Thermaset offers powder coatings for every occasion
Thermaset offers powder coatings for every occasionKeywords: Minolta, Thermaset, Powder coatings, Photometers
Modern demand for colour choice has led to an explosion in the number of shades and hues available to manufacturers using metal finishes. With thousands of colours to choose from, and others produced daily for bespoke applications,it is vital that powder coating manufacturers can offer customers the range,speed, matching and flexibility that customers require.
The UK's Thermaset Limited, of Tamworth, believes that it has established an enviable reputation for excellence and innovation in the formulation and manufacture of thermosetting powders for electrostatic application. The company strives to maintain a cutting edge in the research and development of new materials and processes, and continuous testing takes place throughout the production cycle, so that any problems are spotted early. This goes for colour match, too. And this is where Minolta considers that it has one small, but vital, part to play in this programme of quality control and development.
Thermaset employs a Minolta CM-3600d bench-top spectrophotometer to match,compare and record the colours of metal finishes produced by its powder coatings. Before any product leaves the factory, it undergoes a series of final QC checks to ensure that the final material matches the customer's order. The company policy of total quality commitment to the customer implies "get it right first time, every time".
The basic manufacturing process consists of mix, extrude, cool and grind to finish with a uniform powder that can be applied to metal products electrostatically. The company uses over 4,000 colour standards, the formulations of the constituent ingredients being stored on a PC. Of these colours, around 1,000 are greys. For each formulation Thermaset maintains a record stored on proprietary colour matching software system on a PC linked to the spectrophotometer, so that samples can be tested and compared on the Minolta.
If a customer produces a coloured sample that he wants the company to match,the sample can be checked by the spectrophotometer and compared with those on the database to see if a formulation already exists. Checks are also made with the human eye against reference metal plates. A light cabinet is employed to compare these reference plates with the customer's sample. If there is no existing formulation, then Thermaset will develop a new formulation to fit the bill. The company promises to formulate and manufacture a new product to match a customer's specifications within five working days.
When planning the work ahead, the coatings are sorted into a production order by colour. The raw ingredients are purchased from all over the world, including the UK, Spain, Germany, Switzerland and Korea. Each formulation of plastic resin, titanium dioxide whitener, colouring pigments and special additives for the required surface finish, is then weighed into a large metal tub, where it is mixed. The resultant mixture is slowly introduced into the hopper of an extruder. The contents are heated as they are extruded to form a molten plastic,which is then poured between two large water-chilled cylindrical rollers, about 50cm in length and 30cm in diameter. This causes the plastic mixture to expand into a thin, wide sheet. By the time this reaches the end of a short conveyor belt it is a brittle solid, which is then broken into small, thin, irregular"tiles". The final stage involves the use of a microniser which grinds the tiles into a powder. Different powder coating applications require a finer or coarser grain, an average production size being around 40 microns in diameter.
The material is checked for quality at various stages in the process. Regular samples of the finished powder product are tested by spraying, using electrostatic deposition, on to metal test plates. The powder is stoved on to the metal surface at the appropriate temperature, typically at 180°C, and then checked for colour match in the Minolta spectrophotometer.
The Minolta CM-3600d spectrophotometer is a highly accurate, multi-function,front port instrument, designed for a broad range of colour measurement applications. Solid specimens for reflectance measurement are simply placed between the front port and a spring-loaded retaining plate. Different target masks can be selected with three aperture sizes: LAV 25.4mm, MAV 8mm and SAV 4mm.
The CM-3600d measures wavelengths between 360nm and 740nm with a 10nm pitch,and features Minolta's Innovative Optical System. This includes Numerical UV Control (NUVC), which is said to ensure fast and accurate calibration and simultaneous UV-included, UV-excluded and UV- adjusted measurements. Proprietary software on the linked PC provides numerical and graphical display of data as well as the ability to export to other applications. The spectrophotometer is said to meet the ISO and DIN standards for reflectance measurements, utilising d/8° geometry (diffuse illumination and 8° viewing). It also provides separate gloss control measurements, SCI (Specular Control Included) and SCE(Specular Control Excluded).
Inter-instrument agreement for the CM-3600d has a typical mean 
E*ab 0.15. Repeatability standard deviations for spectral reflectance are within 0.1 percent, and for calorimetric values within E*ab0.02.
According to Frank Savage, technical manager for Thermaset Limited, who also has responsibility for QC, the Minolta has proved invaluable as a rapid reference and quality checking tool. He commented:
Thermaset produces upward of 700 tonnes of finished product per year for a diverse range of applications. Our customers apply our powder coatings to finished goods such as bicycles, ovens and fridges, and shop-fitting and racking systems. We have seen a steady increase in demand over recent years, partly fuelled by the environmental benefits to be gained by our customers from the lack of solvent emissions. Thermaset is accredited to the internationally recognised ISO 9002 quality standard. The Minolta CM-3600d helps us maintain these high standards.
Details available from: Industrial Instruments Operation, Minolta (UK)Limited. Fax: +44 (0)1908 618662; E-mail: twalker@minolta.co.uk
