Plastic and nonmetallic article shaping or treating: processes – Forming continuous or indefinite length work – Layered – stratified traversely of length – or multiphase...
Reexamination Certificate
1995-08-31
2003-03-25
Sellers, Robert E. L. (Department: 1712)
Plastic and nonmetallic article shaping or treating: processes
Forming continuous or indefinite length work
Layered, stratified traversely of length, or multiphase...
C057S351000, C057S362000, C264S103000, C264S168000, C428S085000, C525S420000
Reexamination Certificate
active
06537475
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to stain-resistant polyamide compositions and fibers and articles of manufacture formed therefrom.
2. Description of the Prior Art
Textile and carpet yarns prepared from polyamide fibers are subject to staining by a variety of foods, drinks and many other compositions with which it comes in accidental contact. The uptake of acid dye stains from, for example, soft drinks, is a particularly vexing problem for polyamide fibers due to the availability therein of acid dye sites such as amine end groups and amide linkages. Several methods have been suggested for enhancing the resistance of polyamide fibers to acid dye stains.
One approach is to apply a so-called “stain blocker” coating to the surfaces of polyamide fibers to prevent access to the acid dye sites therein by the acid dye staining composition. An example of such a method is illustrated by U.S. Pat. No. 5,145,487 which discloses coating the fibers with sulfonated aromatic condensates (SACs). Similar proposals are suggested in U.S. Pat. Nos. 4,680,212 and 4,780,099.
Another approach is to form the fibers from polyamides prepared by copolymerizing monomers, some of which contain sulfonate moieties. Typical of such systems are those disclosed in U.S. Pat. Nos. 3,542,743; 3,846,507; 3,898,200 and 5,108,684.
U.S. Pat. No. 4,374,641 relates to pigment concentrates made using sulfonated polymers as carrier resins including the highly sulfonated polyamides disclosed in U.S. Pat. No. 3,846,507. U.S. Pat. No. 5,236,645 represents an improvement on the invention claimed in U.S. Pat. No. 4,374,641.
Fibers are generally prepared from polyamides by melt-spinning. Sulfonate containing copolymers generally have higher melt viscosities than non-sulfonate containing copolymers for equivalent relative solution viscosities which limits the extent of polymerization which can be achieved in batch autoclave reaction vessels due to the retardation thereby of the rate of polymerization, as well as its hindrance of effective discharge of the polymerized melt from the reactor. In addition, the presence of sulfonates which have surfactant properties promotes excessive foaming during the melt polymerization process resulting in poor agitation of the reaction mixture and non-uniformity of product.
Yarns having different depths of color require different levels of stain protection. Thus, light shaded colors show the presence of stains more than darker colors. It would be advantageous, therefore, to be able to provide different levels of stain resistance to polyamides depending upon the ultimate yarn color without having to provide a separate polyamide feedstock for optimum formulation of each color yarn.
An additional disadvantage associated with sulfonate containing polyamide copolymers is that they are generally more difficult to dry than sulfonate-free polyamides due to the hygroscopic nature of sulfonate groups.
Polyamides that are topically coated to give stain resistance to the fiber, e.g., with SACs, have the disadvantage that the topical coating is removed during use and maintenance. Gradual removal of the coating will also occur during cleaning with water and detergents. Fibers used for carpet applications may be regularly cleaned with alkaline-based cleaning agents. SAC topical coatings are easily removed using these types of cleaning agents. The topical coating will also be gradually removed during normal wear of the fiber in its chosen application. In addition to their removal during use and maintenance, SACs generally have inferior resistance to light, oxides of nitrogen, and bleach, the latter of which is commonly used for the cleaning of industrial textiles and carpets. Also, the base color of SACs is not colorless and thus may change the shade of the color of the yarn.
It is an object of the present invention to provide a novel and highly advantageous approach for imparting stain resistance to fibers formed from polyamides.
SUMMARY OF THE INVENTION
The above and other objects are realized by the present invention, one embodiment of which comprises an acid dye stain-resistant fiber-forming polyamide composition comprising:
a. a fiber-forming polyamide; and
b. a reagent at least a portion of which associates with free acid dye sites in the polyamide, thereby disabling the acid dye sites in fibers formed from the composition from taking up acid dye stains.
Another embodiment of the invention relates to a masterbatch concentrate for addition to a fiber-forming polyamide to form the above-described acid dye stain-resistant fiber-forming polyamide composition, the concentrate comprising a carrier material compatible with the fiber-forming polyamide, preferably a polyamide, combined with an amount of the reagent in excess of that desired in the acid dye stain-resistant fiber-forming polyamide such that addition of the concentrate to the compatible fiber-forming polyamide results in the desired level of stain resistance.
An additional embodiment of the invention concerns stain-resistant fibers formed from the above-described polyamide compositions.
Further embodiments of the invention comprise articles of manufacture prepared with fibers according to the invention such as textiles and carpets.
A final embodiment of the invention relates to a method of forming acid dye stain-resistant fibers comprising forming a polyamide composition according to the present invention into fibers by, for example, melt spinning.
DETAILED DESCRIPTION OF THE INVENTION
The terms below have the following meanings herein, unless otherwise noted:
“Reagent” refers to any chemical compound, composition or material which associates (as that term is defined below) with the free acid dye sites in a fiber-forming polyamide to thereby render them unavailable for association with an acid dye, which reagent is incapable itself of associating with or taking up the acid dye.
“Association” refers to the chemical reaction or bonding between the reagent and the free acid dye sites in the polyamide which results in prevention of “taking up” of the acid dye by the polyamide, i.e., staining. The association may take the form of a chemical reaction or an acid-salt formulation. Additional types of association include hydrogen bonding, dipole-dipole interaction, Van der Waals forces and coordination complexing.
“Acid dye stain” refers to any material or composition which functions as an acid dyestuff by reacting with the free dye sites in polyamides to substantially permanently color or stain the latter.
The term “acid dye sites” refers to those basic sites in polyamides (e.g., amine end groups, amide linkages, etc.) which react or associate with acid dyes, thereby resulting in a stain bonded thereto.
“Disabling” the acid dye sites from taking up acid dye stains refers to the effect of the association between the reagent and the acid dye sites which renders the latter less capable of associating with acid dyes such as, for example, those in soft drinks, tomato-based products, etc., which result in staining.
The present invention is predicated on the discovery that optimum levels of resistance to acid dye stain may be imparted to polyamide fibers by compounding certain reagents with fiber-forming polyamide compositions subsequent to polymerization of the polyamide and prior to the formation of the fibers. The invention thereby enables avoidance of the above-enumerated disadvantages associated with coating the polyamide fibers with stain resistant SACs and with formation of the polyamides by copolymerizing sulfonate containing monomers.
The selection of a suitable non-acid dyeable reagent having at least one functional group capable of associating with the acid dye sites available in fiber-forming polyamides, thereby rendering those dye sites unavailable for association with acid dye stains, enables the formation of stain-resistant fibers having predetermined and optimum levels of stain resistance not obtainable by the methods and systems of the prior art.
Suitable such reagents include those having at least one fu
Dykema Gossett PLLC
Prisma Fibers Inc.
Sellers Robert E. L.
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