What Are Water-Based Neoprene Adhesives?

Water-based chloroprene latex uses water as the dispersion medium and is produced directly through emulsion polymerisation of the monomer chloroprene in the presence of emulsifiers, persulphate initiators, and/or sulphur-containing compounds. It combines the advantages of both chloroprene rubber (see solvent-based chloroprene rubber) and water-based adhesives.

Composition of Water-Based Neoprene Adhesives

Water-based neoprene-type adhesives primarily consist of neoprene latex, metal oxides (vulcanising agents), antioxidants, stabilisers, fillers, tackifiers, vulcanisation accelerators, and thickeners. Depending on the emulsifiers, initiators, regulators (including sulphur-containing compounds), terminators, auxiliary monomers, and polymerisation conditions used, varieties with different properties and applications can be produced.

Emulsifiers

Commonly used emulsifiers are anionic emulsifiers, while carboxyl-modified chloroprene latex is a nonionic latex. It is produced by copolymerising chloroprene with acrylic acid or its derivatives; during polymerisation, nonionic surfactants and polyvinyl alcohol are used to form a stable latex. The surfaces of the latex particles are surrounded by polyvinyl alcohol molecules, which improves mechanical, chemical, and thermal stability, as well as the adhesive’s wetting properties on the substrate and the water resistance of the adhesive film.

Acrylic Acid CAS 79-10-7

Polyvinyl Alcohol（PVA) CAS 9002-89-5

Compounding Agents

The basic principles of water-based neoprene latex adhesives are the same as those of solvent-based neoprene adhesives. If zinc oxide is used as a vulcanising agent, lead oxide serves as an acid scavenger. The primary role of lead oxide is to neutralise the hydrochloric acid generated in the latex; it also acts as a vulcanising agent, causing the adhesive film to undergo slow cross-linking at room temperature.

Antioxidant D can be used as an antioxidant; if contamination is a concern, antioxidants such as 264 or 2246 may be used at a dosage of 1–2 parts.

Commonly used fillers include kaolin and calcium carbonate. Fillers increase the solid content of the latex adhesive, adjust its flow properties to facilitate application, enhance the tensile strength of the adhesive film at a given elongation, improve solvent resistance, and reduce the cost of the adhesive.

Viscosity-increasing agents refer to various resins that increase the tack of the adhesive film. They should be selected based on the intended application. Factors such as colour, flexibility, tack retention time, bonding strength, and cost should be considered; these agents may be used alone or in combination with two or more resins. Commonly used resins include terpenes, terpene-phenol-formaldehyde resins, phenol-formaldehyde resins, coumarone resins, and resorcinol-formaldehyde resins.

Zinc oxide CAS 1314-13-2

Butylated Hydroxytoluene (T501) CAS 128-37-0

Bisphenol a Diglycidyl Ether Resin(E-20) CAS 25068-38-6

Characteristics of Water-Based Neoprene Latex Adhesives

Water-based neoprene latex adhesives combine the properties of solvent-based neoprene adhesives with advantages that the latter do not possess. Their advantages and disadvantages are as follows:

① Good film-forming properties; the adhesive film is flexible and resistant to impact and vibration; 

② High cohesive strength; high bonding strength to polar materials; 

③ Good resistance to ozone, oxidation, oil, flame, and weathering; 

④ Easy and safe to use; suitable for wet bonding; low cost; 

⑤ Non-toxic and environmentally friendly, and poses no health hazards; 

⑥ Non-flammable, with no fire hazard or risk of explosion; 

⑦ Slow drying speed, poor initial tack, and short open time; 

⑧ Prone to freezing, with poor freeze resistance; 

⑨ Poor storage stability, prone to discolouration, and releases hydrogen chloride during long-term storage.