Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-12-01
2001-09-18
Szekely, Peter (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S245000, C525S247000, C525S309000, C525S310000, C525S905000, C156S333000, C156S327000
Reexamination Certificate
active
06291593
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to adhesives and more particularly to acrylic adhesives containing an inventive retarding additive to increase open time and provide other benefits.
BACKGROUND OF THE INVENTION
As used herein, “acrylic adhesives” includes methacrylic, acrylate and methacrylate adhesives. Two-component, reactive acrylic adhesives are frequently used for fabrication of plastic and metal assemblies in marine, transportation, and various other industrial applications. These adhesives offer structural bond strength, fast set time, and good resistance to temperature extremes. Acrylic adhesives, particularly methacrylate adhesives, are known in the art, which art is incorporated herein by reference; see for example U.S. Pat. Nos. 4,536,546; 4,714,730; 4,942,201 and the patents cited therein, the contents of all of which are incorporated herein by reference. Some drawbacks to using reactive acrylic and methacrylate adhesives are related to their use and cure characteristics. Acrylic adhesives, particularly methacrylate adhesives, are volatile; methacrylate adhesives are based on methyl methacrylate and other volatile methacrylate monomers. Surface evaporation of dispensed acrylic adhesives thus eventually form a dry film which results in reduced open time. Another drawback relates to the heat evolved (i.e. exotherm) while the adhesive sets or cures. Highly exothermic adhesives can distort heat sensitive substrates, such as fiber-reinforced polyester (FRP) and numerous thermoplastics. A third drawback of acrylic adhesives, particularly methacrylate adhesives, is reduced shelf-life compared to other structural adhesives like epoxies and polyurethanes. Unlike epoxies or polyurethanes, methacrylate adhesives cure by free-radical polymerization preferably initiated by certain peroxide initiators (e.g. cumene hydroperoxide or benzoyl peroxide). Since peroxides degrade more rapidly than the curing agents of epoxy or urethane technology, acrylic and methacrylate adhesives tend to be less stable.
There is a need for acrylic adhesives, particularly acrylate and methacrylate adhesives, which have longer open time and lower maximum or peak exotherm temperatures. The present invention discloses the use of inventive retarding additives which provide such improved acrylic, particularly methacrylate, adhesives.
SUMMARY OF THE INVENTION
An adhesive composition is provided which comprises 10-90 weight percent ester monomer, about 2-85 weight percent polymeric elastomer, about 0.02-10 weight percent initiator, and about 0.005-7 weight percent of a retarding additive. The retarding additive is selected from the group consisting of non-protonic Lewis acids and zinc salts and mixtures thereof. The ester monomer is selected from the group consisting of methacrylate ester monomers, acrylate ester monomers and mixtures thereof. A kit for providing a two-component reactive adhesive composition in accordance with the invention is also provided. The kit comprises a Part A chamber and a Part B chamber. The Part A chamber contains a Part A composition and the Part B chamber contains a Part B composition which is reactable with the Part A composition to yield an adhesive composition according to the invention.
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Loctite Corporation
Pearne & Gordon LLP
Szekely Peter
LandOfFree
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