COLOUR CONCENTRATE

Dyes are miscible with the polymer and hence do not have dispersion problems. They include many of the dyes that have been developed for dying fibres, e.g., azo and anthroquinone derivatives. They are particularly useful for transparent articles, e.g., automotive taillights, decorative film. They can be added either as a dry powder or as a colour concentrate (requiring 10-fold dilution). 

Anthocyanins are extracted commercially using either acidified water or alcohol. The extract is then vacuum evaporated to produce a commercial colour concentrate. The raw materials can be blackcurrants, hibiscus, elderberry, red cabbage or black grape skins. The most commonly used commercially are black grape skins, which can be obtained as a by-product. 

Hermann (2000) described a rapid automated method involving generation of a known amount of free radicals and the detection of the excess by photochemiluminescence. Test kits are available for determination of total water-soluble antioxidants, fat-soluble antioxidants and ascorbic acid. A luminometric method was developed for the determination of antioxidative activity and was subsequently applied to anthocyanin and betalaine colour concentrates (Kuchta et al., 1999). The method involved quantification of the interruption in luminescence from the hydrogen peroxide-horse radish peroxidase-luminol system in the presence of antioxidants. 

Samples Soft drinks (trade name) Colour Concentration (mg/1)... 

Coenen et al. [60,61] proposed a two-step extraction for the separation of pungent compounds and carotenoid fractions. Aroma- and pungent components were recovered at 120 bar and 40°C, and the paprika residue was re-extracted at 320 bar and 40°C to recover carotenoids. The solubility of capsaicin in carbon dioxide was relatively low at a pressure of 120 bar, so a great amount of solvent (for example 130 kg of CO2 per kg of paprika) was needed to recover the aroma components totally. The extraction time was 6.5 hour. In the separator the pressure was 56 bar and the temperature was 45°C. The orange, paste-like extract recovered in the first step was extremely pungent in taste. It contained water, and the yield was about 15%. In the second step, a relatively great amount of CO2 (approximately 50 kg/kg) was needed to recover the carotenoids in quantitative yield. The extraction time was 4 hours. The dark red, liquid colour-concentrate is without capsaicinoids. The yield was 2.5%. 

The most recent developments in pigmenting technology relate to ease of handling, dust free, colour concentrates (73) and dosing on line. Such technology covers encapsulation (385) and the use of polymer carriers (39, 321). 

The experiments were run with aqueous solutions prepared on a distilled-water basis. To simulate alkalinity and TDS, the following components were added calcium bicarbonate, 150 g CaCO m calcium chloride, 140 g Cl m and potassium sulphate, 130 g S0 m. Peat and clay extracts were applied to simulate colour (C) and turbidity (T). Three model solutions differing in colour and turbidity concentrations were used. Solution I was clear (T = 0) and showed a high colour concentration (C = 100 g Pt solution II was both... 

Fig. 2. Colour as a function of coagulant B dose and initial colour concentration in model solutions...

Colorants can be subdivided into dyes, and dispersed organic, inorganic and special-effect pigments. The technique for applying the colour to the product usually involves precolour (material that is already compounded to the colour desired), dry colour (powdered colorant), liquid colour or colour concentrate (high loading colorant in a base resin). 

Pigment dispersants are low molecular weight ionomers that can promote good pigment dispersion and come within the regulations of many countries for colour concentrates... 

Near-infrared (NIR) spectroscopy has become a commonplace analytical tool in the plastics industry. NIR techniques have made quantification of many organic components in polymer processing easy and quick. The work presented outlines the methodology for using NIR to measure stabiliser levels in colour concentrates and natural polymer formulations. Advantages and limitations are considered as well as particle size and product form. 4 refs. 

New developments Kasier forms for use/incorporation In compounds colour concentrates, liquid colours improved dispersibilty. better thermal stabilily replacement of heavy metals inlroduction of new chemisiry... 

High molecular weight poly(ethylene oxide)s find use as water-soluble packaging films and capsules for such products as laundry powders, colour concentrates, tablets and seeds. In solution, the polymers are used as thickeners in pharmaceutical and cosmetic preparations, textile sizes and latex stabilizers. 

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