Devel­op­ing recyc­lable paper com­pos­ite pack­aging by coat­ing paper with nano­cel­lu­lose in a roll-to-roll process

Sub­sti­tut­ing con­ven­tion­al plastic pack­aging with altern­at­ives made from paper or card­board is one of the mega­trends cur­rently dom­in­at­ing the pack­aging industry, driv­en both by con­sumers and by policymakers.

How­ever, paper and card­board pack­aging still has a num­ber of dis­ad­vant­ages com­pared to plastic. For example, when used on its own, mono-mater­i­al paper is gen­er­ally not suit­able for pro­tect­ing products against extern­al influ­ences as its por­ous struc­ture means that it provides vir­tu­ally no bar­ri­er prop­er­ties against gases or con­tam­in­ants. Del­ic­ate products there­fore require pack­aging made from paper com­pos­ites which con­tain addi­tion­al bar­ri­er lay­ers – often made from fossil-based poly­mers – in order to guar­an­tee dur­ab­il­ity. Sep­ar­at­ing these paper com­pos­ites in order to recycle the paper is pos­sible in prin­ciple, but gen­er­ally res­ults in reduced recov­ery of fibrous mater­i­als and, hence, a recyc­ling rate sig­ni­fic­antly below the 90% required for paper and card­board. This in turn means that the license fees stip­u­lated for paper com­pos­ites in the Ger­man Pack­aging Act (Ver­packG) are just as high as for plastic pack­aging, and that single-use products made from paper com­pos­ites come under the rules of the SUPD.

More sus­tain­able bar­ri­er lay­ers with nanocellulose

The Coat­Nano­Cell pro­ject is attempt­ing to solve this prob­lem by devel­op­ing a bar­ri­er coat­ing for paper com­pos­ites that is based on nano­cel­lu­lose. The coat­ing can be applied to paper using a stand­ard indus­tri­al roll-to-roll coat­ing process.

Nano­cel­lu­lose – par­tic­u­late or fibrous struc­tures with at least one dimen­sion in the nano­met­er range – is obtained from cel­lu­lose and is there­fore made from 100% renew­able raw mater­i­als. It is already used in numer­ous fields includ­ing com­pos­ites, cos­met­ics, food and med­ic­al engineering.

Fur­ther­more, the use of nano­cel­lu­lose in coat­ings or as an addit­ive in films and paper is cur­rently the sub­ject of intense invest­ig­a­tion. Numer­ous stud­ies doc­u­ment the excel­lent bar­ri­er prop­er­ties that nano­cel­lu­lose exhib­its against gases and min­er­al oils in pack­aging applic­a­tions. Fur­ther­more, paper coated with nano­cel­lu­lose still counts as a mono-mater­i­al which can be recycled with oth­er waste paper. By the same token, paper com­pos­ites with nano­cel­lu­lose coat­ings do not come under the scope of the SUPD and can there­fore serve as a sus­tain­able altern­at­ive to the fossil-based plastic coat­ings used previously.

Cre­at­ing recyc­lable paper com­pos­ite pack­aging by coat­ing paper with nano­cel­lu­lose in a roll-to-roll process

The aim of the pro­ject is to pro­duce 100% recyc­lable paper com­pos­ite pack­aging in the interests of cre­at­ing a cir­cu­lar eco­nomy. Fraunhofer IVV is there­fore devel­op­ing pack­aging con­cepts for paper com­pos­ites with nano­cel­lu­lose coat­ings which can be recycled as mono-mater­i­al paper. The pro­ject involves sys­tem­at­ic­ally examin­ing com­mer­cially avail­able nano­cel­lu­loses in coat­ing for­mu­la­tions on dif­fer­ent paper sub­strates in order to find suit­able combinations.

The key step is the work to devel­op a roll-to-roll pro­cess for apply­ing the nano­cel­lu­lose coat­ing to paper – the main chal­lenges here include scal­ing up the coat­ing pro­cesses with vis­cous nano­cel­lu­lose sus­pen­sions and dry­ing the nano­cel­lu­lose films once they have been applied. The nano­cel­lu­lose coat­ing should provide the paper pack­aging with suf­fi­cient bar­ri­er prop­er­ties against oxy­gen while also provid­ing good pro­tec­tion against min­er­al oils and grease in order to increase the pre­vi­ously lim­ited use of recycled paper in food pack­aging. Ana­lyt­ic­al invest­ig­a­tions and a sub­sequent assess­ment of the MOSH/MOAH bar­ri­er lay­ers gen­er­ated are there­fore to be car­ried out in order to eval­u­ate the poten­tial use of recycled paper coated with nano­cel­lu­lose in the food sector.

The exper­i­ment­al work will be sup­por­ted by the Tech­nic­al Uni­ver­sity of Munich. In order to obtain a more in-depth under­stand­ing of the occur­rence of defects dur­ing the tech­nic­al man­u­fac­tur­ing pro­cess, sim­u­la­tions will be car­ried out at the TUM School of Life Sci­ences to mod­el the coat­ing and dry­ing processes.