Industry News

Wacker Develops VOC-free SILRES® BS POWDER S for Gypsum Dry-Mix Mortars

Published on 2013-05-23. Author : SpecialChem

Munich -- Munich-based chemical Group WACKER has developed a novel additive for rendering gypsum-based dry-mix mortars hydrophobic, i.e. water-repellent. Sold under the name SILRES® BS POWDER S, the powder is highly efficient and free of volatile organic compounds. The water repellency develops as soon as the construction material has set. Furthermore, gypsum dry-mix mortars formulated with SILRES® BS POWDER S can be mixed with water very quickly without generating any dust.

Gypsum-based construction materials that are formulated with SILRES® BS POWDER S are thoroughly water-repellent, as the droplet test shows. The gypsum plaster is protected against water and thus against irreparable damage.

Moisture can do irreparable damage to gypsum building materials. To prevent this and to protect the set gypsum mortar against moisture, powder-form water-repellent agents are admixed with the dry-mix mortar. This requires the use of carrier or encapsulation materials as a way of converting the conventional liquid active ingredients into a powder. These auxiliary materials delay the onset of the hydrophobic effect of the liquid water-repellent until the gypsum mortar has been mixed with water and has set. However, conventional powder-form water repellent agents have the disadvantage that they are composed almost entirely of carrier material. The actual active ingredient makes up only a few percent of the total weight. This is not very efficient from the perspective of both weight and costs.

The solution here is to use SILRES® BS POWDER S. The new additive for dry-mix mortars does not require any auxiliary materials, consists entirely of a novel active ingredient in powder form and, as such, is extraordinarily efficient. Just 0.2 weight percent of SILRES® BS POWDER S is enough to render gypsum construction materials water-repellent. Gypsum containing the new additive absorbs as much as 90 percent less water when set and so can be employed in bathrooms, kitchens, stairwells and garages. Gypsum-based wall plasters, joint fillers, top-coat materials, floor screeds, and adhesives that have been formulated with SILRES® BS POWDER S are thus suitable for use throughout house interiors.

SILRES® BS POWDER S consists of a methyl siliconate which is produced as a colorless, free-flowing powder by a special process. The active ingredient is inherently soluble in water, a property which confers excellent mixing properties when the mortar is being prepared. Nonetheless, the gypsum mortar turns water-repellent as soon as it sets. SILRES® BS POWDER S can be used with all types of gypsum, irrespective of the pH. It eliminates the pre-reaction times which are often needed by conventional powder-form water-repellent agents. Moreover, it can be used indoors, since it is environmentally friendly and releases neither alcohol nor volatile organic compounds (VOCs).

About SILRES® Masonry Protection Products

WACKER sells numerous silicone-based masonry protection agents under the name SILRES® BS. The raw materials and active ingredients are based on water-repellent silanes, silicone fluids, silicone resins and aqueous silicone emulsions. All products are primarily designed to make construction materials water-repellent, as a way of protecting them from moisture and thus from long-term damage.

Silicones form a strong bond to mineral surfaces, where they build up an extremely stable, long-lasting silicone network that is water-repellent, yet still permeable to water vapor. Silicones protect numerous mineral construction materials, ranging from facades, masonry, terracotta bricks and roof tiles, to thermal insulation materials, concrete, and gypsum products. Modern silicone resin emulsion paints also utilize the hydrophobic or water-repellent properties of silicone resins.


WACKER is a globally active chemical company with some 16,300 employees and annual sales of around €4.63 billion (2012). WACKER has a global network of 24 production sites, 22 technical competence centers and 53 sales offices.

Source: WACKER

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