REACTION INJECTION

This phosphoms-rich oligomer can also be incorporated into polyurethanes. Combinations with Eyrol 6 permit the OH number to be adjusted to typical values used in flexible foam, urethane coating, or reaction injection mol ding (RIM) appHcations (115,116). 

The sandwich-type stmcture of polyurethanes with a smooth integral skin produced by the reaction injection molding process provides a high degree of stiffness as weU as exceUent thermal and acoustical properties necessary for its use in housing and load-bearing stmctural components for the automotive, business machine, electrical, furniture, and materials-handling industry. 

Dicyclopentadiene is also polymerized with tungsten-based catalysts. Because the polymerization reaction produces heavily cross-Unked resins, the polymers are manufactured in a reaction injection mol ding (RIM) process, in which all catalyst components and resin modifiers are slurried in two batches of the monomer. The first batch contains the catalyst (a mixture of WCl and WOCl, nonylphenol, acetylacetone, additives, and fillers the second batch contains the co-catalyst (a combination of an alkyl aluminum compound and a Lewis base such as ether), antioxidants, and elastomeric fillers (qv) for better moldabihty (50). Mixing two Uquids in a mold results in a rapid polymerization reaction. Its rate is controlled by the ratio between the co-catalyst and the Lewis base. Depending on the catalyst composition, solidification time of the reaction mixture can vary from two seconds to an hour. Similar catalyst systems are used for polymerization of norbomene and for norbomene copolymerization with ethyhdenenorbomene. 

Nylon-6 can also be produced from molten caprolactam using strong bases as catalysts (anionic polymerization) this is used as the basis of monomer casting and reaction injection mol ding (RIM). Anionic polymerization proceeds much faster than the hydrolytic route but products retain catalysts which may need to be extracted. 

Reaction Injection Molding. RIM uses the anionic polymeri2ation of nylon-6 to carry out polymeri2ation in the mold. A commercial process involves the production of block copolymers of nylon-6 and a polyether by mixing molten caprolactam, catalyst, and polyether prepolymer, and reacting in a mold (27,28). 

The major uses of aniline are in the manufacture of polymers, mbber, agricultural chemicals, dyes and pigments, pharmaceuticals, and photographic chemicals. Approximately 67% of the wodd production of aniline is used in the manufacture of rigid polyurethanes and reaction-injection-molded (RIM) parts for the constmction, automotive, and durable goods industries. 

Fig. 19. Typical injection molding and reaction injection molding (RIM) machines (a) injection molding machine for thermoplastics (b) reaction injection molding machine, showing A, the closed position, where reagents circulate, and B, the open position, where reagents are mixed and dispensed to mold.

When surfactant-coated glass fibers are included to improve product flexibility and reduce thermal expansion, these semibatch processes are termed reinforced reaction injection mol ding (RRIM). 

M. E. Edwards, Chemical Reaction Engineering of Polymer Processing Reaction Injection Moulding Inst. Chem. Eng. Symp. Ser. 8(87), 783—796 (1984). 

The late 1950s saw the emergence of cast elastomers, which led to the development of reaction injection mol ding (RIM) at Bayer AG in Leverkusen, Germany, in 1964 (see Plastics processing). Also, thermoplastic polyurethane elastomers (TPUs) and Spandex fibers (see Fibers, elastomeric) were introduced during this time. In addition, urethane-based synthetic leather (see Leather-LIKEmaterials) was introduced by Du Pont under the trade name Corfam in 1963. 

The Hquid monomers are suitable for bulk polymerization processes. The reaction can be conducted in a mold (casting, reaction injection mol ding), continuously on a conveyor (block and panel foam production), or in an extmder (thermoplastic polyurethane elastomers and engineering thermoplastics). Also, spraying of the monomers onto the surface of suitable substrates provides insulation barriers or cross-linked coatings. 

The largest segment of the CASE family of polyurethanes are elastomers. Cast polyurethane elastomers reached a new dimension when high pressure impingement mixing led to reaction injection molding (RIM). This technology is used widely in the automotive industry, and reinforced versions (RRIM) and stmctural molded parts (SRIM) have been added in more recent years. 

Because of the unusual reactivity of the DCPD molecule, there are a number of wide and varying end use areas. The primary uses in the U.S. are DCPD-based unsaturated polyester resins (36%) hydrocarbon type resins, based on DCPD alone or with other reactive olefins (39%) EPDM elastomers via a third monomer ethylidenenorhornene or DCPD (16%) and miscellaneous uses (9%), including polychlorinated pesticides, polyhalogenated flame retardants, and polydicyclopentadiene for reaction injection mol ding (39). 

The resins have wide appHcation. In nonreinforced form they serve as insulating coatings for electrical coils (46—47). As fiber reinforced resins, they can be made by reaction injection mol ding into laminates, castings, and coatings (48—49). Fiber-reinforced resins are used in marine appHcations (recreational boats) automotive parts (50) bathroom countertops and shower stalls and tubs and more recendy as baUistic protection for military vehicles and aircraft. 

Poly(dicyclopentadiene). The development of polydicyclopentadiene [25038-78-2] for reaction injection molding is an area which has generated much interest. The polyDCPD is obtained via metathesis polymerization of high purity (usually greater than 98%) DCPD. Excellent reviews (61—62) of the chemistry and properties of polyDCPD have been pubHshed. The patent Hterature of polyDCPD synthesis, catalysts, modifiers, and appHcations is dominated by Hercules (44 patents) and B. F. Goodrich (43 patents) in the U.S. Other participants are Orkem, SheU, Nippon Zeon, and Teijin. 

Reaction-Injection Molding and Reactive Casting. Reaction-iajection molding (RIM) (22) and reactive casting (23) have been demonstrated on nylon-6, which is polymerized by catalytic ring opening and linear recondensation of S-caprolactam (qv) (24). 

An important development of polymerisation casting is that of reaction injection moulding. Developed primarily for polyurethanes (and discussed further in Chapter 27), the process has also found some use with polyamides and with epoxide resins. 

Reaction injection moulding techniques, developed primarily for polyurethanes (see Chapter 27), have also been adapted for nylon 6 in what must be considered as a variation of the polymerisation casting technique. 

Not only are these reactions of importance in the development of the cross-linked polyurethane networks which are involved in the manufacture of most polyurethane products but many are now also being used to produce modified isocycuiates. For example, modified TDI types containing allophanate, urethane and urea groups are now being used in flexible foam manufacture. For flexible integral foams and for reaction injection moulding, modified MDIs and carbodi-imide MDI modifications cU"e employed. 

The reinforced reaction injection moulding (RRIM) process is a development of RIM in which reinforcing fillers such as glass fibres are incorporated into the polymer. One advantage of such a system is to reduce the coefficient of thermal expansion, and with a 40-50% glass fibre content the coefficient is brought into line with those of metals. 

FRISCH, K. c.. Recent Developments in Urethane Elastomers and Reaction Injection Moulded (RIM) Elastomers, Rubber Chem. Technol., 53, 126 (1980)... 

C. W. Macosko, Fundamentals of Reaction Injection Molding, Hanser, New York (1989). 

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