Colour
Masterbatch Ltd
Colouring plastics with masterbatch
Contents
Colouring plastics with masterbatch 3
True colours .............................................................................................................................. 4 Why we need colours
Introduction to masterbatch .......................................................................................... 5 What it is and how it benefits processors
Recent developments ......................................................................................................... 6 Multifunctional Masterbatches
Choosing and using masterbatch ............................................................................... 7 What to use, when and how to use it
EU Legislation ..............................................................................................................................................7
What’s best? ............................................................................................................................ 10 A look at the basics
Service ........................................................................................................................................ 11 What to ask for and what to expect from a masterbatch supplier
Trouble shooting ................................................................................................................. 12 Fault finding guide to common problems
Glossary .................................................................................................................................... 14 Common terms Plastics nomenclature
Sources of information ....................................................................................................17
PrefaceThe first issue of this guide was produced in 2006 and since then it
has been reprinted a couple of times. This latest edition has been
updated and includes a new chapter on multifunctional masterbatches
and many new additions to the glossary.
My reasons for producing the original booklet remain unchanged
- during my 30 years plus experience of working with plastics in
technical and commercial roles I have found that often the most
frustrating problems are those which occur at the start of production
- after the material selection and the colour have been agreed. While
many of the issues raised can be resolved quickly and simply on-line,
I believe that prevention is better than cure and definitely more cost
effective.
This booklet introduces the subject of using colour and adding colour
to plastics. It explains in plain language how to choose and use
masterbatch, what processors should expect from a supplier and,
essentially, what information they require to deliver the right product
for you.
A troubleshooting chart that flags up the most common processing
problems and offers solutions is included. And to help unravel some
of the jargon there is also a glossary.
I do hope you find this book useful and if you have any comments or
think it can be expanded in any way please do get in touch.
Tony Gaukroger
Managing Director
Colour Tone Masterbatch Limited
Colouring plastics with masterbatch4
Colour is a powerful marketing tool. So it is no surprise that, used
strategically, colour sells. Yet as consumers we are notoriously
fickle about colour - green is considered to be unlucky for some, while
hospitals use it everywhere because they say it has a calming effect
on patients. Smart marketers use colour to create brand awareness
and maintain edge in highly competitive and fast-moving consumer
goods and industrial markets.
Modern plastics come in a riot of colours, of every shade and hue
imaginable. One of the best known authorities on colour is Pantone.
Founded in 1963 by Lawrence Herbert in the USA, the company
provides a system that facilitates the selection of colour and the sharing
of this information to reproduce any shade choice across a variety of
industries. A special tool, the Pantone Plastics Color System, allows
designers, manufacturers and suppliers to select, specify, control and
manufacture hundreds of colours using a set of colour chips ranging
from opaque to translucent.
Such an impressive array of colours was not always possible.
Discovered in the mid-1800s plastics offer some unique properties,
but originally colour was not a feature.
Alexander Parkes’ cellulose nitrate material, first shown at the Crystal
Palace International Exhibition in 1862, could be ‘made of the most
brilliant colours’, but was not.
Researchers generally agree that most material breakthroughs came
in the early 1900s. In 1907 Leo Baekeland, a New York chemist,
produced phenol formaldehyde, the first truly synthetic plastic,
known today as Bakelite. Although famed for its ‘fishy’ smell when
hot, Bakelite was widely used for electrical fittings in the 1930s, but
again these were not particularly colourful items.
Mouldings cast from phenol formaldehyde, made as rods and cut into
usable objects such as napkin rings and toast racks, were normally
amber coloured. In the UK, British Cyanide introduced a formaldehyde
moulding powder that could be produced in white and hence various
pale shades. Casein was also popular at this time and its ability to
accept colours led to its use for coloured fountain pens and fashion
buttons. In the 1940s walnut effect brown was still popular for radio
sets although ivory, black, jade-green, bottle-green, red and some
interesting mottled-effect colours were beginning to attract attention.
The period 1935 to 1945 witnessed the introduction of a whole
raft of thermoplastic materials including PVC, PA, PE, PMMA and
PS. Processing methods developed too and in the early 1950s
the extrusion technique for film gave birth to the ‘polythene bag’
industry.
Colourful plastics as we know them today, however, did not really take
off until after the war. Following the restrictions and privations of World
War II, demand for brighter and more colourful accessories increased
dramatically. The population craved bright cheerful clothing, kitchens,
cars and domestic appliances. Plastics were popular because they could
be converted into many forms and would accept virtually any colour.
Remember Formica - a laminated plastic widely used for worktops
and offered in an amazing array of patterns? Not to be outdone, the
ceramic industry adopted colourful plastics as a direct replacement for
existing materials and American designer Russell Wright introduced
melamine tableware in 1953.
Over the past 50 years the development of plastic materials, processing
techniques and applications has continued virtually unabated. Blues
and greens are always popular colours followed by yellows and reds
after which come violet shades.
Despite the impact of all these colours, however, there is one
surprising fact. Colours account for less than 10 per cent of pigment
consumption worldwide and white is the most popular colour by a
substantial margin, closely followed by black.
Pigments & dyesPlastics are coloured by adding pigments or dyes. Pigments tend
to be opaque and are virtually insoluble in plastics whereas dyes are
generally transparent and soluble (in most plastics but not polyolefins).
In general pigments are associated with a particle size range of ~0.01
to ~1 µm. Primary pigment particles obtained during production tend
to mass together to form aggregates and subsequently agglomerates,
the size and distribution of which are responsible for colour properties.
Agglomerates have to be broken down (colour development), wetted
by the base polymer and distributed homogeneously (dispersion).
Colouring with dyes involves dissolving the dyes in the polymer. In
every case solubility depends on the host plastic and the processing
conditions likely to be encountered.
Other factors that affect colour are the nature of the plastic and the
temperature at which it is processed.
Most plastics can be coloured but thermosetting materials (e.g.
phenolic) and high temperature (>260°C) processing engineering
thermoplastics (e.g. PPO), can alter the physical state of pigments;
changing or even degrading their colours.
The most widely used white pigment in plastics is titanium dioxide.
Other popular pigments for plastics are carbon black, iron oxide (Red
101), phthalocyanine blue (Blue 15), phthalocyanine green (Green 7),
plus a number of organic complexes and heavy metal salts.
True colours
Introduction to masterbatch 5
ConsumptionToday the 700,000 t of plastic colorants consumed worldwide each
year go to make up to 84m t of coloured plastic compound. Global
plastic consumption in 2005 is estimated at 130m t.
It is enormously difficult to put a figure on the quantity of coloured
plastics consumed in the UK. This is not too surprising because
there are numerous global sources of natural polymer, dozens of
pigment suppliers and about 50 masterbatch manufacturers in the
UK delivering material into hundreds of trade moulders and in-house
processors.
However, most material suppliers and processors agree that over 95
per cent of plastics are coloured and would amount to approximately
5m t of coloured plastics consumed every year.
No doubt the digital world will ensure that we have millions of colours
to choose from as well as the means to evaluate and translate them
into ideas.
Plastic materials and processing technology will continue to deliver
end products in any colour we like, although history tells us that the
majority will probably be coloured black or white!
Coloured plastics can be supplied as ready-to-use compounds.
Alternatively, processors - commonly injection and blow moulders,
profile, film, fibre and sheet extruders - can purchase natural polymers
and add colour during processing in their own plant by using pigments
dispersed in a solid polymer carrier known as a masterbatch.
MasterbatchSince their introduction in the 1960s masterbatches have steadily
penetrated the traditional coloured compound market.
A masterbatch is a solid concentrate of colour and/or performance
enhancing additives such as anti-static, UV stabiliser, metal deactivator,
etc., that is added to a base polymer to impart these attributes. It
is usually supplied in granular form, either as pellets similar in size
to most polymers or as miniature pellets, known as micro granules.
Alternatively, masterbatch can be delivered in ‘rough cut’ form - a
mixture of small shreds and chunks.
Two main types are offered - polymer specific and universal. Polymer
specific masterbatch is produced using the same base polymer group.
Universal masterbatch employs a carrier system that is capable of
carrying the high quantities of additives necessary to deliver the end
use properties required as well as affording the essential compatibility
required across a broad range of polymers.
Universal masterbatches are normally readily available from stock,
in small quantities and are cost effective if used correctly. However,
in terms of compatibility, they are a compromise and processing
difficulties can arise with some materials and engineering polymers
that may have to be pre-dried. They are not recommended for use
at high dosage levels as the appearance or physical properties of the
final product may be adversely affected.
Conversely, polymer specific masterbatch, which can be pre-
dried with the host polymer, may be added at high loading without
compatibility problems. However, only a limited range of colours is
generally available and not all engineering polymers lend themselves
to conversion to masterbatch.
Masterbatch formulations normally include:
• pigment-upto65percent
• polymercarrier-35to50percent
• dispersingaids(waxes/stearatesetc)
– up to 10 per cent
• filler
ManufactureIn simple terms masterbatch manufacture is a two-stage process:
gathering the ingredients and then mixing them by applying heat
and shear to produce an homogenised pellet. Generally high or low
speed mixers are used to produce a pre-mix of the additives which
is then compounded on roller mills, kneaders, single or twin screw
extruders. Even distribution (dispersion) and development (breaking
down) of the additives throughout the carrier are essential. This
processing depends on several key elements: formulation, the quality
of raw materials, mixing and the compounding plant. Finally, the mix
is pelletised (die-face or strand cut) or ground.
Colouring plastics with masterbatch6
Composite masterbatches that combine colour with functional
additives, for example UV stabilisers, anti-oxidants, anti-stats
etc., have been available for many years and are usually created
at a processors request. More recently, however, multifunctional
masterbatches have been developed where the masterbatch
contains the colour and carrier as usual but, more importantly, also
incorporates process enhancing additives as well.
These process enhancing additives work in a variety of ways. Most
are polymer specific and their general purpose is to speed up the
subsequent manufacturing process, in effect to optimise whatever
process is utilised to convert polymer granules to end product. They
can be applied in a number of ways.
Successful formulation of a multifunctional masterbatch offers two
benefits to the processor. It fulfils their expectations of a colouring
solution and, due to improved production, it creates added value.
This additional value demonstrates that the masterbatch supplier has
more to offer than just a colouring solution. Being more creative is an
important asset in a market that is increasingly competitive and the
progressive masterbatch manufacturer should be working with their
customers to ensure they are aware of the latest developments in
process technology. This approach has been actively promoted by
BASF with their ‘Help our customers to be more successful’ strategy.
Additives that can be utilised in masterbatches to improve the
processability of a compound include:-
1. Lubricants, which in very simple terms can be categorised as either
internal or external types. Internal lubricants modify the viscosity of
the melt. Chosen for their compatibility [being readily soluble] to the
host polymer they improve flowability by changing the molecular
weight and so avoid any of the undesirable effects of changing the
melt viscosity. Obviously, care has to be taken when the application
is blown film, blow moulding etc. where the extruded parison has to
have great strength. Also, over-lubrication gives screw slip, which is
detrimental to productivity and product quality. An appropriate level
of internal lubrication however can improve throughput and hence
efficiency. Typical internal lubricants include polyolefin waxes, fatty
acid amides and esters, metallic stearates etc.
External lubricants are by definition incompatible with the host polymer
and migrate to the polymer/metal surface interface during processing.
Again, the type of lubricant is dictated by the host polymer and this
kind of lubrication can benefit the process by reducing frictional drag,
aiding ejection of moulded components and preventing melt fracture.
Care has to be taken not to over-lubricate to avoid problems such
as plate-out, reduced weld strength and poor printability. Typical
external lubricants include oxidised polyethylene wax, amide waxes
and fluoropolymers.
Generally, combination lubricant packages are more effective than
single lubricants, probably due to the variety of efficiencies obtained
at the different operating temperatures of each of the individual
lubricants. Another benefit is that many of these lubricants assist in the
breakdown of pigment agglomerates into primary particles during the
masterbatching process, so helping to achieve the good dispersion
and maximum development of the colour: essential to ensure the
most effective use of the pigment.
2. Nucleating agents are of particular importance in injection moulding
applications. Their incorporation results in higher crystallisation
temperatures and/or faster rates of crystallisation, which reduces
cycle times. Nucleating agents can be inorganic [calcium carbonate,
talcs, silica, etc.] or organic [salts of carboxylic acids, montan waxes
etc.] compounds. Some polymers can also be used as nucleating
agents, depending on the host polymer. Nucleating agents tend to
be polymer specific and those that can be used across a range of
polymers tend to have different levels of effectiveness in each.
3. Proprietary multifunctional additives are becoming more common.
Individually developed for specific polymers or applications, often their
exact makeup is confidential. Supplied in additive or masterbatch
form [Moldwiz, Timecut etc.] they are usually claimed to improve
processability, improve outputs and other visual and physical
properties. Incorporating them online into a coloured masterbatch
does have the advantage of being able to see where they are!
To be in a position to address all these points implies an intimate
relationship between the masterbatch supplier and the processor.
Indeed, it might be that, some companies would be happier working
under the formal umbrella of a secrecy agreement. It also requires
the masterbatch supplier to have a good working knowledge of his
customer’s processes. Consistency, repeatability, minimal rejects
and cost effectiveness should all be taken into account. Evaluating
each part of the whole manufacturing process and then designing
the colour and additive package accordingly can deliver worthwhile
benefits to the processor.
In this way the colouring package can be tailored to the manufacturing
process to achieve optimum efficiency and also decrease the number
of rejections. If the reject rate can be lowered it should be possible to
tighten the QC limits. Also, the sampling frequency [based on levels
of confidence] can be lowered. The net result of these benefits is
producing a ‘better’ product.
Developing masterbatches in this way should deliver improved
efficiencies and cost effectiveness benefits to both processor and
masterbatch supplier.
Recent developments – Multifunctional Masterbatches
Introduction to masterbatch 7
Choosing masterbatchMasterbatch offers processors an easy and convenient way
of adding colour and/or performance enhancing additives to natural or base polymers on their own plant. This technique delivers a compelling combination of cost savings and technical benefits including reduced stock holding of compounded material, reduction in cleaning costs, optimum dispersion and hence reliable colour and performance properties in the finished product.
The benefits can be summarised as follows:
• Lowstockholdingcomparedwithpre-compoundedmaterials
• Optimumdispersionofpigments/additives
• Dustfree,nohealthandsafetyrisksincomparisontoundispersedfine powder pigments or additives
• Elimination of ‘trial and error’ development or formulationwork, as this is done by the masterbatch supplier who takes responsibility for colour and consistency
• Reductioninpurging/cleaningcosts
Other considerations:
• Buyingbespokecolouredcompoundstiesthecustomertothesupplier who holds the formulations for the colours
• Usingmasterbatchallowstheprocessortonegotiatethepriceof natural polymer with a number of suppliers to obtain the most competitive price
• Duetothewideravailabilityofnaturalpolymerthemanufacturercan order ‘Just in Time’ to suit order in-take
There are technical benefits too. Because the pigment has already been blended, developed and dispersed in the host polymer it is easier to achieve optimum additive dispersion, i.e. consistent colour, in the finished compound. Additives, such as lubricants that improve processing, and those that enhance performance, such as UV stability, can also be added via the masterbatch.
Another consideration, often overlooked, is the benefit to health and safety through working with dust-free masterbatch pellets rather than handling fine particle size pigment powders. Masterbatch is usually supplied in granular form, either as pellets similar in size to most polymers or as miniature pellets, known as micro-granules. Alternatively, it can be delivered in ‘rough cut’ form - a mixture of small shreds and chunks.
As mentioned earlier, two main types of masterbatch are commonly available: polymer specific and universal.
Technical considerationsOriginally, universal masterbatches were designed to offer a commodity colouring solution for plastics, predominately polyethylene, polystyrene and flexible PVC. However, they are now also extensively used in engineering polymers where they can adversely affect physical properties such as impact and tensile strength if used incorrectly. Another factor to consider is that some pigments interact with certain polymers, for example phthalocyanine blue or green interferes with the crystallinity of polyolefins which manifests as shrinkage and/or distortion problems.
For optimum performance, engineering polymers must be processed dry. It is common practice to pre-dry polymer specific masterbatches with the host polymer. This is not possible with universals due to their lower melting points. However, only a limited range of colours is available generally and not all engineering polymers lend themselves to conversion into masterbatch.
Over the past 10 to 15 years, developments in processing machinery, electronic process control, polymer and additive technology, have made it easier to incorporate large quantities of pigment into base polymers and so produce stronger (more highly concentrated) masterbatches. Modern compounding extruders distribute and develop additives more efficiently than earlier machines and as a result it is now possible to produce masterbatches in a wider range of polymers.
Masterbatch can be introduced to the processors’ base polymer on the production line in a number of ways. The most successful methods are volumetric and gravimetric dosing. In both techniques the masterbatch is added directly into the polymer stream immediately before processing. Volumetric dosing has the advantage of relatively low capital investment but requires calibrating every time the batch or colour is changed (depending on the bulk density of the material). Gravimetric dosing is extremely accurate but the equipment is more expensive.
Colour, wall thickness and opacity requirements all affect dosage. Although influenced by homogenisation and dosage level, getting the loading right for the production of transparent colours is particularly tricky as any imperfections are clearly visible. Sometimes it is useful to go for a weaker masterbatch so the demands on homogenisation and dosage are reduced.
Generally dosage rates vary between 1 and 5 per cent by weight depending on opacity and the desired end-use properties.
Colouring plastics with masterbatch8
What to use End use will always influence the type of masterbatch chosen.
Other typical determining factors might be service conditions
such as ‘weatherability’ or light fastness, for example.
Toys and food packaging have to be produced from materials
made with ‘controlled’ ingredients and engineering products
will demand reliable high performance properties. Typically, an
off-the-shelf masterbatch formulation, chosen for colour but
incorporating premium priced additives for high specification
polymers, when used in an ‘uncontrolled’ application in a
low temperature commodity polymer, would be grossly over-
engineered and unnecessarily expensive.
When to use itInjection moulding, blow moulding, profile extrusion, sheet
extrusion, film extrusion, cast film, fibre and calendered sheet
processes commonly employ masterbatch.
A basic method of determining whether you will benefit from
using masterbatch is to consider that small lots of coloured
compound invariably carry a surcharge. Further, if you are
using several colours in the same base polymer, especially if it
is an engineering polymer, you should explore the cost of using
masterbatch. Also, look at the cost of stock holding tonnes of
coloured compounded material and weigh this up against using
the space saved by installing a plant that contributes to profit.
Although masterbatch is more expensive than compound it has
the potential to save hundreds of pounds per tonne against
compounded materials.
Moreover, there are many different masterbatch suppliers to
choose from, so you should be able to find one that offers
quality and service to match your exact requirements.
EU legislationColouring plastics is becoming increasingly complex. With
mounting EU legislation controlling the use of pigments and
additives, choosing the correct colour to meet legal and
application requirements as well as optimum cost is both
critical and complicated.
In some instances it is mandatory to use certain pigments while
for other applications lower cost alternatives are acceptable.
Get it wrong and the end product might not be fit for purpose
or, worse still, illegal. Either way the directives present problems
for end users, processors and compounders as well as
masterbatch manufacturers.
Although designed to protect consumers or the environment,
the problems lie in interpretation of the directives which can
easily lead to confusion. It’s a minefield for manufacturers. For
example, the use of chrome yellow to colour a PP beach bat
would be illegal if the product was classified as a toy. If defined
as sports equipment this pigment would be acceptable. A
nylon moulding coloured with food approved cadmium yellow
would be perfectly acceptable in a food processing product
as long as it did not conflict with rules on the use of colours in
electrical appliances.
As one of the aims of the legislation is to promote recycling,
manufacturers have to ensure they use colourants that are
acceptable. The chrome yellow pigment mentioned earlier
could not, for example, be used in electrical, automotive or
packaging applications because it would offend recycling
conventions.
A situation where plastic components have to be classified
either as packaging or part of a product is not as simple as
it sounds. Is a video cassette box (library case) packaging or
is it a product? When it comes to disposal, is a ‘grow bag’
packaging or an intrinsic part of the product?
Processors and end users can protect themselves by taking
a number of precautions. A system that will enable them
to keep up to date with current and future legislation is
essential. Additionally, it’s important to track developments
with suppliers and professional bodies such as the British
Plastics Federation and the Trading Standards Office. Critically,
all the companies in the product and manufacturing chain
should implement a process that allows them to accurately
classify the end use of the items they intend to manufacture.
Masterbatch companies in particular have to know the
intended use of products so they can create cost competitive
formulations that comply.
One of the aims of ISO 9001:2000 accreditation is to ensure
we all make products that are legal and fit for purpose. EU
legislation which is ambiguous simply makes the task more
difficult.
Whatever you do, remember the rules don’t just apply to new
colours. So don’t be tempted to use old stocks of universal
masterbatches without talking to someone who’s up to speed
on the legislation.
Choosing masterbatch 9
Cost savingsA company extruding PVCu tile edging strips has a stock range of 50 colours and its coloured compound supplier will only supply 1t
lots minimum of these colours - even though the company requires only half of this amount to produce orders that meet demand. The
company is therefore forced to accept a minimum raw material requirement for stock colours of 50t.
Alternatively, adding 2% masterbatch to natural (uncoloured) polymer the colour masterbatch requirement is 50 x 2% =1t plus an appropriate
quantity of natural polymer to which the colour must be added.
In this example it would be reasonable to assume that with the change over to natural polymer the compounded material stockholding would
reduce by 50%, delivering a significant saving on cash flow and cost of storage.
Cost example:
Blue PVCu compound:
Purchased in 1t lots .......................................................................................................................£1070.00 per tonne
2% Blue masterbatch purchased in 20kg lots @£6.00 per kg
Add on cost per tonne ...................................................................................................................£120.00
Plus natural PVCu ..........................................................................................................................£870.00*
TOTAL ...........................................................................................................................................£990.00 per tonne
Savings:
£80.00 per tonne on PVCu compound*
Increase in working capital freed up 25 tonnes less stock:
25 x 1070 .....................................................................................................................................= £26750
*The company would be buying the natural polymer in bulk:
20t lots @ £870.00 PMT
Prices based on average costs October 2008
What’s best?So now you want to produce plastic parts in a number of
colours and use masterbatch to achieve a good, cost effective result. This is easy to say and, with due consideration of a few material facts, is relatively easy to do.
First, what masterbatch should you use? A number of factors will influence your choice but the most important consideration is the base polymer of the masterbatch.
As mentioned earlier there are two types of masterbatch: universal and polymer specific. Universal types are convenient to use. They work in most polymers, can be used at low dosage levels, are readily available in a range of standard colours, and in small quantities.
However, they do have limitations. It is essential to check that the colourants in the masterbatch are suitable for the material you plan to mould. In addition, universal masterbatches generally have low melting points and this means that they cannot be pre-dried with polymers. Another consideration is overdosing as this can lead to compatibility problems that manifest as reduced physical properties and poor appearance in moulded products – not to mention the additional cost of using more masterbatch than is required.
Another dilemma is that the perceived versatility of universal masterbatches encourages moulders to purchase them in the belief that any surplus can be used again on another job. In reality, colours are rarely re-used and bags of material simply pile up in the materials store. It does not help that with universals the final shade imparted will vary depending on the material to which it is introduced.
Conversely, compatibility is less likely to be a problem with polymer specific masterbatches. Further, this type of masterbatch can be pre-dried with suitable polymers and this is especially useful if you are processing engineering polymers. Some producers offer small lots of custom colour matched polymer-specific masterbatch in 24 hours, so lead time is not an issue.
Another essential consideration that affects the choice of masterbatch type is mouldings with thin wall sections. If opacity is required, dosing levels can be high and this means that excessive amounts of the carrier resin are added to the moulding material and this may change its physical characteristics.
Having chosen the masterbatch type the next major decision is how to add it to the material you will be moulding. The choices are to manually mix pre-weighed masterbatch and polymer prior to filling the machine hopper, or use in-line volumetric or gravimetric dosing equipment to add predetermined amounts of masterbatch to known quantities of polymer.
Either way, it is important to ensure that the machine on which the processing is to take place is presented with evenly distributed masterbatch. Smaller granules amount to better distribution in the polymer being processed. However, while the particle size of the masterbatch should be similar in form to the host polymer it should not be so small as to fall to the bottom during mixing. In addition, the quantity of masterbatch (dose level) should be within the capacity of the dosing machine and should take into account shot weight. This can be critical because if your shot weight is, for example, two grams and you are adding masterbatch at 1 percent it amounts to a mere 0.02 grams of masterbatch. If you think of this as one granule per hundred granules of polymer, you can see that dosing has to be finely controlled.
How much masterbatch should be added? The ideal dosing level is determined by a number of factors. As mentioned above small shot weights benefit from higher doses of weaker masterbatches because this helps to ensure even distribution from shot to shot. The age and efficiency of moulding plant can also be an important factor. Expecting homogenisation of a 1 percent masterbatch by a 20-year-old machine that has never been serviced is wishful thinking!
In reality, the amount of actual colourant required is governed by your customer’s requirements for wall thickness, opacity, colour and application. These considerations directly affect dosing levels and hence masterbatch type. For instance, a thin wall HIPS container may require 4% titanium dioxide to achieve the opacity required by the customer. Obviously this is not going to be achieved by using a universal masterbatch (typically 70 percent TiO2) at 1 percent!
Personal preferences are also important. Using small quantities of strong universal masterbatch is extremely cost effective, whereas, the level of control with a weaker (cheaper) masterbatch is greater and can be readily fine-tuned to achieve optimum processing.
10 Colouring plastics with masterbatch
Service 11
Service
Colour required – your colour referenceCompany/department internal reference – this is important as it helps to avoid confusion with any subsequent colour matches.
ProcessInjection moulding / blow moulding /profile extrusion / film extrusion / sheet extrusion.
Quantity Ammount of polymer you need to colour in kgs/tonnes.
Preferred type of masterbatch:Universal.
Polymer specific.
ApplicationWill it be used for toys or packaging?
Will it be in contact with potable water?
Does it need to be FDA approved?
Will RoHS & WEEE directives need to be
taken into account?
Does it need to be free of heavy metals?
Does the masterbatch need to include any performance enhancing additives such as antistatic, slip, UV stabilizer, or antioxidant?
Is it going to be used indoors or outside?
What form of supply is expected? A colour plaque?
Material sample? (check the minimum quantity offered by the supplier).
Time frame - how soon do you expect to see plaques/samples?
Polymer the masterbatch will be used inProvide as much detail as possible. Brand name, grade number as well as generic polymer type. This information is essential if you plan to colour an engineering polymer.
State the colour standard you wish to work to, for example: RAL/BS/Pantone colour reference number or some other standard?
Lastly and most importantly, do not be tempted to over specify what you need. As this has an escalating effect on costs! Ensure you meet only the requirements of the application.
Once you have approved your colour the masterbatch should be produced within a few days.
Colour Tone offers a same day colour matching service for universal and commodity polymers, engineering polymers as well as custom additive blends. Orders are generally despatched within 48 hours (depending on quantity) although we can, at a push, deliver sufficient material to get production started within 24hours.
Many, but not all, masterbatch producers have the capability to formulate in a wide range of materials covering universal, special effect, engineering polymers and polymer-specific masterbatches.
Shown below is a list of the most common types of base polymer, the form in which masterbatches are normally supplied and typical minimum quantities.
All masterbatch suppliers offer a colour matching service. The speed at which they respond with a quotation or return a match will depend upon the complexity of the colour required and the
information you give them. If you have a colour that you would like the supplier to match you will need to provide the following information along with a sample if you have one.
Material Colour match Form Dosage* Minimum quantity
ABS same day pellet 2% 25kgs
SAN same day pellet 1% 25kgs
PA same day pellet 1% 25kgs
PC same day pellet 1% 25kgs
PE-HD/LD/LLD same day pellet 1% 25kgs
PBT/PET same day pellet 1% 25kgs
PP same day pellet 1% 25kgs
PS-GP/HI same day pellet 1% 25kgs
PVCU/PVCP same day pellet 1% 25kgs
ACETAL (POM) same day pellet 1% 25kgs
Colouring plastics with masterbatch12
Injection mouldingtroubleshooting
Burning Check set temperatures Check heat stability of masterbatch Reduce holding pressure Reduce holding time Decrease injection speed Improve tool venting Increase gate size
Colour inconsistency Check dosing and dosing level(between shots) Improve pre-mixing or blending Check no bridging in the throat Check set temperatures Check heat stability of masterbatch ‘Dirty’ streaks or specks Check set temperatures Check heat stability of masterbatch Check feedstock for contamination Clean and purge machine
Dispersion (poor) Improve pre-mixing or blending Improve temperature profile in the barrel Increase back pressure Reduce screw speed
Flashing Reduce injection speed Reduce injection pressure Reduce barrel temperatures Reduce tool temperature Check shot size
Flow lines Increase injection speed Increase injection pressure Increase back pressure Increase barrel temperature Increase tool temperature Improve tool venting Check feedstock for contamination Check material is dry
Injection moulding troubleshooting 13
Hang-ups (ejection difficulties) Reduce barrel temperatures Reduce tool temperature Reduce holding time Reduce injection speed
Lamination Increase barrel temperatures Increase nozzle temperature Increase tool temperature Increase screw speed Reduce injection speed Reduce back pressure Open up the gate
Screw not returning Check feed from hopper is unobstructed and not bridging Increase screw speed Reduce back pressure Check polymer is dry
“Short” shots Check shot capacity/size Increase injection pressure Increase injection speed Increase barrel and nozzle temperatures Increase mould temperature
Silvering Check feedstock is dry Check feedstock for contamination
Sinks or voids Increase holding pressure Increase holding time Reduce tool temperature Reduce barrel temperatures Increase nozzle temperature Reduce injection speed Check shot capacity/size Modify gate
Warping Increase barrel temperatures Increase injection pressure Increase back pressure Increase injection speed Reduce holding pressure Weld lines Increase barrel and nozzle temperatures Increase tool temperature
Increase injection speed Improve tool venting
Colouring plastics with masterbatch14
GlossaryBleeding - where parts of the colouring constituents either stain
an adjacent contact material or are released into a surrounding
solvent.
Blooming - migration of pigment particles in the component to
the surface which results in a ‘haze’ or bloom to be present on
the surface of the product. Generally confined to a few organic
pigments this effect can take some time to develop.
Blue Wool Scale - (ISO 105-B01-1988) is a means of measuring
the colour fastness to natural daylight of a colour by comparing
it to a blue wool standard. Expressed as 1-8, where 1 is the
lowest value, the next digit corresponds to twice the fastness
level of the previous digit. i.e. double the exposure time at the
same exposure level.
Colour Index - a system of classifying colourants by their
chemical type. Hence titanium dioxide is C.I. Pigment White 6
and fluorescent yellow is C.I. solvent yellow 93.
Dispersing aids - additives incorporated into the masterbatch
formulation to aid dispersion and development of the active
constituents. These can work in a number of ways, reducing
friction, wetting the pigment, helping to break down pigment
aggregates, improving melt rheology, lubricating the particles
to name a few.
Dispersion - defines the quality of the distribution of the colour
in the polymer matrix. Usually referred to in the general terms
of good and bad. In metallic and pearl colours can also be
(erroneously) applied to the streaking caused by the pigment
platelets being orientated in different directions.
Dyes - powdered colourants that are soluble in the polymer
matrix (see pigment).
Fillers - solid additives, usually inert inorganic compounds (e.g.
Chalk, Talc etc) added to plastics and masterbatches to increase
polymer bulk or reduce costs. Some fillers are incorporated
to produce specific physical properties (reinforcing fillers) in
polymer compounds.
Grey Scale - (ISO105-A02-1987) is a scale from 1-5 (Where
5 is no change) used to describe colour change due to
weathering.
Heavy metal pigments - the coloured salts of heavy metals that
make good, economical pigments. Concerns about heavy
metals in the waste/recycling chain have led to their control
in some applications and their replacement with organic
substitutes.
Homogenisation - the term to describe the evenness of mixing
of the constituents in the compound.
Lamination - occurs when there is stratification of the polymer
due to poor homogenisation of the masterbatch. Usually
a processing problem, it is often blamed on masterbatch
incompatibility.
Let Down Ratio (LDR) - the level at which a master batch is
incorporated into the base polymer. Hence an LDR of 3 (%) is
97 % polymer, 3% masterbatch.
Melt fracture - describes the alternation of adhesion/slip
between the side of the barrel on processing plant and the
extrudate giving a ‘sharkskin’ effect on the products, especially
film and profile or hose extrusions.
Metamerism - a the term to describe the phenomena when
two colours are a good match under one illumination but are
not a good match when illuminated under a different light
source. This is due to different pigment combinations in the
composition of each colour and the different absorption and
reflection characteristics of each pigment under the differing
illuminations.
Migration - a term applied to the mobility of colourants usually
attributed to the partial solubility of one of the components of
the colour. It can appear as ‘bleeding’ or ‘blooming’.
Multi-functional masterbatches - composite masterbatches
that combine colour with functional additives, for example UV
stabilisers, anti-oxidants, anti-stats.
Pigment - powdered colourants that are dispersed through the
polymer matrix (see dyes).
Plate out - this is the separation of components of a material
while being processed on the hot or cold metal surfaces of the
processing equipment. It appears as staining on processing
equipment and is sometimes referred to as ‘mould staining’.
Glossary 15
ABS acrylonitrile-butadiene-styrene
ASA acrylate-styrene-acrylonitrile
ATH aluminium trihydrate
BDS butadiene-styrene block copolymer
BMC bulk moulding compound
BOPP biaxially oriented polypropylene
BR butadiene rubber
CA cellulose acetate
CAB cellulose acetate-butyrate
CAP celluse acetate propionate
CE cellulose
CMC carboxymethyl celluse
CN cellulose nitrate
CP cellulose propionate
CSM chopped strand mat (or)
chlorosulphonated polyethylene
(rubber)
DMC dough moulding compound
ECTFE ethylene chlorotrifluoro ethylene
copolymer
EPDM ethylene-propylene-diene monomer
(elastomer)
EPM ethylene-propylene rubber = EPR
EPR ethylene-propylene rubber = EPM
EPS expanded polystyrene
EVA ethylene vinyl acetate
EVOH ethylene vinyle achol
FEP fluorinated ethylene-propylene
FRP fibre reinforced polyester/plastics
GMT glass mat thermoplastic
GPPS general purpose polystyrene
GRP glass reinforced plastic
Usually it is attributed to a limited compatibility of part of the
formulation
Polymer specific masterbatch - a masterbatch where the carrier
for the colourant(s) or active additives is the same polymeric
type as the polymer it is to be used in (see universal).
Slip - as the name implies this refers to the ‘slippery’ nature
of a polymer surface (low co-efficient of friction]. Also used to
describe a family of additives that increase this property.
Universal masterbatch - a highly concentrated masterbatch
where the ‘carrier’ or ‘binder’ is formulated from ingredients
selected for their compatibility with a range of polymers
enabling it to be used in a number of polymers.
Weld line - the meeting of two material flows in a moulding
where the pigment is not aligned in the same direction as the
majority of the material, which results in an unsightly boundary
line. Particularly prevalent in metallic and pearl colours.
Polymers – Plastics – Rubbers
HDPE high density polyethylene
HEMA hydroxyethyl methacrylate polymer
HIPS high impact polystyrene = TPS
LCP liquid crystal polymer = SRP
LDPE low density polyethylene
LLDPE linear low density polyethylene
MBS methacrylate-butadiene-styrene
terpolymer
MDPE medium density polyethylene
MF melamine formaldehyde
NBR nitrile rubber = acrylonitrile butadiene
rubber
NR natural rubber
OPP oriented polypropylene
PA polyamide = nylon
PA 11 nylon 11
PA 12 nylon 12
PA 46 nylon 46
PA 6 nylon 6
PA 610 nylon 610
PA 66 nylon 66
PA 66/610 nylon 66/610 copolymer
PAA polaryl amide
PAI polyamide imide
PAN polyacrylonitrile
PB polybutylene
PBT polybutylene terephthalate = PTMT
PC polycarbonate
PE polyethylene
PEBA polyether block amide
PEEK polyetheretherketone
PEEL polyester elastomer
PEI polyester imide
PEK polyetherketone
PES polyether sulphone
PETG PET copolymer
PETP polyethylene terephthalate
PF phenol formaldehyde
PFA perfluoro alkoxyl alkane
PHB polyhydroxybutyrate
PI polyimide
PIR polyisocyanurate rigid (foam)
PMMA polymethyl methacrylate
PMP polymethyl pentene
POM polyoxymethylene
PP polypropylene
PPE polyphenylene ether
PPO polyphenylene oxide
PPS polyphenylene sulphide
PPSS polyphenylene sulphide sulphone
PS polystyrene
PSU polysulphone
PTFE polytetrafluoroethylene
PTMT polytetramethylene terephthalate =
PBT
PUR polyurethane
PVA polyvinyl acetate
Colouring plastics with masterbatch16
PVB polyvinyl butytral (butyrate)
PVC polyvinyl chloride
PVCC chlorinated polyvinyl chloride
PVCP polyvinyl chloride plasticised
PVCU polyvinyl chloride unplasticised
PVDC polyvinylidene chloride
PVDF polyvinylidene flouride
PVF polyvinylflouride
PVOH polyvinyl alcohol
SAN styrene acrylonitrile (copolymer)
SBR styrene butadiene rubber
SBS styrene-butadiene-styrene (block
copolymer)
SEBS styrene-ethylene-butadiene-styrene
SIS styrene-isoprene-styrene
SMA styrene maleic anhydride
SMC sheet moulding compond
SRP self reinforcing polymer = LCP
TPE thermoplastic elastomer
TPO thermoplastic olefin (rubber)
TPR thermoplatic rubber
TPS toughened polystyrene = HIPS
TPU thermoplastic polyurethane (rubber)
= TPUR
TPUR thermoplastic polyurethane (rubber)
= TPU
TPX* polymethyl pentene copolymer
UF urea formaldehyde
UHMWPE ultra high molecular weight PE
VC vinyl chloride = VCM
VCM vinyl chloride monomer = VC
XLPE cross-linked polyethylene
Glossary 17
Sources of informationwww.internationalcolourauthority.com
www.pantone.com
www.bpf.co.uk
www.colourtone-masterbatch.co.uk/technicalarticles/
Colouring plastics with masterbatch18
Notes
Colouring plastics with masterbatch
Colour Tone Masterbatch Limited, Pant Glas Farm Industrial Estate, Newport Road, Bedwas CF83 8BJ. UK
Telephone: +44 (0) 2920 888910. Fax: +44 (0) 2920 868487
email@colourtone-masterbatch.co.ukwww.colourtone-masterbatch.co.uk
© Colour Tone Masterbatch 2008 Issue 2