Epichlorohydrin bisphenol ratios

Taffy Process. Bisphenol A reacts direcdy with epichlorohydrin in the presence of a stoichiometric amount of caustic. The molecular weight of the product is governed by the ratio of epichlorohydrin—bisphenol A. 

The ratio of the main ingredients used in the synthesis of epoxy resins (epichlorohydrin bisphenol A) determines the extent of the reaction and the molecular weight (or value of n repeating units in the molecular chain). The addition of bisphenol A to the reaction mix will advance the molecular weight of the resin and the value of n. As n increases, the viscosity or melting point of the resin also increases. Also as the value of n increases, the number of hydroxyl groups increases while the number of epoxy groups remains constant. 

Mole ratio epichlorohydrin/ bisphenol A Mole ratio NaOH/ epichlorohydrin Softening point, °C Molecular weight Epoxide equivalent Epoxy groups/ molecule... 

Synthesis. lj characterization of the graft copolymer has been reported. The Epoxy resin used is a high molecular weight (Mn=10,000) epichlorohydrin-Bisphenol type, and the acrylic is approximaely a 2 1 molar ratio of methacrylic acld/styrene. The Epoxy/acrylic ratio is approximately 80/20 by weight. Grafting is achieved.by.free radical means... 

Molar Ratio Epichlorohydrin/Bisphenol A Molecular Weight Epoxide Equivalent Softening Point (°C)... 

Bisphenol A is mainly used to manufacture epoxy resins by the reaction with epichlorohydrin in the presence of caustic soda at 40 to 60 °C. This yields resins with a molecular weight between 450 and 4000. The molecular weight of the resins increases as the epichlorohydrin/bisphenol A ratio falls. 

SERs are prepared by two processes the taffy process and the advancement or fusion process. The first is directly from epichlorohydrin, bisphenol A, and a stoichiometric amount of NaOH. This process is very similar to the caustic coupling process used to prepare liquid epoxy resins. Lower epichlorohydrin to bisphenol A ratios are used to promote formation of high MW resins. The term taffy is derived from the appearance of the advanced epoxy resin prior to its separation from water and precipitated salts. 

In the taffy process, a calculated excess of epichlorohydrin governs the degree of polymerization. However, preparation of the higher molecular weight species is subject to practical limitations of handling and agitation of highly viscous materials. The effect of epichlorohydrin-bisphenol A (ECH-BPA) ratio for a series of solid resins is shown in Table 6. 

Table 6. Effect of Epichlorohydrin-Bisphenol A Ratio on Resin Properties of Taffy SERs...

The products obtained vary in molecular weight depending on the excess of epichlorohydrin used. The use of 10 1 mole ratio of epichlorohydrin bisphenol A gave a molecular weight of 370. However the use of 1.4 1 mole ratio gives a molecular weight of 791 [33]. 

Polymeric products [117] are obtained when the mole ratio is less than 2 for the epichlorohydrin-bisphenol A reaction and a molecular weight of 1420 is reported at a mole ratio of 1.2 [118]. High molecular weight resins (30,000 or more) are known as phenoxy resins, and these thermoplastic resins are used for coatings, adhesives, and various molding applications. 

The most widely used epoxies are those derived from the condensation of epichloro-hydrin with bisphenol A. The degree of oligomerization, can be controlled by varying the epichlorohydrin/bisphenol A ratio. When this ratio is 2 1 or more, the major product is the diglycidyl ether monomer, where n is zero in the general formula. 

The reaction actually involves the sodium salt of bisphenol A since polymerization is carried out in the presence of an equivalent of sodium hydroxide. Reaction temperatures are in the range 50-95°C. Side reactions (hydrolysis of epichlorohydrin, reaction of epichlorohydrin with hydroxyl groups of polymer or impurities) as well as the stoichiometric ratio need to be controlled to produce a prepolymer with two epoxide end groups. Either liquid or solid prepolymers are produced by control of molecular weight typical values of n are less than 1 for liquid prepolymers and in the range 2-30 for solid prepolymers. 

The IPNs prepared were composed of a rubbery polyurethane and a glassy epoxy component. For the polyurethane portion, a carbodiimide-modified diphenyl-methane diisocyanate (Isonate 143L) was used with a polycaprolactone glycol (TONE polyol 0230) and a dibutyltin dilaurate catalyst (T-12). For the epoxy, a bisphenol-A epichlorohydrin (DER 330) was used with a Lewis acid catalyst system (BF -etherate). The catalysts crosslink via a ring-opening mechanism and were intentionally selected to provide minimum grafting with any of the polyurethane components. The urethane/epoxy ratio was maintained constant at 50/50. A number of fillers were included in the IPN formulations. The materials used are shown in Table I. 

DGEBA epoxy resins. Two moles of epichlorohydrin are theoretically required for each mole of bisphenol A. However, this ratio gives less than 10% yield practically. Therefore excess of epichlorohydrin is used by doubling or triphng the amount to achieve greater than 90% yields. The process involves the following stages (Lee and Nivelle, 1972) ... 

Polymers that contain an epoxide group include various carbon skeletons, but by far the most important group commercially are formed from reaction of bisphenol A or bisphenol F with epichlorohydrin. By manipulation of the mole ratio of reactants and of the reaction conditions, a range of polymers is formed in which the value of n in formulas A-C varies from 0 up to about 12. Formulas A-C are idealized formulas and it is believed that variations from this occur. However, discussion of such matters is beyond the scope of this chapter and the reader is referred elsewhere" ". ... 

The molecular weights of epoxy resins depend on the molar ratio of epichlorohydrin and bisphenol A used in their preparation (see Table 4.25). In a typical process for the production of liquid epoxy resins, epichlorohydrin and bisphenol A in the molar ratio of 10 1 are added to a stainless steel kettle fitted with a powerful anchor stirrer. The water content of the mixture is reduced to below 2% by heating the mixture until the epichlorohydrin-water distils off. After condensation, the epichlorohydrin layer is returned to the kettle, the water being discarded. 

Under similar conditions to those used in (a), 22.8 g (0.1 mol) of bisphenol A, 5.55 g (0.14 mol) of NaOH (dissolved in 56 ml water), and 11.3 g (0.123 mol) of epichlorohydrin are allowed to react with one another. Because of the smaller molar ratio of epichlorohydrin to bisphenol A (1.22) the resulting epoxy resin is of higher molecular weight than that produced in (a). The epoxy value is approximately 0.1, corresponding to 1.44 epoxy groups per molecule of resin (equivalent weight... 

Epoxy Resins. The largest volume epoxy resins are made by reacting BPA [4,4 -(l-methylethylethylidene)bisphenol] [80-05-7] with epichlorohydrin (ECH). The resins are represented by the following general formula, where the molar ratio of ECH to BPA determines the average n value. 

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