colouring plastics with · pdf filein simple terms masterbatch manufacture is a two-stage...

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

[email protected]

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.


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.


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


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


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


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/


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

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