Effective stain removal: Ciba's Tinocat TRS KB1 oxidation catalyst is a gentle and cost-effective additive to laundry bleaching aids.

The use of laundry bleaching additives has been increasing significantly during the past several years. Ciba Tinocat TRS KB1, when added to laundry bleaching products, increases their effectiveness at low temperatures and reduces formulation cost because bleaching additives with Tinocat TRS KB1 make more efficient use of the chemicals inside. The result is a more effective product, and more satisfied customers, with the use of a product that in many cases "pays fox. itself."

Laundry additives based on oxygen bleach, in liquid or in powder form, were introduced several years ago especially as a color safe alternative to chlorine bleach. These products are now sold under a variety of names including "oxygen bleach for fabrics," "bleach booster." "color safe bleach" and "multi- purpose stain remover." These products are used to remove dirt and stubborn natural stains such as tea, coffee, fruit, wine, tomato and chocolate. They can be used in the wash, for soaking, or for direct spot treatment. In addition to laundry care applications, multi-purpose stain removers also claim to be applicable for removing stains from furniture, carpets and hard surfaces such as outdoor garden furniture and litter boxes. In addition to stain and spot removal, the products are also used to remove and prevent graying, dinginess and unpleasant odors, as well as for sanitizing.

The introduction of an oxygen-based, multi-purpose stain remover in the U.S. resulted in a worldwide boost in the market for oxygen-type bleaching additives. The market size for laundry bleaching additives is presently estimated to be about 5% of the laundry care market. The market for this profitable group of products is still growing and becoming more competitive.

The use of separate bleaches has been common in markets characterized by low washing temperatures, short washing cycles, dilute washing liquors and/or a high popularity of liquid detergents. Under all these washing conditions it is often difficult to achieve adequate bleaching performance by the bleaching system incorporated in the laundry detergent itself. In the case of liquid detergents, bleaching can only come from an adjunct. These markets typically comprise the U.S., Korea, Japan, Australia and southern Europe. However; even in western and middle Europe, where the washing conditions are traditionally distinctly different (front loading washing machines using higher washing temperatures and concentrated wash liquors), bleaching additives and laundry stain removers are increasing in popularity. The increasing popularity of bleaching additives in Europe is in part related to a trend to lower washing temperatures and a rising market share of liquid detergents, but also to the fact that these products are heavily promoted.

Options for Formulators

This article details bleaching additives in powder or granular form. These products contain a persalt, such as sodium percarbonate or sodium perborate. When dissolved in water, these persalts generate hydrogen peroxide, which is able to oxidatively destroy natural colorants present in stains, dirt and dinginess. Hydrogen peroxide also has a sanitizing effect. Many products use sodium percarbonate as the main active ingredient. Others contain a broad range of active components such as surfactants, enzymes, builders and fluorescent whitening agents. In these products, the level of perborate or percarbonate is often lower than the first type.

The basic components, which contribute to bleaching performance, are sodium percarbonate and soda ash. The latter works as a filler and pH booster, the bleaching power of hydrogen peroxide alone is best at high alkalinity. However, bleaching with percarbonate or perborate alone is not very efficient at low temperatures; i.e., satisfactory results are obtained only by using an excess of persalt. In order to make a more efficient use of the persalt in a laundry product, bleach activators like TAED, NOBS or DOBA have been introduced. The nature and mode of action of these activators has been described in the literature. (1) However, in various cases, especially at the lowest washing temperatures (15-30[degrees]C), dilute washing conditions and high washing pH, the effectiveness of activators is not satisfactory. TAED is used in several bleach booster powders and tablets in Europe.

Another way to increase the bleaching power of peroxides is the use of metal coordination complexes based on manganese or iron as catalysts for bleaching reactions with hydrogen peroxide. The key feature of these catalysts is that they can potentially produce very reactive species out of peroxide while requiring low incorporation levels since they are catalysts. In 2004, Ciba Specialty Chemicals launched Tinocat TRS KB1, a granulated manganese catalyst. The chemical structure of the catalyst is shown in Fig: 1. The basic features of this catalyst have been published. (2) Tinocat TRS KB1 improves the bleaching power of hydrogen peroxide, while the catalyst is as safe for dyes and fibers as current bleaching systems (based on percarbonate and TAED) that have become a market standard.

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Creating Cost-Effective Formulas

The use of Tinocat TRS KB1 in bleaching additives enables more cost-effective formulations than those formulated with bleaching chemicals sodium percarbonate, soda ash and TAED. Thus, similar or even better bleaching performance can be obtained for similar cost. This is possible since many bleaching additives contain a high level of sodium percarbonate (up to 100%), which can be reduced significantly when Tinocat TRS KB1 is used. At the same time Tinocat TRS KB1 itself is added in only small concentrations, so that the contribution to the cost stays within limits. In other words, reducing the percarbonate and/or TAED in the formulation contributes significantly to the cost of the introduction of Tinocat TRS KB1.

Ciba Specialty Chemicals conducted a large number of washing trials in which a bleaching additive of varying compositions was used in combination with a detergent. The level of percarbonate in the product varied from 15-75%, the TAED level from 0-5% and the Tinocat TRS KB1 level from 0-1%. The remainder of the formulation was soda ash. This constitutes a 3-dimensional formulation space. For each formulation, the cost can be calculated by using typical market prices for SPC, TAED, soda ash and Tinocat TRS KB1.

The bleaching performance of each formulation was tested for a tea stain on cotton in a washing trial at 30[degrees]C in a Linitest apparatus. Details on the conditions are given at the end of the article. In Fig. 2 the bleaching performance (given as bleaching index) for the various formulations is shown. The experimental data were smoothed by fitting them to a mathematical function (see below). The data show that increasing the level of percarbonate, TAED or Tinocat TRS KB1 leads to a higher bleaching index. However, within the present formulation space and the present laundry conditions, the increase in bleaching performance per invested dollar or euro is the highest for Tinocat TRS KB1. Thus, it is possible to formulate a higher performing product on the basis of Tinocat TRS KB1 for the same cost as a formulation without Tinocat TRS KB1. As shown in Fig. 3, a formulation containing 30% percarbonate, 69.5% soda ash and 0.5% Tinocat TRS achieves a better performance than a formulation comprised of only 60% percarbonate and 40% soda ash. In Fig. 4, a formulation containing 30% percarbonate, 69.25% soda ash and 0.75% Tinocat TRS KB1 performs similarly to a formulation containing 45% percarbonate, 50% soda ash and 5% TAED, while having a significantly lower cost.

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Additionally, if there is room for a more significant investment in a new formulation, Tinocat TRS KB1 can be used at incorporation levels of up to 1-2% on top of the original level of percarbonate in order to achieve even higher levels of bleaching performance, as illustrated in Figures 2-4.

Additional Benefits

Tinocat TRS KB1 has a number of benefits, which makes it attractive beyond its possibility to optimize the cost/performance ratio of a bleaching additive. As already noted, the use of Tinocat TRS KB1 allows for stain removal at lower temperatures (Fig. 5). A further benefit of oxygen-based formulations catalyzed by Tinocat TRS KB1 is that they can effectively bleach fugitive dyes in the wash liquor. If colored garments are washed, the clothes often release textile dyes into the wash liquor. These fugitive dyes may cause discoloration of other garments in the wash load. This phenomenon may happen by accident where a red sock ruins an entire load of white laundry items. However, more often consumers wash mixed loads of whites, white with colors and near white items. Then, after many wash cycles the white articles become grayish due to the accumulated textile dyes. By bleaching these dyes in the wash liquor, the whites are maintained better. This benefit is illustrated in Fig. 6 where the results of washing experiments are shown in which cotton fabric dyed with direct black 22 was washed together with white cotton fabric over five cycles. The same white cotton was used in each wash cycle and the black cotton was replenished after each cycle. The graying effect of the white fabric is clearly visible when no Tinocat is used while a significant reduction of graying is observed when laundered with Tinocat TRS KB1.

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This anti-graying benefit is visible for Tinocat TRS KB1 and percarbonate at low levels of 0.3-0.5 % and 5-10% in the additive product, respectively. In most cases, the oxygen product will be formulated to achieve the optimal balance between stain removal performance and cost, thus the added benefit of anti-graying from Tinocat TRS KB1 is at no additional cost to the formulator. Bleaching systems based on Tinocat TRS KB1 decolorize dyes in the wash liquor only, whereas dyes on the fiber are not affected beyond the level of percarbonate/TAED. (2)

A third benefit of Tinocat TRS KB1 is that it is fully compatible with enzymes like protease and amylase. Detergent enzymes are relatively sensitive to the action of bleaching systems. This sensitivity reduces their stain removal effectiveness, which can only be compensated by a higher level of enzymes in the laundry product or the use of special and more costly enzymes that are more stable towards bleach. Fig. 7 shows that the peracetic acid formed by the combined action of percarbonate and TAED has a significant negative influence on enzyme action, while the active species formed by Tinocat TRS KB1 do not negatively interfere with the action of protease and amylase. It is clear that there is a potential cost savings when Tinocat TRS KB1 is used.

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Conclusion

Ciba Specialty Chemicals introduced the oxidation catalyst, Tinocat TRS KB1, as a new cost-enabling ingredient for laundry bleaching additives based on persalts. This catalyst, which is gentle on dyes and fibers, makes a more effective use of the persalt present in such laundry products. In many cases the incorporation of Tinocat TRS KB1 allows for a reduction in the level of persalt and bleach activator and thus in those cases Tinocat TRS KB1 "pays for itself." The most significant benefit of Tinocat TRS KB1 is stain removal at lower wash temperatures of 20-30[degrees]C, while additional benefits of Tinocat TRS KB1 include anti-graying effects for white care claims, as well as compatibility with enzymes.

References

(1.) E. Smulders, "Laundry Detergents," Wiley-VCH, Weinheim, 2002, p. 80

(2.) F. Bachmann et al., 50th SEPAWA Congress, 2003, proceedings, p. 271.

Washing Conditions in Tests Used

Results are obtained under controlled laboratory conditions. Applicability to specific conditions of use requires full scale testing.

Fig. 2-4: In-wash application European conditions, 30[degrees]C, 60 rain main wash. Bleaching additive on top of detergent (with SPC 17%, w/o TAED). Water hardness 12[degrees]dH, pH=10.7.4.8 g/l base 1993 AATCC Standard Reference Detergent WOB cont. 17% Sodium percarbonate. 2.35 g/l bleaching additive/stain remover (40 g per wash). Liquor ratio 1:3.6.

5% stained cotton, 95% white cotton load. Bleachable stains: BC01 Tea stain. Wash, lx rinse (running tap water), spin dry, iron and measure brightness Y. The bleaching performance was determined for 52 different formulations using teastained cotton. Bleaching index: Y(ref. form. + detergent) - Y(detergent) = net effect of ref. form = 10, thus the detergent only has a bleaching index of 0, while the reference formulation has an index of 10. Results shown in Fig. 2-4 were smoothed, taking the best fit of the raw data to an analytical function: Bleach index = 265.40 * TRS + 3.54 * SPC + 52.10 * TAED + 744.57 * TRS * SPC + 5.80. where: TRS=parts TINOCAT TRS KB1 in the formulation, SPC=parts percarbonate in the formulation and TAED=parts TAED in the formulation

Fig. 5: As for Fig. 2-4, but 3.53 g/l bleaching additive. Composition of bleaching additive: 45% SPC, 55% soda ash, optionally with Tinocat TRS KB1

Fig. 6: In wash conditions USA: 35[degrees]C 12 min in Linitest. Liquor ratio 25:1, water hardness 10[degrees]dH, 1.6% black cotton EMPA 132, 49.2% white CO, 49.2% white CO/PES. Bleach booster formulation: 35% SPC, 65% soda ash, optionally 0.5% Tinocat TRS KB1, used in combination with a bleach-free detergent (1g/l)

Fig. 7: As for Fig. 2-4, but 4g/l AATCC detergent, 0.8 g/l sodium percarbonate (SPC), Optionally 47 mg/l protease enzyme or 37 mg/l amylase enzyme, Optionally 0.2 g/l TAED or 47 mg/l Tinocat TRS KB1.

Menno Hazenkamp

Ciba Specialty Chemicals Inc.

P.O. Box 1266

D-79630 Grenzach-Wyhlen

Germany

Johan Werner

Ciba Specialty Chemicals Inc.

Postfach

CH-4002 Basel

Switzerland