Polyesters alcoholysis

The processes of polyester alcoholysis/glycolysis have been extensively investigated and commercialized. For a review of these methods, see [1,14]. 

Saturated polyesters and saturated alkyds cannot undergo such modification with vinyl monomers but can be modified with other polymers such as silicone resins by alcoholysis. Here outdoor durability is considerably improved. 

Thus, a polyester with the ring in the backbone can be prepared by the Friedel-Crafts polyalkylation of vinyl 2-furoate. BF3 Et20 gave similar results at room temperature in methylene chloride. Structure 30 was arrived at by spectroscopy and by alcoholysis of the polymers. 

During their synthesis esters and polyesters can be modified by the following side reactions alcoholysis, aridolysis, ester interchange, hydrolysis. 

Polyesters have been obtained in organic medium by polyesterification of hydroxy acids,328,329 hydroxy esters,330 stoichiometric mixtures of diols and diacids,331-333 diols and diesters,334-339 and diols and cyclic anhydrides.340 Lipases have also been reported to catalyze ester-ester interchanges in solution or in die bulk at moderate temperature.341 Since lipases obviously catalyze the reverse reaction (i.e., hydrolysis or alcoholysis of polyester), lipase-catalyzed polyesterifications can be regarded as equilibrium polycondensations taking place in mild conditions (Scheme 2.35). 

Figure 10.4 Four major polyester depolymerization processes (hydrolysis, alcoholysis, acidolysis, and aminolysis).

Chemoenzymatic synthesis of alkyds (oil-based polyester resins) was demonstrated. PPL-catalyzed transesterification of triglycerides with an excess of 1,4-cyclohexanedimethanol mainly produced 2-monoglycerides, followed by thermal polymerization with phthalic anhydride to give the alkyd resins with molecular weight of several thousands. The reaction of the enzymatically obtained alcoholysis product with toluene diisocyanate produced the alkyd-urethane. 

In the polyurethane industry, the polymeric glycols are prepared by anionic polymerization of epoxides such as ethylene oxide and propylene oxide. Poly(tetra-methylene glycol), which was prepared by polymerization of tetrahydrofuran, was subjected to chain extension by reaction with diisocyanate (polyurethane formation) and with dimethyl terephthalate (polyester by alcoholysis). 

Lipase Transesterification and direct esterification (inch polyester synthesis) Ring-opening polymerization of 8-caprolactone Hydrolysis alcoholysis acetylation Higher stability of enzyme greater activity catalyst recyclable sometimes higher enantio- and regio-selectivity compared with VOCs... 

The alcoholysis of the polyesters of propjolacionei<>> and their amlnolysis by dirnethyl- or diethylominc take place in the peecnee of a trace of sulfuric acid this makes it possible to obtain the eelem and amides of hydracrylic acid, which are difiicalt to prepare from l.hc add itself. 

Transesterification (also known as ester exchange, ester interchange, or ester alcoholysis) is the most important of the esterification reactions. Polyesters of relatively low molecular weight (around 2000) prepared from aliphatic dicarboxylic acids and glycols are most commonly made by direct esterification (Section 5.2) with or without addition of an external acidic catalyst. Phosphoric acid, p-toluenesulphonic acid, and antimony pentafluoride have been used as catalysts. The preparation of PET by the direct esterification of TA with ethylene glycol was not practical until the... 

By chemical recovery of polyester [poly(ethylene terephthalate) (PET)] (Chapter 16) and PU wastes, by alcoholysis or by aminolysis (Chapter 20), new polyols are obtained that can be used in rigid PU foam fabrication. The vegetable oil polyols, obtained by chemical transformation of the double bonds in vegetable oils in various hydroxyl groups are a very attractive route to obtain polyols from renewable resources (Chapter 17). 

Ester Exchange. The most practical methods for the preparation of high molecular weight polyesters involve ester exchange reactions. The simplest exchange method involves a catalyzed alcoholysis reaction between a diol and a dicarboxylic acid ester with elimination of the alcohol ... 

Whinfield and Dixon, in UK, developed polyethylene terephthalate fibers (Dacron, Terylene). This first Dacron polyester plant went into operation in 1953. Easter interchange (also known as ester exchange or alcoholysis) was once the preferred method for making polyethylene terephthalate (PET) because... 

The hetero-chain polymers, notably the polyesters, polyamides and polyurethanes, can also act as a source of new monomers or oligomers by hydrolysis and alcoholysis. This recycling process (sometimes called... 

Alcoholysis diacetate ester of polytetramefhylene ether + alkanol = polytetramethylene ether glycol (PTMEG) + alkanol acetate ester alkali metal oxide or alkaline earth metal oxide in the presence of hot methanol PTMEG is used to make polyesters, polyurethanes etc. complete conversion of diester. [86]... 

The solvolytic processes hydrolysis, alcoholysis, glycolysis, and aminolysis are suitable for recycling of products of polycondensation and polyaddition [13]. Since these are balanced-reaction processes, the primary material can be broken down into its monomers at a high temperature and with appropriate additives. A differentiation is drawn between summative and selective solvolytic processes. These processes are applied to polyesters, st5renics, and pol3mrethanes on a large scale as of today, and other (selective) polymers solvolysis solutions are under development. 

Properties Wh. powd. insol. or limited sol. in most org. soivs. m.p. 174 C Precaution Combustible Uses Alcoholysis catalyst for alkyds and polyesters specialty greases and lubricants drier in food-contact coatings Regulatory FDA 21CFR 175.300 Manuf./Distrib. CasChem http //www. rutherfordchemicals. com Lithium silicate... 

Vegetable oil-based polyesters 103 Monoglyceride / alcoholysis process... 

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

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