Synthesis of polyester resins

Prior to 1975, benzene was catalytically oxidized to produce maleic anhydride, an intermediate in synthesis of polyester resins, lubricant additives, and agricultural chemicals. By 1986 all commercial maleic anhydride was derived from oxidation of / -butane. It is expected that / -butane will remain the feedstock of choice for both economic and environmental reasons. 

Synthesis of Polyester Resins Described in Table II. The monomers and 3 wt % of xylene were placed in a 1-L breakaway reaction flask equipped with a thermometer, a Liebig condenser, a mechanical stirrer, an N line and a heating mantle. The mixture was slowly heated under 210 C, with stirring being started as soon as... 

Reaction scheme for synthesis of polyester resin by an alcoholysis process. 

The only other glycol that is fairly common is propylene glycol which has a molecular formula of C3H (OH)2. It is a combustible liquid with a flash point of 210°F, and its major use is in organic synthesis, particularly of polyester resins and cellophane. 

New processes include synthesis of /V-alkylated anilines from olefins and aniline in an inert solvent with at least one catalyst from a range that includes alkali metal alcoholates, alkaline earth metal alcoholates, alkali metal amides and alkaline earth amides36. The uses for /V,/V-dimethylaniline (11) include in the manufacture of polyester resins, sulfur recovery (in copper refining), insecticides and fungicides, dyes, pharmaceuticals, explosives, rubber products, specialty isocyanates and petroleum additives. The /V-ethylaniline (26) is a dye intermediate and rubber additive, and is used for bum control in explosives, while /V,/V-diclhylaniline is used in production of polyester resins, pharmaceuticals, diazo prints (lithographic), and dyes, and as a petroleum additive37. 

Polymer concretes show excellent mechanical properties and chemical resistance compared with conventional cement concretes. Polymer concretes can be cured quickly by the use of curing agents. Thus, the applications of polymer concretes are being increased. One of the popular polymers for polymer concretes is unsaturated polyester (UPE) resin. The properties of UPE resin can be modified by changing its molecular features. For the synthesis of the resin, phthalic anhydride or isophthalic acid as well as maleic anhydride can be employed to modify the mechanical properties or hydrothermal resistance. Terephthalic acid which is also used for the synthesis of poly ethylene terephthalate (PET) enhances the thermal resistance of the cured UPE resin. However, the synthesis of unsaturated polyester resin from terephthalic acid is difficult. One method to synthesize unsaturated polyester from terephthalic acid is the use of recycled PET. 

The chemical participation of lignin macromonomers in polymerization or copolymerization reactions has been focussed mostly on the reactivity of both types of OH groups, and hence in the synthesis of polyesters, polyurethanes and polyethers, although some research has also dealt with their intervention through the unsubstituted aromatic sites in different formaldehyde-based resins in partial replacement of phenol [58, 59]. 

A wide range of chemical agents, catalysts and conditions for the glycolysis of unsaturated polyester resins, used in the manufacture of buttons, have been described in a recent patent.34 In addition to different metal acetates, the following compounds have been proposed to be catalytically active in PET glycolysis sodium methylate, sodium ethylate, sodium hydroxide, methane-sulfonic acid, magnesium oxide, barium oxide and calcium oxide. Different applications of the depolymerization products were described, e.g., preparation of fresh unsaturated polyesters by reaction with maleic acid, maleic acid/ phthalic anhydride or maleic anhydride/terephthalic acid or the synthesis of polyurethane resins by reaction with a diisocyanate. 

Beilstein Handbook Reference) AI3-02247 BRN 1912251 Dimethyl 1,3-benzenedi-carboxylate Dimethyl isophthalate Dimethyl m-phthalate Dimethylester kyseliny isoftalove EINECS 215-951-9 HSDB 6138 Isophthalic acid dimethyl ester Methyl 3-(carbomethoxy)benzoate Methyl isophthalate Morflex 1129 NSC 15313 Uniplex 270. Chemical intermediate in the synthesis of polyesters. Used as a plasticizer, modifies clarity and melting point of PET resins used in films, blow-molded bottles, and similar products. Needles mp = 67.5° bp = 282° d = 1.194 Xm = 280, 288 nm (MeOH) slightly soluble in H2O, Morfiex Unitex. 

Methods of synthesis of polymeric plasticizers are discussed in several pat-ents. ° ° "° Endcapped polyalkylene ethers were prepared for use in polyester resins. Different propanediol derivatives are synthesized to form polyester-type plasticizer. In the synthesis of polyester-type plasticizer it is important to avoid presence of unreacted acids. A second stage reaction is conducted in order to remove the odor from the polyester plasticizer." First, the plasticizer is synthesized in the presence of a molar excess of alcohol, then hydroxyl groups are reacted with mono- or difimctional isocyanates." Polyester plasticizer is also produced from a waste stream of non-volatiles recovered as a by-product of oxidation of cyclohexanone. 

N. Dutta, N. Karak and S. K. Dolui, Synthesis and characterisation of polyester resins based on Nahar seed oil . Prog Org Coat, 2004,49,146-52. 

Frechet and coworkers explored the synthesis of polyester dendrons on solid support. These dendrons, based on 2,2-bis(hydroxymethyl)propanoic acid monomers, were assembled up to the fourth generation on poly(2-hydroxyethyl methacrylate-co-ethylene dimethacrylate) resin and decorated with chiral proline derivatives (Scheme 15.15). T vo methods for preparation of these materials were reported. The solid-phase divergent approach yielded polymer with higher loading but a less precise architecture than the second approach. The second approach, the divergent synthesis of the dendrons in solution, followed by the focal point deprotection and then attachment to the solid support, led to well-defined structures on the polymer, but relatively low loading. 

All polymers must be checked for the presence of residual monomers, which by their nature are reactive, toxic materials. During manufacture, other low molecular weight materials may be unintentionally synthesized from EO and PO, such as acetaldehyde and 1,4-dioxane (from EO), and propionaldehyde, allyl alcohol, allyloxy-2-propanol, and substituted dioxolanes (from PO). Good manufacturing practice requires that these low molecular weight compounds be vacuum stripped from the surfactant at the end of the alkoxylation reaction. Generally, the presence of a high level of one of these is associated with the presence of others, so that it is not necessary to determine each individually for routine quality control. Dioxanes and dioxolanes from surfactant synthesis seem not to be the cause of odor complaints, unlike the similiar family of compounds produced as a byproduct of polyester resin manufacture (52,53). 

Processes have been developed separating pure metaxylene from other Cj aromatics.Metaxylene is a raw material for the manufacture of isophthalic acid. The major outlets for the acid are in the synthesis of unsaturated polyester and alkyd resins, and for the production of isophthalic esters (plasticizers). 

Oxidation of n-hutane to maleic anhydride is becoming a major source for this important chemical. Maleic anhydride could also be produced by the catalytic oxidation of n-butenes (Chapter 9) and benzene (Chapter 10). The principal use of maleic anhydride is in the synthesis of unsaturated polyester resins. These resins are used to fabricate glass-fiber reinforced materials. Other uses include fumaric acid, alkyd resins, and pesticides. Maleic acid esters are important plasticizers and lubricants. Maleic anhydride could also be a precursor for 1,4-butanediol (Chapter 9). 

Since anhydrides are much more reactive than carboxylic acids, reaction kinetics is controlled by the second step. The scope and apphcations of this reaction are the same as direct polyesterification but are practically limited to the synthesis of unsaturated polyesters and alkyd resins from phtliahc and maleic anhydrides (see Sections 2.4.2.1 and 2.4.23). 

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