1.6- Hexamethylene diisocyanate

HEXAMETHYLENE DIISOCYANATE (Isocyanic acid, hexamethylene ester 1, 6-Hexanediol, diisocyanate) 

Caution Hexamethylenediamine, hexamethylene diisocyanate, and phosgene are highly toxic. Exposure to vapors or solutions containing these materials should be avoided. All operations should be conducted in a hood. 

Hexamethylenediammonium chloride. To a solution of 116 g. (1.0 mole) of hexamethylenediamine (Note 1) in 145 ml. of methanol in a 1-1. beaker is added slowly from a dropping funnel, 175 ml. of concentrated hydrochloric add (sp. gr. 1.19) 

The mixture is well stirred during the addition and cooled externally to keep the contents below 30°. The hexamethylene-diammonium chloride is then precipitated by adding the solution slowly with stirring to approximately 2 1. of acetone. The precipitate is collected on a Buchner funnel, washed with 100 ml. of cold acetone, and dried in a vacuum oven at 75° for 12-18 hours (Note 2). The yield of dry product amounts to 170-187 g. (90-99%), m.p. 243-246° (Note 3). 

Hexamethylenediamine may be obtained from the Polychemicals Department, E. I. du Pont de Nemours and Company, Inc., Wilmington, Delaware. Usually the commercial product is a 70% aqueous solution from which the water may be distilled at atmospheric pressure. The residue is suitable for preparing the dihydrochloride. 

Synonyms HDI HMDI 1,6-diisoq anato-hexane 1,6-hexamethylene diisoq anate 

Cross-linking agent (hardener) in the production of polyurethane materials such as car paints, dental materials, and contact lenses 

Toxicology. Hexamethylene diisocyanate (HDI) is an irritant of the eyes, mucous membranes, and skin and is a sensitizer of the respiratory tract. 

A second type of response to isocyanates is allergic sensitization of the respiratory tract. This usually develops after some months of exposure. The onset of symptoms may be insidious, becoming progressively more pronounced with continued exposure. Initial symptoms are often nocturnal dyspnea and/or nocturnal cough with progression to asthmatic bronchitis. 

Productive cough and shortness of breath developed in a spray painter 12-18 months 

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Haward et al.t have reported some research in which a copolymer of styrene and hydroxyethylmethacrylate was cross-linked by hexamethylene diisocyanate. Draw the structural formula for a portion of this cross-linked polymer and indicate what part of the molecule is the result of a condensation reaction and what part results from addition polymerization. These authors indicate that the crosslinking reaction is carried out in sufficiently dilute solutions of copolymer that the crosslinking is primarily intramolecular rather than intermolecular. Explain the distinction between these two terms and why concentration affects the relative amounts of each. 

Because of steric effects, TMXDI is less reactive than the trifunctional derivatives of hexamethylene diisocyanate (HDI) (1,6-diisocyanatohexane)... 

Stmctural and chemical modification of urethane containing polymer matri-ces with macrocycles - calixarenes having reactive hydrazide groups have been carried out and stmcture, physico chemical and sensor properties of polyure-thanesemicarbazides (PUS) synthesised have been studied. The polymers obtained (on the base of polypropylene glycol MM 1000 and polysiloxane diol MM 860, hexamethylene diisocyanate and calixarene dihydrazide) are identified by IR-spectroscopy, size exclusion chromatography (SEC), DSC, WAXS and SAXS methods. 

For environmental reasons there has been interest in methods for manufacturing isocyanates without the use of phosgene. One approach has been to produee diurethanes from diamines and then to thermal eleave the diurethanes into diisocyanates and alcohols. Although this method has been used for the production of aliphatic diisocyanates such as hexamethylene diisocyanate and isophorone diisocyanate, for economic reasons it has not been adopted for the major aromatic isocyanates MDI and TDI. 

In certain cases, even dimers of certain isocyanates, such as toluene diisocyanate or hexamethylene diisocyanate, can act as blocking agents, thermally reversing to regenerate the isocyanate [16,17]. 

Applications for blocked urethane adhesives are small. However, they may be used as flocking adhesives or as crosslinkers for solvent-borne adhesives. Blocked urethane adhesives are also used as splicing adhesives for belts. Blocked isocyanates based on TDI, IPDI, and derivatives of hexamethylene diisocyanate are most commonly commercially available. 

Unlike the epoxy resins where the members differ only in their size, the isocyanate resins differ markedly according to the choice of components, but all have the common feature of a diisocyanate as one of the components. Two of the most widely used diisocyanates are tolylene diisocyanate and hexamethylene diisocyanate which have the following structures ... 

From these, prepolymers are prepared where the diisocyanates may be completely reacted as in the case of the urethane oils which resemble the oil-modified alkyds but have urethane (—NHCOO—) links in place of the ester (—COO—) links of the alkyds, or where one only of the isocyanate groups is combined, leaving the other to participate in crosslinking reactions. Such a reactive prepolymer is the biuret that may be prepared from hexamethylene diisocyanate, has the following structure ... 

The proplnts developed by Aerojet (Ref 3) use v small amts of ferric acetylacetonate as the catalyst or polymerization agent. Proplnts developed by JPL (Ref 2) use hexamethylene diisocyanate as the copolymer of PGN, together with a nitric ester plasticizer and ferric acetylacetonate as the curing catalyst. 

A three-necked flask equipped with a condenser and stirrer was charged with the PET depolymerization product (0.05 mol of BHET and dimer in the ratio of 80 to 20 wt%), 0.05, 0.10, and 0.15 mol of e-caprolactone (in separate experiments), and 0.1 wt% of dibutyltin dilaurate. The reaction mixture was heated at 150°C for 2 h. The resulting co-oligomer (0.01 mol) was dissolved in 500 mL of tetrahydrofuran in a three-necked flask equipped with a condenser and a stirrer. After the temperature was raised to 67°C, a solution of 0.01 mL of hexamethylene diisocyanate in 50 mL of tetrahydrofuran was added dropwise. After heating and stirring the reaction mixture for 12 h, it was cooled and precipitated in ether. The polyurethane precipitate was collected by filtration and dried at 70°C for 12 h. 

Heterocyclic block copolymers, 282-284 Heterocyclic diamines, rigid, 281 Heterocyclic polymers, structure-property relationships in, 273-274 Heterocyclic ring formation, PQ and PPQ synthesis by, 309-310 Hexadecyltrimethylammonium bromide (HTMAB), 549-550 Hexamethylene diisocyanate (HDI), 199, 210. See also HDI trimer Hexamethylenediamine-adipic acid salt, 169, 170... 

Recently, Cohn and Salomon synthesized and characterized a series of PLCL thermoplastic bioelastomers by two-step synthesis procedure. First, ring-opening polymerization of L-lactide initiated by the hydroxyl terminal groups of the PCL chain. Second, chain extension polymerization of these PLA-PCL-PLA triblocks initiated by the hexamethylene diisocyanate (HDl). 

Most of the hexamethylenediamine produced is used for the manufacture of Type 66 nylon by polymerization with adipic acid. A minor use is for the preparation of hexamethylene diisocyanate used in light-stable polyurethane coatings. 

Poly(boronic carbamatejs were prepared by alkoxyboration polymerization of diisocyanates with mesityldimethoxyborane (scheme 33).59 The polymers obtained have boronic carbamate functions in their repeating units and can be expected to be novel reactive polymers. First, alkoxyboration polymerization between mesityldimethoxyborane and 1,6-hexamethylene diisocyanate was examined, and the optimized reaction conditions were bulk reactions at 140°C. Both aliphatic and aromatic diisocyanates gave the corresponding polymers. When aromatic diisocyanates were employed, the... 

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