There are many reasons why Landercoll™ HEC is an important component in water based paints for ceilings, walls and facades.
Application of paint should be smooth and easy, whilst spatter must be kept to a minimum. To achieve these attributes only a small amount of Landercoll™ HEC is necessary. Depending on the system being used, a concentration of 0.2 % – 0.5 % is typically required. The choice of Landercoll™ HEC types depends on the application and requirements. The most commonly used Landercoll™ HEC in coating materials are Landercoll™ HE,HEM and HEBE.
The inclusion of Landercoll™ HEC can improve the following properties of dispersion paints:
• Rheological properties such as leveling and spattering
• Storage stability
• Open time
• Hiding power
• Film formation
The following properties of Landercoll™ HEC are essential for the optimization of coating materials:
• Thickening / Adjustment of consistency
• Water retention
• Function as a protective colloid
• Binding power
Thickening / Adjustment of Consistency
Technically, the most important property of Landercoll™ HEC is its capability to increase the viscosity of liquids and thus to act as a thickener. The thickening eﬀect of Landercoll™ HEC strongly depends on its concentration.
Furthermore, the inﬂuence of the degree of polymerization on the thickening eﬀect of Landercoll™ HEC can be clearly seen. With all other parameters constant, the viscosity of Landercoll™ HEC solutions increases with an increasing viscosity level.
Aqueous solutions of Landercoll™ HEC show a pseudoplastic eﬀect (shear thinning), which means with an increase in shear rate, the viscosity of the solutions declines.
This pseudoplasticity is specifc to each Landercoll™ HEC type and the respective viscosity of the grade. High viscosity Landercoll™ HEC grades have a stronger shear thinning eﬀect than those of low viscosity.
Because of its thickening eﬀect in coatings, Landercoll™ HEC acts as a stabilizer for the dispersed components. The formation of serum, i.e. the tendency to precipitate displayed by insoluble components such as pigments and fillers etc., is slowed down or even stopped completely. As a result, the coating material is protected against slow sedimentation of its components and is also stable during storage
An important property of Landercoll™ HEC is its pronounced water retention capability. It prevents the water from penetrating into the absorbing substrate too quickly which results in a better adhesion to the substrate. To the greatest possible extent, the water will be retained in the coating material during drying. A uniform film formation is ensured and incipient cracking is avoided. Particularly in formulations with high pigment volume concentration, the water retaining eﬀect of Landercoll™ HEC ensures sufficient open time for application. Adequate water retention in paints depends mainly on the concentration and viscosity level as well as on the type and temperature of the substrate.
Function as Protective Colloid
Coating materials are predominantly dispersions of pigments and fillers in an aqueous medium. Landercoll™ HEC acts as a protective colloid by preventing the agglomeration of the solid particles. This leads to a better
storage stability and easier agitation of the paint. Due to its molecular structure and its specifc properties, Tylose is a highly eﬀective protective colloid. It is widely used in other application fields, such as polymerization, to avoid the coagulation of the polymer
Especially in distempers, Landercoll™ HEC acts as a binder by combining the solid particles and binding them to the substrate. Landercoll™ HEC has strong adhesive power, good dry binding power and dry adhesion.
For these reasons, Landercoll™ HEC ensures a good adhesion between the coating and substrate.
Dissolution time of a delayed solubility Landercoll™ HEC grade at various pH values
Landercoll™ products with delayed solubility are denoted with an additional ´S´. Delayed solubility Landercoll™ grades can easily be suspended in pH neutral water without forming any lumps. Adjusting the pH to alkaline values can eliminate the delayed solubility. Please note that the pH value should be adjusted after the Landercoll™ is completely dispersed. Raising the pH before dispersion results in lumps.