How clean is your leather?23 January 2007
There are a number of causes which result in surface contamination but three key factors are machines, people and the material being processed. For example, slitters and buffers create slivers and dust particles, operators contaminate through skin flakes, hairs and clothing fibres, hides and conveyors generate static which attracts dust particles as they are processed.
Surface contamination affects all kinds of production processes and the leather industry is no exception. With production and material costs continually increasing, the issue needs to be addressed if a company is to remain competitive. It is uneconomic for leather manufacturers to invest in the type of clean rooms used in medical packaging and the electronics sectors. However, they need to be aware of the dangers of dust and other debris entering the production line. There are two key issues to be addressed - dust and static control. Dust is produced in a variety of tanning and finishing operations. Chemical dust can be produced during the loading of hide processing drums. Leather dust is produced during mechanical operations and buffing used to improve the final appearance of the leather is also a major source of dust. This dust may be impregnated with chemicals, as well as fragments of hair, mould and excrement. This is a major problem for leather processing because dust can cause both chemical, mechanical and cosmetic damage. The sharp edges of minute particles are abrasive and can cause fibre damage if removed by methods other than suction or soft rollers. Dust also attracts fungal spores and acts as a centre for condensation and subsequent chemical attack. Also, in this sector, appearance is everything. A black speck of dirt on white leather upholstery, if it manages to pass through quality controls, can severely impact on sales. The second issue to be addressed is static, which is created throughout the manufacturing process, and causes several problems to the leather industry. When a hide is first pulled from the pile of materials waiting to be processed, static is generated by the fibres in the material rubbing against each other. When the hides enter the production line and are buffed to get a lustre, this again causes more friction. As the hides are then placed on belts that carry them to the spray application, the high charges will attract dust and particles onto the hides as they travel down the narrow gauge belts, or perlons. This results in the hide holding onto particles as it passes below the commonly used air knife. The static generated on the hide may affect the spray coating and can also damage the spray nozzle. The dust or debris which has been trapped on the leather can severely affect yields as such corrupted materials will have to be destroyed. So what solutions are available? Currently, many leather manufacturers use blowers to remove dust and contaminants from the hides. However, these are not wholly effective, as they move the dust around rather than remove it completely. Contact cleaning systems are an efficient way to ensure high quality finishing, as they effectively remove dust and other particles from the materials before they enter the production line. Possibly the best overall solution is a two-step contamination removal process. This uses a special elastomer roller to remove contaminants from the product's surface down to one micron in size. The contaminants are then transferred on to a roll of adhesive film for disposal. The second stage involves passing the product through anti-static bars to avoid re-contamination. This equipment can easily be installed 'in-line' and the replacement of consumables is quick and easy. To remove static, static neutralisation bars and ionised blowers should be integrated into the production line. This will ensure that not only do the cleaned hides not recontaminate but also ensures there are no static discharges within the spraying area. The key benefit of having a production process free of static and contaminants is reduced waste, higher yields and ultimately higher productivity and profits. Microclean Technologies and their US partner Static Clean International specialise in contact cleaning and static neutralisation solutions for a wide range of industries including leather, packaging, bottling, labelling, cosmetics, printing, pharmaceutical/ medical and electronics. For further information visit http://www.microcleantech.com