The present invention relates to a process for manufacturing a waterproofing membrane comprising:
a preparation of a composition comprising an acrylic polymer and titanium dioxide dispersed in a solvent;
coating a reinforcement layer by application of said composition on one side of the reinforcement layer;
having the coated reinforcement layer dried; and
an application of a bituminous mass on another side of said reinforcement layer.
The present invention relates also to a composition for a waterproofing membrane.
A process for manufacturing such a waterproofing membrane is known from US2006/0110996. The coated waterproofing membrane, obtained by the known process, has the property to reflect the solar rays due to the presence of titanium dioxide and allows to avoid exudation problems of the membrane due to the presence of a coating with an acrylic polymer as binder which is less sensitive to solar rays. So the coating forms as if to say a barrier against the solar rays so that the latter heat less the bituminous mass and the building on which the membrane is placed as a roof covering.
A drawback of the known membrane is that its reflectivity decreases over time. Indeed, the colour of the coating on the membrane changes from white to yellow so that the coating on such a membrane loses its reflectivity property over the years. Consequently, in the known waterproofing membrane, the oil contained in the bituminous mass may migrate more easily to the upper side of the waterproofing membrane because the membrane heats more up due to the reflectivity decrease. This oil migration phenomenon is called exudation and it further reduces the long-term whiteness of the waterproofing membrane. Also, pollution could be provoked if the oil will not remain in the crystalline phase of the bituminous mass and mix with rain water.