Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Treating polymer containing material or treating a solid...
Reexamination Certificate
2000-07-10
2001-07-31
Hampton-Hightower, P. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Treating polymer containing material or treating a solid...
C528S483000, C528S486000, C528S491000, C528S492000, C428S395000, C428S396000
Reexamination Certificate
active
06268468
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to making stain- or dye-resistant polyamide carpet fibers by reducing the amino end group content of the polyamide. The present invention also relates to reducing the rate of monomer regeneration during extrusion of the polyamide by reducing the amount of end groups in the polyamide.
BACKGROUND OF THE INVENTION
As used herein, the term “fiber” includes fibers of extreme or indefinite length (i.e., filaments) and fibers of short length (i.e., staple fibers). The term “yarn” as used herein means a continuous strand of fibers.
The terms “stain” and “staining” as used herein with reference to polyamide fibers mean discoloration of such fibers caused by a chemical or physical attraction thereof with a substance such as, for example, food red. The terms “stain-resistant” and “stain resistance” as used herein with respect to polyamide fibers or carpets refers to the ability of the fiber or carpet to resist staining.
As used herein, “unmodified polyamide” refers to a typical commercially available polyamide with an AEG above 20 meq/kg that is known in the art such as, for example, nylon 6 or nylon 6,6.
Polyamide fibers are relatively inexpensive and offer a desirable combination of qualities such as durability, comfort, and ease of manufacture into a broad range of colors, patterns, and textures. As a result, polyamide fibers are widely used in the home and industry as carpets, drapery material, upholstery, and clothing. Carpets made from polyamide fibers are a popular floor covering for residential and commercial applications.
Polyamide fibers dye easily with acid dyes. Consequently, carpets made from polyamide fibers stain easily when exposed to natural or artificial acid dyes that exist in some foods, drinks, medicines, and other consumer products. The resulting stains cannot be easily removed under ordinary cleaning conditions. The severe staining of carpeting is a major problem for consumers. In fact, surveys show that more carpets are replaced because of staining than because of wear. Accordingly, it is desirable to provide polyamide fibers that resist common household stains, thereby increasing the life of the carpet.
One way of avoiding such staining is to topically apply to the surface of the polyamide filaments materials that function as stain blockers so as to prevent acid stains from permanently coloring the yarn. Topical treatments may be sulfonated materials that act as “colorless dyes” and bind the amine dye sites on the polyamide polymer. Sulfonated products for topical application to polyamide substrates are described in, for example, U.S. Pat. No. 4,963,409 to Liss et al., U.S. Pat. No. 5,223,340 to Moss, III et al., U.S. Pat. No. 5,316,850 to Sargent et al., and U.S. Pat. No. 5,436,049 to Hu. Topical treatments, however, tend to be costly and non-permanent (wash away with one or more shampoos).
Another way to make stain- or dye-resistant polyamide carpet fibers is to reduce the number of amino end groups in the polyamide yarn. Methods have been developed to reduce the amino end group content of polyamide fibers by adding amino end group blockers such as caprolactone and butyrolactone to the extruder during polymer extrusion. Blocking the end groups during polymer production greatly reduces the rate of polymerization, and the obtainable amino end group level would still be too high to provide meaningful stain resistance.
There remains a need for stain- or dye-resistant polyamide carpet fibers that overcome the above-discussed limitations, as well as a simpler and more economical process for producing the same.
Moreover, during extrusion, polyamides regenerate the starting monomers via the end groups in the melt. The regenerated monomers are deposited on the extruder die, which causes fuming and other processing problems. The regenerated monomers also show up in the finished products.
A need exists, therefore, for a method of reducing the rate of regeneration of starting monomers from polyamides during extrusion.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide stain- or dye-resistant polyamide carpet fibers.
It is also an object of the present invention to produce a polyamide polymer that significantly slows down the rate of monomer regeneration during extrusion or remelting.
It has now been found that these objects may be achieved by reducing the number of end groups of solid state polyamide with an acid, anhydride, or amine gas.
The above and other objects, effects, features, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments thereof.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
To promote an understanding of the principles of the present invention, descriptions of specific embodiments of the invention follow, and specific language is used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is intended by the use of this specific language and that alterations, modifications, equivalents, and further applications of the principles of the invention discussed are contemplated as would normally occur to one of ordinary skill in the art to which the invention pertains.
According to the present invention there is provided a method of processing solid-state polyamide comprising treating said polyamide with gas-phase acid, anhydride, or amine.
According to the present invention there is also provided a method of reducing the amino end group content of polyamide comprising treating said polyamide with gas-phase acid or anhydride. The polyamide treated in accordance with the present invention is particularly advantageous for solution-dyed fibers, greatly reducing the staining propensity of such carpets.
To reduce the number of amino end groups, solid state polyamide may be treated with an inert carrier gas such as nitrogen or argon containing acid or anhydride at temperatures above the boiling point of the acid or anhydride. The polyamide reacts in the solid state with the acid or anhydride in the gas phase at temperatures elevated above room temperature to reduce the number of amino end groups in the polyamide. Suitable acids include acetic acid, formic acid, and propionic acid. Acetic acid and formic acid are the preferred acids. Suitable anhydrides include acetic anhydride, maleic anhydride, and propionic anhydride. Acetic anhydride is the preferred anhydride.
Further according to the present invention there is provided a method of reducing the carboxylic end group content of polyamide comprising treating said polyamide with gas-phase amine. Reducing the carboxylic end group content reduces both the rate of monomer regeneration during extrusion and the amount of regenerated monomers in the finished products.
To reduce the number of carboxylic end groups, solid state polyamide may be treated with amines that are in the gas phase. More particularly, the polyamide is treated with a gas phase amine at temperatures above its boiling point such that the amine reacts with the polyamide to reduce the number of carboxylic end groups in the polyamide. Suitable amines include ammonia; methyl amine; dimethyl amine; ethyl amine; propylamine; 2-propylamine; butylamine; sec-butylamine; tert-butylamine butylamine; pentylamine; 2-pentylamine; 3-pentylamine; hexylamine; 2-hexylamine; 3-hexylamine, heptylamine; 2-heptylamine; 3-heptylamine; 4-heptylamine; octylamine; 2-octylamine; 3-octylamine; cyclopropylamine; cyclobutylamine; cyclohexylamine; cycloheptylamine; cyclooctylamine; 1,1,3,3-tetramethylbutylamine; diethylamine; diproylamine; dibytylamine; di-sec-butylamine; dipetylamine; N-ethylmethylamine; N-ethylpropylamine; N-ethylpropylamine; 1,2-diaminopropane; 1,3-diaminopropane; 1,2-diaminobutane; 1,3-diaminobutane; and 1,4-diaminobutane. Preferred amines are ammonia, methyl amine, and dimethyl amine.
Polyamides suitable for use in the invention are those that are generically known by the term “nylon” and that are long chain synthetic polymers containing amide (—CO—N
Brank Scott R.
Hu Harry Y.
Ilg Otto M.
BASF Corporation
Hampton-Hightower P.
Nixon & Vanderhye P.C.
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