WO1996020129A1

WO1996020129A1 - Modified alkali metal silicate, preparation method thereof, use thereof as non-corrosive and protective alkaline agent in detergent compositions, and detergent compositions

Info

Publication number: WO1996020129A1
Application number: PCT/FR1995/001682
Authority: WO
Inventors: Jean-Pierre Cuif; Daniel Joubert
Original assignee: Rhône-Poulenc Chimie
Priority date: 1994-12-23
Filing date: 1995-12-18
Publication date: 1996-07-04
Also published as: AU4393696A; FR2728555A1; FR2728555B1

Abstract

A modified alkali metal silicate containing calcium, magnesium, strontium or cerium ions is disclosed. A method for the preparation of said silicate, its use as a non-corrosive and protective alkaline agent in detergent compositions and detergent compositions containing said silicate are also described.

Description

MODIFIED ALCAUN METAL SIUCATE, PREPARATION METHOD THEREOF,

ITS USE AS A NON CORROSIVE ALCAUN AND

PROTECTOR IN DETERGENT COMPOSITIONS AND

THESE DETERGENT COMPOSITIONS

The present invention relates to a modified alkali metal silicate containing calcium, magnesium, strontium or cerium ions.

The invention also relates to the process for the preparation of this silicate, the use of this silicate as a non-corrosive and protective alkaline agent in detergent compositions and said detergent compositions based on said silicate.

Alkaline silicates, in particular sodium silicates, are known for their use in detergents for dishwashers. They provide a buffering effect, detergent power and dispersing action in the detergent bath.

Metasilicates (SiO / M ₂ O ratio equal to 1 where M represents an alkali metal) have been particularly used in detergents for dishwashers because of their high detergent power. However, these high alkalinity products had the disadvantage of deteriorating the surface of the glass. Consequently, after a number of washes with this detergent, a frosted appearance of the glass, colored iridescence, white streaks or a continuous whitish veil appeared on the glass. They were gradually replaced by disilicates (SiO _{_2/2} O equal to

2) which have the advantages of the alkali silicates listed above. However, even if these disilicates have a lower alkalinity than metasilicates, they still do not protect the glass sufficiently against corrosion.

In some detergents, the silicates have been replaced by sodium tripolyphosphate, which performs functions equivalent to silicates and which protects, in particular, the glass against temporary deposits, particularly deposits of calcium carbonate. However, phosphates also have the disadvantage of causing corrosion of the glass. In fact, because of their calcium complexing power, they contribute to the surface rupture of the glass network by the passage of calcium in solution, which results in corrosion of the glass. In addition, phosphates are less and less used in detergents due to environmental standards.

Thus, to date, there is no detergent composition whose alkaline or complexing agents do not corrode the glass.

An object of the present invention is therefore to solve the problem of corrosion of glass by the alkaline agents contained in the detergent compositions and to provide a detergent composition for dishwashers comprising an alkaline product which does not corrode the glass and protects it from the corrosion. For this purpose, the invention relates, first of all, to an alkali metal silicate modified with calcium, magnesium, strontium or cerium ions.

The invention also relates to the process for the preparation of said modified alkali metal silicate. The invention also relates to the use of said modified alkali metal silicate as a non-corrosive and protective alkaline agent in detergent compositions.

Finally, it relates to a detergent composition comprising said modified alkali metal silicate.

The present invention firstly relates to an alkali metal silicate with a molar ratio SiO / M ₂ O of the order of 0.5 to 4, M representing an alkali metal, characterized in that said silicate is an alkali metal silicate modified containing alkaline earth metal ions or trivalent ions A ^{n +} chosen from calcium, magnesium, strontium and cerium, n being 2 or 3, in an amount corresponding to a molar ratio A ^{n +} / MO which can range from about 0.005 to less than 0.1, preferably about 0.01 to less than 0.1.

Preferably, the alkaline earth metal ions of the modified alkali metal silicate are calcium ions Ca ²⁺ -

The alkali metal M is generally chosen from sodium, potassium and lithium. It is generally preferred to use sodium.

The modified alkali metal silicate can be in the form of an aqueous solution or in solid form. In the latter case, the modified silicate then exhibits a loss on ignition, measured at 700 ° C., of the order of 15 to 30% by weight, preferably of the order of 18 to 28%.

This modified alkali metal silicate can be obtained according to the process comprising the following steps:

- An alkali metal silicate is mixed in an aqueous solution with a Siθ2 / M ₂ O molar ratio of the order of 0.5 to 4 with a salt of alkaline earth metal or of water-soluble trivalent ion chosen from calcium, magnesium , strontium and cerium in proportions such that the molar ratio of the cation A ^{n +} solubilized from the salt / M ₂ O from the silicate is between about 0.005 and less than 0.1, preferably between about 0.01 and less 0.1, then

- The mixture obtained is heated to a temperature between about 50 and 120 ° C, preferably between 80 and 100 ° C, then

- optionally drying the product from the previous step until it has a loss on ignition, measured at 700 ° C, of the order of 15 to 30% by weight, preferably of the order of 18 to 28%. The aqueous alkali metal silicate solution has a dry extract of between about 30 and 55% by weight, preferably between about 35 and 50% by weight.

The alkaline earth metal or cerium salt can be chosen from chloride and acetate.

Preferably, the mixture of the two reactants is heated with stirring. Following said heating, the modified alkali metal silicate is obtained in liquid form.

This heating step can be followed by drying so as to obtain the modified alkali metal silicate in solid form. This drying operation can be carried out at a temperature of between approximately 50 and 120 ° C. until the modified silicate exhibits a loss on ignition, measured at 700 ° C., of the order of 15 to 30% by weight, preferably of the order of 18 to 28% by weight.

This drying can be carried out by any means such as in a rotary oven, by atomization, in an oven, etc. If necessary, the solid product obtained can be ground by known techniques until a powder of particle size suitable for the formulation detergent in which it will be incorporated. In general, the diameter of the granules is of the order of about 150 to 600 μm.

Said modified silicate can be used, and this constitutes another object of the invention, as a non-corrosive and protective alkaline agent in detergent compositions.

During said use of the modified alkali metal silicate, the detergent composition comprises of the order of 10 to 40% by weight of modified alkali metal silicate relative to the weight of the detergent composition expressed as dry matter.

Finally, the invention relates to a detergent composition for a dishwasher which does not degrade glass and tableware, comprising said modified alkali metal silicate. Indeed, such a detergent composition is particularly suitable for dishwashers because it prevents corrosion of glass and dishes and has a protective effect.

Such a composition may comprise of the order of 10 to 40% by weight of alkali metal silicate modified relative to the total weight of the composition expressed as dry matter. Besides the modified silicate according to the invention, various constituents can also be present in the detergent composition, such as: - At least one surfactant in an amount which can range from 0.5 to 10%, preferably of the order of 1 to 5%, of the weight of said composition expressed as dry matter.

Among these surfactants, there may be mentioned: anionic surfactants such as alkali metal soaps (alkaline salts of Ce fatty acids - C24). alkali sulfonates (C - C13 alkylbenzene sulfonates, C12 - Ciβ alkyl sulfonates). oxyethylenated and sulfated CQ - C16 fatty alcohols, oxyethylenated and sulfated Ce - C13 alkylphenols, alkali sulfosuccinates (C12 - C16 alkyl - sulfosuccinates) -. nonionic surfactants of the polyoxyethylenated CQ - C12 alkylphenols type, oxyethylenated aliphatic Ce - C22 alcohols, ethylene oxide - propylene oxide block copolymers, optionally polyoxyethylenated carboxylic amides,. amphoteric surfactants of the alkyldimethyl betaine type. - "builders" or agents improving the surface properties of surfactants of the type:

. organic phosphonates of the type from those of the DEQUEST® range from MONSANTO at a rate of at most 15% of the total weight of formulation expressed as dry matter, phosphates at a rate of at least 25% of the total weight of formulation expressed as dry matter,

. nitriloacetic acid up to approximately 10% of the total weight of formulation expressed as dry matter,

. citric acid, gluconic acid or tartaric acid or their salts up to approximately 50% of the total weight of formulation expressed as dry matter,

- bleaching agents of the perborate type, percarbonates associated or not with N, N, N ', N'-tetraacetylethylenediamine (TAED) or chlorine products of the chloroisocyanurate type up to approximately 30% of the total weight of said detergent composition expressed in dry matter, - anti-encrustation, anti-fog or anti-stain agents of the acrylic acid and maleic anhydride copolymer type or acrylic acid homopolymers in an amount which can range up to approximately 10% of the total weight of said detergent composition expressed as dry matter,

- fillers of the sodium sulfate type for detergents in powder in an amount which can range up to 50% of the total weight of said composition expressed as dry matter. The following examples illustrate the invention without, however, limiting its scope.

EXAMPLES

Description of the glass corrosion test

This simplified glass corrosion test reproduces certain washing machine washing conditions, in particular the soaking, rinsing and drying cycles. The glass used is made up of microscopy slides measuring 2.5 × 7.5 cm.

This glass has the following chemical composition by weight:

If: 21-43% Ca: 2.8-5.8% Mg: 1.6-3.4%

Na: 6.8-14.2% Al: 0.3-0.7%

The slide is half immersed and slightly tilted in 80 ml of aqueous washing solution at room temperature containing 5 g / l, expressed as dry, of dissolved product, the more or less corrosive effect of which is to be tested.

If the product is initially solid, the slide is not introduced into the solution until the product is completely dissolved.

The container containing the half-submerged blade is then closed, then placed in an oven at 60 ° C for 3 weeks. Three times a week, the slide is removed from the container, rinsed thoroughly with deionized water, then wiped with paper and re-immersed in the solution, the volume of which has been adjusted in the event that evaporation has occurred.

At the end of the three weeks, the slide is weighed after cooling to room temperature and the change in mass is calculated. The blade is observed and the presence or absence of the following forms of corrosion is noted: iridescence, haze, streaks or frosted.

Finally, the pH of the solutions is measured at room temperature before immersion of the slide and at the end of the experiment. Comparative example 1.

Three solutions at 5 g / l of dry product of the following sodium disilicates are prepared: Product 1: disilicate in aqueous solution of SiO / Na ₂ O ratio = 2.1 containing 55% water by weight

Product 2: disilicate atomized to 20% water by weight

Product 3: disilicate dried in an oven at 80 ° C in a thin layer of 5 mm, containing

27% water by weight.

Results

The glass corrosion test described above is carried out, the results are as follows:

Table 1

Product initial pH final pH Δ mass Observations

1 11, 6 11, 3 -2.1 mg opaque haze

2 11, 5 11.3 -1.6 mg opaque veil, iridescence

3 11, 6 11, 3 -1.8 mg light haze, iridescence

It can be seen that for these three prior art silicates, the glass has undergone corrosion clearly visible to the naked eye and a loss of mass.

Example 2.

Preparation of a modified silicate of Ca2 + / Na O ratio = 0.01

A disilicate solution (reference 1 of Example 1) is mixed with a 73.4 g / i solution of calcium chloride of formula: CaCl, 2 H ₂ O so that the Ca ²⁺ / Na ₂ ratio O is equal to 0.01 while stirring using a paddle stirrer.

The two solutions are left to react for 30 min at 80 ° C. Then the solution is dried in a thin layer in an oven at 60 ° C until the final water content is equal to 26% by weight measured by loss on ignition at 700 ° C. The product is then finely ground to an idameter of 200 μm. We obtain the product referenced 4. Preparation of a modified silicate with a Caï Na O ratio ≈ 0.05

A disilicate solution (reference 1 of Example 1) is mixed with a 73.4 g solution of calcium chloride of formula: CaCl, 2 H ₂ O so that the Ca ²⁺ / Na O ratio is equal at 0.05.

Then we proceed as before. Obtained the product referenced 5 having a final water content of 27.5% by weight measured by loss on ignition at 700 ° C.

Preparation of a modified rannort silicate _.__- + IHΆ_Q = 0.1

A disilicate solution (reference 1 of Example 1) is mixed with a 73.4 g / l solution of calcium chloride of formula: CaCl ₂ , 2 H ₂ O so that the Ca ²⁺ / Na ratio ₂ O is equal to 0.1.

Then we proceed as before. We obtain the product referenced 6 having a final water content of 27.5% by weight measured by loss on ignition at 700 ° C.

Corrosion test of modified silicates 4. 5 and 6

The glass corrosion test described in Example 1 is carried out, the results are as follows:

Table 2

Product initial pH final pH Δ mass Observations

4 11, 6 11, 3 -0.2 mg no visible corrosion

5 11.5 11.2 -0.2 mq no visible corrosion

6 11.6 11.3 -3.8 mg very light haze, iridescence

It therefore appears that a small amount of calcium in the silicate has sufficiently modified the structure of the silicate to prevent its corrosion of the glass, a property which the disilicates of the prior art do not exhibit.

Claims

1. An alkali metal silicate with a Siθ2 / M ₂ O molar ratio of the order of 0.5 to 4, M representing an alkali metal, characterized in that said silicate is a modified alkali metal silicate containing alkali metal ions -terreous or trivalent ions A ^{n +} chosen from calcium, magnesium, strontium and cerium, n being 2 or 3, in an amount corresponding to a molar ratio A ^{n +} / M ₂ O which may range from approximately 0.005 to less than 0.1, preferably from about 0.01 to less than 0.1.

2. Silicate according to claim 1 characterized in that the alkaline earth metal ions are calcium ions Ca ²⁺ .

3. Silicate according to claim 1 or 2 characterized in that it has a loss on ignition, measured at 700 ° C, of the order of 15 to 30% by weight, preferably of the order of 18 to 28% .

4. Process for the preparation of the modified alkali metal silicate forming the subject of one of claims 1 to 3, characterized in that it comprises the following steps:

an alkali metal silicate is mixed in an aqueous solution with a SiO ₂ / M ₂ O molar ratio of the order of 0.5 to 4 with an alkaline earth metal salt or of a water-soluble trivalent ion chosen from calcium, magnesium, strontium and cerium in proportions such that the molar ratio of the cation A ^{n +} solubilized from the salt / MO from the silicate is between about 0.005 and less than 0.1, preferably between about 0.01 and less 0.1 then

- The mixture obtained is heated to a temperature between about 50 and 120 ° C, preferably between about 80 and 100 ° C, then

- optionally drying the product from the previous step until it has a loss on ignition, measured at 700 ° C, of the order of 15 to 30% by weight, preferably of the order of 18 to 28%.

5. Use of a modified alkali metal silicate which is the subject of one of claims 1 to 3 or which can be obtained by the process which is the subject of claim 4, in a detergent composition as an agent non-corrosive and protective alkaline.

6. Use according to claim 5 characterized in that the detergent composition comprises of the order of 10 to 40% by weight of alkali metal silicate modified relative to the weight of the detergent composition expressed as dry matter.

7. A detergent composition for a dishwasher that does not degrade glass and dishes comprising a modified alkali metal silicate which is the subject of one of claims 1 to 3 or capable of being obtained by the process of claim 4.

8. Detergent composition according to claim 7 characterized in that it comprises of the order of 10 to 40% by weight of alkali metal silicate modified relative to the weight of the detergent composition expressed as dry matter.