Thicke - Deuteron GmbH

More documents

Recommendations

Info

DEUTERON GmbH in Achim sells since 30 years xanthan gums which more and more have found application in the coating industry through the years. The xanthan products are used all over the world as thickening agents and stabilisers for aqueous systems. The aim of this information is to help you make technical decisions about what xanthan products offered by DEUTERON GmbH are suitable for you. From a structural point of view xanthans are polysaccharides composed of ß-D-glucose units. Xanthan molecules are anionic due to the carboxyl groups on the side chains. Xanthan is therefore essentially an anionic heteropolysaccharide. These chemical features mean that xanthans are compatible with a broad range of anionic and non-ionic surfactants. Compatibility with cationic surfactants, for example the quaternary ammonium salts in DEUTERON conductivity agents, must be separately investigated if necessary but is not very probable The products listed here consist of xanthan gums which are partly swelling delayed, or which are modified with other bio polymers. For the easier incorporation pre wetted types are available with organic solvents . � Pseudoplastic (non-Newtonian) thickening agent. � Small quantities very effective � Very good pH resistance � High tolerance to organic solvents � Gel-formation possible � Easy-to-incorporate variants available � Dust-free liquid variants available The compact structure of the xanthans offered by DEUTERON GmbH mean that there is only a little dust formation and hence easy handling. For totally dust-free processing, use can be made of DEUTERON VT 855 and VT 856. These are flowable pastes of thickening agents. The xanthans of DEUTERON GmbH are pseudoplastic (thixotropic) thickening agents. Using these products it is possible to set specific flow properties over a broad working region, unlike the situation for other thickening agents commonly used in the paint/lacquer industry such as celluloses. The processing of the xanthans is preferably carried out under high shear forces using a dissolver. Here the dimensions of the stirrer blade, the dispersing vessel and the filling height must be optimal. The required rolling, laminar motion of the dispersing material in the vessel is only achieved by having the correct conditions and dimensions. Under no circumstances must the motion of the material be turbulent, rather a funnel must form (doughnut effect) so that the dispersing blade is still visible. Swelling behaviour of Deuteron XG in water Swelling behaviour of Deuteron VT 819 in water For the shown comparison 5 grams of product have been admitted to 100 g water. Without any stirring the photos have been done immediate after dosage.
In contrast to liquids with Newtonian behaviour, in which the shear stress increases or decreases in direct proportion to the shear rate, solutions of the swollen xanthans display a rapid decrease of the shear stress with increasing shear rate. With decreasing shear rate the shear stress continuously increases again. This corresponds to pseudo plastic (thixotropic) behaviour. If the shear forces are interrupted, the solutions of xanthans almost immediately assume their initial viscosity again. This can be seen in the graph from the almost congruent curve. This is typical behaviour for the xanthans from DEUTERON GmbH and for many technical applications this is an ideal precondition for customization of the rheological properties for specific users. . The distance of the legs of the curves to each other is a measure of the thixotropy of the solution. This behaviour is a fundamental prerequisite for producing coatings with very special properties. These include, for example, solid paints (whose viscosity drops on application) and plaster (here special stability is required on vertical surfaces) and many other potential applications. Viscosity (mPa.s) 2 200 2 000 1 800 1 600 1 400 1 200 1 000 800 600 400 200 0 increasing steigende speed Drehzahl decreasing sinkende speed Drehzahl 0 10 20 30 40 50 60 70 80 90 100 110 120 Revolutions per minute It hardly comes to viscosity changes at concentrations of 1% or more at temperature rise. At less concentrations (e.g. 0.3%) the viscosity becomes reduced. at temperature rise easily this can, however, be compensated for by adding of NaCl or other monovalent salts largely. This is different behaviour to the other standard thickening agents used in the paint/lacquer industry which on addition of monovalent metal salts tend rather to undergo viscosity loss. A viscosity increase or gel formation is therefore certainly not possible. Gel formation is possible in the presence of multivalent metal salts. The multivalent metal ions lead to cross linking and hence in some cases to a stable gel. The nature of the metal ion and prevailing pH of the system determine whether flexible or solid gels are formed. It is recommended to add the multivalent metal ions only at the end of the production process, otherwise there could potentially be problems during the production due to gel formation. The xanthans of DEUTERON GmbH in general do not swell in organic solvents. It is however possible to add organic solvents to already admixed systems. Up to 40% of these solvents can be tolerated here, with the xanthans having a largely stable viscosity. This compatibility does not apply for DEUTERON SR 28, and when using this product own tests must be carried out. Viscosity (mPa.s) 3000 2500 2000 1500 1000 500 0 DEUTERON XG 1% in water/isopropanol 0 10 20 30 40 Content of isopropanol (%) The solutions of swollen xanthans of DEUTERON GmbH are mostly stable to pH. There is almost no viscosity change in the region between pH 2 and pH 12. Viscosity stability is only an issue at extreme pH. This must, however, be individually tested for specific applications. The admixing of the xanthans should, however, be carried out in the neutral region and the pH subsequently adjusted. Viscosity (mPa.s) 1100 1000 900 800 700 600 500 Viscosity behaviour of DEUTERON XG (1%) at changing pH-values 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 pH-Values As DEUTERON SR 28 contains xanthan-galactomannan, It leads opposite pure xanthans to a higher basic viscosity, however, can influence the pH-stability unfavourable. Therefore the pH stability of this product must be checked for each individual use. Nevertheless there are a lot of possibilities. DEUTERON VT 819 is a swelling retarded xanthan variant which cannot be direct incorporated into the acid area. A value of pH 7 is required, the acidification can, however, be carried out after finished swelling. Biopolymers require a stabilisation against microorganism. This is possible with common biocides used in the coating industry.
Page 1: Thickening Agents INFO VT-0311/1E B

Thicke - Deuteron GmbH

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?