Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1998-04-02
2001-06-12
Lipman, Bernard (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C106S277000, C106S278000, C106S600000, C106S632000, C106S633000, C524S157000
Reexamination Certificate
active
06245850
ABSTRACT:
TECHNICAL FIELD
The invention relates to bituminous coatings and sealants. More particularly, it relates to method and composition for reflective asphalt emulsions for roofing, waterproofing, paving, coating, and sealing.
BACKGROUND OF THE INVENTION
The present invention relates to reflective asphalt emulsions and more particularly to novel method and compositions for producing such reflective emulsions, which may be used advantageously as a roofing and waterproofing composition having superior characteristics.
Prior asphalt emulsion mixtures have been applied to roofs and other substrates, sometimes as a protective coating and sometimes as a re-cover system, using a reinforcing sheet. Such asphalt mixtures have little or no reflectivity in that they are typically black in color. In many circumstances, however, it has been found desirable to use asphalt coatings and sealants for roofing, paving, waterproofing, sealing, etc., with increased reflectivity. This is particularly true where the asphalt is exposed to sunlight and other solar radiations. For example, it has long been known that asphalt roofing installations are subject to moderately severe thermal expansion and contraction cycles as they heat beneath the sun during the day and cool at night. Repeated thermal shock cycles of this type lead to accelerated breakdown of the asphalt and destroy its effectiveness as a roofing, waterproofing, or sealing membrane, and therefore lead to eventual damage to the protected structure due to rain and weather. And while it has long been realized that increasing the reflectivity of such installations would decrease their absorption of solar radiation, and thereby reduce the thermal stresses and shock cycles to which they are subjected—and thus would prolong the life of the installations and of the structures they are intended to protect—no satisfactory means for increasing the reflectivity of asphalt has yet been put forward.
One proposal has involved the use of aluminum coating asphalts. Such asphalts provide a thin aluminum surface coating atop an installed asphalt layer (or membrane) and provide relatively high reflectivity. But while aluminum coating asphalts have been found to be extremely useful and beneficial in many applications, it has also been found that in many other circumstances they are not suitable. For example, the aluminum coating formed in the application of such asphalts is typically extremely thin, and, as the asphalt beneath or behind it hardens, the coating tends to become relatively brittle. In such circumstances relatively light physical impacts can break the coating, and cause flaking and therefore loss of reflectivity and even (when the asphalt beneath it breaks also) loss of moisture resistant integrity. For example, the surface of an installed aluminum coating roofing asphalt for a portion of a roof subjected to foot traffic (as for example for maintenance purposes) tends to break down and lose substantial portions of its reflectivity due to the stresses caused by individuals walking on it, leading to increased thermal shock loadings in the asphalt and eventual failure of the asphalt as a roofing membrane.
Another approach has been the simple painting of asphalt installations, using, for example, light-colored latex paints. But paints used in such installations typically cannot weather the stress of physical impacts, such as the walking previously described, or the ponding of water (as for example during or after rainstorms), and they do not wear well: they tend to both break down structurally and lose reflectivity with age and exposure.
Thus there is a need for a durable, wear-resistant, highly reflective asphalt suitable for use in roofing, waterproofing, and sealing applications, and for application at ambient temperatures.
DISCLOSURE OF THE INVENTION
It is accordingly an object of the invention to provide a means of producing a highly reflective asphalt membrane, as for example in a roofing, waterproofing, or sealing membrane.
It is another object of the invention to provide a reflective asphalt membrane that is highly durable and resistant to wear.
It is another object of the invention to provide roofing, waterproofing, and sealing membranes in the form of a black asphalt emulsion changed to a light colored (white to gray) asphalt emulsion, so as to provide a reflective asphalt emulsion which may be spread directly on surfaces exposed to the weather with or without the use of reinforcing sheeting.
It is another object of this invention to provide a reflective asphalt emulsion which is suitable for application at ambient temperatures.
It is a further object of this invention to provide method and composition for making such an asphalt emulsion by mixing an asphalt emulsion with a titanium dioxide pigment in a manner to maintain stable emulsification and result in a non-brittle emulsive coating having enhanced reflective properties.
It is a further object of the invention to provide method and apparatus for providing such compositions having improved elasticity, resistance to thermal shock cycles, and resistance to ozone and ultraviolet rays by including in such compositions white latex and/or SEBS rubber as additives.
The invention provides such an asphalt and method for producing them.
One aspect of the invention is a method for preparing an asphaltic emulsion of bentonite clay, asphalt, and water. One such method starts by initially mixing bentonite clay and a lignosulfonate dispersant in a high shear mixer, and a 100% oxidized emulsion grade or a paving grade asphalt having a softening point of about 110° to 180° F. at a temperature of about 240° to about 320° F. into a composition of about 30 to 60 percent and preferably about 45 percent by weight of asphalt. The mixture is sheared until the resulting composition is smooth. The resultant emulsion contains: (1) asphalt, (2) clay or other emulsifiers, (3) water, and (4) miscellaneous other chemicals in smaller quantities. Titanium dioxide pigment together with a small amount of filler, such as diatomaceous earth, is then added under low shear so that the emulsion does not break down. The titanium dioxide pigment is added in the amounts of from 10 to 20 percent by weight of the finished emulsion so that the finished color of the emulsion is white to light gray. The emulsion has a consistency of soft putty and is creamy in texture. The finished product has a weight of about 8.0 to 11.0 pounds per gallon and preferably about 9.0 to 10.0 pounds per gallon. The emulsion is stable and may be stored in containers before use. In another such method, the reflective asphalt is formed by preparing a slurry, at a temperature of from 100° to 130° F., of bentonite clay and water with an emulsifier and/or a dispersant; preheating an asphalt having a softening point of from about 100° to about 180° F. to a temperature within the range from about 240° to about 320° F. and mixing said slurry with said asphalt while agitating at a shearing speed of about 2000 rpm to emulsify the slurry and asphalt into a paste; cooling said paste to below about 100° F.; blending at low shear a quantity of titanium dioxide pigment and a small quantity of diatomaceous earth filler into said paste so that the resulting paste has a white to light gray color and a soft consistency. Another aspect of the invention comprises a product produced by this method and used for coating surfaces, the product being characterized by having a high reflectivity of various electromagnetic waves, including particularly visible solar radiations.
A particularly advantageous variant of the method aspect of the invention is a method for preparing a reflective asphaltic emulsion of an emulsifier, a dispersant, asphalt, and water. This method comprises the steps of preparing a slurry at a temperature of from 100° F. to 130° F. of an emulsifier and water; preheating an asphalt having a softening point of from about 90° F. to about 225° F. to a temperature within the range from about 240° F. to about 320° F.; mixing the slurry with said asphalt at a shearing spee
Brown & Raysman Millstein Felder & Steiner LLP
Lipman Bernard
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