Our paper production process can be divided into four process steps:
In pulpers the raw materials are disintegrated. Afterwards the fibres are cleaned and milled in the raw material preparation.
Then on the paper machine the paper web is generated, dried and coiled up on tambours. Finally on the slitter machine the tambours are cut and packed up to customer reels.
Three types of raw material are used at Grünewald-Paper:
After release, the raw materials in quantities according to the recipe are defibered in a pulper.
We are equipped with three pulpers, each of these optimized for one raw material type of raw materials. Thus the defibring process operates on a very high level of effectiveness and energy efficiency.
Within the defibrizing process the plastic film is separated of the beverage cartons and is directly conveyed from the pulpers into our residual material treatment system. Here, we process the folms to merchantable plastic agglomerates, e.g. for injection moulding.
In the raw material preparation a cleaning process matched to the particular raw material is carried out on the three streams of raw material. Undefibered rests of raw material, heavy contamination (e.g. sand) and lightweight contamination (e.g. plastic coatings) are separated off and discharged.
All recycled raw materials are then heated up and defibered for several minutes at approx. 100 °C in the disperger system for hygienisation and cleaning. After that all the fibres are milled before they can interweave to a solid fibre web in the paper machine.
The fibre-water mixture generated in the raw material preparation is then diluted down to a fibre content of just approx. 0.5 %. At this stage it is passed to the paper machine with a speed of around 600 litres per second.
Since the most recent modernization of the paper machine, which was first put into operation in 1970, can run at a speed of up to 800 m/min (48 km/h).
The fibrous material is first dewatered in the paper machine through a wire. In the next step the paper web, that has been created there, is pressed by two rotating felts so that the water from the paper web is absorbed by the felts. This is followed by the drying and smoothing of the paper in the dryer section in which the paper web is led via a steam-heated Yankee cylinder. The yankee cylinder has a diameter of 5 metres. On the reverse side a temperature of 320 °C is passed through.
After a dwell time of 3 to 5 seconds on the 27 metres long paper machine 600 litres of fibre-water mixture have been turned into around 1.5 kgs of paper.
On the reel slitting machine the large paper reels, also known as tambours, are cut to smaller customers reels. Layer by layer the paper is unwinded to so - called changes of different diameters, observing the customers requirements on reel widths, reel and core diameter.
After each change the paper rolls are wrapped in the reel-slitting machine. Finally they are weighed, labelled and brought to the pre-planned places in our finished-goods warehouse.