactured by first carrying out the coating of the trichloroisocyanuric acid with the aid of paraffin waxes. This coating is carried out in any kind of industrial mixer, such as a drum mixer, preferably a mixer fitted with a heating device. It is also possible to employ a rotary mixer of the concrete-mixer type in which the molten wax is sprayed on the acid heated to a temperature in the region of 50"C. The temperature of use permits good distribution of the paraffin waxes, which solidify on cooling. The wax-coated trichloroisocyanuric acid is then mixed in another mixer with the other components of the washing agent.

The quantities of the various components other than the paraffin employed for the manufacture of the new washing agent compositions which are the subject of the invention are employed in conventional weight ratios. The softening agent chosen from the polyphosphates is employed in a concentration of 25 to 60% by weight and preferably 40 to 50% by weight relative to the weight of the composition.

The alkalinity-producing agent chosen from the sodium silicates is employed in a concentration of 30 to 70% by weight and preferably 40 to 60% by weight relative to the weight of the composition. In a known manner, sodium silicate may be partly replaced with sodium carbonate, sodium sulphate or sodium hydroxide. The nonionic surface-active agent is employed in a concentration of 0.5 to 4% by weight and preferably in a concentration of 1 to 3% by weight relative to the weight of the composition. The trichloroisocyanuric acid coated with the aid of paraffin waxes is employed in a concentration of 0.5 to 5% by weight and preferably 1 to 3% by weight relative to the weight of the composition.

The following examples illustrate the present invention.

EXAMPLE 1 Trichloroisocyanuric acid is first stabilised with the aid of paraffin waxes in the following manner: The acid is heated to a temperature of 50"C and is then placed in a pill-coater. While the coater rotates, paraffin waxes are sprayed from above by means of a spray-gun. The temperature of use permits a good distribution of the waxes, which solidify on cooling. The paraffin waxes employed have a melting point below 60"C and a viscosity at 1 00 C of less than 6 centistokes.

Various mixtures of acid and waxes are produced by using varying percentages of paraffin waxes. The mixtures obtained in this way are employed for the manufacture of washing agent compositions.

Washing agents having the following composition are prepared (parts are expressed in parts by weight): sodium tripolyphosphate: 50 parts, sodium metasilicate (anhydrous or 5H20 hydrate): 50 parts, -PLURAFAC RA 43 (ethoxylated nonionic surface-active agent manufactured by the company PCUK): 2 parts, -trichloroisocyanuric acid coated with paraffin waxes: 2 parts.

A premix of sodium tripolyphosphate and nonionic surface-active agent is first made in a mixer of a rotary type. A homogeneous mixture is obtained after 20 minutes. The metasilicate is then added to the mixer. After 20 minutes the coated trichloroisocyanuric acid is added. The whole composition is then left in the rotating mixer for 20 minutes. The percentage of chlorine determined by iodometry in the washing agent composition is then 1.65%.

The washing agent composition prepared in this way is placed in plastic bags closed with a non-hermetic closure. The bags are stored in a controlled environment oven under the following conditions: -temperature: 40"C, relative humidity: 80%.

Samples are withdrawn after a storage period of between 1 and 3 months and the residual chlorine is determined by iodometry. Table 1 shows the results obtained after 50 days' storage for washing agent compositions prepared from anhydrous sodium metasilicate and from trichloroisocyanuric acid coated with the aid of paraffin waxes employed in various percentages (by weight). The results relating to the remaining chlorine are expressed as percentages relative to the original chlorine.

TABLE 1 TRICHLOROISO- Washing agent CYANURIC ACID composition Z of remaining chlorine Not coated with paraffin waxes 39 Coated with 5X of paraffin waxes having a melting point of 50-520C 81 Coated with 5% of paraffin waxes having a melting point of 40-420C 78 Coated with 5X of paraffin waxes having a melting point of 58-600C 68.5 EXAMPLE 2 Example 1 is repeated but using sodium metasilicate pentahydrate, instead of the anhydrous metasilicate as in Example 1, for the preparation of the washing agent compositions. Table 2 collates the results obtained.

TABLE 2 Trichloroiso- Washing agent cyanuric acid composition X of remaining chlorine Not coated with paraffin waxes 14 Coated with 5% of paraffin waxes having a melting point of 50-52 C 38.5 Coated with 5X of paraffin waxes having a melting point of 40-420C 26.5 Coated with 5X of paraffin waxes having a melting point of 58-600C 30 EXAMPLE 3 Examples 1 and 2 are repeated using paraffin waxes having a melting point of 40-42"C.

Samples are withdrawn after a storage period of 80 days. Table 3 shows the results obtained for washing agent compositions prepared either from anhydrous sodium metasilicate or from sodium metasilicate pentahydrate.

TABLE X of remaining chlorine Trichloroiso- Washing agent prepared mashing agent cyanuric acid from anhydrous sodium prepared from metasi licate sodium meta silicate pentahydrate Uncoated acid 20 10 Acid coated with 1% of waxes 30 15 Acid coated with 2X of waxes 60 25 Acid coated with 5Z of waxes 78 26.5 Acid coated with 10% of waxes 78 27

Claims (10)

1. A detergent composition containing a chloroisocyanurate derivative suitable for washing dishes in a washing machine and also containing a softening agent chosen from the polyphosphates, an alkalinity-producing agent consisting at least partially of sodium silicates and a surface-active agent, characterised in that the chloroisocyanurate derivative employed is trichloroisocyanuric acid coated with the aid of a paraffin wax having a melting point below 60 and used in a concentration of 1 to 10% by weight of the acid.

2. A composition according to claim 1, characterised in that the quantity of paraffin wax employed is 3 to 5% by weight relative to the acid.

3. A process for preparing a composition according to claim 1 or 2, characterised in that the trichloroisocyanuric acid is coated with the aid of paraffin wax before being mixed with the other components of the washing agent.

4. A process according to claim 3, characterised in that the molten wax is sprayed on the trichloroisocyanuric acid heated at 50'C.

5. A detergent composition containing trichloroisocyanuric acid coated with a paraffin wax.

6. A composition as claimed in claim 5, comprising from 1 to 10% by weight of the acid.

7. Trichloroisocyanuric acid coated with a paraffin wax.

8. The composition of claim 7, wherein the wax has a melting point less than 60do.

9. A detergent composition substantially as hereinbefore described with reference to the foregoing Examples.

10. A method of preparing a detergent composition, substantially as hereinbefore described.