Patent GB-1523440-A (GB)
Title: Anaerobic pressure sensitiveadhesive sheets and tapes
IPC: C09J7/10
Filed: 1975-10-07
Abstract: 1523440 Pressure sensitive curable adhesive coated sheets and tapes LOCTITE CORP 7 Oct 1975 [7 Oct 1974] 40976/75 Heading B2E [Also in Division B5] An anaerobically-curing pressure-sensitive adhesive sheet or tape comprises (a) a first release coating on a self-supporting release liner; (b) a transferable pressure-sensitive adhesive layer comprising a thermoplastic polymer system (e.g. polyvinylchloride and/or a polyurethane, or a polyester alone or with polyvinylchloride), an anaerobically curable resin system (e.g. at least one monomer selected from the reaction product of 2 mols, hydroxypropyl methacrylate with methylene bis - phenyl - 4, 4' - diisocyanate; hydroxypropyl methacrylate - capped reaction product of a 1:1 adduct of toluene diisocyanate and hydrogenated 2, 2 - bis(4 - hydroxyphenyl) propane; and mixtures thereof), and a catalyst system for the anaerobic resin causing cure thereof by activation of a peroxy compound initiator in the system in the presence of an accelerator which is included in the system and on substantial exclusion of oxygen, said pressure-sensitive adhesive layer being in contact with the first release coating, and in a solvent-free state having a static shear strength of at least 2 minutes at a 250 gm. load per 0.25 sq. inch and a 180 peel value of at least 0.5 1b. per inch prior to its anaerobic curing; (c) a second release coating on a self-supporting liner, which coating is in contact with the opposed surface of the transferable pressure-sensitive adhesive layer, the bond strength of the first release coating to the adhesive layer being less than the cohesive strength of the adhesive layer and exceeding the bond strength of the second release layer to the adhesive layer so as to permit the adhesive layer to be preferentially separated from the second release coating for application and bonding to a substrate prior to separation of the adhesive layer from the first release coating without cohesive failure of the adhesive layer. The first and second release coatings may be on opposed sides of a common release liner to allow forming the sheet or tape into a roll, or may be provided on two separate release liners. The adhesive layer may be in the form of two adhesive layers separated at least in part by an interlayer (e.g. of optionally perforated polyethylene) to support the adhesive layer and improve its flexural strength after curing. The first and second release coatings may be in contact (on the adhesive layer face or the release liner face) with a polymeric barrier layer (e.g. polyethylene) preventing diffusion of an organo-nitrogen compound comprising the accelerator in the adhesive layer. The surface of one barrier layer may be smooth and the other matt-finished to provide the preferential separation properties of the two release layers from the adhesive. The adhesive system may include a tackifying resin (e.g. rosin and its derivatives, terpins, low molecular weight polyacrylates). The accelerator may include a micro-encapsulated transition metal compound (e.g. copper salts, as an initiator for the catalyst system, the micro-capsules rupturing on application of pressure to release the initiator and activate the catalyst system to cause curing of the resin system.