Plastic and nonmetallic article shaping or treating: processes – Forming continuous or indefinite length work – Layered – stratified traversely of length – or multiphase...
Reexamination Certificate
2002-04-30
2004-01-20
Sellers, II, Robert E. (Department: 1712)
Plastic and nonmetallic article shaping or treating: processes
Forming continuous or indefinite length work
Layered, stratified traversely of length, or multiphase...
C008S115560, C057S351000, C057S362000, C252S008610, C264S103000, C264S168000, C525S420000, C525S437000
Reexamination Certificate
active
06680018
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to stain resistant and soil resistant polyamide compositions and fibers formed therefrom, the fibers being particularly useful in the manufacture of textile articles, carpets and floorcoverings.
2. The Prior Art
Articles of manufacture based on polyamide fibers, particularly apparel, textile fabrics such as for upholstered furniture, wallcoverings and carpeting, are subject to staining when brought into accidental contact with a variety of foods, drinks, and other substances, which contain particular colorant species. The uptake of acid dye stains from, for example, soft drinks, is a particularly troublesome occurrence for polyamide fibers due to the availability within said polyamide fibers of acid dye receptor sites such as amine end groups and amide linkages. The problem is of particular significance when the fibers are uncolored, or are colored by the technique known as “solution dyeing”, i.e., where the coloration is imparted by the addition of pigments to the polymer melt prior to spinning. In both these cases, the acid dye receptor sites are not neutralized by acid dyes used in the alternative bath dyeing methods used to color fibers or fiber containing articles of manufacture.
Several approaches have been suggested for enhancing the resistance of polyamide fibers to accidental staining, particularly by acid dyes. One approach is to apply a so-called topical “stainblocker” coating to the surface of the polyamide fibers to prevent access to the acid dye sites therein by the acid dye staining compositions. The main type of topical stainblockers known to those skilled in the art is sulfonated aromatic condensates (SAC). There are a number of patents covering SAC and their use; examples of the method include U.S. Pat. No. 5,145,486 (to Ciba-Geigy), U.S. Pat. No. 4,680,212 (to Monsanto), and U.S. Pat. No. 4,780,099 (to DuPont). Polyamides that are topically coated with SAC have the disadvantage that the said topical coating provides only temporary protection, as it can be rendered ineffective, or removed, during use and maintenance. In the case of carpet fibers so treated, the coating can be worn away by traffic across the carpet, and may be also removed by cleaning. Commercial and institutional carpeting tends to be cleaned regularly with relatively harsh, alkaline-based cleaning agents, and these in particular may easily remove the SAC coating. In addition to actual removal of the protective coating, SAC generally have inferior resistance to light, oxides of nitrogen, and thermal ageing, the last being a particular problem where underfloor heating is involved. Also, the base color of SAC is not colorless, and thus may change the shade of the color imparted to the base fiber.
Another approach for enhancing the resistance of polyamide fibers to acid dye staining 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. No. 3,542,743 (to Monsanto), U.S. Pat. No. 3,846,507 (to Union Carbide), U.S. Pat. No. 3,898,200 (to Allied Chemical Corporation), U.S. Pat. No. 4,391,968 (to Montedison), U.S. Pat. No. 5,108,684 (to DuPont) and U.S. Pat. No. 5,164,261 (to DuPont), and European Patent 517 203 (to BASF). All of these prior art patents teach the initial formation of a sulfonated copolyamide in a polymerization stage where the sulfonate containing co-monomer becomes an integral part of the polyamide to be used as the base polymer for fiber spinning. All of these patents are concerned with modifying the dyeing or stain resistance characteristics of the polyamide.
Fibers are generally prepared from polyamides by melt spinning. Sulfonate-containing polyamides generally have higher melt viscosities than non-sulfonate-containing polyamides for equivalent relative solution viscosities, which limits the extent of polymerization that can be practically achieved in batch autoclave reaction vessels due to retardation thereby of the rate of polymerization, as well as 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. 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 the sulfonate groups.
Yarns having different depths of color require different levels of protection against staining. 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 on the ultimate yarn color without having to provide a separate polyamide feedstock for optimum formulation of each yarn. Attempts have been made to achieve this goal through the use of sulfonated copolyamides containing high levels of sulfonate moieties, which are themselves added to fiber-forming polyamides to provide an overall sulfur content within the range demonstrated in the prior art to be effective in providing stainblocking to the final fibers. For example U.S. Pat. No. 3,846,507 (to Union Carbide Canada) utilises a copolymer of isophthalic acid, hexamethylene diamine and 5-sulfoisophthalic acid with high sulfur content, which is then compounded into fiber-forming polyamide to produce a fiber with stain resisting properties. Similar high sulfur content copolyamides are also claimed in U.S. Pat. No. 5,889,138 (to Solutia Inc.). However, while providing a partial answer at least to the need to provide simpler routes towards polyamide-based fibers with variable stainblocker levels, the above methods still utilise sulfonated copolyamides, with all the aforementioned disadvantages of such species. In a similar vein to the above two references, PCT Application 96/17982 (to Monsanto) again suggests the use of highly sulfonated copolymers as additives for stainblocking polyamides, but in this case uses non-polyamide copolymers. In this case the problems of manufacture of the said copolymers will be the same as those encountered with sulfonated copolyamides, along with the same high hygroscopicity; however, in addition to these problems, such an approach will also introduce the problems of compatibility between different classes of polymer, which are well known to those skilled in the art.
In addition to the problems of staining of polyamide fibers, soiling of polyamide fibers is also an issue. Fibers used in textile, carpet and flooring applications are most preferably low in soil pick-up, i.e. the fiber does not attract soil, and secondly the fiber should be easy to clean once it is soiled. Soil proofing of polyamides typically involves one of two approaches. Firstly, a coating may be placed on the fiber which is “sacrificial” in nature, i.e. it is designed to pick up soil, but then must be removed in a cleaning process. Starch is a well known and long established example of this method. Such an approach has the drawback that the fiber needs to be recoated after each cleaning to maintain its soil resistance. The second approach to soil proofing is the use of a different type of coating to change the surface energy or hydrophilic/hydrophobic balance of the polyamide, thus making it less attractive to soil. Fluorinated compounds are the most favoured species in this area, applied as a topical coating to the fiber. The fluorochemical compounds are coated onto the fiber to prevent or reduce the wetting of the surface by minimising the contact between the fiber surface and substances that can soil the fiber, making the substance easier to remove. Examples of patents in this area include U.S. Pat. Nos. 3,816,167, 3,896,035, RE 30 337 and 4,043,964 (all assigned to 3M). The use of topical soilproofing coatings suffers from similar disadvantages
Dykema Gossett PLLC
Prisma Fibers Inc.
Sellers II Robert E.
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