The leather articles that are the most appreciated are often made of leathers which are the most sensitive to soiling and staining during casual and professional use. In the case of the footwear, apparel or furniture markets, it typically includes nubuck and suede which are also defined as vulnerable leathers.
Nowadays, industrial and consumers’ market reports state that stain protection is seen as an area of growth in the apparel and shoe sectors. Because of the convenience and easy-care concept it provides to consumers, surface protection, stain-protection and stain-release as well as anti-soiling are the fastest growing concepts in technical development and marketing.
A large range of protective performances
Due to the large surface area and fibrillar structure, vulnerable leathers readily absorb water and oil-based substances to which they can be frequently exposed. Thankfully, specialised fluorocarbons can be spray or drum applied in order to provide protection to vulnerable footwear.
Fluorocarbon treatments provide protection against the effects of wet weather, melting snow, food or drink stains without changing the natural feel and look of leathers. The protection imparted by fluorocarbons – whether by drum or spray application – largely treats the surface layers. Under heavy mechanical load, it is possible for both water and oils to penetrate this surface barrier.
Under these conditions of stress it is, therefore, possible to introduce stains. Nevertheless, if these leathers have been treated with fluorocarbons they are much easier to clean than untreated leathers. Application of fluorocarbons to washable leathers enables an ‘easy care’ concept for footwear and apparel.
Typical performances for surface protection of casual and industrial footwear
For casual footwear, there is a discernible increase in demand for improved comfort in terms of longer-lasting coolness and dryness for the wearer of the shoe. In this respect, leather has a natural advantage over synthetic footwear – as long as the leather is not prevented from breathing by having been finished or heavily waterproofed. This is because all finishes act as a surface barrier to the passage of water vapour and, likewise, heavy waterproofing reduces the water vapour permeability.
However, this demand for improved comfort cannot be separated from the consumer expectation that footwear should also have some surface protection. Thankfully, the protective materials from 3M (Scotchgard Protector for leather) impart surface protection without any discernible effect on water vapour permeability. They are, therefore, eminently suitable for inclusion in recipes for making this type of shoe upper.
Fluorocarbons also offer a high level of protection in industrial applications. This is especially important in areas where leather might otherwise be subject to breakdown of the structure, such as contamination by acids or alkalis.
Salt stain resistance
Walking in winter time on a snowy street can easily turn into a disaster when a couple of hours later, after drying, a white crust of salt appears, creating an irreversible loss of softness and an unpleasant aspect to the shoes, especially on dark shades. The fluorocarbon barrier protects the leather from salt water. Even if the salt can dry out on the leather surface, a very smooth brush will be enough to get rid of the stain.
Industrial risks for footwear and gloving
Industrial footwear and gloving also require a best-in-class surface protection. Handling strong acids and alkalis at work means a complete and safe protection for the workers. A fluorocarbon treatment with 3M Protective Materials builds an outstanding surface protection against the most concentrated acids and alkalis. Even hydrochloric acid does not alter the leather surface but, without any treatment, the leather would dramatically and instantly shrink. Also a boiling saturated solution of sodium hydroxide will only cause a slight burn of the leather surface instead of complete through penetration without a fluorocarbon treatment.
The peace of mind of the customer!
Wearing a suede or doubleface coat in the rain or sitting on a smooth comfortable nubuck sofa requires trust in the protection of your most valuable goods.
Increasing numbers of companies have understood the necessity of ‘easy maintenance’ and ‘easy care’ to promote their products at the consumer level. What is better than wonderful apparel, that is machine-washable with lasting protection against stains?
Nowadays ‘peace of mind’ concepts become more and more important and respected buying factors by the end user.
Application of 3M Protective Materials Protector for leather
1) When applied in the drum, the following recommendations are typical levels of application. These levels shall qualify for the brand Scotchgard Protector for Leather
* As a co-application: After the dyeing process, 3-6% PM 4700 (on shaved weight), 10 minutes prior or after the introduction of the fatliquors.
* As an after treatment in the drum: 3-6% PM 4700 (on shaved weight), in a fresh bath, 35-50°C; pH3.5-3.7; 40-60 minutes.
2) When used as a spray application to the grain or suede surface, the following are typical levels of application:
* Aqueous spray application
75-300g PM 4701
700-925g Water
Apply 5-15g/ft2 (co-solvents for wetting – ethylene glycol or methoxypropanol)
* Solvent spray application
25-50g PM 4800
950-975g solvent or solvent blend (ethers, ketones & esters)
Apply 5-15g/ft2
Keep your leathers looking good longer…
The surface protection of treated leathers kept under static conditions actually continues to improve for some months. The effect of wear can, however, have the opposite effect and this can be simulated by a simple abrasion test which is based on the use of sandpaper attached to the head of a crock meter.
There is little change in the performance of 3M Protective Materials products by this surface abrasion, whereas products available from other sources show a lowering of performance.
The performance monitoring for the Scotchgard branding procedure includes oil and water repellency before and after such abrasion. This establishes the Scotchgard Protector for leather as the best-in-class surface treatment with durable performances.
As a consequence, production of nubuck and suede via direct process is conceivable, reducing the long and expensive standard process via crust.
New chemistry and favourable environmental profile
The 3M fluorochemicals used in the treatment of leather are based on perfluorobutyl chemistry. When applied, dried or cured onto the leather fibres, the fluorochemicals tails orientate themselves away from the substrate conferring to the leather surface a low surface tension, allowing liquids to bead up and repel.
In the 1990s, it was found that the ultimate breakdown product (PFOS – perfluoro-octanesulfonate) of the perfluorooctanyl (C8F17-) based chemistry, which was used at that time in surface protectors, was being found in the environment, at very low levels. Although extensive research indicates that no health or environmental effects result from these breakdown products at these very low levels, it was decided by 3M to phase them out.
After significant R&D work, new leather protectors based on perfluorobutyl chemistry (C4F9-) have been developed. This new technology has a favourable environmental, health and safety profile. With the help of these new building blocks, it is possible to produce high molecular weight polymers that remain stable during the useful lifetime of the treated leather. Furthermore, the polymers are developed in such a way that they will contain very low levels of residual monomers that have the potential to degrade further to PFBS (perfluorobutanesulfonate).
Concerning the ultimate degradation product of this new chemistry, PFBS, test findings provide evidence that this substance is persistent, but it is not considered bioaccumulative or toxic under the US EPA persistent, bioaccumulative and toxic chemical policy. The acute ecotoxicity data show that PFBS would be classified as an insignificant hazard by the US NIOSH and requires no label warning by the EU regulations.
The necessity of branding for leather
Scotchgard Protector for leather is one the most famous brands applied in the leather industry. The high recognition level and reliability of Scotchgard Protector for leather and related performances are determining advantages for business opportunities. Brand differentiation is nowadays an outstanding solution for gaining new market shares.
Scotchgard Protector for leather and its dual action which offers stain repellency and stain release is the key solution in combining the appropriate leather treatments to match consumers’ expectations. To apply the Scotchgard brand to shoes, apparel or furniture; leathers must pass stringent specifications regulated by 3M procedures involving the most rigorous methods for leather surface protection assessment.
Distribution of Scotchgard Protector for leather
TFL are the authorised distributors of 3M protective materials for the leather industry. PM 4700 is an aqueous-based product for drum application, PM 4701 is an aqueous-based product for spray application and PM 4800 is a solvent-based formulation for spray application.
Keywords
Vulnerable leathers; footwear, apparel, furniture, gloving, fluorocarbons treatment; oil, water and stain repellency; keeps your leather looking good longer; favourable environmental profile; branding; determining advantages for business. Scotchgard Protector for Leather.
Acknowledgements
Special thanks to Dirk Coppens, Pierre Vander Elst, Hans Ulrich Schenk from 3M, Victor Callegher and Mike Donohue from TFL for their contribution to this article.
