Лако-красочные материалы — производство

Outstanding properties such as thermal stability, weathering resi­stance, low temperature flexibility, low surface tension, hydropho — bicity and surface activity of silicone resins and their combinations with other resins made them a commercially important category of binders for high performance coatings. Table 2.9: Typical monomers for silicones Monomer Functionality* Effect in final structure of silicone […]

PUDs are another commercially important type of waterborne polyu­rethane systems. Due to their versatility, stability, high performance, and low VOCs, PUDs are increasingly used as binders for a wide range of coatings and related products. Conventional PUDs are aque­ous secondary dispersions of high MW polyurethanes with a typi­cal particle diameter of 0.1 to 0.2 pm. […]

Earlier we discussed two-component polyurethane systems for sol — ventbased or high-solid systems. In general, any waterborne coating system requires resins and cross-linkers that are water dispersible. To confer water dispersibility, resins and cross-linkers are generally modified with a sufficient degree of hydrophilic groups or struc­tures. When such modified materials are added to water under […]

As discussed earlier, many polyurethane resin systems offered for coatings contain free — NCO groups, which are expected to react with appropriate cross-linkers during the curing reaction after application. Since isocyanates are reactive to water, until the 1990s, it was thoughtdifficult to offer waterborne polyurethane resin systems. While iso­cyanate can react with water at ambient […]

Urethane (meth)acrylates are another class of polyurethane resins mainly used in radiation curable systems. Urethane acrylates are oligomeric urethanes with (meth)acrylate functionality. They are used as components of radiation curable systems, in which coatings are applied and exposed to high energy radiation such as UV light or an electron beam. The free radicals generated during […]

These resins are generally polyurethanes modified by drying-oil fatty acids. These types of resins are essentially urethane modi­fied alkyd resins, and hence are also called urethane alkyds or uralkyds. Like alkyds, urethane alkyds dry by auto-oxidative poly­merization, and their drying rate can be improved by use of con­ventional driers used for alkyds. A reaction scheme […]

Blocked isocyanates are a type of urethane that are made from reaction of polyisocyanates with special active H-compounds that form thermally reversible urethane linkages. When heated above a certain characteristic temperature, called the deblocking tem­perature, blocked isocyanates undergo a reversible reaction with formation of free — NCO groups and an active H-compound. Some examples of […]

A moisture-curable urethane resin is simply a urethane prepolymer with free — NCO groups. Typically made from aromatic isocyanates, the free — NCO group of such a resin, when exposed to the envi­ronment after application, will react with ambient moisture and produce urea linkages between prepolymer chains, resulting in formation of the cured coating (Figure […]

Polyurethane resins and coatings are also offered as one-component (also called single-component, 1-part or 1K) systems. Such systems are typically comprised of polyurethane prepolymers with reactive functional groups. As a single-component system, the functional groups are kept from reacting with any internal or external agents to provide shelf stability. A number of different types of […]

Two-component (also called by such terms as 2K, plural component, two-can, and two-part) polyurethane coatings are among the most popular types, and such coatings are offered in two separate cans that are required to be mixed in specified proportion just prior to their use (Figure 2.63). Since polyols and isocyanates are reactive at ambient temperature, […]