Accelerators and antioxidants

Millingen has described a thin-layer chromatographic method for the identification of accelerators and antioxidants in nonvulcanized (natural) rubber compounds (Method 41). This procedure discusses interference from other compounding ingredients and describes, in detail, means for overcoming this. 

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Types of Latex Compounds. For comparison with dry-mbber compounds, some examples of various latex compounds and the physical properties of their vulcanizates are given in Table 23. Recipes of natural mbber latex compounds, including one without antioxidant, and data on tensile strength and elongation of sheets made from those, both before and after accelerated aging, are also Hsted. The effects of curing ingredients, accelerator, and antioxidant are also Hsted. Table 24 also includes similar data for an SBR latex compound. A phenoHc antioxidant was used in all cases. 

The largest user of phenol in the form of thermosetting resins is the plastics industry. Phenol is also used as a solvent and in the manufacture of intermediates for pesticides, pharmaceuticals, and dyestuffs. Styrene is used in the manufacture of synthetic rubber and polystyrene resins. Phthalic anhydride is used in the manufacture of DMT, alkyd resins, and plasticizers such as phthalates. Maleic anhydride is used in the manufacture of polyesters and, to some extent, for alkyd resins. Minor uses include the manufacture of malathion and soil conditioners. Nitrobenzene is used in the manufacture of aniline, benzidine, and dyestuffs and as a solvent in polishes. Aniline is used in the manufacture of dyes, including azo dyes, and rubber chemicals such as vulcanization accelerators and antioxidants. 

Applications As the basic process of electron transfer at an electrode is a fundamental electrochemical principle, polarography can widely be applied. Polarography can be used to determine electroreductible substances such as monomers, organic peroxides, accelerators and antioxidants in solvent extracts of polymers. Residual amounts of monomers remain in manufactured batches of (co)polymers. For food-packaging applications, it is necessary to ensure that the content of such monomers is below regulated level. Polarography has been used for a variety of monomers (styrene, a-methylstyrene, acrylic acid, acrylamide, acrylonitrile, methylmethacrylate) in... 

Aniline is an aromatic amine used in the manufacture of dyes, dye intermediates, rubber accelerators, and antioxidants. It has also been used as a solvent, in printing inks, and as an intermediate in the manufacture of pharmaceuticals, photographic developers, plastics, isocyanates, hydroquinones, herbicides, fungicides, and ion-exchange resins. It is produced commercially by catalytic vapor phase hydrogenation of nitrobenzene (Benya and Cornish 1994 HSDB 1996). Production of aniline oil was listed at approximately 1 billion pounds in 1993 (U.S. ITC 1994). Chemical and physical properties are listed in Table 1-2. 

N-Nitroso compounds occur in many operations in the rubber industry. Some nitrosamines (nitrosodiphenylamine, N-N-dinitrosopentamethylenetetramine, polymerized N-nitroso 2,2,4-trimethyl-l,2-dihydroquinoline and N-methyl-N-4-dinitroso aniline) are used as organic accelerators and antioxidants in the production of rubber and often the products are found to be contaminated with such compounds [19]. 

Uses Aniline is an oily liquid used in the manufacture of dyestuffs, intermediates for dyestuffs, and manufacture of rubber accelerators and antioxidant substances. Aniline has been extensively used as an intermediate in the manufacture of plastics, pharmaceuticals, pesticides, isocyanates, and hydroquinones. Occupational exposure to aniline is extensive and as diverse as its industrial uses. Workers associated with the manufacturing of acetanalide bromide, coal tar, colors and dyes, leather, disinfectants, nitraniline, perfumes, rubber, and photographic materials become victims of adverse effects from aniline. 

These are easily prepared by the reaction of amines with carbon disulfide (1) in the presence of alkali (Scheme 17).2 The synthesis of dithiocarba mates (4) was first reported by Debus in 1850. Dithiocarba mates (4) form metal chelates, and sodium dimethyl dithiocarbamate is used in quantitative inorganic analysis for the estimation of metals, e.g. copper and zinc. Dithiocarba mates are also employed as vulcanisation accelerators and antioxidants in the rubber industry, and as agricultural fungicides.3 The parent dithiocarbamic acids are unstable, decomposing to thiocyanic acid and hydrogen sulfide however, the salts and esters are stable compounds. Dithiocarba mates (4) are oxidised by mild oxidants to the thiuram disulfides (38) (Scheme 17). 

Use Rubber accelerators and antioxidants, dyes and intermediates, photographic chemicals (hydroqui-none), isocyanates for urethane foams, pharmaceuticals, explosives, petroleum refining, diphenyl-amine, phenolics, herbicides, fungicides. 

Uses Intermediate for paints rubber accelerators and antioxidants dyes and pigments intermediates photographic chems. isocyanates for urethane foams pharmaceutical intermediate explosives petrol, refining phenolics diphenylamine herbicides fungicides epoxy curing agents... 

Accelerated heat aging tests of vulcanized and thermoplastic rubber are conducted according to ISO standard.In respect to plasticized samples it is important to test materials in separate ovens to prevent cross-contamination of samples, which may contain, in addition to a plasticizer, other additives, which may be transferred from sample to sample, such as accelerators and antioxidants. 

Running shoes and athletic gear contain rubber additives, accelerators, and antioxidants, which are common causes of contact allergy. Among the potential allergens are thioureas, thiurams, N-isopro-pyl-N-phenyl-p-phenylenediamine (IPPD), and me-... 

Apart from proteins and amino acids, there are other nitrogenous compounds in the latex. These compounds are mainly amines and the corresponding derivatives, such as choline, methylamine, tetramethylenediamine, pentamethyl-enediamine, ethanolamine and trigonelline. These amine compounds, such as choline, a quaternary saturated amine, have been reported to be an accelerator, and antioxidant for the raw rubber. ... 

METHOD 41 - IDENTIFICATION OF ACCELERATORS AND ANTIOXIDANTS IN NON-VULCANIZED RUBBER COMPOUNDS. THIN LAYER CHROMATOGRAPHY. ... 

This thin-layer chromatographic method determines a range of accelerators and antioxidants in non-vulcanized rubber compounds in amounts down to 5 ppm. 

The unvulcanized rubber sample is extracted with isopropanol to remove accelerators and antioxidants. Isopropanol is removed and the residue dissolved in chloroform and applied to a thin-layer plate. Development with a range of solvent mixtures separates the components which are then detected with a range of spray reagents. Calibration is achieved by applying the procedure to prepared pure standard solutions. 

This method is capable of determining accelerators and antioxidants in unvulcanized rubber compounds with an accuracy of 10%. 

About 8% of aniline production goes directly into the manufacture of rubber accelerators and antioxidants. Aniline is reacted with carbon disulfide to produce crude mercaptobenzothiazole (MBT), which is purified further for use as a rubber accelerator. More importantly, MBT is an intermediate for the manufacture of other, more sophisticated accelerators. 

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