Cold rubbers

A chemical reaction employing a catalyst which includes both a reducing agent and an oxidising agent. The system is used in the production of cold styrene-butadiene rubbers. See Cold Rubber. 

The feed characteristics of cold rubber compounds differ considerably from those of hot compound to the extruder and a number of devices were developed to overcome this problem. However, the productivity of the early machines was not as high as for the hot-feed machines. 

As already stated, mastication reactions are not limited to elastomers but can be extended to all polymers in the viscoelastic state. It is thus interesting to note that before the fundamental study of Watson and coworkers on cold rubber... 

Using a similar procedure as is used for cold rubber , various mixtures of 3-6 with styrene and butadiene (ratio by weight 1 3, whereby various amounts of styrene were substituted by the azo compound) have been polymerized in emulsion at 5 °C using a redox initiating system. 

Cold rubber contains fewer branched macromolecules formed by transfer to polymer. This also contributes to its better properties. 

Use Fungicide, food preservative (mold inhibitor), alkyd resin coatings, upgrading of drying oils, cold rubber additive, intermediate for plasticizers and lubricants. 

EDTA is used to prevent pesticides from precipitation in hard-water solutions, to soften water in soap and detergent, and to prevent the catalytic effects of metal ions present in water in the cold rubber SBR process [57]. EDTA attached to iron catalyzes the direct hydroxylation of phenolic compounds [58] it also is the best way to supply iron-deficient citrus trees [59]. Other chelating agents include nitrilotriacetic acid (NTA) made from ammonia and diethylenetriamine pentacetic acid from diethylenetriamine [60]. 

Since polymerization at lower temperatiures results in a superior synthetic GR-S (cold rubber), the tertiary modifiers have an opportunity to play an important role in this process. The tertiary mercaptans are a mixture of mercaptans having 11-13 carbon atoms with an average molecular weight corresponding to about 12 carbon atoms, as compared to commercial lauiyl mercaptan which is 60 per cent normal lauiyl and the balance normal mercaptans having 10,14, and 16 carbon atoms. Tertiary... 

Physical properties Chemigum SL gum stock Natural rubber Cold rubber black tread... 

Solvent type plays a very important role in the reactivity ratios of anionic copolymerization pairs. Hydrocarbon solvents, such as C4-C10 alkanes and cycloalkanes, are commonly used. n-Hexane and cyclohexane are employed in many commercial processes. Except for some SBRs with very specific microstructures made at very low temperatures (T < —20°C), the so-called cold rubbers, most anionic polymerization processes occur at relatively high temperatures (T > 30-100°C), isothermally or semiadiabatically. Number average molecular weights for the blocks vary widely but may be most commonly maintained between 30,000 and 100,000 Da. Once all monomer has been consumed via propagation reactions, a short stopper reactant, typically alcohol or water, is added to the mix to kill the living character of the anion and... 

The most successful method developed for the production of a general-purpose synthetic rubber was the emulsion copolymerization of butadiene and styrene (SBR), which still represents the main process in use today [54,64-69]. The general principles of copolymerization will be discussed in a later section, but it is instructive at this point to examine the other main features of this system. The types of recipes used are seen in Table V [67]. The recipes shown are to be considered only as typical, as they are subject to many variations. It should be noted that the initiator in the SO C recipe (hot rubber) is the persulfate, whereas in the recipe (cold rubber) the initiator consists of a redox system comprising the hydroperoxide-iron(II)-sulfoxylate-EDTA. In the latter case, the initiating radicals are formed by the reaction of the hydroperoxide with the ferrous iron, whose concentration is controlled by the EDTA complexing agent the sulfoxylate is needed to convert the oxidized ferric(III) back to ferrous iron. The phosphate salt serves as a stabilizing electrolyte for the latex. 

Hydroperoxides. Hydroperoxides such as cumene hydroperoxide are used primarily for low-temperature emulsion polymerization of butadiene to make cold rubber. ... 

Cold rubber n. A synthetic rubber made at a relatively low temperature (about 40° F or 4°C) and having greater strength and durability than that made at the usual temperature (about 120°F or 49°C. 

Recently another type of nitrile rubber, cold rubber, such as Hycar 1041 and 1051 (Goodrich), has seen increased usage. 

Polybutadiene (BR rubber) and the random styrene/butadiene copolymer (SBR rubber) are the most widely used polymers. Their principal use is in tyres, which are typically blends of natural/synthetic rubber. BR rubber has good resilience, abrasion resistance and low heat build-up. SBR contains 10-25% styrene which is added chiefly to reduce cost but also to improve wearing and blending characteristics compared with BR alone. BR and SBR are polymerized by a free-radical mechanism as a water emulsion at 50-60 °C (hot rubber) or 0°C (cold rubber). Typical compositions are 70% trans-1,4, 15% cis-1,4 and 15% 1,2. Ziegler systems used in solution polymerization yield an SBR which has higher MW, narrower MWD and higher cis-1,4-content than the emulsion free-radical type. 

Second generation emulsion polymers ( cold rubbers ). 

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