5-sulfoisophthalic acid

It was previously mentioned was that a large number of minor copolymers of PET have been developed over the past 50 years, with the intent of modifying textile fiber properties and processability [2, 3], Of broader interest is that some of these textile modifications, such as PET copolymers with metal salts of 5-sulfoisophthalic acid (SIPA), have their own rich chemistries when the extent of polymer modification is increased beyond textile levels. An example of such a modification is that changing the counterions associated with SIPA can significantly effect the kinetics of polyester transesterification reactions (the... 

As earlier noted, PET has no dye attachment sites for chemically active dyes. It is possible to add ionic dyeability by forming copolymers of PET with monomer species that possess active sites, for example, on a pendant side chain. The most common of these has been the incorporation of a sodium salt of a dicarboxylic acid, e.g. of 5-sulfoisophthalic acid (Figure 12.14). The acidic sulfo group allows the attachment of cationic dye molecules. If both the modified and the unmodified fibers are put into a dye bath containing a mixture of disperse and cat dyes, they will emerge with two different colors. This is useful in the creation of specialty fabrics, e.g. when two different dye types are woven into fabrics with a predetermined pattern. The multicolored pattern emerges upon dyeing. 

Direct copolymerization of sulfonated monomers has been used to synthesize sulfonated poly (benzimidazoles), poly(benzoxazole)s, and poly(benzothia-zole)s. As an example, Kim et al. synthesized poly-(benzthiazole)s from 2,5-diamino-1,4-benzenedithiol dihydrochloride and either 2-sulfoterethphthalic acid sodium salt, 5-sulfoisophthalic acid sodium salt, or 2,4-disulfoisophthalic acid potassium salt in poly-phosphoric acid (PPA), as shown in Figure 34. Similar sulfonated poly(benzimidazole) and sulfonated poly(benzoxazole) ° structures have also been synthesized. A general synthetic scheme for each is shown in Figure 35. The stability of these polymers in aqueous acidic environments appears... 

Since disperse dyes diffuse very slowly into PES fibers, efforts have been made to increase the rate of dye strike by chemical or physical alteration of the fiber. The fiber is also modified to reduce the pilling tendency, to increase shrinkage and elasticity, and to reduce flammability. Such modified fibers exhibit improved dye receptivity. Fibers with improved dyeability can be dyed with disperse dyes at boiling temperature without a carrier or with basic dyes when they are modified with acidic components (5-sulfoisophthalic acid). Fibers of this type are used if dyeing cannot be carried out easily above 100°C (e.g., in the case of floor coverings, articles made of PES-wool blends, stretch materials, and cord). Strongly crimped PES bicomponent fibers are produced for special purposes. These fibers are normally also dyeable at the boil and without a carrier [136, 137, 138],... 

Greater success was achieved by DuPont who copolymerized, the sodium salt of 5-sulfoisophthalic acid into PET to render the polymer dyeable with cationic (basic) dyes. Basic dyeable PET was successfully launched as Dacron 64 in the form of a low-pill staple product [64]. The presence of the sulfonate groups in the polymer chain also acts as an ionic dipolar cross-link and increases the melt viscosity of the polymer quite markedly. Thus, it is possible to melt-spin polymer with IV 0.56 under normal conditions, giving a low-pill fiber variant. The fiber also has a greater affinity for disperse dyes due to the disruption of the PET structure. Continuing this theme, there are deep dye variant PET fibers, often used in PET carpet yarns, which are copolymers of PET with chain-disrupting copolymer units like polyethylene adipate. They have less crystallinity and a lower Tg. therefore, they may be dyed at the boil without the use of pressure equipment or carrier at the cost of some loss of fiber physical properties. 

Several attempts have been made to develop sulfonated polyazoles [148, 149] and polybenzazoles [150-160]. Sulfonated poly-l,3,4-oxadiazoles have been prepared by the interaction of 5-sulfoisophthalic acid with hydrazine sulfate in polyphosphoric acid (PPA) [148,149]... 

A partially sulfonated PBI can be prepared from 3,3 -diaminobenzidine, isophthalic acid, and 5-sulfoisophthalic acid with poly(phosphoric acid) [8]. The reaction takes place at 220 °C for 25 h. In the course of the reaction, the color of the solution changes from ocher to dark brown. Afterwards the polymer is precipitated in water and dried in vacuo. In the course of the preparation of a fuel cell membrane, the poly(phosphoric acid) is hydrolyzed into phosphoric acid due to moisture in air so that the polymer membrane has an acid doping level of 2000. 

DuPont has patented aliphatic/aromatic copolyesters that contain sulfo groups [56-59]. Polyesters that are copolymerised with 5-sulfoisophthalic acid hydrolyse readily. The polyesters are reported to be biodegradable and can be processed at higher temperatures than other biodegradable polymers. These polyesters also offer the cost advantages mentioned earlier for aliphatic/aromatic copolyesters. 

In order to obtain the membrane in which both conductivity and solubility coexist, copolymers containing sulfonic and phosphonic acid groups at the same time were prepared (Schemes 9,10) [55]. As dicarboxyUc adds containing sulfonic acid groups 5-sulfoisophthalic acid monosodium salt (SIA) and 2-sulfoterephthalic acid monosodium salt (STA) were used. 

The majority of polyester fibres are based on poly(ethylene terephthalate) (PET), currently accounting for about 50% of all synthetic fibres produced. Modification of the dyeing behaviour of PET fibres can be achieved by using small quantities of comonomers. For example, use of 2 mol % of the sodium salt of 5-sulfoisophthalic acid gives fibres which are dyeable with cationic dyes. 

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