CA2040307A1

CA2040307A1 - Effervescent detergent tablets

Info

Publication number: CA2040307A1
Application number: CA 2040307
Authority: CA
Inventors: Yogesh Sennik
Original assignee: JORIKI INC.
Current assignee: JORIKI Inc
Priority date: 1991-04-12
Filing date: 1991-04-12
Publication date: 1992-10-13

Abstract

ABSTRACT
A laundry detergent tablet comprising a water-disintegratable dry laundry detergent tablet having a composition comprising a synthetic organic detergent compound and an effervescence-generating agent in intimate admixture therewith. The tablets provide a detergent composition of reduced weight and volume, with an enhanced safety feature. The tablets may be further provided with a water soluble but humidity resistant coating.

Description

- 1 - 20~3~7 EFF~RVESCE~T D~TeRGENT TABLETS
-FIELD OF THE INVENTION
-This invention relates to detergent compositions and more particularly to effervescent detergent compositions in the form of tablets.
BACKGROUND OF THE INVENTION
Laundry detergents are presently provided in the form of granular powders or concentrated aqueous solutions.
These formulations constitute additional bulk due, in the case of free flowing granular powders, to entrapped air, or in the case of aqueous solutions to significant amounts of water. Further, in the latter case, such water also results in a significant weight increase over the amount of detergent active ingredient to be handled.
Yet further, each of the above two forms of formulations requires a measurement to be made, by the consumer, of the amount of detergent to be added to the laundry wash,~which measurement requires a measuring cup and action which is prone to error.
Yet still ~urther, household detergent formulations in the form of powders and, particularly, liquids, constitute a health safety hazard in being in an available, readily ingestable form. Accidental ingestion by small children is possible should good housekeeping precautions by the consumer not be taken or inadvertently lapse.

, , ' : . . ' ' ~ 2 20403~7 Thus, there is a demand to provide laundry detergent to the trade and/or consumer in a form which minimizes the bulk and weight of the detergent and its packaging, obviates the need for measurement and with enhanced safety features.
Detergent compositions in the form of tablets and the like are well known in the art. U.S. Pate~t No.
4.370,250, issued January 25, 1983, however, sets out a detailed description, of the problems associated with providing a detergent in tablet form.
For a cleaning tablet to be commerically acceptable, it must be of sufficient strength so that it will not break under normal production, packaging and handling conditions, yet it must also be readily dispersed in cold water so as to provide the desired function comparable to that of granular or liquid products, which are, because of their physical nature, readily dispersable in the washing medium. A disintegration time for a detergent tablet of about three minutes or less is considered to be a highly desirable rate from both the viewpoint of the detergent being dispersed in the water and the minimization of spotting of the clothes by local concentrations of detergent. Additionally, overcoming these problems is further complicated by the need today for cleaning products which are egually suitable for both hot water and cold water applications. Cold water washing, in . . .

- ~- 20~307 particular, is especially important because of the need to conserve energy and it is imp~rtant that the tablets may be used interchangeably for either cleaning application.
Cold water, in terms of cleaning products, usually means tap water, which has a temperature range of about 70F.
The art has attempted to resolve the dichotomy between a cleaning tablet having sufficient physical strength and satisfactory water-dispersability, as well as other associated problems normally encountered with such tablet products, by using very specialized cleaning formulations and processing techniques. The solution to these problems is beset with many difficulties. While handling of the tablet without breakage normally requires the tablet to have a high strength, cleaning tablets normally disintegrate much more slowly as the tablet strength is increased. These competing forces, coupled with the inherent nature of cleaning tablets to be much more readily disintegrated in hot water than in cold water, present the manufacturer with formidable problems to be overcome to provide tablets having the desired characteristics.
Further, the operation of a conventional tablet press is hampered drastically if the ~ase powder beads to be compressed into tablet form are (a) not free flowing (b) sticky and tacky (c) light in density with correspondingly high bulk and (d) weak and fragile when compressed.

- 4 ~ 20~0307 Surprisingly, we have discovered that a detergent composition can be formulated in the form of a tablet and the like, which has sufficient stabili~y to withstand normal tablet packaging and transportation and yet which dissolves satisfactorily in a laundry wash. ~e have found that the detergent tablets of the present in~ention when placed in contact with water are, surprising'y, adequate to result in rapid disintegration of the tablels to enable the detergent to dissolve in the water.
It is an object of the present invention ~o provide a laundry detergent formulation in tablet form which has improved disintegration and solubility properties on addition to water.
S~MMARY OF THE INVENTION
.
In view of the need in the art explained hereinabove, the present invention provides a stable laundry detergent tablet which, when added to the laundry water, dissolves to form a foaming cleansing solution.
- Accordingly, the invention provides in its broadest aspect a water-disintegratable dry laundry detergent tablet having a composition comprising a syn~hetic organic detergent compound and an effervescence-generating agent in intimate admixture therewith.
The tablet may contain from about 5% w/Y to about 25%
w/w of detergent compound.

2 ~ 4 ~

Preferably, the tablet comprises from about 10 to about 20% of detergent compound, and more preferably, from about 15 to about 18~ of detergent compound.
In addition to the detergent tablets and the like according to the invention, also included are processes for manufacturing such tablets and methods for washing laundry using such tablets.
The synthetic organic detergent compound of use in the practice of the invention is generally an anionic synthetic organic detergent, preferably of the water soluble sulfated and/or sulfonated lipophile type, but in some instances, different synthetic organic detergents ~ay be employed, usually as mixtures of anionic and nonionic detergents.
Of the synthetic anionic oeganic detergents those preferred are higher alkyl (preferably linear alkyl) benzene sulfonates, higher fatty alcohol sulfates, higher fa-tty alcohol ethoxylate or polyethoxylate sulfates, olefin sulfonates and paraffin sulfonates. Usually such compounds are water soluble alkali metal salts, such as sodium salts, and include higher fatty alkyl or other aliphatic moieties, which serve as lipophilic moieties, and which increase detergency. Such higher alkyl or higher aliphatic moieties will normally be of 8 to 20 carbon atoms, preferably 12 to 18 carbon atoms and more preferably, especially for the alkylbenzene sulfonates, 12 - 6 - ~04~7 to 14 carbon atoms. As representatives of such detergents there may be mentioned sodium linear tridecylbenzene sulfonate, sodium linear dodecylbenzene sulfonate, sodium lauryl al~oho1 sulfate, sodium coco alcohol triethoxylate sulfate, sodium Cl6 paraffin sulfonate and sodium olefin sulfonate derived from Cl4 olefin.
Althouyh nonionic detergents are not preferred detersive co~ponents of the present compositions and products, they may be employed, usually in relatively minor proportions, and normally in conjunction with an anionic detergent. Among the nonionic detergents, those which are most preferred are ethylene oxide condensates with higher fatty alcohols or with alkyl phenols, such as condensation products of 3 to 12 moles of ethylene oxide with highec fatty alcohols of lO to 15 carbon atoms or with alkyl phenols of 7 to 10 carbon atoms in the alkyl groups, e.g. Neodol~ 257.
_ In addition to the described anionic and nonionic detergents, in some instances, amphoteric, ampholytic and zwitterionic detergents may be present, normally in relatively minor proportions. In some instances, cationic detergents may be utilized, also normally in relatively minor proportions, e.g., less than 10%, but in some circumstances, as when such cationic detergent or surface active agent is intended to be the fabric softener in a composition or product to be blended with or to be used ..

20~03~7 with such detergent composition, so as in that way to produce a "softergent", uQ to 20 to 30~ may be employed.
~xtensive listings of detergents that are useful for practicing the present invention may be found in standard textbooks relating to synthetic organic detergents, of which there may be mentioned herein, as representative, Surface Active Agents (Their Chemistry and Technology) by Schwartz and Perry, and the various annual editions of John W. McCutcheon's Detergents and Emulsifiers, e.g. that of 1980.
Hydratable builder salts may be used with the synthetic organic detergent. Sodium salt of ethylene diaminetetracetic acid (EDTA), trisodium salt of nitriloacetic acid (NTA) and sodium tripolyphosphate are preferred, but other such salts may also be employed, either alone or in admixture with such salts, such as, for example, tetrasodium pyrophosphate and other pyrophosphates, sodium carbonate, sodium sesquicarbonate, sodium silicate, sodium sesquisilicate or borax. In some ~
instances, it may be desirable to mix with such salts builders which are not hydratable. Hydratable filler salts may be employed in some instances but normally will desirably be omitted from the compositions because they add only bulk, and do not contribute to detergency. Of the builders the polyphosphates are highly preferred, and of those, particularly, sodium tripolyphosphate.

- 8 - 204~3~7 The effervescence producing agents of use in the practice of the invention comprise an acid and a compound which reacts with the acid in water to generate gas bubbles to effect disintegration and agitation when the tablet is added to water.
Preferably, the effervescence producing agent is a carbon dioxide generating mixture comprising a carbonate compound and an acid. By ~carbonate compound" is meant an alkali metal carbonate or bicarbonate, such as for example carbonate or bicarbonate of sodium or potassium. The acid component is preferably citric or tartaric acid or_ mixtures thereof but may be other water soluble acids including mixtures thereof such as, for example, sodium or potassium acid phosphates, gluconic acid, malic acid, and the like. The acid and the carbonate compound are generally employed in approximately stoichiometric amounts, although a very slight excess of acid may be employed to effectively generate the potential carbon dioxide. Large excesses of acid are generally not desirable.
The tablets may have as an additional or alternative effervesence producing agent one or more peroxygen or active oxygen compounds such as sodium perborate monohydrate, sodium perborate tetrahydrate, potassium persulfate, sodium carbonate peroxide and the like, which cause the tablets to evolve microbubbles of nascent or - 2~403~7 active oxygen as they are dissolved in water and provi~e an additional oxidizing, cleansing action, including a bleaching effect on the laundry. A hypochlorite ion forming oxidizing agent may, optionally, be included to provide an additional oxidizing, cleansing action.
The effective amount of the effervescence producing agent in the tablet will depend on the nature and amounts of the remaining ingredients present in the composition of the tablet. This amount can be readily determined by the skilled man without the exercise of his inventive faculty. Accordingly, the effervescence_producing agent will be present in the tablet in an effervescent effective amount to effect the required disintegration in a laundry wash.
The synthetic organic detergent compositions of use in the invention preferably further comprise conventional detergent composition additives. For instance, in addition to the aforesaid builder salts, which are hard water softeners, generally chelating agents, used to enhance the cleaning ability of the detergent surfactant, alkali, such as granular sodium hydroxide and/or sodiu~
metasilicate is very preferably also present to provide an increase in the pH tOr at least, the neutral level.
We have found that the presence of salts, alkali and bu1lders which are readily soluble in water also enhance the disintegration process. We have, further, found that, .

lO - 2~ ~0~ ~

surprisingly, the gas bubbles generated by the effervescent action provides an additional agitation action to the detergent and enhances the desirable foaming effect sought in a laundry wash.
Thus, we have found that the disintegration times of the de~ergent tablets according to the invention are also dependent upon the choice and amounts of salts, alkali and builders. However, the amount of alkali used to increase the p~ of the laundry wash solution in the practice of the present invention can be kept to a minimum and well below that conventionally used. The ~referred composition of use provides an approximate neutral solution of pH 7.
Enzymes and fluorescent whitening agents are further optional additives. The tablet compositions may thus additionally comprise detergent enzymes such as amylases and proteases. Examples include ESPERASETM and SAVINASETM
protease enzymes. (Novo Nordisk Bioindustries, Netherlands) and BANTM and MAXATASETM amylase enzymes.
The detergent tablets may be made with relatively inexpensive, easy-to-operate and trouble-free standard mixing and tablet-forming equipment. In view of the sticky and tacky nature of the majority of built synthetic organic detergents having the desired detergency proper~ies, we have found that the presence of a de-tackifier compound, such as talc, titanium dioxide, magnesium stearate, in an amount of from about 0.05 to 20403~7 about 5% w/w in the ?reparation of the tablet, assists the mixing and tabletting by reducing the tackiness of the detergent compound. The amount of such de-tackifer will be dependent on the detergent composition, but can be readily determined by the skilled man.
Thus, in a further feature the invention provides a process for the manufacture of a detergent tablet as hereinbefore defined which process comprises intimately mixing said detergent compound and said effervescence-generating agent to provide an admixture thereof, and compacting said admi~ure in the form of a tablet.
We have, surprisingly, found that the tablets of the present invention are advantageously and significantly more compact than the tablets disclosed in USP 4,933,100, wherein a density of 0.8 g/cm3 is reported. Such an enhanced density of the tablets of the present invention with a concommittent satisfactory disintegration rate provides for the manufacture of tablets of advantageously reduced size.
Typically, tablets with greater than 80~
disintegration in the first 3 minutes, very satifactorily breakdown with the ac~ion of the water, agitation of the machine and the friction of the clothes. Tablets with less than 80% disintegration, although of value, do not breakdown fully when ~sing a short 6 minute wash cycle.

- 12 - 2~4~307 Thus, in a yet further feature the invention provides a method of cleaning laundry comprising adding a detergent tablet as hereinbefore defined to a laundry wash for a sufficient period of time to effect cleaning of said laundry.
By the term "tablet'l is meant a compact mass of a detergent composition according to the invention in the form of a suitable shape to utilize the concept of the invention. Preferably, the tablet takes the form of a disc, cube, square or solid cylinder. It is not necessary that each individual tablet contains the requisite amount of detergent for a full laundry wash. Although not preferred, clearly, such a requisite amount could be provided by a combined amount from a plurality of tablets.
We have found that the manufacture and shelf stability of the tablets are dependent on the free water content of the compositions, i.e. water not bound up as water of crystallization or in hydrat~d salts. The free water content should not be greater than 3% w/w of the composition, preferably ~ O.5% w/w and more preferably ~ 0.1% w/w i.e. the tablets should be dry.
Thus, in this specification and claims the term "water-disintegratable dry laundry detergent tablet" means a ta~let having no more than 3% w/w free water content.
We have further found in shelf-life studies with the tablets that they may absorb moisture and over a two to - 13 ~ 0~7 three-week period show signs of "pitting" with the surface becoming rough. Although this does not effect th3 performance of the detergent, testing shows that the initial effervescent reaction upon submergence of t~e tablets in water is not as violent as compared to fresh"
samples. This, however, changes into aggressive ~bling after the pitted surface has an opportunity to dissolve away, generally after about 2-S seconds.
In order to provide an improved tablet resis~nt to humidity and, thus, a product having an extended shelf-life, the tablet has been given a humidity resist~nt, water soluble coating.
Accordingly, in a preferred feature, the inven~ion provides a water-disintegratable dry laundry deterg~nt tablet as hereinbefore defined provided with a water-~oluble coating.
An example of such a coating is provided by spraying the tablets with an effectiv~ amount of non-aqueo1s solvent based cellulosic composition sold under the trade mark OPADRY CLEARCOAT (Colorcon, U.S.A.). As the solvent, typically an aliphatic alcohol such as ethyl alcohol, evaporates, a thin glossy cellulosic film forms to protect the tablet.
Accordingly, in a preferred process, the invention provides a process for the manufacture of a detergent tablet as hereinbefore defined further comprising coating said tablet with a water-soluble coating composition.

. . .

- 14 - 2~ 7 In a further featurer the invention provides a method ef cleaning laundry as hereinbefore defined wherein said tablet is coated with a water-soluble coat.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In order that the invention may be better understood ~referred embodiments will now be described with reference ~o the accompanying examples.
The efficacy of a detergent composition in a laundry wash was measured by a visual noting of the degree of removal of an artificially induced stainl such as ketchup, tomato, and the like and of measurement of the brightness.
Example 1 A detergent tablet was made having the following composition:-% w/w Sodium dodecylbenzene sulphonate t90% a.i.;
NANSATM HS85/S-Albright and Wilson Ltd.) - talc (4% w/w) 16 Sodium metasilicate 4.8 Citric acid 18 Sodium bicarbonate 51 Sodium hydroxide (50% granular) 4 rthylene diaminetT~raacetate acid (Kalex ~00TM) 5 Amylase (MAXATASE ) - protease (~AXAMYLT ) enzyme mixture (1:1) w/w 1.15 Fluorescent whitening agent (TINOPALTM AMS-GX stilbene type - Ciba-Geigy) 0.05 The above ingredients, totalling 450 kg. were, sequentially, mixed in a ribbon blender (Britton Machine, Guelph, Ontario, Canada). Sodium dodecylbenzenesulphonate surfactant and talc, 4% w/w, de-tackifer, were charged to . .

- 15 - 2~4~7 the blender and mixed for 2 minutes. The following ingredients, namely, sodium metasilicate, sodium bicarbonate, sodium hydroxide, citric acid, ethylene diamine tetraacetate acid, enzymes and fl~orescent whitening agent were, subsequentl~, added, in sequence, after a respective 2-3 minute blending time between individual additions. The composition was sufficiently dry to prevent or significantly reduce any effervescence reaction between the citric acid and sodium bicarbonate.
The composition was formed into 54 g, disc-shaped tablets having a density of 1.42 g/cm, a 5.8 cm. diameter and 1.47 cm. thickness, using a STOKES-RTM tablet press under a compression ratio of 2.8:1.
Disintegrations tests were conducted by weighing the tablet before it was placed in water and after it was submerged for 3 minutes in water and, subsequently, dried. The disintegration figure is based on the percentage mass reduction.
The tablets of Example 1 were found to satisfactorily disintegrate to a 82~ degree within a standard 3 minute period.
Example 2 A detergent tablet was made having the identical composition as the tablet of Example 1 but with an alternative surfactant, namely, the sodium salt of the linear alkyl benzenesulphonate sold under the trade mark .

- 16 - 2040~07 NACCONOLTM 90G (Stepan Compan~, Illinois, U.S.A.), substituted for the surfactant described in Example 1.
The tablets were identical to ~hose of Example 1 in disintegration characteristics and efficacy.
Example 3 Detergent tablets according to the present invention were made incorporating a peroxy bleach agent, namely, sodium perborate (monohydrate) and having the composition:
% w/w Sodium d~decylbenzene sulphonate (90% a.i.;
NANSAT HS85/S-Albright and ~ilson ~td.) -(titanium dioxide, 0.5% w/w) 16 Sodium metasilicate 4.8 Citric acid 14 Sodium bicarbonate 36 Sodium hydroxide (50% - granular) 4 NTA
Sodium perborate (Monohydrate) 19 Amylase and Protease (1:1 w/w) 1.1 Fluorescent whitening agent, TINOPALTM AMS-GX stilbene type (Ciba-Geigy) 0.05 These tablets were found to have excellent laundry cleaning properties and a superb disintegration rate.
Example 4 This example illustrates the effect of detergent additives, such as salts, alkali or builders on the disintegration rate of a table~ according to the invention having constant amounts of the same detergent (surfactant) and effervescence-producing agent. The enzymes and FWA
were as for Example 1.

.

~0~3~7 The resJlts are given in the Table and show that the disintegration varied from 59-81~.

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8 ~ e ~ ~; .S 5 19- ~0~7 Example 5 Comparative tests were carried out on tablets prepared fr~m three commercially available laundry detergents.
The granular powders of three commercially available detergents were individually compacted into the tablet form as described for the compositions of ~he invention of Examples 1 to 4. Difficulty was found in ~he preparation of these tablets in that the press had to ~e modified to allow for adequate compacting. It is believed that the ~ 3% w/w water content inherent in the detergent composition contributed to this difficulty.
The compacted tablets of these commercial detergent compositions did not disintegrate and produce a readily soluble cleaning solution when added to water.
One of the commercial powder compositions was mixed with various amounts of sodium bicarbonate~citric acid effervescence producing agent and formed into tablets.
The results of the three minute resid~nce diaintegration tests ~e shown below.

., . ~ . , .

.

- 20 - 2~03~

NaHC03/
citric acid % disintegration Commercial detergent 20 6.8 15.2 The results indicate that disintegration and cleansing were obtained. The nature of the commercial composition in being ~ 3% w/w water-containing to effect undue compacting of the tablet does not produce a preferred tablet according to the invention.
Although this disclosure has described and illustrated certain preferred embodiments of the invention, it is to be understood that the invention is not restricted to these particular embodiments. Rather, the invention includes all embodiments which are functional or mechanical equivalents of the specific embodiments and features that have been described and illustrated herein.

Claims

1. A water-disintegratable dry laundry detergent tablet having a composition comprising a synthetic organic detergent compound and an effervescence-generating agent in intimate admixture therewith.

2. A water-disintegratable dry laundry detergent tablet as claimed in Claim 1 wherein said detergent is an anionic synthetic organic detergent compound.

3. A water-disintegratable dry laundry detergent tablet as claimed in Claim 2 wherein said detergent is a water soluble sulfated and/or sulphonated lipophile anionic synthetic organic detergent compound.

4. A water-disintegratable dry laundry detergent tablet as claimed in Claim 3 wherein said detergent compound is selected from the group consisting of higher linear alhyl benzene sulphonates, higher fatty alcohol sulfates, higher fatty alcohol ethoxylate or polyethoxylate sulphates, olefin sulphonates and paraffin sulfonates.

5. A water-disintegratable dry laundry detergent tablet as claimed in Claim 4 wherein said detergent compound is a C12 - C18 alkyl benzene sulphonate.

6. A water-disintegratable dry laundry detergent tablet as claimed in Claim 1 wherein said effervescence-generating agent comprises a mixture of sodium bicarbonate and citric acid.

7. A water-disintegratable dry laundry detergent tablet as claimed in any one of Claims 1 to 6 wherein said detergent compound is present in an amount of from about 10 to about 20% w/w.

8. A water-disintegratable dry laundry detergent tablet as claimed in any one of Claims 1 to 6 wherein said detergent compound is in an amount of from 15 to 18% w/w.

9. A water-disintegratable dry laundry detergent tablet as claimed in any one of Claims 1 to 6 further comprising a de-tackifier.

10. A water-disintegratable dry laundry detergent tablet as claimed in any one of Claims 1 to 9 provided with a water-soluble coating.

11. A process for the manufacture of a detergent tablet as claimed in any one of Claims 1 to 10 which process comprises intimately mixing said detergent compound and said effervescence-generating agent to provide an admixture thereof, and compacting said admixture in the form of a tablet.

12. A process as claimed in Claim 11 further comprising coating said tablet with a water-soluble coating.

13. A method of cleaning laundry comprising adding a detergent tablet as claimed in any one of Claims 1 to 10 to a laundry wash for a sufficient period of time to effect cleaning of said laundry.