Advances in Sustainable Automatic Dishwashing Synergistic Cleaning Effects Between Conventional and Biobased Ingredients

Transcription

1 R. Nolles* Advances in Sustainable Automatic Dishwashing Synergistic Cleaning Effects Between Conventional and Biobased Ingredients Following the European Commission regulation (1) to restrict the use of phosphorous compounds in consumer laundry and by 1 January 2017, i.e. household automatic dishwasher (ADW) detergents sold on the European market have to be almost phosphorous free: max. 0.3 grams total P. This requires re-formulation. As a consequence, more sustainable formulations are developed and novel, biobased ingredients will be incorporated. Carboxymethyl inulin is one of those novel ingredients that can contribute to the development of high performance and cost-effective ADW detergents. Synergistic cleaning effects with biobased co-builders To develop automatic dishwasher detergent formulations that meet the upcoming European Commission regulation on the restriction of phosphorous, synergistic cleaning effects between conventional and biobased ingredients are useful. Carboxymethyl inulin (CMI) is one of those novel, biobased ingredients that can contribute to the development of high performance and cost-effective detergents. Lab studies have indicated that CMI is synergistic with ingredients like sodium citrate, green chelating agents and polyacrylates. This know-how was implemented in various automatic dishwasher detergent formulations and their efficacy to prevent filming and spotting in the rinse phase was examined. The outcome of the experiments shows that in general performance ingredients (chelating agents, polymers, etc.) are required to obtain cleaning results comparable with standard STPP based tablets. By selecting the right combination of conventional and biobased ingredients, even better results on spotting and filming were found at equal or lower cost. The use of CMI in a citrate/carbonate based formulation contributes to achieve the desired cost-performance. And, because of its excellent sustainability and safety profile, CMI is suitable for use in Ecolabel and/or Ecocert formulations. Effectiveness of CMI in the dishwashing process CMI (Carboxyline, Cosun Biobased Products) is a so-called co-builder or threshold scale inhibitor (2). Moreover, it is an anti-redeposition agent for use in ADW and laundry detergent formulations. Biopolymers like CMI tend to be absorbed on individual particles and on growing scale crystals. Whereby substoichiometric quantities of inhibitor prevent scale formation and the action of these substances will be defined as threshold inhibition. Threshold inhibition can act through dispersion, sequestration, scale crystal distortion, or a combination of these. In an ADW detergent the co-builder contributes to prevent scale formation on the heating element of the machine. In addition, the use of a co-builder suppresses filming and spotting, particularly in the rinse phase when most of the (precipitating) builders are gone. And last but not least, the dispersing power of CMI will prevent re-deposition of removed dirt particles back onto the cleaned dishes. Synergistic effects between conventional and biobased ingredients As part of the general research program, the Cosun R&D lab studies synergistic effects between CMI and other ingredients used in detergent formulations. These other ingredients can be both conventional (fossil based) or biobased. The use of synergies allows formulators to benefit maximally from the chemistry applied, resulting either in improved performance or reduced cost, or both. Three examples of useful synergies for ADW detergent formulations are introduced below. Synergy of CMI with sodium citrate Sodium citrate is a weak sequestering builder. In combination with a precipitating builder like sodium carbonate it forms an economic basis for ADW detergent powders or tabs. The presence of sodium citrate can support CMI to perform better as a threshold scale inhibitor. This is shown in Fig. 1. The use of 3 5 ppm CMI as sole inhibitor results in approx. 80% inhibition. The use of the same amount of CMI in an environment containing 25 ppm sodium citrate shows an improved scale inhibition of approx. 90%. This increase is significant and considered to be the result of synergistic behaviour. At a dosage level of 25 ppm, sodium citrate by itself does not show any scale inhibition effect. 50 SOFW-Journal

2 Synergy of CMI with chelating agents Also with strong sequestering builders or chelating agents like methylglycinediacetic acid (MGDA), glutamic acid diacetic acid (GLDA) and ethylenediaminedisuccinic acid (EDDS) synergistic effects with CMI are observed. More specific, a clear difference is seen in the time elapsed before scale formation occurs. From the results of the experiment described in Table 1 it can be concluded that a relative high dosage of sequestering builder alone (1500 ppm) is required to delay scale formation up to 3 hours. When the concentration of the builder is reduced, scale is being formed rather quickly (within 1 hour). However, when CMI is introduced to the system scale formation can be delayed up to 3 hours with a lower total amount of chemicals: 863 ppm of the builder blend instead of 1500 ppm of the pure builder. (Remark: The duration of wash programs in household laundry and/or ADW machines tend to increase in order to save water and energy.) Fig. 1 Static CaCO3 inhibition test of sodium citrate I and CMI. Conditions: 11 dh (approx. 200 ppm calcium hardness), ph 8.5, T=50 C; t=22 h. Synergy of CMI with polyacrylate Finally, combining CMI with conventional acrylic polymers shows an improvement in scale inhibition too. This probably is due to differences in the inhibition Builder (ppm active) t = 0 t = 1 h t = 2 h t = 3 h ± ± Builder + CMI (ppm active) t = 0 t = 1 h t = 2 h t = 3 h = no scale formation, ± = some scale formations, - = scale formations mechanism of CMI and polyacrylates. Apparently this works complementary. Fig. 2 shows that the blend of 75% CMI and 25% polyacrylate outperforms the Table 1 Static CaCO3 scale inhibition test of chelating agent alone (upper part) and of chelating agent in combination with CMI (lower part), respectively. Conditions: 25 dh (approx. 450 ppm calcium hardness), ph 10, T=60 C individual ingredients (when dosed at the same active level). This effect was observed for different CMI-polyacrylate ratios. The use of synergistic effects between ingredients can help to improve the overall performance of automatic dishwashing detergent formulations, or allows formulators to develop well-performing detergents at a lower cost. Implementation in automatic dishwasher detergent formulations Builders and co-builders have different purposes in a detergent formulation. Builders are used to soften the water and bind certain free metal ions. Co-builders are added to inhibit crystal growth and disperse (dirt) particles. Uniting these functionalities in one formulation generally results in a better overall performance of the detergent. In other words, builders and co-builders are complementary (Fig. 3). The three abovementioned synergies were brought together in a complete ADW detergent formulation. SOFW-Journal

3 Fig. 2 Static CaCO3 inhibition test of polyacrylate and CMI. Conditions: 20 dh (approx. 350 ppm calcium hardness), ph 10, T=60 C, t=1h In the example described in Table 2, the starting point for the development of the formulation is a combination of sodium citrate and sodium carbonate as a base (approx %). These builders will provide decent water softening and are quite economic. The performance of the builders can be boosted by the use of chelating agents (non-precipitating) and co-builders (polymers). In this case MGDA, polyacrylates and CMI are used. The remaining ingredients are kept constant in the formulations. These are the sodium percarbonate/taed bleach system, low foaming surfactants and enzymes (protease and amylase). If required, sodium sulphate is used as an inert to complement the formula to 100%. The example shows the performance of (A) a very basic formula versus (B) a formula with a high content of MGDA versus (C) a cost optimised formula containing CMI and (D) a performance optimised formula also containing CMI. A standard commercial STPP-based tablet is used as a reference. For the different formulations the relative cost price is determined using actual raw material prices from the market. The material cost price of formulation B (containing a high amount of MGDA) is normalised to 100%. The basic (budget) formulation A has a relative cost price that is approx. 27% lower than formulation B. The cost optimised formulation containing CMI (formulation C) is approx. 7% more economic than formulation B. Results The different formulations from Table 2 were tested following the rinse aid Cost of the formulation protocol for ADW (see text box). The results of the visual judgement on spotting and filming after 6 washes are shown in Fig. 4. The major difference in the results is found on spotting. The budget formulation A only shows a fair performance compared to the good result of the other formulations and the reference tablet. More specific, the performance of formulation A is particularly poor on glass. Furthermore, on spotting formulations B and C perform more or less similar to the reference tablet, although the reference tablet shows a better result on plastic. The difference in the results on filming is less obvious. Even the budget formulation seems to perform decently. However, an important note is that filming is harder noticeable when spotting is severe (and the other way around). Another relevant observation is that the reference tablet performs Cleaning performance Fig. 3 Builders and co-builders are complementary ingredients for detergents 52 SOFW-Journal

4 Fig. 4 Results of the ADW rinse aid test: average score on spotting (upper part) and on filming (lower part) Ingredients Part (weight-%) A B C* D Sodium citrate Sodium carbonate Sodium percarbonate MGDA (78% active) Acrylic polymers (90% active) CMI (45% active) TAED Surfactants Enzymes Sodium sulfate q.s. q.s. q.s. q.s. Reference Commercial tablet (STPP based) Relative cost price** unknown Overall performance poor-fair good good very good fair-good * The performance of formulation C can be improved by adjusting the amount of polymers and/or surfactants. Guideline formulation D is the result of that. ** The material cost price of formulation B is normalised to 100% Table 2 ADW detergent formulations poorly compared to the other formulations on filming on glass, ceramics and knives. And last but not least, a further optimized formulation D outperforms all other formulations as well as the reference tablet. It is particularly good to prevent spotting on glass and filming on plastic and ceramics. CMI is sustainable and safe CMI has an excellent sustainability and safety profile. It is partly renewable and is ultimately, but inherently biodegradable. The fact that CMI is inherently biodegradable gives the polymer a certain amount of microbiological stability, which is beneficial for formulation stability. Moreover, CMI is 100% phosphorous and nitrogen free. Hence, it is suitable for use in Ecolabel and/or Ecocert formulations. 54 SOFW-Journal

5 SEPAWA SLI-151 COSUN-123 Detergents Conclusions and discussion To develop automatic dishwasher detergent formulations that meet the upcoming European Commission regulation on the restriction of phosphorous, synergistic cleaning effects between conventional and biobased ingredients are useful. Lab studies have indicated that CMI is synergistic with ingredients like sodium citrate, green chelating agents and polyacrylates. By selecting the right combination of biobased and conventional ingredients even better results on spotting and filming in automatic dishwashing experiments are obtained at equal or lower cost. Moreover, the outcome of the ADW rinse aid tests shows that in general performance ingredi- ents (chelating agents, polymers, etc.) are required to obtain cleaning results comparable with standard STPP based tablets. On the contrary, it can be concluded that formulations not containing any performance ingredients are underperforming. The use of CMI in a citrate/carbonate based formulation contributes to achieve the desired cost-performance. An additional benefit of partial replacement of strong chelating agents by CMI could be a reduced risk of glass corrosion caused by ion exchange on the surface of the glass. However, this effect was not covered in this study. Finally, because of its excellent sustainability and safety profile, CMI is suitable for use in Ecolabel and/or Ecocert formulations. References (1) Annex VI a of REGULATION (EU) No 259/2012 of 14 March 2012 amending Regulation (EC) No 648/2004 (2) G. van Engelen, R. Nolles, Clean products from a clean planet for a clean future, SOFW- Journal 136 (2010) 10, *Author s address: Robert Nolles Marketing & Sales Manager Cosun Biobased Products P.O. Box MG Breda, The Netherlands robert.nolles@cosun.com n AZ_SLI_2013_HR:SLI :17 Uhr Seite 2 Biobased cleaning, phosphate free from chicory roots Don t miss Mr. Robert Nolles SEPAWA lecture / Cosun Biobased Products. Wednesday, 9th October 2013, a.m., hall 2 SOFW-Journal Insterburger Strasse Frankfurt am Main Telephone: +49 (0) Fax: +49 (0) info@slichemicals.com