Coating general knowledge: polyurethane coating preparation

Core tip: polyurethane coating preparation Polyurethane coating mainly includes the following categories: 1 Urethane oil Urethane oil is a kind of paint which first exchanges the dry oil with polyol, then reacts with diisocyanate, and then dry in the air with the unsaturated double bond of oil and fat by adding some drying agents such as cobalt, lead and manganese Generally, the ratio of NCO / Oh is between 0.9 and 1.0 If it is too high, the finished product will be unstable If it is too low, the residual hydroxyl will be more and the water resistance will be poor Compared with alkyd resin, urethane oil has the advantages of fast drying, high hardness, good wear resistance, water resistance and weak alkaline resistance This is mainly because hydrogen bond can be formed between urethane bonds, so the conjunctiva is fast and hard But the ester bond of alkyd can not form Shenyang steel structure fireproof coating construction expert punde Building Fire Engineering Co., Ltd Recommended introduction: since its establishment, Shenyang punde Construction Fire Engineering Co., Ltd has cultivated a group of professional construction teams with excellent equipment, rich experience and serious responsibility with advanced and scientific management methods and strict engineering quality assurance and after-sales service system It has undertaken a number of fire system installation projects, which has been praised by customers Every idea and special requirement of you will be fully considered by us and fully realized in the construction technology, which will become the cornerstone of our successful long-term development We are looking forward to your invitation, to provide you with quality services and high-quality technical support! All construction coatings have passed ISO9001 Home of paint news: polyurethane paint preparation polyurethane paint mainly has the following categories: first, polyurethane oil ammonia ester oil is the first dry oil and polyols for ester exchange, and then with diisocyanate reaction, add cobalt, lead, manganese and other drying agents, oil unsaturated double bond in the air dry paint Generally, the ratio of NCO / Oh is between 0.9 and 1.0 If it is too high, the finished product will be unstable If it is too low, the residual hydroxyl will be more and the water resistance will be poor Compared with alkyd resin, urethane oil has the advantages of fast drying, high hardness, good wear resistance, water resistance and weak alkaline resistance This is mainly because hydrogen bond can be formed between urethane bonds, so the conjunctiva is fast and hard However, the ester bond of alkyd can not form hydrogen bond, and the cohesion between molecules is low The performance of urethane paint film is not as good as that of two-component or one component moisture curing polyurethane paint containing NCO group The principle of moisture curing polyurethane paint is to use water in the air and prepolymer containing isocyanate group to react to form film, which is characterized by convenient use, curable at room temperature, and better wear resistance than two-component polyurethane paint There are two preparation methods: 1 Using polyester or polyether with larger molecular weight to react with diisocyanate, NCO / Oh ≥ 2, i.e using isocyanate to seal the original complex macromolecule 2 Reaction of diisocyanate with binary or ternary polyether with lower molecular weight, NCO / Oh < 2, generally between 1.2 and 1.8 That is to say, because NCO / Oh is less than 2, the molecular weight of prepolymer is increased when isocyanate is used to seal the end, and the urethane bond is embedded in the polyether chain segment to improve the mechanical strength and ensure rapid drying 3、 The film-forming substance of closed polyurethane paint is similar to that of two-component polyurethane paint, which is composed of polyisocyanate and polyhydroxy resin The difference is that the polyisocyanate has been sealed by phenol or other monofunctional substances containing active hydrogen atoms, so the two parts can be packed together without reaction, and become a single component coating, with very good storage stability Phenol sealing: caprolactam sealing: malonate sealing: when heated, the ammonia ester bond is cracked to form isocyanate, and then react with the polyhydroxy resin to form a film Therefore, the film formation of polyurethane paint is to use the difference of thermal stability of different structures of urethane bond, and replace the weaker urethane bond with a more stable urethane bond The isocyanate sealed with phenol is used for wire baking, and the curing temperature is above 175 ℃ Table 7.2 cracking temperature of HDI blocked urethane compounds cracking temperature of sealer, ℃ cracking temperature of sealer, ℃ caprolactam 160 catechol 160 phenol 160 diethyl malonate 130-140 m-nitrophenol 130 acetylacetone 140-150 p-chlorophenol 130 acetylethyl acetate 140-150 cracking temperature is affected by the following factors: paint home is focused on paint, diatom mud, Paint coating, coating process, news information and coating of fire retardant coating, diatom mud, paint coating, coating process, decoration knowledge and decoration effect drawing of fire retardant coating,