Apparel – General structure – Linings
Reexamination Certificate
2000-08-04
2002-02-19
Dawson, Robert (Department: 1712)
Apparel
General structure
Linings
C441S088000, C441S102000, C441S106000, C441S120000, C428S313500, C428S319300, C428S315500, C428S332000, C428S402210, C428S405000, C428S447000, C524S404000, C524S413000, C524S425000, C524S437000, C524S442000, C524S588000, C523S218000, C523S223000, C525S100000, C528S010000
Reexamination Certificate
active
06347411
ABSTRACT:
FIELD OF INVENTION
This invention relates to a composition comprising a homogeneous continuous phase of polydimethylsiloxane viscous liquid, and a discontinuous phase of microballoons; the invention also relates to a buoyant putty of such composition in which sinkable objects can be wrapped or embedded to keep them afloat, for example if accidentally dropped overboard from a boat, and for other applications.
BACKGROUND ART
Through being denser than the medium in which they have been immersed, many objects that would otherwise endure at least a brief wetting, are often irretrievably lost upon accidental release into deep, clouded or cluttered water, through sinking. Such accidental release may occur during the course of recreational or commercial activities; from a ship, boat, dock, shore, or the body of a wader or swimmer; into a pond, pool, canal, swamp, river, lake or ocean; objects commonly lost in such fashion include glasses, pens, watches, combs, coins, cards, keys, tools, instruments, utensils, jewelry, as well as rods, lures, hooks and other fishing accessories, that contain substantial quantities of metal, glass, ceramic, stone, bone, or most kinds of fibers, rubbers, resins or plastics, or even certain woods such as ebony.
Such losses are always annoying and often costly. It is often not practical, convenient or comfortable to keep such sinkable objects held or tied to a person, boat or shore at all times, nor to permanently incorporate low-density parts or materials into their design for the sole purpose of keeping them afloat in the event of accidental release. Certain buoys or other flotation devices exist of a shape or with accessories that allow them to be temporarily tied or fitted to particular types of sinkable objects during the use of these near water, to be later detached for easier transport or storage. One example of these is the “Aqua Float Rod Floater”, from Marine Manufacturing Industries (M.M.I.) Inc., Île des Soeurs (Montreal), PQ Canada, a “tubular split foam device that fits around a fishing rod between the handle and the first eyelet” (Marine Manufacturing Industries Inc., “Aqua Float: The Fisherman's Friend” (pamphlet), Montreal, PQ, Canada, 1995). Such devices, whether made of wood, plastic or other solid materials, that often contain either one or a few large enclosed spaces, or many small closed cells, that are filled with air or inert gas to reduce overall density, are often of size or shape unsuitable for use with other than a limited variety of sinkable objects. Even pieces of soft closed cellular foams, composed of elastic flexible material that imprisons numerous air bubbles in a permanent arrangement, for example some types of foam rubber or polyurethane, that can be wrapped around sinkable objects of various shapes, will tend to revert to non-wrapping shapes in an elastic manner unless restrained by ties, adhesives or envelopes. Also, though either rigid or soft foams can be cut to accommodate smaller sinkable objects, they cannot thereafter easily be re-joined for use with larger ones.
A better way to protect sinkable objects would use a material that is a putty of lowest possible density that can be inelastically deformed to a new stable shape that surrounds or otherwise holds a sinkable object without need for ties, adhesives or envelopes. only a sufficient quantity of buoyant putty to float a smaller sinkable object need be detached from a larger mass; or, several such small quantities could be joined to be able to float a larger sinkable object, or to be stored or transported as a larger mass.
The lowest density that can be achieved with a homogeneous organic material that can be inelastically deformed, for example, unvulcanized rubber, oligoisobutylene or similar flowable hydrocarbon, is about 0.910 g/mL. Since this density is not much less than that of water, fresh water having a density of 1 g/mL, relatively large quantities of such material would be necessary to float most sinkable objects. To enable the greater buoyancy that would be necessary for practical applications, substantial quantities of air or other gas would therefore need to be incorporated, for the lowest possible overall density. However, a material that would be capable of inelastic deformation through flow would not be able to retain loose air bubbles, each of which would eventually break and release its air on contact with the outside surface, or merge on contact with other bubbles to form larger and still unstable voids, thus causing phase-separation within the mass, and even breaking it up to release a held sinkable object. Also, a flowable material that is homogeneous, even if buoyant, would continue to flow under even very mild forces, and thus would not be able to sufficiently retain a shape that could hold a sinkable object in the manner of a putty.
Surrounding each of many tiny air bubbles in its own membrane as a microballoon (also called hollow microsphere, and so distinct from solid or porous microspheres) would allow them all to be retained, evenly dispersed, within the mass of a highly viscous fluid, yet allow them to slide past each other as a portion of the material is inelastically deformed to a new shape. Such a material would now be highly buoyant; moreover, it would have the desirable consistency and flow properties of a putty, by analogy with other heterogeneous composite mixtures that are putties.
A putty is generally formulated as a simple composite material that usually consists of a collection of discrete particles, such as powdered calcium carbonate, as the discontinuous phase, suspended in a viscous liquid, such as oil, as the continuous phase. A certain minimum force is required to overcome the static friction between the particles; below this critical force the material tends to retain the shape given it. This mechanical property has allowed “putties” or “caulks” to be used for centuries to seal small cracks in boats or housing, by forming a plug within a hole that, in contrast with flowable homogeneous materials, does not continue to flow out under gravity or water pressure. In general, the volume of viscous liquid in a putty must be sufficient to fill the voids between the particles, but not so much as to allow the particles to settle and the liquid to exude for the whole material to phase-separate. In the case of approximately spherical particles, the volume-to-volume ratio of continuous to discontinuous phases would thus be a function of geometry, that is independent of the average size of the particles, though a larger distribution of particle sizes makes for relatively less void space available to be filled by liquid. The same volume-to-volume ratio for a putty would be more or less independent of the chemical compositions of the two phases, though their weight-to-weight ratio would depend on their relative densities. A classic composition uses ca. 15% w/w (which corresponds to 34% v/v) of water-insoluble vegetable oil as continuous phase, with inorganic whiting (powdered calcium carbonate) as discontinuous phase (“Putty”,
Encyclopedia Britannica
William Benton Publisher, Chicago Ill. USA y1966 v18 p888); other compositions substitute Fuller's earth (clay) for the discontinuous phase. More modern compositions use low-molecular-weight polysulphides, silicones, or oligomeric hydrocarbons as the “oil” or “continuous” phase, and a wide variety of materials as “filler” or “discontinuous phase” (“Sealants”
Kirk-Othmer Encyclopedia of Chemical Technology
Wiley, New York N.Y. USA y1978 v20 p549-558). Sometimes also the continuous phase consists of or includes monomer that can be cured to a rigid matrix after the desired shape has been formed.
The required qualities for a composition of matter that would be a buoyant putty to hold sinkable objects would be: lowest possible density for maximum buoyancy; malleability towards deliberate shaping by hand without the mass breaking or crumbling, yet sufficient stiffness that it does lose hold of a sinkable object through flow due to gravity or normal manipulation of the object;
Dawson Robert
Marine Manufacturing Industries Inc.
Renault Ogilvy
Robertson Jeffrey B.
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