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
1999-07-29
2002-07-02
Michl, Paul R. (Department: 1714)
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
active
06414077
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates in general to the field of moisture curable sealants, and more particularly, to a sealant that is warm-applied, provides green strength and is transformed from a thermoplastic to a non-thermoplastic sealant by curing at room temperature using ambient moisture.
BACKGROUND OF THE INVENTION
Without limiting the scope of the invention, its background is described in connection with compositions and methods for the use of a sealant that is curable using ambient moisture at room temperature, as an example.
Various sealant compositions are available that may be cured by exposure to atmospheric moisture, such as those that are based on isocyanate-terminated polyurethanes or silicone polymers. Yet another type of sealant is a so-called “hot melt adhesive”. Typical hot melt adhesives set quickly due to instant cooling after application and thus provide a narrow window of time in which the position of the substrate, such as glass, may be adjusted within the frame after application. Hot melt adhesives also require high application temperatures typically in excess of 300° Fahrenheit.
Generally, the choice of sealant products has been determined by a balance between good quality seals and price. Sealants based on isocyanate-terminated polyurethanes, however, are unsuitable for long-term packaging and storage due to their short shelf life, i.e., they tend to harden in situ. Also, isocyanate based sealants suffer from the drawback of limited thermal stability.
Another problem observed with these types of polyurethane polymers is bubble formation, which results from the production of carbon dioxide during the curing process. Also, heat-resistance of the seals formed is only moderate in many cases and UV resistance through glass is poor.
Sealants based on silicone polymers, on the other hand, generally have desirable properties and yield seals of high quality that perform well under many conditions. Silicone-based systems offer both clear sealing and good ultra-violet light stability. Unfortunately, both the polyurethane hot-melts and silicone sealants typically tend to require expensive materials. Silicon sealants may not possess the desired adhesion characteristics when used in connection with some substrates, particularly in high moisture environments. Another drawback of silicon sealants is the fact that they do not provide a substrate to which a coating, such as paint or stains, will adhere. They also cause contamination problems on substrates.
Various moisture-curable compositions are known in the art. For example, U.S. Pat. No. 4,043,953, entitled “Ambient Temperature Moisture-Curable Acrylic-Silane Coating Compositions Having Improved Potlife”, discloses an ambient temperature, moisture-curable coating composition that includes as one part an acrylic-silane interpolymer of an ethylene monomer and a vinylalkoxysilane. U.S. Pat. No. 4,707,515, entitled “Moisture-Curable Sealant Compositions,” discloses a sealant composition capable of curing using atmospheric moisture formed from a reaction of substantially linear acrylate ester polymer with a hydrolyzable silane having an amino functional silane group. U.S. Pat. No. 4,147,685 and U.S. Pat. No. 4,177,301, entitled “Adhering Silicone Compositions,” and “Primer Compositions for Adhering Silicone Compositions”, respectively, disclose primer compositions that are the reaction product of methyl- or butylmethacrylate or butylacrylate and an acrylate functional silane that is moisture curable at room temperature. Wakabayashi, U.S. Pat. No. 4,910,255, entitled “Curable Composition”, discloses a composition containing a copolymer that has silicon-containing functional groups capable of cross-linking by forming siloxane bonds, alkyl acrylate monomer from 1 to 8 carbons, and alkyl acrylate monomers with at least 10 carbons as a co-reactant with a silane terminated polyoxypropylene based polymer.
None of the previously mentioned patents disclose materials in which a second silane groups is used to cap some of the polymer chains. As a result of the inclusion of this second type of silane unit, the composition claimed here meets the need for a sealant with desirable physical properties not found in the prior art.
SUMMARY OF THE INVENTION
What is needed is a sealant composition curable by atmospheric moisture, that forms a resilient seal at ambient temperatures and that is manufactured with inexpensive raw materials. The sealant composition must also have a desirable combination of properties, such as, convenient application, and a long storage life. Another preferred feature of a sealant is that it provides an opportunity for re-seating the materials in case its position is not exact or an alternative position is preferred, and that is capable of curing using atmospheric moisture. The sealant must also be produced in a cost-effective manner. The sealant formulation of the current invention meets all of these criteria.
The moisture curable composition of the present invention may be warm applied or may be applied as a low viscosity solvent-containing sealant under ambient conditions. When warm applied, the present invention differs substantially from “hot melt” sealants in that the method of curing the sealant of the present invention does not depend on temperature. As distinguished from “hot melt” sealants, the sealant of the present invention for warm application is stored as a viscous semi-solid that is warmed to increase mobility. Therefore, the warm applied sealant is not melted and hardened when it cools, as is the case with “hot melt” sealants. The sealant of the present invention cures when exposed to atmospheric moisture to form a non-thermoplastic sealant, which is highly elastic and adhesive.
The warm applied sealant of the present invention cures chemically, not thermally, and is stable in the warm form as compared to conventional moisture curing hot melt sealants based on polyurethane chemistry. The sealant is produced by admixing a polymer with various additives that produce a sealant with superior green strength and curability. Unlike conventional hot melt sealants, the warm-applied sealant of the present invention allows for repositioning of substrates after application and prior to chemical curing to a non-thermoplastic rubbery sealant.
The curable, warm-applied composition of the present invention is useful for many purposes such as sealant adhesives, pressure-sensitive adhesives, water proofing agents, sealant compositions, casting rubber materials and foaming materials. Using the moisture curable composition of the present invention, the inventors have sealed windows in compliance with the AMAA's guidelines for sealants. The present composition and method for curing a sealant includes mixing the components in a relatively moisture-free condition. Once blended, the composition may be stored for a prolonged period at ambient temperature without degradation in a sealed container. The composition of the present invention cures rapidly to form a good rubber elastomer upon exposure to atmospheric moisture.
The curable composition of the present invention is used as a one-component elastomeric sealing material that displays superior weather resistance, may be transparent or pigmented and have high tensile strength and elongation. The composition of the present invention readily accepts paint, which is in contrast to silicone-based sealants, which do not. It also displays greatly improved characteristics for use as a highly elastic sealant in window creation and packaging and other areas.
The moisture curable composition of the present invention may be used as a waterproofing agent. It also exhibits a good balance between breaking strength, elongation, and glass transition temperature, while at the same time having a long storage life and improved application during manufacturing as compared to products prepared by existing techniques using more expensive components.
The curable composition of the present invention may also be used as an adhesive because it exhibits high bo
Barron Larry R.
Damschroder Brian L.
Flores Edwin S.
Gardere Wynne & Sewell LLP
Michl Paul R.
Schnee-Morehead, Inc.
Warren, Jr. Sanford E.
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