Carboxy-functional polyesters

The reaction system consisting of acid (i.e., carboxy-functional) polyester resins and epoxy resins is important for powder coatings [2.84]. 

Glycidyl Esters. Glycidyl ester resins were originally developed for electrical applications. Glycidyl esters of phthalic acid, hexahydro phthalic acid, terephthalic acid or trimellitic acid (e.g. Araldite PY 284, PT 910) cured with carboxy functional polyesters or polyacrylates at elevated temperatures give coating with both excellent colour stability and outdoor resistance. 

The most important combinations of epoxy resins and curing agents are summarized in Table 2.6. Depending on their molecular mass, bisphenol A epoxy resins can be cured by polyaddition via their epoxy or hydroxyl groups. Polyamines, poly thiols, and polyisocyanates are suitable for room temperature cure. Polyanhydrides, polyphenols, acids, and carboxy-functional polyesters are suitable for hot cure. 

Acids and Carboxy-Functional Polyesters. Curing of epoxy resins with acids and carboxy-functional polyesters requires heat. Industrially, these systems are most important in the formulation of powder coatings more than 70% of powder coatings are based on epoxy resins and carboxy-functional polyesters (see also Sections 3.4.2 and 3.4.3). 

Powder coatings based on aromatic epoxy resins have high chemical and mechanical resistance, but are not resistant to weathering. To obtain weather-resistant powders, triglycidyl isocyanurate (Araldite PT 810, Ciba-Geigy Tepic, Nissan) must be used as the epoxy component with carboxy-functional polyesters. 

Thus, in alkyd, polyester, and epoxy coatings applied to CRS, phosphatized steel, and aluminum, the use of ZAs APG (aminofunctional) and CPG (carboxy-functional) has allowed for the virtual elimination of blister formation and corrosion after 300 h of salt fog exposure. The use of multifunctional ZAs in a Kraton base adhesive has allowed for a 52% increase in T-peel strength on EPDM rubber when compared with the same adhesive containing aminofunctional silane. Incorporation of mercaptofunctional ZA into crosslinkable elastomers has... 

Yang, Y Lu, W Zhang, X., Xie, W Cai, M., and Gross, R.A. (2010) Two-step biocatalytic route to biobased functional polyesters from co-carboxy fatty acids and diols. Biomacromolecules, 11 (1), 259-268. 

On-line coupling of pyrolysis, gas chromatography, and mass spectrometry is a quick and elegant method for the qualitative detection of monomer units in many resins (e.g., polyesters, polyurethanes, phenolic resins, and polyacrylates). Identification of comonomers of polyacrylates, including hydroxy-functional and carboxy-functional monomers, is facilitated if the sample is silylated before pyrolysis [10.30]. 

Polyurethane dispersions can also be prepared by a nonisocyanate process (35). An aliphatic polyester diol is reacted with a bis(2-hydroxypropyl carbamate), a triol, and a transesterification catalyst, such as dibutyltin oxide. Carboxy functionality is then introduced by reacting some of the remaining hydroxy groups with an anhydride. 

Fourier transform near-infrared spectroscopy had been used to determine traces of hydroxy and carboxy functional groups and water in polyesters. Bowden and co-workers [25] monitored the degradation of PVC using Raman microline focus spectrometry. They demonstrated that PVC decomposition is accompanied by the formation of modal polyene chains containing 11-12 or 13-19 double bonds. Bloor [26] has discussed the Fourier transform Raman spectroscopy of polydiacetylenes. Koenig [27] discusses results obtained by the application of infrared and Raman spectroscopy to polymers. 

DWI external coatings are split between acrylic and polyester systems, both of which contain carboxy functionality, neutralised with an amine such as dimethylethanolamine. Current developments in DWI basecoat technology are towards hybrid acrylic polyester water systems. The acrylic portion provides good pigment dispersion properties, whilst the polyester will give improved performance during the spin necking operation. 

If the polyester synthesis is performed with equimolar amounts of diol and diacid, then, in addition to hydroxy, carboxy-terminated oligomers, dihydroxy- and dicarboxy-terminated oligomers are formed, as shown below. In a thermodynamic equilibrium, the molar ratios of the three functionality fractions should be 2 1 1, respectively. 

The method of choice, however, is the reaction of (137) with benzenesulfonyl chloride in pyridine at low temperature (equation 49). This conversion proceeds via (138) with strict retention of configuration and is compatible with a variety of substituents (Table 10). ° However, it fails for small substituents (1371 and 137m) in which case only polyesters are formed. In cyclic systems like (140) 3-lactone formation cannot occur if the carboxy and the hydroxy functions are trans (equation SO) In this case the di-... 

Simple azo-compounds (AIBN or AIBMe) have also been used to produce telechelic polymers. The nitrile and ester functions can be elaborated to reactive carboxy, hydroxy or amino groups and used in polyester or polyurethane formation (e.g. Scheme 7.15). Functionalities (number of end groups/molecule) of... 

DuPont workers have described (7) a wide variety of tractabilizing molecules and the thermotropic polyesters derived therefrom. Their research has focused for the most part on ring substituted monomers such as chloro, methyl or phenyl substituted hydroquinone and swivel" or linked ring molecules, examples of which are 3,4 or 4,4 functionally (hydroxy or carboxy) disubstituted diphenyl ether, sulfide or ketone monomers. Use of the parallel offset or crankshaft" geometry provided by 2,6 functionally disubstituted naphthalene monomers has been the major thrust of the Celanese Corporation development of easily processed, high performance wholly aromatic thermotropic polyesters. 

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