Two in one
When the subject of polyurethane soling comes up, one may automatically think of DESMA. This is because the German manufacturer has been the major supplier of PU moulding machines for 50 years.
It has also been the leading innovator in PU soling technology. A prime example of this is the DESflow process introduced in 2012 by which a colourant could be premixed with natural PU immediately prior to it being injected into the mould cavity.
Another German company with a long and successful track record of supplying PU and TPU polymers for a wide range of footwear is chemical manufacturer BASF. Besides supplying raw materials, BASF also develops highly functional surface solutions at its Coatings division. The two companies have now jointly announced NovaCoat-D, a new and radically different process for adding a coloured skin to direct moulded PU soles which, at the same time, also acts as a release agent to ensure easy extraction of the shoe once the moulding cycle is complete.
The process involves spraying a coating of NovaCoat-D into the mould cavity in the same way that a mould release agent is applied except, in this instance, the spray forms a coloured film on the inside of the cavity which chemically bonds to the injected polyurethane foam of the sole. By the time the moulding cycle is completed, it has become a permanent part of the outer skin of the finished sole. The chemistry BASF has used is clearly an excellent innovation as it also acts as a mould release which it says provides easy de-moulding with no further processing necessary.
Furthermore, the company says that it is compatible with many polyurethane foams and produces a tough and flexible finish. It also offers a number of extra benefits as it makes the sole more resistant to scuffs and scratches, as well as UV light and dirt. It is apparently also able to cover up small imperfections on the surface of the moulded sole which is another useful feature. Applied by the specifically upgraded former release agent robot attached to the table of a rotary moulding machine, the spray is available in a wide range of colours and offers finishes ranging from glossy to matte depending on the exact chemical composition and mould design.
DESMA says that it can cope with the fast cycle times of round table moulding machines and that most of its machines can be upgraded to integrate the application of NovaCoat-D in the moulding process. The best way to do this is to test it and, to this end, DESMA has a team at its headquarters in Achim which is carrying out testing in conjunction with BASF teams in Asia, Europe and North America prior to conducting trials together with interested parties. However, as a first step, it is recommended that initial trials are made in order to check the compatibility of the coating with the foam the customer is currently using. This can be carried out either at one of BASF’s technical centres or by DESMA if the main focus concerns automated processing. After this initial validation, further tests can then be carried out using one of the following standard coatings, Clearcoat 5KG, Orange metallic 5KG, Purple metallic 5KG, together with the necessary NovaCoat-D hardener.
This is a clever concept from two companies with strong reputations for both innovation and quality products so there can be little doubt that it will do all that they claim. By combining two operations in one, the process further streamlines the manufacture of polyurethane direct moulding for footwear as well as adding extra benefits in terms of finish, aesthetic appeal and abrasion resistance to an already successful soling material.
Credit: DESMA
