**1. Introduction**

36 Will-be-set-by-IN-TECH

154 Textile Dyeing

Park, J. (1987). Whither autoomation - how much can we afford ?, *Journal of the Society of Dyers*

Park, J. (1991). Laboratory-to-bulk reproducibility, *Journal of the Society of Dyers and Colourists*

Park, J. & Shore, J. (2009). Evolution of right-first-time dyeing production, *Coloration*

Shamey, R. & Hussein, T. (2005). Critical solutions in the dyeing of cotton textile materials,

Smith, B. & Rucker, J. (1987a). Water in textile processing - part i, *American Dyestuff Reporter*

Smith, B. & Rucker, J. (1987b). Water in textile processing - part ii, *American Dyestuff Reporter*

Smith, C. B. (2007). Dyebath monitoring and control: Past, present, and future, *AATCC Review*

Suh, M. W., Günay, M. & Jasper, W. J. (2007). Prediction of surface uniformity in woven fabrics

Summer, H. H. (1976). Random errors in dyeing - the relative importance of dyehouse

Tavanai, H., Denton, M. J. & Tomka, J. G. (1997). The twist-related structure of yarns with few

Wyszechki, G. & Stiles, W. S. (2000). *Color Science: Concepts and Methods, Quantitative Data and*

Yang, Y. & Li, S. (1993). Instrumental measurement of the levelness of textile coloration, *Textile*

Ziv, B., James, P. & David, W. (1979). Control engineering in the dyeing and finishing industry,

through 2-d anisotropy measures, part-i: Definitions and theoretical model, *Journal*

variables in the reproduction of dyeings, *Journal of the Society of Dyers and Colourists*

Park, J. & Shore, J. (2004). *Practical Dyeing*, Bradford, The Society of Dyers and Colourists. Park, J. & Shore, J. (2007). Significance of dye research and development for practical dyers,

Schanda, J. (2007). *Colorimetry: Understanding the CIE system*, Wiley, Newark.

Shivramkrishnan, C. N. (1983). Level dyeing, still a problem, *Colourage* 30(11): 45,53.

*and Colourists* 103: 199.

*Technology* 125: 133–140.

*Textile Progress* 37(1): 1–84.

7: 15.

8: 68–73.

(92): 84.

7(11): 36–41.

*Coloration Technology* 123: 209–216.

*of the Textile Institute* 98(2): 109–116.

*Chemist and Colorist* 25: 75.

filaments, *Journal of the Textile Institute* 88(2): 107–117.

*Formulae*, 2nd edn, John Wiley and Sons, New York, NY. USA.

*Review of Progress in Coloration and Related Topics* 10(1): 55–60.

107(5-6): 193–196.

Polypropylene (PP) fibers belong to the newest generation of large-scale, manufactured chemical fibers, having the fourth largest volume in production after polyesters, polyamides and acrylics [1, 2]. PP is one of the most successful commodity fibers, reaching a world production capacity of four million tons a year. Due to its low density (0.9 gm/cc), high crystallinity, high stiffness and excellent chemical/bacterial resistance, isotactic PP is widely used in many industrial applications such as nonwovens, industrial ropes, packaging materials, furnishing products, etc. PP fiber has potential, high-volume applications in the carpet, textile, apparel and industrial textile markets.

Due to its thermoplastic nature, PP fiber is manufactured using conventional melt spinning. Subsequent multistage drawing imparts tensile strength and enhances mechanical properties required for industrial applications. Synthesis of PP polymer involves stereoregular polymerization of propylene gas using Ziegler-Natta catalysts [3]. Only isotactic polypropylene is useful for fiber applications among the three stereoisomers. Since only a simple monomer, i.e., propylene gas, is involved in the synthesis of PP, this fiber is relatively inexpensive to produce as compared to other high volume textile fibers such as polyesters, acrylics and nylons. The major products of PP fibrous materials are monofilaments, multifilament yarns, staple fibers and yarns, nonwoven textiles (spunbond, meltblown), tapes, split filament, ropes, carpet backing, etc. Crystallinity of isotactic PP is about 70%, and the molecular weight of fiber grade PP is in the range of 80,000 to 300,000 gm/mole. Since the advent of stereo-regular isotactic polypropylene (PP), the fiber has been used in many industrial applications, as well as in carpets and apparel, due to its high degree of crystallinity, good handle, strength and a high enough melting point for normal use. The potential commercial importance of unmodified polypropylene (PP) fiber in the carpet and textile industries has led to research to develop an aqueous dyeing process for the highly-hydrophobic fiber, consistent with the established coloration processes in use for other high-volume fibers (cotton, nylon, polyester and acrylic). Despite substantial research conducted around the globe, a commercially viable and sustainable aqueous dyeing process of PP based on demand-activated manufacturing has not been realized.

PP offers the advantages of exceptionally low price, good strength and aesthetic properties, along with many other desirable characteristics of a textile/carpet fiber, thus creating the

Commercially Adaptable Coloration Processes for Generic Polypropylene Fiber 157

of materials and operational steps. The treated fibers also showed ring dyeing and inferior

Incorporating dye receptive groups in a polymer chain is known as copolymerization, whereas attaching a segment of a dye receptive group as a side chain is termed graft copolymerization [9]. Several disadvantages are associated with the copolymerization of PP:

b. Polar compounds impede the crystallization behavior of PP and also decrease the

c. Copolymerization adversely affects the physical and mechanical properties of the

Graft copolymerization was more technically appealing in the case of PP, but the expensive

Addition of dye receptor additives prior to fiber extrusion has been explored by many

The additive approach can be divided into four major areas of research involving the

Brown et al. [13] reported disperse and acid dyeable olefin fibers. The dyeable olefin fiber was prepared in two ways: (a) formed a blend of alpha-monoolefin polymer and 1-5% by weight of a pyridine type polymer dye receptor which led to disperse dyeable PP fiber; (b) formed a blend of less than 97% by weight of alpha-monoolefin polymer, 0.5-5% by weight of pyridine type polymer dye receptor and 0.5-5% of hydrophilic compound containing ethylene oxide units. The resultant fibers were dyeable by both anionic and disperse dyes. The approach was to dye the uniformly-dispersed additives so that the whole fiber appeared colored. This approach was found much easier and efficient than fiber pretreatments, copolymerization or grafting, and also less harmful to the fiber's physical

a. The availability of a wide range of disperse dyes, eliminating the requirement of

Grafting of dye enhancers to the polyolefin polymer has been reported by Negola et al. [9, 10]. A mixture of amorphous PETG (glycol-modified polyethylene terephthalate) was grafted onto polyolefin. Maleic anhydride was added to increase the cohesion and dispersion of amorphous PETG in polyolefin polymer. A formulation of 50% PP, 48%

c. Vat and azoic dyes could also be used after a slight modification in the process.

physical properties. Reactive modification is thus not a commercially viable option.

a. Copolymerization of PP with polar compounds gives low efficiency.

technology was considered as a barrier to the commercial adaptation [9].

researchers [9]. Three different classes of these additives are:

c. Low molecular weight organic and inorganic compounds

b. Disperse dyeable fiber using mordant disperse dyes c. Acid dyeable fiber using anionic dyes used for wool

d. Basic dyeable fiber using cationic dyes

**2.1.2 Disperse dyeable PP fibers** 

developing new dyes.

The advantages of disperse dyeable PP fibers were:

b. The leveling properties of disperse dyes were excellent.

d. The result was excellent wash fastness due to water insolubility.

a. Disperse dyeable fiber using major disperse, vat and azoic dyes

melting point of the polymer.

**2.1.1 Addition of dye receptors** 

a. Metallic compounds b. Polymeric additives

development of:

properties.

polymer.

impetus for manufacturing from PP fiber a variety of materials such as towels, floor coverings, sportswear and select technical products. Due to its nonpolar and hydrophobic nature, most of the production of PP fiber is colored by means of mass pigmentation. This route of coloration gives excellent fastness properties during end use; however, it restricts the producer in fulfilling the changing fashion demands of the market. An alternative way of coloring PP fiber exists in which the fiber can be made dyeable by means of post modification, creating active sites for dye association or adding hydrophilic comonomers, but this route has adverse effects on the mechanical properties and costs of the fiber. The development of a truly aqueous process for dyeing PP in its generic, unmodified form is of significant importance vis-à-vis the rising demand for this relatively inexpensive fiber. The developed batch exhaust dyeing methods for PP fiber by us were reported earlier [4-6] and the continuous pad steam and pad/dry heat methods are reported in our recent paper [7]. This chapter covers the state of the art in PP dyeing as well as our adopted approach to develop a commercially viable coloration process for unmodified PP fiber in conventional aqueous systems.
