Paper recycling takes place inside paper mills when they receive paper to be recycled. Here it is chopped, bleached and reduced to a pulp by adding hot water. This allows the removal of the last impurities and waste from the mixture. The remaining fibres dissolved in the water are then filtered several more times before it becomes suitable for paper production.
The filtration phase involves the separation of liquids from solids by pressing, which takes place inside a screw press. The screw press is a slow-moving mechanical device in which a conical screw rotates inside a perforated cylindrical filter. The solution of fibres dissolved in water is placed inside the press. During the pressing phase, the paper fibre is pressed with increasing force against the metal filter and the holes in the filter allow the water to drain out, therefore retaining the paper pulp.
Paper recycling can transform approximately 95% of the collected material (fibre from waste paper) into new paper.
The Costacurta drilled plate that forms the filter of the screw press is a fundamental element of the machine. The plate must have a high thickness to resist pressure, and different kinds of perforations (cylindrical, conical or step drilled) that enable the filtration of water and its separation from the solid pulp.
In the production of a drilled plate for paper recycling, the quality of the material used and the precision of the perforations are crucial elements for guaranteeing efficient filtration.