a me chem fibers

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Over the past 20 years, polyester (poly-

ethylene terephthalate) has emerged asa leading polymer for fibers, film andpackaging. Recent publications [1, 2] putthe 2002 production of polyester fiber at20.9 million tons, slightly more than cot-ton during the same period.The contain-er resin production during 2002 wasabout 9 million tons.The combined fore-cast for 2010 is estimated to top 50 mil-lion tons. Some of the applications forpolyester include:• textile products such as apparel, auto-

motive, home furnishings and beddingproducts etc.

• nonwoven products such as filters,medical and protective fabrics• technical fibers such as tire cord,

awnings, tents and sewing threads• packaging applications including bot-

tles for soft drink, water and juice etc.• polyester film - imaging, magnetics

and other industrial specialties.In keeping with the explosion of the useof polyester resin in various applica-tions, Americhem, Inc., is constantly de-veloping new masterbatches for PETthat enhance the properties and valueof the products in which they are incor-porated. Properties that today's fibersand packaging materials demand. Ex-amples of such products include fiberswith anti-microbial properties, fibers thatwithstand the harsh effects of UV so thatarticles made from such fibers lastlonger, fibers that absorb odor or fibersand textiles that offer moisture manage-ment properties and packaging materi-als that offer UV protection and ac-etaldehyde reduction. Here, solutiondyeing techniques for coloring polyesterand the use of the concept for producingvalue added fibers will be described.Recent developments in functional andmulti-attribute masterbatches for fibersas well as masterbatches for packagingare discussed. Americhem has beenserving the synthetic fibers industry withcolor and additive masterbatches for so-lution dyeing (mass dyeing) for the past18 years.

Coloring of polyester fibers

Polyester fibers, because of their struc-ture and well-developed order duringspinning, absorb little dye in convention-al dye systems. Hence traditional poly-ester fibers are predominantly dyed us-

ing disperse dyes.Cationic dyeable poly-

ester fibers, with modified structure offerenhanced dyeability. Solution dyeing (al-so referred to as mass dyeing or spindyeing or dope dyeing) offers a way ofcoloring polyester fibers and is inde-pendent of its chemistry.

- Solution dyeing

Solution dyeing can be defined as aprocess for coloring polyester (and othersynthetic yarns) in which the colorant isadded to the polymer melt, before it isextruded through a spinneret in to indi-vidual fibers. As a result, the colorant ispermanently locked into the fiber and the

fiber is colored throughout. Solution dye-ing offers following advantages:• better color fastness to light (UV),

bleaching agents and ozone• very good migration stability under ad-

verse conditions• tight lot to lot color uniformity• environmentally friendly manufactur-

ing process (energy efficient, sincefiber spinning and coloring is done inthe same step; does not use water -conventional dyeing on the other handuses water extensively; effluent treat-ment may be necessary, since part of

the disperse dye is left behind in thedye bath - only about 85% or so be-comes part of fiber)

• high yields with low scrap• wide range of colors can be produced• customized products can be easily de-

signed for value added fibers.On the limitations inventory, control canbe an issue, since the decision to pro-duce colored yarn is done at the earlyphase of the production process. Devel-opment of small lot capability andspeedy color matching are helpful inovercoming this concern.

- Product design for solution dyeing Proper masterbatch design is an impor-

portant parameters of color masterbatch

design are:• product specification or end applica-

tion in which the product is used• spin performance - the term spin per-

formance relates to factors such asspin breaks, draw warps, yield rates,filter pack life, and deposit build up onspinneret and godets.

Proper colorant selection is the first criti-cal step in masterbatch design. Sincethe masterbatch is added to the polymermelt prior to spinning, the colorant mustwithstand the high processing tempera-ture without color variation.Thermal sta-

bility of the pigment is important for bothcolor control and specification control.Color concentration also has an effect onthe color stability. Depending on the endapplication, weathering and other fast-ness requirements play an importantrole in masterbatch design.The choice of carrier resin also plays animportant role in product performance.This is especially critical when producinglower denier fibers. Incompatibility ofmasterbatch carrier resin with host poly-mer leads to problems such as• bridging problems at the throat of the

extruder and polymer build up in thefeed section

• differences in recrystallization temper-ature can affect bulking conditions inair-jet texturing.

Very good dispersion of colorant in thepolymer matrix and proper melt viscosityof the masterbatch are an absolute ne-cessity, without it, the spin pack is imme-diately blocked or restricted. Poor pig-ment dispersion also results in breakageof fiber, especially in the drawingprocess, which results in draw warpsaround the godets. Americhem has de-veloped a test that correlates laboratoryfiltration analysis with the length of timethat the filter packs will last.

452 CHEMICAL FIBERS INTERNATIONAL Volume 53, December 2003

FIBER PRODUCTION

Color, functional and multi-attribute solutionsfor polyester fibersV.G. Kulkarni, Americhem, Inc., Concord, NC/USA

tant aspect of solu-tion dyeing. Poorlydesigned master-batches can leadto spinning prob-lems. There are anumber of criticalfactors which canaffect spin per-formance of solu-tion dyed polyesterthat can be con-

trolled by means ofproper product de-sign. Two of the im-

Fig. 1 Antimicrobial efficiency of polyester fiber as a function of concen-

tration of antimicrobial masterbatch

Lecture held at the 8th World Congress "The Poly-

ester Chain", Polyester 2003 in Zurich/Switzerland,

December 1-3, 2003



Black polyester yarn has been tradition-ally produced using the solution dyedprocess. The demand for solution dyedcolors is steadily increasing especially inautomotive and specialty fabrics/textileswhere higher performance offered by so-lution dyeing is preferred. One of the key

advantages that solution dyeing offers isthat customized products can be easilydesigned for producing value-addedfibers. For example customized colors(fluorescent, metallics), functional fibersand more importantly multi-attributeproducts can be produced.Lastly, there are many colorants, whichgive the expected color, but only proper-ly designed masterbatches give bothcolor and performance. Communicationin regards to which product values arecritical is very important to assure prop-er product design.

Functional masterbatches

Functional masterbatches deliver func-tional attributes without compromisingthe processing properties. Typical func-tions offered include• antimicrobial• weathering/UV protection• customized optical whitening effects• flame retardants.In addition to these, Americhem is devel-oping several novel masterbatches thatoffer unique functional attributes to fiberssuch as odor adsorption, moisture man-agement and low abrasion/friction prop-erties.

Antimicrobial masterbatches

Antimicrobial masterbatches based onsilver chemistry are designed to standup to high processing temperatures atwhich polyester fibers are produced. Be-ing non-migratory in nature, the concen-trate becomes part of the synthetic fiber,thereby offering protection throughoutthe life of the product. A unique com-pounding process, specifically devel-oped for this application offers excellentdispersion and makes possible higher

loading of the antimicrobial additive inthe polymer matrix.At the recommendeduse rate of 1.5-4% the products offervery good spin performance and highyields. Fibers and articles containingAmerichem's antimicrobial masterbatch-es display very good efficiency againstgram positive (Staphylococcus aureus)and gram negative (Klebsiella pneumo-nia) bacteria as shown in Fig. 1.

Light stabilizer masterbatches

Polyester fibers are increasingly used inexterior applications, such as automotive

fabrics, awnings and flexible signs etc.These applications require that the fiberbe stabilized against degradation by ul-

traviolet light. Light stabilizers, depend-ing on the chemical class (UVA, HALS)either absorb the harmful ultraviolet radi-ation or counteract the photo-degrada-tion of synthetic fibers by UV and oxygenand help retain color and mechanicalproperties. Using a customized ap-

proach and extensive weathering ex-pertise, Americhem has developed mas-terbatches, which stand up to toughweathering requirements. Fig. 2 showsthe transmission spectrum of polyestercontaining UV additive compared withneat polyester. Polyester containing UVadditive shows absorption of light to 380nm, which extends the useful life of thefiber/fabric. Data on tenacity of fiber as afunction of extended UV exposure is be-ing developed.

Flame retardant masterbatches

Flame retardant masterbatches basedon phosphorous chemistry are designedto offer flexibility in producing niche fiberproducts. At the present time, the userate of such masterbatches is ratherhigh (in excess of 10%) and requires ad-ditional handling solutions for large vol-ume runs.

Smart masterbatches

Active research is underway to developnovel masterbatches that can impartunique functional and performance prop-erties to polyester fibers.For example, imagine a polyester fiber

containing activated carbon that absorbsodor and offers moisture management,and can be processed and handled sim-ilar to traditional textile or industrial fiber!Americhem, in co-operation with Traptekis working on developing such a master-batch, based on activated carbon. Acti-

vated carbon, well known for its out-standing adsorptive properties is used ina variety of applications such as treat-ment of drinking water, decolorization ofsugar, pharmaceutical production andautomotive filters.A range of other novel property and per-formance enhancing additive master-batches are being explored atAmerichem research and developmentlaboratories.

Multiattribute masterbatches

Multiattribute masterbatches combine

color and functional properties or offermore than one functionality in a singlemasterbatch, thereby providing a cus-tom product that is easy to handle andhighly effective. The concept can beused to design a wide range of products.Some examples of multi-attribute prod-ucts include• color and UV• color and antimicrobial• delustrant and optical brighteners.Fig. 3 shows the reflectance spectrum ofdelustured polyester fiber containing op-tical brightener compared to a typicaldelustured fiber. Customized optical

CHEMICAL FIBERS INTERNATIONAL 453Volume 53, December 2003

FIBER PRODUCTION

Fig. 2 Transmission spectrum of polyester film containing 0.5% of light stabilizer compared with poly-

ester film containing no additive

Fig. 3 Reflectance curve of polyester fiber showing optical whitening effect



whitening masterbatches impart cool,bluish white appearance to polyesterfibers. Customization in regards tobrightness, tone and use rate can bedone to suit specific needs

Solid color solutions forPET packaging

Polyester bottles and packaging materi-als are colored using masterbatchescomprising various carrier systems rang-ing from liquid to low melting wax to sol-id resin. Americhem color and additivemasterbatches based on polyester carri-er resin with melting point of greater than220 °C offer several advantages overother systems as shown in the table.

Summary

In conclusion, the solution dyeing ap-proach to coloring polyester fibers and

its advantages in terms of performancesuch as weathering, migration as well asa environmentally friendly manufacturingprocesses are described here. Further-more functional, multi-attribute productsare described and novel smart master-batch concepts are introduced. Multiat-

tribute masterbatches offer an effectivemeans to produce value added productswith color and functionality or multifunc-tional fibers.

References

[1] Chemical Fibers International 53 (2003) 216

[2] International Fiber Journal 18 (2003)

454 CHEMICAL FIBERS INTERNATIONAL Volume 53, December 2003

FIBER PRODUCTION

Advantages of solid masterbatches over liquid and wax systems

Advantage Eliminates

decrease plasticizing time by 5-7% injection-molder screw slippage & recovery times

caused by lubrication of liquid and wax carriers

solids color change can be 50% faster longer purge times typically observed

compared to liquid with liquid colors

no lost time from shutting line down to clean residue build-up on screw resulting inmachine lost time

no bridging bridging caused by low melt resins adhering

to PET pellets

no volatiles during recycling recycled reclaim problems caused by volatiles

cleaner to use and easier house keeping general housekeeping problems of l iquids

a me chem fibers

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