Fiber grade products

One expedient designed to obtain aM fiber-grade product consists in preparing the prepolymer, bis hydroxyethyl terephthalate, also called Bisbet, and purifying it The pre-polymer is obtained by the reaction of two moles of glycol with one mole of acid ... 

In the early composition of matter, process and product patents that IKC had filed, reference and claims to all types of substituted styrene homopolymers and copolymers in the syndiotactic configuration had been made. These became the practical basis for the development of film and fiber grade products with improved (in this case reduced) crystallization rates from the melt. The incorporation of small amounts of alkyl-substituted styrene monomers led to a new line of products for these markets and applications. The almost complete random copolymer of para-methyl styrene and styrene with these catalysts is the basis of this technology. Once it was discovered that this was effective, it was only a matter of optimizing the melt crystallization rate with... 

In the various appHcations, each type or group of products usually requires a selected asbestos fiber grade (or range of grades). Table 6 Hsts various... 

In the Amoco process, p-xylene is oxidized at 200 °C under 15-20 atm in acetic acid and in the presence of a catalyst consisting of a mixture of cobalt acetate (5% weight of the solution), manganese acetate (1%) and ammonium bromide. Owing to the highly corrosive nature of the reaction mixture, special titanium reactor vessels are required. One of the main difficulties of this process is to remove the intermediate oxidation products such as p-toluic acid or p-carboxybenzal-dehyde which contaminate TPA obtained by precipitation from the reaction medium. A series of recrystallization and solvent extraction apparatus is required to obtain fiber grade TPA with 99.95% purity. The overall yield in TPA is ca. 90% for a 95% conversion of p-xylene. 

The Dynamit Nobel process produces dimethyl terephthalate (DMT) by a complicated series of oxidation and esterification stages (equation 241).83,84,86 In the oxidation section, p-xylene is oxidized at 150°C and 6 atm without solvent and in the presence of cobalt octoate to TPA and p-toluic acid. These oxidation products are sent to another reactor for esterification by methanol at 250 °C and 30 atm. Fiber grade DMT is purified by several recrystallizations, and monoesters are recycled to the oxidation reactor. The overall yield in DMT is about 80%, which is lower than in the Amoco process. However, this process is competitive because it is not corrosive and requires lower investments. It provides high-quality fiber-grade dimethyl terephthalate. 

Description Anhydrous DMA and CO are continuously fed to a specialized reactor (1), operating at moderate conditions and containing a catalyst dissolved in solvent. The reactor products are sent to a separation system where crude product is vaporized (2) to separate the spent catalyst. Excess DMA and catalyst solvent are stripped (3) from the crude product and recycled back to the reaction system. Vacuum distillation (4) followed by further purification (5) produces a high-quality solvent and fiber-grade DMF product. A saleable byproduct stream is also produced. 

Most EO plants are integrated with fiber-grade mono-ethylene glycol (MEG) production facilities. In such an integrated EO/MEG facility, the steam system can be optimized to fully exploit the benefits of high-selectivity catalyst. 

Product quality The SD process has set the industry standard for fiber-grade MEG quality. When EO is produced as a co-product it meets the low aldehyde specification requirement of 10-ppm aldehyde maximum, which is required for EO derivative units. 

Application Production of fiber-grade terephthalic acid (PTA). PTA is the market standard raw material to produce of all types of polyester fibers used in the textile industry. 

Description The general flow diagram for the production of PTA using Eastman Chemical s new proprietary process can be broken down into the two main production lines—the production of polymer-grade terephthalic acid (MTA), followed by a hydrogenation process to produce fiber-grade terephthalic acid (PTA). 

The pressure is released on the exit stream, which simultaneously flashes off much of the excess p-xylene and the acetic acid, and cools the residual solution causing terephthalic acid to crystallize out. Residual acetic acid and p-xylene are removed from the crystals by centrifugation. The crude product acid is then slurried in hot water first for washing, and then for hydrogenation to decolorize any residual traces of colored impurities. It is then recrystallized and dried to give fiber-grade material (m.p. >300 °C) in yields of about 90%. 

The Lummus process converts p-xylene to terephthalic add in a first step by ammo-xidation in the presence of a V20s/AI203-bascd catalyst. Terephthalic nitrile is converted to terephthalic add in three steps. It is first hydrolysed by steam to form ammonium hydrogen terephthalate, and this salt is then pyrolysed to the diadd. The third step consists of a second hydrolysis to convert the amide which may have been formed in the trace state to the add. This technique, which cou d be considered as a promising one, in so far as it allowed the production of fiber-grade terephthalic add without spedal purification, has not yet enjoyed any industrial development... 

Table 13.1 provides an order of magnitude of capital expenditures and various consumptions per ton of product for tbe mam types of process to manufacture dimethyl terephthalate and fiber-grade terephthalic acid. 

Today, both MCC and PC fiber grades are widely used in tabletting. Depending on the composition of the formulation, one or the other cellulose product results in better hardness, friability, and disintegration values. However, the quantity of MCC required to yield comparable tablet properties is normally at least one-third higher than that of PC fibers. Since, because of a more economical production process, the cost of PC fibers is also lower than that of MCC, monetary advantages can be derived from using powdered cellulose. 

In the Chemische Werke Witten process, which was further developed by Dynamit Nobel and Hercules, p-xylene, air and the catalyst are fed continuously into the oxidation reactor, to which recirculated p-methylbenzoic acid methyl ester is also added. Oxidation is effected at a temperature of 140 to 170 °C and a pressure of 4 to 7 bar. The heat of reaction is removed by the vaporization of water and excess p-xylene. The further reaction with methanol is carried out at 200 to 250 °C under slightly raised pressure (20 bar) in the esterification reactor, to keep the reaction mixture in the liquid-phase. The esterification products flow to the crude ester column, where p-methylbenzoic add methyl ester is separated from the crude dimethyl terephthalate. p-Methylbenzoic acid methyl ester is recycled to the oxidation reactor, where oxidation of the second methyl group occurs. The crude dimethyl terephthalate is purified to fiber grade quality by distillation and crystallization from methanol, and subsequent redistillation in a column with around 30 trays. The yield of dimethyl terephthalate (m.p. 141 °C) is generally about 87 mol%. 

All bast (stem) fibers (flax, kenaf, ramie, nettle, hemp, jute) as well as hard fibers (caroa, sisal) are suitable as for reinforcing fibers for natural fiber reinforced polymer composites, if they have a high tensile modulus and sufficient tensile strength. In addition to cultivation site, type and harvest, the properties of natural fibers depend significantly on the fiber extraction method. An extraction to technical fiber grades, i.e. production of bundles with different number of single fibers, is generally sufficient for use in plastics composites. The properties of such extracted fibers may be described as follows ... 

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