1.4- Cyclohexanedimethanol

This report provides an overview of some of the newer polyester compositions based on CHDM. The basic properties and chemistries of PCT have been described in earlier reviews [9, 13]. The CHDM-based polyesters covered in this review are PCT, PCTG, PCTA, and PETG. These compositions are described in more detail in the sections that follow. 

CHDM is thus a highly versatile monomer for producing polyesters that can be tailored to achieve a wide range of physical properties for a broad range of end-use applications. 

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Glycols such as neopentyl glycol, 2,2,4-trimethyl-l,3-pentaiiediol, 1,4-cyclohexanedimethanol, and hydroxypivalyl hydroxypivalate are used in the synthesis of polyesters (qv) and urethane foams (see Foamed plastics). Their physical properties are shown in Table 1 (1 6). 

Cyclohexanedimethanol is miscible with water and low molecular weight alcohols and appreciably soluble in acetone. It has only negligible solubihty in hydrocarbons and diethyl ether (6). 

Chemical Properties. The chemistry of 1,4-cyclohexanedimethanol is characteristic of general glycol reactions however, its two primary hydroxyl groups give very rapid reaction rates, especially in polyester synthesis. 

Manufacture. The manufacture of 1,4-cyclohexanedimethanol can be accompHshed by the catalytic reduction under pressure of dimethyl terephthalate ia a methanol solution (47,65). This glycol also may be prepared by the depolymerization and catalytic reduction of linear polyesters that have alkylene terephthalates as primary constituents. Poly(ethylene terephthalate) may be hydrogenated ia the presence of methanol under pressure and heat to give good yields of the glycol (see Polyesters) (66,67). 

Cyclohexanedimethanol is produced commercially by Eastman Chemical Co. The price within the United States ia bulk tmckloads as of June 1993 was 99% purity, 2.49/kg. 

Unsaturated resias based on 1,4-cyclohexanedimethanol are useful ia gel coats and ia laminating and molding resias where advantage is taken of the properties of very low water absorption and resistance to boiling water (6). Thermal stabiHty is imparted to molding resias, both thermoplastic (71,72) and thermoset (73—76), enabling retention of physical and electrical properties at elevated temperatures (77). Additionally, resistance to chemical and environmental exposure is characteristic of products made from these resias (78). 

Another area ia which 1,4-cyclohexanedimethanol is commercially important is ia the manufacture of polyurethane foams (see Eoamed plastics). 

MixedPhosphona.te Esters. Unsaturated, mixed phosphonate esters have been prepared from monoesters of 1,4-cyclohexanedimethanol and unsaturated dicarboxyhc acids. Eor example, maleic anhydride reacts with this diol to form the maleate, which is treated with benzenephosphonic acid to yield an unsaturated product. These esters have been used as flame-retardant additives for thermoplastic and thermosetting resias (97). 

The 1,4-isomer has been similarly generated from terephthalonitdle [623-26-7] (56) using a mixed Pd/Ru catalyst and ammonia plus solvent at 125 °C and 10 MPa (100 atm). It is also potentially derived (57) from terephthaUc acid [100-21-0] by amination of 1,4-cyclohexanedimethanol (30) [105-08-8], Endocyclization, however, competes favorably and results in formation of the secondary amine (31) 3-a2abicyclo[3.2.2]nonane [283-24-9] upon diol reaction with ammonia over dehydration and dehydrogenation catalysts (58) ... 

With one exception no other high molecular weight linear polyesters have achieved any sort of commercial significance for films and fibres. The one exception is the condensation polymer of dimethyl terephthalate and 1,4-cyclo-hexylene glycol (also known as 1,4-cyclohexanedimethanol) (Figure 25.19). 

PPF catalyzed an enantioselective polymerization of bis(2,2,2-trichloroethyl) tra 5-3,4-epoxyadipate with 1,4-butanediol in diethyl ether to give a highly optically active polyester (Scheme 9). °° The molar ratio of the diester to the diol was adjusted to 2 1 to produce the (-) polymer with enantiomeric purity of >96%. The polymerization of racemic bis(2-chloroethyl) 2,5-dibromoadipate with excess of 1,6-hexanediol using lipase A catalyst produced optically active trimer and pentamer. The polycondensation of 1,4-cyclohexanedimethanol with fumarate esters using PPL catalyst afforded moderate diastereoselectivity for the cis/trans monocondensate and markedly increased diastereoselectivity for the dicondensate product. 

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. 

All maleimides were synthesized according to standard procedures.16 Maleic anhydride, dimethyl maleate, and diethyl fiimarate were purchased from Aldrich Chemical Co. and used as received. 1,4-Cyclohexanedimethanol divinyl ether (CHVE) and tetraethylene glycol divinyl ether (CHVE) were used as received from International Speciality Products. Bis(4-vinyloxybutyl) isophthalate (IPDBVE) and bis(vinyloxybutyl)succinate (SEGDVE) were obtained from Allied-Signal and used without further purification. All acrylates were used as received from either Aldrich Chemical Co. or Scientific Polymer Products. 2,2-Dimethoxy-2-phenylacetophenone (DMAP) was used as received from Ciba Specialty Chemicals. 

Polyester polyols, 25 464 468 Polyester resin(s), 11 302 coating resins, 7 104-106 cyclopentadiene and dicyclopentadiene applications, 8 230 flammability of, 20 115-116 properties in powder coating, 7 43t standard test methods for, 20 11 It unreinforced, 10 187t weathering of, 20 116 Polyester resin-based powder coatings, organic titanium compounds in, 25 125 Polyester resin composites, 26 762-763 Polyester resin formulations ingredients of, 20 96t unsaturated, 15 511-512 Polyesters, 10 185-189, 497 12 655-656. See also Thermoplastic polyesters Unsaturated polyesters acid resistance of, 20 7-8 antioxidant applications, 3 121 aromatic ionic, 23 722 based on 1,4-cyclohexanedimethanol, 12 674-675... 

CHDA CHDM DMCD EG IPA N NDA PCT PCTA PCTG PET PETG TMCD TPA cis/trans-1,4-cyclohexanedicarboxylic acid cis/trans-1,4-cyclohexanedimethanol dimethyl cis/trans-1,4-cyclohexanedicarboxylate ethylene glycol isophthalic acid dimethyl 2,6-naphthalenedicarboxylate 2,6-naphthalenedicarboxylic acid poly(1,4-cyclohexylenedimethylene terephthalate) dibasic-acid-modified PCT copolyester glycol-modified PCT copolyester poly(ethylene terephthalate) CHDM-modified PET copolyester c .S / ra .v-2,2,4,4-tetramethyl-l,3-cyclobutancdiol terephthalic acid... 

The isosorbide polyurethanes based on the aromatic diisocyanates P(I-TDI) and P(I-MDI), possess more rigid structures with both polymers forming brittle films and brittle compression moldings. Their glass transition temneratures are above their decomposition temperature of 260°C. The thermostability of isosorbide polyurethanes correspond to that of conventional polyurethanes with similar structure based on 1,4-cyclohexanedimethanol for which degradation temperature of 260°C has been determined. 

The polymer limiting oxygen index (LOI) value is 26,5 which corresponds to that of the isosorbide polyurethanes. It is again higher than that of conventional MDI polyurethanes with similar structure based on 1,4-cyclohexanedimethanol (LOI = 20) and indicates lower flammability of cellobiose polymers,... 

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