Keramag Uses Bayer MaterialScience Polyurethanes For Its Premium Bathtub

"F1", the premium bathroom range manufactured by Keramag AG in Ratingen, Germany, features dynamic lines and innovative styling. It was developed in cooperation with F.A. Porsche Design. A key quality characteristic of the new range is the use of modern materials and state-of-the-art processing. And the "F1" bathtub is made using not one but two modern polyurethane materials from Bayer MaterialScience AG - the new Multitec® Short Fiber Spraying polyurethane spray system and the microcellular rigid integral skin molded foam Baydur® 60. These materials not only give designers a lot of freedom, they also meet the high stability requirements applying to bathtubs.

The tub shape is produced by thermoforming a thermoplastic film - in this case acrylic - and then reinforcing the reverse side using the new Multitec® Short Fiber Spraying polyurethane system. This typically consists of an isocyanate, a fast-reacting and a slow-reacting polyol and an optional foam additive, and is applied to the reverse side of the film at room temperature in several layers together with cut glass fibers 12 millimeters long. It only takes three to five minutes for the sprayed-on reinforcement to cure.

"This saves a lot of time compared with the conventional method, which involves reinforcing the reverse side using a time- and labor-intensive hand lay-up process with unsaturated polyesters and cut glass fibers," says Dr. Marc Schütze, a polyurethane expert at Bayer MaterialScience. "A further disadvantage of the traditional manufacturing method for glass fiber-reinforced systems is the use of styrene as a solvent and co-reactant. The maximum workplace concentration value for styrene was recently lowered quite considerably."

The "F1" bathtub is manufactured under contract by DECS Kunststoff- und Gerätetechnik GmbH.

"The Multitec® system allows extremely cost-effective and versatile processing," says Ulrich Krämer, Managing Director of DECS.

The company uses the polyurethane CSM (Composite Spray Molding) spray technology of Hennecke GmbH, a wholly-owned subsidiary of Bayer MaterialScience. The technology was developed specifically for processing reinforced and non-reinforced polyurethanes using the spraying process. Spraying into the open mold and curing in the open air mean that only one half of the mold is required and, given the limited stresses, this can be made from a synthetic resin. The result is a significant reduction in investment costs, partly due to the fact that the mold carrier is no longer required either. Consequently, the use of polyurethane CSM spray technology is particularly suited to the cost-effective manufacture of larger molded parts or small to medium production runs.

The base of the Porsche Design bathtub is made from Bayer MaterialScience’s Baydur® 60 rigid polyurethane integral skin foam, which is supplied by the polyurethane system house Büfa Polyurethane GmbH & Co. KG.

"If you consider the large size of this component - one meter by two - the advantage of this lightweight polyurethane material immediately becomes apparent," says Ulrich Krämer. After curing, the component can support considerable loads. The material can be painted using several methods and its high-quality surface satisfies all the esthetic requirements of modern bathroom design. A further feature of Baydur® 60 is its very low water absorption which means that the tub can occasionally "get its feet wet".

The base is made in one shot in a closed aluminum mold. The connections for joining the base to the upper part of the bathtub - a tongue-and-groove system - are molded into the design to give a perfect fit.

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