Powdered Nonionic-Based Detergent Compositions Containing Sodium Acetate Trihydrate

This invention relates to improved nonionic-based detergent formulations in powdered form. In particular, this invention relates to such nonionic-based detergent formulations in powdered form which further include sodium acetate trihydrate as a stability promoting agent. Another aspect of this invention relates to a process for the making of said nonionic-based detergent formulations in powdered form.

By way of general background, it sould be noted that in detergent compositions which employ nonionic surface active agents or detergents, there is a tendency of such detergent to "bleed out" from the detergent composition as a whole. Such bleeding is not necessarily dependent upon the nature of the container in which the detergent composition is placed. Thus, nonionic surface active agents are known to bleed out of detergent compositions and to absorb themselves onto the glass walls of beakers in which they might have been placed. Naturally, in the consumer context, where such detergent compositions are ordinarily placed in cardboard boxes, such nonionic surfactant bleeding will be more severe as a result of the absorbent nature of such cardboard boxes. While such nonionic bleeding may be minimized by storing such detergent compositions in impervious receptacles such as plastic bottles or other containers, the nonionic bleeding problem is not thereby totally eliminated. In the case of such impervious receptacles, the nonionic detergent active compound tends to bleed out of the powdered detergent composition in any event whereby it ends up being adsorbed upon the walls of such impervious receptacle.

The phenomenon of nonionic surfactant bleeding is undesirable for several reasons. Firstly, such bleeding leads to unsightly discoloration of the cardboard boxes in which a nonionic surfactant based powdered detergent composition is ordinarily placed for sale to the consuming public. As a result, not only is the aesthetic appeal and saleability of such a powdered detergent composition package reduced, but the performance of the detergent composition contained therein is itself adversely affected. Such adverse effects are twofold. Firstly, the loss of some of the surface active compound to the walls of the receptacle in question causes reduction of the cleaning strength of the detergent composition as a whole. Moreover, the powdered detergent composition in closest proximity to the absorbent walls of the container loses a greater proportion of its nonionic surfactant content, as opposed to those portions of such powdered detergent composition which are located at a greater distance from such walls. As a result, the powdered detergent composition contained in such a box becomes non-uniform with consequent unpredictability of its cleaning power and erosion of consumer confidence in the product in question.

Accordingly, a method of preventing nonionic surfactant bleeding in detergent compositions containing such nonionic surfactants would not only promote the storage life of such detergent compositions, but would also result in increased consumer appeal and acceptance of such detergent products. Moreover, by minimizing or eliminating the need to utilize plastic bottles or other containers in favor of conventional cardboard type boxes or containers, further savings are effected in terms of packaging materials from which the consuming public can be expected to ultimately benefit. As already noted above, unless nonionic surfactant bleeding can be effectively arrested, even the more expensive plastic receptacles would not be entirely satisfactory.

Commonly assigned U.S. patent application Ser. No. 555,776 filed on Nov. 28, 1983 discloses the utility of magnesium sulfate heptahydrate as an additive for the minimization or elimination of nonionic surfactant bleeding from a powdered detergent composition containing a nonionic surfactant.

It has now been surprisingly discovered that the undesirable phenomenon of nonionic surfactant bleeding from a powdered detergent composition can also be minimized or eliminated by the alternative incorporation within such a detergent composition of sodium acetate trihydrate.

According to the present invention, a particulate nonionic based non-phosphate detergent composition of improved storage stability wherein nonionic surfactant bleeding is minimized or eliminated further comprises in admixture therewith an effective amount of sodium acetate trihydrate to substantially arrest and/or inhibit nonionic bleeding from said detergent composition, a representative composition comprising nonionic detergent active compound to sodium acetate trihydrate in the ratio w/w of about 1.0:0.9.

In another aspect of the present invention, a method for making a nonionic based non-phosphate particulate detergent composition is provided which comprises the steps of (a) adding a nonionic detergent active compound or compounds to a pulverized particulate mixture comprising finely divided sodium acetate trihydrate to form a detergent mixture; (b) optionally adding further particulate matter comprising further detergent materials to the detergent mixture to form an ultimate mixture; and (c) blending the ultimate mixture thoroughly.

The following illustrative but non-limiting Examples will aid in a fuller understanding of the present invention. Examples I through IV are substantially identical to Examples I through IV included in U.S. patent application Ser. No. 555,776 referred to above. They are included herein to demonstrate the superiority of the sodium acetate trihydrate additive of the present invention over the magnesium sulfate heptahydrate additive of the invention disclosed in U.S. patent application Ser. No. 555,776.

Table 1 noted below lists the ingredients of detergent composition A containing magnesium sulfate heptahydrate and detergent composition B not containing magnesium sulfate heptahydrate which were initially compared against each other with respect to the rate of nonionic surfactant bleeding. Both compositions contained an identical percentage w/w of the same nonionic surfactant.

The respective compositions were mixed using a domestic use blender, i.e., a Kitchen Aid brand cake mixer and a "V" blender (Patterson-Kelley Company, Division of Daylor-Wharton Company, Harsco Corp.) in the manner further described below.

In detergent composition A, the sodium sulfate, sodium carbonate and magnesium sulfate heptahydrate were mixed together and comminuted in the Kitchen Aid blender. Thereafter, the nonionic surfactant was added to the comminuted particulate matter to form a detergent mixture. The detergent mixture was then transferred to the "V" blender where diatomaceous earth and Britesil H-24 were subsequently added, followed by approximately 15 minutes of mixing.

Detergent composition B was prepared by charging the Kitchen Aid blender with sodium sulfate and sodium carbonate, comminuting the charge followed by the addition of water (4% w/w) finally followed by the nonionic surfactant with continued blending. The resulting detergent mixture was thereafter transferred to the "V" blender where diatomaceous earth and Britesil H-24 were subsequently added, followed by approximately 15 minutes of further mixing.

The nonionic surfactant bleeding rate of the resulting compositions was determined with the aid of a Modified Ong Test. The Ong Test is described in U.S. Pat. No. 4,328,114.

In the modified form of said test as employed herein, 9 pre-weighed blotters consisting of ashless No. 42 filter paper were used per experimental test.

All filter paper blotters were cut to fit snugly around the inner circumference of a 150.times.75 mm. evaporating dish. Three pre-cut blotters were initially placed upon the bottom of the evaporating dish, followed by an approximately 133 grams layer of the detergent powder. A further layer of three blotters was placed upon such detergent powder layer followed by another detergent powder layer of approximately 133 grams. The foregoing procedure was repeated a third time whereby three distinct layers of detergent powder in cylindrical form each separated from the layer immediately above it by a layer of three blotters was obtained, wherein the bottom layer was not in direct contact with the bottom of the evaporating dish but through an intervening layer of three blotters. The upper surface of the uppermost detergent powder layer was not covered by any blotters.

The entire assembly was sealed with Parafilm brand (American Can Company) wrap and subjected to the test temperature of 95.degree. F. The aforementioned temperature, being somewhat higher than the ambient temperature prevailing under normal storage conditions was intended to speed up the usual rate of nonionic surfactant bleeding.

In each case, the amount of nonionic bleeding was calculated from the total increase in weight of all 9 blotters at the expiration of each test time period.

Table 2 noted below shows that detergent composition A containing magnesium sulfate heptahydrate exhibited a significantly lower rate of nonionic surfactant bleeding compared to detergent composition B which did not contain magnesium sulfate heptahydrate.

The foregoing experimental data show that more than twice as much nonionic surfactant was lost as a result of bleeding from detergent composition B as compared to detergent composition A comprising the magnesium sulfate heptahydrate of the present invention.

Following the general procedures noted for detergent composition A and detergent composition B, the further detergent compositions noted in Table 3 below were prepared. However, in the case of detergent composition C, the 4% w/w water required to hydrate the anhydrous magnesium sulfate was added to the batch in the Kitchen Aid mixer after the nonionic surfactant had been added thereto, and prior to the transfer of the pulverized detergent mixture to the "V" blender.

The four compositions noted above were subjected to the Modified Ong Test in accordance with the procedure described above. The results obtained are summarized in Table 4 below.

The foregoing results demonstrate that a 7.80% w/w quantity of magnesium sulfate heptahydrate was sufficient to inhibit nonionic bleeding from the detergent powder composition tested. In fact, in the case of compositions C and D, the amount of nonionic bleeding which was measured was substantially equivalent (and even superior in the case of composition C) to the results obtained with composition A which contained 20.48% magnesium sulfate heptahydrate.

It is also evident that composition C which contained magnesium sulfate heptahydrate formed in situ showed a significant retardation in nonionic bleeding compared to Composition D which employed magnesium sulfate heptahydrate initially.

Aged control composition F registered less nonionic surfactant bleeding than was the case with its freshly prepared counterpart control composition E. This difference in behavior can be explained by taking into account the loss of nonionic surfactant to the walls of the container of the aged product before it was removed therefrom for the Modified Ong Test evaluation.

The tests noted herein demonstrate the rates at which a nonionic surfactant bleeds out of a typical detergent composition. Accordingly, detergent composition G and detergent composition H were freshly prepared for further testing. Detergent composition G was an identical remake of detergent composition A, and detergent composition H was an identical remake of detergent composition B. The respective batches of detergent composition G and detergent composition H were each subdivided into five samples of 400 grams each, and each sample subjected to the Modified Ong Test for the respective test periods (at 95.degree. F.) noted in Table 5 below.

The data shown in Table 5 above demonstrate that most of the nonionic surfactant bleeding loss occurred during the first two to three weeks after the detergent composition was made. Once again, it will be seen that not only was the overall nonionic surfactant bleeding greater in the case of detergent composition H (which did not contain magnesium sulfate heptahydrate) but that the amount of such bleeding was greatest during the first two to three weeks following the making of such composition, and additional bleeding after this time was minimal or practically non-existent.

It is evident that magnesium sulfate heptahydrate not only retards the enhanced rate of bleeding normally encountered in the first two to three weeks following the preparation of a nonionic surfactant based composition, but is continues to retard such bleeding over the entire test period.

Further tests were conducted to investigate the utility of Na.sub.2 CO.sub.3.H.sub.2 O, polyvinyl alcohol (PVA) as well as workable and optimal lower use levels of magnesium sulfate. To that end, detergent compositions I, J, K, L, M and N as shown in Table 6 below were prepared following the general procedure used with compositions A and B. In compositions I and J, which contained magnesium sulfate, heptahydrate, the magnesium sulfate as it was initially employed was in anhydrous form, and it was hydrated after the addition thereto of the nonionic surfactant.

All of the above noted six compositions were subjected to the Modified Ong Test described previously at two different time intervals, and the results obtained are noted in Table 7 below.

The data reflected in Table 7 clearly demonstrate that the least nonionic surfactant bleeding was encountered in compositions comprising magnesium sulfate heptahydrate. Although the incorporation of polyvinyl alcohol showed some benefit especially at the higher use level of 3% w/w as compared to detergent composition N, it was nonetheless not as effective as magnesium sulfate heptahydrate on a comparable weight basis nor was its use as economical as the use of magnesium sulfate heptahydrate. However, detergent composition J containing 2.8% w/w magnesium sulfate (anhydrous) together with 1% w/w PVA was found to be as stable as detergent composition D containing 7.80% w/w magnesium sulfate heptahydrate.

Further tests were conducted to investigate the utility of Na.sub.2 SO.sub.4, Na.sub.2 CO.sub.3, Na.sub.2 CO.sub.3.H.sub.2 O, MgSO.sub.4.7H.sub.2 O and CH.sub.3 COONa.3H.sub.2 O. To that end, detergent compositions O, P, Q and R as shown in Table 8 below were prepared following the general procedure used with compositions A and B.

All of the above noted four compositions were subjected to the Modified Ong Test described previously at two different time intervals, and the results obtained are noted in Table 9 below.

The data reflected in Table 9 clearly demonstrates that the least nonionic surfactant bleeding was encountered in compositions comprising sodium acetate trihydrate while the most bleeding occurred with sodium carbonate monohydrate (whether added as is--composition P--or formed in situ--composition R).

Compositions O, Q and R contain the same amount of water in the form of different hydrates and are, otherwise, substantially similar in composition. When the equilibrium data (Table 9; 6 weeks) for compositions O and Q are compared to that for R as a reference, it may be concluded that sodium acetate trihydrate is slightly more efficient than magnesium heptahydrate on a weight basis for reducing nonionic bleeding.

In the above formulations, the total amount of nonionic in the 400 grams of sample used in the modified Ong Test is 400.times.0.0855 or 34.2 g. As a general rule, it is preferred that the amount of nonionic bleeding over a 6 week period as determined by the heretofore described modified Ong Test is below about 10% of the total nonionic surfactant present. Thus, the result for detergent composition Q, i.e. 2.9 g., is well below the preferred limit.

The minimum effective level of sodium acetate trihydrate in a particular formulation containing a nonionic surfactant will, of course, depend largely on the level of the nonionic surfactant present and, usually, to a much lesser extent on the other formulation ingredients. It will be within the scope of one skilled in the art to determine by routine testing what the minimum effective level is for a particular detergent formulation. In general, a ratio (w/w) of nonionic to sodium acetate trihydrate of 1 to about 0.9 may be sufficient although in some cases a ratio of 1 to about 0.4 may also be suitable, especially if a higher than 10% level of nonionic bleeding can be tolerated.

While greater quantities of sodium acetate trihydrate, may be employed if desired, in practice an upper effective limit is dictated both by cost considerations and by undue dilution of the detersive power of the resulting detergent compositions as will be apparent to persons of ordinary skill in the art to which the invention pertains.

While in all the compositions tested herein, the level of nonionic surfactant employed was 8.55% w/w, the amount which is used in practice may range from about 5% w/w to about 25% w/w. Moreover, a detergent composition may, in addition to nonionic surfactants contain other surfactants, e.g., those which are anionic (including soaps), cationic, zwitterionic and ampholytic. In such a mixed detergent composition, the actual amount of nonionic surfactant present may even be less than 5% w/w if the balance is made up by the other surfactants. But, in any event, the actual amount of nonionic surfactant employed will be largely determinative of the corresponding amount of sodium acetate trihydrate to be effectively employed in accordance with the invention.

The scope of the present invention is further defined by and should be read in conjunction with the appended claims.