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Flexo: Green Chemistry and Sustainability

Jeannette Truncellito

Sun Chemical Corporation

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Presentation Content

Review of Chemistry and Hazards

Comparison of Water-Based, Solvent Based and Energy Curable Inks

Health and Safety Risks

EPA Position

Ink Composition

Sustainable Issues

New technology approach for flexible packaging ink

Biodegradability

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Flexible Packaging Inks: Are They Green and Are they Safe?

As with most printing inks, Flexo and Gravure inks do contain “hazardous”components, but are safe and effective when used properly.

Potential hazards:

– Solvent based inks are flammable and ignitable, however, generally these inks are not reactive.

– Water-based inks, dependent on the % solvent incorporated can also be flammable, they are not ignitable or reactive.

– UV inks can be reactive depending on composition.

– EB inks can be reactive depending on composition

Although significant portions of inks may be composed of bio and naturally occurring components, this may not imply they would be classified as “Green” or non-hazardous!

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Potential Risks vs. Classification of Ink Systems

Flammability Ignitability Reactivity

Solvent- Based

Highly Yes No

Water-Based Low to high No No

UV/EB No No Yes

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Health and Safety Concerns

All ink classes may impose some potential chemical risk

Dermal and inhalation are the main routes of exposure

Solvent and water-based inks risk are generally related to solvents.

UV risk is mainly related to reactivity skin sensitivity.

Press-side additions, common in both water-based and solvent-based inks can pose an additional risk in handling and containment.

Even when formulated to contain bio-derived materials, health and safety risks must be accessed

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EPA’s Structure Activity Study

EPA performed a thorough study comparing 3 different Flexo ink chemistries to determine overall risks and environmental impact.Study included water-based, solvent-based and UV inks, all used for printing wide-web flexo.Study was completed in early 2000’s and did not include EB, which today is also a viable method.For the purpose of this presentation EB is similar in chemical composition to UV, without photoinitiators.

EPA found Water-based inks to have lower potential hazards with lower energy requirements

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Water-Based Inks

As regulated, water-based inks can contain up to 25% solvent to be classified as “water-based”– Typical water-based inks may contain from 1-10% solvents– Additionally, some water-based inks contain hazardous air

pollutants (HAP’s)– Alcohols, amides, nitrogenous compounds and glycols exposure

routes are typically inhalation and dermal.– Energy consumption of water-based inks are considered favorable

in comparison to solvent-based inks which required treatment.– Water-based inks can easily utilize bio-based components

In practice, water-based inks require adaptations in applicationand are generally printed at lower press speeds, but are effective

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Solvent-Based Inks

High concentration of VOC’s compared to water-based inks

Oxidizers are used to destroy emissions outside of the printing facility

Alcohols, esters and some hydrocarbon solvents and glycols represent potential risk to workers.

Bio-based alcohols may be used in favor of petro-based, however, overall impact on sustainability is low.

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UV/EB InksAcetylated polyols used as reactive diluents.Components are active and not volatilePhotoinitiators have the potential for migration issues to occur in the final package.EB technology is applicable to “Wet on Wet” trapping, inks are commercially available. EC inks can be formulated with negligible VOC levels, eliminating the energy used to recapture solvent. Curing process often consumes less energy than the dryers required to evaporate other inks. Energy curable inks do not dry up on press, wash-up is facilitated

UV and EB cured inks offer a number of advantages towards reducing environmental impact at the press.

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Newest Technology for Flexo: Advantages of EB vs. Other Ink Chemistries

EB Wet-On-Wet Advantages:– NO SOLVENTS– NO VOC’S– NO SOLVENT LICENSING or EXPOSURE– NO SOLVENT COSTS– NO INCINERATION– NO INTERSTATION DRYING– NO HEAT… less waste– NO PHOTOINITIATORS– NO/LOW EXTRACTABLES– NO/LOW ODOR– POTENTIAL IN-LINE LAMINATION

*Reproduced from ESI

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EB AdvancementsHigher potential for use in food packaging vs. UV

May offer some cost advantages vs. UV

Applications for a variety of end-use packaging

No VOC’s

Lower energy requirements

Excellent reproduction quality

EB provides a favorable carbon footprint

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Overall Ink Considerations:

Solvent-based inks appear to have the most “suspect” ingredients. – As they are readily captured, the overall risk is low. – Oxidators used on press may contribute to green-house gases and other

potential pollutants. – Energy consumption related to the use of solvent-based inks were rated

high, primarily due to the recovery systems employed.Water-based inks represent lower risks than solvent-based inks. – Water-based inks with high VOC’s may have similar risks to solvent-based

inks. – Water-based inks were found to have lower energy requirements, even

though they require higher air volumes and heat on press to dry.EB will likely be favored vs, UV, both represent low risk

Independent of source and origin, green materialscarry similar risks in a formulated ink products.

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Sustainable Ink Materials

Sustainable opportunities for Flexible packaging inks

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Sustainability Factors for Inks

Various organizations and companies have released sustainability definitions and statements.Dominant themes are:– Source of materials– Energy / conservation– Waste / end-of-life– Economics / performance

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Sustainability Factors for Flexible Packaging Inks

Ink manufacturing– Renewable materials

– Production (emissions, energy, waste)

– Origin and transportation

Performance on sustainable substrates– Printability / appearance

– Functionality

– Barrier coatings applied by printing

End-of-life– Biodegradability of final article

with dry ink film

– Recycling

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Current Status of Flexible Packaging Inks

Current ink systems often contain some bio- based materials and can be combined with petroleum-based materials to deliver the performance demanded for theapplication(s). Use of bio-derived materials should positively impact sustainability from a material perspective.

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ASTM MethodsFrom ASTM D 6852:

Bio-based Material: Organic material in which carbon is derived from a renewable resource via biological processes. Bio-based materials include all plant and animal mass derived from CO2 recently fixed via photosynthesis.

Renewable Resource: Resource that replenishes or can be made to replenish on an essentially predictable time schedule. Old growth forests, rare species and all fauna and flora not regenerated on an essentially predictable time scale are not considered renewable resource. Generally the renewal cycle time is less than human life span (<100 years).

A renewable or bio-based material does not imply it is compostable or biodegradable

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Sustainability Factors for Flexible Packaging Inks

A variety of opportunities to improve sustainability arise during the formulation, manufacture, and use of ink.

Scorecards and statements emphasize the need for many factors to be considered when selecting or developing products with improved sustainability.

Ink and adhesive impact has not yet been addressed by retailers and consumer product groups.

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Ink CompositionMain ink components:

Pigment: The majority of pigments in use today are synthetic materials designed to deliver high strength so that they can be formulated at low levels, due to their impact on costs. – Organic or inorganic solids which provide color– May not be present in transparent coating productResin: Ink resins must interact successfully with the pigments, the solvents, the printing technology they are designed for, and the substrate they will adhere to. Their chemistry may contribute to the drying/crosslinking of the ink film on the substrate. They help give formulated inkthe viscosity for the printing method and provide adhesion, appearance (gloss), and resistance properties to the final film – Wets pigment; provides gloss, adhesion, other propertiesSolvent: Solvents mobilize the solid components. The phase change from a liquid or paste ink to a solid ink film is accomplished by evaporation, curing, or absorption of the solvent into the substrate. A range of solvent systems are encountered in inks, depending on the printing method, including water, oils, toluene, alcohols, acetates, and none at all. – Mobilizes the solid components; cures, evaporates, or penetrates substrateAdditives: A variety of materials including waxes, defoamers and special functional material are available.– For special performance needs

Actual raw materials used vary widely among different printing technologies and substrates

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Polymer Examples of Bio-based Materials in InksModern ink systems often contain some bio-based materials and are combined with petroleum-based materials to deliver performance demanded by current printing technologySome bio-based resources currently used in inks suffer supply/price pressures– Rosin-derived resins

Prices skyrocketingFuture global capacity questionable

– ShellacPrice fluctuations, inconsistent performanceLimited harvesting

– NitrocelluloseGlobal reduction in number of manufacturersHigh costPotential danger in handling and storage

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Examples of BiopolymersPolyesters– Polylactic acid– Polyhydroxyalkanoates

Proteins– Silk– Soy protein– Corn protein (zein)

Polysaccharides– Xanthan– Gellan– Cellulose– Starch– Chitin

Polyphenols– Lignin

– Tannin

– Humic acid

Lipids– Waxes

– Surfactants

Specialty polymers– Shellac

– Natural rubber

– Nylon (from castor oil)

Thames Research Group

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Pigments

Mainly organic; typically constitute 10-18% of inkAlternative manufacturing to reduce loss/waste and lower environmental impact has been successfulStrength and purity of colorants difficult to reproduce using alternative chemistriesNaturally occurring pigments do not afford the color values required

New renewable resource technology will likely impact resins first, pigments later

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Bio-derived Materials in Flexo Inks

Ink technology Film-forming component

Solvent & mobilizing component

Amount renewable resource / VOC’s

Water-based Acrylic emulsion or solution

Water Little or none (but 95% VOC-free)

Solvent-based Cellulose esters, urethanes, polyamides, acrylic

Organic solvents (and corn-based ethanol)

10-15% (50% VOC at application)

Oleoresinous Rosin esters; vegetable oils and alkyds

Petroleum distillates, fatty acid esters

30-40% (higher levels available); VOC varies

Energy curing Acrylate esters or biscycloaliphatic epoxides

Reactive diluents (acrylates, epoxides)

10% possible with fatty acid derivatives (VOC- free)

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Bio-derived Materials in Inks

Renewable Resource Function Application

Vegetable oils (linseed, Tung, soybean)

Oxidative drying Litho publication, sheetfed packaging

Cellulose (nitro-, acetate, propionate)

Modified rosin

Shellac

Proteins

Film-formers (meet required solubility, drying, resistance properties)

Solvent-based flexo; solvent-based screen; litho packaging

Esterified fatty acids Solvents Litho publication and some packaging

Functions of some major renewable resources in inks

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Bio-derived Materials in InksSources of sustainable raw materials:

Cultivated streams (corn, soybean, etc.)– Some receiving increased support due to biofuels

initiatives– Polysaccharides (starches, etc.), proteins, oilsBiomass waste streams– Lignocellulosics, chitin/chitosanBio-based building blocks– PLABiosynthesis– Xanthan, pullulan, bacterial cellulose, PHA

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Bio-derived Materials in Inks

Some already have a history as raw material sources for inks, coatings, and additives

Many experiencing increasing interest as resins for coatings/films

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Bio-derived Materials in Flexo Inks

Sustainable raw materials: renewable and availableContrast:Petroleum-derived raw materials (acrylics, etc): essentially non-renewableTraditional bio-based raw materials (NC, rosin, shellac): manufacture/availability issues driving up price

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Bio-derived materials in Inks

Properties bio-based resins must meet in printing formulations:– Gloss– Adhesion– Viscosity/stability– Pigment wetting– Compatibility– Fast, thorough drying on substrate while easy to clean off press– Durability in final product– Easy to handle– Low Cost– Compatible with many different films and adhesives

Current systems extensively formulated to provide these properties today, some compromises may be realized when incorporating Bio- based materials

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Bio-derived Materials in Inks

Printing inks based on naturally-derived raw materials are available.

For some applications, further research will be required to develop bio-based resins with the needed performance properties.

Development of bio-based pigments will likely lag behind development of bio-based resins.

Percentages of bio-based components will vary by application

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Emerging Solutions

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Emerging Solutions: Barrier Coatings

Considering the potential for compromised ink performance using bio-based/naturally derived materials, enhancements to the performance of these inks are possible by employing barrier coatings.

Functional and barrier coatings based upon chemistries outside the scope of traditional ink components can be used.

Materials are compliantAfford performance attributes to finished productAre generally non-bio accumulatingReadily biodegradability

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Prevents the penetration or loss of gases, light or odors which can cause advanced spoilage of the packaged product. In addition act as effective barriers to prevent migration.

Prevents the penetration or loss of gases, light or odors which can cause advanced spoilage of the packaged product. In addition act as effective barriers to prevent migration.

What are Barrier CoatingsWhat are Barrier Coatings

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Alternative Approach: Barrier Coatings

Barrier coatings: lower permeability of oxygen, aroma, moisture, etc. –extend shelf life of package contents– Current technology: often a barrier substrate or laminate, which includes

an adhesive– Alternative technology: printable coating (flexo, gravure, other coating

process) which can be thinner and facilitate lower waste, easier disposal & recycling

– Potentially, a thin barrier film will have less impact on compostability of degradable packaging

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Alternative Approach: Barrier Coatings

Barrier coatings can offer enhancements to conventional inks and packaging structures

Barrier coatings to reduce number of packaging elements

Barrier coatings can prolong shelf-life

Barrier coatings that replace non-preferred structures and coatings (PVDC etc.)

Barrier coatings can promote compliance

Barrier coatings as “light-weighting” alternatives offer benefit to multi-layer complex structures

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RetortPackaging

FoodPackaging

Dry Foods PerishableFoods

Barrier Coatings: Primary Focus and Application Space for Barrier Coatings: Primary Focus and Application Space for Flexible PackagingFlexible Packaging

Targeted Market Applications

OxygenBarrier

LiquidLaminates

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Commercial 3-Ply Laminate New 2-Ply Laminate

Barrier Coatings: Oxygen Barrier Coatings andBarrier Coatings: Oxygen Barrier Coatings and Sustainable FeaturesSustainable FeaturesLight Weighting Flexible Model

Less complex laminate structureLighter weight packaging (30% reduction)

Improved laminate integrity (post flexing O2 barrier improvement)Improved shelf life

Removal of Metalized layer and one layer of adhesiveImproved recycling

Coatings that enable the next generation of food packaging technology and design while promoting an environmental focus

Polymer FilmAdhesiveMET Polymer FilmAdhesivePolymer Film

Polymer FilmAdhesiveBarrier CoatingPolymer Film

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Coatings designed for in-line application

PVdC or EVOHCoated Films

MET-PolymerFilms

e.g. MET-Polyester or MET-Polypropylene

CoextrudedFilms

e.g. Polyethylene-EVOH-Polyethylene

Al2 O3 / SiOxCoated Films

Oxygen Barrier Coating: Oxygen Barrier Coating: Model ApplicationsModel Applications

Light Weighting

e.g. Clear barriers, mainly PET

e.g. Chlorine elimination

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Barrier Coatings for Bio-Based Substrates

Preliminary research : flexo system lowered oxygen permeability of biodegradable substrates (23°C, 50% RH):– PLA film with no coating: >> 100 cc/m2/day

with coating: 2.7

– Cellulose film with no coating: 30.2 with coating: 0.50

Printing technology can be used to improve properties of renewable substrates.

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Polymers from renewable sources

Coatings with lower environmental impact

Waste reduction

Conservation of energy, less processing

Improved recycling

Solution: Functional Coatings Solution: Functional Coatings

Making products greener

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Biodegradability

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Converters have an interest in understanding the degree to which inks are biodegradable.

For most printed articles intended to be labeled as biodegradable, this environment would probably be industrial or home composting.

Compostable substances must biodegrade at a rate similar to the materials normally found in compost; 90% of the carbon in a blend of polymers must be converted into carbon dioxide in 180 days.– Inks are rarely 100% composed of individual materials that would be considered compostable by this definition.

The biodegradation rate of natural materials such as cellulose can be slowed by derivatization, and some bio-based materials may undergo cross-linking in the final film. – This makes it difficult to assume that these components will meet the qualifying rate of compostability, despite

their natural origin.

– Ink film makes up only a small portion of most printed articles, and may not affect their compostability rate much.

Biodegradability: How important is it?

The standards by which biodegradability is determined rely on identifyingthe environment in which the article would be expected to undergo decompositionby microorganisms.

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Biodegradability

Normally, dry ink film is not expected to significantly affect biodegradation rate of final article, even when ink contains pigments or acrylics– Many current ink resins such as cellulose derivatives and vegetable oils

will biodegrade, but not as quickly as starches/proteins (e.g. cellulose acetate: similar to wood)

Must establish that heavy metal requirements are met and that plant growth is not affected– e.g. blue and green inks may contain Cu

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Biodegradability

In many applications (smaller print area on medium-heavy gauge material), amount of dry ink film will be almost negligible

Certain heavy metals such as Cr, Pb have been eliminated from most ink products

Alternative metal-based pigments available and continue to be developed

D 6400 EN 13432As 20.5 5

Cd 17 0.5

Cr - 50

Cu 750 50

Pb 150 50

Hg 8.5 0.5

Mo - 1

Ni 210 25

Se 50 0.75

Zn 1400 150

Heavy metal limits (concentration in tested product, mg/kg):

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Biodegradability

Consider all aspects of ink formulation such as metals

Continuing research on bio-based resin / pigment materials should increase print loading possible on thinner compostable substrates

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ConclusionsFlexo inks regardless of the chemistry chosen are safe and effective.

– End-use and packaged components are paramount in deciding process and chemistry

Each class of chemistries used in developing flexo inks have positive and negative implications

– Total cost to use models are available

A variety of opportunities to improve sustainability arise during the manufacture and use of ink

Printing inks based on naturally-derived raw materials are available

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Conclusions

Further research will be required to develop and expand use of bio-based resins and pigments

Printing technology can be used to apply barrier coatings to renewable substrates

Dry ink film on a typical package may not have much impact on compostability - should confirm through testing

Barrier coatings can increase product integrity and package performance

We can manage and minimize risks that can positively enhance safety and environmental impact

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Acknowledgements

Dr. Malisa Troutman/ Martin Spatz : Sun Chemical Corp.

ESI: Information and data for EB

EPA: Various studies and information on ink use and effectiveness

Thames: Data on Bio-based alternatives