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New colorants and light-stabilizers for plastics processing |
Design – Aesthetics – Packaging
New colorants and light-stabilizers for plastics processing
Presented by Presented by Clemens Karg, Head of Performance Chemicals for Plastics
Trade Press Conference K 2004, June 22, 2004, Ludwigshafen, Germany
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Differing sets of requirements at different parts of the value chain, stiff competition and low economic growth are the main factors behind the pressure to innovate in the pigments and light stabilizers market. Product differentiation and cost reduction are therefore the two central goals when it comes to optimizing processes and developing new raw materials and applications.
It is against such a background that BASF is targeting its research efforts to meet market needs, developing new products that offer advantages along the entire value chain, as well as creating new applications. Three examples from the areas of fibre spinning, injection moulding and coatings will illustrate this (figure 1).
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FPV-tested pigments for the fibre industry
The fibres industry is the biggest consumer of mass-coloured plastics, accounting for around 30% of volume. In melt spinning, it would be fine if all that pigments did was to impart colour. Unfortunately, depending on their particle size and structure, and dispersibility, they can also adversely influence the spinning process. Blocked filters and fibre breaks cause long down-times, increase scrap rates and so add to costs (figure 2).
In order to prevent such problems, BASF was instrumental in the development and adoption of a standard measurement method for determining the dispersibilty – and therefore the suitability – of pigments for the mass coloration of fibres. This method was recently published as a European standard, EN 13900-5.
The method determines a characteristic filter-pressure value (FPV), the ratio of pressure increase during extrusion of a coloured polymer melt and the amount of pigment present. Pigments with FPVs of less than 2 are suitable for melt spinning, but in general, the smaller the FPV is, the better (figure 3).
BASF is the first manufacturer to market a set of pigments with a guaranteed FPV of 2 or less, representing a statement of the products’ suitability for fibre spinning. The range comprises five FP products in blue, green, scarlet and yellow. These pigments offer customers enhanced process stability with fewer fibre breaks and correspondingly lower production costs (figure 4).
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Low-warpage blue pigment for the injection-moulding sector
Freshly injection-moulded plastic parts can warp as they cool. There are many causes of warpage, one of them being the pigment-phthalocyanine ones especially.
BASF has developed a method to determine the extent of pigment-induced warpage, expressed as a ratio of the dimensions of a pigmented/ unpigmented part to those of the mould tool. The measurements are taken perpendicular to the direction of melt flow. The figure obtained is a measure of the warpage of a pigmented moulding compared with an unpigmented one.
BASF’s new phthalocyanine Heliogen® Blue K 7104 LW (LW for low warping) is a high-colour-strength pigment that has little influence on the warpage of injection-moulded parts. The benefits to customers are better process stability and correspondingly lower colouring costs. Moreover, the pigment is approved for food-contact applications and is not affected by changes to the moulding conditions. One typical application is bottle crates (figure 6).
Other low-warpage pigments are under development.
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Uvinul for automotive interior applications
The design of car interiors, as well as the choice of materials and colour scheme, is a decisive selling point and thus becoming increasingly important. Higher standards of appearance, haptic and aging properties of the materials used have led to a demand for new systems in recent years. In up-market vehicles the trend is away from slush coating with vinyl plastisols and TPO towards PU spraying and casting, as well as TPU powder slush systems (figure 7).
The extreme heat that can build up inside a vehicle on a hot summer’s day can cause the release of additives - such as light stabilizers - which condensate on the inside of the windscreen to form a haze, an effect known in the car industry as “fogging”.
The industry currently specifies that within a 16-hour period at temperatures between 100° and 120°C, emissions of light stabilizing additives must not exceed 2 mg per square metre of instrument panel; the long-term goal is a value of less than 1 mg. BASF’s light stabilizer Uvinul® 3039 combines low volatility with very good UV absorption properties, making it the current reference standard. This product is used by leading car makers for door trim and instrument panels. Another grade, the newly developed Uvinul 3460 is the first UV absorber on the market to achieve a fogging value of only 0.5 mg, while at the same time having very good absorption values (figure 8).
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