Trimesoyl chloride

Cortisone acetate has been incorporated into several polyanhydrides (15). The rates of release of cortisone acetate from microcapsules of poly(terephthaUc acid), poly(terephthaUc acid-sebacic acid) 50 50, and poly(carboxyphenoxypropane-sebacic acid) 50 50 are shown in Fig. 8. These microcapsules were produced by an interfacial condensation of a diacyl chloride in methylene chloride with the appropriate dicarboxylic acid in water, with or without the crosslinking agent trimesoyl chloride. This process produces irregular microcapsules with a rough surface. The release rates of cortisone acetate from these microcapsules varied correspondingly with the rate of degradation of the respective polyanhydrides. It can be expected that the duration of release of cortisone acetate from solid microspheres, such as those produced by the hot-melt process, would be considerably longer. 

Trimellitic anhydride, b32 Trimesic acid, b31 Trimesoyl chloride, b33 T rimethoxymethy lsilane, m455 Trimethylacetaldehyde, d677... 

A variant of this membrane was then made by replacing the isophthaloyl chloride with its triacyl chloride analog, trimesoyl chloride (benzene-1,3,5-tricarboxylic acid chloride)(21,22). 

The trimesoyl chloride could be mixed with isophthaloyl chloride to produce copolyamide barrier layers. Salt rejections toward synthetic seawater improved as the isophthalamide content of the barrier layer Increased. Surprisingly, membrane flux passed through a peak rather than simply declining as a function... 

Table 2. Effect of the Isophthaloyl Trimesoyl Chloride Ratio on the Performance of NS-300 Membranes in Reverse Osmosis Tests...

Preparation of Linear and Star Nylon 6. The star-branched initiator, trimesoyl-tris-caprolactam (TTC) 6 was synthesized from the commercially available trimesoyl chloride 5 using the route shown in Figure 2. (6) Trimesoyl acid chloride in benzene was slowly added to a stirring solution of e-caprolactam, pyridene, and benzene. After addition was complete, the solution was heated to 70° C for 30 minutes to assure conversion to the initiator species. Single and difunctional analogs were synthesized using the same reaction scheme for direct comparison of the star-branched and linear aromatic initiator systems. 

In pursuit of a chlorine-resistant, non-biodegradable thin-film-composite membrane, Cadotte et al. 97 )03,104 fabricated interfacially the poly(piperazineamide) membrane (NS-300). The interfacially formed piperazine isophthalamide and terephthalamide membranes exhibited high salt rejection (98 %) in sea water tests but their flux was low (Table 8). The replacing of the isophthaloyl chloride with its triacyl chloride analog, trimesoyl chloride improved vastly the flux of the membrane but its seawater salt rejection was low — in the range of 60 70 % (55). The trimesoyl... 

Kawaguchi et al.105) in Teijin Ltd. prepared a similar polyamide composite membrane from piperazine, trimesoyl chloride, and isophthaloyl chloride on a polysulfone support. The membrane exhibited high chlorine-resistance and excellent pressure-resistance. When used for reverse osmosis of an aqueous solution of 0.5% NaCl and NaOCl (available Cl 4 5 ppm) at pH 6.5 7.0, 25 °C, and 42,5 kg/cm2, the water permeation was 1400 and 13301/m2 - day and desalination was 93.4% and 95.7% after 2 and 100 hr, respectively. 

They fabricated another two kinds of composite membranes through the interfacial reaction of triethylenetetramine 106,107). The one was the (3,(3 -dichloroethylether-triethylenetetramine-isophthaloyl chloride-trimesoyl chloride copolymer membrane, which had the water permeation rate of 2400 1/m2 day and desalination rate of 96.8 %. The other was the adipic-triethylenetetramine-isophthaloyl chloride copolymer membrane, which showed the water flux 95.8 1/m2 day and NaCl rejection 99.8 % on the reverse osmosis of a 0.5% aqueous solution at 25 °C and 42.5 kg/cm2. These characteristics for both membranes did not decrease during the continuous operation for 100 500 hr. 

Trimellitic acid, b29 Trimesic acid, b30 Trimesoyl chloride, b32 Trimethylacetaldehyde, d596... 

The chemistry and properties of some of the important interfacial composite membranes developed over the past 25 years are summarized in Table 5.1 [10,12,29,30], The chemistry of the FT-30 membrane, which has an all-aromatic structure based on the reaction of phenylene diamine and trimesoyl chloride, is widely used. This chemistry, first developed by Cadotte [9] and shown in Figure 5.9, is now used in modified form by all the major reverse osmosis membrane producers. 

Figure 5.9 Chemical structure of the FT-30 membrane developed by Cadotte using the interfacial reaction of phenylene diamine with trimesoyl chloride...

Fig. 24 Sytheses of multicydic poly(ether ester)s from trimesoyl chloride and monodisperse oligo(ethylene glycol)s...

Cellulose acetate and linear aromatic polyamide membranes were the industry standard until 1972, when John Cadotte, then at North Star Research, prepared the first interfacial composite polyamide membrane.8 This new membrane exhibited both higher throughput and rejection of solutes at lower operating pressure than the here-to-date cellulose acetate and linear aromatic polyamide membranes. Later, Cadotte developed a fully aromatic interfacial composite membrane based on the reaction of phenylene diamine and trimesoyl chloride. This membrane became the new industry standard and is known today as FT30, and it is the basis for the majority... 

There are a number of combinations for the choice of diamine and acid chloride monomers. For example, if trimesoyl chloride, which has three -COCl groups in an aromatic ring, is mixed with phthaloyl chloride, which has two -COCl groups, crosslinking will form between two main chains. Unreacted -COCl will become -COOH upon contact with water and the membrane will become negatively charged. Monomers with reactive groups other than amine and acid chloride can also be used. 

One approach used by Kawaguchi et al for preparation of the amphoteric membrane was the use of polyethylenimine having part of the amine groups neutralized with hydrochloric acid. The interfacial reactants were trimesoyl chloride (TMC), 3-chlorosulfonyl isophthaloyl chloride (SPC) and pyromellitlc acid chloride (PMC). 

Table IV lists the best performance data obtained for piperazine oligomer membranes interfacially reacted with isophthaloyl chloride. The objective of these tests was to achieve single-pass seawater desalination membranes. As such, the presence of free carboxylate groups was avoided use was made of the trimesoyl chloride or alternate triacyl halides in the oligomer formation step, and diacyl chlorides in the interfacial reaction step. A few samples of seawater desalination membranes were obtained. Best results were seen for piperazine-cyanurate pre-polymers interfacially cross-linked by isophthaloyl chloride, but fluxes were low in view of the operating test pressure of 1500 psi (10 342 kPascal). Also, individual membrane results with piperazine oligomers were equally as erratic as those experienced for piperazine directly. The only notable advantage of the piperazine oligomer approach was the ability to incorporate...

To increase the flux of this membrane, partial or complete substitution of isophthaloyl chloride with trimesoyl chloride was examined.46 47 Dramatic changes in membrane flux and salt rejection were observed. Table 5.3 lists the results of this approach. As the trimesoyl chloride content of the acyl halide reactant was increased from 0 to 100%, seawater salt rejection dropped while... 

The combination of piperazine with trimesoyl chloride in composite membrane form was named NS-300. Trimesoyl chloride leads to a crosslinked polyamide structure. Apparently, however, considerable formation of hydrolyzed carboxylate groups also occurs. This is evidenced by the anion selectivity of the membrane, demonstrated by the sequential salt rejection data in Table 5.4 for a series of salts on test with a single set of membrane specimens. 

A typical recipe for an interfacially formed aromatic polyamide composite membrane comprised a 2.0% aqueous solution of the aromatic diamine and a 0.1% nonaqueous solution of trimesoyl chloride. This recipe was extraordinarily simple, and ran quite contrary to experience with piperazine-based membranes. For example, surfactants and acid acceptors in the aromatic diamine solution were generally not beneficial, and in many cases degraded membrane performance by lowering salt rejection. In contrast, surfactants and acid acceptors were almost always beneficial in the NS-300 membrane system. In the nonaqueous phase, use of isophthaloyl chloride as a partial replacement for trimesoyl chloride had relatively little effect on flux, but tended to decrease salt rejection and increase susceptibility to chlorine attack. 

Figure 5.11 SEM photographs of the surface texture of composite polyamide membranes from aliphatic and aromatic amines (a) uncoated microporous poly-sulfone (b) polyamide from polyethylenimine and trimesoyl chloride (c) tri-ethylenetetramine and trimesoyl chloride (d) 1,3-benzenediamine and trimesoyl chloride (e) 2,4-toluenediamine and trimesoyl chloride (f) 4-methoxy-1,3-benzenediamine and trimesoyl chloride. Note the smooth surface for aliphatic amine-based interfacial trimesamides and the coarse ridge-and-valley structure for aromatic amine-based interfacial trimesamides.

Some hydrolysis of the trimesoyl chloride takes place during membrane fabrication. ESCA studies indicated that approximately one-sixth of the carboxyl groups ere present as ionic carboxylate and five-sixths of the carboxyl groups are present as amides, leading to the above structure. The FT-30 barrier layer is insoluble in sulfuric acid and in all organic solvents, in agreement with the crosslinked nature indicated above. Its chemical structure is somewhat similar to the composition of the duPont Permasep B-9 hollow fiber polyamide, believed to be approximately as follows ... 

The prepolymer approach which worked well for piperazineamide interfacial membranes was not useful in the case of FT-30 and its analogs. Poor solubility of aromatic amide precursors in aqueous media was the main obstacle. A patent application has appeared on the use of prepolymer formed from 1,3-benzenediamine and trimellitic anhydride acid chloride.66 This prepolymer contains a free carboxylate group and is soluble in water as the sodium salt. A membrane is obtained by reaction of this intermediate with trimesoyl chloride, followed by a curing step at 110° to 130°C. Salt rejections of 98.5 to 99.1% on 2,000 ppm sodium chloride solution at 200 psi were obtained fluxes were 4 to 11 gfd. 

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