Epoxy resins from phenolic compounds

Epoxy phenolic adhesives are polyepoxy compounds which possess epoxy reactivity and phenolic resin heat resistance. These are prepared by condensing epichlorohydrin and novolac phenolics (phenol/formaldehyde ratio > 1). A recent Japanese patent issued to Mitsubishi Petrochemical Co. describes the preparation of epoxy resins from epichlorohydrin condensation with phenolic resins prepared from phenol and substituted aldehydes, e.g., vanillin. These resins (23) have high epoxy contents (epoxy equivalent weights >200) and relatively high softening points (85-95°C). 

Allyl chloride is used to make intermediates for downstream derivatives such as resins and polymers. Approximately 90% of allyl chloride production is used to synthesize epichlorohydrin, which is used as a basic building block for epoxy resins and in glycerol synthesis. Allyl chloride is also a starting material for allyl ethers of phenols, bisphenol A and phenolic resins, and for some allyl esters. Other compounds made from allyl chloride are quaternary amines used in chelating agents and quaternary ammonium salts, which are used in water clarification and sewage sludge flocculation (Kneupper Saathoff, 1993). 

Epoxy resins are essentially condensation products of epichlorhydrin and diphenylolpropane. The latter has been known as the usual phenolic compound of "reduced phenolics." Epichlorhydrin, closely related to glycerol, is readily obtained from natural glycerol, or in the process of making the synthetic product. It is usually obtained by the latter method. 

Polyethers are obtained from three different classes of monomers, namely, carbonyl compounds, cyclic ethers, and phenols. They are manufactured by a variety of polymerization processes, such as polymerization (polyacetal), ring-opening polymerization (polyethylene oxide, polyprophylene oxide, and epoxy resins), oxidative coupling (Polyphenylene oxide), and polycondensation (polysulfone). 

When processing (CM, injection molding, extrusion, ICM, etc.) from uncrosslinked (A state) or crosslinked (B state) duroplastic molding compounds, the shearing forces applied upon injection through dies impose orientations upon the macromolecules and, if any are present, upon the reinforcing fibers as well. Because of the low viscosities of uncrosslinked masses such as phenolic, melamine, UP and epoxy resins and the hot mold wall, relaxation of the molecular orientations sets in quickly. As a rule, duroplastics show little or no orientation. Crosslinking fixes this state. 

In solutions of epoxy resin based on 6is-phenol A and glycerol (Af = 6,500) in ethyleng-lycol acetate and in the gel obtained from these compounds by crosslinking by polypropy-leneglycol with amino endgroups, the concentration dependence D(c) remains the same up to c = 65% (Patterson, 1981). 

These included polyphenolic compounds, mono and diamines, amino phenols, heterocyclic imides and amides, aliphatic diols and polyols, and dimeric fatty acids. Epoxy resins derived from epichlorohydrin are termeA glycidyl-hased resins. 

CNSL is obtained as a by-product of the cashew nut industry, mainly containing anacardic acid 80.9%, cardol 10-15%, cardanol, and 2-methyl cardol (Fig. 10). CNSL occurs as a brown viscous fluid in the shell of cashewnut, a plantation product obtained from the cashew tree, Anacardium oxidentale (Bhunia, et al., 2000). CNSL is used in the manufacture of industrially important materials such as cement, primers, specialty coatings, p)aints, varnishes, adhesives, foundry core oils, automotive brake lining industry, laminating and rubber compounding resins, epoxy resins, and in the manufacture of anionic and non-ionic surface active agents. CNSL modified phenolic resins are suitable for many applications and perform improved corrosion and insulation resistance. 

Cardanol is a main component of thermally treated cashew nut shell liquid (CNSL), and is a phenolic compound with a long unsaturated hydrocarbon chain substituted in the meta position (Figure 2.17a). Urushiol, which is obtained from lacquer tree, poison ivy, poison oak, and poison sumac (Toxicodendron), and used for a raw material of a lacquer (urushi) in East Asia, is also a phenolic compound of catechol with a long unsaturated or saturated hydrocarbon chain (Figure 2.17b). Cardanol-based polymers have been reported very often, while there are a few research reports on urushiol-based polymers. Research on polymers synthesized from cardanol or CNSL are reviewed elsewhere.In the late 1980s, cardanol or CNSL-based polymers began to be reported as novel phenol-formaldehyde type resins and novel epoxy resins.Thereafter, Pillai and his co-workers have vigorously studied synthesis of various type of cardanol-based polymers polymers obtained... 

The authors extended the study to other compounds claiming that rare earth fluorides have promising antiwear properties as the addition of LaFj or CeF corroborated the increased wear resistance of phenolic/epoxy-resin-MoSj bonded solid film. Nevertheless, the endurance of the phenolic/epoxy-resin-MoSj bonded solid film, estimated from the traveling distance without wear of the substrate, increased by 60% with the addition of 2-2.5% LaF. It was doubled at 2% CeF, but increased by a factor of 3.8 when 1% of cerium di-n-butylphosphate (BUC) was incorporated. 

This class of compounds is one of the most important adhesive groups with applications ranging from consumer to aerospace markets. Epoxies are thermosets and are cross-linked during the cure cycle. The chemical stmcmre for a simple epoxy (ethylene oxide) in its unhardened state is shown in Figure 5.2. All epoxy compounds contain two or more of these groups. Epoxy resins form adducts with vinyl, acrylic, and polyester resins producing compounds such as phenol novolac, cresol novolac, bis-[4(2,3-epoxy propyoxy) phenyl] methane, and phenol hydrocarbon novalac [53]. 

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