Rubbers, additives Antioxidants

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. 

Plastic and rubber additives are both commodity chemicals and specialties. The Handbook of Plastic and Rubber Additives [27] mentions over 13 000 products antioxidants and antiozonants amount to more than 1500 trade name products and chemicals [28], flame retardants to some 1000 chemicals [29] and antimicrobials to over 1200 products [30]. 

At Goodyear laser-desorption MS has been used for direct analysis of rubber additives (e.g. antioxidants, antiozonants, vulcanising agents, processing oils, silica fillers, etc.), in situ at the surface of an elastomeric vulcanisate [74,75]. 

Applications Open-column chromatography was used for polymer/additive analysis mainly in the 1950-1970 period (cf. Vimalasiri et al. [160]). Examples are the application of CC to styrene-butadiene copoly-mer/(additives, low-MW compounds) [530] and rubbers accelerators, antioxidants) [531]. Column chromatography of nine plasticisers in PVC with various elution solvents has been reported [44], as well as the separation of CHCI3 solvent extracts of PE/(BHT, Santonox R) on an alumina column [532]. Similarly, Santonox R and Ionol CP were easily separated using benzene and Topanol CA and dilaurylthiodipropionate using cyclohexane ethyl acetate (9 1 v/v) [533]. CC on neutral alumina has been used for the separation of antioxidants, accelerators and plasticisers in rubber extracts [534]. Column chromatography of polymer additives has been reviewed [160,375,376]. 

Potassium carbonate is used in the chemical industry as a source of inorganic potassium salts (potassium silicates, potassium bicarbonate), which are used in fertilizers, soaps, adhesives, dehydrating agents, dyes, and pharmaceuticals. Potassium carbonate used to make potassium lye produces soft soaps, which are liquids or semisolids rather than solids. Other uses of potassium carbonate includes use as a fire suppressant in extinguishers, as a C02 absorbent for chemical processes and pollution control, an antioxidant in rubber additives, and in pharmaceutical formulations. 

Hydrocarbon oxidation may also be considered a free radical chain-type reaction. At elevated temperatures, hydrocarbon free radicals (R) are formed which react with oxygen lo form peroxy radicals (R(X These, in turn, take up a hydrogen atom from the hydrocarbon to form a hydroperoxide (ROOH) and another hydrocarbon free radical. The cycle repeals itself with the addition of oxygen. The unstable hydroperoxides remaining are the major points for degradation and lead to rancidity and color development in oils, fats, and waxes decomposition and gum formation in gasolines sludging in lubricants and breakdown of plastics and rubber products. Antioxidants, such as amines and phenols, are often introduced into hydrocarbon systems in order lo prevent this free radical oxidation sequence. 

In addition to DAA s use in the production of MIBK, DAA also finds use as a specialty reaction intermediate. Hydrogenation of DAA at 100°C and 30 MPa (83) yields hexylene glycol ( 1.43/kg, October 1994), widely used in castor oil-based hydraulic brake fluids and as a solvent. Reaction of -phenetidine [156-43-4] with DAA synthesizes Monsanto s Santoquin (ethoxyquin) [91-53-2] (149), an antioxidant used in animal feeds and also as a rubber additive. Diacetone alcohol (acetone-free) was available at 1.32/kg as of October 1994. 

The specialists in rubber additives are distinctly different from the specialists in additives for plastics, even though the same products are sometimes used in both industries blowing agents (azodicarboamide), phenol antioxidants (BHT, 2246), phosphites (tris-nonylphenyl phosphite). In the first place, additives for elastomers, unlike those which might come into contact with foodstuffs, do not require official approval, which... 

The substituted phenols and cresols constitute about half the total volume of this group. Para-t-butylphenol is produced by the alkylation of phenol with isobutylene. The principal applications for this derivative are in the manufacture of modified phenolic resins for the rubber industry and in surface coatings. BHT is obtained from isobutylene and p-cresol. Technical-grade BHT is an antioxidant for plastics and elastomers, and is a gum inhibitor in gasoline. Food-grade BHT is an antioxidant in edible oils, preserves, and many other foods. 2,6-Di-t-butylphenol is used to produce a wide range of plastics additives, antioxidants, and gasoline additives. 

This product is approved for use by die FDA in a number of food-contact applications as an Indirect Food Additive, including 21CFR175.105 (Components of Adhesives) 21CFR175.125 (Pressure-Sensitive Adhesives) 21CFR177.2600 (Rubber Articles - Antioxidants) and 21CFR178.2010 (Antioxidants and/or Stabilizers for Polymers). 

Argus. [Witco/Argus] Thiodipro-pionates Antioxidants for plastics and rubber, additive for high-pressure lubricants and greases, plasticizer and softening agent antioxidant for edible fats and oils. 

Synonyms N,N -Bis (3,5-di-t-butyl-4-hydroxyhydrocinnamoyl) hydrazine Uses Antioxidant for polyolefins, polyesters, polyamides, PVC, PS, rubbers, cellulosics antioxidant/stabilizer for food-grade polymers in food-pkg. adhesives Regulatory FDA 21CFR 175.105, 178.2010 Manuf./Distrib. Ciba Spec. Chems./Plastic Addit. http //www.cibasc.com, Fairmount Trade Name Synonyms BNX MD-1024 [Mayzo http //www.mayzo.com], Irganox MD 1024... 

Uses In rocket fuels industrial solvent solvent for fibers, plastics rubber accelerator plasticizer for acrylonitrile polymers, rubber gasoline and lubricant additive antioxidant pesticide nematicide inhibition of nitrification in soil mfg. of 1,1-dimethylhydrazine in active metal anode-electrolyte systems (high-energy batteries) prep, of thiocarbonyl fluoride polymers additive in condensers to inc. dielec, const. lubricant and softener in copolymers Regulatory SARA 302a extremely hazardous, 313 reportable CERCLA hazardous substance HAP... 

Methyl oleate N,N,N, N -Tetramethylethylenediamine Triethylamine intermediate, rubber accelerators Allyl mercaptan t-Butylamine Diethylamine Isopropylamine 2-Methylpropanal p-Phenylenediamine Piperidine intermediate, rubber additives Benzoyl chloride intermediate, rubber antioxidants 2-Methylpropanal intermediate, rubber chemicals Benzonitrile Bisphenol A n-Butylamine Cyclopentanone Diethanolamine Ethylene carbonate Ethylenediamine Hexamethyleneimine dl-Limonene 2-Mercaptoethanol... 

Polymethylpentene has a high crystalline melting point of 240°C, coupled with useful mechanical properties at 204°C and retention of form stability to near the melt point. However, the polymer is brittle (fiber or rubber additives are usually advised for improved toughness), ages poorly (the use of antioxidants is recommended), has high gas permeability, and is relatively expensive. Polymethylpentene s chemical resistance is very good and typical of the polyolefins. Its transparency is close to the theoretical optimum for thermoplastics. Polymethylpentene also has excellent electrical properties with power factor, dielectic constant, and volume resistivity on the same order as PTFE fluorocarbon. 

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-... 

Uses food additive antidegradation agent for natural rubber and styrene-butadiene rubber insecticide antioxidant flex-cracking inhibitor post-harvest dip to prevent scald on apples and pears fungicide plant-growth regulator antioxidant in animal feed. ABCD ... 

Lattimer and co-workers [46] have applied MS to the determination of organic additives (antioxidants and antiozonants) in rubber vulcanisates. Direct thermal desorption was used with three different ionisation methods (El, Cl, FI). The vulcanisates were also examined by direct FAB-MS as a means for surface desorption/ionisation. 

LD-MS has proven a uniquely useful technique for the direct characterisation of ruhher-compound surface species. Mass spectra were obtained for intact molecular ions (M+) of organic chemical rubber additives such as the aromatic processing oil, and the aromatic antiozonant and antioxidants incorporated to protect the rubber. MW information from... 

Lattimer et al have very successfully applied mass spectrometry to the determination and identification of organic additives (antioxidants and antiozonants) in rubber vulcanizates (Method 42). A wide variety of components are involved - polymers, fillers, solvents and organic and inorganic additives. Field desorption/ionization (FD/FI) is the most efficient for identifying typical organic additives in rubber vulcanizates. 

Antioxidants. All nitrile rubber producers add an antioxidant to their raw nitrile rubbers. However, where heat resistance and the maximum in durability and service is demanded, additional antioxidant may be added to the cement. Antioxidants commonly used in nitrile rubbers (e.g., amine antioxidants) may be used if staining is not a factor. Antioxidants may also contribute stability and tack. 

The antioxidants used in adhesive formulations are similar to those used in rubber compounding and include materials such as the aromatic amines, substituted phenols, and hy-droquinoes. Elastomer and resin manufacturers typically incorporate antioxidants (0.1-0.3 wt %) in their products for protection during storage and shipment. Adhesive formulators will usually add additional antioxidant to protect the adhesive during processing and use. It is not unusual for an adhesive formulation to contain as many as three or four different types of antioxidants. 

Rubber vulcanisation inhibitor, lubricant additive, antioxidant, fungicide, insecticide, stabiliser. Yellow plates. Mp 66.5°. 

Rubber is a popular closure component, and additives such as vulcanizers, pigments (qv), or antioxidants may leach into the product. In cases where mbber closures are penetrated by needles in dosing, bits of the closure (coring) could enter the product. Thus, such closure components must be sufficiendy tested before use. 

Rubber. The mbber industry consumes finely ground metallic selenium and Selenac (selenium diethyl dithiocarbamate, R. T. Vanderbilt). Both are used with natural mbber and styrene—butadiene mbber (SBR) to increase the rate of vulcanization and improve the aging and mechanical properties of sulfudess and low sulfur stocks. Selenac is also used as an accelerator in butyl mbber and as an activator for other types of accelerators, eg, thiazoles (see Rubber chemicals). Selenium compounds are useflil as antioxidants (qv), uv stabilizers, (qv), bonding agents, carbon black activators, and polymerization additives. Selenac improves the adhesion of polyester fibers to mbber. 

Silicone Heat-Cured Rubber. Sihcone elastomers are made by vulcanising high molecular weight (>5 x 10 mol wt) linear polydimethylsiloxane polymer, often called gum. Fillers are used in these formulations to increase strength through reinforcement. Extending fillers and various additives, eg, antioxidants, adhesion promoters, and pigments, can be used to obtain certain properties (59,357,364). 

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