The Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB is researching harmless biobased alternatives to harmful chemicals often used in textile processing. The Institute is working on utilising side streams from the animal feed manufacture for the production of chitosan. The biopolymer is supposed to be used as a sizing agent in the processing of yarns or for the functionalisation of textiles. Fraunhofer IGB presented its work at the Achema trade fair in Frankfurt, this month.

Chitin is a major component of insect skins and shells; large quantities of it result from the production of animal feed – ever since the feed industry has increasingly relied on insects as protein suppliers. Insects have the advantage that they reproduce quickly and can be bred cheaply on low-value substrates.

This makes them a sustainable source of protein. So far, soya has been used for this purpose, but its cultivation is in direct competition with food production. Insect proteins have already been approved for poultry and pig feed. Since summer 2017, they can also be used as feeding stuff for fish. It is therefore to be expected that the use of insect proteins will become even more important in the future, the Institute explains.

Valuable recyclable material

The feed industry is focused on proteins, but the skins and shells of insects remain as a waste product. If they can also be utilised, this contributes to the sustainability and economic efficiency of the overall feed production. The potential is enormous, the Institute explains: in the course of their development, the larvae of the insects shed their skins several times. The remaining molting products consist up to 40% of chitin.

In the joint project ChitoTex, the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB is investigating how insect chitin from animal feed production can be processed to supply biobased chemicals for textile processing. “For a long time now, we have been working on the development of processes for the recycling of residual and waste materials and therefore have the necessary expertise,” explained Dr Susanne Zibek, who heads the research area of industrial biotechnology at the Institute.

Substitute for harmful fluorocarbons

At first, the Fraunhofer researchers have developed a purification process to separate chitin from further components of the insect skins such as proteins and minerals. “We are investigating various ways of deacetylating chitin to produce chitosan,” said Zibek. “With an enzyme screening for example, we search for suitable enzymes for the deacetylation process.”

Due to its ability to form films, chitosan can be used as a sizing agent. This reduces friction in weaving machines and prevents the roughening or breaking of yarns in the weaving process; after that the sizing agent is either washed out again or remains on the yarn.

The second possible application is the functionalisation of textiles, i.e. the finishing of textile fabrics with specific properties. “For example, we want to use the functional amino group to link hydrophobic molecules with the chitosan. Water-repellent properties can be achieved when applied to textiles,” added Zibek. “Until now, environmentally harmful fluorocarbons are widely used for the hydrophobic finishing of outdoor textiles.”

www.igb.fraunhofer.de