Diphenylmethane diisocyanate , from

Adhesives based on isocyanate (especially PMDl, polymethylene diisocyanate, more exactly polymeric 4,4 -diphenylmethane diisocyanate) have been used for more than 25 years in the wood-based panel industry [88], but still have a low market value in the wood-working industry compared to systems based on UF-, MUF- or PF-resins. The main application is the production of waterproof panels, but also the production of panels from raw materials that are difficult to glue, like straw, bagasse, rice shells or sugar cane bagasse. They can be used as adhesives for wood-based products like particleboard, oriented strandboard (OSB), laminated strand lumber (LSL), medium-density fiberboard (MDF) or... 

Figure 6. Analysis (29) according to Eq. 7 of gel-point data (25, 26, 28) from reactions of HDI and diphenylmethane diisocyanate (MDl) with POP trilos (LHT-240, LHTII2) and tetrols (OPPE-NHI, OPPE-NH2-oxypropylated pentaerythri-tols) in bulk and in nitrobenzene solution at 80°C, with cMt = cao + ecosystems 1 and 2, HDI and POP triols 3, MDl and POP triol 4 and 5, HDI and POP tetrols. Key 1, HDI and LHT240, is 33 2, HDI and LHTII2, v is 61 3, MDl and LHT240, v is 30 4, HDI and OPPE-NHI, v is 29 S, HDI and OPPE-NH2, v is 33.

Polyurethane networks were prepared from polyoxypropylene (POP) triols(Union Carbide Niax Polyols) after removal of water by azeotropic distillation with benzene. For Niax LHT 240, the number-average molecular weight determined by VPO was 710 and the number-average functionality fn, calculated from Mjj and the content of OH groupSj determined by using excess phenyl isocyanate and titration of unreacted phenyl isocyanate with dibutylamine, was 2.78 the content of residual water was 0.02 wt.-%. For the Niax LG-56, 1 =2630, fn=2.78, and the content of H2O was 0.02wt.-%. The triols were reacted with recrystallized 4,4"-diphenylmethane diisocyanate in the presence of 0.002 wt.-% dibutyltin dilaurate under exclusion of moisture at 80 C for 7 days. The molar ratio r0H = [OH]/ [NCO] varied between 1.0 and 1.8. For dry samples, the stress-strain dependences were measured at 60 C in nitrogen atmosphere. The relaxation was sufficiently fast and no extrapolation to infinite time was necessary. 

Bascom R, Kennedy TP, Levitz D, et al. 1985. Specific bronchoalveolar lavage IgG antibody in hypersensitivity pneumonitis from diphenylmethane diisocyanate. Am Rev Respir Dis 131(3) 463-465. 

Over time, uretdione continues to form in 4,4 -diphenylmethane diisocyanate until it precipitates from melted 4,4 -diphenylmethane diisocyanate. For example, pure 4,4 -diphenylmethane diisocyanate compositions... 

Littorin, M., Truedsson, L., Welinder, H.. Skarping, G, Martensson, U. Sjohohn, A.G (1994) Acute respiratory disorder, rhinoconjimctivitis and fever associated with the pyrolysis of polyurethane derived from diphenylmethane diisocyanate. Scand. J. Work Environ. Health, 20,216-222... 

The catalysts of reactions between 4,4 -diphenylmethane diisocyanate (MDI) and alcohols in N,N-dimethylformamide (DMF) by dibutylin dilaurate has been investigated. The reaction rate of the catalyzed urethane formation in DMF is proportional to the square root of dibutylin dilaurate concentration. This result differs from that of similar studies on apolar solvents. The catalysis in DMF can be explained very well by a mechanism in which a small amount of the dibutylin dilaurate dissociates into a catalytic active species. 

The decrease in rate after 50% reaction is quite apparent in the reaction of tolylene diisocyanate with the polyester at 29°C (Fig. 11). This change in rate illustrates the reduced reactivity of the 2-position isocyanate group, having steric hindrance from the ortho methyl substituent, as well as the lesser activating influence of a meta urethane substituent compared to a meta isocyanate substituent. An increase in reaction temperature favours the slow reaction more than the fast, as would be expected if differences in activation energy accounted for at least part of the difference in rates. Thus at 100°C there was little decrease in rate of reaction with TDI. In the case of 4,4 -diphenylmethane diisocyanate (Fig. 12), there was little change in rate after 50% reaction at any of the temperatures studied. 

The production of aniline is a major international business, carried on in the US, Europe and Asia, mainly for the conversion, by reaction with formaldehyde under acid-catalyzed conditions, into diaminodiphenylmethanes 9a, 9b and 9c, and then into isocyanates, mainly 4,4/-methylenebis(phenylisocyanate) (MDI, also known as 4,4 -methylene-di-paraphenylene isocyanate, 4,4 -diphenylmethane diisocyanate, methylene diphenylene diisocyanate and diisocyanato diphenyl methane) (9d), from which polyurethanes are produced. This accounts for well over 60% of total demand (Figure 1). Aniline is also used in bulk for the production of antioxidants and vulcanization accelerators for rubber. Some 15.5 million lbs. of cyclohexylamine are made each year mainly by catalytic hydrogenation of aniline. Half the demand is for use as a boiler water additive. Other major uses include in the manufacture of herbicides, plasticizers, emulsifying agents, dyes, dry-cleaning soaps, acid gas absorbents and, in Asia, cyclamate sweeteners. Apart from India, the use of aniline for dyestuff manufacture represents about 10% of demand. 

In the last few years, however, 4,4 -diphenylmethane diisocyanate (methane diphenyldi isocyanate, MDI), whose precursor 4,4 -diaminodiphenylmethane is obtained from the condensation of aniline with formaldehyde, has overtaken TDI. In 1990, capacities in Western Europe, the United States, and Japan for MDI were 600,000, 530,000, and 190,000, tons, respectively for TDI, they were 400,000, 360,000, and 110,000 tons [91]. 

The same strong effect on the viscosity decrease was observed by the introduction of an internal poly [EO] block in the case of synthesis of aromatic aminic polyols derived from methylenedianiline (MDA), a precursor of diphenylmethane diisocyanate (MDI) [2, 5, 6] ... 

The phosgene toxicity, separation of hydrochloric acid from excess phosgene, and the use of chlorinated solvents as a reaction medium are the major drawbacks of this reaction process. Extensive studies have suggested that carbamate and dicarbamate can serve as environmentally benign precursors for the synthesis of isocyanate and diisocyanate (1-5). Figure 1 illustrates nonphosgene routes for the synthesis of two important diisocyanates [i.e., 4,4 -diphenylmethane diisocyanate (MDI) and toluene diisocyanate(TDI)] via carbonate and carbamate. 

Problem 5.26 A crosslinked polyurethane is to be made from diphenylmethane diisocyanate, OCNC6H4CH2C6H4NCO, and a polymeric tetrol, R(OH)4, without addition of any water (Rempp and Merrill, 1986). Let the stoichiometric ratio of initial concentrations of NCO to OH groups be denoted by r. 

It is, however, also possible to start with the free amine, provided that reaction is first converted with an excess of phosgene in the cold. The amine, sometimes in solution, is usually added to a cooled solution of an excess of phosgene the symmetrical urea derivative is not formed under these conditions, but instead a mixture of the amine hydrochloride and the carbamoyl chloride which then reacts further with phosgene as described above. For instance, the 4,4 -diisocyanate from diphenylmethane was prepared in this way.629... 

Diisocyanates are an important class of chemicals of commercial interest, which are frequently used in the manufacture of indoor materials. such as adhesives, coatings, foams and rubbers (Ulrich, 1989). In some types of particle board, the diisocyanates have replaced formaldehyde. Isocyanates are characterized by the electrophilic -N=C=0 group, which can easily react with molecules containing hydroxy groups, such as water or alcohols. On hydrolysis with water, primary amines are formed, while a reaction with alcohols leads to carbamates (urethanes). Polyurethane (PUR) products are then obtained from a polyaddition of diisocyanate and diol components. Compounds commonly used in industrial surface technology are 4,4 -diphenylmethane diisocyanate (MDI) and hexamethylene diisocyanate (HDI). The diisocyanate monomers are known as respiratory sensitizers and cause irritation of eyes, skin and mucous membrane. Therefore, polyisocyanates such as HDI-biuret and HDI-isocyanurate with a monomer content <0.5 % are used for industrial applications, and isocyanate monomers will not achieve high concentrations in ambient air. Nevertheless, it is desirable to measure even trace emissions from materials in private dwellings. 

As compared to metallic compounds used as shape memory materials, shape memory polymers have low density, high shape recoverability, easy processability, and low cost. Since the discovery by Mitsubishi in 1988, polyurethane SMPs have attracted a great deal of attention due to their unique properties, such as a wide range of shape recovery temperatures (— 30°C to 70°C) and excellent biocompatibility, besides the usual advantages of plastics. A series of shape memory polyurethanes (SPMUs), prepared from polycaprolactone diols (PCL), 1,4-butanediol (BDO) (chain extender), and 4,4 -diphenylmethane diisocyanate (MDI) or toluene diisocyanate (TDI) have recently been introduced [200—202]. 

Polyurethane ether (PUR-ether) foams are thought to degrade primarily by oxidation, particularly in the presence of light, resulting in discolouration and a loss of mechanical properties. Polyurethanes synthesized from a polyether polyol and an aromatic diisocyanate such as diphenylmethane diisocyanate (MDI) are highly vulnerable to photo-oxidation, whereas polyester-based polyurethanes are more resistant to ultraviolet radiation (Kerr and Batcheller, 1993). Metal ions, particularly copper, aluminium and zinc, form chelates with some polyurethanes imparting increased sensitivity to photo-oxidation (Ranby and Rabek, 1975). 

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