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
2000-05-10
2002-10-08
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...
C525S261000
Reexamination Certificate
active
06462126
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates generally to structural acrylic/methacrylic adhesives and more particularly to acrylic/methacrylic adhesives used for construction purposes or the assembly of large objects.
Many products, ranging from car parts to boats to truck cabs and other structures are made by bonding various sheets (panels) of material, such as fiberglass, with adhesives. For example, U.S. Pat. Nos. 4,942,201 and 4,714,730, assigned to ITW of Glenview, Ill., the contents of which are incorporated herein by reference, describe adhesives made with methacrylate and acrylate based adhesives together with various other additives and ingredients for use in the construction of large objects.
Available adhesives have exhibited certain inadequacies in their potential application to various construction and manufacturing methods. For example, it is often desirable to apply the adhesive to a first surface of a panel and permit the adhesive to remain “open” and uncured for working times longer than one hour or more before the panel is adhered to another structure. For example, during the construction of large boats, the panel to be adhered could be 30 feet or longer and the bead, typically applied in a serpentine fashion would be even longer. It is therefore necessary for the beginning of the bead to remain workable and uncured until it is time to adhere the panel. This period of time, between the time when the adhesive is applied to a first substrate and when that first substrate is pressed to a second substrate to bond the first substrate to the second substrate will be referred to herein as “open time”.
It is also desirable for adhesives to exhibit excellent cure properties, even when applied to cross sections well above {fraction (1/16)} of an inch. For example, when large panels are fastened to structures with adhesive, the gap between the two members can vary in thickness.
Gaps in a pair of adhered 20-50 foot panels can be 1 inch or more. Adhesives that are applied to this thickness generate considerable heat while curing. Methyl methacrylate boils at 210° F. It is undesirable for the adhesive to boil during curing, because bubbles can form thereby reducing structural integrity of the bonded assembly.
It is also desirable for adhesives to cure over a wide range of temperatures, including cold temperatures below 65° F. and hot temperatures that one might experience when building boats in southern Florida. Thus, it is desirable for adhesive to cure at cold temperatures, yet remain open for sufficiently long times at hot temperatures.
Available adhesives have exhibited other inadequacies. For example, many state of the art adhesives can “swim” on materials when a first panel is bonded to a second panel in an overhead or vertical arrangement. Parts are often bonded before fiber reinforced polymer materials have fully cured. The adhesive can solvate the bonding surface to the extent that a boundary layer of liquid methacrylate and e.g. polyester is formed between the bulk of the adhesive bead and the surface being bonded. The adhesive bead can then “swim” down the vertical surface or in the case of overhanging overhead surfaces, fall off. This swimming phenomenon has interfered with the use of methacrylate and acrylate adhesives for structural bonding of large members in vertical or overhanging positions. Thus, in many instances, it has become necessary to hold the members being bonded until the adhesive has cured. This can interfere with construction times and can in certain instances, make the use of adhesives undesirable or impossible without complicating the manufacturing process or employing additional fastening mechanisms.
Accordingly, it is desirable to provide a new adhesive and method of forming the adhesive which overcome drawbacks of the prior art.
SUMMARY OF THE INVENTION
Generally speaking, in accordance with the invention, an adhesive comprising a combination of high molecular weight acrylic and/or methacrylic esters, which become co-polymerized with low molecular weight acrylic and/or methacrylic esters, and advantageously polymers, such as impact modifiers including graft co-polymer (core-shell and non core-shell) impact modifiers, carboxylic acids, elastomers, and sulfur bearing compositions, such as chloro sulfonated polymers and other active sulfur moieties is provided.
Accordingly, it is an object of the invention to provide an improved adhesive.
Another object of the invention is to provide an improved method of making adhesives.
Still another object of the invention is to provide improved structures bonded together with adhesives.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification and the drawings. The invention accordingly comprises a composition of matter possessing the characteristics, properties, and the relations of components which will be exemplified in the compositions hereinafter described, and the scope of the invention will be indicated in the claims. The invention also comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the constructions, compositions and articles embodying the features of construction, combinations and arrangements of parts which are adapted to effect such steps, and the articles, constructions and compositions which possess the characteristics, properties and relations of elements, all as exemplified in the detailed disclosure hereinafter set forth.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
This invention is directed to structural adhesive compositions.
The adhesive compositions of this invention can be made by combining:
(A) a methacrylate or acrylate ester monomer;
(B) an elastometric polymer soluble in the ester monomer;
(C) a graft copolymer;
(D) a free radical producing catalyst;
(E) an organic acid; and
(F) a sulfur bearing compound.
Adhesive compositions of this invention will advantageously contain about 40 to about 70 weight percent methacrylate ester monomer, 0 to about 15 weight percent acid monomer, about 5 to about 20 weight percent elastomer and about 10 to about 30 weight percent graft copolymer, said weight percents being based on the total weight of the components. Preferably, the compositions contains about 50 to about 60 weight percent methacrylate ester monomer, about 0.1 to about 5 weight percent acid monomer, about 8 to about 15 weight percent elastomer and about 15 to about 25 weight percent graft copolymer.
The monomers useful in this invention include a combination of high molecular weight (MW) and low molecular weight methacrylate and acrylate ester monomers which are copolymerized during the curing process. The low molecular weight monomers are characterized by the alcohol portion of the ester group having 1 to 8 carbon atoms. The high molecular weight monomers are characterized by the alcohol portion of the ester group having 9 to 40 carbon atoms.
Examples of such low molecular weight ester monomers are methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethyhexyl methacrylate, cyclohexyl methacrylate and mixtures thereof. The preferred low MW ester monomer is methyl methacrylate.
Additional low molecular weight ester monomers which can be used alone or in combination with the methacrylate monomers are acrylate esters, examples of which are methyl acrylate, ethyl acrylate, butyl acrylate and 2-ethyhexyl acrylate. Other useful monomers are acrylonitrile, methacrylonitrile, styrene, vinyl toluene, and the like.
The low molecular weight monomer is advantageously included as about 50 to 60% of the adhesive composition.
Examples of such high molecular weight monomers are steryl methacrylate, lauryl methacrylate, polyethylene glycol methacrylates, and isodeceyl methacrylate.
The preferred high MW monomers are lauryl methacrylate and methoxy polyethylene glycol mono methacrylate. High molecular weight acrylates, particularly those with ether linkages, in effective amounts, appear useful in controlling boiling during curing.
The high mo
Gosiewski Donald
Lambert Kenneth A.
Leeser Daniel L.
Loven William E.
Illinois Tool Works Inc.
Michl Paul R.
Pitney Hardin Kipp & Szuch LLP
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