Methylene diphenyl isocyanate

Commonly used isocyanates are toluene dhsocyanate, methylene diphenyl isocyanate, and polymeric isocyanates. Polyols used are macroglycols based on either polyester or polyether. The former [poly(ethylene phthalate) or poly(ethylene 1,6-hexanedioate)] have hydroxyl groups that are free to react with the isocyanate. Most flexible foam is made from 80/20 toluene dhsocyanate (which refers to the ratio of 2,4-toluene dhsocyanate to 2,6-toluene dhsocyanate). High-resilience foam contains about 80% 80/20 toluene dhsocyanate and 20% poly(methylene diphenyl isocyanate), while semi-flexible foam is almost always 100% poly(methylene diphenyl isocyanate). Much of the latter reacts by trimerization to form isocyanurate rings. 

The most commonly used isocyanate in urethane adhesives is MDI. The pure material methylene diphenyl-isocyanate is a solid that melts around 37°C. Many variations of MDI are commercially available, and these variations fall into three major classes monomeric MDI, modified MDI s, and polymeric MDI s. 

The diisocyanate is generally toluene diisocyanate (TDI) or methylene diphenyl isocyanate (MDI) or oligomers based on them. 

Isocyanates are formed by reacting phosgene with an appropriate hydrocarbon substrate. Many isocyanates are possible depending upon the hydrocarbon starting material. The commercially important polyurethanes are manufactured from toluene diisocyanate, based on toluene, and methylene diphenyl isocyanate, based on aniline. Both toluene diisocyanate (TDI) and methylene diphenylene isocyanate (MDI) can be used to manufacture foamed products, but only MDI is used as the primary feedstock for elastomeric polyurethanes. 

In 1985, experiments on an industrial scale were carried out jointly at Quaker Oats Chemicals and Collins Pine Company particleboard plants [35]. In these trials 1 was used as an extender in a polymeric methylene diphenyl isocyanate (MDI) binder (1 MDI = 1 3 w/w). The main conclusions which could be reached from these trials were that savings in binder levels, pressing time, and temperature and drying requirements could be obtained compared with the corresponding performances of standard phenol-formaldehyde and urea-formaldehyde systems. 

For methylene diphenyl diisocyanate (MDI), the initial reaction involves the condensation of aniline [62-53-3] (21) with formaldehyde [50-00-0] to yield a mixture of oligomeric amines (22, where n = 1, 2, 3...). For toluene diisocyanate, amine monomers are prepared by the nitration (qv) of toluene [108-88-3] and subsequent hydrogenation (see Amines byreduction). These materials are converted to the isocyanate, in the majority of the commercial aromatic isocyanate phosgenation processes, using a two-step approach. 

Phenolic-isocyanates (phenolic-urethanes). The binder is supplied in three parts a phenolic resin in an organic solvent (0.8%), methylene diphenyl diisocyanate (MDI) (0.5%), and a liquid amine catalyst. When mixed with sand, the amine causes a reaction between the resin and the MDI, forming urethane bonds, which rapidly set the mixture. The speed of setting is controlled by the type of catalyst. The optimum cure temperature is 25 to 30°C. Compression strength is typically over 4000kPa (600psi). 

The two key isocyanates that are used in the greatest volumes for polyurethane polymers are toluene diisocyanate (TDl) and methylene diphenyl diisocyanate (MDl). Both isocyanates are produced first by nitration of aromatics (toluene and benzene, respectively), followed by hydrogenation of the nitro aromatics to provide aromatic amines. In the case of MDl, the aniline intermediate is then condensed with formaldehyde to produce methylene dianiline (MDA), which is a mixture of monomeric MDA and an oligomeric form that is typical of aniline/formaldehyde condensation products [2]. The subsequent reaction of phosgene with the aromatic amines provides the isocyanate products. Isocyanates can also be prepared by the reaction of aromatic amines with dimethylcarbonate [3, 4]. This technology has been tested at the industrial pilot scale, but is not believed to be practiced commercially at this time. 

Important commercial isocyanates include the diisocyanate monomers toluene diisocyanate (TDI), methylene diphenyl diisocyanate (MDI), hexamethylene diisocyanate (HDI), and MDI-, TDI-, and HDI-based isocyanates (e.g., prepolymers and polyisocyanates). World-wide production volume is estimated at over 12 billion lb. Isocyanates (diisocyanates, polyisocyanates, and prepolymers) all cause similar health effects, most commonly asthma [32]. Isocyanates are reported to be the leading attributable cause of work-related asthma [16]. Isocyanates are potent sensitizers that can trigger a severe and potentially fatal asthma attack in sensitized persons at very low isocyanate exposure levels [16]. Toluene diisocyanate is reasonably anticipated to be a human carcinogen by National Toxicology Program. 

Isocyanates (RNCO) are industrially relevant compounds which find application in several fields [9, 106]. Many isocyanates serve as the starting materials for the manufacture of plant protection agents, pesticides, dyes, resins and plastics, textile waterproofing agents, detergents, bleaches, and adhesives. They are also widely used in surface coatings such as paints, sealants and finishes, and in the manufacture of rubbery plastics such as those used to coat wires. Traditionally, diisocyanates are the primary feedstock for the production of polyurethanes. The global market for diisocyanates in the year 2000 was 4.4 million tonnes, of which 61.3% was methylene diphenyl diisocyanate (MDI), 34.1% was toluene diisocyanate... 

All chemicals used in this study were reagent grade. Butyl isocyanate (BuNCO, 99% from the Upjohn Chemical Co.), hexamethy-lene diisocyanate (HDI, 99% from the Mobay Chemical Co.), phenyl isocyanate (PhNCO, 99%, from the Upjohn Chemical Co.), p-tolyl isocyanate (MePhNCO, 99% from the Aldrich Chmical Co.), p-chloro-phenyl isocyanate (CIPhNCO, 99%, from the Aldrich Chemical Co.) and cyclohexyl isocyanate (CHI, 98%, from the Aldrich Chemical Co.) were purified by vacuum distillation. Methylene diphenyl diisocyanate (MDI, 99%+, from the Mobay Chemical Co.) was used without further purification. N,N-Dimethylformamide (DMF, reagent grade, from the Mallinckrodt) was dried by molecular sieves 4a. The NCO-terminated prepolymers were prepared from poly(oxy-tetramethylenediol) (POTMD, mol. wt. 650, 1000, 2000, Quaker Oats Chem. Co.) and MDI. 

Methylene diphenyl diisocyanate Methylene di (phenylene isocyanate) ... 

Synonyms Bis (1,4-isocyanatophenyl) methane Bis (4-isocyanatophenyl) methane Bis (p-isocyanatophenyl) methane 4,4 -Diisocyanatodiphenylmethane Diphenylmethane diisocyanate Diphenylmethane-4,4 -diisocyanate 4,4 -Diphenylmethane diisocyanate p,p -Diphenylmethane diisocyanate MBI 1,1-Methylenebis (4-isocyanatobenzene) Methylenebis (4-isocyanatobenzene) Methylenebis (p-phenylene isocyanate) Methylene bisphenyl isocyanate Methylene diphenyl diisocyanate Methylene di (phenylene isocyanate)... 

Methylene diphenyl diisocyanate. See MDI 1,1-(Methylenedi-4,1-phenylene) bismaleimide 1,1 -(Methylenedi-4,1-phenylene) bis-IH-pyrrole-2,5-dione. See Bismaleimide Methylene di (phenylene isocyanate) Methylene di-p-phenylene isocyanate. See MDI Methylene dithiocyanate. See Methylenebis (thiocyanate)... 

In other applications, Baysal utilized methylene dicyclohexyl isocyanate to link polybutadiene with polystyrene or poly(methyl methacrylate) to form the appropriate block copolymers(70). Diphenyl methane-4,4 diisocyanate was similarly used to prepare a block... 

Among these, the most common diisocyanates used on a large scale are toluene diisocyanate (TDI) and MDI.TDI was the first commercially available isocyanate and is available as a mixture of 80% 2,4- and 20% 2,6-toluene diisocyanate isomers (Table 6.2), although they are also available as pure single isomers. Similarly, MDI has three isomers, namely 4,4 -, 2,4 -and 2,2 -diphenylmethane diisocyanate. However, only the 4,4 -isomer is used for commercial purposes although all the isomers are present in polymeric methylene diphenyl diisocyanate (PMDI) which is also used in the preparation of polyurethane. 

Phosgene produced by chlorinating carbon monoxide is used as a carbonylating agent to convert amines to isocyanates, as shown by reactions (8) and (9). Thus, the reaction of phosgene with diphenylmethane diamine results in the formation of methylene diphenyl diisocyanate (MDI), and with toluenediamine to form toluene diisocyanate (TDI). The isocyanates are used to produce polyurethanes for flexible and rigid foams, elastomers, coatings, and adhesives, for the construction and automotive industries. 

Asahi Chemical Industry Co., Ltd. has succeeded in developing alternative and innovative non-phosgene processes for producing isocyanates and polycaihonates in the pilot scales which are commercially viable. In the production of isocyanates, processes for both aromatic isocyanates, such as methylene diphenyl diisocyanate (MDI), and aliphatic isocyanates, such as hexamethylene diisocyanate (HDI) or isophoione diisocyanate (IPDI), have already been developed successfully. A part of those processes has already been reported (i), and the others will be reported in the near future. In this paper, the new iimovative process for producing polycarbonates is reported. 

PU based on the use of pristine castor oil were reviewed in 2010 [9, 10], including preparation and properties of an interpenetrating network with other polymers. Recent additions to this topic include work by Larock and co-workers [13, 14] on waterborne PU and their silica composites a kinetic study of the reaction of castor oil with 4,4 -methylene diphenyl diisocyanate to produce an elastomeric matrix [15] the rheology of waterborne PU dispersions for coating applications, prepared with castor oil and isophorone diisocyanate (IPDI) [16] (Scheme 3.7) and the synthesis and characterisation of gelled materials arising from the reaction of isocyanate-bearing chitin or chitosan with castor oil [17]. 

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