Celanese method

Chain growth polymerizations very often contain a double bond however, cyclic ethers will polymerize in this manner [5], POM (polyoxymethylene) made by the Celanese method shown in Figure 3.6 is an example of a cyclic ether with this method. The Celanese route for the production of polyacetal yields a more stable copolymer product via the reaction of trioxane, a cyclic trimer of formaldehyde, and a cyclic ether (e.g., ethylene oxide or 1,3 dioxalane). 

The ketene—crotonaldehyde route through polyester with various modifications and improvements is reportedly practiced by Hoechst Celanese, Cheminova, Daicel, Ueno, Chisso, Nippon Gohsei, and Eastman Chemical Company. Differences in thein processes consist mosdy in the methods of polyester splitting and first-stage purification. Production of the potassium salt can be from finished sorbic acid or from a stream in the sorbic acid production route before the final drying step. Several patents on the process for producing sorbic acid and potassium sorbate from this route are given in the hterature. 

Acetic acid has been produced in relatively large quantities for more than 100 years. The changes in the methods used for its production over this period reflect some of the underlying general trends in the chemical industry. It was originally produced via fermentation, as were many other organic chemicals in the early days of the chemical industry. The first major synthetic process for acetic acid was based on the hydrolysis of acetylene to acetaldehyde catalyzed by mercuric ion. This process was the dominant method of production for more than 40 years, until 1955— 1960, when two new processes were developed which have dominated the acetic acid markets in the past 20 years. Celanese in the United States and British Petroleum in Europe introduced short-chain paraffin oxida-... 

Nelsen, S., Golder, M. and DeStio, P., Method and compositions for toughening polyester resins, US Patent 6020414 (to Hoechst Celanese Corporation, Somerville, NJ), 2000. 

Elango, V. (1990) Method for producing ibuprofen, Eur Patent 400 892 (Cl. C07c57/30), Chem Abstr. 114 205780, to Hoest Celanese and Boots. 

Currently the global production of hexamethylenediamine exceeds 1.2 Mt/a and production (e.g. ICI, BASF and Rhone-Poulenc in Europe) is based on the hydrogenation of adiponitrile, largely obtained by catalytic addition of HCN to butadiene. Celanese produced hexamethylenediamine by reaction of ammonia with hexane-1,6-diol, coming from the hydrogenation of adipic acid. However, production by this method was abandoned in 1984. 

Improvements in existing processes accompagnied by new techniques. The first edition of this book presented 70 processes. It now discusses 140. Admittedly these are not all innovations. Many of them are different versions of the same chemical reaction or of an already existing separation method. Others, more innovative, only made headway slowly their industrial penetration was hindered by the slowdown in economic expansion new solvents in extractive distillation for benzene production, metathesis of olefins (Shell), olefins for oxo synthesis (Dimersol, Instituc Franfais du Pitrole), adiponitrile by direct hydrocyanation of butadiene (Dm Pont de Nemours), or by the conversion of 1,6-hexanediol (Celanese), laur IIactam from cyclododecane [ATO, Huls). 

An elegant method for the production of ihuprofen, 19, was developed hy Hoechst-Celanese. This method involves two steps catalytic hydrogenation and catalytic carhonylation [10]. 

Carbonylation of methanol catalyzed by soluble Group IX transition metal complexes remains the dominant method for the commercial production of acetic acid. The Monsanto process stands as one of the major success stories of homogeneous catalysis, and for three decades it was the preferred technology because of the excellent activity and selectivity of the catalyst. It has been demonstrated by workers at Celanese, however, that addition of iodide salts can significantly benefit the process by improving the catalytic reaction rate and catalyst stability at low water concentrations. Many attempts have been made to enhance the activity of... 

In a 40.000 tyear plant in the United States, Celanese employed a method for synthesizing bexamethylene diamine starting, like the others, with cyclohexane, but using 1,6-hexanediol, HOCH2-(CH2)A—CH2OH, as an intermediate. In this process, the cyclohexane is first oxidized at 150°C and 33 106 Pa absolute to a mixture of adipic acid and o>-hydroxycaproic add. These adds are esterified by reaction with a fraction of the hexanediol previously produced. 

Dobbins, J.T. Jr Discussion of methods for determination of polynuclear aromatic hydrocarbons (with Celanese research persoimel) RDM, 1968, No. 62, October 10, see www.ijrtdocs.com 500604311 4 314. 

Polyacetal can be divided into two basic types, acetal homoploymer and acetal copolymer. Both homopolymer and copolymer are available in a range of molecular weights (M = 20 000-100 000). The homopolymer is a polymer of formaldehyde with a molecular structure of repeated oxymethylene units (Staudinger, 1932). Large-scale production of polyformaldehyde, i.e. polyacetal, commenced in 1958 in the USA (US Patent 2 768 994,1956) (British patent 770 717,1957). Delrin (1959) was the first trade mark for this polymer by Du Pont Company. The copolymers were introduced by the Celanese Corporation of America, and the first commercial product named Celcon (1960). One of the major advantages of copolymerization is to stabilize polyacetal because the homopolymer tends to depolymerize and eliminate formaldehyde. The most important stabilization method is structural modification of the polymer by, for example, copolymerization with cyclic ether. 

Acetal polymers, also known as POM or polyacetal, are formaldehyde-based thermoplastics that have been commercially available since the 1960s. Polyformaldehyde is thermally unstable. It decomposes on heating to yield formaldehyde gas. Two methods of stabilizing polyformaldehyde for use as an engineering polymer were developed and introduced by DuPont, in 1959, and Celanese in 1962. 

The method of shear loading of the specimen end was used in the original Celanese test method [83], where the tabbed specimen is held in conical grips, held in tapered sleeves accommodated in an outer cylinder (Figure 17.55). A load applied to the sleeve will be transmitted to the specimen by shear through the specimen and grips. This has been adopted in a slightly modified form as ASTM D 3410. 

Figure 17.55 The Celanese compression test. Source Reprinted from Courtaulds Grafil Test Methods.

Acetal polymers are formed from the polymerization of formaldehyde. They are also given the name polyoxymethylenes (POMs). Polymers prepared from formaldehyde were studied by Staudinger in the 1920s, but thermally stable materials were not introduced until the 1950s, when DuPont developed Dehin. Hompolymers are prepared from very pure formaldehyde by anionic polymerization as shown in Fig. 2.1. Amines and the soluble salts of alkali metals catalyze the reaction. The polymer formed is insoluble and is removed as the reaction proceeds. Thermal degradation of the acetal resin occurs by unzipping with the release of formaldehyde. The thermal stability of the polymer is increased by esterification of the hydroxyl ends with acetic anhydride. An alternative method to improve the thermal stabihty is copolymerization with a second monomer, such as ethylene oxide. The copolymer is prepared by cationic methods developed by Celanese and mar-... 

Threaded-roll process n. A high-speed method developed by Celanese for converting crimped continuous filament tow into highly bulked, uniformly spread webs of up... 

---