Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
2002-03-11
2004-05-11
Berman, Susan (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S024000, C522S026000, C522S028000, C522S173000
Reexamination Certificate
active
06734221
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to radiation-curable compositions, which include a cyanoacrylate component or a cyanoacrylate-containing formulation, a photoinitiated radical generating component and a photoinitiator component.
2. Brief Description of Related Technology
Cyanoacrylates generally are quick setting materials which cure to clear, hard glassy resins, useful as sealants, coatings, and particularly adhesives for bonding together a variety of substrates [see e.g., H. V. Coover, D. W. Dreifus and J. T. O'Connor, “Cyanoacrylate Adhesives” in
Handbook of Adhesives
, 27, 463-77, I. Skeist, ed., Van Nostrand Reinhold, New York, 3rd ed. (1990)].
Ordinarily, upon contact with substrate materials possessing a surface nucleophile, cyanoacrylate-containing compositions spontaneously polymerize to form a cured material. The cured material exhibits excellent adhesive properties to materials such as metals, plastics, elastomers, fabrics, woods, ceramics and the like. Cyanoacrylate-containing compositions are thus seen as a versatile class of single-component, ambient temperature curing adhesives.
With conventional polymerizable compositions other than those containing cyanoacrylate monomers, radiation cure generally presents certain advantages over other known cure methods. Those advantages include reduced cure time, solvent elimination (which thereby reduces environmental pollution, and conserves raw materials and energy) and inducement of low thermal stressing of substrate material. Also, room temperature radiation cure prevents degradation of certain heat sensitive polymers, which may occur during a thermal cure procedure.
Radiation-curable, resin-based compositions are legion for a variety of uses in diverse industries, such as coatings, printing, electronic, medical and general engineering. Commonly, radiation-curable compositions are used for adhesives, and certain of the compositions are acrylate-based compositions.
Well-known examples of radiation-curable, acrylate-based resins include those having structural backbones of urethanes, amides, imides, ethers, hydrocarbons, esters and siloxanes. [See e.g., J. G. Woods, “Radiation-Curable Adhesives” in
Radiation Curing: Science and Technology
, 333-98, 371, S. P. Pappas, ed., Plenum Press, New York (1992).] The common cure mechanism for such radiation-curable, acrylate-based compositions is reported to be free-radical polymerization.
European Patent Publication EP 393 407 describes a radiation-curable composition which includes a slow cure cationic polymerizable epoxide, a fast cure free radical polymerizable acrylic component and a photoinitiator. Upon exposure to radiation, the photoinitiator is said to be capable of generating a cationic species which is capable of initiating polymerization of the epoxide and a free radical species which is capable of initiating polymerization of the acrylic component. The polymerizable acrylic component includes monofunctional acrylates and acrylate esters, such as cyano-functionalized acrylates and acrylate esters, examples of which are expressed as 2-cyanoethyl acrylate (CH
2
═CHCOOCH
2
CH
2
CN) and 3-cyanopropyl acrylate (CH
2
═CHCOOCH
2
CH
2
CH
2
CN). (See page 5, lines 19-26.)
U.S. Pat. No. 4,707,432 (Gatechair) speaks to a free radical polymerizable composition which includes (a) polymerizable partial esters of epoxy resins and acrylic and/or methacrylic, and partial esters of polyols and acrylic acid and/or methacrylic acid, and (b) a photoinitiator blend of a cyclopentadienyl iron complex and a sensitizer or photoinitiator, such as an acetophenone.
In C. Kutal, P. A. Grutsch and D. B. Yang, “A Novel Strategy for Photoinitiated Anionic Polymerization”,
Macromolecules
, 24, 6872-73 (1991), the authors note that ethyl cyanoacrylate is “unaffected by prolonged (24-h) irradiation with light of wavelength >350 nm” whereas in the presence of NCS
−
, cyanoacrylate is observed to solidify immediately, generating heat in the process. Though the NCS
−
was not in that case generated as a result of irradiation, it was generated from the Reineckate anion upon ligand field excitation thereof with near-ultraviolet/visible light. See also U.S. Pat. No. 5,652,280 (Kutal) U.S. Pat. No. 5,691,113 (Kutal) and U. S. Pat. No. 5,877,230 (Kutal).
International Patent Application PCT/US98/03819 describes photocurable compositions including a cyanoacrylate component, a metallocene component and a photoinitiator component.
European Patent Publication No. EP 769 721 A1 describes a photocurable compositions of (a) an &agr;-cyanoacrylate and (b) a metallocene compound comprising a transition metal of group VIII of the periodic table and aromatic electron system ligands selected from &pgr;-arenes, indenyl, and &eegr;-cyclopentadienyl. The photocurable composition may further include (c) a cleavage-type photoinitiator. U.S. Pat. No. 5,814,180 (Mikuni) describes such compositions in the context of a method of bonding artificial nails.
Although the predominant mechanism by which cyanoacrylate monomers undergo polymerization is an anionic one (which as noted above is typically initiated using a nucleophile), free-radical polymerization is also known to occur. Such free radical polymerization is however seen as troublesome since it tends to reduce shelf-life stability under prolonged exposure to heat or light of an appropriate wavelength. See e.g., Coover et al., supra. Ordinarily, free-radical stabilizers, such as quinones or hindered phenols, are included in cyanoacrylate-containing adhesive compositions to consume free radicals that are generated by light and under typical non-airtight storage conditions, thereby extending the adhesive's shelf life. Thus, the extent of any free-radical polymerization of commercial cyanoacrylate-containing adhesive compositions is especially undesirable for at least the reason stated and in practice is typically minimal due to the inclusion of such free-radical stabilizers.
It is not believed to date that a cyanoacrylate-based adhesive composition has been developed to rapidly cure through a photoinitiated free radical mechanism, while retaining commercially acceptable shelf life stability. Such a composition would be desirable as possessing the benefits and advantages of cyanoacrylate-containing compositions while curing through at least a photo-induced free radical polymerization mechanism.
SUMMARY OF THE INVENTION
The present invention provides compositions which include a cyanoacrylate component or a cyanoacrylate-containing formulation, a photoinitiated radical generating component and a photoinitiator component. Such compositions cure after exposure to radiation in the electromagnetic spectrum.
The photocurable compositions of this invention retain those benefits and advantages of traditional cyanoacrylate-containing compositions while curing through at least a photo-induced free radical polymerization mechanism, thereby providing to the compositions (and cured reaction products formed therefrom) the benefits and advantages of curing through such a mechanism. More specifically, photocurable compositions of this invention cure rapidly when used, and in so doing minimize the opportunity for undesirable blooming or crazing formation in the cured reaction product. In addition, the inventive photocurable compositions are capable of curing through larger gaps between substrate surfaces than conventional cyanoacrylates, or known photocurable cyanoacrylates. Moreover, as set forth in greater detail below, in one aspect of the invention the photocurable compositions include a non-cyanoacrylate-based radical curable component. The precense of such a component in the inventive compositions allows for the generation of copolymers and reaction products, which would not otherwise be accesible through typical anionic polymerization mechsanisms—the predominant polymerization of cyanoacrylates.
In another aspect of the present invention, there is provided a method of polymerizing a ph
Bauman Steven C.
Berman Susan
Loctite (R&D) Limited
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