Isocyanates foaming

Isomate [Pfizer], TM for isocyanate foam systems. Available as nonbuming, pour-in-place froth, or spray foams. 

To fill voids with semirigid material (isocyanate foams)... 

Isocyanate Foaming. Alternatively, PAI foams can be prepared by the reaction of multifunctional isocyanates with multifimctional imido carboxylic acids. " The reaction is catalyzed by tertiary amines. Best results are obtained with polymeric diisocyanates from the MDI type. Surfactants... 

Fourteen insulations were examined in this study. The insulations included three types of polyurethane, three varieties of polymethacrylimide, one polybenzimidazole, two polyisocyanurates, two polymetric isocyanate foams (one with chopped fiberglass reinforcement, one without), a modified isocyanate foam, and two insulation systems (one of polymeric isocyanate foam, one of toluenedi isocyanate foam, both with two vapor barriers and fiberglass reinforcement) ... 

Fourteen commercially available organic foam insulations were examined to determine their suitability for insulating liquid hydrogen tanks of subsonic hydrogen fueled aircraft. Materials investigated were polyurethane, polymethacryllmide, polyisocyanurate, polymetric isocyanate, polybenzamidazole, toluenedi isocyanate, and isocyanate foam. The test specimens included foams with chopped fiberglass reinforcements, flame retardants, and vapor barriers. 

Polyurethane Foam n (urethane foam, isocyanate foam) This family of foams differs from other cellular plastics in that the chemical reactions causing foaming occur simultaneously with the polymer-forming reactions. As in the case of Polyurethane Resins the polymeric constituent of urethane foams is made by reacting a polyol with an isocyanate. The polyol may be of the polyester or polyether type. When the isocyanate is in excess of the amount that will react with the polyol. 

The plot shown in Fig. 4 is for an isocyanate foam with a 2.3-lb/ft density and with liquid nitrogen as the test fluid. The plotted line intersects the ordinate at 0.0122 in./min. On this basis, the time it would take to vaporize a 2-in. head... 

In many isocyanate systems, reactions can be so rapid as to present problans in control. Isocyanate foam production involves the following reactions to form COj as foaming agent and then the polymer network ... 

Stepwise polymerization can sometimes be stopped at an early stage and completed in a separate piece of equipment. Such two-stage polymerizations are quite common. In the isocyanate example above, the polypropylene oxide is a low-molecular-weight (x = 15), ring-opening polymer that then becomes part of the isocyanate foam by a different reaction. 

The polycondensation of di-isocyanates with polyhydric alcohols gives a wide range of polyurethanes which are used as artificial rubbers and light-weight foams, and have other important properties. Isocyanates are also used as modifiers in alkyd resins. ... 

Foams. Polyurethane foams are prepared by the polymerization of polyols with isocyanates. 

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 urethane forming ingredients in a polyurethane foam formulation are the isocyanate (1) and the polyol (2) as shown in equation 3. 

Another type of polyol often used in the manufacture of flexible polyurethane foams contains a dispersed soHd phase of organic chemical particles (234—236). The continuous phase is one of the polyols described above for either slab or molded foam as required. The dispersed phase reacts in the polyol using an addition reaction with styrene and acrylonitrile monomers in one type or a coupling reaction with an amine such as hydrazine and isocyanate in another. The soHds content ranges from about 21% with either system to nearly 40% in the styrene—acrylonitrile system. The dispersed soHds confer increased load bearing and in the case of flexible molded foams also act as a ceU opener. 

The isocyanates used with rigid foam systems are either polymeric MDI or specialty types of TDI. Both contain various levels of polymerized isocyanate groups which contribute to molecular weight per cross-link and also may affect reactivity due to steric hindrance of some isocyanate positions. 

RigidPoly(vinylchloride) Foam. The techniques that have been used to produce rigid vinyl foams are similar to those for the manufacture of flexible PVC foams. The two processes that have reached commercial importance for the manufacture of rigid vinyl foams (246) are the Dynamit-Nobel extmsion process and the Kleber-Colombes Polyplastique process for producing cross-linked grafted PVC foams from isocyanate-modified PVC in a two-stage mol ding process. 

The Kleber-Colombes rigid PVC foam (253,254) is produced by compression mol ding vinyl plastisol to react and gel the compound, followed by steam expansion. The process involves mixing, mol ding, and expansion. The formulation consists of PVC, isocyanate, vinyl monomers such as styrene, anhydrides such as maleic anhydride, polymerization initiators, FC-11, and nucleators. The ingredients are mixed in a Wemer-Pfleiderer or a Baker Perkins... 

Methylenebis(4-phenyl isocyanate). This compound is also known as methyl diisocyanate [101-68-8] (MDI) and is produced by the condensation of aniline and formaldehyde with subsequent phosgenation. Its principal end use is rigid urethane foams other end uses include elastic fibers and elastomers. Total formaldehyde use is 5% of production (115). 

Commercially, polymeric MDI is trimerized duting the manufacture of rigid foam to provide improved thermal stabiUty and flammabiUty performance. Numerous catalysts are known to promote the reaction. Tertiary amines and alkaU salts of carboxyUc acids are among the most effective. The common step ia all catalyzed trimerizations is the activatioa of the C=N double boad of the isocyanate group. The example (18) highlights the alkoxide assisted formation of the cycHc dimer and the importance of the subsequent iatermediates. Similar oligomerization steps have beea described previously for other catalysts (61). 

Industrially, polyurethane flexible foam manufacturers combine a version of the carbamate-forming reaction and the amine—isocyanate reaction to provide both density reduction and elastic modulus increases. The overall scheme involves the reaction of one mole of water with one mole of isocyanate to produce a carbamic acid intermediate. The carbamic acid intermediate spontaneously loses carbon dioxide to yield a primary amine which reacts with a second mole of isocyanate to yield a substituted urea. 

Aromatic Isocyanates. In North America, aromatic isocyanates ate heavily used as monomers for addition and condensation polymers. The principal appflcafions include both flexible and rigid polyurethane foam and nonceUulat appflcations, such as coatings, adhesives, elastomers, and fibers. 

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