Finishing ideas from ALPA19 June 2004
Italian leather chemical producers, ALPA, are constantly coming up with new wet-end and finishing ideas. They have recently presented their latest finishing chemicals which include novel fashionable effects and new ideas for upgrading lower quality leathers. The nine latest finishing products provide the tanner with new finishing solutions which can be shown to customers and may make that all important 'new leather' that fashion or legislation requires. As with most new finishing compounds, ALPA produce mainly water-based products which are easy to apply either by spray finishing or rollercoater. Prefondal K 77: General purpose cationic ground for polish and plate finishing. The ready-to-use whitish liquid is a cationic sealer coat for use on both felt polishing and plating. Leathers treated with this product have a nicely sealed surface, an extremely natural surface look with a waxy touch and resistance to water spotting. Prefondal K 77 is particularly useful when softening dry grain in the crust without overloading the finish. This product is made up of oils, resins and waxes and can be used alone or in combination with other products. K 77 can be modified with cationic protein products and, in the case of a plated finish, the filming properties can be enhanced by the addition of cationic polyurethanes or acrylic resins. SFT COMP A 086: Compound designed to produce a natural appearance when upgrading leather during plating. Based on oily and waxy acrylic urethanes in a water dispersion, this product has a non-ionic (slightly anionic) charge and is a specific ground coat covering compound for full grain ironed finishes. It has excellent coverage properties and leaves the leather with a non-resin look and touch. The white liquid acts as a good compromise for semi-aniline finishing with good sealing properties and a natural look. ALPA recommend this product to be used on cow calf and cow side leathers for semi-aniline production. Casein combinations or nitrocellulose top coat emulsions can be applied on to this base product. It has a pH of 8.0 and a dry solids content of 20%. SFT Oil 29: Non-swelling darkening oil based on synthetic oils. This product is also self-emulsifying and does not contain solvents. The honey-coloured liquid is ideal for pull-up effects and good darkening effects can be achieved by ironing at high temperatures. The non-ionic compound may be applied to leathers such as pull-up upholstery articles in a pure form, non-diluted on to the crust. Following resting, the leather is passed through an ironing machine at 110°C and finished by spraying on an adhesion and top coat. SFT Oil SA: Pure synthetic base coat oil which is free of solvents. This product is a concentrated oil for ground coat finishing. The yellowish liquid is normally applied by rollercoater, spray or added pure or diluted 1:1 to 1:3 with ethylglycol or similar solvents such as methoxypropanol. SFT Oil SA gives the final leather a natural silky, greasy surface feel which is long lasting. It has a strong sealing power on the grain and can be plated using a hydraulic press or ironed using a roller press at high temperatures (120/140ºC). The oil is not sticky during plating and develops a good shine especially when polished or glazed using a stone or felt. It acts as a very good base to enhance the gloss and look of a casein finish. SFT Oil SA does swell in water and is good at hiding any defects. The final appearance of the leather is very bright, natural and transparent. Akral PU MF: Soft acrylic polyurethane compound for buffed leathers containing binders and fillers. Ideal for producing buffed leather with a full grain look known as 'Mezzofiore'. This compound has good covering characteristics and, after dry milling, presents a very natural final article. Akral PU MF is applied by airless spraying on leathers which have been buffed, milled and embossed. ALPA recommend using this product with 0.5% crosslinking agent, Alparet RU, to enhance the physical performance and Alpatop 10L as a top coat. The whitish, anionic liquid is ideal for upholstery leathers followed by dry milling overnight and roller press. Alpatop HDR Strong: Hard binder for 'crystal' and 'ceramic' finishing effects. Made from an acrylic copolymer, it is very hard and shiny. HDR Strong is ideal for producing leathers with an aged look with surface effects such as crystal or the micro-crystalline crackled finishing film. Depending on the type of crust used, this compound is applied by spray or rollercoater as an intermediate mixture and/or directly as the first finishing step. It can be applied to full grain or splits and produces a uniform shrunken film similar to a spider's web if applied as a heavy coat using a rollercoater. The anionic, creamy-coloured liquid may be applied with hard casein finishes depending on the desired effect. Alpatop S 10 L: Solvent-based polyurethane for top and intermediate finishing coats. It acts as an adhesion promoter for oil and wax upholstery finishes. It is a shiny nitro-urethane topcoat where high physical properties are required. Dry milling for several hours after applying Alpatop S 10 L will not affect the physical characteristics. The clear yellowish liquid has a flash point around 15ºC/DIN 52231 and can be diluted 1:2.5 with a lacquer thinner when used as a top coat. The addition of 1-2% of a crosslinker will also increase the physical properties even if S 10 L is used as an intermediate coat. It is useful as an intermediate coat to increase the adhesion on wax and oil coats for upholstery leather or to improve adhesion on pigmented, pull-up or waxy finishes. It can be applied by spray finishing. Alpatop S 11 Matt: A waxy, solvent-based, dull nitrocellulose auxiliary for top coats. The white liquid leaves the final leather with a good waxy touch and dulls down solvent-based top coats which require high physical characteristics. It may withstand prolonged dry milling and re-shines with rubbing or hot plating. The nitrocellulose in solvent solution has a flash point of 21ºC/DIN 52231 and may be added with a crosslinker or lacquer thinner to further increase the physical parameters of the leather. It may be applied in different quantities to produce either a dull waxy top coat or a semi-shiny top coat finish. Alpatop S 11 Matt has a dry content of 18% and may used in combination with Alpatop S 10 L (see above) in different proportions depending on the desired final effect. SFT Ground 03: A dull finishing polyurethane dispersion which is specific for rollercoater and spray applications. The beige liquid has excellent filling, levelling and sealing properties making it ideal for upgrading. The stucco properties contribute to improved smoothness of corrected grain with covering of defects without compromising the flexometer results of a resin finish. This anionic product may be applied to produce a more uniform and smooth finish to brush-off articles or cover deep defects on full grain leathers. On buffed articles after impregnation and re-buffing, SFT Ground 03 can be added pure or with a pigment by rollercoater to coat a film of 10g/sq ft due to the higher viscosity of the product. After overnight resting, leathers may be ironed (110-120ºC) and buffed (paper 400-500) and resin finished. The addition of SFT Ground 03 with resin grounds for spray finishing may be used to upgrade full grain articles. This is particularly effective due to its strong reactivity to hot temperatures occurring during ironing or printing. This product also provides a uniform seal during the finishing of split leathers by ironing at 120ºC.