Лако-красочные материалы — производство

Although particleboard and plywood are the major users of UF adhesives, two other applications, although consuming much lower proportions of these resins, are also worthy of note. The first is in the furniture and joinery industry, including the manufacture of hollow-core doors. While in the latter application thermosetting resins with character­istics and glue mixes similar to those for plywood are used, often (but not always) cured by radio frequency, the former can be simpler resins of higher urea/formaldehyde molar ratio to which cold setting capability and different pot lives are given by a variety of hardener types; in these, hardeners formed by an acid plus a salt are the norm. The second applica­tion of note is in foundry applications as sand core binders. In this application UF resins compete with phenolic and furanic resins. In general, however, the resins used for the hot — box process are UF resins modified with 20 to 50% furfuryl alcohol to obtain a UF — furanic resin copolymer, and phenol-formaldehyde resins modified with urea. Small amounts of paraffin wax and corn flour are often added to facilitate mixing of the resin with the sand (generally between 1 and 2.5% resin on sand).