H12MDI diisocyanate

In certain niche applications, aliphatic isocyanates, such as isophorone diisocyanate (IPDI), hexamethylene diisoeyanate (HDI), methylene 4,4 -biscyclo-hexylisocyanate (H12MDI), and polymeric versions of these diisocyanates, are used, e.g., in instances where light stability or reduced reactivity is needed. These isocyanates usually cost more than the aromatic diisocyanates. Thus, they are used in adhesive areas that can Justify the higher costs. 

Polyurethane dispersions (PUD s) are usually high-performance adhesives based on crystalline, hydrophobic polyester polyols, such as hexamethylene adipate, and aliphatic diisocyanates, such as methylene bis(cyclohexyl isocyanate) (H12MDI) or isophorone diisocyanate (IPDI). These PUD s are at the more expensive end of the waterborne adhesive market but provide excellent performance. 

Where color and light stability of the adhesive are important, and cure speed or cost is less important, aliphatic isocyanates are frequently used. Adhesives derived from isophorone diisocyanate (IPDI), hexamethyl-ene diisocyanate (HDI), or 4,4 -dicyclo-hexylmethane diisocyanate (H12MDI) are available. 

Triohdiisocyanate 1 1 NCO OH, 70% solution in dioxane 70 °C, 1,6-hexamethylene diisocyanate (HDD, 5-isocyanato-1-(isocyanato-methyl)-1,3,3-trimethyl-cyclohexane (IPDI), 1,1 -methylenebis[4-isocyanato-cyclohexane (H12MDI), 1,1 -methylenebis [isocyanato-benzene (MDI) and 1,3-diisocyanatomethyl-benzene (TDI). Me % = percent metal based on polymer solids... 

Figure 3.39 Alicyclic isocyanates, (a) Isophorone diisocyanate (or 3-isocyanato-methyl-3,5,5—trimethylcyclohexyl isocyanate), Huels IPDI (b) l,4-bis(isocyanatometh-yl)cyclohexane, Mobay s p-Desmodur (c) l,3-bis(isocyanatomethyl)cyclohexane, Takeda s Hr,XDI (S3.50) (d) Methylene bis(4—cyclohexylisocyanate), Mobay s Desmodur W ( 3.00). also known as H12MDI, RMDI (reduced MD1), and PACM [bis-/ -aminocyclohcxyl methane].

Although p-phenylene diisocyanate (PPDI) has been synthesized as early as 1913 (18). the Akzo Corp. has developed more recently a modified Hofmann process for the preparation of PPDI (19). A comparison of the reactivity of PPDI in comparison with MDI and NDI (1,5-naphthalene diisocyanate) as well as with aliphatic diisocyanates (H12MDI, IPDI, and CHDI—see Aliphatic Isocyanates) was reported by Wong and Frisch (20). 

A number of other aliphatic diisocyanates that impart excellent color stability to urethane coatings have been introduced into the U.S. market. Foremost among these are 4,4 -methylene bis(cyclohexyl isocyanate) (H12MDI) and Isophorone diisocyanate (25. 26). An isocyanurate ring containing isocyanate produced by trimerization of IPDI is also commercially available (T-1890). 

H12MDI) n. A diisocyanate used in making urethane elastomers and foams. 

Aliphatic diisocyanates can have strong, adverse skin irritation effects and two are well known for this problem, namely dicyclohexylmethane diisocyanate (H12MDI) (Desmodur W by Bayer) and hexamethylene diisocyanate (HDI). Usually care in handling and good hygiene prevents undue problems. Occasionally a more serious effect has been observed in one instance a chemical worker exposed her face to the hot vapour of dicyclohexylmethane diisocyanate and within 24 h her head had swollen to 20% of its original size and characteristic red spots with a white centre were present over the exposed area. Recovery took place slowly over a period of 3 weeks with cortisone-type ointment treatments. Her central nervous system was also affected and took some months to become normal. This was a very unusual and unique incident and is recorded to show that occasionally the unexpected human response can occur with diisocyanates. 

The principal aliphatic isocyanates used are 1,6-hexamethylene diisocyanate (HDD (1,6-isocyanatohexane) [822-06-0], bis(4-isocyanatocyclohexyl)methane (H12MDI) [5124-30-1], and isophorone diisocyanate (IPDI) (3-isocyanato-l-iso-cyanatomethyl)-l,3,3-trimethylcyclohexane [4098-71-9]. Tetramethyl-m-xylidene diisocyanate (TMXDI) [2778-42-9] and m-isopropenyl-a,a-dimethylbenzyl-isocyanate (TMI) (l-(l-isocyanato-l-methylethyl)-3-(l-methylethenyl)benzene [2094-99-7] are specialty products used on a much smaller scale. Diisocyanates are only used as higher molecular weight derivatives in coatings to increase functionality and reduce toxic hazard. 

H12MDI is less volatile than HDI and is sometimes used as afree diisocyanate in coatings to be applied by roll coating, but not by spray coating. It is a mixture of stereoisomers since both isocyanate groups are secondary, reactivity is lower than HDI or IPDI. Combined allophanate-isocyanurate derivatives are available with low free monomer content. Reference 7 covers the chemistry and uses of H12MDI. 

Speckhard T, et al. Properties of polyisobutylene polyurethane block copolymers 3. Hard segments based on 4, 4 -dicyclohexylmethane diisocyanate (H12MDI) and butane diol. Polymer 1985 26(l) 70-8. 

The goal of the study was to create three different hard segments, using a common diisocyanate, H12MDI, and three different reactants DMPA, hexanol, and hexylamine. Then eharacterize all three hard segments with solution and solid state NMR spectroscopy to determine reaction coordinates, reaction rates, and possible side reactions. 

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