Use of the Hydrotrope, Appyclean 6505 in acidic rinse aid formulation Cédric ERNENWEIN, R&D manager, WHEATOLEO

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1 Use of the Hydrotrope, Appyclean An underlying consideration in I&I cleaning is finding solutions of minimal impact to the environment, including new molecules from renewable resources. Low foaming surfactants are commonly used in auto-dish apparatus and in many industrial applications. This type of molecules is mainly produced from natural or synthetic fatty alcohols by alkoxylation of a well-defined amount of ethylene oxide (EO) and propylene oxide (PO). These non-ionic surfactants are known to show cloud points depending on the EO/EP distribution and alcohol tail length. Furthermore, the temperature at which their solutions become cloudy is of critical importance for the cleaning process. Hydrotropes are also used to provide a clear and easy to use solution and to maintain performance of surfactant during application. Mainly hydrotropes are coming from fossil origin like the sodium xylen sulfonate. This work aims at presenting a new method developed to optimize on the one hand, the choice of surfactant, and on the other hand, the action of hydrotropes. The final goal is to improve efficiency of acidic rinse aid formulations without further raising high amounts of PEG surfactants. In recent years, the study of physical behaviour of simple surfactants compositions has become increasingly used and provides a criterion for surfactant selection. For example, measurements of surface tension are widely used as a method of characterising surfactants and selecting products for particular applications. Surface tension is a measure of the ease with which fresh surface can be formed. Here, we will start with discussion toward the evolution of dynamic surface tension and foam with concentration of surfactants, temperature and blends with hydrotrope. Then, we will discuss several practical tests in which glass objects were uniformly soiled (with KOH solution) and rinsed by acidic formulations containing low amounts of PEG surfactants. The effectiveness of acidic rinse was evaluated both visually (spotting, filming formation) and with computational picture treatments. Materials and methods Low foaming surfactants : For this study, we used two EO. alcohols of industrial grade: Name C-chain Average EO No. Average PO No. Cloud point ( C in 1% in water) Suppliers Berol C Akzo-Nobel Triton DF x y 36 C Dow Chemical Table 1 : low foaming surfactants dedicated to rinse-aid formulations Hydrotrope : Appyclean 6505 is a new alkyl polyglycoside by WHEATOLEO. It s INCI name is Amyl-Xylsoides, and it s built with natural starting materials (alcohols for the lipophilic tail and sugars for hydrophilic head). Amylic alcohols comes from bio-ethanol process (from beet) and C5 sugars from wheat or corn by-products.

2 Dynamic surface tension: The dynamic surface tension was performed using a maximum bubble pressure tensiometer Krüss BP2. The maximum pressure to produce air bubble at the outlet of a defined capillary is directly proportional of the surface tension 1. = γ 0 γ (in mn/m) A freshly formed interface of a surfactant solution has a surface tension, γ, very close to that of the solvent, γ 0. Over a period of time, γ will decay to the equilibrium value, γ eq, value reached when adsorbing flux of surfactants monomers to the surface is equal to the desorbing flux, and this period of time can range from milliseconds to days depending on the surfactant type and concentration 2. Thus, by maximum bubble pressure measurements, we can study dynamic behaviour of surfactants in the region of 5 to millisecond range, where efficiency and effectiveness of acidic rinse aid must be optimum. Dishwashing test: To simulate an automatic dishwashing process, we use a loop circulating bath equipped with a pump (180 l/h), specific nozzle in order to spray fine droplets on microscope slides. In the first step, the slides were uniformly soiled by immerging them in a 5% KOH solution during 20 minutes at ambient temperature. After, the rinsing solution were sprinkled during 1,5 minutes at the same temperature or at 70 C. Finally, the glass slides were dried in a oven (80 C) before evaluation. First evaluation consists in optical marking (0 to 10) by observation of the numbers of spots or the formation of films. The second method is a computer s quantitative evaluation. All slides are scanned and the resulting image is treated by software (like Photoshop) to obtain a binary image (white pixel for the spots and black for the shiny glass). Finally, the Imagetool for windows software allow an account of black/white pixels and give the percentage of spots in the slides. 1 a) Miller, R., Fainerman, V.B., Schano, K.-H., Hofmann, A., Heyer, W., Tenside Surf. Det., 34, (1997); b) Christensen, T.C., Janule, V.P., Proc. 5th World Surfactants Congr., (2000) 2 Eastoe, J., Dalton, J.S., Advances Colloid Int. Science, 85, (2000)

3 p (mn/m) Use of the Hydrotrope, Appyclean 6505 Results and discussion Effect of Appyclean 6505 on the dynamic surface tension of detergents. Berol 260 is a narrow-range non ionic surfactant; it give low foam volumes (20 mm in Ross Miles test at 50 C and 0,05 %). The static surface tension of a 0,1 % w/w solution is 27 mn/m at 25 C measured with the Du Noüy ring. In figure 1 the dynamic surface tension reduction of Berol 260 at 0,5g/l with addition of increasing concentration of Appyclean 6505 (named ASF5 here) are represented Berol 260 0,5g/l Berol260 0,5g/l ASF5 1g/l Berol 260 0,5g/l ASF5 2g/L Berol260 0,5g/l ASF5 5g/L ASF5 5g/l Surface Age (ms) Figure 1 : Dynamic surface reduction at 25 C, 0,5g/l Berol260 and with 1, 2 and 5g/l Appyclean In reference : Surface reduction with 5g/l of Agppyclean On figure 1, we show that it is possible to improve Berol 260 effectiveness by addition of 1 to 5 g/l of the poorly surface active Appyclean 6505 (ASF5). This phenomenon drive us to say that, since Appyclean 6505 show poor activity on dynamic surface tension, it is eventually able to raise the Berol 260 monomers diffusion from the bulk into the surface where they directly adsorbs. We also demonstrated in figure 2 that this effect is dose dependant.

4 Foam volume (ml) p (mn/m) at 0,1s 28 27, , , , , [ASF5] (g/l) Figure 2 : Surface reduction at 25 C of 0,5g/l Berol 260 with addition of Appyclean 6505 after 0,1s. It is well known that efficiency of EO alcohol surfactants decrease with the temperature above the cloud point 3. This is presumably due to the decrease of water solubility. Foam behaviour further demonstrates this phenomenon (figure 3) C 35 C 60 C time (mn) Figure 3 : Foam volume (Ross Miles test) of 1g/l Berol 260 (cloud point C) Appyclean 6505 is able to maintain efficiency of EO alcohol even when raising temperature (table 2) or soda concentration (figure 4), both effective way to decrease EO alcohol solubility. 3 A.Schrem, D.Miller, W. Skypzak, Cesio 2004.

5 p (mn/m) Use of the Hydrotrope, Appyclean A B C Surface Age (ms) Figure 4 : Dynamic surface reduction at 25 C, A : 0,5g/l Berol260; B:0,5 g/l Berol ,5g/l NaOH; C: 0,5g/l Berol ,5g/l NaOH + 5g/l Appyclean Surface reduction ( ) at 0,1s T ( C) 0,5g/l Berol 260 0,5g/l Berol ,5 g/l NaOH 0,5g/l Berol ,5 g/l NaOH + 5 g/l Appyclean ~ 23,5 ~ 23,5 ~ ~ 23,5 ~ ~ 30 ~ 30 ~ 32.5 Table 2 : Evolution of the surface reduction at 0,1s depending of the formulation and the temperature. The results obtained with the Triton DF16 are appreciably the same ones as previously. Nevertheless the influence of the Appyclean 6505 is less significant. To obtain good rinse effect, glasses need to be wetted by a thin water film that evaporates without any residues. Low surface tension indicates good wetting properties. Appyclean 6505 can lower the surface tension of EO alcohols, especially in the low age of surface region. This characteristic is very important when fluids are to be sprayed onto surfaces 4. A lowering of surface tension in spray liquid is known to decrease droplet size. Moreover, two main factors rule the impact drop phenomena: the absolute dynamic surface reduction at low time (approx. 5ms) and the adsorption kinetics of the surfactant. 4 a) N.Mourougou-Candoni, B. Prunet-Foch, F. Legay, M.Vignes-Adler, K.Wong ; J.Coll Inter.Sci, 192, (1997) b) R.Crooks, J.Cooper-Whitez, D.V.Boger, Chemi.Eng.Sci, 56, (2001) c) M.C Butler Ellis, C.R Tuck, P.C.H Miller, Coll Surf A, 180, (2001)

6 Visual score Use of the Hydrotrope, Appyclean 6505 Effect of the Appyclean 6505 during the dishwashing process. We tried to exploit the synergistic effect of Appyclean 6505 during the dishwashing process, especially at the rinse and drying moment. The glass slides soiled with the KOH solution shows whitish marks highly visible (in this case the visual score is 0). The rinsing with only water showed the biggest level of spots and films (visual score of 3). The effect of Appyclean 6505 was demonstrated in a solution of Triton DF16 in acidic condition. The addition of citric acid to the nonionic surfactant gave unclear solution and then a formation of spot and film on the glass. Appyclean 6505 can keep clear solution, and increased the efficiency of the triton DF16. Figure 5 shows the scores obtained during the rinse aid test A B C D E Figure 5 : Rinse aid test results at 25C. A:Water, B: 0,1g/l Citric acid, C:0,1g/l Appyclean 6505, D:0,1g/l Triton DF16 + 0,1g/l Citric acid, E:0,1g/l Triton DF16 + 0,1g/l Citric acid + 0,05g/l Appyclean white bar for clear solution and hatched for the unclear. Results obtained after scanning and computer evaluation are slightly different (table 3). Calculation with citric acid alone gives worst results than visual observation which give 24 % of white pixels (i.e the marks). Results with the main surfactant cumulate the marks both due to KOH and surfactant residues. Addition of ASF5 increases the solubility of Triton DF16 and gives the best formula.

7 Rinse aid formulation 0,1g /l Citric acid 0,1g/l Triton DF ,1g/l Citric acid 0,1g/l Triton DF ,1g/l Citric acid + 0,05g/ Appyclean 6505 Score % white marks Scanned (left) and treated (right) images B D E Table 3 : Rinse aid test result Treatment of scanned image with Imagetool for Windows and calculation of % White pixel. The test realised with Berol 260 gives the same tendency (table 4). Rinse aid formulation 0,1g /l Citric acid 0,1g/l Berol ,1g/l Citric acid 0,1g/l Berol ,1g/l Citric acid + 0,05g/ Appyclean 6505 Score 7 6 7,5 % white marks ,5 Scanned (left) and treated (right) images B F G Table 4 : Rinse aid test result Treatment of scanned image with Imagetool for Windows and calculation of % White pixel. The over dosage of surfactant leads to filming, thus the score obtained with 0,2 % of triton DF16 in acidic formulation with Appyclean 6505 (to obtain a clear formulation) is of 7 (approx. 40% of marks) in comparison with the notation of 8 (with less than 10% of marks) at 0,1%. By increasing temperature (ambient to 70 C), the formulation E become cloudy and thin films residues still visible on the glass; thus, visual score decreased from 8 to 6,5. Raising temperature necessitate to add more Appyclean 6505 for optimum appearance of formulations.

8 Conclusions Appyclean 6505 is a hydrotrope obtained with agricultural by-products. It fulfils environmental criterion of E.U. and most of ecological labels. His main use is to increase solubility in diluted or concentrated formulations. By maximum bubble pressure measurements, we demonstrated that Appyclean 6505 could increase the efficiency of the low foaming surfactants (a narrow range EO alcohol and a EO/PO alcohol) in the millisecond region. These properties influence the characteristics of sprayed liquid and leads to a reduction of the droplets size. All of this physical characteristics improves the rinsing and drying process. After impact onto the solid substrate, low surface tension allows good wetting, also at low concentrations of surfactant. Formulation with Appyclean 6505 furnish clear diluted solutions with optimum appearance of the washed glasses. By the mean of specific tests, we demonstrate that Appyclean 6505 increase cloud point of surfactants, improve efficiency of acidic rinse aid formulation while it maintain a very low foam level.