Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Adhesive outermost layer
Reexamination Certificate
2001-05-08
2003-09-30
Seidleck, James J. (Department: 1711)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Adhesive outermost layer
C428S343000, C428S345000, C602S054000, C602S056000, C602S057000, C602S058000
Reexamination Certificate
active
06627309
ABSTRACT:
TECHNICAL FIELD
This invention relates to a method of curing a polymerizable material using a light-stable isomer of a 2,4,5-triarylimidazolyl dimer. Applying a solvent or friction activates the dimer.
BACKGROUND
Photosensitive bilophine isomers are known. For example, U.S. Pat. Nos. 3,479,185 and 3,549,367 describe photopolymerizable compositions that include a 2,4,5-triphenylimidazolyl dimer consisting of two lophine radicals bound together by a single covalent bond. Upon irradiation, the dimer is dissociated into free radicals that react with a free radical-producing agent included in the composition. These materials are useful in image-forming systems. U.S. Pat. No. 4,459,349 describes a photopolymerizable resin composition that is highly sensitive to ultraviolet rays yet is thermally stable. The photopolymerization initiation system includes a 2-polycyclic aryl-4,5-diphenylimidazolyl dimer. British Patent No. 997,396 describes 2,4,5-triphenylimidazole dimers that change color upon exposure to light. British Patent No. 1,047,569 describes light-sensitive compositions including a leuco dye and a 2,4,5-triarylimidazolyl radical. The compositions change from colored to clear upon irradiation with ultraviolet light, and are useful in image-forming systems. Photoimaging compositions containing leuco dyes and triarylimidazoles are also described in U.S. Pat. No. 3,445,234 (2,2′,4,4′,5,5′-hexaarylbiimidazole) and in EP 0 024 629 B1 (2,4,5-triphenylimidazolyl dimer).
Polyarylimidazoles are described in U.S. Pat. Nos. 3,707,475 and 3,772,441 to inhibit inflammation in mammals. Triphenylimidazolyl compositions are included in Example X of '475 and in Example V of '441.
Various methods of detackification are known. U.S. Pat. No. 3,861,950 describes a process of detackifying rubber using a substituted phenyl group having a sulfenyl chloride substituent. U.S. Pat. No. 4,857,372 describes a graphic composition that includes a thermally detackifiable adhesive premask tape. A diaziridine compound is described to provide initial crosslinking in this premask tape, while a melamine compound extensively crosslinks the tape to detackify it during a later exposure to elevated temperatures, such as encountered during an automotive paint baking cycle. U.S. Pat. No. 4,202,696 describes a method of removing surface tack from a cured resin such as used in photorelief-type printing plates by treating the resin with specific carbonyl compounds such as benzophenones and anthraquinones. The surface layer of the cured resin is impregnated with the compound, then the impregnated layer is irradiated with specific actinic rays. U.S. Pat. No. 4,286,047 describes an adhesive system containing an oxirane ring-bearing component and a photoinitiator. When this pressure-sensitive adhesive is exposed to ultraviolet light, the adhesion is reduced.
U.S. Pat. No. 4,024,312 discloses a film backed, normally tacky and pressure-sensitive adhesive tape that is highly extensible and highly elastic. The tape can be easily removed from a surface to which it has been applied by stretching it lengthwise in a direction substantially parallel to the plane of the surface. The film backing is formed from elastomeric and thermoplastic block copolymers. A preferred use for this tape is in a bandage. U.S. Pat. No. 5,989,708 describes an adhesive tape that is removable from a substrate by stretching it in a direction substantially parallel to the surface of the substrate. The tape backing is described as highly extensible and substantially inelastic.
DISCLOSURE OF INVENTION
Briefly, the present invention provides a method of curing a polymerizable material containing ethylenically unsaturated bonds at a temperature of 60° C. or less, comprising the steps of (a) providing a curative comprising an effective amount of a light-stable isomer of a 2,4,5-triarylimidazolyl dimer, (b) activating said curative by application of an activator selected from the group consisting of solvent and friction, and (c) combining the activated curative with the polymerizable material.
In another aspect, the present invention provides a method of making an article comprising an adhesive having a detackified surface comprising the step of applying a curative to an adhesive surface of an article comprising an adhesive, said curative comprising a component selected from the group consisting of 2,4,5-triarylimidazole, bilophine and lophine radicals.
In another aspect, the present invention provides a two-part adhesive comprising a first part which comprises a light-stable isomer of a 2,4,5-triarylimidazolyl dimer and a second part which comprises a secondary or tertiary amine and a polymerizable material containing ethylenically unsaturated bonds.
The present invention also provides a detackifying solution comprising a light-stable bilophine, a secondary or tertiary amine, and a suitable solvent.
In still other aspects, the present invention provides articles that include an adhesive having a detackified surface, articles that include an adhesive removable from a substrate, tape articles, and adhesive bandages.
As used herein:
“aryl” means a C6-C20 aromatic group, which may be substituted; and
“substituted” means having substituents that do not interfere with the desired product, e.g., substituents can be alkyl, alkoxy, aryl, phenyl, halo (F, Cl, Br, I), cyano, nitro, etc.
It is an advantage of the present invention to provide adhesive material with various properties. For example, an adhesive having different tackiness on each major side, while the cohesive properties of the bulk or interior of the adhesive remains substantially unmodified. This is useful in matching peel and/or shear adhesion release properties when bonding two different materials.
In addition, one major surface of an adhesive can be crosslinked to a greater extent than the opposing major surface. For example, an adhesive tape can be made wherein one major surface of the adhesive remains a pressure-sensitive adhesive while the opposing major surface of the adhesive is extensively cured with the method of the present invention to provide an essentially non-tacky integral backing for the pressure-sensitive adhesive.
The present invention is useful in a shear-debonding adhesive wherein one major surface of the adhesive has different adhesive properties, such as shear, peel, and tack, than the opposing surface of the adhesive. Such an adhesive is useful for applying graphics to surfaces such as those found on trucks, railway cars, buildings, and billboards.
Additionally, the present invention provides an adhesive packaging method which may be combined with an adhesive delivery method and/or use method. For example, an outer surface of a glue stick or an outer surface of a bulk adhesive mass can be detackified without detrimentally affecting the eventual intended use of the adhesive. The invention provides a thin, thermoplastic shell that is not tacky, and which will mix into the adhesive during application and need not interfere with the complete consumption of the product.
DETAILED DESCRIPTION
The present invention provides a method of curing a polymerizable material containing ethylenically unsaturated bonds at a temperature of 60° C. or less. In this method, a curative comprising an effective amount of a light-stable isomer of a 2,4,5-triarylimidazolyl dimer is provided and activated by applying an activator selected from the group consisting of solvent and friction. Then the polymerizable material is combined with the activated curative.
The curative is a light-stable isomer of a 2,4,5-triarylimidazolyl dimer. A preferred light-stable isomer is 2,2′,4,4′,5,5′-hexaphenyl-4,4′-biimidazole, also termed bilophine, which has the following structure:
Non-light-stable isomers include 2,2′,4,4′,5,5′-hexaphenyl-1,1′-biimidazole, 2,2′,4,4′,5,5′-hexaphenyl-1,2′-biimidazole, 2,2′,4,4′,5,5′-hexaphenyl-1,4′-biimidazole, 2,2′,4,4′,5,5′-hexaphenyl-2,2′-biimidaz
Landgrebe Kevin D.
Perry Dale C.
Stebbings William L.
3M Innovative Properties Company
Dahl Philip Y.
Harts Dean M.
Ribar Travis B
Seidleck James J.
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