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Publication Date: 2017-Jan-13
Document File: 7 page(s) / 105K

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This disclosure describes compositions which include a radiation-crosslinked elastomer, a tackifying resin, and a metal rosinate. Such compositions are useful, for example, as pressure-sensitive adhesives (PSAs) and tape articles made therefrom. The PSAs and tape articles may further include filaments. The tape articles can have a variety of different uses (e.g., packaging tape such as box sealing and strapping tape, decorative tape, medical tape, and indicator tape). Such tapes including these compositions may be cleanly removable from a surface (including stainless steel, general purpose polystyrene, and high impact polystyrene surfaces) after exposure to a temperature of at least 80 ˚C for at least 48 hours. As a result tapes made with the compositions described herein can be useful in tapes for the temporary holding and shipping of goods, such as appliances. In some cases, the tape is applied to a surface of an appliance, automobile, or electronic component. In other cases, the surface comprises at least one of glass, stainless steel, a painted surface, or polystyrene. It has been found that the presence of metal rosinate unexpectedly permits clean removal of the tape from a surface of various substrates. This indicates the cohesive (internal) strength of the overall tape construction is greater than the adhesive strength between the tape and the substrate. Such cohesive strength is indicative of good bonding between materials in the tape construction. Comparable compositions including radiation-crosslinked elastomer and hydrocarbon tackifier but lacking metal rosinate are not cleanly removable under the same conditions. Increasing the amount of hydrocarbon tackifier to provide an even higher amount of tackifier in the composition does not improve the clean removal performance in the absence of metal rosinate. It has been unexpectedly found that it is the zinc rosinate and not the crosslinker that enhances the clean removal property.

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This disclosure describes compositions which include a radiation-crosslinked elastomer and a

metal rosinate. Such compositions are useful, for example, as pressure-sensitive adhesives (PSAs). 5 Materials that have been found to function well as PSAs are polymers designed and formulated to exhibit

the requisite viscoelastic properties resulting in a desired balance of tack, peel adhesion, and shear

holding power.

While PSAs are desirably cleanly removable from a substrate, clean removability can be

challenging, particularly after aging at elevated temperatures and high relative humidity. A lack of clean 10 removability can be indicative of poor cohesive strength in the PSA composition and/or poor bonding of

the PSA to a polymeric film backing or other components (e.g., filaments) in a PSA tape. Clean

removability may be particularly important in applications where items are intended to be temporarily

held together by the tape, for example, in the holding or shipping of goods such as appliances.

The composition according to the present disclosure typically and unexpectedly provides superior clean-15 removal performance over other comparable pressure sensitive adhesive compositions that do not contain

the metal rosinate. A metal rosinate is sometimes referred to in the art as a metal resinate. The terms are

considered interchangeable. In other adhesive compositions such as the natural rubber- or thermoplastic

elastomer-based adhesive compositions metal rosinates have been included to serve as tackifiers or as

accelerators for phenolic curatives. See for example U.S. Pat. Nos. 3,716,503 (Johnston) 3,912,709 20 (Gould), 3,932,329 (Lakshmanan), 5,385,783 (Patel et al.), 5,439,963 (Korpman), 6,187,127 (Bolitsky et

al.); and Canadian Patent 1,285,276.

Compositions according to the present disclosure include a hydrocarbon elastomer which may be

radiation-crosslinked. Such elastomers typically include carbon-carbon double bonds. Examples of useful

unsaturated elastomers include natural rubber, synthetic polyisoprene, polybutadiene, styrene/butadiene 25 rubber (SBR), butyl rubber, ethylene-propylene-diene monomer rubber, and block copolymers in which

one of the blocks is a block of one of the above elastomers, such as styrene-isoprene-styrene, styrene-

butadiene-styrene, styrene-ethylene-butylene-styrene triblock or styrene-isoprene, styrene-butadiene,

styrene-ethylene-butylene starblock polymers. Combinations of two or more of these elastomers may be

present in the composition. In one variation, the elastomer comprises at least one of natural rubber or a 30 block copolymer of styrene with isoprene or butadiene. In another variation, the elastomer comprises

natural rubber and a star block copolymer of styrene and isoprene. In yet another variation, the elastomer

comprises a styrene-isoproprene-styrene block copolymer.

The composition includes at least about 20 percent by weight...