Oxidation during drying

Because nitrile rubber is an unsaturated copolymer it is sensitive to oxidative attack and addition of an antioxidant is necessary. The most common practice is to add an emulsion or dispersion of antioxidant or stabilizer to the latex before coagulation. This is sometimes done batchwise to the latex in the blend tank, and sometimes is added continuously to the latex as it is pumped toward further processing. PhenoHc, amine, and organic phosphite materials are used. Examples are di-Z fZ-butylcatechol, octylated diphenylamine, and tris(nonylphenyl) phosphite [26523-78-4]. All are meant to protect the product from oxidation during drying at elevated temperature and during storage until final use. Most mbber processors add additional antioxidant to their compounds when the NBR is mixed with fillers and curatives in order to extend the life of the final mbber part. 

Figure 9 suggests that careful control of conditions of activation would be needed for good reproducibility. The level of reproducibility which we secured was fair (see Table IV) but there are factors affecting catalytic activity which we have not identified. We have established that the activity of our samples of chromia did not depend upon trace impurities of other metals nor upon surface oxidation during drying the gel at 110° in the course of preparation of the catalyst. 

Thermosetting polyester resins are used in paints and surface coatings. In these, oxidation during drying forms a cross-linked film, which provides a tough, resistant finish. 

DRI can be produced in pellet, lump, or briquette form. When produced in pellets or lumps, DRI retains the shape and form of the iron oxide material fed to the DR process. The removal of oxygen from the iron oxide during direct reduction leaves voids, giving the DRI a spongy appearance when viewed through a microscope. Thus, DRI in these forms tends to have lower apparent density, greater porosity, and more specific surface area than iron ore. In the hot briquetted form it is known as hot briquetted iron (HBI). Typical physical properties of DRI forms are shown in Table 1. 

Stabilization of Elastomers. Polyunsaturated elastomers are sensitive to oxidation. Stabili2ers are added to the elastomers prior to vulcani2ation to protect the mbber during drying and storage. Nonstaining antioxidants such as butylated hydroxytoluene (1),... 

The mass balance for carbon during dry oxidation of bitumen in our calorimeter can be calculated from the above results in combination with some of our chemical results for oxidized samples reported elsewhere ( 2). This mass balance is summarized in Table IV, where the following relationships have been used ... 

A general approach to evaluating decomposition and oxidation of product during drying follows ... 

It was observed by Desmaroux (Ref 4), Marqueyroi Muraour (Ref 5) and Marqueyrol Loriette (Ref 6) during their studies of DPhA derivatives which impart a dark color to old proplnts, that the color is produced by impurities in ether (used in manuf of proplnt), or by the oxidizing action of air during drying and storage. Their presence is not an evidence that the proplnt has decomposed, but... 

This study supports the hypothesis that high DE maltodextrins and syrup solids permit the formation of encapsulated products with excellent stability to oxidation. Different enzyme-hydrolyzed starches yielded encapsulated orange oils which varied in stability amylomaize and potato maltodextrins exhibited the poorest stabilities while normal corn, waxy corn, cassava, rice, and wheat glucose syrup solids yielded the best and approximately equivalent shelf-lives. Based on oil retention during drying, amylomaize, wheat, rice, and cassava yielded satisfactory products. 

The primary benefit claimed in this patent was the maintainence of fresh flavor in encapsulated citrus oils which otherwise would readily oxidize during storage, yielding objectionable off-flavors. While spray dried flavorings have continued to dominate the dry flavor market, encapsulated products have been gaining market share. Initial studies that led to the work of Swisher (1 ) were done by Schultz et al (2), This work involved the addition of citrus oils to a molten solution of sucrose and dextrose, cooling the solution to form a hard slab similar to rock candy and then grinding the solid to the desired size. 

Concurrent studies in these laboratories (15) indicate that humic acids heated to temperatures around 300°C. (or higher) will, even in the presence of oxygen, tend to lose their acidic functional groups and revert to an essentially coal-like material. In view of this and observations made in the course of the investigations reviewed here, the overall reactions occurring during dry oxidation of coal can be put in the form ... 

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