Dynamit Nobel

RigidPoly(vinylchloride) Foam. The techniques that have been used to produce rigid vinyl foams are similar to those for the manufacture of flexible PVC foams. The two processes that have reached commercial importance for the manufacture of rigid vinyl foams (246) are the Dynamit-Nobel extmsion process and the Kleber-Colombes Polyplastique process for producing cross-linked grafted PVC foams from isocyanate-modified PVC in a two-stage mol ding process. 

The Dynamit-Nobel extmsion process (252) utilizes a volatile plasticizer such as acetone which is injected into the decompression section of a two-stage screw and is uniformly dispersed in the vinyl resin containing a stabilizer. The resulting PVC foam has low density and closed cells. 

Herm/es/Djnamit JS obe/Process. On a worldwide basis, the Hercules Inc./Dynamit Nobel AG process is the dorninant technology for the production of dimethyl terephthalate the chemistry was patented in the 1950s (67—69). Modifications in commercial practice have occurred over the years, with several variations being practiced commercially (70—72). The reaction to dimethyl terephthalate involves four steps, which alternate between liquid-phase oxidation and liquid-phase esterification. Two reactors are used. Eirst, -xylene is oxidized with air to -toluic acid in the oxidation reactor, and the contents are then sent to the second reactor for esterification with methanol to methyl -toluate. The toluate is isolated by distillation and returned to the first reactor where it is further oxidized to monomethyl terephthalate, which is then esterified in the second reactor to dimethyl terephthalate. 

Eigure 3 is a flow diagram which gives an example of the commercial practice of the Dynamit Nobel process (73). -Xylene, air, and catalyst are fed continuously to the oxidation reactor where they are joined with recycle methyl -toluate. Typically, the catalyst is a cobalt salt, but cobalt and manganese are also used in combination. Titanium or other expensive metallurgy is not required because bromine and acetic acid are not used. The oxidation reactor is maintained at 140—180°C and 500—800 kPa (5—8 atm). The heat of reaction is removed by vaporization of water and excess -xylene these are condensed, water is separated, and -xylene is returned continuously (72,74). Cooling coils can also be used (70). 

During the 1980s some rationalization of capacity occurred in the United States reducing the number of producers to four with the purchase of NeveiUe s chloriaated paraffin business by Dover (ICC). In Europe, Dynamit Nobel ceased as a suppHer. However, elsewhere new companies have commenced manufacture to take advantage of the opportunities in new and emerging economies, particularly in Asia. Some suppHers of chloriaated paraffins are Hsted in Table 2. 

This melt-processable homopolymer was first introduced in 1961 as Kynar by the Pennsalt Chemical Corporation (the company name being subsequently changed to Pennwalt). Other companies now manufacturing similar polymers are Dynamit Nobel (Dyflor), Kureha (KF), Solvay (Solef) and Atochem (Foraflon). 

The oldest of these materials, a poly (trimethylhexamethylene terephthal-amide) was first marketed by Dynamit Nobel in the mid-1960s (Trogamid T). It is a condensation product of trimethylhexamethylenediamine and terephthalic acid (or its dimethyl ester) (Figure 18.25). In practice a 1 1 mixture of 2,2,4- and 2,4,4-trimethyldiamines is used, this being produced from acetone via iso-phorone, trimethyladipic acid and trimethyladiponitrile. 

In the USA producers included Eastman Kodak (Tenite PTMT), General Electric Corporation of America (Valox), and American Celanese (Celanex). In Europe major producers by the end of the decade were AKZO (Amite PBTP), BASF (Ultradur), Bayer (Pocan) and Ciba-Geigy (Crastin). Other producers included ATO, Hills, Montedison and Dynamit Nobel. With the total Western European market at the end of the decade only about 7000 tonnes other companies at one time involved in the market such as ICI (Deroton) withdrew. 

---