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
2001-06-14
2004-05-11
Sellers, Robert (Department: 1712)
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...
C252S182180, C524S559000, C526S230000, C526S230000
Reexamination Certificate
active
06734249
ABSTRACT:
BACKGROUND OF INVENTION
This invention pertains to a room-temperature fast-curing acrylate adhesive useful for structural applications including fiber optic connector assembly.
Presently, various methods are used to affix an optical fiber in a fiber optic connector so that the fiber does not move over time and during use. Movement of the fiber is problematic due to the potential for signal loss when two connectors are in alignment. One common method of securing the optical fiber in the connector is through use of an epoxy resin. Epoxy resins, however, are typically cured at high temperature when securing fibers in the connector. This adds cost to the installation process in that ovens are needed to effect curing at a reasonable rate. Typically, the curing occurs at 120° C. for about twenty minutes. The present inventors have recognized that a need exists for an adhesive which cures at room temperature to afford stable connections. The present inventors have determined that a solution to this problem would be highly desirable.
In an effort to find a solution to the problem, it was decided to investigate acrylate adhesives.
Acrylate adhesives are well known. For instance, U.S. Pat. No. 5,865,936, R. Edelman and W. J. Catena, describes the formulation of rapid curing two-part structural acrylate adhesives using a first part consisting of a mixture of acrylate and methacrylate monomers or oligomers, maleic acid, a hydroperoxide, and a source of ferric ions. A second part, the activator, is a substituted dihydropyridine.
U.S. Pat. No. 4126504, L. E. Wolinski and P. D. Berezuk, describes a fast-curing acrylate adhesive comprising of an elastomer dissolved in acrylate or methacrylate monomers initiated by benzoyl peroxide that is activated with a tertiary amine in the presence of an oxidizable heavy metal.
U.S. Pat. No. 4,112,013, P. C. Briggs, Jr. and L. C. Muschiatti, describes a room-temperature curing adhesive containing various acrylate monomers polymerized in the presence of a high amount (>20%) of either chlorosulfonated polyethylene or a mixture of chlorinated polyethylene and sulfonyl chloride. The method utilizes a peroxide as a free-radical generator, an organic salt of a transition metal as a promoter, an aldehyde-amine condensation product as an accelerator, and a tertiary amine as an initiator. These adhesives may be formed as a two-component system or as a primer system. A similar method for room-temperature cure adhesives is described in U.S. Pat. No. 4,263,419 by G. Piestert and H. G. Gilch.
However, the present inventors recognized that none of these references discloses an acrylate adhesive that cures at room temperature and is dimensionally stable under load. The present inventors recognized that a need existed for such an adhesive.
SUMMARY OF INVENTION
This invention solves one or more of the problems and disadvantages described above. This invention provides a room-temperature fasturing acrylate adhesive useful for structural applications including fiber optic connector assembly. The adhesive may either be a two-component system or a primer-based system in which the surfaces to be bonded are primed before the adhesive is applied. The adhesives exhibit high modulus, low water absorptivity, excellent adhesion, and high glass transition and heat deflection temperatures. The most important and unexpected characteristic of these room temperature cured acrylate adhesives is the dimensional stability of the adhesive under load and at elevated temperature.
In one broad respect, this invention is a two-part adhesive system which may comprise:
(a) an adhesive part A which may be comprised of:
one or more monofunctional, difunctional, or trifunctional acrylate or methacrylate monomers,
a peroxide or hydroperoxide free-radical initiator,
an antioxidant such as of the quinone family, and
optionally, additives such as thickeners, thixotropes, and adhesion promoters;
(b) an activator part B which may be comprised of:
a N,N-disubstituted aromatic amine,
a difunctional methacrylate monomer,
an antioxidant such as of the quinone family, and
optionally, additives such as thickeners, thixotropes, and adhesion promoters.
Each of the parts of the system is mixed to form a substantially homogeneous composition prior to use. When the two parts of this system are mixed, reaction occurs to form the resulting adhesive. That is, a reaction product forms when the two parts of the system are mixed to initiate curing. Advantageously, this curing can occur at room temperature. The reaction product (which may be referred to as the cured adhesive) resulting from the admixture of part A and part B has excellent dimensional stability and affords an excellent material to use as an adhesive for fiber optic connectors.
In another respect, this invention is a primer-based adhesive system which may comprise:
(a) an adhesive part A which may be comprised of:
one or more monofunctional, difunctional, or trifunctional acrylate or methacrylate monomers,
a peroxide or hydroperoxide free-radical initiator,
an antioxidant such as of the quinone family, and
optionally, additives such as thickeners, thixotropes, and adhesion promoters;
(b) a primer part B which may be comprised of:
a N,N-disubstituted aromatic amine,
an adhesion promoter, and
a solvent.
In another embodiment, the primer-based adhesive system may comprise:
(a) an adhesive part A which may be comprised of:
one or more monofunctional, difunctional, or trifunctional acrylate or methacrylate monomers,
a N,N-disubstituted aromatic amine,
an antioxidant such as of the quinone family, and
optionally, additives such as thickeners, thixotropes, and adhesion promoters;
(b) a primer part B which may be comprised of:
a peroxide or hydroperoxide free-radical initiator, and
a solvent.
In the primer based systems, part A and part B are each mixed prior to use. When a given surface is to be joined to another surface, the primer is first applied and the solvent allowed to evaporate. The A part is then applied onto the primed surface, whereupon the reaction is initiated to form the final adhesive product. The second surface is contacted with the adhesive before it completely cures. Normally, the second surface will be pressed against the first surface immediately after the A part is applied to the primed surface. Alternatively, the A part can be applied to the second surface and then pressed against the primed surface.
The type of substrates and surfaces on which the adhesive of this invention may be used vary widely. For example, the type of surfaces that can be treated with the adhesives of this invention includes glass, ceramics, metals, and plastics. A particularly advantageous use is in the fiber optic application. In this case, for instance, the two-part system of this invention is mixed and injected into the ferrule of a connector. Then, the optical fiber is inserted into the ferrule. The ferrule is often made of metal and/or a ceramic material. The adhesive is allowed to cure, which sets the fiber in place within the connector.
In another broad respect, this invention is the reaction product of each of two-part composition and the primer compositions That is, this invention includes the reaction product (the cured adhesive) resulting from the curing of the admixture of part A and part B in the embodiments of this invention. In yet another broad respect, this invention is a process useful for adhering one surface to a second surface, which comprises applying a primer part B as described above to the first surface, allowing the solvent to evaporate so that the initiator (or activator) is on the first surface, applying the part A to the primed surface, pressing the first surface to the second surface so that the adhesive is sandwiched between the two surfaces until the adhesive is cured. Alternatively, the adhesive part A can be applied to the second surface in an area complementary to the placement of the primer part B, and then the two surfaces are pressed together so that part A and part B come into contact. In another broad respect, this invention is
Bulluck John Werner
Rix Brad A.
O'Keefe Egan & Peterman, LLP
Sellers Robert
Texas Research International, Inc.
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