Butyl rubber preparation

The most important of the commercial cationic copolymers is butyl rubber prepared from isobutylene and isoprene. Because of its very low air permeability, butyl rubber finds extensive use in tire inner tubes and protective clothing. It is manufactured by low-temperature (— 100°C) copolymerization of about 97% isobutylene and 3% isoprene in chlorocarbon solvents with AICI3 coinitiator (see Table 8.5). More recently, an ozone-resistant copolymer of isobutylene and cyclopentadiene has been marketed. 

Until the mid-1950s the only polyolefins (polyalkenes) of commercial importance were polyethylene, polyisobutylene and isobutylene-isoprene copolymers (butyl rubber). Attempts to produce polymers from other olefins had, at best, resulted only in the preparation of low molecular weight material of no apparent commercial value. 

Chlorobutyl rubber is prepared by chlorination of butyl rubber (chlorine content is about 1 wt%). This is a substitution reaction produced at the allylic position, so little carbon-carbon double unsaturation is lost. Therefore, chlorobutyl rubber has enhanced reactivity of the carbon-carbon double bonds and supplies additional reactive sites for cross-linking. Furthermore, enhanced adhesion is obtained to polar substrates and it can be blended with other, more unsaturated elastomers. 

Butyl latices are prepared by emulsification of butyl rubber. Butyl latex has excellent mechanical, chemical and freeze-thaw stability, and when dried it shows the typical properties of butyl rubber [7]. 

TPEs from blends of rubber and plastics constitute an important category of TPEs. These can be prepared either by the melt mixing of plastics and rubbers in an internal mixer or by solvent casting from a suitable solvent. The commonly used plastics and rubbers include polypropylene (PP), polyethylene (PE), polystyrene (PS), nylon, ethylene propylene diene monomer rubber (EPDM), natural rubber (NR), butyl rubber, nitrile rubber, etc. TPEs from blends of rubbers and plastics have certain typical advantages over the other TPEs. In this case, the required properties can easily be achieved by the proper selection of rubbers and plastics and by the proper change in their ratios. The overall performance of the resultant TPEs can be improved by changing the phase structure and crystallinity of plastics and also by the proper incorporation of suitable fillers, crosslinkers, and interfacial agents. 

Recent trends in protective coatings used on buried pipelines have been away from reinforced hot applied coal tar and asphalt enamels and butyl rubber laminate tapes, particularly where applied over-the-ditch . The more recently developed coatings based on fusion bonded epoxies, extruded poly-ethylenes, liquid-applied epoxies and polyurethanes, require factory application where superior levels of pipe preparation and quality control of the application process can be achieved. 

Problem 31.6 Draw the structure of an alternating segment of butyl rubber, a copolymer of iso-prene (2-methyl-],3-butadiene) and isobutylene (2-methylpropene) prepared using a cationic initiator. 

Butyl rubber (a copolymer of isobutylene and 1-3 mole per cent isoprene) and its halogenated derivatives have unsaturation in the carbon-carbon backbone and consequently do not have as good aging properties as EPDM. There are also reports (9-12) that ozone-resistant butyl rubber with a high degree of unsaturation can be prepared by copolymerization of isobutylene with either cyclopentadiene or 9-pinene. 

Commercial grades of HR (butyl rubber) are prepared by copolymerising small amounts of isoprene with polyisobutylene. The isoprene content of the copolymer is normally quoted as the mole percent unsaturation , and it influences the rate of cure with sulphur, and the resistance of the copolymer to attack by oxygen, ozone and UV light. The polyisobutylene, being saturated, however, naturally confers on the polymer an increased level of resistance to these agencies when compared to natural rubber. Commercial butyl rubbers typically contain 0.5-3.0% mole unsaturation. 

Filled resins, 18 292 Filled silicone networks, 22 570-572 Filler hybrid preparation method, 13 539 Filler loading, 10 430, 457 Fillers, 10 430-434 11 301-321. See also Filled polymers applications of, 11 301-302 butyl rubber applications, 4 448-449... 

Uses Coolant and refrigerant herbicide and fumigant organic synthesis-methylating agent manufacturing of silicone polymers, pharmaceuticals, tetramethyl lead, synthetic rubber, methyl cellulose, agricultural chemicals and nonflammable films preparation of methylene chloride, carbon tetrachloride, chloroform low temperature solvent and extractant catalytic carrier for butyl rubber polymerization topical anesthetic fluid for thermometric and thermostatic equipment. 

Almost all isoprene produced is used in the preparation of polymers and copolymers. cis-Polyisoprene, primarily for vehicle tyres, is the largest application, with styrene-isoprene-styrene (SIS) block polymers being a rapidly growing secondary application. Butyl rubber is a significant third application. World demand for isoprene for monomer use in 1992 was (thousand tonnes) polyisoprene, 827 SIS, 95 butyl rubber, 25 and other uses, 10 (Weitz Loser, 1989 Lybarger, 1995). 

To remove peroxides, wear butyl rubber gloves, laboratory coat, and eye protection. Pour the dioxane (100 mL) into a separatory funnel and shake with a freshly prepared 50% aqueous solution of sodium metabisulfite (20 mL) for 3 minutes. Release the pressure in the funnel at 10-second intervals. Separate the aqueous layer. Retest the dioxane for the continued presence of small amounts of dialkyl peroxides that are not reduced by the metabisulfite treatment. If peroxides are absent, the dioxane can be dried for reuse or packaged for disposal by burning. If peroxides are still present, in the fume hood, place the ether in a 250-mL round-bottom flask equipped with a condenser, and add a solution of 100 mg of potassium iodide in 5 mL of glacial acetic acid and 1 drop of concentrated hydrochloric acid. Reflux gently for 1 hour. Package the ether for disposal by burning.13... 

Small Quantities. Wear butyl rubber gloves,10 laboratory coat, and eye protection. Work in the fume hood. Prepare a dilute (5%) aqueous solution of hydrazine by adding slowly to the appropriate volume of water. For each 1 g of hydrazine, place 120 mL (about 25% excess) of household laundry bleach (containing 5.25% sodium hypochlorite) into a three-necked, round-bottom flask equipped with a stirrer, thermometer, and dropping funnel. Add the aqueous hydrazine dropwise to the stirred hypochlorite solution at such a rate that the temperature is maintained at 45-50oC. The addition takes about 1 hour. Stirring is continued overnight (at least 12 hours). Wash the reaction mixture into the drain.12,13... 

Wear butyl rubber gloves, eye protection, and laboratory coat. A body shield should be available. In the fume hood, prepare a dilute solution (5%) of peroxide by cautiously adding to a large volume of water. Gradually, while stirring, add to a 50% excess of aqueous sodium metabisulfite in a round-bottom flask equipped with a thermometer. An increase in temperature indicates that reaction is taking place. Acidify the reaction if it does not proceed spontaneously. Neutralize the reaction mixture and wash into the drain.25-27... 

Potassium Cyanide Solutions. Wear breathing apparatus, eye protection, laboratory coat, and butyl rubber gloves. Instruct others to keep a safe distance. Cover the spill with a 1 1 1 mixture by weight of sodium carbonate or calcium carbonate, clay cat litter (bentonite), and sand. Scoop the mixture into a container and transport to the fume hood. Slowly, and while stirring, add the slurry to a pail containing household bleach (about 70 mL/g of cyanide). Test the solution for the presence of cyanide using the Prussian blue test. To 1 mL of the solution, add 2 drops of a freshly prepared 5% aqueous ferrous sulfate solution. Boil the mixture for at least 60 seconds, cool to room temperature and add 2 drops of 1 % ferric chloride solution. Add 6 M hydrochloric acid (prepared by... 

Small Quantities. Wear eye protection, laboratory coat, and butyl rubber gloves. Work in the fume hood. Slowly add sodium alkoxide to a pail of water. Neutralize with 6 M hydrochloric acid (prepared by cautiously adding a volume of concentrated acid to an equal volume of cold water), and then wash into the drain.5... 

Wear butyl rubber gloves, laboratory coat, and eye protection. Work in the fume hood. Place a 1-L, three-necked, round-bottom flask, equipped with a stirrer, dropping funnel, and thermometer, on a steam bath. Place in the flask 600 mL (1.5 mol, 50% excess) of a 2.5 M sodium hydroxide solution (prepared by slowly dissolving 60 g of NaOH in 600 mL of cold water) and add tetrachlorosilane (42.5 g or 28 mL 0.25 mol) dropwise at such... 

Rubbers were compounded with the ingredients and vulcanized as shown in Table I. The vulcanizates were cut off from the sheet with JIS (Japanese Industrial Standard) No. 3 dumbbell cutter to prepare the samples for heat aging. Styrene-butadiene rubber (SBR), cw-polybuta-diene (BR), and butyl rubber (HR) vulcanizates were aged in the Geer oven at 100°C. for 48 hours. Natural rubber (NR) was aged at 100°C. for 36 hours. 

Cationic polymerizations are not only important commercial processes, but, in some cases, are attractive laboratory techniques for preparing well-defined polymers and copolymers. Polyacetal, poly(tetramethyl-ene glycol), poly(e-caprolactam), polyaziridine, polysiloxanes, as well as butyl rubber, poly(N-vinyl carbazol), polyindenes, and poly(vinyl ether)s are synthesized commercially by cationic polymerizations. Some of these important polymers can only be prepared cationically. Living cationic polymerizations recently have been developed in which polymers with controlled molecular weights and narrow polydispersity can be prepared. 

Polymers produced by cationic vinyl polymerizations include poly(A/-vinylcarbazole) and poly(vinyl ether). However, polyisobutylene and its copolymer with isoprene (butyl rubber) is probably the most important commercial polymer produced by a cationic polymerization. Other industrial polymers such as poly(styrene) can be prepared by cationic polymerization, although they are usually produced radically or anionically. Many low molecular weight polymers produced by cationic polymerizations of... 

As shown in Table 1, poly(isobutylene-co- -pinenes) containing up to 10 mole% -pinene are rubbery materials Tg< —53 ). In view of the structural similarity between our copolymer and butyl rubber, we decided to use conventional butyl rubber cure conditions (3) to prepare our vulcanizates (see Experimental). Figure 2 shows the curing rate of two copolymers containing 3 and 10 mole% fi-pi-nene units respectively, as determined by a Monsanto Rheometer at 160 C (320 F). As expected, the curing rate of the cr lymer containing 10 mole% unsaturation is several times hi r than that of the material with 3 mole% unsaturation level. 

Examples of preservatives are phenylmercuric nitrate or acetate (0.002% w/v), chlorhexidine acetate (0.01% w/v), thiomersal (0.01% w/v) and benzalkonium chloride (0.01% w/v). Chlorocresol is too toxic to the corneal epithelium, but 8-hydroxy-quinoline and thiomersal may be used in specific instances. The principal consideration in relation to antimicrobial properties is the activity of the bactericide against Pseudomonas aeruginosa, a major source of serious nosocomial eye infections. Although benzalkonium chloride is probably the most active of the recommended preservatives, it cannot always be used because of its incompatibility with many compounds commonly used to treat eye diseases, nor should it be used to preserve eye-drops containing anaesthetics. As benzalkonium chloride reacts with natural rubbers, silicone or butyl rubber teats should be substituted and products should not be stored for more than 3 months after manufacture because silicone rubber is permeable to water vapour. As with all rubber components, the rubber teat should be pre-equilibrated with the preservative before use. Thermostable eye-drops and lotions are sterilized at 121 °C for 15 minutes. For thermolabile drugs, filtration sterilization followed by aseptic filling into sterile containers is necessary. Eye-drops in plastic bottles are prepared aseptically. 

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