A new generation of high performance leather protectors

3M Company have been selling Scotchgard protective treatments to the global leather industry for more than 40 years but, in the late 1990s, 3M discovered that a breakdown product of the original chemistry was found to be widespread in the environment. Due to their principles of responsible environmental management, they decided to phase-out this chemistry. A significant R&D effort to create a new generation of replacement protective treatments for leather produced from sustainable technologies, resulted in a number of new proprietary leather treatments in late 2002. For application during the wet stages of the leather production a new product, PM-4700 was developed. For application during the finishing stages of the leather production two new products were introduced, a water based material, PM-4701, and a solvent based material, PM-4800. When properly applied, these new materials provide high levels of oil, water and stain repellency to vulnerable leathers. The performance and application properties of the new products are equivalent to 3M Company's discontinued leather protectors and, in general, they also outperform the existing competitive leather protectors. In addition to providing state of the art performance, these newly developed materials have a very favourable environmental, health and safety profile that meets 3M Company's Life Cycle Management and environmental, health and safety principles. Through extensive testing, these materials have been shown to exhibit very low mammalian toxicity, low ecotoxicity, and the breakdown product of the small amount of residuals has a very low potential to bioaccumulate. 3M pioneered the technology of treating substrates with fluorochemical materials 'to keep things looking good longer'. One consideration in choosing a sustainable technology for the new leather protectors was the Bioconcentration Factor (BCF) of any degradation products. The ultimate degradation product, for the new sustainable technology, perfluorobutane sulfonate (PFBS) with four perfluorinated carbon atoms, has a dramatically lower BCF than the ultimate degradation product of the phased-out products, perfluorooctance sulfonate (PFOS) which has eight perfluorinated carbon atoms. The low bioaccumulation potential was a critical factor in 3M's decision to develop new replacement leather products based on PFBS technology. Sustainable technology development Bioconcentration: 3M company wanted to introduce new products based on sustainable technologies. One important attribute needed in these products was to have a low potential to bioaccumulate. This was determined using the fish BCF test on the ultimate breakdown compound of the fluorochemical residuals (see Table 1). As shown in Table 1, PFBS, with four perfluorinated carbon atoms, has a dramatically lower bioconcentration factor (BCF) than PFOS, which has eight perfluorinated carbon atoms. Table 2 lists the BCF values and the degree of concern raised by different governmental regulatory programmes. From Table 1 and 2 it is clear that PFBS, which has a BCF of less than one, is 100 to 1,000 times lower than levels that are a concern to the US EPA, Canadian Programs and the Joint US/Canadian Great Lakes Water Quality Initiative and meets 3M's objectives for a sustainable technology. Technical Challenge of Delivering Performance with Sustainable Technology: A key characteristic that affects the performance attributes of a substrate is its surface tension. It is widely known that substrates treated with fluorinated polymers, containing a terminal CF₃ group in the fluoroalkyl side chain, reduce the critical surface tension (y_c) and, therefore, the substrates repel higher surface tension liquids like oil and water. It is also well known that the degree of crystalinity of the fluorinated side chains in a fluorinated polymer (ie organization of the fluorinated groups) greatly influences the potential of a polymer to lower the critical surface tension (y_c) of a substrate as shown by Pittman and et al². The Differential Scanning Calorimetry (DSC) scans of the three acrylate homopolymers with varying chain lengths are shown in Chart 1. The polymers containing side chains of -C₈F₁₇ and -C₆F₁₃ groups show crystalline transitions in the DSC. The homopolymer, with -C₄F₉ side chains, does not show a crystalline transition, indicating a great deal of difficulty for the polymers with -C₄F₉ side chains to organize. Graph 1 shows the performance, as measured by water Receding Contact Angle, RCA, of the homopolymers with varying chain lengths. The RCA of the polymer with -C₄F₉ side chains is much lower than conventional polymers made with -C₈F₁₇ side chains. This relationship between the length (n) of the perfluoroalkyl side chains on the dynamic water contact angle and hence water repellency is mainly attributed to the organization of the fluorinated side chain with n = 6 and higher. The relationship between the length of the perfluoroalkyl chain in polyperfluoroalkylethyl acrylate polymers (made from C_nF_2n+1C₂H₄OOCCH=CH₂) and water repellency was also studied by Maekawa et al³. Their results showed that polymers with -CF₂- chain lengths greater than eight exhibited higher receding water contact angles and hence excellent water repellent properties. They partly attributed this to the increase in side chain crystalinity in the polymers with chain lengths greater than eight. The data below (Graph 1) shows it would be technically very difficult to develop high performance leather protectors based on the -C₄F₉ moiety. After a significant R&D effort, 3M has been able to develop a new generation of leather protectors based on proprietary technology using the -C₄F₉ moiety. As performance results will show, these new state of the art leather products have demonstrated performance equal to or better than competitive products. In addition to the better performance, the data shows the new product chemistry has a very favourable environmental, health, safety profile as indicted by standard health and environmental test results. The general findings are summarised as follows: The 'general-performances', as measured by oil and water repellency and abrasion repellency of leathers treated with the newly developed leather protectors PM-4700, PM-4701 and PM-4800, are significantly higher than the competitive products. The competition materials cannot match the high oil and water repellency achieved with the newly developed leather protectors. The performance 'durability', as measured by an abrasion test of the treated leathers, show the newly developed leather protector are significantly better than the competitive materials. The handle of leather treated with PM-4700 was generally better than the other materials, ie it was more neutral and certainly less harsh than some competitive products. It was also concluded that the penetration' of the leather treated with PM-4700 was better than the competitive materials, as demonstrated by the higher after treatment and oil and water repellency results achieved. Environmental principles 3M have recognised the necessity for responsible environmental management and conservation of resources for many years. As a result, 3M have established a record of many significant environmental improvements with products and at their facilities worldwide. 3M environmental policy will continue to recognize and exercise their responsibility to: * Solve their own environmental pollution and conservation problems * Prevent pollution at the source wherever and whenever possible * Develop products that will have a minimum effect on the environment * Conserve natural resources through the use of reclamation and other appropriate methods. * Assure that their facilities and products meet and sustain the regulations of all federal, state, and local environmental agencies. * Assist, wherever possible, governmental agencies and other official organizations engaged in environmental activities. 3M view long-term sustainability as a key to developing viable products and applications because the environmental landscape and regulations continue to change. Therefore, 3M are committed to developing products that not only meet existing regulations but also anticipate future environmental trends and the needs of the industry and consumers. 3M believe PFBS-based leather treatment products, with only four perfluorinated carbon atoms, are a sustainable alternative to other leather treatment products. Extensive testing has shown: 1) PFBS based polymers are stable with minimal to no environmental impact and are practically non-toxic 2) Products have low levels of residuals that are expected to degrade to PFBS that has: * Low mammalian toxicity * Low ecotoxicity * Low bioaccumulation potential Regulatory summary The new 3M leather products can be imported and used in all countries except Australia, Canada, Japan and the Philippines where chemical notifications to the appropriate regulatory agency will be needed prior to import. The new PFBS acrylate polymer has been notified in the United States and is on the TSCA Inventory. The polymer is exempt from reporting in Europe because it meets the polymer exemption criteria and, in addition, all monomers are on the European chemical inventory (EINECS). The polymer has also been nominated to the Korea chemical inventory, KECI, and the Chinese inventory. The PFBS-based fluorochemical acrylate polymer, and the 3M product formulations containing this polymer, have been the subject of significant testing. Summary 3M have developed a new generation of state of the art leather protectors based on sustainable technology from PFBS, for applications during the wet-end and finishing stages of the leather production. A comparison of the product performances of PM-4700, offered by 3M/TFL, with competitive products on several leather-types (upholstery, shoe and garment) was made. The performance and application properties of the new products are equivalent to 3M Company's discontinued leather treatments and, in general, they also outperform the existing competitive leather protectors. This technology has a favourable environmental, health and safety profile. The products, and potential degradation products, have been shown to have very low mammalian toxicity, very low ecotoxicity, and very low potential to bioaccumulate. These new leather treatment products provide a sustainable alternative to other leather treatment products currently on the market. Acknowledgement The authors would like to thank the entire staff of the TFL Basel and TFL Montebello laboratory and offices, for all their help and support in generating the comparative product performance data.