Coating apparatus – Control means responsive to a randomly occurring sensed...
Reexamination Certificate
1999-09-27
2001-11-06
Edwards, Laura (Department: 1734)
Coating apparatus
Control means responsive to a randomly occurring sensed...
C118S664000, C118S665000, C118S683000, C118S688000, C118S712000, C118S033000, C118S067000, C118S068000, C118S123000, C118S304000, C118S643000
Reexamination Certificate
active
06312523
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods of and apparatus for the introduction of sufficient energy to controllably and selectively place a polymer composition into a porous web. The present invention more particularly relates to methods of and apparatus for the controlled placement of a curable, shear thinning, polymer composition into a web. The controlled placement is preferably performed through the energy controlled viscosity and rheology modified placement of the polymer controlled manner by 1) applying the polymer composition onto a surface of a web, 2) shear thinning the composition and placing it into the web, and 3) curing the polymer composition. This method and apparatus produces a web that either has some of its fibers or structural elements encapsulated by the polymer composition while at least some of the interstitial spaces of the web are open; or has an internal layer extending through the web in a direction generally spaced from at least one major surface thereof; or has both encapsulated structural elements and an internal layer of polymer composition.
2. Description of Related Art
In the prior art, it has been proposed to treat porous webs, especially fabrics, with silicone resins and also with fluorochemicals. Conventional treatments of webs fall into the general categories of (i) surface coatings and (ii) saturations or impregnations.
For example, U.S. Pat. Nos. 3,436,366; 3,639,155; 4,472,470; 4,500,584; and 4,666,765 disclose silicone coated fabrics. Silicone coatings are known to exhibit relative inertness to extreme temperatures of both heat and cold and to be relatively resistant to ozone and ultraviolet light. Also, a silicone coating can selectively exhibit strength enhancement, flame retardancy and/or resistance to soiling. Fluorochemical treatment of webs is known to impart properties, such as soil resistance, grease resistance, and the like.
Prior art fluorochemical and silicone fabric treatment evidently can protect only that side of the fabric upon which they are disposed. Such treatments significantly alter the hand, or tactile feel, of the treated side. Prior silicone fabric coatings typically degrade the tactile finish, or hand, of the fabric and give the coated fabric side a rubberized finish which is not appealing for many fabric uses, particularly garments.
U.S. Pat. No. 4,454,191 describes a waterproof and moisture-conducting fabric coated with a hydrophilic polymer. The polymer is a compressed foam of an acrylic resin modified with polyvinyl chloride or polyurethane and serves as a sort of “sponge”, soaking up excess moisture vapor. Other microporous polymeric coatings have been used in prior art attempts to make a garment breathable, yet waterproof.
Various polyorganosiloxane compositions are taught in the prior art that can be used for making coatings that impart water-repellency to fabrics. Typical of such teachings is the process described in U.S. Pat. No. 4,370,365 which describes a water repellent agent comprising, in addition to an organohydrogenpolysiloxane, either one or a combination of linear organopolysiloxanes containing alkene groups, and a resinous organopolysiloxane containing tetrafunctional and monofunctional siloxane units. The resultant mixture is catalyzed for curing and dispersed into an aqueous emulsion. The fabric is dipped in the emulsion and heated. The resultant product is said to have a good “hand” and to possess waterproofness.
This type of treatment for rendering fabrics water repellent without affecting their “feel” is common and well known in the art. However, it has not been shown that polyorganosiloxanes have been coated on fabrics in such a way that both high levels of resistance to water by the fibers/filaments and high levels of permeability to water vapor are achieved. As used herein, the term “high levels of permeability to water vapor” has reference to a value of at least about 500 gms/m
2
/day, as measured by ASTM E96-80B. Also, as used herein, the term “high level of waterproofness” is defined by selective testing methodologies discussed later in this specification. These methodologies particularly deal with water resistance of fabrics and their component fibers.
Porous webs have been further shown to be surface coated in, for example, U.S. Pat. Nos. 4,478,895; 4,112,179; 4,297,265; 2,893,962; 4,504,549; 3,360,394; 4,293,611; 4,472,470; and 4,666,765. These surface coatings impart various characteristics to the surface of a web, but do not substantially impregnate the web fibers. Such coatings remain on the surface and do not provide a film over the individual internal fibers and/or yarn bundles of the web. In addition, such coatings on the web surface tend to wash away quickly.
U.S. Pat. No. 4,619,864 describes a coating designed to lower the air permeability of the treated web by filling the voids of the web. U.S. Pat. No. 5,322,729 teaches coating a fabric and blowing holes through the coating resin to increase the air permeability.
Prior art treatments of webs by saturation or impregnation also suffer from limitations. Saturation, such as accomplished by padbath immersion, or the like, is capable of producing variable concentrations of a given saturant chemical.
To treat a flexible web, by heavy saturation or impregnation with a polymer material, such as a silicone resin, the prior art has suggested immersion of the flexible web, or fabric, in a padbath, or the like, using a low viscosity liquid silicone resin so that the low viscosity liquid can flow readily into, and be adsorbed or absorbed therewithin. The silicone resin treated product is typically a rubberized web, or fabric, that is very heavily impregnated with silicone. Such a treated web is substantially devoid of its original tactile and visual properties, and instead has the characteristic rubbery properties of a cured silicone polymer.
U.S. Pat. No. 2,673,823 teaches impregnating a polymer into the interstices of a fabric and thus fully filling the interstices. This patent provides no control of the saturation of the fabric. It teaches full saturation of the interstices of the fabric. U.S. Pat. Nos. 4,894,105; 4,919,739; and 5,128,198 teach an immersion of the web into a bath of suspended thermoplastic polymer. Such a treatment provides no control over the placement of the polymer and is capable of producing variable concentrations of a given saturant chemical.
The prior art application of liquid or paste compositions to textiles for purposes of saturation and/or impregnation is typically accomplished by an immersion process. Particularly for flexible webs, including fabric, an immersion application of a liquid or paste composition to the web is achieved, for example, by the so-called padding process wherein a fabric material is passed first through a bath and subsequently through squeeze rollers in the process sometimes called single-dip, single-nip padding. Alternatively, for example, the fabric can be passed between squeeze rollers, the bottom one of which carries the liquid or paste composition in a process sometimes called double-dip or double-nip padding.
Prior art treatment of webs that force a composition into the spaces of the web while maintaining some breathability have relied on using low viscosity compositions or solvents to aid in the flow of the composition. U.S. Pat. No. 3,594,213 describes a process for impregnating or coating fabrics with liquified compositions to create a breathable fabric. U.S. Pat. No. 4,287,261 describes a process for impregnating or coating fabrics with liquified compositions using a siloxane composition having a viscosity in the range of 20,000 to 40,000 centipoise at 25° C. These patents impart no energy into the composition to liquify it while forcing it into the spaces of the web. The composition is substantially liquified before placement onto and into the web. U.S. Pat. No. 4,588,614 teaches a method for incorporating an active agent into a porous substrate. This patent utilizes a solvent to aid in the incorporation of the active
Caldwell James Michael
Schmermund George
Edwards Laura
Lyon & Lyon LLP
Nextec Applications Inc.
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