Epoxies, ester-type

Epoxy ester-type resins from diepoxide... 

Synthesis. The synthesis of epoxy ester type resins from diepoxide ( ) is illustrated in Figure 1. 

Plasticizers (qv) can range in composition from the ester types, ie, epoxies, phosphate, amides, etc. The effect of any one of these on curing is usually pH-dependent. However, it is pmdent to investigate each on a case by case basis. 

High phenyl content resins are compatible with organic resins of the P-F, U-F, M-F, epoxy-ester and oil-modified alkyd types but are not compatible with non-modified alkyds. Silicone resins are highly water repellent. 

Epoxy ester Epoxy esters are a type of alkyd where a high molecular weight resin is reacted with alkyd resin. The curing mechanism remains primarily through the oil-oxidation reaction and their properties are in no way similar to the chemically reacted epoxies. They have similar properties to alkyds although with improved chemical resistance but inferior appearance. They form a reasonably hard, oil-resistant coating, which can sometimes be suitable for machinery enamels, but are primarily for interior use, since they tend to chalk rapidly on exteriors. Their best use is for chemical or water resistance where circumstances dictate that finishes that are more superior cannot be used. 

Epoxide resins can be esterified with fatty acids to give media ranging from air-drying to stoving types. The presence of fatty acid reduces the chemical resistance to the same order as that of the alkyds. It is nevertheless sometimes found advantageous to use an epoxy ester for certain specialised purposes. 

Aldehydes and ketones condense with a-halo esters in the presence of bases to give ot,p-epoxy esters, called glycidic esters. This is called the Darzens condensation. The reaction consists of an initial Knoevenagel-type reaction (16-41), followed by an internal Sn2 reaction (10-13) ° ... 

A farther example of the same type of rearrangement is provided by the observation of Komfeld and oo-workers,888 drawn durim lla-ir synthesis of lysergic acid, that treatment of the 0,y-epoxy ester derivative shown in Eq. (509) with the base saroosine (tbe ethyl ester of A -methylglydue) led to a lactone instead of the desired nucleophilic addition product. 

The formation of the six-membered ether ring via epoxy ester-ortho ester cyclic ether rearrangement supports the hypothesis that epoxy ester-ortho ester cyclic ether rearrangement may be involved in the biosynthesis of ladder-type marine polyether toxins. This reaction represents a biomimetic preparation of medium ring cyclic ethers. 

Organic zinc-rich primers are based on epoxy/polyamides, high-molecular-weight linear epoxies, moisture-cured urethanes, high-styrene resins, chlorinated rubbers and epoxy esters. In this type of primer zinc is covered with a monomolecular layer of the binder which facilitates the adhesion of the film to the substrate. 

As an alternative route to the sesquicarane-type sesquiterpenoids, Hortmann and Ong have examined the carbanionic opening of the epoxy-ester (70) derived from perillaldehyde (71). The two products of this reaction are (72) and (73) in the ratio 3 1. Further elaborations of these two compounds have still to be carried out. Plattner and Rapoport have now reported the preparation of both (+)- and (— )-sirenin. This was accomplished by preparative g.l.c. separation of the two diastereoisomeric pairs of ketals derived from the synthetic ketone (74) and D-( —)- and L-( -1- )-butane-2,3-diols. Synthetic procedures for the conversion of racemic (74) into both racemic sirenin and racemic sesquicarene had already been developed. Furthermore, these authors have firmly established by chemical correlation and c.d. studies that naturally-occurring sirenin and sesquicarene have the same absolute stereochemistry, i.e. (75) and (76) respectively. 

The related (Z)-lithium dialkenylcuprates (147) derived from acetylene itself also react well with epoxides to provide a useful route to (2)-homoallylic alcohols the lack of reactivity with esters allows an easy access to lactones (148) by condensations between epoxy esters and this type of cuprate (Scheme 29). Likewise, the lower homologs (149) and (151), both of which are relatively easy to prepare in optically active forms, can be readily converted into homoallylic and bishomoallylic alcohols (150) and (152) respectively. An ester unit can also be incorporated into the cuprate functions thus, addition of a mixed lithium cuprate, RCuYLi , to ethyl propiolate gives the cuprates (153), which add to epoxides to give unexpectedly the (Z)-crotonates (154). Such isomerization is not uncommon with vinyl carbanions in general, and is obviously a limitation when isomeric mixtures are produced. 

The types of enzymes used by organic chemists vary widely and include such well-known biocataiysts as lipases, esterases, oxidoreductases, oxinitrilases, transferases and aldolases [4]. An example which illustrates the industrial application of a lipase concerns the kinetic resolution of a chiral epoxy ester used as the key intermediate in the synthesis of the calcium antagonist Diltiazem, a major therapeutic in the treatment of high blood pressure [6] (Fig. 1). In developing the industrial process for the production of this drug, many different lipases were screened, but only the bacterial lipase from Serratia marescens showed both a sufficiently high activity and enantioselectivity. The intermediate is produced industrially on a scale of 50 tons/year. 

Resins. The epoxy ester was prepared from one of the solid grades of epichlorohydrin/bisphenol-A type resin. The resin was first esterified with benzoic acid to 40% of the available esterifiable groups. The re-... 

Table 17. Mechanical properties of composites made of the PAFO cured epoxy compounds (glycidyl ester type)...

Chem. Deserp. Epoxy ester resin (soya oil type) in xylene Uses Epoxy for primers/coatings for metal surfs., floor finishes, elec, insulating coatings, OEM coatings, coil coatings, metal deco finishes, aerosol finishes Features General purpose... 

Chem. Descrip. Epoxy ester resin (TOFA oil type) in Aromatic 100/Aro-matlcISO blend... 

Epoxy esters. Similar solvents are used as for alkyds, e.g. white spirit or xylene, depending on their type and amount of fatty acid, eventually with a small amount of alcohol. 

Electrodeposited resins based on epoxy resins can be of both the anodic and cathodic types. The anodic types based on maleinized epoxy esters have already been mentioned in this chapter. Cathodic electrodeposition resins may be illustrated by the reaction product of epoxy resin with diethylamine ... 

Water-based epoxy resins not applied by electrodeposition are mostly of the anodic type and maleinized epoxy esters are frequently used. Another class is the epoxy acrylic graft copolymer, where the epoxy resin is rendered water-soluble by attaching side chains of acrylic polymer containing a high amount of methacrylic acid. The process of grafting is similar to that of chain transfer (p. 67), where acrylic chains are attached by hydrogen abstraction. This process is illustrated in Fig. 14.2, where C- represents a radical site, and represents an extended acrylic chain containing both methacryclic acid and styrene components. 

---