Diallyl phthalate process

Diallyl Phthalate (DAP, DAIP) Powder Excellent humidity resistance. Withstands temperatures over 400 F. Easily processed. Dimensional stability excellent. May be compression, transfer and injection molded. Low cost. Precision potentiometers, RF connectors, waveguide auxiliaries, attenuators, heating panels, heated battery cases. 

P.O.38 is stable to styrene monomer, but not entirely fast to acetone, which occasionally leads to bleeding if the pigment is processed according to the diallyl-phthalate method (Sec. 1.8.1.2). This is also true if the pigment is treated with a melamine resin solution. 

Some of the common types of plastics that are used are thermoplastics, such as poly(phenylene sulfide) (PPS) (see POLYMERS CONTAINING SULFUR), nylons, liquid crystal polymer (LCP), the polyesters (qv) such as polyesters that are 30% glass-fiber reinforced, and poly(ethylene terephthalate) (PET), and polyetherimide (PEI) and thermosets such as diallyl phthalate and phenolic resins (qv). Because of the wide variety of manufacturing processes and usage requirements, these materials are available in several variations which have a range of physical properties. 

The methods of polymerization of the diallyl phthalates deal with control of the process to permit isolation of the thermoplastic prepolymer before the fully cured, crosslinked resin is formed. 

There appears to have been little interest in ionic polymerization of the diallyl phthalates. In one patent, it is implied that the initiation of diallyl o-phthalate by boron alkyls in the presence of oxygen probably involves a free-radical process [110]. 

The reactive monomer responsible for the cross-linking reaction is normally styrene, vinyl toluene, methyl methacrylate, or diallyl phthalate. The unsaturated polyester prepolymers are, by themselves, relatively stable at ambient temperatures. When they are added to the cross-linking monomers, however, the blend is extremely unstable. To prevent premature gelation and to control the cross-linking process, inhibitors like hydroquinone are added to the blend. The cross-linking process is usually initiated by an organic peroxide added by the end user. The peroxide may be activated by heat. For room-temperature cure, accelerators and activators such as cobalt salts are also added. The cross-linking reaction can be represented as follows (Equation 5.2) ... 

Diallyl Phthalate Resin Thermoset supplied as diallyl phthalate prepolymer or monomer. Has high chemical, heat and water resistance, dimensional stability, and strength. Shrinks during peroxide curing. Processed by injection, compression, and transfer-molding. Used in glass-reinforced tubing, auto parts, and electrical components. Also called DAP. 

Invention describes the use of plasticizer to dissolve resin. A solution of resin is mixed with graphite to form a mass, which, after the process of calendering, forms a film or a sheet. The formed material is subjected to a temperature sirfficiently high to remove the plasticizer by evaporation (250°C). After the plasticizer (diallyl phthalate) is removed a sheet is subjected to temperatures between 500 and 1000°C imder nitrogen atmosphere which decomposes the resin and leaves a fully carbonaceous diaphragm. Other similar processes were discussed in Chapters 11 and 13. In many cases, the plasticizer is also removed by extraction with a suitable solvent. 

These modifications are necessary to provide the working time-temperature relationship required for screw plasticating. The most commonly used injectionmolding thermosetting materials are the phenolics. Other thermosetting materials often molded by the screw-injection process include melamine, urea, polyester, alkyd, and diallyl phthalate (DAP). (Source Chanda, M. and S. K. Roy, Plastics Technology Handbook, Marcel Dekker, Inc., New York, NY, 1987). 

Liquid injection molding (LIM) A process of injection-molding thermosetting resins in which the uncured resin components are metered, mixed, and injected at relatively low pressures through nozzles into mold cavities, the curing or polymerization taking place in the mold cavities. The process is most widely used with resins that cure by addition polymerization such as polyesters, epoxies, silicones, alkyds, diallyl phthalate, and (occasionally) urethanes. 

Chemical characteristics. The most broadly used allyl resins are prepared from the prepolymers of either DAP or DAIP which have been condensed from dibasic acids. The diallyl phthalate monomer is an ester produced by the esterification process involving a reaction between a dibasic acid (phthalic anhydride) and an alcohol (allyl alcohol) which yields the DAP ortho monomer, as shown in Fig. 2.1. Similar reactions with dibasic acids will yield the DAIP (iso) prepolymer. Both prepolymers are white, free-flowing powders and are relatively stable whether catalyzed or not, with the DAP being more stable and showing negligible change after storage of several years in temperatures up to 90°C. 

Figure 7.3 shows a typical curing curve from a thermoset material showing the exothermic peak produced as heat is released during the curing process. A particular example is the curing study carried out on diallyl phthalate moulding compounds [64, 65]. 

Chemical characteristics. The most broadly used allyl resins are prepared from the prepolymers of either DAP or DAIP, which have been condensed from dibasic acids. The diallyl phthalate monomer is an ester produced by the esterification process in-... 

Chloroprene rubber or, polychloroprene rubber Chlorotrifluoroethylene ethylene copolymers Cis-polyisoprene or, cis-l,4-polyisoprene Coumarone indene resins Diallyl phthalate Diallyl isophthalate Dough molding compound Elastomeric alloy melt processable rubber Elastomeric alloy thermoplastic vulcanizate Epichlohydrin rubber Epoxy or, epoxide Epoxy or, epoxide, with glass fiber Ethyl cellulose Ethylene acryic acid Ethylene propylene diene monomer (an EPR terpolymer)... 

It was observed that up to about 25% conversion, the polymerization of diallyl o-phthalate is linear with time and initiator concentration. As the process continues, a cross-linked gel forms. The polymer formed up to 25% conversion has a melting point of about 90°C, is soluble, and is less unsaturated than would be expected for a linear polymer. Therefore, it was presumed that the prepolymers consisted of a main chain with a number of short branches [30]. 

Simply heating diallyl o-phthalate with benzoyl peroxide at 115°-125 C produced a highly cross-linked thermoset resin [92]. The usual methods of producing prepolymers involve the interruption of the polymerization process before gelation sets in (at about 25% conversion). 

One novel method of polymerization without the use of any peroxide initiator involves heating diallyl o-phthalate under nitrogen in the presence of metallic copper. Below 205°C, copper acts as a retarder of the polymerization. However, above 225°C it accelerates the process (at about 215°C it neither inhibits nor accelerates) [93]. 

The prepolymer has also been prepared in two stages at two different temperatures using two initiators which operate at two distinctly different temperatures like terr-butyl hydroperoxide and di-te/t-butyl peroxide [98]. In a strictly thermal process, diallyl o-phthalate has been polymerized at 200 -250 C. The conversion of monomer to polymer was followed by checking the change in refractive index with time. The process was short stopped before the gel point was reached by adding a solvent which separated unreacted monomer from the polymer [99]. 

The control of the molecular weight of the prepolymer of diallyl o-phthalate has led to several processes which may be considered solution polymerizations in which the solvent serves also as a chain-transfer agent. Procedure 8-4 is an adaptation from a patented process given here to illustrate the process. In this... 

According to another patent, heating 100 parts of diallyl o-phthalate with 2 parts of methanol, 2 parts of carbon tetrachloride, and 0.4 parts of dibenzoyl peroxide for 3.5 hr at 1 lO C results in the isolation of 27 gm of a prepolymer by precipitation with an excess of methanol [105]. After heating 30 gm of the monomer with 10 gm of hexachloroethane for 18 hr with 0.3 gm of dibenzoyl peroxide at 80 C, 12.3 gm of a prepolymer is isolated which could readily be molded. This process affords a greater than 30% yield of prepolymer [106]. Evidently by using a rather large quantity of chain-transfer agent, substantial... 

The disappearance of a plasticizer from water can be the result of a number of abiotic and biotic processes that can transform or degrade the compound into daughter compounds that have different physicochemical properties from the parent compound. Hydrolysis is a family of chemical reactions where a plasticizer reacts with water. Phthalate esters may hydrolyze to form monoesters and then dicarboxylic acid. It has been predicted that di-(2-ethylhexyl) sebacate will form 2-ethylhexanol and decanedioic acid. Wolfe et al experimentally measured second-order alkaline hydrolysis rate constants for dimethyl, diethyl, di-n-butyl, and di-(2-ethylhexyl) phthalates, and it appears that hydrolysis may be too slow to have a major impact on the fate of most dissolved plasticizers. The estimated hydrolysis half-lives at pH 7 for 20 plasticizers were longer than 100 days. No information was located for diallyl, ditridecyl and diundecyl phthalates. Under alkaline conditions, hydrolysis may be important for tricresyl phosphate and tri-(2-ethylhexyl) trimellitate at pH 8 their predicted half-lives are 3.2 and 12 days respectively. 

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