EP0087035B1

EP0087035B1 - Zeolite-containing detergent compositions and process for preparing same

Info

Publication number: EP0087035B1
Application number: EP83101103A
Authority: EP
Inventors: Anthony Joseph Gioffre; Albert Saunders Behan
Original assignee: Union Carbide Corp
Current assignee: Union Carbide Corp
Priority date: 1982-02-08
Filing date: 1983-02-05
Publication date: 1985-09-11
Also published as: ATE15500T1; JPS6049680B2; DE3360741D1; EP0087035A1; JPS58145796A

Abstract

Spray-dried detergent compo9itions prepared by spray-drying aqueous slurries comprising high concentrations of alkali metal silicates in combination with aluminosilicate particles which have been coated with from 100 ppm to 2000 ppm of a cationic surfactant contain fewer large aggregates which can deposit on washed fabrics as floc than is the case when the aluminosilicate is not so coated. The improvement is believed to result from an inhibition of the bridging of aluminosilicate particles by silicic acid.

Description

Background of the Invention

This invention relates in general to granular detergent compositions which comprise as essential ingredients an alkali metal silicate, a water-insoluble aluminosilicate and a cationic surfactant. More particularly it relates to spray-dried detergent compositions containing the aforesaid essential ingredients wherein the aluminosilicate particles are coated with the cationic surfactant in an amount of at least 50 ppm (wt.) at least prior to being subjected to the elevated temperatures and CO₂-containing environment of the spray dryer, and preferably prior to being brought into contact with an aqueous solution of the alkali metal silicate.
Because of the suspected eutrophication properties attributed to phosphate builders in detergent compositions such as those used for laundering fabrics, it has become conventional in the art to substitute for some or all of the phosphate formerly employed, a water-insoluble aluminosilicate which can be either amorphous or crystalline. Another necessary component of such detergents is an alkali-metal silicate, such as sodium silicate. These compounds are found to minimize the corrosion of washing machine surfaces attributed to the other detergent components. In addition it has been proposed that alkali metal silicates are desirable components in spray-dried detergent granules in that they aid in crutcher mix processing and also aid in maintaining crisp free-falling granules.
It is further known, however, that there are difficulties attendant the use of both aluminosilicates and alkali metal silicates in the same detergent composition. As reported in US-A-4,019,999 issued April 26, 1977 to T. H. Ohren et al these two constituents have a pronounced tendency to aggregate through bridging of the aluminosilicate particles. In aqueous slurry a chemical reaction takes place which can be theorized as involving ≡Si―OH and/or ≡SiO^- groups of the aluminosilicate and the alkali metal silicate which can condense to form Si-O-Si linkages and result in the aggregation by bridging. The aggregates then fail to disperse in the washing medium and deposit on the fabric as a white floc which is particularly evident on dark fabrics.
It has been proposed to avoid the deposition problem by limiting the amount of sodium silicate to less than about 3% by weight based on the overall weight of the detergent compositions containing from 5 to 95 weight per cent aluminosilicate. This solution is disclosed in US-A-3,985,669 issued October 12,1976 to Krummel et al. The sodium silicate is employed in the form of a solid particle: A third essential ingredient is a water-soluble surface-active agent selected from the group consisting of anionic, nonionic, ampholytic and zwitterionic surfactants. It would be desirable, however, to be able to utilize greater concentrations of alkali metal silicates and/or aqueous solutions of alkali metal silicates in preparing detergent compositions.
It is therefore the general object of the present invention to provide a detergent composition suitable for spray-drying which contains an aqueous solution of alkali metal silicate in conjunction with an aluminosilicate builder, and which is highly dispersible in water even after spray-drying so that floc deposition on fabrics is ameliorated.

Summary of the Invention

A spray-dried detergent composition comprising an alkali metal silicate and an aluminosilicate ion- exchanger prepared by spray drying a precursor composition containing aqueous alkali metal silicate solution and a cationic surfactant-coated aluminosilicate. The cationic surfactant is found to inhibit the tendency of the alkali metal silicate or derivatives thereof formed during spray drying to react with the aluminosilicate particle and create non-dispersable floc aggregates.

The Present Invention

The spray-dried detergent composition of this invention thus comprises an organic surfactant, a crystalline aluminosilicate and an alkali metal silicate, and is characterized in that the aqueous slurry composition to be spray-dried comprises:

(a) 0 to 30% by weight of one or more organic surfactants:
(b) 10 to 90% by weight of a builder system consisting of
- (1) 1 to 90 parts by weight of an aluminosilicate having as a coating on the particles thereof from 50 to 2000 ppm by weight of a cationic surfactant, said aluminosilicate being
  - a crystalline aluminosilicate zeolite having the general formula M_x[(AlO₂)_x (SiO₂)_y]z H₂O wherein x and y are integers, the molar ratio of x to y being in the range of 0.1 to 1.1 and z is an integer from 8 to 264 and/or an amorphous hydrated aluminosilicate having the empirical formula Mz(zAI02. Si0₂) wherein M is sodium, potassium, ammonium or substituted ammonium, z is from 0.5 to 2, said material having a magnesium ion-exchange capacity of at least 50 milligrams of CaC0₃ hardness per gram of anhydrous aluminosilicate: and
- (2) 4 to 35 parts by weight of a water soluble alkali metal silicate having a molar composition equivalent to 1.0 to 4.0 moles of Si0₂ per mole of Na₂0, said alkali metal silicate being in the form of an aqueous solution having a solids content of from 20 to 60 weight per cent.

From presently available test data it appears that significant improvement in the inhibiting aggregation due to aluminosilicate bridging is obtained when as little as 100 ppm (wt.) of the cationic surfactant is coated on the aluminosilicate particles. It appears that with coatings constituting more than 2000 ppm (wt), no further improvement is obtained, and in fact some decrease in effectiveness results compared with the effectiveness of lesser amounts. Accordingly it is preferred that the aluminosilicate composites contain a coating of from 100 ppm to 2000 ppm by weight based on the anhydrous weight of the aluminosilicate.
The aluminosilicate components used in the present invention are any of synthetic or naturally occurring zeolites heretofore proposed for use in detergent compositions such as (1) crystalline aluminosilicate zeolites having the general formula:
wherein x and y are integers, preferably having a value of at least 6; the molar ratio of x to y is in the range of 0.1 to 1.1; and z is an integer from 8 to 264, preferably a value such that in the spray-dried detergent product containing same, the zeolite contains from 10 to 30 weight-% adsorbed water, and M is preferably sodium but can also be potassium, ammonium or substituted ammonium; or (2) amorphous hydrated aluminosilicate material of the empirical formula
wherein M is sodium, potassium, ammonium or substituted ammonium, z is from 0.5 to 2, and said material has a magnesium ion exchange capacity of at least 50 milligrams of CaC0₃ hardness per gram of anhydrous aluminosilicate; or (3) mixtures thereof. Mixture of zeolite A and zeolite X wherein either zeolite constitutes at least 30 weight per cent of the overall zeolite mixture and the other zeolite constitutes a complementary amount, are especially preferred as the aluminosilicate constituent.
The cationic surfactant is preferably any of the quaternary ammonium compounds having the formula
wherein at least one, but not more than two, of the R- groups is an organic radical containing a group selected from C_a-C₂₂ aliphatic radical, or an alkyl phenyl or alkylbenzyl radical having 10 to 16 carbon atoms in the alkyl chain, the remaining group or groups being selected from C,-C₄ alkyl, C₂-C₄ hydroxy alkyl, and cyclic structures in which the nitrogen atom forms part of the ring, Y constituting an anionic radical selected from the group consisting of hydroxide, halide, sulfate, methylsulfate, ethylsulfate and phosphate ions.
The alkali metal silicates employed in preparing the present detergent compositions are preferably sodium silicates with 1.0 to 4.0 moles of Si0₂ per mole of Na₂0. Equivalent potassium and lithium silicates are also useful. The alkali metal silicates are preferably employed in the form of concentrated aqueous solutions containing from 20 to 60% solids, but hydrated and anhydrous silicate powders can be imparted to the overall detergent composition along with an appropriate amount of water if desired.
It is an important aspect of this invention that the aluminosilicate constituent be coated with the cationic surfactant, or a portion thereof, before there is contact of the aluminosilicate with the alkali metal silicate under conditions which permit significant reaction between these two materials. Advantageously, and preferably, the aluminosilicate is coated with from 100 ppm to 2000 ppm of the cationic surfactant before any contact with an aqueous sodium silicate solution is allowed, i.e. the aluminosilicate-cationic surfactant composite is imparted to the crutcher as an already prepared material. In all events the aluminosilicate must contain the cationic surfactant coating before the overall detergent composition is subjected to spray-drying.
While not wishing to be bound by any particular theory, it is believed that the principal cause of bridging of the aluminosilicate particles to form undesirable aggregates is a condensation reaction between silicic acid and/or terminal silanol groups on polymerized silicic species and =Si-OH groups of the aluminosilicate. While relatively small amounts of silicic acid are present in the alkali metal silicate solution employed, there is apparently enough to cause appreciable floc formation even at ambient room temperatures during prolonged periods.
In the spray-dryer, however, the detergent feed containing relatively large amounts of water is contacted at elevated temperatures, i.e., 260°C to 482°C, by a rather high concentration of carbon dioxide. This permits the formation of HZC03 which then can react with the alkali metal silicate to produce silicic acid in accordance with the following equation:
The silicic acid in turn bonds to aluminosilicate (zeolite) surfaces by the following equation:
of course monomeric silicic acid is not the only active species, and polymerized silica can also be considered to be a reaction bonding agent.
The cationic surfactant coating on the aluminosilicate interferes with this or similar bonding reactions without inhibiting appreciably the ion exchange activity of the aluminosilicate when the detergent is added to the washing medium.
The method of coating the aluminosilicate with the surfactant is not a critical factor. Ordinarily the aluminosilicate is simply slurried or otherwise washed with a solution of the surfactant in a suitable solvent such as water or a mixture of water and polar organic solvent such as isopropanol.
There is a considerable attraction between the cationic surfactant and the anionic aluminosilicate, and accordingly other types of surfactants, builders and other traditional detergent ingredients can be included in the present compositions without loss of the benefits obtained using the three essential ingredients alone. The compositions, properties and preparation of other organic surfactants are well represented in the patent literature and a detailed review of such readily available material will not be undertaken here. We hereinafter disclose examples of certain classes of and individual surfactants that can be used in the detergents of our invention. It is not intended that the scope of our invention be limited to these specific materials, but that equivalent materials also be included.
Anionic surfactants are particularly important in the detergent compositions of our invention. Such anionic materials include, among others, alkali metal soaps of fatty acids, alkali metal salts of alkyl sulfuric acid reaction products, sodium alkyl glyceryl ether sulfonates, succinamates and anionic phosphates, one of the most commonly used anionic surfactants is the sodium salt of linear alkyl benzene sulfonate (LAS) wherein the alkyl group contains more than 10 carbon atoms. LAS forms at least a part of many of the surfactant systems used in our detergent compounds and may be the only surfactant used.
Nonionic surfactants are also useful and include, among others, polyethylene oxide condensate of alkyl phenols, condensation products of aliphatic alcohols with ethylene oxide, nonyl phenol-ethylene oxide condensates, amine oxides and posphine oxides.
Ampholytic surfactants such as the aliphatic derivatives of heterocyclic secondary and tertiary amines and zwitterionic surfactants such as derivatives of aliphatic quaternary ammonium compounds are also useful.
Although sufficient aluminosilicate-cationic surfactant composite builder and alkali metal silicate can be used to accommodate any laundering environment it may be desired to include an auxiliary builder in the detergent compositions of our invention. Such auxiliary builders include salts of phosphates, pyrophosphates, orthophosphates, polyphosphates, phosphonates, carbonates, and polyhydroxysulfonates, organic sequestering agents such as polyacetates, carboxylates, polyaminocarboxylates and polyhydroxysulfonates are of use in our detergent compositions. Specific examples of useful materials include sodium and potassium salts of tripolyphosphate, pyrophosphate, hexametaphosphate, ethylene- diaminotetraacetic acid, nitrilotriacetic acid, citric acid, citric acid isomers and others.
The present detergents can also include numerous additional detergent ingredients. Antirediposition agents such as sodium carboxymethyl cellulose prevent certain types of soils from redipositioning on clean fabric. Minor detergent ingredients such as enzymes, optical brighteners and bleaches are included to remove stains and/or improve the appearance of the fabric. Other minor detergent ingredients such as perfumes, anti-caking agents, dyes, coloured specks and fabric softeners are added to improve the properties or appearance of the detergent or the fabric. Since detergent actives are effective at low concentrations, it is important the bulking agents be added to the formulation so that measurement of the appropriate dose is facilitated. We have found bulking agents such as sodium sulfates, sodium chloride and other neutral alkali metal salts to be effective.

Example 1

In order to demonstrate the effectiveness of cationic surfactant-treated zeolite particles in promoting the dispersability of a spray-dried detergent containing high levels of sodium silicate and zeolite particles, two spray-dried detergents were prepared in which the only significant difference was in the zeolite constituent. In one sample (A) the zeolite particles were coated with 500 ppm of a cationic quaternary ammonium (alkyltrimethylammonium chloride in which the primary alkyl group contains from 14 to 18 carbon atoms. In sample B, the zeolite was untreated. The composition contained:
Both samples were subjected to a dissolution screen analysis procedure which utilized a tergotometer, a R.O. Tap Testing Sieve shaker, a series of seven U.S. standard sieves (Nos. 30, 40, 50, 70, 100, 200 and 325, plus top and bottom), a drying oven, a 26 cm diameter Buchner funnel, a 8.9 cm diameter Buchner funnel, a 2 liter vacuum flask, a 4 liter Erlemeyer flask, Whatman® No. 1 filter paper and an aspirator. The analysis procedure was as follows:

(a) The clean sieve series plus sieve bottom and 8.9 cm Buchner funnel (with filter paper) were dried in a 100° C oven, cooled to room temperature, and weighed.
(b) One liter of a solution of hardness water (150 ppm, Ca++/Mg++ = 3/2) was heated to 50° C in the tergotometer.
(c) Twenty-five grams of the detergent sample to be tested was added to the hardness water in the tergotometer and the contents agitated for 10 minutes at 100 RPM min.
(d) A "sieve tower" is prepared from the sieve series and set into the 26 cm diameter Buchner funnel, which is inserted into the four liter Erlemeyer flask.
(e) The contents of the tergotometer were emptied into the sieve tower. Particles clinging to the tergotometer tub were rinsed out with distilled water and added to the same tower.
(f) When it was observed that water was no longer dripping from the sieve tower, the bottom was placed on the tower and the entire apparatus placed in a 100° C drying oven for twenty-two hours.
(g) The collected liquid fraction was filtered with the aid of vacuum using the weighed 8.9 cm Buchner funnel and Whatman^O No. 1 filter paper.
(h) The 8.9 cm Buchner funnel with filtered contents was placed in a 100° C drying oven for twenty-two hours.
(i) After drying the sieve top was placed on the sieve tower and along with the Buchner funnel was allowed to cool to room temperature.
(j) The sieve tower was placed in the R.O. Tap Testing Sieve Shaker for three minutes.
(k) Each sieve plus bottom and Buchner funnel was weighed and any increase in weight noted.
(I) The total solids recovered plus the percentage of solids on each sieve were recorded. The percentage of solids collected on the sieve bottom and the filter were combined to represent the fine fraction.

Screen analysis of the starting samples showed that the median particle size of Sample A was 360 micrometers, and for Sample B the median particle size was 345 micrometers. The results of the dissolution screen analysis procedure showed that detergent Sample A (containing the surfactant coated zeolite) dispersed to the degree that the median particle size was less than 44 micrometers, whereas the comparison Sample B (contained untreated zeolite particles), the dispersion was such that the median particle size was 120 micrometers.

Claims

1. A spray-dried detergent composition comprising an organic surfactant, crystalline aluminosilicate and an alkali metal silicate, characterized in that the aqueous slurry composition to be spray-dried comprises:

(a) 0 to 30% by weight of one or more organic surfactants;

(b) 10 to 90% by weight of a builder system consisting of

(1) 1 to 90 parts by weight of an aluminosilicate having as a coating on the particles thereof a cationic surfactant, in an amount of from 50 to 2000 ppm by weight, said aluminosilicate being

a crystalline aluminosilicate zeolite having the general formula M_x[(AlO₂)_x SiO₂)_y]_z H₂O wherein x and y are integers, the molar ratio of x to y being in the range of 0.1 to 1.1, and z is an integer from 8 to 264; and/or an amorphous hydrated aluminosilicate having the empirical formula M_z(zAlO₂ . SiO₂) wherein M is sodium, potassium, ammonium or substituted ammonium, z is from 0.5 to 2, said material having a magnesium ion-exchange capacity of at least 50 milligrams of CaC0₃ hardness per gram of anhydrous aluminosilicate;

(2) 4 to 35 parts by weight of a water soluble alkali metal silicate having a molar composition equivalent to 1.0 to 4.0 moles of Si0₂ per mole of Na₂0, said alkali metal silicate being in the form of an aqueous solution having a solids content of from 20 to 60 weight per cent.

2. Detergent composition according to claim 1 wherein the aluminosilicate is a crystalline zeolitic molecular sieve.

3. Detergent composition according to claim 2 wherein the cationic surfactant is a quaternary ammonium compound having the general formula

wherein at least one, but not more than two, of the R-groups is an organic radical containing a group selected from C₈―C₂₂ aliphatic radical, or an alkyl phenyl or alkylbenzyl radical having 10 to 16 carbon atoms in the alkyl chain, the remaining group or groups being selected from C_l-C₄ alkyl, C₂-C₄ hydroxy alkyl, and cyclic structures in which the nitrogen atom forms part of the ring, Y constituting an anionic radical selected from the group consisting of hydroxide, halide, sulfate, methylsulfate, ethylsulfate and phosphate ions.

4. Detergent composition according to claim 3 wherein the quaternary ammonium cationic surfactant is an alkyltrimethylammonium, chloride wherein the alkyl group contains from 14 to 18 carbon atoms.

5. Detergent composition according to claim 3 wherein the aluminosilicate is zeolite A and the alkali metal silicate is sodium silicate.