food packaging — the role of additives.pdf

8/17/2019 Food packaging — the role of additives.pdf

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Food pa cka ging the role of

additives

A w ide range of addit ives is available for enhancing the per-

form ance and appearance of food packaging as well as

impro ving the processing of the comp ound . Legislation gov-

erning products coming into contact with food and drink is

cont inual ly under review throughout the world.John Murphy

takes a look at plastics additives in food packaging.

The requirements o f packaging for food-

stuffs includi ng drinks) app ly across all

the materia ls used in the compou nd, espe-

cially stabilizers, pigments, processing aids

and lubricants. While it is necessary to

ensure tha t a l l the ingredients in the com -

pou nd are comple te ly safe for use in con-

tac t with food, this may dis trac t a t tent ion

from their poss ible inf luence on the

processabil i ty of the compound.

Especially in the food packaging sector,

plast ics comp oun ds for f i lm, sheet / ther-

m oform ing a nd in je c tion m ould ing a re

expected today to run a t ever-higher

speeds, with no sticking or faults.

Processing aids and antistats are therefore

much to the fore a lso - an d the ir behav-

iour in contact with foodstuffs is critical.

The ingredients used in products coming

into contac t with food and dr ink have

been regula ted for man y years but , with

new materials particularly additives) con-

s tantly be ing introduced, and a lso with a

growing unders tandin g of what ac tua l ly

constitutes a hazard, the legislation is

under continuous revis ion.

Toxic i ty is probably the longest and best-

researched se ctor of plastics additives,

w i th e x te ns ive doc um e nta t ion on both

sides of the Atlantic . For as long as

research has been carr ied out , there has

been an argument as to which is be t te r

to legis late : the inherent conten t o f a

c om po und, or the e xt r a c ta b i l ity of

potentia l ly hazardous substances .

Legis la tors have tended towards control-

l ing the inhe re nt c onte n t of a c om p ound

though, by the same token, glass should

be excluded as a packaging mater ia l ,

s ince i t conta ins lead) . But the point is

tha t the lead cannot be extrac ted, and

the point is now being accepted when

drawing up new legis la t ion.

For many years the effective international

control has been the US Food and Drug

Adminis tra t ion FDA) and most plast ics

and additives are tested to these standards.

In Europe, there is extensive national leg-

is lat ion and one o f the most inf luentia l

bodies has been the G erman Federa l

Health Minis try Bundesgesundheitsamt -

BGA) which is f requently c i ted in mater i-

al specifications.

The European Union legis la t ion goes

back to the 1990 Direc t ive

90/128/EEC

which was originally a positive list of

a u thoriz e d m onom e rs . The Com m iss ion

is now publis hing its first list of additives

Plastics Additives Compo unding February 2

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that will require testing for migration in

food-contact applications in a new

Directive. Th e listed additives will need to

be tested to show that the plastics com-

pounds in w hich they are used comply

wit h EC legislation for materials in con-

tact with food, an d the process of listing

restricted additives will be conti nued by

means of amendments to the 1990

Directive.

An im portan t and positive aspect of the

programm e will be the use of amend -

ments to introduce new concepts which

should m ake future testing m ore effec-

tive, such as food consu mpti on factors,

and m igration modelling and functional

barriers.

It is almost impossible to presen t an

exhaustive list of additives t hat have been

accepted by the various aut horities for use

in contact wi th food. The following are

guidelines:

S t a b i l i z e r s l a n t i o x i d a n t s

Phosphite/phosphonites

are generally

regarded as the most effective stabilizers

during processing, protecting bo th the

polymer and the p rimary antioxidant.

Hydrolyticallystable phosphites are the

mo st freq uently-use d processing stabilizer

in high-p erforma nce additive systems.

For applications in contact wit h food,

FDA and B GA regulations recommen d

liquid antioxidants based on Vita min E.

These have been developed as paten ted

systems and also open up new areas of

application, in polyolefins and

polyurethane foam systems.

Develo pmen t in recent years has cen-

tered on technical improvement of the

product, and easier handling an d disper-

sion. The main technical objectives have

been a m ore durable effect at lower

dosage levels, with good retention of

colour and transparency when required.

Improv emen t of toxicological properties,

for food-con tact and medical applica-

tions has also been a continu ing aim of

developers. For improved handling, pel-

letized and liquid systems have been

introduced, and there is a general trend

towards greater use o f masterbatch. The

most expensive stabilizers are organotin

stabilizers. Lead compounds are the

cheapest.

Am ong recent developments are systems

with better colour fidelity and handling

properties. Typical is Dover's Doverphos

HiPure 4 - a high-purity tris-nonylphenyl

phosphite (TNPP) processing and heat

stabilizer, whic h is claime d to reduce over-

all costs. Wi th 0.1 residual nony l phe-

nol, it is FDA-approved for food-co ntact

applications and is also used in medicals,

colour-critical polyolefins and styrenic

block copolymers. It is effective also in

acrylics, elastomers, nylon, polycarbonate,

polyurethanes, polystyrene, PVC, ABS

and PET.

A solid phosphite antioxidant has been

developed introduced by GE Specialty

Chemicals, in its Ultra nox range.

Designed to meet the dem and for a high

activity stabilizer wit h superior hy drocar-

bon stability and improved handling char-

acteristics, it is based on b utyl ethy l

propane diol chemistry, rather than the

usual pentaerythritol. It has been granted

FDA approval for food contact in certain

applications and is expected to find appli-

cations in polyolefins, styrenics, PVC,

engineering thermoplastics, elastomers

and adhesives.

l as t i c i ze rs

Polymeric plasticizers (usually polyesters,

based on adipic acid) extend the life of

PVC end-products considerably. They

slow down migration, extraction and

9

volatility. Molecular weight has a signifi-

cant influence on performance but other

factors also determ ine characteristics a nd

performance. Typical applications include

coated fabrics, protective clothing, electri-

cal tapes, con veyor belting, food wrap-

ping, lami nated films, adhesive-coated

films, heat-resistant cables, oil-resistant

cables, oil a nd petrol hose, refrigerator

gaskets and roofi ng membranes.

Esters of fatt y acids and m onocarboxylic

acids - can be used as viscosity depres-

sants for PVC pastes and also as second-

ary plasticizers for plasticized PVC com-

pounds. The y are in liquid form. Advice

should be sought on food-contact

approval. Stearic acid esters are used as

plasticizers and processing agents for vari-

ous plastics and also as lubricants for

polystyrene. The y are semi-solid a nd have

general food-co ntact approval.

Sebacates an d adipates - these provide

good lo w tempe rature plasticizers for

PVC, in liquid form , with fairly general

food-c ontact approval. Di -butyl sebacate

is a highl y efficient prim ary plasticizer for

low temperature applications, used in

films and containers for packaging.

Epoxid ized grades (soya bean oil, linseed

oil) - used asstabilizin g plasticizers wit h

properties o f migratio n resistance, in PVC

compounds, alkyd resins and chlorinated

paraffins, and as pigme nt dispersing

agents in plasticized PVC . Alkyl epoxy

stearate plasticizers are used as low viscosi

lastics

Additives Compounding February 2


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dd i t i v e s

i. stabilisers, especially in PV C pastes,

with some grades providing good low

temperature properties. They are in liquid

form. Soya bean versions have widespread

approval for food contact. Advice should

be sought for other types.

Co l o u r a n t s

Colouran ts are necessary materials in

mos t forms of packaging, and th ey are

critical to extraction and toxicity.

Fortunately, this has been known rig ht

from the beginning, an d there are pig-

ments w ith satisfactory performance

that are accepted for food-con tact

applications.

Dyes are transparent and give bright

colours in light. M ost have relatively poo r

light-fastness an d lim ited hea t stability,

but will tend to retain their colour better

than pigment systems. This is because,

wit h all colourants, it is the surface layer

tha t is affected by exterior con dition s such

as light and , wh ile dyes will similarly suf-

fer fading on the surface, thei r transparen-

cy gives a real depth o fcol our unaffected

by surface influences. D yes can also be

subject to migration ofcolour, w hich is

the subject of legislation for critical prod-

ucts, such as food-con tact applications

and toys.

Thermochrom ic and photochromic pig-

men ts are micro-encapsulated liquid crys-

tal systems, giving precise colour-changes

at specific temperatures, or whe n exposed

to light. The y are particularly interesting

for food/pharm aceutic al packaging, giving

an in dicato r of storage or co oking state.

Therm ochromi c pigments change colour

with temperature, and there are com-

pounds and masterbatches for injection,

blow moulding or extrusion. The pig-

ments comply with FDA food contact

regulations a nd can be used for novelty

products and for products requiring warn-

ing indicators, such as baby bottles, ther-

mom eters and kettles. Possible colour

changes are: green t o yellow, mage nta to

blue an d colou red to colourless. Typical

ranges include Hanna/Victor's

Cham eleon organic pigment concentrate

for polyolefins and styrenics, with co lour

changes activated in 10°C bands, from

-25 to +58°C, a nd a range from Sibner

Hegner, which changes from coloured to

colourless at 5-15°C or 65-75°C.

Intelligent heat protection

for food

products is offered by a pigme nt system

developed by Sachtleben Chemie,

Germany. It can be incorporated in plas-

tic films and food packaging, to control

the temperature in heat-sensitive prod-

ucts. Visible light is kept away and heat

may escape unham pered from the pack-

age. The product is said to be of interest

for projects sponsored by the W orld

Health Organization, aimed at prolong-

ing the preservation of foodstuffs in

developing countries, and for disaster

relief operations.

High

colour strength:

Recen t develop-

ment of pigments with very high colour

strength, for use to give opacity in thin-

wall packaging, have taken place with

the needs of food packaging in mind.

For example, BASF's range of azoic yel-

lows (Paliotol) allows bright tints to be

produced, resistant to heat and light and

suitable for food contact. The families of

Paliotol yellows based on isoindoline,

and reds based on perylene, can be used

in polyolefins and also in the more tech-

nical plastics. A new mixed-phase rutile

yellow pigment (introduced by Bayer:

Light fast Yellow 62R) differs from con-

ventional chrom e rutile yellows by high-

er tinting strength, better hidin g power

and gloss promotion, suitable for light-

fast, water-stable and heat-stable pig-

ment ation o f plastics and coatings and

satisfying purity requirements for food-

cont act applications.

A novel blue-shade red azo pigm ent,

Engelto ne 1 115 (Engelhard) is an alterna-

tive to high perform ance organics, com-

plying with FDA lim its for food contact

and comparable in he at stability with

man y high performance bright reds, such

as DPPs (up to 300°C i n ABS) - which it

could replace, wit h up to 50 savings.

P roces s i ng a id s l ub r i c an t s

a n d an t i s t a t s

Milliken's nucleating technology for PP,

Millad, is approved for PP compou nds

for food contact by the US FD A, the

Canadian HPB (Health Protection

Plastics Additives Comp ounding

February 2

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d d i t i v e s

' I n t e l li gen t ' p igm ent s y s tems

P igment d i s pers an t s

Processing a ids:

F l u o r o p o l y m e r s

Nuc lea t i ng agen t s

indica t ing s tora ge o r coo k ing s tate, . . . . .. .. .

D e v e l o p e d b y S a ch d e b e n C h e m l e ; c a n b e i n c o r p o r a t e d i n fo o d p a c ka g in g t o c o n t r o l ~ e

t e m p e r a t u r e o f h e a t- s en s it iv e p r o d u c t s : u n d e r s t u d y b y W o r l d H e a l t h O r g a n i z a t i o n .

L o w m o l e c u la r w e i g h t i o n o m e r s p r o m o t e g o o d p i g m e n t di s p e rs i on a n d c o m e w i t h i n t h e

r e g u l a ti o n s o f m a n y c o u n t r i e s f o r c o l o u r c o n c e n t r a t e s i n fo o d c o n t a c t .

M o s t fl u o r o p o l y m e r p r o c e s s in g a id s c o m p l y w i t h i n d i r e c t fo o d c o n t a c t r e g u l a t io n s a n d

c an be us ed in PP and PE.

M i l li k en 's M i l lad i s w ide l y approv ed f o r PP c omp oun ds f o r f o od c on t ac t app l ic a t ions .

2

P l a st ic s A d d i t iv e s C o m p o u n d i n g February 2


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dd i t i v e s

board) and the German BGA

(Bundesgesundheitsamt).

Most fluoro polym er processing aids,

which are used in film processing to

reduce die build-up and improve output

of film, will comp ly with regulations for

indirect food contact and f ood regulations

for PP and PE.

Dyn ama r PPA from D yne on is a process-

ing additive for blown film that improves

thermoplastic processing witho ut altering

the existing physical properties. The

c o r n

pan y says that it can re duce significantly

die build-up and has good thermal stabili-

ty in h igh tempera ture processing.

Apparent melt viscosity is lowered allow-

ing fabricators to use high viscosity, high

molecular weight in cast and blown films

and blow m ouldin g applications.

Low molecular weight ionomers th at are

used to prom ote good p igmen t dispersion

com e within the regulations of many

countries for colour concentrates in food

con tact applications.

Am ong o ther additives, Colloids has a

range o f masterbatches for high slip, anti-

block and high clarity that are suitable fo r

food contact. G E Silicones' Tospearl fine

particle silicone anti-bl ockin g additive,

improving film clarity and abrasion resist-

ance is also approved for food contact.

Sodium sulphonate (Chem stat PS- 101,

from Chemax Inc) is recommended for

use in polystyrene, where US FDA

approval is required. It is used as a 50%

active masterbatch or a 30% blend of

sodium alkyl sulphonate an d glycol

monostea rate in LD PE carrier.

Pure Eze (from Slide Products) is a white

oil-based release agent th at is suitable fo r

foo d applications.

n f o r m a t i o n s o u r c es

The re is a wealth of information , from

national plastics federations and from the

EU, and a valuable source of information

on this subject is the UK packaging and

prin ting research association Pira.

A comprehensive database on all forms

of chemical legislation in 25 c ountries

has been published as a CD- RO M by the

United Nations Economic Commission

for Europe (UN/ECE). It covers 15 sec-

tors of the industry, including materials

in contact with foodstuffs, and transport

and labelling of dangerous chemicals.

Over 600 text summaries are given, with

full references to the original legislative

acts. The acts themselves are also

'chained' so that amend ments can be

found with the act itself. The database

can be searched by country, keyword,

and reference to act or date, with sum-

maries and titles in the original language,

as well as in English.

Including Directives of the Eu ropean

Com munity , the database is intended to

provide useful inform ation and guidelines

for countries w orldwide that still have lit-

tle or no legislation contr olling chemicals.

It also provides manufacturers, traders,

legislators and lawyers with instan t access

to inform ation that is normally difficult

to obtain.

The CD -RO M costs US 250, and can be

ordered through the usual U N publica-

tions sales agencies, or direct fro m the

UN sales offices in the USA (New York)

or Euro pe (Geneva). •

PlasticsAdditives Compounding February 2

food packaging — the role of additives.pdf

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