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Effect of organotin catalysts on the synthesis of polyester resins for powder coatings
Edit:Nantong Yutai Chemical Products Co., Ltd.   UpDate:2019-10-11

Properties of monobutyltin oxide: white powder, insoluble in water and most organic solvents, soluble in strong bases and inorganic acids.

German concentration (g / L, 25oC): 1.46;

Organotin catalyst:

The organotin compound is a metal organic compound formed by direct bonding of tin and carbon. There are two types of alkyl tin compounds and aromatic compounds. 10-20% of the tin production is used to synthesize organotin compounds. Organotin catalysts are commonly used in the production of polyurethanes and other products, especially in the polyurethane foam, coatings, elastomers, adhesives, resins and other industries.

1. Common organotin catalysts:

1) Dibutyltin dilaurate

A strong gel catalyst for elastomers, adhesives, sealants, coatings, rigid foams, molded foams, RIM, etc.

Dibutyltin dilaurate is also a heat stabilizer, mainly used in the processing of PVC soft-transparent products, silicone rubber catalysts, polyacrylamide and photothermal stabilizers for phenolic resins.

2) Stannous octoate

A catalyst for the production of basic catalysts for polyurethane foams, room temperature curing silicone rubbers, polyurethane rubbers, polyurethane coatings.

The chemical properties are extremely unstable and highly susceptible to oxidation. Stannous octoate is an abbreviation for 2:1 ethyl stannous hexanoate. 2-Ethyl acid is reacted with sodium hydroxide to form 2-ethyl B. Sodium 1 is then prepared by metathesis reaction with stannous chloride in an inert solvent, and a small amount of antioxidant -264 is added to the reaction pot to increase the tin content and stability of 2-ethylhexanoic acid.

Stannous octoate is soluble in polyols and most organic solvents, insoluble in alcohols and water. Stannous octoate can be stored for 12 months, but must be sealed and stored in a dry place. Stannous octoate is non-toxic and corrosive and can be used in the manufacture of medical supplies.

Powder coatings usually use polyester resin as the main raw material, and the performance of the polyester has a great influence on the coating. The polyester resin is formed by heating and condensation of a dibasic acid and a glycol. The properties of the polyester mainly depend on the molecular weight of the polyester resin and the molecular weight distribution. The polyester resin synthesized by neopentyl glycol has the characteristics of good weather resistance and high film strength, and is mainly used as a high-grade baking varnish and a self-drying varnish. The polyester resin synthesized by ethylene glycol has good abrasion resistance and dimensional stability, and is widely used in the fields of fibers and engineering plastics. Due to the neopentyl structure in the neopentyl glycol molecule, it plays a protective role in the molecular chain of the polyester resin, so that the powder coating prepared from such a resin has excellent stability and fluidity. The synthesis of polyester can control the reaction rate by adding a catalyst, thereby controlling the molecular weight and molecular weight distribution of the polyester. During the reaction, the exothermic reaction of the reaction will lead to the loss of the polyol, the reaction is incomplete, and the diol and the binary are regulated. The ratio of acid, the use of a step-wise temperature rise process, and the selection of specific catalysts are also important ways to control the progress of the reaction. There are many types of catalysts used in the esterification reaction, such as tin, lanthanide and titanium. Conventional polyester resin synthesis processes usually use an organotin compound as an esterification catalyst. The organotin compound is directly combined with carbon and tin to form a metal organic compound. As a catalyst, the side reaction is small, the purity and quality of the product are not affected, the catalytic effect is good, and the organotin catalyst has thermal stability and non-corrosiveness. At the end of the reaction, there is no separation, no post-treatment is required, production is convenient, and the process cycle can be greatly shortened. Organotin catalysts are mainly organotin compounds such as monobutyltin and dibutyltin. Among them, monobutyltin is the most widely used traditional high-efficiency organotin catalyst. In this paper, five organotin catalysts were used to catalyze the synthesis of two polyester resins. The catalytic properties of the five catalysts and the effects on the polyester resins were investigated. The catalytic rates of the same catalysts in the synthesis of the two polyesters were compared.