EP0290209A1

EP0290209A1 - Spray-dried material for detergent compositions

Info

Publication number: EP0290209A1
Application number: EP88303910A
Authority: EP
Inventors: Michael Dr Hull; Peter Cory Dr Knight; Andrew William Travill
Original assignee: Unilever PLC; Unilever NV
Current assignee: Unilever PLC; Unilever NV
Priority date: 1987-04-30
Filing date: 1988-04-29
Publication date: 1988-11-09
Also published as: GB8710293D0; ZA883077B; AU600123B2; AU1515888A; TR25690A; BR8802053A

Abstract

A porous spray-dried material suitable for carrying mobile ingredients in a detergent composition consists of

(i) from 90 to 100% by weight of sodium tripolyphosphate and sodium carbonate in a weight ratio of from 0.1:1 to 1.5:1; and
(ii) from 0 to 10% by weight of other ingredients, for example, sodium silicate, anionic and/or nonionic surfactant, polymer.

The material may be used for carrying liquid nonionic surfactants in detergent compositions.

Description

TECHNICAL FIELD OF INVENTION

The present invention relates to a material prepared by spray-drying which is suitable for use as a carrier for mobile ingredients, for example, liquid nonionic surfactants, in detergent and cleaning compositions. The carrier material of the invention consists essentially of sodium tripolyphosphate and sodium carbonate.

BACKGROUND AND PRIOR ART

It is difficult to spray-dry crutcher slurries containing high levels of nonionic surfactants as they tend to autoxidise. Powders with poor flow properties also result. Furthermore, some nonionic surfactants volatilise to an unacceptable degree in the spray-drying tower and produce emissions ("blue smoke") which are environmentally objectionable. It has therefore been proposed to incorporate nonionic surfactants in detergent powders by spraying a liquid, liquefied or dissolved nonionic surfactant onto a carrier material which may itself be a detergent base powder containing most or all of the other desired ingredients of the composition, or which may be a wholly or predominantly inorganic carrier material that can subsequently be dry-mixed or granulated with other desired ingredients to form a detergent composition. Similar methods are used to incorporate other mobile liquid ingredients, for example, lather suppressors, in detergent powders.
GB 1 579 261 (Colgate-Palmolive Co.) discloses spray-dried base beads comprising, by weight, 7% sodium silicate, 78% sodium tripolyphosphate, and 15% sodium carbonate; CA 978 821 (Colgate-Palmolive Co.) discloses spray-dried base beads comprising, by weight, 13% sodium silicate, 42.9% sodium tripolyphosphate, 19.5% sodium carbonate and 24.7% sodium sulphate. The base beads disclosed in both documents are subsequently oversprayed with nonionic surfactant.
We have now discovered that spray-dried base beads consisting essentially of sodium tripolyphosphate (STP) and sodium carbonate, with a relatively high proportion of carbonate, unexpectedly show a higher absorptivity for liquid nonionic surfactants, a lower tendency to allow the nonionic surfactant to bleed out, and a faster dissolution rate, than would be expected from the behaviour of the constituent salts. These advantages are observed only within a particular ratio range of STP to carbonate, and when no more than 10% by weight of other materials are present.

DEFINITION OF INVENTION

The present invention accordingly provides a porous spray-dried material suitable for carrying mobile ingredients in a detergent composition, wherein the solids content consists of

(i) from 90 to 100% by weight of sodium tripolyphosphate and sodium carbonate in a weight ratio of from 0.1:1 to 1.5:1; and
(ii) from 0 to 10% by weight of other ingredients.

The invention further provides a detergent composition or component therefor, comprising

(I) from 15 to 40% by weight of a liquid or pasty detergent component sorbed onto
(II) from 60 to 85% by weight of a porous carrier material as defined in the previous paragraph,

DESCRIPTION OF INVENTION

The solids of the porous carrier material of the invention consist wholly or predominantly (to an extent of at least 90% by weight) of sodium tripolyphosphate (STP) and sodium carbonate in a weight ratio of from 0.1:1 to 1.5:1, preferably from 0.25:1 to 1.5:1. The proportion of sodium carbonate is thus relatively high, and since the absorptivity of sodium carbonate for liquids such as nonionic surfactants is low it is surprising that material in accordance with the invention containing as little as 20% STP (ratio 0.25:1) has an absorptivity value approaching that of STP itself.
Carrier materials in accordance with the invention, when treated with liquid or liquefied nonionic surfactants, form free-flowing powders showing little tendency to nonionic surfactant bleeding and having high dissolution rates in water. Such materials are therefore highly suitable as detergent compositions in their own right, or as components (hereinafter referred to as adjuncts) for detergent compositions. For convenience, the term "adjunct" will be used to refer to combinations of the porous carrier material and a liquid or pasty detergent component, even though such combinations may be usable as such as detergent or cleaning compositions.
In the porous carrier material of the invention, a ratio of STP to carbonate of from 0.7:1 to 1:1 is of particular interest because especially free flowing powders are obtained, but the whole ratio range of 0.1:1 to 1.5:1 is useful.
The porous carrier material is prepared by spray-drying an aqueous slurry. The slurry is preferably prepared at a temperature not exceeding 70°C, to allow the growth of small, fully hydrated STP crystals; a temperature of 60-70°C is preferred. Advantageously, the STP is added first to the slurry-making vessel and a period of at least 5 minutes is allowed to elapse before the sodium carbonate is added. After addition of the sodium carbonate the temperature is preferably raised to 75-85°C and the slurry mixed for a further 10-20 minutes before it is conveyed to the spray-drying tower. Spray-drying is preferably carried out so as to give a powder having a moisture content of 10-15%. Drying further increases porosity.
If desired, minor amounts of other materials may be included in the slurry, or subsequently admixed, provided that these materials do not interfere with the absorptivity of the carrier material or the non-bleeding properties and rapid dissolution of the subseqently prepared adjunct, and provided that the total amount of such materials does not amount to more than 10% by weight of the porous carrier material. Examples of materials that may be incorporated include the following.

(a) Up to 10% by weight, preferably not more than 5% by weight, of sodium silicate, to improve particle structure and strength; higher levels cause an unacceptable decrease in absorptivity and in the dissolution rate of the adjunct.
(b) Up to 10% by weight of other inorganic salts, for example, sodium sulphate.
(c) Up to 5% by weight of anionic and/or nonionic surfactant, to stabilise the slurry and improve its pumpability; nonionic surfactant also accelerates the absorption of nonionic surfactant by the spray-dried powder.
(d) Up to 5% by weight of polymers, for example, polymeric polycarboxylates for crystal growth modification as described in EP 221 776A (Unilever), published after the priority date of this application on 13 May 1987.

The adjunct of the invention contains from 15 to 40% by weight of a liquid or pasty detergent component sorbed onto from 60 to 85% by weight of the porous carrier material of the invention. The term "liquid or pasty detergent component" is intended to encompass any liquid or pasty ingredient that may usefully be incorporated in a detergent composition, and does not necessarily imply surface activity. The liquid or pasty detergent component will generally be wholly or predominantly organic, but need not be. Examples of components that may be carried in the adjunct of the invention are anionic surfactants, nonionic surfactants, fabric softening amines, and lather suppressors, for examples, alkyl phosphate/petroleum jelly, silicone oil/hydrophobic silica. Although the invention will be described primarily in terms of nonionic surfactants, it should be remembered that it is equally applicable to other liquid or pasty ingredients.
The adjunct of the invention is prepared by treating the porous carrier material of the invention with the liquid or pasty detergent component. A preferred method for preparing the adjunct is to spray the component, after melting or solvent dissolution if necessary, onto the carrier material. During the spraying process, the carrier material is advantageously agitated in apparatus, for example, a rotating drum, that continually presents a changing surface of powder to the sprayed liquid; and the spray nozzle is advantageously angled so that liquid that penetrates the powder curtain falls on further powder rather than the shell of the drum itself.
Adjuncts in which the liquid or pasty detergent component is a nonionic surfactant represent a preferred embodiment of the invention.
Suitable nonionic surfactants which may be used include in particular the reaction products of compounds having a hydrophobic group and a reactive hydrogen atom, for example aliphatic alcohols, acids, amides or alkyl phenols with alkylene oxides, especially ethylene oxide either alone or with propylene oxide. Specific nonionic detergent compounds are alkyl (C₆-C₂₂) phenol-ethylene oxide condensates, generally 5 to 25 EO, ie 5 to 25 units of ethylene oxide per molecule, the condensation products of aliphatic (C₈-C₁₈) primary or secondary linear or branched alcohols with ethylene oxide, generally 5 to 40 EO, and products made by condensation of ethylene oxide with the reaction products of propylene oxide and ethylenediamine. Other so-called nonionic detergent compounds include long chain tertiary amine oxides, long chain tertiary phosphine oxides and dialkyl sulphoxides.
Of especial interest in the context of the present invention are the ethoxylated aliphatic alcohols.
The invention is especially of applicability to adjuncts carrying nonionic surfactant of which at least 50% by weight has an average of less than 6 moles of ethylene oxide per mole, which are difficult to incorporate by spray-drying. The invention may also be used to incorporate nonionic surfactants with greater amounts of ethylene oxide per mole.
As hinted above, porous carrier materials of the invention intended to carry nonionic surfactant advantageously contain a low level, for example, 0.5 to 2% by weight, of nonionic surfactant incorporated via the slurry. This greatly increases the rate at which nonionic surfactant is absorbed by the spray-dried carrier material.
An adjunct of the present invention containing nonionic surfactant is useful in its own right as a detergent or cleaning composition. Alternatively, however, it may be incorporated in a detergent powder containing other ingredients, in particular, a spray-dried detergent powder.
One advantage, not previously mentioned, of the porous carrier material and adjunct of the invention, is that they can be prepared to a high bulk density. The adjunct preferably has a bulk density of at least 0.45 g/ml, more preferably at least 0.55 g/ml, and desirably at least 0.65 g/ml. An adjunct of high bulk density can thus be mixed with a spray-dried base powder of high bulk density, for example, at least 0.45 g/ml and preferably at least 0.55 g/ml, to give a final product of high bulk density. The adjuncts of the invention also have excellent flow properties, so that admixture of such an adjunct with a detergent base powder will not generally give a final product having worse flow properties than the base powder.
A nonionic surfactant adjunct in accordance with the invention is suitably incorporated in a particulate detergent composition in an amount of from 5 to 25% by weight, preferably from 10 to 20% by weight. The amount of nonionic surfactant incorporated in the detergent powder by means of the adjunct may range, for example, from 2 to 10% by weight.
The final particulate detergent composition preferably has a bulk density of at least 0.45 g/ml, more preferably at least 0.55 g/ml.
The adjunct is suitably incorporated in the composition by dry mixing.
The particulate detergent composition may contain all or any of the conventional ingredients. It will generally contain one or more anionic and/or nonionic surfactants and one or more detergency builders.
Anionic surfactants are well known to those skilled in the detergents art. Examples include alkylbenzene sulphonates, particularly sodium linear C₈-C₁₅ alkylbenzene sulphonates having an average chain length of C₁₁-C₁₃; primary and secondary alcohol sulphates, particularly sodium C₁₂-C₁₅ primary alcohol sulphates; olefin sulphonates; alkane sulphonates; and fatty acid ester sulphonates.
It may also be desirable to include one or more soaps of fatty acids. The soaps which can be used are preferably sodium soaps derived from naturally occurring fatty acids, for example the fatty acids from coconut oil, beef tallow, sunflower or hardened rapeseed oil.
The particulate detergent composition may also include one or more nonionic surfactants, in addition to any nonionic surfactant incorporated by way of the adjunct of the invention. Examples of suitable nonionic surfactants are the primary and secondary alcohol ethoxylates, especially the C₁₂-C₁₅ primary and secondary alcohols ethoxylated with an average of from 5 to 20 moles of ethylene oxide per mole of alcohol.
The STP and sodium carbonate present in the adjunct of the invention act as detergency builders, but will not generally be present in a sufficient amount to provide adequate building. Preferred builders for inclusion in the particulate detergent composition include phosphates, for example, orthophosphates, pyrophosphates and (most preferably) tripolyphosphates. Non-P builders that may be present include, but are not restricted to, sodium carbonate, crystalline and amorphous aluminosilicates, soaps, sulphonated fatty acid salts, citrates, nitrilotriacetates and carboxymethyloxsuccinates. Polymeric builders, for example, polycarboxylates such as polyacrylates, acrylic/maleic copolymers and acrylic phosphinates, may also be present, generally but not exclusively to supplement the effect of another builder such as STP or sodium aluminosilicate.
Other ingredients that may be present in the base powder slurry include alkali metal silicates, antiredeposition agents, antiincrustation agents and fluorescers.
The detergent composition of the invention may also contain various ingredients that are unsuitable for slurrying or spray-drying or that interfere with the spray-drying process, and such ingredients may be incorporated by spraying, dry-mixing or granulation. Examples of such ingredients are enzymes; bleaches, bleach precursors, or bleach activators; inorganic salts such as sodium sulphate, as described and claimed in EP 219 328A (Unilever); or sodium silicate as described and claimed in EP 240356 (Unilever) published in October 1987; lather suppressors; perfumes; dyes; and coloured noodles or speckles. Further examples of ingredients best incorporated by postdosing will readily suggest themselves to the skilled detergent formulator.

EXAMPLES

The following Examples illustrate the invention. Parts and percentages are by weight unless otherwise stated.

EXAMPLES 1 TO 6

Ten porous carrier materials (six in accordance with the invention, and four controls) were prepared by slurry-making and spray-drying. The inorganic salts (STP, sodium carbonate) were slurried together with 1% by weight, based on the inorganic salts, of nonionic surfactant (7EO). The slurries were prepared in a temperature-controlled, steam-jacketed, turbine-agitated vessel. Water was preheated to 65°C and STP then added; after 5 minutes sodium carbonate (light soda ash ex ICI) was added and the temperature controlled at 80°C. Mixing was continued for a further 15 minutes, then the slurries were conveyed to a countercurrent spray-drying tower, where they were spray-dried at an inlet gas temperature of 300°C to form powders having moisture contents of about 12%.
The carrier materials according to the invention contained STP and sodium carbonate in ratios ranging from 0.1:1 to 1.5:1. The controls were STP alone (A), sodium carbonate alone (B), and STP and sodium carbonate in ratios of 2.2:1 (C) and 0.05:1 (D) which are both outside the limits of this invention. The bulk density, flow rate and absorptivity for nonionic surfactant (4EO) were measured and the values are shown in Table 1.
The flow rates of the powders ranged from 75 to 109 ml/s, indicating that all were free-flowing and non-cohesive.
The nonionic surfactant absorptivity was measured by titrating each carrier with liquid nonionic surfactant (4EO) until the nonionic surfactant was no longer retained strongly by the particles: failure to retain surfactant was detected by the staining of a filter paper pressed against the powder. Values of 0.30-0.36 ml/g were obtained for the carriers 1 to 6 according to the invention, indicating a good capacity for liquid carrying. It will be seen that, surprisingly, the values for the carriers 1 to 6 according to the invention were not much lower than the value for the control A (STP alone), despite the fact that the control B (sodium carbonate alone) had a much lower value. A number of these values were distinctly higher than the values predicted by linear interpolation. This was notable when the STP:carbonate ratio was in the range 0.1:1 to 0.7:1 when the values predicted by linear interpolation are below 0.30 ml/g. The control (D) displayed an absorptivity better than predicted, but below 0.30 ml/g.
Nonionic surfactant adjuncts were prepared from each of the ten carriers by spraying 1 part of nonionic surfactant (4EO) onto 4 parts of carrier, while the carrier was mixed in a rotary mixer. After spray-on, a period of 24 hours was allowed for equilibration, then the properties listed in Table 2 were measured.
The tendency of the nonionic surfactant to "bleed" from the adjuncts was measured by leaving a standard weight of adjunct on a filter paper for 2 weeks at 40°C in a sealed container. After this period of time the weight of nonionic surfactant absorbed by the filter paper was determined. It will be seen that the adjuncts 1 to 6 according to the invention had nonionic surfactant bleeding figures well below those predicted by linear interpolation. Adjuncts 1 to 5 were free-flowing powders of high bulk density. Adjunct 6 had a slightly poorer flow rate whose acceptability was borderline while control D had an even lower flow rate and also displayed poor retention of surfactant.
The dissolution rate of each adjunct was determined by adding a fixed weight of the adjunct to a vessel containing water at 20°C in which constant agitation could be maintained, and by measuring the increase of electrical conductivity with time. The dissolution time was taken as that at which 95% of the equilibrium conductance was reached. As the carrier dissolved, nonionic surfactant was released: this was indicated by an increase in turbidity of the solution. Measurements were made on 180-250µ fractions of the adjuncts, in both demineralised and 48°H (French) water: no significant differences between the dissolution times in hard and soft water were observed, and mean results are presented in Table 2.
It will be seen that the adjuncts 1 to 6 dissolved faster than would be predicted by linear interpolation. Adjuncts 1 and 5 actually had shorter dissolution times than either of the controls A and B. Control C displayed a dissolution time of borderline acceptability, slower than any of adjuncts 1 to 6.
Thus control C showed good ability to carry nonionic surfactant with a borderline dissolution rate, control D had poor ability to carry nonionic surfactant but the adjuncts 1 to 6 had a good combination of properties better than predicted by linear interpolation between the values for controls A and B.

EXAMPLES 7 AND 8

Adjuncts were prepared to the following compositions:
These adjuncts were each prepared by spray-drying a porous inorganic carrier powder, and then nonionic surfactant was incorporated by spray-on to the powder in a batch mixer.
A spray-dried base detergent powder was prepared to the following formulation:
The powder was free-flowing and had a bulk density of 0.6-0.65 g/ml.
57.6 parts of the above mentioned high bulk density base powder containing 1% of 4EO nonionic were mixed with 17 parts of Adjunct 7 given above (effectively adding 3 parts of 4EO nonionic in adjunct form), together with the further ingredients listed below, to give the final formulation shown below. The bulk densities of the various components, and that of the final powder, are also shown. The final powder was free-flowing and non-caking.

EXAMPLES 9 TO 11

Carrier materials were prepared by a procedure similar to that for Examples 1 to 6 except that nonionic surfactant (7EO) was not always included. Nonionic surfactant adjuncts were then prepared by spraying 1 part of nonionic surfactant (4EO) onto 4 parts of each carrier, in a rotary mixer, and allowing a period of 24 hours for equilibration.
Compositions of the carrier materials are set out in Table 3 below together with properties of the carrier materials and adjuncts determined as described for Examples 1 to 6. Also included in this table is a comparative material, designated E.
Comparative composition E and Example 9 demonstrate the effect of silicate. In each case the ratio of STP to sodium carbonate is 0.7:1 as for Example 3. Ability to carry surfactant is satisfactory, and flow rate shows an improvement, especially in the case of composition E with over 10% silicate. However the inclusion of silicate has a detrimental effect on dissolution time, and that of Example 9 is of borderline acceptability.
Examples 10 and 11 demonstrate incorporation of low levels of other materials without detriment to carrier or adjunct properties.

Comparative Examples F and G

Two comparative examples outside the scope of the invention were performed. In each case the procedure was similar to that of earlier Examples in that a carrier material was prepared by spray-drying and 4 parts of this was sprayed with 1 part of nonionic surfactant (4EO) to give an adjunct. Compositions are set out in Table 4 below together with properties of the carrier materials and adjuncts determined as described for Examples 1 to 6.
Composition F reproduces Example 2 in British patent 1579261. The ratio of STP:carbonate is 5.2:1. The rate of dissolution is much slower than observed with Examples of this invention.
Composition G reproduces Example 1 in Canadian patent 978821. The ratio of STP:carbonate is 2.2:1. The STP and carbonate constitute less than 90% of the solids content of the composition. The carrier had poor ability to absorb and retain nonionic surfactant and the adjunct had a slow rate of dissolution.

Claims

1. A porous spray-dried material suitable for carrying mobile ingredients in a detergent composition, wherein the solids content consits of

(i) from 90 to 100% by weight of sodium tripolyphosphate and sodium carbonate in a weight ratio of from 0.1:1 to 1.5:1; and

(ii) from 0 to 10% by weight of other ingredients.

2. A material as claimed in claim 1, wherein the weight ratio of sodium tripolyphosphate to sodium carbonate is within the range of from 0.25:1 to 1.5:1.

3. A material as claimed in claim 1 or claim 2, which comprises as other ingredients (ii):

(a) from 0 to 10% by weight of sodium silicate and/or

(b) from 0 to 10% by weight of other inorganic salts, and/or

(c) from 0 to 5% by weight of one or more anionic and/or nonionic surfactants and/or

(d) from 0 to 5% by weight of one or more polymers.

4. A porous spray-dried material as claimed in any one of claims 1 to 3 wherein the amount of silicate present is not more than 5% by weight of the solids content.

5. A detergent composition or component therefor, comprising

(I) from 15 to 40% by weight of a liquid or pasty detergent component sorbed onto

(II) from 60 to 85% by weight of a material as claimed in any preceding claim, the percentages being based on the total of (I) and (II).

6. A particulate detergent composition having a bulk density of at least 0.45 g/ml, comprising one or more anionic and/or nonionic surfactants, one or more detergency builders and optionally other conventional ingredients, and containing from 5 to 25% by weight of an adjunct comprising a nonionic surfactant sorbed onto a porous spray-dried material as claimed in any one of claims 1 to 3.