Coating processes – Immersion or partial immersion – Running lengths
Reexamination Certificate
1999-03-23
2002-04-30
Cole, Elizabeth M (Department: 1271)
Coating processes
Immersion or partial immersion
Running lengths
C442S079000
Reexamination Certificate
active
06379753
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to methods for the modification of textile and other materials, for example by the attachment of hydrophobic moieties, to impart properties thereon such as water repellency and permanent press.
BACKGROUND ART
Most chemical research in the textile field was conducted in the 1950s, 60s, and 70s. This work has been extensively reviewed. For example, see: Smith and Block,
Textiles in Perspective
, Prentice-Hall, Englewood Cliffs, N.J., 1982
; Handbook of Fiber Science and Technology
, Marcel Dekker, New York, N.Y., Vols. I-III, 1984; S. Adanur,
Wellington Sears Handbook of Industrial Textiles
, Technomic Publishing Company, Inc., Lancaster, Pa., 1995; and Philip E. Slade,
Handbook of Fiber Finish Technology
, Marcel Dekker, New York, 1998). A large majority of this published research was never commercialized due to inhibitory costs or the impracticality of integration into textile production processes. There has been less research in this area in recent years. Most current work is centered on optimizing existing technology to reduce costs and comply with recent government regulations.
Methods have been developed in the art for making textile materials water repellent. The terms “water repellent” and “waterproof” are distinguishable as related to textiles. Water repellent fabrics generally have open pores and are permeable to air and water vapor. Waterproofing involves filling the pores in the fabric with a substance impermeable to water, and usually to air as well. For the purpose of everyday clothing, water repellent fabric is preferable because of the comfort afforded by the breathability of the clothing.
Current commercial processes for producing water repellent fabrics are based on laminating processes (C. J. Painter,
Journal of Coated Fabrics
, 26:107-130 (1996)) and polysiloxane coatings (Philip E. Slade,
Handbook of Fiber Science and Technology
, Marcel Dekker, New York, N.Y., Vol. II, 1984, pp. 168-171). The laminating process involves adhering a layer of polymeric material, such as Teflon®, that has been stretched to produce micropores, to a fabric. Though this process produces durable, water repellent films, it suffers from many disadvantages. The application of these laminants requires special equipment and therefore cannot be applied using existing textile processes. Production of the film is costly and garments with this modification are significantly more expensive than their unmodified counterparts. The colors and shades of this clothing can be limited by the coating laminate film color or reflectance. Finally, clothing made from this material tends to be heavier and stiffer than the untreated fabric. This material also can be disadvantageous due to mismatched expansion and shrinkage properties of the laminate. Polysiloxane films suffer from low durability to laundering which tends to swell the fabric and rupture the silicone film.
Methods of imparting hydrophobic character to cotton fabric have been developed including the use of hydrophobic polymer films and the attachment of hydrophobic monomers via physi- or chemisorptive processes. Repellents used based on monomeric hydrocarbon hydrophobes include aluminum and zirconium soaps, waxes and waxlike substances, metal complexes, pyridinium compounds, methylol compounds, and other fiber reactive water repellents.
One of the earliest water repellents was made by non-covalently applying water soluble soap to fiber and precipitating it with an aluminum salt.
J. Text. Res
. 42:691 (1951). However, these coatings dissolve in alkaline detergent solution, therefore washfastness is poor. Zirconium soaps are less soluble in detergent solutions (Molliet,
Waterproofing and Water-Repellency
, Elsevier Publ. Co., Amsterdam, 1963, p. 188); however, due to the non-covalent attachment to the fabric, abrasion resistance and wash fastness are poor. Fabric also has been made water repellent by coating it with a hydrophobic substance, such as paraffin.
Text. Inst. Ind
. 4:255 (1966). Paraffin emulsions for coating fabrics are available, for example, Freepel® (BF Goodrich Textile Chemicals Inc., Charlotte, N.C.). Waxes are not stable to laundering or dry cleaning. Durability is poor due to non-covalent coating of the fabric and breathability is low.
Quilon chrome complexes polymerize to form —Cr—O—Cr— linkages (R. J. Pavlin,
Tappi
, 36:107 (1953)). Simultaneously, the complex forms covalent bonds with the surface of fibers to produce a water repellent semi-durable coating. Quilon solutions require acidic conditions to react thus causing degradation of the fiber through cellulose hydrolysis. Fabric colors are limited by the blue-green coloration imparted by the complex.
Pyridinium-type water repellents have been reviewed by Harding (Harding,
J Text. Res
., 42:691 (1951)). For example, an alkyl quaternary ammonium compound is reacted with cellulose at elevated temperatures to form a durable water-repellent finish on cotton (British Patent No. 466,817). It was later found that the reaction was restricted to the surface of the fibers (Schuglen et al.,
Text. Res. J
., 22:424 (1962)) and the high cure temperature weakened the fabric. Pyridine liberated during the reaction has an unpleasant odor and the fabric had to be scoured after the cure. The toxicological properties of pyridine ended its use in the 1970s when government regulations on such substances increased.
Methylol chemistry has been extensively commercialized in the crosslinking of cellulose for durable press fabrics. N-methylol compounds are prepared by reaction of an amine or amide with formaldehyde. Alkyl-N-methylol compounds can be reacted at elevated temperatures in the presence of an acidic catalyst with the hydroxyl groups of cellulose to impart durable hydrophobic qualities to cotton. British Patent Nos. 463,300 (1937) and 679,811 (1952). The reaction with cellulose is accompanied by formation of non-covalently linked (i.e., non-durable) resinous material, thus decreasing efficiency. In addition, the high temperature and acid catalyst reduces the strength of the fabric. Recently, the commercial use of methylol compounds has been decreasing due to concerns of toxic formaldehyde release from fabrics treated in such a manner.
Long-chain isocyanates have been used to hydrophobically modify cotton. British Patent No. 461,179 (1937); Hamalainen, et al.,
Am. Dyest. Rep
., 43:453 (1954); and British Patent No. 474,403 (1937)). The high toxicity of isocyanates and significant side reactions with water, however, precluded it from commercial use. To circumvent the water sensitivity of isocyanates, alkyl isocyanates were reacted with ethylenimine to yield the less reactive aziridinyl compound which was subsequently reacted with cellulose. German Patent No. 731,667 (1943); and British Patent No. 795,380 (1958). Though the toxicity of the aziridinyl compound was reduced compared to the isocyanate, the procedure still required the handling of toxic isocyanate precursors. Also, the high cure temperature weakened the cellulose and crosslinkers were needed to increase structural stability. Alkyl epoxides have been reacted with cellulose under acidic or basic conditions to produce water repellent cotton. German Patent No. 874,289 (1953). Epoxides are, in general however, not very reactive and require long reaction times at high temperatures and therefore have not been extensively commercialized.
Acylation of cotton with isopropenyl stearate from an acidic solution of benzene and curing was used to produce a hydrophobic coating for cotton. U.S. Pat. No. 4,152,115. The high cure temperature and acid catalyst however weakens the cotton. This method disadvantageously uses carcinogenic and flammable solvents. The practicality of using flammable solvents in fabric finishings is limited. Alkyl vinyl sulfones have been reacted with cellulose in the presence of alkali to form a water repellent finish. U.S. Pat. No. 2,670,265. However, this method has not been commercialized because the alkali is not compatible with cross-linking reactants req
Offord David A.
Soane David S.
Cole Elizabeth M
Larson Jacqueline S.
Nano-Tex, LLC
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