Лако-красочные материалы — производство

Lignin is a phenolic polymer that is one of the main polymeric constituents of wood formula (1). It is generally produced in great quantities as waste from paper pulp mills. It is composed of repeating phenylpropane units. Considerable research has been carried out on lignin adhesives and binders. While for certain applications, such as binders for nontarred rough rural roads, lignin derivatives have been used for many years, in the main area of potential application—wood adhesives—industrial use has been lagging. A variety of effective lignin adhesive formulations exist and have already been reviewed extensively [3], some of them having been used for some length of time in some particleboard or plywood mills. Not all these formulations are used today because all of them always come up against two broad problems: the formulation tends to be corrosive or hard on equip­ment in the plant, or the lignin in the formulation tends to noticeably slow down panel pressing time, with consequent loss of mill productivity. In North America there are now encouraging indications that premethylolated lignin (prereacted with formaldehyde) can be added in place of up to 20 to 30% of synthetic phenolic resins for plywood without lengthening panel pressing times, and a few mills already appear to have been using such a system for some time [4]. Recent claims that industrial use of wood adhesive formulations containing up to 50% lignin has occurred for some years but has now been discontinued purely on economical grounds have proven to be true and reliable [7]. Considering their very limited application, the reader is referred to more extensive reviews on this subject [3,6].