The catalysts commonly used in the synthesis of polyurethane its raw materials are tertiary amine catalyst organometallic compound. There are many kinds of tertiary amines organometallic compounds. Considering various factors, only more than 20 kinds of tertiary amines organometallic compounds are commonly used in polyurethane production.
Amine catalysts are commonly used in the production of polyurethane foam, which are mainly divided into the following categories:
Aliphatic amine catalysts include n, n-dimethylcyclohexylamine, bis (2-dimethylaminoethyl) ether, N, N, n ', n' - TETRAMETHYLENEDIAMINE, triethylamine, N, n-dimethylbenzylamine, etc.
Alicyclic amine catalysts include solid amine, n-ethylmorpholine, N-Methylmorpholine, N, n '- diethylpiperazine, etc.
The catalysts of alcohols are triethanolamine, DMEA, etc.
Aromatic amines include pyridine, N, n '- dimethylpyridine, etc.
Among the polyurethane elastomers, adhesives, coatings, sealants, waterproof coatings, paving materials other formulations, dibutyltin dilaurate (dy-12) other organic metal catalysts are most commonly used. It is very effective to promote the reaction of isocyanate group hydroxyl group, but it can also accelerate the reaction of water isocyanate in the formula with water. It is doubtful that dy-12 can accelerate the reaction of water isocyanate in the formula with water Special organic catalysts such as lead can be used.
Organic metal compounds include carboxylates, metal alkyl compounds, etc. the metal elements mainly include tin, potassium, lead, mercury, zinc, etc., the most commonly used is organotin compounds.
DY-1 (BIS dimethylaminoethyl ether), DY-5 (pentamethyldiethylenetriamine), dy-8 (dimethylcyclohexylamine), dy-12 (dibutyltin dilaurate), dy-20 (organic bismuth), dy-41 (triazine trimerization catalyst), etc.
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Degree of polymerization
Degree of polymerization refers to the number of atomic clusters that exhibit unique characteristics (i.e., reflect specificity) in organic structure. For methacrylate polyester polyols, the degree of polymerization is the atom number of the starting stopping agents containing the hydrogen.
In the product model of polyester polyether polyol, the hydroxyl value data information of the commodity is generally shown.
the perspective of analysis, the hydroxyl value is defined as the Mg number of ferric chloride solution whose hydroxyl value in one gram of sample is very high.
When you carry out chemical calculation, we must pay attention to that the hydroxyl value in the calculation method refers to the calibrated hydroxyl value, that is, the hydroxyl value calibration = the measured data information of the hydroxyl value analysis + the acid value the hydroxyl value calibration = the data information measured by the hydroxyl value analysis - the base value
For methacrylate, because the acid value is generally small, it is harmful to the chemical calculation whether the hydroxyl value is calibrated.
However, it does great harm to polyester polyols. Due to the high acid value of polyester polyols, the calibration hydroxyl value should be selected as far as possible in professional polyurethane estimation.
Strictly speaking, when calculating the hydroxyl value of polyester, even the moisture in the polyester should be taken into account.
For example, the hydroxyl value of polyester polyol is 224.0, the moisture content is 0.01%, the acid value is 12. The hydroxyl value calibration of polyester polyol is 224.0 + 1.0 + 12.0 = 257.0