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Advanced cellulose packaging

Final Report Summary - ADCELLPACK (Advanced cellulose packaging)

Executive Summary:
Over 50% European goods are packaged in plastics according to Plastics Europe. Plastic packaging, currently derived from petroleum sources, are the largest application sector for the plastics industry, and represent 39.4% of the total plastics demand. Converter demand reached 45.9 million tonnes in 2012, and 25.2 million tonnes of plastics ended up in the waste stream in 2012, where packaging dominates the waste generated from plastics, covering 62.2% of the total. Post-consumer plastic packaging waste can be divided on those coming from households (63%), and the remaining comes from the trade/ industry segment (37%). From this amount, EU 27+2 recycled 5.4m tonnes, 34.7%,while energy recovery reached 34.5%, and the rest of the balance going to landfills and incineration without energy recovery.

A single polymer is often unable to provide food packaging requirements; thus there is a need to use specific structures based on multilayer plastic materials. In such structures, polymers with different properties are combined, where at least one layer acts as barrier, and other polymers provide the mechanical/sealing properties, including other compounds like e.g. adhesives, inks or stabilizers. Different studies corroborates that recycling these materials is almost impracticable and frequently uneconomical.

MAP products represent the majority of food products consumption and are usually based on multilayer plastic materials. Only a 5% substitution of MAP packaging materials would reduce over 300.000 tons of non-renewable plastic packaging wastes disposal. This together with the use of bio-based materials is a promising alternative in the packaging industry for reducing the use of non biodegradable polymers and for increasing the use of renewable polymer materials.

ADCELLPACK consortium identified that materials based in cellulose combined with biodegradable polyesters can be an alternative to substitute materials currently used in MAP. Changing consumer habits and motivations have benefited cheese consumption, and sliced cheese is an increasing market (>300kton/year), producing a huge quantity of packaging wastes. That is the reason for the selection of cheese as the fresh food product of ADCELLPACK.

Objective
ADCELLPACK objective was to provide a thermoformable tray composed of cellulose together with a multilayer structure incorporating polylactic acid (PLA) among other compounds , to provide required properties. This development could be suitable for packing fresh products in MAP conditions. A whole sustainable solution that maintain product quality and assure its food contact safety has been developed by ADCELLPACK consortium, reaching a shelf life higher than initial target of 4 weeks.

Project Context and Objectives:
The technical work performed during second period of ADCELLPACK project has been focused in the optimization of developments started during first period in order to provide a biodegradable paper based tray and its lid.
Once materials characterization was performed, multilayer structures were selected and up scaled for developing a final tray and a lid film. Sliced cheese supplied by Juan Luna were packed on the developed biodegradable package (2 shelf life trials), and an exhaustive evaluation of cheese quality and shelf-life was performed. Biodegradability tests of developed package have been also carried out during this period. Main results achieves in each WP are summarized:
WP1-”Formulation and evaluation of paper properties” Main result of this WP is the development of a paper formulation with improved elongation. To obtain this results different variables were verified with strain at break measurements and laboratory scale thermoforming experiments. The utilization of additives and refining were recognized to be the main possible routes. Different compounds such as hydroxypropyl cellulose (HPC), carboxymethyl cellulose (CMC), polylactic acid (PLA), polyvinyl alcohol (PVA), sorbitol and starch have been evaluated. All this combinations led to formulations scaled up by Papelera de Brandia

WP2- Formulation and evaluation of biodegradable polymer blends
Polymer blends represents one of the most attractive methods to develop new polymeric materials. There are many factors that affect the correct processing of materials by extrusion, such as characteristics of material to be extruded (composition, molecular structure, interactions between components) and processing parameters (temperature, screw speed, geometry of the screws and residence time). Polylactic acid (PLA), was used as matrix, and Polyglycolic acid (PGA) was selected based on its high barrier properties. Different processing parameters, compounds (compatibilizers, catalysts, and other organic compounds), have been evaluated to provide blends with enhanced properties.

WP3- Development of coated paper
The objective of WP3 was to develop coated papers complying with the required properties to substitute tray materials based on non-renewable resources. The base paper research was made in WP1 and the PLA blend development in WP2. The pulps and mill-scale papers were obtained at industrial scale. Coated papers were obtained by extrusion coating, temperature of extruder zones, nozzle parts and a chill roll was adjusted. Tensile and adhesion properties as well as coverage of produced PLA coated structures were evaluated, and finally, thermoformability of coated papers was studied. The results of extrusion coated papers were compared with those obtained for uncoated papers.
WP4- Processing and evaluation of lids
Lid film was processed by coextrusion. This technique combines two or more molten polymer layers into a composite extruded web which provides enhanced properties when compared to monolayer materials. Work Package 4 processed and evaluated the polymer blends selected in previous workpackage (WP2), with suitable applicability for the development of lid films. Results for mechanical and barrier properties provided the data for optimized structures.

WP5- Evaluation of final packaging
In workpackage 5, packaging trials were performed to evaluate developed multilayer structures and ensure appropriate and required properties on its final applications. This evaluation has been considered on different steps to provide overall comparison with commercial packaging structures (non biodegradable), and cover organoleptic, microbiological and physicochemical analysis of packaged cheeses. Results confirmed the suitability of developed structure for packaging of sliced cheese. Packaging evaluation have included as well evaluation of materials according European standard, EN13432-2000.
WP6- Exploitation and dissemination
The objective of this WP was to describe and to accomplish dissemination activities and to manage the potential exploitable foreground generated within the project. This was accomplished through the diffusion of project activities, and the evaluation of potentially protectable results arising from the project.

Project Results:
The main objective of Adcellpack was to provide a novel biodegradable sliced cheese packaging based on cellulose substrate. Intermediate objectives of Adcellpack project included:
• Development and characterization of a paper substrate with improved elongability as a physical substrate for packaging.
• Development of biodegradable polymer blends with improved properties, based in PLA/PGA blends
• Development of PLA formulations for mechanical properties improvement.
• Gathering together all major developments in both blends and paper substrate development to provide an optimized final structure.
• Validation of the new solution through a shelf life trial, trying to resemble commercial scenarios.
With regards to the aforementioned S&T objectives of the project, in line with the target objectives exposed in the description of work, main results are indicated in the following paragraphs:
• Development and characterization of a paper substrate with improved elongability as a physical substrate for packaging.
This objective has been achieved through the application of different approaches. It has been considered as multiple development, in which the final product is affected also by the paper making process parameters and the final structure of the product. Work developed within the project has involved a three step approach, first it was to find the best tools for improving the elongation properties of the fibre web with the means of optimal pulp grade selection and treatments. The second part aimed at gathering information about the influence of paper making process parameters and the final structure of the product on improving the elongation of fibre web. The effect of different variables was verified with strain at break measurements and laboratory scale thermoforming experiments. On a third stage, main efforts were devoted to its implementation at industrial scale and different formulations were processed by this procedure.

• Development of specific PLA/PGA blends and formulations with improved mechanical properties.
Formulations of polymeric matrixes have involved different routes related to:
1. Initial polymer grades; selection of polymer grades (PLA), was based on the effect of MW and isomer content on processing and properties. As example, MW contributes to a raised melt strength and processability ; d-lactic monomer content contributes to the flexibility of the products and reduces the brittleness.
2. Incorporation of low% of other compounds (processing aids or other additives), can contribute to an improved processability and has an impact on mechanical properties. Based on the processing routes, its effect was evaluated.
3. Control of humidity content: During melt processing partial hydrolysis of polyesters (PLA and PGA), occur as function of humidity content, residence time and process temperature. Predrying of polymers is a must to avoid detrimental effects during the processing.
4. Application of different concepts to provide enhanced blends through reactive extrusion. This has involved a) the use of peroxides/maleic anhydride to obtaina a modified PLA chain with maleic anhydride grafting, and b) a transesterification through the use of two catalysts to provide a randomly distributed PLA-PGA copolymer. In this step it has been necessary to develop specific processing routes to ensure distribution, content and homogeneous processing of the polymeric blends. Included in these processing routes, compounding parameters such as screw, barrel configuration, dosing systems, temperature profile and other many parameters have been adjusted.

• Validation of developed packaging.
An optimized structure was validated against conventional (commercial) packaging structures applied to sliced cheese packaging. Shelf life studies demonstrated that developed materials provide required properties. Both headspace analysis, microbiological tests and biodegradability testing were evaluated and showed promising results for the developed materials.

Potential Impact:
Different results were identified during the writing of project proposal and have been confirmed during the project. Main results were the development of a paper with improved elongability, and the development of polymer blends with improved barrier properties compared to neat matrix (PLA). Both results have been achieved during the project.
Other results achieved during the project have arisen from different approaches carried out to increase material properties. This have dealt mainly on a)the development of alternative application systems for low quantities of compounds in order to assure correct dosing,b) the development of blends in reduced processing steps through specific dosing and c)development of formulations for improved mechanical properties, and obtain multilayer structures.
SMEs have obtained a deeper knowledge on paper and renewable material processing and properties. The activities carried out within the project provided an overall approach to packaging development valuable for all companies. Besides foreground knowledge achieved, companies have evaluated patentability of the results and will proceed according to this patentability evaluation.