Polyurethane paint (code S) is polyurethane paint, which contains a considerable number of urethane bonds in its structure. Unlike acrylic acid, the resin of polyurethane paint is polymerized from acrylic monomers; although its molecular structure contains repeating chains of carbamate, it is not polymerized from carbamate monomers , but It is formed by reacting polyisocyanate with active hydrogen-containing compounds. There are many types and varieties , which can be divided into:
(1) Hydroxy-cured two-component polyurethane coating
This type of coating has better comprehensive performance in polyurethane coatings, the largest variety, large output, and the most widely used. It mainly uses isocyanate group-containing adducts and prepolymers as component A, and hydroxyl-containing polyester , polyether, acrylic resin or epoxy resin as component B, which are mixed in proportion when used. Polyester type and hydroxyacrylic resin have good weather resistance; polyether type has poor weather resistance, but better water and alkali resistance; epoxy type has good corrosion resistance and poor weather resistance. A series of coatings with different , which are suitable for coating various materials such as metal, wood, cement, plastic, rubber, leather, fabric, paper, etc., and can be applied to Anti-corrosion coating for aircraft, cars, railway vehicles, machine tools, household appliances , light industrial products, wooden furniture and petrochemical equipment pipelines, buildings, offshore oil production units and marine structures.
(2) Catalytic curing two-component polyurethane coating
The isocyanate prepolymer is used as the A component, and the catalyst is the B component, and it is prepared according to the proportion when used. Its curing agent mechanism is the same as that of moisture curing polyurethane. The coating dries quickly, has good corrosion resistance, strong adhesion, wear resistance, water resistance and good gloss. Commonly used for wood and metal finish and concrete surface coating, also used for petrochemical anti-corrosion coating.
(3) Moisture-curing one-component polyurethane coatings
It is made by the reaction of hydroxyl-containing polyester, polyether compound and diisocyanate in the case of an appropriate excess of isocyanoamino groups, and is cured into a film by the action of active isocyanate groups contained in its molecules and moisture in the air . The coating film has high cross-linking density, wear resistance, oil resistance, water resistance, chemical corrosion resistance, pollution resistance , good adhesion and flexibility, and is easy to apply in a humid environment. It is used as a high-performance anti-corrosion coating for buildings, underground , and is also often used as an internal coating for oil pipes and oil tanks.
(4) Closed one-component polyurethane coating
This type of coating is to use a blocking agent to block , and mix it with polyhydroxyl components to form a one-component coating. During use, it is baked to unblock the blocking agent, regenerate the -NCO group, and react with the polyhydroxy component to form a film. The sealing agent evaporates during baking and does not remain in the coating film, but pollutes the air. This kind of paint has good stability, low toxicity, and excellent insulation of the coating film. It is specially used as electrical insulation paint for enameled wires.
Polyurethane coatings have a variety of excellent properties, the coating film is hard, flexible, wear-resistant, bright and full, strong adhesion oil resistance, acid resistance, solvent resistance, chemical corrosion resistance, good electrical insulation performance, low temperature and room temperature curing, and protective And decoration, the elasticity of the paint film can adjust its composition ratio according to needs. Polyurethane coatings can be made into solvent-based, liquid solvent-free, powder, water-based, one-component, two-component and other forms to meet different needs. Because of this, polyurethane paint is widely used in national defense, infrastructure, chemical anticorrosion , vehicles, aircraft, wood, electrical insulation, etc., and new varieties continue to emerge. It is more expensive and is generally used in places with high performance requirements. Some polyurethane paints contain quite a lot of free isocyanate, inhalation is harmful to human health, storage must be airtight, and ventilation needs to be strengthened during construction. The cured polyurethane coating does not contain free isocyanate groups and is safe and harmless to the human body. Polyurethane coatings are highly reactive coatings, sensitive to the environment, and have strict requirements for construction. The ratio of ingredients, curing period, and construction intervals must be implemented in accordance with regulations.
