Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
1999-12-29
2003-07-15
Kelly, Cynthia H. (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S394000, C252S008620, C442S079000, C442S082000, C442S089000
Reexamination Certificate
active
06592988
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to compositions that exhibit both repellency and antistatic characteristics. This invention further relates to fibers, films, fabrics, coatings, and molded or blown articles comprising the compositions. In other aspects, this invention also relates to a topical treatment composition and to processes for imparting both repellency and antistatic characteristics to substrates.
BACKGROUND OF THE INVENTION
Various fluorochemicals have been used to impart water and oil repellency, as well as soil resistance, to a variety of substrates (for example, textiles, carpet, leather, paper, and non-woven webs). These fluorochemicals have most often been applied topically (for example, by spraying, padding, or finish bath immersion), but some fluorochemicals have also been useful as polymer melt additives for preparing water- and oil-repellent polymeric fibers, films, fabrics, etc. The resulting repellent substrates have found use in numerous applications where water and/or oil repellency (as well as soil resistance) characteristics have been valued.
For some applications, however, antistatic properties have also been necessary or desirable.
Electrostatic charge buildup is responsible for a variety of problems in the processing and use of many industrial products and materials. Electrostatic charging can cause materials to stick together or to repel one another. This is a particular problem in fiber and textile processing. In addition, static charge buildup can cause objects to attract dirt and dust, thereby decreasing the effectiveness of fluorochemical repellents.
Sudden electrostatic discharges from insulating objects can also be a serious problem. With photographic film, such discharges can cause fogging and the appearance of artifacts. When flammable materials are present (for example, in a surgical environment), a static electric discharge can serve as an ignition source, resulting in fires and/or explosions. Static is a particular problem in the electronics industry, since modern electronic devices are extremely susceptible to permanent damage by static electric discharges.
However, conventional antistats (many of which are humectants that rely on the adsorption and conductivity of water for charge dissipation) have generally not been very effective in combination with fluorochemical repellents. The result of such combination has often been a substantial deterioration (or even elimination) of either antistatic or repellency characteristics (or both), relative to the use of either additive alone.
Furthermore, it has been particularly difficult to combine conventional antistats and fluorochemical repellentsin polymer melt processing applications, as, for example, the water associated with humectant antistats vaporizes rapidly at melt processing temperatures. This has resulted in the undesirable formation of bubbles in the polymer and has caused screw slippage in extrusion equipment. Many antistats have also lacked the requisite thermal stability, leading to the production of objectionable odors (for example, in melt blowing applications, where high extrusion temperatures are involved).
Thus, there remains a need in the art for antistatic agents and repellents that can be effectively combined to impart both good antistatic characteristics and good repellency characteristics to substrates and that, in particular, can be utilized as melt additives without causing processing problems or melt defects.
SUMMARY OF THE INVENTION
Briefly, in one aspect, this invention provides a water- and oil-repellent, antistatic composition comprising (a) at least one nonpolymeric ionic salt consisting of (i) at least one monovalent metal cation, divalent metal cation, or organic onium cation (for example, a quaternary ammonium ion) and (ii) at least one weakly coordinating anion, the conjugate acid of the anion having an acidity greater than or equal to that of a hydrocarbon sulfonic acid (for example, a bis(perfluoroalkanesulfonyl)imide ion), and with the proviso that the anion is organic or fluoroorganic when the cation is a metal; (b) at least one fluorochemical repellency-imparting additive or repellent; and (c) at least one insulating material. As used herein, the term “organic onium cation” means a positively charged organic ion having at least part of its charge localized on at least one heteroatom (for example, nitrogen, phosphorus, sulfur, iodine, or oxygen). Preferably, the insulating material is a thermoplastic or thermosetting polymer (more preferably, thermoplastic), and the composition is prepared by forming a blend (more preferably, a melt blend) of the components.
It has been discovered that the above-described class of ionic salt antistatic agents or antistats can be effectively combined with fluorochemical repellents to impart both good antistatic characteristics and good repellency characteristics to a variety of insulating materials. The antistats and repellents can be combined not only in topical treatments (external additives) but even (and preferably) as melt additives (internal additives) without causing processing problems or melt defects. The antistat/repellent combination used in the composition of the invention is surprisingly effective at dissipating the static charge that can accumulate in an otherwise insulating substrate such as a polymer film or fabric, while also imparting durable water and oil repellency (and soil resistance). Even more suprisingly, when used in topical treatments or as polymer melt additives in polypropylene melt-blown nonwoven fabric, certain preferred antistats exhibit synergistic behavior when combined with the repellent(s), in that better static dissipation rates are obtained than when the antistats are used alone.
The combination of ionic salt antistat(s) and fluorochemical repellent(s) used in the composition of the invention is compatible with a variety of polymers. Since many of the antistats are hydrophobic (immiscible with water), the antistatic performance of the combination is often relatively independent of atmospheric humidity levels and durable even under exposure to aqueous environments. In addition, since many of the antistats are stable at temperatures up to 300-500° C., the combination of such antistat(s) with thermally stable fluorochemical repellent(s) is particularly well-suited for use in high temperature polymer melt additive applications and in applications where the use temperatures are very high.
The combination of ionic salt antistat(s) and fluorochemical repellent(s) used in the composition of the invention therefore meets the need in the art for antistatic agents and repellents that can be effectively combined to impart both good antistatic characteristics and good repellency characteristics to substrates and that, in particular, can be utilized as melt additives without causing processing problems or melt defects.
In other aspects, this invention also provides fiber, fabric, film, a coating, and a molded or blown article comprising the composition of the invention; processes for imparting both repellency and antistatic characteristics to a substrate, for example, by bulk addition or by topical treatment; and a topical treatment composition comprising (a) at least one nonpolymeric ionic salt consisting of (i) at least one monovalent metal cation, divalent metal cation, or organic onium cation and (ii) at least one weakly coordinating anion, the conjugate acid of the anion having an acidity greater than or equal to that of a hydrocarbon sulfonic acid, and with the proviso that the anion is organic or fluoroorganic when the cation is a metal, and (b) at least one fluorochemical repellency-imparting additive or repellent.
DETAILED DESCRIPTION OF THE INVENTION
Antistats
Ionic salts suitable for use as antistats in the composition of the invention are those that consist of a monovalent or divalent metal cation (preferably, monovalent) or an organic onium cation (preferably, an organic onium cation) and a weakly coordinating anion. Suitable metal cations include, for example, lithium, ca
Klun Thomas P.
Lamanna William M.
Thompson Delton R.
Fulton Lisa P.
Gray J. M.
Kelly Cynthia H.
Weiss Lucy C.
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