Dianhydrides

D-Fructose is known to form bimolecular dianhydrides containing a central dioxane ring, when acted upon by aqueous acids. Six such substances have been described 129), A high degree of polymorphism is characteristic of these substances and their derivatives. The first of these 

Another dianhydride of D-fructose was isolated by Wolfrom and Blair 

Jackson and Goergen 133) and Jackson and McDonald 134) have isolated three dianhydrides of D-fructose from the nonreducing residue that remains after the removal of D-fructose from the acid hydrolyzate of inulin 135). On the basis of methylation data 136), structure (III) was assigned to difructose anhydride I. Difructose anhydride III was considered 135) to be di-D-fructofuranose l,2 2,3 -dianhydride. Wolfrom, Hilton, and Binkley 129) believe, on the basis of rotational data, that difructose anhydrides II and III are structural units differing only in the configuration of one of the asymmetric centers on the substituted dioxane ring. 

Two dianhydrides of L-sorbose have been isolated by Wolfrom and Hilton 137). The first of these substances was established by periodate oxidation to be di-L-sorbopyranose 2,T 2, 1-dianhydride and the second as probably L-sorbofuranose-L-sorbopyranose 2,1 2, 1-dianhydride. 

No monomolecular anhydride of a ketohexose has been established they are known in the ketoheptose series. An interesting bicyclic structure containing a meta or 1,3 dioxane ring has been established by Stewart 

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Colourless solid m.p. 79 - C. Forms a quinone, duroquinone, a phenol, durenol and a carboxylic acid, durylic acid. Oxidized to pyro-mellitic dianhydride. 

Aromatic polyimides are the first example we shall consider of polymers with a rather high degree of backbone ring character. This polymer is exemplified by the condensation product of pyromellitic dianhydride [Vll] and p-amino-aniline [Vlll] ... 

See also Pyromellitic acid.) [PHTTiALIC ACID AND OTTiERBENZENEPOLYCARBOXYLIC ACIDS] (Vol 18) Benzene-1,2,4,5-tetracarboxylic dianhydride-3-carboxylic acid [59025-58-0]... 

Inclusion compounds of the Cg aromatic compounds with tris((9-phenylenedioxy)cyclotriphosphazene have been used to separate the individual isomers (43—47). The Schardinger dextrins, such as alpha-cyclodextrin, beta-dextrin, and gamma-dextrin are used for clathration alpha-dextrin is particularly useful for recovering PX from a Cg aromatic mixture (48,49). PyromeUitic dianhydride (50) and beryllium oxybenzoate (51) also form complexes, and procedures for separations were developed. 

Polyimides for use ia molded products and high temperature films can be produced by the reaction of pyromelHtic dianhydride [89-32-7] and 4,4 -diaminodiphenyl ether [13174-32-8] ia DMAC to form a polyamide that can be converted iato a polyimide (13). DMAC can also be used as a spinning solvent for polyimides. AdditionaUy, polymers containing over 50% vinyHdene chloride are soluble up to 20% at elevated temperatures ia DMAC. Such solutions are useful ia preparing fibers (14). 

Miscellaneous Applications. Ben2otrifluoride derivatives have been incorporated into polymers for different appHcations. 2,4-Dichloroben2otrifluoride or 2,3,5,6-tetrafluoroben2otrifluoride [651-80-9] have been condensed with bisphenol A [80-05-7] to give ben2otrifluoride aryl ether semipermeable gas membranes (336,337). 3,5-Diaminoben2otrifluoride [368-53-6] and aromatic dianhydrides form polyimide resins for high temperature composites (qv) and adhesives (qv), as well as in the electronics industry (338,339). 

Synthesis and Properties. Several methods have been suggested to synthesize polyimides. The predominant one involves a two-step condensation reaction between aromatic diamines and aromatic dianhydrides in polar aprotic solvents (2,3). In the first step, a soluble, linear poly(amic acid) results, which in the second step undergoes cyclodehydration, leading to an insoluble and infusible PL Overall yields are generally only 70—80%. 

Numerous diamines and aromatic dianhydrides have been investigated. WhoUy aromatic Pis have been stmctiirally modified by incorporating various functional groups, such as ether, carbonyl, sulfide, sulfone, methylene, isopropjlidene, perfluoroisopropyUdene, bipyridyls, sdoxane, methyl phosphine oxide, or various combinations of these, into the polymer backbone to achieve improved properties. The chemistry and apphcations of Pis have been described in several review articles (4). 

Pis commonly have been synthesized from reactions of pyromellitic dianhydride [26265-89-4] (PMD A) or 3,3H,4 -benzophenone tetracarboxyUc dianhydride [2421-28-5] (B IDA) with a number of diamines like 2,2-bis(4-aminophenyl)propane, 2,2-bis(4-amino-3-methylphenyl)propane, I,I-bis(4-aminophenyl)-I-phenylethane, and 1,1-his(4-amino-3-methy1pheny1)-1-phenylethane (5). The PMDA-based Pis were thermally more stable than the corresponding Pis obtained from BTDA. 

A successful synthesis of novel, soluble aromatic Pis involving 3,4-bis-(4-aminophen5l)-2,5-diphen5lfuran by polymerization with aromatic tetracarboxyhc dianhydrides through the conventional two-step method has been reported (6) (Fig. I). 

Poly(phenylquinoxaline—arnide—imides) are thermally stable up to 430°C and are soluble in polar organic solvents (17). Transparent films of these materials exhibit electrical insulating properties. Quinoxaline—imide copolymer films prepared by polycondensation of 6,6 -meth5lene bis(2-methyl-3,l-benzoxazine-4-one) and 3,3, 4,4 -benzophenone tetracarboxyUc dianhydride and 4,4 -oxydianiline exhibit good chemical etching properties (18). The polymers are soluble, but stable only up to 200—300°C. 

Polyetherimide synthesis has been achieved by reaction of a dianhydride containing an ether linkage with a diamine, reaction of a diamine containing an ether linkage with a dianhydride, or nucleophilic displacement of halo or nitro groups of a bisimide by bisphenol dianion (19,20). Such Pis exhibit good thermal stabiUty and melt processibiUty. 

Silicon-containing Pis, useflil as insulation and protective materials, demonstrate adhesion to fibers, fabrics, glass, quartz, and carbon (36). The synthetic method used is the reaction of the silicon-containing dianhydride with diamines. 

The dianhydride of 1,4,5,8-naphthalene tetracarboxyhc acid [81-30-1] has been of research interest for the preparation of high temperature polymers, ie, polyimides. The condensation of the dianhydride with o-phenylenediamines gives vat dyes and pigments of the benzimidazole type. 

Phthahc anhydride (1) is the commercial form of phthaUc acid (2). The worldwide production capacity for the anhydride was ca 3.5 x 10 metric tons ia 1993, and it was used ia the manufacture of plasticizers (qv), unsaturated polyesters, and alkyd resins (qv) (see Polyesters, unsaturated). Sales of terephthahc acid (3) and its dimethyl ester are by far the largest of any of the benzenepolycarboxyhc acids 14.3 x 10 t were produced in 1993. This is 80% of the total toimage of ah. commercial forms of the benzenepolycarboxyhc acids. Terephthahc acid is used almost exclusively for the manufacture of poly(ethylene terephthalate), which then is formed into textiles, films, containers, and molded articles. Isophthahc acid (4) and trimehitic anhydride (5) are commercial products, but their worldwide production capacities are an order of magnitude smaller than for terephthahc acid and its dimethyl ester. Isophthahc acid is used primarily in the production of unsaturated polyesters and as a comonomer in saturated polyesters. Trimehitic anhydride is used mainly to make esters for high performance poly(vinyl chloride) plasticizers. Trimesic acid (6), pyromehitic dianhydride (7), and hernimehitic acid (8) have specialized commercial apphcations. The rest of the benzenepolycarboxyhc acids are not available commercially. 

The physical properties of the acids, the most important anhydrides, and the full methyl esters are summarized ia Tables 2, 3, and4. Detailed Hsts of physical properties for phthaUc acid and its anhydride, terephthaUc acid and dimethyl terephthalate, isophthaUc acid, trimeUitic acid and its anhydride, and pyromeUitic acid and its dianhydride/ are provided under the sections describiag these compounds. 

Table 36. Physical Contants of Pyromellitic Acid and Pyromellitic Dianhydride...

Production, Storage, and Shipment. As noted above, AUco Chemical, Amoco Chemical, Mitsubishi Gas Chemical, and Hbls all produce either the acid or the anhydride using different production techniques. The relatively small production volumes of pyromellitic acid and dianhydride results in both storage and shipment in polyethylene-lined fiber dmms of 22—136-kg capacity. 

Economic Aspects. Prices for pyromeUitic acid were about 14/kg in 1994. The dianhydride sold for about 19—25/kg depending on purity, and prices of the dianhydride ground to a fine 3-p.m size were 2/kg higher (153). Production amounts are not released and are dictated by market needs. The use of some multipurpose units to make this product means that the amounts produced are highly variable. 

Health and Safety Factors. Both pyromellitic acid and its dianhydride irritate skin, eyes, and mucous membranes, and they cause skin sensitization (156). When it comes in contact with moist tissue the dianhydride converts to the acid. Direct contact with should be avoided and protective clothing should be worn in areas where it is used. The LD q for intergastric administration in rats is 2.2—2.6 g/kg (157). In 6-mo experiments, the maximum nontoxic dose was 0.07 mg/kg/d, and it affected the fiver, kidney, and reproductive tract. Precautions against fire and dust explosions as explained in the terephthafic acid section should be foUowed. 

Uses. Pyromellitic dianhydride imparts heat stabUity in applications where it is used. Its relatively high price limits its use to these applications. The principal commercial use is as a raw material for polyimide resins (see POLYIMIDES). These polypyromellitimides are condensation polymers of the dianhydride and aromatic diamines such as 4, -oxydianifine ... 

Because the heat distortion temperature of cured epoxy resins (qv) increases with the functionality of the curing agents, pyromellitic dianhydride is used to cross-link epoxy resins for elevated temperature service. The dianhydride may be added as a dispersion of micropulverized powder in liquid epoxy resin or as a glycol adduct (158). Such epoxies may be used as an insulating layer in printed circuit boards to improve heat resistance (159). Other uses include inhibition of corrosion (160,161), hot melt traffic paints (162), azo pigments (163), adhesives (164), and photoresist compounds (165). 

Pigment Orange 43 [4424-06-0] 71105 Perinone condensation of naphthalene-1,4,5,8-tetracarboxyhc acid dianhydride with o-phenylenediamine, and separation of trans isomer... 

Pigment Red 179 [5521-31-3] 71130 Perylene imidation of perylene 1,6,7,12-tetra-carboxyhc acid dianhydride with methylamine... 

Perylenes. Perylene pigments are either the 3,4,9,10-tetracarboxyhc dianhydride or more often N,N -substituted diknides (Table 7). 

The pigments are manufactured either by reaction of the dianhydride with an amine or N,N -diaLkylation of the diimide. They are characterized by high tinctorial strength, excellent solvent stabiUty, very good weatherfastness, moderate brightness, and range in color from red to violet. An exception is the dianhydride which is not stable to alkah. 

An all aromatic polyetherimide is made by Du Pont from reaction of pyromelUtic dianhydride and 4,4 -oxydianiline and is sold as Kapton. It possesses excellent thermal stabiUty, mechanical characteristics, and electrical properties, as indicated in Table 3. The high heat-deflection temperature of the resin limits its processibiUty. Kapton is available as general-purpose film and used in appHcations such as washers and gaskets. Often the resin is not used directly rather, the more tractable polyamide acid intermediate is appHed in solution to a surface and then is thermally imidi2ed as the solvent evaporates. 

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