Description of Production Process

 

The production is made through the departments mixture preparation, paper machines and rolls set-up.

Mixture preparation

It is the department where all raw materials, after appropriate processing are mixed to form an aqueous suspension that in the next step in paper machine is converted into finished paper.
The cellulose supplied in sheets will be reduced in aqueous suspension at 5% dry in two pulpers; such suspension then undergoes a refining in refiners and deflakers. The intensity of refining is dependent on the physical and mechanical properties required by the paper. The fine fibrous suspension is combined with other raw materials in the mixing cest.
The pigments and colorants are added in the mixing cest. Their regulation conditions the paint mixture. Resins, aqueous solutions of epichlorohydrin polyamide resin, give to the paper the wet strength.

Paper machines

The mixture mixed, diluted, dosed and cleaned is ready to be transformed into a sheet of paper.
The fibrous suspension, very dilute (more than 99% water), goes to a suitably shaped metal container called head box which has the function to distribute with the utmost regularity and uniformity the suspension on the forming wire , preventing the formation of vortices and foams.
The head box is the heart of the paper machine, where the paper born. It has essentially the difficult task of distributing a flow of pulp and water in a thin sheet with uniform characteristics over the entire width.
The forming wire, which is an endless belt that wraps two or more cylinders that rotated constantly, has the basic function to lose much of the water contained in the mixture favoring at the same time, the union of cellulose fibers. At the end of the cycle that the mixture needs to do on the wire, the paper begins to have a certain level to be removed from the base on which it is settled and then allow the start of a new phase of processing. When the sheet leaves the wire, still contains a high percentage of moisture. This value is very variable depending on the type of machine, mixture and weight. Once detached from the wire the sheet of paper is settled on a felt this is a porous synthetic tissue in the form of continuous ribbon whose job in the at first , is to advance the paper, settled on it, to the next press section .
The other fundamental task of the felt comes from the fact that at this point in the process the paper alone can not be compressed, because its major component is water and a possible attempt to compression would ensure that stray fibers in aqueous eqipment moves wildly destroying the structure of what already formed. If the pressure is exerted on the sheet when it lies on the felt soft and absorbent, water is transferred to the felt without pressing problem for the fiber.
The presses are made up of pairs of opposed cylinders, the number and size vary with the characteristics of paper to be manufactured. From this point on the sheet is dried by heat.
The paper comes in a set of cylinders called drying section, and the remainder of the paper machine is called the drying part. The various cylinders have the ability to vary the speed individually or in groups of several batteries.
The function of the drying section then is to dry the paper, that is to dehydrate almost completely (about 3% water final). The paper tape enters in the drying section at a temperature around 15-35 ° C and must be brought gradually to a value slightly above 120 ° C to enable the transformation of water retained in the fibrous support in steam and condensation of the resin for the wet resistance.
This vaporization of the water must occur in the time used by the paper tape to cover the space represented by the drying section..
All the drying section is covered with a hood of aluminium to prevent cold air currents, resulting in heat loss, and to obtain a good and uniform heat distribution over the whole cross-section of the paper.
The machine for the production of paper is called continuous because the paper is generated without interruption. When the sheet leaves the drying section is wrapped, in the reel (pope), over a core that serves as a support for the paper that wraps around. This creates a roll weighing several tons and a width equal to the width of the machine. For the trade effects and the subsequent stages of construction, the rolls must have a certain size and weight. Therefore it is necessary to periodically remove the formed roll and start winding of a new one.
This operation is performed without stopping the machine continues, preparing, close to the complete roll, a new core ready to be wrapped from the sheet. The operator of the machine, with a particular system, controls the breaking of the sheet that is transferred from the full roll on a new core to be filled.

Setting rolls

The semi-finished roll will be reduced in the size desired by the customer, width and diameter, with perfect trimming of the edge on the rewinder.
The rolls after packaging and weighing are kept in the warehouse of the finished product awaiting shipment.
In that department there is a second rewinder which is occasionally used to remove any defects of the rolls already set up.