What catalyst is used for polyester polyols, and what is used to dissolve polyester polyols

Polyester polyols, organic substances, are usually formed by the condensation (or transesterification) of organic dicarboxylic acids (anhydrides or esters) with polyols (including diols) or by polymerization of lactones with polyols. Dibasic acids include phthalic acid or phthalic anhydride or its esters, adipic acid, halobenzephthalic acid, etc. Polyols include ethylene glycol, propylene glycol, ethylene glycol, trimethylolpropane, pentaerythritol, etc.

Different varieties of polyester polyols due to different types or preparation processes, properties are also different, for polyester polyols more important indicators are hydroxyl number, acid number, moisture, viscosity, molecular weight, density and color. Characteristics and uses of polyester polyols: Polyester polyurethane has high strength and wear resistance due to the fact that it contains more ester groups, amino groups and other polar groups in the molecule.

The production of polyester polyols requires strict monitoring of acid and hydroxyl numbers. and viscosity changes to ensure the production of qualified polyester polyols.

Polyester polyols used in polyurethane adhesives are of high quality, and in addition to molecular weight (hydroxyl number), the acid number is particularly important, as it is a measure of the residual carboxyl group. The terminal carboxyl group reacts with the isocyanate to form an amide and releases carbon dioxide, which not only causes the termination of the chain, but also forms nasty bubbles. This amide group can also react with isocyanates to form an acylurea group.

Residual acids in polyester can also catalyze polyurethane reactions, have adverse effects, and reduce the hydrolytic stability of polyurethane. Therefore, the acid value is generally required to be less than 1mg koh g, and even less than: koh g; However, if the acid number is too low (< koh> the reaction will be too fast to form polyurethane resin, which will affect the operation, and the acid number should be koh g.

The addition of catalyst to the preparation of polyester polyol can shorten the polycondensation reaction time: but the catalyst is not easy to remove, and has an adverse effect on the next polyurethane reaction, and the dosage is not large and has no effect. The inorganic catalysts include zinc acetate and antimony trioxide or zinc acetate and antimony trioxide mixture, etc., with an addition amount of 100 300ppm; Organocatalysts include tetrabutyl titanate, tetraisopropyl titanate, etc., with a dosage of 15 100ppm.

Generally, toluene and ethanol are mixed with solution.

Ether, acetone and other common organic solvents.

Depending on what you want to do, alcohol can be dissolved.

There are several spine catalysts commonly used: antimony (antimony oxide, antimony acetate, antimony glycol); titanium (titanium dioxide, titanate, etc.); germanium (germanium dioxide and metal complexes are missing); tin (stannous chloride and many metal complexes); enzymes, etc.