News Details
Crosslinking agent for isocyanate coatings
2017-8-7 23:35:41
Crosslinking agent for isocyanate coatings
The crosslinking agent of isocyanate coatings is the general term of various esters of isocyanate. If the number of - NCO groups is classified, including monoisocyanate R - N = C = O and diisocyanate O = C = n-r-n = C = O and polyisocyanate, etc.
Monoisocyanate is an important intermediates of organic synthesis, which can be used to make a series of urethane insecticides, fungicides and herbicides, as well as to improve the water resistance of plastics, fabrics and leather. Functional groups and above isocyanates can be used to synthesize a series of excellent polyurethane foam plastics, rubber, elastic fibers, coatings, adhesives, synthetic leather, artificial wood and so on.
Common isocyanate crosslinking agent for coating industry:
1) toluene diisocyanate (TDI)
2) diphenylmethane diisocyanate (MDI)
3) polymethylene polyphenyl isocyanates (PAPI)
4) diisocyanate (HDI)
5) benzene dimethylene diisocyanate (XDI)
6) isoflone diisocyanate (IPDI)
Currently, the most widely used and the largest isocyanate crosslinking agent is Toluene Diisocyanate (TDI). Methylenediphenyl Diisocyanate (MDI).
1. The most commonly used raw material in polyurethane paint is toluene diisocyanate (TDI), which is made from toluene by nitrification to dinitrotoluene, which is reduced to diamino-toluene and then gasified.
Toluene diisocyanate (TDI) is a colorless, has a strong pungent flavour liquid, the boiling point of 251 ° C, specific gravity 1.22, with light black, has strong stimulation to the skin, eyes, and can cause eczema with bronchial asthma, is mainly used for polyurethane foam plastics, coating, synthetic rubber, insulating paint, adhesives, etc. According to its composition, toluene diisocyanate is a nitrogen-containing organic compound. The production of polyurethane high polymer, often choose toluene diisocyanate mainly for the following reasons:
1) the nitrification of toluene is much faster than that of benzene (24:1), which is that the dinitrotoluene is easy to produce
2) toluene diamine is aromatic amines, which are easier to gasify and make diisocyanate than fat people
3) because it is aromatic isocyanate, the reaction activity is high, it is beneficial to make foam plastics, coating and so on
Chinese name: Diethyl toluene diamine(DETDA)Chinese alias: aryl, aryl diethyl - aryl - methyl-p-phenylenediamine
English name: Benzenediamine, ar, ar-diethyl-ar-methyl-English aliases:Diethyltoluenediamine; ar, ar-Diethyl-ar-methylbenzenediamine;Diethylmethylbenzenediamine;
CAS No. :68479-98-1
EINECS No. :270 -877-4
Molecular formula: C11H18N2
Molecular Weight: 178.28
Boiling point: 310 ℃
Refractive index: 1.581
Flash Point: > 140 ℃
Inchi: InChI = 1/C11H18N2/c1-4-8-6-7 (3) 10 (12) 11 (13) 9 (8) 5-2/h6H ,4-5,12-13H2 ,1-3H3 density : 1.022
Risk Codes: R10; R35
RIDADR: UN 3082
Safety instructions: S2; S26; S39; S61
Packing Group: III
Hazard Class: 6.1
2. Diphenylmethane diisocyanate is a diphenylenediamine, which is condensed by aniline and formaldehyde, and then photochemical. Diphenylmethane diisocyanate (MDI) is divided into pure MDI and crude MDI. Pure MDI under normal temperature for white solid, when heated to stimulate the stink, the boiling point of 196 ° C, it is mainly used for rigid polyurethane foam plastics, synthetic fiber, synthetic rubber, synthetic leather, adhesives, etc. According to its composition, pure diphenyl methane diisocyanate is also a nitrogen-containing organic compound.
The use of diphenylmethane diisocyanate in coatings is less than toluene diisocyanate, for several reasons:
1) MDI is solid, which is not convenient for pipeline delivery and feeding
2) the two NCO bases of MDI have the same reaction activity. It is more difficult to make prepolymer, and the distribution of the product is wide
3) the storage process of MDI is not stable, and it will get together on its own. It needs to be refrigerated and stored and transported
4) the yellowing of MDI coating is more serious than TDI
But MDI coatings also have the following advantages:
1) the vapor pressure of free MDI is far lower than that of TDI, so the toxicity is low
2) MDI symmetric structure, make its paint film strength, abrasion resistance and flexibility are better than the TDI coating, and the rapid drying, overseas a lot for the moisture crosslinking floor paint, anti-corrosion primer, elastic coatings.
Copyright: Zhang Jia Gang YaRui Chemical co.,Ltd
Copyright: Zhang Jia Gang YaRui Chemical co.,Ltd
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