Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
1997-10-02
2003-12-16
Nakarani, D. S. (Department: 1773)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C528S022000, C528S037000
Reexamination Certificate
active
06664359
ABSTRACT:
TECHNICAL FIELD
This invention relates to polydiorganosiloxane polyurea segmented copolymers and a process for making the same.
BACKGROUND OF THE INVENTION
Pressure-sensitive adhesive tapes have been used for more than half a century for a variety of marking, holding, protecting, sealing and masking purposes. Pressure-sensitive adhesive tapes comprise a backing, or substrate, and a pressure-sensitive adhesive. Pressure-sensitive adhesives are materials which adhere with no more than applied finger pressure and are aggressively and permanently tacky. Pressure-sensitive adhesives require no activation, exert a strong holding force and tend to be removable from a smooth surface without leaving a residue. In some applications, interesting pressure-sensitive adhesives are silicone based adhesives.
Traditionally, polydiorganosiloxane pressure-sensitive adhesives have been made in solution. Conventional solvent based polydiorganosiloxane pressure-sensitive adhesives are generally blends of high molecular weight silanol functional polydiorganosiloxanes, i.e., polydiorganosiloxane gums, and copolymeric silanol functional silicate resin, i.e., MQ resins, which comprise R
3
SiO
1/2
units and SiO
4/2
units. In order to obtain the desired adhesive properties, it has been necessary to react the copolymeric silicate resin with the polydiorganosiloxane. Improvements in such pressure-sensitive adhesive properties are achieved when the copolymeric polydiorganosiloxane resin and polydiorganosiloxane are intercondensed, providing intra- and inter-condensation within the adhesive. This condensation step requires 1) the addition of a catalyst, 2) reacting the copolymeric polydiorganosiloxane resin and polydiorganosiloxane in solution, and 3) allowing the reaction to take place over a period of time at elevated temperature
Solutions of intercondensed polydiorganosiloxane pressure-sensitive adhesives, are generally applied to a backing, heated to remove solvent, and crosslinked, if necessary, to improve physical properties. If crosslinking is needed, peroxide catalysts are conmnonly used. Disadvantages of solution applied polydiorganosiloxane pressure-sensitive adhesives include the need for elaborate drying ovens to remove solvent, and if crosslinking is required, ovens which operate at temperatures greater than 140° C. are needed to initiate diaryl peroxide crosslinking catalysts. Such high oven temperatures limit the substrates useful in making pressure-sensitive adhesive tapes to those which can withstand the elevated temperatures.
In the medical field, pressure-sensitive adhesive tapes are used for many different applications in the hospital and health areas, but basically they perform one of two functions. They are used to restrict movement, such as in various strapping applications, or they are used to hold something in place, such as a wound dressing. It is important in each function that the pressure-sensitive adhesive tape be compliant with and non-irritating to the skin and adhere well to the skin without causing skin damage on removal.
In recent years, pressure-sensitive adhesives have been used in transdermal patch aplications as drug transport membranes or to attach drug transport membranes to skin. Although there is continued development of new drugs and the need for different transport rates of existing drugs, pressure-sensitive adhesives are still needed that can transport such drugs at various rates. Furthermore, there is a continuing need to adhere new drug transport membrances to skin during a treatment period.
In the automotive industry, there are applications that remain unaddressed by current tape products. One such application relates to automative paints and finishes that are formulated for environmental conservation, recyclability, enhanced appearance, improved durability, as well as resistance to environmental sources of contamination. Painted substrates using these new formulations are difficult to adhere to with current tape products. Another application involves mounting thermoplastic polyolefin automotive body side moldings.
Similarly, early electrical tapes were black friction tapes, and the adhesive was soft and often split when unwound. Current electrical tapes have a layer of a pressure-sensitive adhesive applied to a plasticized polyvinyl chloride backing or a polyethylene or rubber film backing. Electrical tape is used to insulate, hold, reinforce and protect electrical wires. Other uses include providing a matrix for varnish impregnation, identifying wires in electrical circuitry, and protecting terminals during manufacture of electrical circuit boards. Electrical tape, should be stretchable, conformable and meet nonflammability requirements.
Corrosion protection materials must be delivered in a conformable form for optimal performance. The ability of pressure-sensitive adhesives to instantly attach to exposed surfaces is very useful for applying protective constructions and for convenient repair of breached protective coatings associated with steel pipelines and related structures subject to corrosion. In these and related applications, the material must not readily flow or be easily rubbed off. Some of the properties of commercially available silicones are known to provide some degree of corrosion protection.
For many heat shrink applications, a single article capable of withstanding high temperature while providing an environmental seal is desired. It is preferable that the adhesive be transparent, to allow viewing of the spliced or protected region. Dual wall heat shrink tubes generally are coextruded tubes of polyolefin (the shrinkable sleeve) and EVA (for hot melt sealing). Use of these products is limited by the rheology of the hot melt. High temperature heat shrink tubes are generally made of fluorinated materials. Hotmelts used in dual wall heat shrink can be of a wide range of materials, as described in U.S. Pat. No. 4,509,820. However, no hotmelt adhesive with satisfactory flow and temperature stability has been identified for use at the shrink temperature of high temperature tubing.
Preformed pavement marking materials include pavement marking sheet materials and raised pavement markers that are used as highway and pedestrian crosswalk markings. They are often reflective and strategically oriented to enhance reflective efficiency when illuminated by vehicle headlamps at night. The marking materials must adhere to a variety of surfaces such as concrete or asphalt, that may be cold, hot, oily, damp, rough or smooth. Present pavement marking adhesive generally have inadequate initial bonding or inadequate permanent bonding to roadway surfaces that are illustrated by five problem areas: (1) limited adhesive tack at cold temperatures resulting in a narrow application window, (2) reduced durability under shear or impact causing difficult removal of temporary markings, (3) low molecular weight fractions in the adhesives on removable markings that stain light colored concrete surfaces, (4) limited ductility allowing raised markers to sometimes shatter upon impact by vehicle tires and (5) insufficient elasticity to fill in gaps between markers and rough road surfaces, thus often leading to premature detachment of the marker from the roadway surface.
Hot melt adhesives are compositions that can be used to bond nonadhereing surfaces together into a composite. During application to a substrate, hot melt adhesives should be sufficiently fluid to wet the surface completely and leave no voids, even if the surface is rough. Consequently, the adhesive must be low in viscosity at the time of application. However, the bonding adhesive generally sets into a solid to develop sufficient cohesive strength to remain adhered to the substrate under stressful conditions.
For hot melt adhesives, the transition from fluid to solid may be accomplished in several ways. First, the hot melt adhesive may be thermoplastic that softens and melts when heated and becomes hard again when cooled. Such heating results in sufficiently high fluidity to achieve successful wetting. Alternativ
Kangas Lani S.
Mazurek Mieczyslaw H.
Melancon Kurt C.
Romanko Walter R.
Sherman Audrey A.
3M Innovative Properties Company
Nakarani D. S.
Peters Carolyn V.
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