C. Orgilés-Barceló’s research while affiliated with INESCOP Footwear Technological Institute and other places

Over 20 million tons of animal by-products (ABP) emerge annually in the EU from slaughterhouses, plants producing food for human consumption, dairies and as fallen stock from farms. These ABP usually contain high water content which promote the microorganism proliferation, their decomposition and environmental pollution. Due to the growing demand from the European Union for the treatment of the by-products of the meat industry, these low-value tissues are non-edible materials which are typically recovered by a rendering process whose main final products are animal fats and meals. Meals obtained from ABP considered of Category 3 (also called processed animal proteins, PAP) are suitable for pet feeding, but other applications are not easily found due to its insolubility, heterogeneity and the presence of non-protein substances. Currently, European Policies about environmental issues promote to minimise industrial wastes, their recycled and transformation into high-value added products which could be reused in other industrial fields. Since rendered meals are rich in collagen, they can be a source of gelatine and hydrolysed collagen which could be use in other applications. They include new biodegradable and bio-based adhesives, flocculants, emulsifiers, foaming agents, fertilisers, retanning agents, reductors and stabilizing agents for nanoparticle synthesis, among others. In this sense, INESCOP is working on the project PILOT ABP “Pilot plant for environmentally friendly animal by-products industries” for the isolation of collagen derivatives from PAP to evaluate their viability in other industrial sectors. This work deals about the influence of extraction conditions on biopolymers properties and therefore on its final application. This project has received funding from the European Union’s Seventh Programme for research, technological development and demonstration under grant agreement No 603986. Duration: 01/06/2014-31/05/2017

Nowadays, the requirements of consumers go further of their primary use, which is to protect the foot from the harsh climatic conditions and terrain. Aspects such as comfort, safety, health and welfare are increasingly demanded by consumers. The use of new smart materials breaks new opportunities to the footwear industry, enabling it to meet the expectations of increasingly demanding customers and thus become more competitive. The fight against microorganisms in footwear focuses on the synthesis of substances that, once added to the materials that are commonly used in footwear manufacture, will confer antimicrobial, antifungal and/or antiseptic properties on them, thus avoiding the proliferation of microorganisms that are responsible for infections and bad odour in feet. To date, and to this same end, the industry has resorted to the incorporation of organic biocides in the formulation of materials. However, but the use of these products is being limited since most of them are harmful to humans and the environment. In fact, the European Commission has decided the non-inclusion of some of them in the positive lists of biocides for use as preservatives in polymeric materials, rubber, leather and fibre, so they are completely inadequate for use in the footwear industry. In this sense, the formulations based on metals like silver and gold are more and more regarded as an efficient alternative to replace organic biocides. The antimicrobial properties of these metals, which were already well known long time ago, have been boosted thanks to the development of nanotechnology. Nanometric sized metal particles have proved to be highly active against a wide spectrum of bacteria and have a longer lasting effect, among other benefits. However, both the usual procedures for the preparation of metal nanoparticles and their handling present some drawbacks from the health and environment point of view. In addition, their marked tendency to aggregate compromises their stability and effectiveness and can sometimes cause poor dispersability in the materials to be modified. The main objective of this study is to synthesise metal nanoparticles by means of “greener” procedures that are an alternative to the current ones, thus boosting the use of natural raw materials. Alternative reducing agents, stabilisers and/or catalysts of natural origin, such as amino acids, sugars, plant extracts, gelatine, etc., will be employed as much as possible, hence contributing to the reduction of their environmental impacts. Authors thank the partial financial support to the Spanish Ministry of Economy and Competitiveness through the project NANOMETAL (Ref. CTQ2013-40927-P).

Since raw materials used in polyurethane adhesives come from fossil resources, there is a trend towards renewable alternatives to petroleum. In this sense, the use of carbon dioxide as a feedstock for the chemical industry is an interesting alternative to oil because CO2 is inexpensive and abundant in the atmosphere. A new generation of CO2-based polymers has been recently developed, specifically, polyols, essential components for polyurethane synthesis. This work focused on the synthesis of reactive polyurethane hot melt adhesives (HMPUR) containing polycarbonate polyols derived from CO2 and 4,4′-diphenylmethane diisocyanate (MDI). The sustainable polyurethane adhesives derived from carbon dioxide were characterised by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Finally, the adhesion properties were measured from a T-peel test on leather/polyurethane adhesive/SBR rubber joints, in order to establish the amount of CO2-based polycarbonate polyol that could be added to reactive polyurethane hot melt adhesives satisfactorily to meet the quality requirements of footwear joints. All percentages of CO2-based polyol added to polyurethane adhesives meet successfully the quality requirements of footwear, being comparable to conventional adhesives used currently in shoe joints both in terms of green and final strength, and after high temperature/humidity conditions and hydrolysis tests. Therefore, this new generation of sustainable polyurethane adhesives could replace the adhesives commonly used in shoe joints.

Previous studies al INESCOP demonstrated the feasibility of replacing polyols, one of the essential components of polyurethanes, as vegetable oils, a sustainable alternative to sustainable polyurethanes. However, they compete with food production for humans or animal feed. In this sense, the use of carbon dioxide as a feedstock for the chemical industry is an interesting alternative to oil because CO2 is useful, versatile, non-flammable and its presence is abundant in the atmosphere. Specifically, carbon dioxide could be used for the synthesis of polyurethanes, one of the most polymers produced worldwide, currently dependent on fossil fuels. This work focused on the synthesis of polyurethane adhesives containing polyols from CO2. They were synthesised with 4,4’-diphenylmethane diisocyanate (MDI) and 1,4-butanediol as a chain extender. The sustainable polyurethane adhesives derived from carbon dioxide were characterised by Fourier Transform Infrared Spectroscopy (FTIR) and thermogravimetric tests (TGA). Finally, the adhesion properties were measured from a T-peel test on leather/polyurethane adhesive/SBR rubber joints, in order to establish the amount of CO2-based polyol that could be added to polyurethane adhesives satisfactorily to meet the quality requirements of footwear joints.

Leather is widely used to make items such as clothing, shoes, car upholstery, boat and airplane seats, and many more items for daily use. Each item requires the use of a leather type with certain properties. Here the use of chemical compounds that are able to change the properties of these raw skins and hides comes into play. In general, traditional finishing treatments that provide leather with the desired functional features involve significant energy consumption as well as large volumes of water (both in finishing liquors and in further rinsing). In addition, in most cases, said treatments involve also the use of chemicals such as halogenated organic compounds, biocides, and organophosphorous compounds, the use of which is currently restricted or under consideration in the European Union (REACH and Biocides legislations). The main objective of this work is to demonstrate the technical and environmental feasibility of the MLSE technology that combines atmospheric-pressure plasma energy with laser energy for the treatment of leathers as a way of providing them with improved properties for their application in the manufacture of products with functional properties and high added value.