Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Patent
1993-05-19
1995-02-21
Kight, III, John
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
528347, 524606, 264 78, 2642108, 264211, C08G 6926
Patent
active
053917030
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to an improved process for making pigmented polyamide yarns involving, as the polymer matrix for a pigment dispersion, random copolymers of hexamethylene diamine, isopththalic acid and terephthalic acid.
BACKGROUND OF THE INVENTION
Nylon yarns and products made therefrom, such as fabrics and carpeting, have long been colored by treatment with acid, cationic, or other types of dyes. Recently, yarn producers have begun incorporating colored pigments into nylon yarns to improve their resistance to degrading and fading in ultraviolet light, to provide improved resistance to chemicals and noxious fumes, and to provide permanent coloration which is not removed by washing. While some pigments can be mixed easily into the nylon without adversely affecting the filament spinning operation, most pigments--and particularly organics--cause some difficulties while being mixed into the nylon or in subsequent melt-spinning and drawing operations. In general, organic pigments cross-link nylon, change its viscosity, increase the rate of crystallization and spherulite formation resulting in increased draw tension, weakened fibers, and more filament breaks.
European Patent Publication No. 0373655 ("Anton et al."), published Jun. 20, 1990, discloses processes for making stain-resistant, pigmented-colored polyamide fibers with acceptable levels of spinning performance. Those processes involve forming a random nylon copolymer made with up to 4.0 weight percent of a cationic dye additive such as 5-sulfoisophthalic acid or its salts, adding a pigment dispersed in a matrix of nylon 6 and a nylon 6,6/6,10/6 multipolymer to the random copolymer, and melt-spinning the pigment/polymer blend.
The pigment dispersions used in making such fibers are typically prepared by first combining the raw pigment with the nylon multipolymer in roughly equal percentages by weight, melting and resolidifying the combination to form pigmented pellets of the multipolymer. These pellets are then remelted or "let-down" in an equal or greater amount of nylon 6, mixed thoroughly to form a uniform dispersion, resolidified, and pelletized. Certain pigments, however, remain very difficult to spin and draw when dispersed in such matrices.
Ways of reducing the impact of such pigments on nylon spinning and drawing performance would permit the use of a wider selection of colored pigments, both organic and inorganic, and would enable fiber producers to offer a complete range of styling colors without encountering serious product deficiencies or operating difficulties.
SUMMARY OF THE INVENTION
In one embodiment the present invention provides an improved process for preparing pigmented drawn polyamide filaments wherein a molten mixture of a polyamide and a pigment dispersed in a polymer matrix is spun into filaments and drawn, the improvement being the use of a polymer matrix which is a random copolymer of hexamethylene diamine, isophthalic acid and terephthalic acid. Such random copolymers will sometimes be referred to herein as 6I/6T polymers or copolymers, 6I referring to the units formed by the reaction of hexamethylene diamine and isophthalic acid, and 6T referring to the units formed by the reaction of the diamine with terephthalic acid.
The pigment dispersions or compositions of this invention are comprised of from about 5-25% by weight of pigment dispersed in a polymeric carrier or matrix of from about 75-95 weight percent of the 6I/6T copolymer. Preferably the molar ratio of the isophthalic units to the terephthalic acid units in the copolymer is from about 60:40 to about 80:20. Most preferably, this ratio is about 70:30. The compositions may also optionally include small quantities of lubricants and surfactants conventionally used as dispersion aids in pigment concentrates.
The use of these pigment compositions results in reduced draw tension necessary to achieve a predetermined degree of draw in the pigmented fiber. Additional benefits include uniform dispersion of the pigment within the polymer matrix and
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E. I. Du Pont de Nemours and Company
Hampton-Hightower P.
Kight III John
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