What are the production processes of polyester polyols
1、 Conventional melt condensation method
Feeding: Dicarboxylic acid and polyol are fed into the reaction vessel at once, with an appropriate excess of alcohol;
Heating esterification: esterification reaction occurs at 140-200 ℃, generating water and continuously evaporating it;
1、 Conventional melt condensation method
Feeding: Dicarboxylic acid and polyol are fed into the reaction vessel at once, with an appropriate excess of alcohol;
Heating esterification: esterification reaction occurs at 140-200 ℃, generating water and continuously evaporating it;
Vacuum condensation: In the later stage, high vacuum is applied (above -0.095MPa, temperature 220-240 ℃) to remove excess small molecule alcohols and increase the degree of polymerization;
Post processing: cooling down, adding catalysts and antioxidants, testing for hydroxyl and acid values, filtering out the material after passing.
Advantages: No need for solvents, low production cost; Disadvantages: Long term reaction at high temperatures, resulting in slightly darker product color. Most aliphatic and aromatic polyester polyols use this process.
2、 Solvent azeotropic dehydration method
Adding toluene and xylene as water carrying agents, the water and solvent generated by the reaction are azeotropically carried out of the system. The reaction temperature can be controlled at 160-180 ℃, and the reaction conditions are mild. Remove the solvent later.
Advantages: Low reaction temperature, light color of finished products, and fewer by-products;
Disadvantage: Solvent recovery increases costs, and is now less commonly used in large-scale production lines. It is mostly used for high-end polyurethane adhesive specific polyester polyols.
3、 Ester exchange method
The raw material uses small molecule diesters (such as dimethyl adipate) to undergo ester exchange with diols, and methanol is distilled to gradually expand the chain to obtain polyester polyols.
Applicable scenarios: Some special branched polyester polyols, or recycled PET bottle flakes are degraded to prepare regenerated polyester polyols. The use of waste PET for depolymerization and exchange with diols belongs to a cyclic process.
4、 Continuous production process
Different from intermittent kettle reactions, the materials are sequentially passed through esterification reactors, thin film evaporation vacuum condensation units, and continuously fed and discharged.
Advantages: Good batch stability of the product, small fluctuations in viscosity and hydroxyl value, and lower energy consumption; The equipment investment is huge, and large chemical enterprises choose it.
中文
English
WeChat number：
Home
Product
Wechat
Telephone