1. Field of the Invention
The invention pertains to a process and a device to moisten a layer of material (which can be referred to as a web of material), in particular, a moving layer of paper or cardboard.
2. Description of the Related Art
It is already well known that the qualitative properties of paper, in particular the shine, the smoothness and the dampness, can be influenced by adding steam through blower chests or steam moistening applicators to the calender, either along the machine running direction or transverse to it. The increase in moisture content that can be achieved by using pure steam is, however, limited.
A spray device, known from pamphlet WO 2007/003059 A1, utilizes a special nozzle at the calender, in order to add condensation to the steam, thus adding to the total moisture content of the steam that is applied onto a layer of material. Such a spray device can be used for cross profiling. The device does however tend to form droplets and lead to obstructions in the pipe which supplies the condensate, since the pipes need to be very thin in order to avoid the formation of drops. So called overhead compartments are in this context especially critical.
A method to moisten a layer of material, presented in pamphlet DE 29 25 026 A1, shows how water is added to the steam as it exits the nozzles.
According to pamphlet WO 2004/063463 A1 the layer of material is treated by a steam blower chest with additional water. In this instance, there is again the risk of developing droplets.
What is needed in the art is to provide an improved method and an improved device of the initially described type, while avoiding any of the previously mentioned negative side effects. This method is intended to apply moisture in a controlled fashion over different discrete zones onto a moving web of material, in particular a web of paper or cardboard, before and/or at a calender to influence the dampness, the shine and/or the smoothness, either transversely to or along the direction of movement of the machine (which can also be referred to as the direction of movement of the web or the machine direction).