Masterbatches are concentrates made from pigments, dyes or additives in a carrier polymer. They are pre-mixed in mixers, compounded in an extruder and pelletised. Plastics processors then add them to the raw material during injection moulding, extrusion or film blowing. The same applies to both: anyone who frequently changes colours and formulations has to clean the equipment frequently, and that is precisely where the costs arise.
The typical challenges
- Colour changes and colour carry-over: Even small traces of the previous colour can lead to streaks, speckles or colour variations. The result is rejects until the system is running clean again.
- High temperatures and cracking: Processing in the extruder takes place at high temperatures, often in excess of 200 °C depending on the polymer. Residue that remains for too long in dead zones, on the screw, barrel, die plate or screen changer, decomposes and carbonises. These carbonised deposits eventually break away and appear as black specks in the granulate or in the finished part.
- Stubborn pigments and additives: Pigment dust and additive residues adhere to mixers, hoppers, dosing units and feed pipes. Some pigments, such as ultramarine blue, are considerably more difficult to remove than others.
- Committee and standstill: Every hour spent on cleaning is an hour lost to production. Every batch that fails to meet specifications due to carry-over is material that has to be rejected or reprocessed.
- Health and Safety at Work: Flammable solvents are often used undiluted for cleaning, requiring hazard labelling, explosion protection and protective equipment.
What cleaning methods are available?
| Procedure | What is it for? | Borders |
|---|---|---|
| Cleaning granules (dishwashing compound) | Extruder, screw and barrel during operation, whilst changing colour and material | It does not reach every dead zone or the parts of the system upstream of the extruder, and this in itself results in material and time wastage |
| Burn-out / Pyrolysis | Removed screws, nozzle plates, screens and perforated plates with severe cracking | Dismantling required; either by the manufacturer or a service provider; often followed by further cleaning |
| Blasting (dry ice, glass beads) | Tools, moulds, components | A blasting machine is required; not suitable for all surfaces |
| Mechanical (brass brush, scraper) | warm polymer residues on accessible parts | time-consuming, risk of scratches |
| Cleaner | Mixers, hoppers, feeders, dosing units, conveyor systems, dismantled parts, granulation, machine surroundings | Leave to act; clean only once surfaces have cooled down |
In practice, these processes work together. The cleaning granules flush out the extruder during a changeover, whilst the cleaner ensures that no traces of the old colour remain either before or after the extruder.
Where Eco-Nova can help
Eco-Nova does not supply cleaning granules. We supply the cleaning agents for everything the granules cannot reach, and the expertise to make the cleaning process as a whole quicker and safer.
| Plant section | Typical residues | Might be suitable |
|---|---|---|
| Heating/cooling mixers and mixing tanks | Pigment and additive residues, waxes | Microsolv |
| Hoppers, dosing units, feed pipes, silos | adhering pigment dust, granule abrasion | Microsolv NX |
| Parts removed after burning out or blasting | Film residues, oil, ash | RF Cleaner |
| Granulation: water bath, cooling section, cutting head | Oil, grease, pigment film | Microsolv Plus |
| Moulds and tools in plastics processing | Deposits, residues of release agents | Topclean |
| Mixing and metering heads in PU processing | cured polyurethane, polyol and isocyanate residues | Purex NF Labelled: Use only with protective equipment as specified in the safety data sheet |
| Cracked polymer residues on accessible parts | cured, hardened polymers | individual, during the consultation Cracking varies so much depending on the polymer, additives and temperature that we always work with you to find the right solution. |
These suggestions are a starting point. During the consultation, we will work with you to determine which cleaner and which process are best suited to your pigments, polymers and equipment, usually with free samples and a demonstration on your own equipment.
On top of that, there is what goes beyond the cleaner:
- On-site consultation: We’ll take a look at your colour change and identify the areas where residue is sticking.
- Tests on your system: in a direct comparison with your current cleaner, even on a large scale.
- Dilutable cleaners: Water-miscible cleaners such as Microsolv can be diluted depending on the level of soiling. This saves on cleaner and reduces solvent vapours.
- Cleaning products without hazard labelling: Many of our cleaning products are not classified as hazardous and serve as alternatives to flammable solvents.
- Evidence: Several cleaning agents have been certified by NSF or ISEGA, for example masterbatches for food packaging. Find out more: Compliance and Certificates.
- Our own recipes: If there isn’t yet a suitable cleaner for your task, we’ll develop one (Tailor-made).
From practice: Mixing vessels in masterbatch production
A masterbatch manufacturer was cleaning its mixing vessels using a flammable solvent labelled with three hazard pictograms – and using it undiluted. Following an on-site cleaning trial involving several free 10-litre samples, Microsolv proved to be the preferred choice. It removed pigment and additive residues more effectively than the previous solvent and, according to the safety data sheet, is not classified as hazardous. The customer now cleans easily soluble pigments using a diluted mixture, whilst for stubborn ones such as ultramarine blue, they use Microsolv in a higher concentration. Read the success story
Tips for faster colour changes
- Planning the order: If possible, produce from light to dark. That way, small leftovers are less of a problem.
- Start before the extruder: Clean the mixer, hopper and dosing unit at the same time. Otherwise, the next batch will carry the old paint over again.
- Understanding dead zones: Where encrustations form, it is advisable to clean at regular intervals before black spots appear in the product.
- Leave to cool: Only use cleaning products on surfaces that have cooled down. We will clarify with you in advance the temperature at which a cleaning product can be used.
- Balancing the four factors: Chemistry, mechanics, temperature and time all play a part. Find out more: The Sinners’ Circle.
Always follow the instructions in the safety data sheet. The safety data sheet is available on request to existing customers and to customers who have received a sample or attended a demonstration.
Is your colour change taking too long, or are you struggling with carry-over and black spots? Tell us about your production line and your formulations. Our technical advisers will recommend a cleaner, put together some free samples and, if you wish, visit you on site.