Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-06-10
2003-05-06
Zalukaeva, Tatyana (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S270000, C525S109000, C525S111000, C525S455000, C525S167000, C525S169000, C525S171000, C156S327000, C156S330000, C156S332000
Reexamination Certificate
active
06559257
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to improved odor of polymerizable or curable acrylic adhesives.
BACKGROUND OF THE INVENTION
Acrylic structural adhesives are well known articles of commerce which are extensively used commercially for bonding metal and plastic materials. Acrylic structural adhesives have found growing use in the automotive industry where the adhesive bonding of metal parts is replacing welding and mechanical fastening techniques. However, these applications give rise to unique requirements not easily met by previously available adhesives. These requirements include high bond strength, improved failure mode and low odor.
Acrylic adhesives typically comprise a mixture of one or more olefinic reactive monomers such as methyl methacrylate or methacrylic acid and curing agents, with cure or polymerization being effected through a free radical polymerization mechanism. The adhesives preferably contain one or more polymeric materials which may or may not be reactive, that is, capable of being polymerized per se or at least capable of interpolymerizing with the reactive monomers, such as grafting onto or crosslinking the growing polymers from the reactive monomer polymerization. In addition, the adhesives can contain other additives for improving adhesion to substrate materials, environmental resistance, impact strength, flexibility, heat resistance, and the like.
P.C.T. Publication WO 97/39074 discloses the use of at least one polymeric material which can act as a toughening agent in an acrylic adhesive such as polychloroprene, polymer-in-monomer syrup, chlorosulphonated polyethylene rubber, copolymers of butadiene and at least one monomer copolymerizable therewith, for example, styrene, acrylonitrile, methacrylonitrile (e.g. poly(butadiene-(meth)acrylonitrile or poly(butadiene-(meth)acrylonitrile-styrene) and mixtures thereof; as well as modified elastomeric polymeric materials, such as butadiene homopolymers and copolymers as noted above modified by copolymerization therewith of trace amounts of up to about 5 percent by weight of the elastomeric material of at least one functional monomer (such as acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, styrene, and methyl methacrylate to give, for example, methacrylate-terminated polybutadiene homopolymers and/or copolymers).
U.S. Pat. No. 4,769,419 (“the '419 patent”), incorporated herein by reference, discloses structural adhesive compositions for metal—metal bonding applications. The adhesives include as tougheners olefinic terminated liquid rubbers which are reacted with monoisocyanate compounds. These tougheners represented by formula I as shown in column 4 and claim 1 of the '419 patent are referred to herein as “urethane modified olefinic-terminated liquid elastomer produced from a carboxylic acid-terminated alkadiene” or, alternatively, as “isocyanate-capped methacrylate-terminated polyalkadiene produced from a carboxylic acid-terminated polyalkadiene”. The '419 patent further describes acrylic adhesives with olefinic monomer, olefinic urethane reaction product of an isocyanate-functional prepolymer and a hydroxy-functional monomer, phosphorus-containing compounds, an oxidizing agent and a free radical source.
U.S. Pat. No. 5,641,834 (“the '834 patent”) and U.S. Pat. No. 5,710,235, both incorporated herein by reference, disclose adhesives that include as tougheners an olefinic-terminated polyalkadiene that includes carboxy ester linking groups and at least one nascent secondary hydroxyl group that is capped with a monoisocyanate. These tougheners represented by the formulae for polymer A or polymer B in claim 1 are referred to herein as “olefinic-terminated liquid elastomer produced from a hydroxyl-terminated polyalkadiene” or, alternatively, as “isocyanate-capped methacrylate-terminated polyalkadiene produced from a hydroxyl-terminated polyalkadiene”. The composition also includes a free radical-polymerizable monomer such as an olefinic monomer and, optionally, a second polymeric material. In a preferred embodiment the composition is an adhesive that also includes a phosphorus-containing compound and an ambient temperature-active redox catalyst. The '834 patent describes polymers A and B with a number average molecular weight of about 1,500 to 10,000, preferably about 1,500 to 6,000.
The odor of acrylic adhesives leaves room for improvement.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide an adhesive that has a lower or less objectionable odor. According to the invention there is provided an adhesive that includes a free radical-polymerizable monomer component that includes at least a reaction product of a (hydroxy)acrylate with an anhydride but is substantially free of methyl methacrylate or methacrylic acid.
DETAILED DESCRIPTION OF THE INVENTION
The free radical-polymerizable monomer component typically is a mixture of free radical-polymerizable monomer that at least includes a monomer that is a reaction product of a (hydroxy)acrylate with an anhydride. The presence of this reaction product allows for the removal from the adhesive formulation of at least one of methyl methacrylate, methacrylic acid or other offensive odoriferous monomers. The adhesive compositions are substantially free of at least methyl methacrylate or methacrylic acid because the use of these ingredients in amounts as little as 2 or 3 weight percent results in offensive odor emissions in certain applications. As the term “substantially free of methyl methacrylate or methacrylic acid” is used herein, it is intended to mean trace amounts or amounts less than an offensive odor generating amount which can be as little as 2 or 3 weight percent of the total formulation.
The odor of methacrylic acid can be particularly offensive. Thus, according to one embodiment of the invention the monomer component can include methylmethacrylate but is substantially free of methacrylic acid.
The (hydroxy) acrylate compound utilized to prepare the reaction product included in the monomer component of the invention can be any acrylate compound characterized by the presence of a hydroxy group. Examples of suitable hydroxy-functional acrylate compounds include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl acrylate, 2-hydroxybutyl methacrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 3-hydroxypentyl acrylate, 6-hydroxynonyl acrylate, 3-hydroxypropyl methacrylate, 2-hydroxypentyl methacrylate, 5-hydroxypentyl methacrylate, 7-hydroxyheptyl methacrylate, 5-hydroxydecyl methacrylate, N-hydroxymethyl acrylamide, N-hydroxymethyl methacrylamide, diethylene glycol monoacrylate, diethylene glycol monomethacrylate, glycerin dimethacrylate, tri-methylol propane dimethacrylate, alkoxylated hydroxyethyl acrylate, trimethylolpropane diacrylate, alkoxylated trimethylolpropane diacrylate, reaction products of polyether glycols of acrylic or methacrylic acid and the like.
Other hydroxy-functional acrylate compounds are lactone-modified acrylate or methacrylate acid esters (hereinafter “lactone-acrylate adducts”) prepared by reacting an appropriate lactone with a hydroxy-functional acrylate compound defined in the preceding paragraph as is known in the art. Lactones employed in the preparation of the lactone-acrylate adducts may be the same as the lactones defined above with respect to the preparation of the lactone-based polyester polyols. An example of a lactone-acrylate adduct is a 2-hydroxyethyl acrylate-caprolactone adduct such as TONE M-100 supplied by Union Carbide Corporation.
The anhydride that is reacted with the (hydroxy)acrylate compound can be maleic anhydride, succinic anhydride, phthalic anhydride, alkylsuccinic anhydride, alkenylsuccinic anhydride and the like. The preferred reaction product is monomethacryloyloxyethyl phthalate commercially available from International Specialty Chemicals under the trade designation BISOMER EMP.
The other free radical-polymerizable monomers that can be p
Dearth Miles B.
Lord Corporation
Zalukaeva Tatyana
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