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
2000-10-17
2003-04-01
Cain, Edward J. (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...
C524S271000, C525S093000
Reexamination Certificate
active
06541553
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to improved high performance pressure sensitive adhesives and protective and decorative strippable adhesive and coating films. More particularly, the invention relates to a novel formulation for forming improved adhesives and such strippable films by curing the formulation by irradiating it with UV light.
BACKGROUND OF THE INVENTION
Protective and decorative strippable adhesive and coating films are well known and are highly useful for application to home and store windows and the windows and panels of automobiles to serve as either a protective or decorative covering or both. This type of film is applied in sheet form, cured, and printed, and it is preferred that it is capable of being wound upon itself without the necessity of a release coating or a release liner.
U.S. Pat. No. 5,286,781 describes a pressure sensitive adhesive composition and tape or sheet made therefrom which is comprised of a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene and a particular polyolefin. Also described therein are previous protective films made with such block copolymers and several other similar polymers.
Formulations based on the above block copolymers are used commercially and have the advantage that they exhibit elastic properties at room temperature. However, they are limited in their susceptibility to high service temperatures, i.e., above about 70° C. At such temperatures, the films weaken cohesively.
Adhesive films based on UV cured epoxidized polydiene polymers are described in U.S. Pat. Nos. 5,776,998 and 5,837,749. While adhesive and coating films made from these materials are highly useful for high performance pressure sensitive adhesives, these formulations do not work very well for strippable coatings. Such films generally have poor tensile properties. They tear or break upon only a small induced elongation. This limits the quality of the strippable coatings and adhesive films because they break too easily and this prevents easy removability. The present invention eliminates this problem.
Furthermore, using this invention, improved high performance pressure sensitive adhesives can be obtained that are more cost effective and convenient to handle for those who have a need for handling a solid adhesive at room temperature such as any typical hot melt adhesive formulator or user. This invention can be handled like a typical hot melt adhesive and later UV cured to get the desired properties. Also, the adhesive can be precoated on a paper or film stock roll and then UV cured in latter operation that is followed by immediate bonding of the substrates. Immediate bonding after cationic UV cure gives higher bond strengths.
SUMMARY OF THE INVENTION
This invention relates to curable strippable adhesive and coating films, and also to improved high performance pressure sensitive adhesives. The adhesive comprises:
(a) from 10 to 90 percent by weight of a crosslinkable epoxidized diene polymer,
(b) from 0 to 70 percent by weight of a diene mono-ol polymer, with the condition that the mono-ol polymer not exceed three times the weight of the epoxidized polymer,
(c) from 5 to 40 weight percent of a block copolymer of a vinyl aromatic hydrocarbon and a diene having, on average, more than one vinyl aromatic hydrocarbon block per molecule, wherein the amount of vinyl aromatic hydrocarbon in the block copolymer is less than 30% by weight, and wherein the block copolymer can be functionalized by grafting onto it from 0.1 to 5% by weight of a carboxylic acid or anhydride, preferably maleic anhydride,
(d) from 0 to 65% percent by weight of a tackifying resin, and
(e) from 0.01 to 3 percent by weight of a photoinitiator.
Formulations can also be made with block copolymers containing 30 to 50 percent by weight of a vinyl aromatic hydrocarbon. In this case, a tackifying resin containing from
—
2_to
—
20, preferably 3 to 10,_percent by weight aromaticity must be used in an amount of 5 to 65, preferably 20 to 40, percent by weight. The use of this type of tackifying resin allows compatible formulations to be made with the block copolymers containing 30 to 50 percent by weight vinyl aromatic hydrocarbon and the crosslinkable epoxidized diene polymer.
The preferred epoxidized diene polymer of the present invention is an epoxidized monohydroxylated block copolymer of at least two conjugated dienes, preferably isoprene and butadiene, wherein the isoprene block substantially contains the epoxidation, the butadiene block is hydrogenated, and the hydroxyl group is attached at the end of the butadiene block. It is preferred that the polydiene mono-ol polymer have a number average or hydroxyl equivalent molecular weight of 2000 to 30,000 and these polymers are preferably hydrogenated polybutadiene with a terminal OH group. The preferred mono-ol polymer, block copolymer, and tackifying resins are hydrogenated.
DETAILED DESCRIPTION OF THE INVENTION
Polymers of this invention containing ethylenic unsaturation can be prepared by polymerizing one or more olefins, particularly diolefins, by themselves or with one or more alkenyl aromatic hydrocarbon monomers. The polymers may, of course, be random, tapered, block or a combination of these, as well as linear, star or radial. In general, when solution anionic techniques are used, polymers of conjugated diolefins, optionally with vinyl aromatic hydrocarbons, are prepared by contacting the monomer or monomers to be polymerized simultaneously or sequentially with an anionic polymerization initiator such as group IA metals, preferably lithium, their alkyls, amides, naphthalides, biphenyls or anthracenyl derivatives.
The vinyl aromatic hydrocarbon/diene block copolymers and the epoxidized polydienes and polydiene monools are synthesized by anionic polymerization of vinyl aromatic and/or conjugated diene hydrocarbons with these lithium initiators. This process is well known as described in U.S. Pat. No. 4,039,593 and U.S. Pat. No. Re. 27,145 which descriptions are incorporated herein by reference. Polymerization commences with a monolithium initiator which builds a living polymer backbone at each lithium site. Typically, such polymerizations are capped by termination with ethylene oxide to provide a terminal hydroxyl group.
Conjugated diolefins which may be polymerized anionically include those conjugated diolefins containing from about 4 to about 24 carbon atoms such as 1,3-butadiene, isoprene, piperylene, methylpentadiene, 2-phenyl-1,3-butadiene, 3,4-dimethyl-1,3-hexadiene, 4,5-diethyl-1,3-octadiene and the like. Isoprene and butadiene are the preferred conjugated diene monomers for use in the present invention because of their low cost and ready availability. Alkenyl (vinyl) aromatic hydrocarbons which may be copolymerized include vinyl aryl compounds such as styrene, various alkyl-substituted styrenes, alkoxy-substituted styrenes, vinyl naphthalene, alkyl-substituted vinyl naphthalenes and the like.
Block copolymers of vinyl aromatic hydrocarbons and conjugated dienes such as used herein are very well known and are described in the aforementioned U.S. Pat. No. 4,039,593 and U.S. Pat. No. Reissue 27,145 among many others. Typically, these polymers contain two vinyl aromatic hydrocarbon blocks, one at each end, and an internal conjugated diene block. For example, the polymer may be styrene-isoprene-styrene or styrene-butadiene-styrene.
The aforementioned commonly used triblock copolymers are not very compatible with the epoxidized diene polymers used in this invention. One way of increasing the compatibility is for the hydrogenated block copolymer to have at least some of the polymer molecules with a hydrogenated diene block on at least one end of the molecule. Another way of increasing the compatibility is to keep the amount of vinyl aromatic hydrocarbon in the block copolymer less than 30% by weight. The compatibility of block copolymers having a vinyl aromatic hydrocarbon content of from 30 to 50 percent by weight can be increased by utilizing from 5 to 65, preferably 20 to 40, percent by weight of a tack
Erickson James Robert
Hansen David Romme
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