Liquid packaging boards

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Liquid Packaging Boards (LPB) are significantly different from the other paperboard packaging materials due to their specific composition and properties that must be considered in all the phases of the recycling process.

There are two basic LPB groups:
  • Approx. 80 % of their total production are represented by 6-layer aseptic shelf-stable cartons to be stored and merchandised at normal temperatures, composed of approx. 75 % paperboard, around 20 % polyethylene (LDPE) and some 5 % aluminium;
  • Approx. 20 % are 3- or 4-layer refrigerated cartons made of approx. 80 % paperboards and 20 % LDPE.
Total LPB basis weights are usually 200 - 350 gsm. The top layer is almost always offset-printed, which requires the use of coated cartonboards. The recycling process is further complicated by the fact that there are used boards based on virgin, bleached as well as unbleached raw materials. Usual sources of the recycled raws are LPB manufacturers' wastes and municipal collection. As the municipal sources are usually more abundant, designing the recycling processes one should presume that:
  • the fibre portion of the input raw material always contains a very heterogenous mixture of fibres;
  • the input raw material always contains up to 5% aluminium.
Interested parties requesting the LPB recycling equipment often overestimate the respective market recycling opportunities. In the Czech Republic, a typical European country with a high waste recycling rate, the LBP per capita consumption in the year of 2010 was 1.7 kg. Thus, at recycling rates around 20 %, the available source in the 10 million population is not more than approx. 10 tons input material per day.

PAPCEL, thanks to the long-term experience in manufacturing equipment for converting recycled paper fibres into the forms usable for papermaking, developed specialised LPB-processing lines for two basic capacities of 20 - 25 tons and approx. 50 tons input material per day. The capacities are linked to the amounts of input material, the output quantities are significantly variable depending on input material composition and content of non-paper impurities, and they represent usually 60 - 70 % of input.

Compared to the other stock preparation lines preparing recycled papermaking stock, the basic difference when designing and economically assessing the SPLs processing LPB consists in considering non-paper input mixture portions to be largely saleable raw material and not only useless reject. Therefore the parties interested in the LPB recycling SPLs, before submitting inquiries, should have very clear:
  • Whether their plant is to be directly followed by a converting capacity or whether and how far from their plant they are going to despatch their products;
  • Whether and how high is the demand for the non-paper part of their production, i. e. mixtures of PE-foils with aluminium.
From the above considerations follow the main differences of the LPB processing lines compared to the common SPLs. Very briefly:
  • Unlike low consistencies (up to 5 %) in pulpers for common input raw materials, LPB is pulped at 12 - 15 % in the MCV type machines;
  • The higher capacity lines use two pulpers, the smaller one used for batch flushing PE-foils;
  • A great attention is paid to processing rejects in all the screening stages, to their thorough multiple flushing and to separating saleable material from useless reject;
  • Also LPB lines water processing is more complicated as it works with three grades of circulating water purity;
  • If the line is not followed by a plant processing its products the output material must be in addition dewatered to dryness values enabling reasonable shipping (at least 50 %);
  • The lines must be designed single-purpose, the trials to design lines alternately processing LPB and other recycled papermaking raws by now have not been successful.
The LPB recycling issue is naturally much more complicated, this brief text presents only the most fundamental summary. For more details the PAPCEL specialists are at your disposal.

Processing liquid beverage packagings - advanced technology

Beverage packagings most often caled simply “Tetrapak” are on one hand waste and a serious environmental trouble, on the other hand raw material and a highly valued utilisable economic source. Liquid packaging boards are composed of 60 - 70 % cellulose fibres and 30 - 40 % polythene (PE) and aluminium (Al - not always) foils. All the components are vauable sources of industrial utilisation under the sole condition: They must be separated as perfectly as possible. The main issue is separating cellulose fibres from foils. More papermaking methods solving this issue more or less sucessfully are well-known. Usually cellulose fibres of a quality sufficient for further papermaking processing are successfully gained but the foil fraction is usually too much polluted with cellulose fibres to be efficiently utilisable as a recyclable secondary raw material. That is still emphasised by the fact that by now tetrapak waste has been processed in heavy-duty plants and the lack of tetrapak needed for plant employment has been eliminated by adding common recycled paper bringing into the systems more sorts of impurities and thus utterly spoiling the foil fractions.

Bílý Tetrapak - obaly od mléčných výrobků Hrubé třídění s dopravníkem fólií Pohled do výrobní haly, v pozadí rozvlákňovač Paletizace bílé buničiny

The Ukrainian corporation “ASS” cooperating with PAPCEL solved in pursuance of its "Environmental development program" an absolutely unique task: To build in the OOO “KRONEX Ukrajina” Zmiyev paper mill an almost wasteless process of beverage packagings. The output from the plant had to be a fraction of pure cellulose fibres for papermaking and a fraction of pure recyclable foils polluted with up to 1 % residual cellulose fibres. The waste was composed of admixed heavy impurities of a negligible quantity and a small quantity of water drained to a biological effluent treatment plant. The task was also based on the real Ukrainian beverage packaging occurence and it was designed for the plant capacity of 15 - 20 tpd. The designed process based on a long-term experience of both partners with recycled paper processing was first tested at the PAPCEL development pilot plant and then implemented at the Zmiyev mill. The plant is based on the PAPCEL standard machinery specially tailored for this purpose. The auxiliary machines have been procured by the customer. A press made by the Slovakian Vanex company is used for dewatering fibres.

Raw materal is pulped in a batch working pulper LCV-14 at high consistencies. After pumping the fibres away the foil residues are washed in the pulper and discharged to a rotating drum (OBN-10) to be finally washed and dewatered. The pulped fibre fraction goes on through the heavy trash separator - cleaner (SVS-20) to the light impurities separator (VSV-30). The latter one is an intermittently working separator first sorting fibres through a 1.8 mm bored screen, then deflaking unpulped paper pieces and cleaning remaining fibres possibly stuck to the foils, then washing this material once again and finally discharging the remaining foils and water to a vibrating thickener..

The dewatered foils together with the foils from the drum proceed to a container and then to a packing press. The sorted fibrous fraction flows to a Vanex press (VX-20-VT) connected to a palletising device. All the water is recirculated in several loops and depending on a pollution rate it is used for pulping and washing. The plant works in an automated mode (except manual handling raw material and products). Operators control only the pulping node and supervise the function of the rest of the plant. Currently the plant works at an average capacity of 15 tpd and meets the quality requirements as per the project task.