On our 3 paper machines, we are able to annually produce up to 64 000 tones of kraft paper, including semi and fully extensible sack kraft, wrapping kraft and some specialty grades.
PM 1 (3660 mm) Products:
- Flat sack kraft paper from 65 gsm – 150 gsm
PM 2 (3060 mm) Products:
- Semi extensible sack kraft from 70 gsm – 120 gsm
- Fully extensible sack kraft from 70 gsm – 120 gsm
- SpeedEx from 70 gsm – 120 gsm
PM 3 (2280 mm) Products:
- Flat sack kraft from 40 gsm – 90 gsm
We can also offer all above-mentioned products with up to 33% of wet strength.
Swiss manufactured off-line Slitter-Rewinder converts coils and rolls from 40 mm – 1200 mm (for bag handles, paper rope, counter rolls, bottom patches, valve tubes etc.).
Grammages are from 50 gsm – 150 gsm, both for flat and extensible sack papers.
We also have a modest sack plant, producing open mouth sacks for agri-products, with maximum 2 color prints.
TECHNOLOGY OF EKP PRODUCTION
Mechanical process
The extensibility is imparted into a paper, produced on an ordinary paper machine equipped with an extensible unit, by a mechanical process. The paper is mechanically compacted by a compaction process through an elastic medium mainly a rubber blanket which is forced to expand and while in this condition comes in contact with the paper web which is at suitable level of moisture content.
The sudden release of the expanding forces allows the rubber surface to return to its original length and in the process, forces the paper fibres to assume new configurations. The paper web is held in contact with the rubber surface by pressure of a smooth surface having a considerably lower coefficient of friction than the rubber. This is required because the paper web must recoil with the rubber and slide over the smooth surface without creeping.
The resulting paper has the same surface appearance as paper not processed in this manner but has a controlled built in stretch, which has a considerable resistance to removal.
A significant feature of the compaction process is that it is entirely mechanical. No chemical changes are made to the paper.
Property
The paper along with its inherent tensile strength and newly imparted stretch gives rise to a property called tea – the tensile absorption property, which is the most significant property for its improved performance over kraft and sack kraft paper.
Tea – it is measured by stretching a paper sample to the breaking point and plotting a curve of the applied tensile force against the samples elongation. The paper’s ability to absorb energy, i.e. to perform work under stress, i.e. its TEA, is proportional to the area under the curve.
Performance
When a sack is dropped, from a place of rest, its potential energy gets converted into kinetic energy under gravity, as it approaches the surface and upon touching the ground, a shock wave is propagated through the contents, reaches the sack wall and is reflected back to the contents again. In reflecting the shock wave, paper of the sack changes. It is slightly stretched and contracts again when the stress is released, absorbing the part of the impact energy in the process. The contraction is not complete however, and some elongation remains. The reserved potential TEA, enables the sack to absorb more shocks, i.e. to stand another drop and thus extensible sack kraft paper improves performance over conventional kraft paper which has only tensile strength to prevent or withstand the impact energy.
The greater the TEA of the sack, the greater its ability to withstand additional drops. The research has shown that of all properties in a sack, the measure of TEA is the most important as there is a straight-line correlation between the total TEA and number of drops to failure.
Win-Win Situation
In order to achieve certain performance level, the emphasis was given onto the tensile strength alone, before the advent of the concept of extensible paper and as a result thereof gsm or the number of plies in a sack or both, used to increase. This used to result in higher fibre consumption for the paper maker, and higher cost for the sack maker. With extensible sack kraft paper equivalent efficiency could be achieved by lower gsm or lower number of plies or both, for the benefit of paper maker, sack maker and for the end consumer. It is a win-win situation.
