Division BAT 7 In order to reduce raw material consumption and the overall environmental impact of the coating application processes, BAT is to use one or a combination of the techniques given below.
United Kingdom
| The selection of the application techniques may be restricted at plants with low throughput and/or high product variety as well as by the substrate type and shape, product quality requirements and the need to ensure that the materials used, coating application techniques, drying/curing techniques and off-gas treatment systems are mutually compatible. | |||
| Technique | Description | Applicability | |
|---|---|---|---|
| Techniques for non-spraying application | |||
| (a) | Roller coating | Application where rollers are used to transfer or meter the liquid coating onto a moving strip. | Only applicable to flat substratesf1. |
| (b) | Doctor blade over roller | The coating is applied to the substrate through a gap between a blade and a roller. As the coating and substrate pass, the excess is scraped off. | Generally applicable. |
| (c) | No-rinse (dry-in-place) application in the coating of coil | Application of conversion coatings which do not require a further water rinse using a roller coater (chemcoater) or squeegee rollers. | Generally applicable. |
| (d) | Curtain coating (casting) | Work-pieces are passed through a laminar film of coating discharged from a header tank. | Only applicable to flat substrates. |
| (e) | Electrocoating (e-coat) | Paint particles dispersed in a water-based solution are deposited on immersed substrates under the influence of an electric field (electrophoretic deposition). | Only applicable to metal substrates. |
| (f) | Flooding | The work-pieces are transported via conveyor systems into a closed channel, which is then flooded with the coating material via injection tubes. The excess material is collected and reused. | Generally applicable. |
| (g) | Co-extrusion | The printed substrate is coupled with a warm, liquefied plastic film and subsequently cooled down. This film replaces the necessary additional coating layer. It may be used between two different layers of different carriers acting as an adhesive. | Not applicable where high bond strength or resistance to sterilisation temperature is needed . |
| Spraying atomisation techniques | |||
| (h) | Air-assisted airless spraying | An airflow (shaping air) is used to modify the spray cone of an airless spray gun. | Generally applicable. |
| (i) | Pneumatic atomisation with inert gases | Pneumatic paint application with pressurised inert gases (e.g. nitrogen, carbon dioxide). | May not be applicable to coating of wooden surfaces. |
| (j) | High-volume low-pressure (HVLP) atomisation | Atomisation of paint in a spray nozzle by mixing paint with high volumes of air with a low pressure (max. 1,7 bar). HVLP guns have a paint transfer efficiency of > 50 %. | Generally applicable. |
| (k) | Electrostatic atomisation (fully automated) | Atomisation by high-speed rotational discs and bells and shaping the spray jet with electrostatic fields and shaping air. | |
| (l) | Electrostatically assisted air or airless spraying | Shaping the spray jet of pneumatic or airless atomisation with an electrostatic field. Electrostatic paint guns have a transfer efficiency of > 60 %. Fixed electrostatic methods have a transfer efficiency of up to 75 %. | |
| (m) | Hot spraying | Pneumatic atomisation with hot air or heated paint. | May not be applicable for frequent colour changes. |
| (n) | ‘Spray, squeegee and rinse’ application in the coating of coil | Sprays are used for application of cleaners, pretreatments and for rinsing. After spraying, squeegees are used to minimise solution dragout, which is followed by rinsing. | Generally applicable. |
| Automation of spray application | |||
| (o) | Robot application | Robot application of coatings and sealants to internal and external surfaces. | Generally applicable. |
| (p) | Machine application | Use of paint machines for the handling of the sprayhead/spray gun/nozzle. | |
Annotations
Footnotes
- f1
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The selection of the application techniques may be restricted at plants with low throughput and/or high product variety as well as by the substrate type and shape, product quality requirements and the need to ensure that the materials used, coating application techniques, drying/curing techniques and off-gas treatment systems are mutually compatible.