Methods for improving the water-whitening resistance of pressure sensitive adhesives

This article is related to pressure-sensitive adhesives based on aqueous emulsion and methods of preparing this adhesive. Most names of pressure-sensitive adhesives are in improved water– White Resistance. These pressure-sensitive adhesives are particularly suitable for applications where a pressure-sensitive adhesive is required to maintain adhesion between the substrate and the surface material when subjected to hot water spray or dipping. Hot water adhesion is required in applications such as bottle labeling, where bottles are subjected to hot water spray during washing operations.

In general, In a transparent surface or substrate pressure-sensitive adhesive contact with water or high humidity of 5 degrees, water resistance to whitening is desired. These include labels on the sides of trucks, signs, and bottles. The prior art discloses a method for providing a water-resistant whitening latex emulsion for a pressure-sensitive adhesive. Us Patent 5,286,843 discloses a method for improving the water-resistant whitening of a pressure-sensitive adhesive containing a water-containing latex emulsion and a water-soluble ionized adhesive by removing water-soluble ions and adjusting the pH to at least approximately 6. The patent discloses that water-soluble ions can be removed by a number of techniques, including centrifugation, dialysis, precipitation, and deionization with ion exchange resins.

The preferred method of removing water-soluble ionizers is to contact the aqueous latex emulsion, a prepared pressure-sensitive adhesive containing the aqueous emulsion, or both with the dissociative exchange resin. The international publication W097/11996A1 discloses a method for preparing heat-resistant water-whitening latex emulsions for use in pressure-sensitive adhesive compositions, which consists of copolymerization of a monomer mixture, It consists of at least one alkyl acrylate containing at least 4 carbonic alcohols, at least one polar copolymer, and at least one partially water-soluble copolymer in the presence of at least approximately 7% by weight. Polymerization occurs in the presence of at least one nonionic surfactant containing at least 8 moles of ethylene oxide and at least one anionic surfactant containing up to about 10 moles of ethylene oxide, neutralizing the polymerized product to produce an emulsion with a pH higher than and containing particles with a volume average particle size of up to about 165m in diameter. After polymerization, electrolytes can be added to stabilize the opacity of the film flowing from the emulsion.