How to Achieve the Environmental Protection Goals of Adhesives
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Technological Innovation to Optimize Adhesive Characteristics
Water - based Transformation: The water - based process of adhesives involves using water as a solvent or dispersion medium to prepare water - based adhesives. Since no organic solvents are used, solvent pollution is fundamentally eliminated. For example, emulsion - type acrylate pressure - sensitive adhesives can replace solvent - type pressure - sensitive adhesives; water - based laminating adhesives have gradually replaced solvent - type laminating adhesives, with advantages such as non - toxicity, non - flammability, no pollution, and safe use. By adding isocyanates or prepolymers to a polyvinyl alcohol (PVA) aqueous solution, a vinyl polyurethane emulsion can be prepared, which can replace urea - formaldehyde adhesives and completely solve the problem of formaldehyde release. However, water - based adhesives have the disadvantages of slow drying speed, poor water resistance, and poor frost resistance. In the future, the solid content should be increased, the drying speed should be accelerated, and cross - linking methods should be used to improve the drying speed and water resistance, thereby expanding their application scope.
Solvent - free Exploration: Solvent - free means that the adhesive contains no solvents. Since no solvents are volatilized into the atmosphere, there is no pollution or harm to the environment. Most epoxy adhesives, anaerobic adhesives, α - cyanoacrylate adhesives, aerobic modified acrylate structural adhesives, solvent - free polyurethane adhesives, and light - curable adhesives belong to the solvent - free type.
Solid - state Practice: The solid - state use of adhesives refers to using them in a solid form, such as hot - melt adhesives, hot - melt pressure - sensitive adhesives, water - soluble powder adhesives, reactive rod - shaped adhesives, and office solid glue sticks. During the coating and bonding processes, these solid - state adhesives do not release volatiles and cause no environmental pollution at all. Powdery adhesives are more popular abroad due to their stable performance and no environmental pollution.
Low - toxicity Improvement: Although solvent - type adhesives have fast drying speed and good water resistance, they cause significant pollution and toxicity. Currently, they cannot be completely replaced by water - based adhesives. However, low - or non - toxic solvents such as cyclohexane, ethyl acetate, methyl ethyl ketone, 1,1 - dichloroethane, and dimethyl carbonate can be used to prepare non - or low - toxic solvent - type adhesives.
Process Upgrading and Implementing Clean Production
Adopting advanced clean production processes can achieve the unity of economic and environmental benefits and produce environmentally friendly adhesives.
Abandon the use of methyl methacrylate with a strong odor and use high - boiling - point monomers to produce modified acrylate fast - curing structural adhesives.
Do not use toxic raw materials such as formaldehyde, chlorinated solvents, aromatic hydrocarbon solvents, and fillers containing toxic heavy metals in the formulation and production process of adhesives.
Carry out production under non - toxic and harmless conditions. For example, use paraformaldehyde instead of formaldehyde solution to produce modified amine curing agents.
Add formaldehyde scavengers such as starch, polyvinyl alcohol, and melamine, which can significantly reduce the free formaldehyde content in urea - formaldehyde resin adhesives. Among them, oxidized starch is more effective than ordinary starch and can reduce the free formaldehyde content to less than 0.1%.
