B. S .
G A R V E Y
ELASTOMERS FOR T H E CONSUMER In the spotlight-coatings
/or missiles, two-pll, tires, sneakers, foundation
garments.
BR and Spandex.
On stage-cis
In the wings-EPR.
All
phases of elastomer research emphasize potential consumer market applzcations
igh quality performance of cis BR (cis-polybutadiene
H rubber) in tires has been demonstrated in road
tests. And production capacity is increasing rapidly. Polyurethanes have also become established as elastic fibers with present outlets in foundation garments and swimming suits. Ethy-lene-propylene rubbers are studied and discussed at great length but quantity production is well in the future. A technique for ablating silicone rubber compounds makes them excellent for insulation on space vehicles. An increase in output of two-ply tires can be expected since this type is now standard on compact cars. Rubber-soIed canvas shoes, touted as both formal and casual wear by the younger generation, gain increasing popularity and offer additional outlets for elastomeric products. N o comprehensive summary of progress in elastomers is possible due to the extreme mobility of the field. A selection of developments believed to be of general interest during the period May 1, 1961, to March 1, 1962, is covered here. General
Total rubber consumption in 1961 dropped to 1.51 million long tons from 1.56 million long tons in 1960 chieffy because of reduced auto production ( 7 A ) . I n 1962 it is expected to rebound to 1.62 million long tons. Currently 72y0 of the total is synthetic rubber. Although tires and tire products continue to use most of the rubber, 37y0 of the 1961 total, c r 550,000 long tons, went into nontransportation items. This amount is equal to the total annual con.rumption o f new rubber prior to the outbreak of W-orld W a r 11. Twenty-five years ago the United States was totally dependent on imports for crude rubber. Now it is a large exporter of synthetic rubber and compounding materials but exports are falling because of increasing production of these materials in Europe and Asia, often in facilities jointly or completely owned by American companies. In Europe, consumption of synthetic rubber has increased to 4070 and even in Brazil, the home of Hevea Brasiliensis, it is about 357, of the total. 52
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
SeveraI suits are pending in U. S. courts over the validity of the U. S . patent on oil-extended SBR for use in tires. Similar patents have been granted in England, Germany, and Sweden. Phillips Petroleum and Du Pont have settled out of court their dispute over Du Pont‘s patent on high density polyethylene. Another legal decision of big financial interest to tire manufacturers, as well as to truckers, is that of the Interstate Commerce Commission giving wider scope to the “piggybacking” of trailers on railroad flat cars. It is of public interest also because of its possible effect on highway traffic patterns. Rubber
YATURALRUBBERS. Consumption of natural rubber has continued to exceed production by a small margin. A lower price is attributed to stockpile sales in the United States and in England. Obuiously such sales are notpopular in rubber-producing aieas. Planting of high yielding trees has doubled the yield per acre on Malayan estates from 434 to 898 pounds. For this reason 62% of the rubber now comes from 45Y0 of the estates. Oil-extended Hevea is considered as a competitcr for oil extended SBR (QB). For a number of uses liquid rubber, made by heat depolymerization of natural rubber, is advantageous ( I 7B). Several unrelated plants produce rubber of the same molecular structure as that from Heoea (27B). I t has been proposed that the biosynthesis of rubber takes place through use of isopentyl pyrophosphate (3B, 72B).
SBR. Liquid SBR polymers produced by the American Synthetic Rubber Corp. are finding a variety of uses such as casting, spreading, plasticizing, and in hard rubber. It has been shown that a good masterbatch can be obtained by polymerizing the monomers in the presence of carbon black ( ISB). A production line at the Goodyear synthetic rubber plant in Houston is now being controlled by a n analog computer (23B). An analysis of production statistics for 1961 indicates that for that year over 150,000 long tons of petroleum oil were sold as rubber (6B). BUTYLRUBBER.Announcement that it will build a 35,000 ton-per-year plant to produce butyl rubber at Lake Charles, La., has been made by the Columbian Carbon Co., recently merged with Cities Service. Although the sale of butyl tires seems to be increasing slowly, the chief use of butyl rubber is still in inner tubes and curing bags. Because of their compatibility with other rubbers, halogenated butyl rubbers make it possible to combine the advantages of butyl rubber with those of other types (7B, 29B). Chlorinated butyl rubber makes an excellent liner for retaining air in tubeless tires (7B). EDITOR’S
NOTE
T h e Sefitember issue of I@EC Product Research and Development (quarterly) will contain a selection of 5 articles based on papers presented before the Division of Rubber Chemistry in Boston, April 7962.
Patching concrete takes on (I new look as latex modified Portland cement enters the picture. Better service can be exbected from this combination of materials
POLYURETHANES. T h e most interesting development in polyurechanes is the rapid acceptance of Spandex fibers for foundation garments, swim suits, and the like. Officially, Spandex fibers are elastomeric fibers in which the fiber forming substance is a long chain polymer consisting of a t least 8.5% segmented polyurethane. At least three companies, D u Pont, U. S. Rubber, and International Latex, are already in production and several more seem to be well on the way including Firestone Tire & Rubber Co., Chemstrand Corp., and Mobay Chemical Co. In pilot production are Globe Mfg. Co. and Easthampton Rubber Thread Co., while Lloyd Mfg., Rhee Elastic Thread, and Ameliotex, Inc., are deep in development work. About a million pounds were used in 1961 and estimates for consumption range up to 30 million pounds by 1965. Products and processing methods have been described for casting, molding, and extruding urethane elastomers (4B, 2OB). They are characterized by high strength and load-bearing capacity, low set, and excellent resistance to tear, abrasion, solvents, oxidation, and ozone. STEREO RUBBERS.Stereo rubbers have come out of the laboratory into commercial production. Some 40,000 long tons were made in 1961 and production capacity by the end of 1962 is expected to approach 200,000 long tons. T h e greatest current interest is in polybutadiene, cis BR, which has been shown to give VOL. 5 4
NO. 8
AUGUST 1962
53
remarkable improvements in tires whether used alone or in mixtures with Hevea or SBR (24B). It improves tread wear, resistance to groove cracking, resistance to ozone cracking, heat buildup and carcass durability, and resistance to skidding on snow and ice. Production methods have been given for a Goodyear pilot plant (I4B) and a Goodrich-Gulf plant was described. The proportion of cis isomer in the different polybutadienes ranges from 35% in Firestone’s product made with lithium catalyst to 98% in Goodrich-Gulf’s product made with a cobalt-containing catalyst. Directions for compounding and mixing these rubbers have been published (5B,IOB, 25B). trans-Polybutadiene like trans-polyisoprene ( 7513) resembles balata, best known in gold ball covers. U. s. Rubber Co. has a rhodium salt-catalyst system for producing trans-polybutadiene. ETHYLEKE-PROPYLENE RUBBER.Commercial sale of EPR has been started by Enjay Chemical Co. At least three others are known to be interested in producing it, Hercules, Avisun, and Du Pont. Its production and properties have been described in several papers ( I B , 8B, 13B, 77B, 28B). Two modifications contain double bonds and can be vulcanized Tvith sulfur and accelerators (8B, 79B). E P R is potentially a low cost, general purpose rubber with good rubbery characteristics and physical properties. Because of its chemical saturation it is inherently resistant to oxygen, ozone, and weathering. It can be vulcanized with peroxides (79B, 26B), peroxides and sulfur ( 2 B ) , or special rwlcanizing agents such as trichloromethane sulfonyl chloride, trichloromelamine, and quinone-;\:-chlorimide ( Z l B ) . Products
Two major developments in the tire field are the t\voply tire and a minor revolution in marketing practice. In two-ply tires the cords are bigger and stronger than in four-ply tires. They are said to give a softer ride, better traction, and reduced rolling resistance. U7hile material use is about the same, production costs arc lower because of fewer steps and less labor. They arc original equipment on compact cars for 1962 and are gaining in popularity (?C). In tire cords, polyester fibers became commercial in 1962. Cords from polyolefins are getting more attention than those from poly(viny1 alcohol). Nylon has increased its share of this market at the expense of rayon. .4n automobile suspension system based on a combination of coil springs and neoprene air cushions has been patented by Regie h-ationale des Usines Renault. Latex modified Portlaiid cement finds increasing utility in patching concrete especially cn road surfaces and
AUTHOR Benjamin
Gnruey is now Manager of Rubber Chemicals f o r Pennsalf Chemicals Cor/). He i7as had a n extensive career in the rubber indzuir): and lias authored I&EEC‘s annual reoiew on Elastomers since 7957. 54
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
bridge decks. Low friction surfaces are made by grafting acrylate polymers on the surfaces of molded rubberarticles, hydrolyzing the acrylate, and fluorinatins with SF4 ( 2 C ) . The ablative characteristics of some silicone compounds make them excellent for protecting space missiles from friction heat during firing and re-entry into thc earth’s atmosphere (3C) BIBLIOGRAPHY General (1A) Currrnt Industrial Reports, Bureau of Census, [I. S. Ilepf. Comm., Ser. M30A, December 1961. (2A) Degekolbe, R . (to General Tire and Rubber Co.), Ger., Pat. 1,069,868 (Nov. 26. 1959). Rubbers (1B) Amberg, L. O., Robinson, A. E., IND. EING.C H e x 53, 368 (1961). (2B) Averna, G. (to Montecaiini), Ital. Pat. 587,009 (Jan. 2, 1959). (3B) Archer, B. L., Ayrey, G.) other, Nature 189, 663 (1961). (4B) Axelrod, S. L., Hamilton, C. W., Frisch. K. C.: IND.ENG. CHEM.53, 889 (1961). (5B) Brown, R. J., Knill, R. B.: other, Rubber W o r l d 145, 70 (November 1961). (6B) Bugbee, H. C.; Il‘atural Rubber AVm!sp. 6 (February 1962). (7B) Frisco, J. V.; Dudley, R. H., Rubber W o r l d 144: 67 (August 1961). (8B) Gladding, E. K . , Fisher, B. S.,other, Ind. Eng. Chem. Prod. Research Develop. 1, 65 (June 1962). (OB) Gurrey, W. A., R u b 6 ~ r@ Plastics Age 42, 862 (1961). (10B) Hannsgen, F. W., Rubber Age (A7. Y.)89, 441 (.Tune 1961). (11s) Hardman, K . V., Land, A. J.. Rubber A g e ( N . Y.)90, 431 ’ (December 1961). 112B) Hublin. R.. Rea. -en. caoutchouc 38. 904 (1961) jl3Bj Kelley,’R. J., Ga;:ner, H. Iother, Di;, Rubber Chcniistry, 140th Meeting ACS, Chicago, September 1961. (14B) Kuchinski, F. L., hluraski. F. T.: Chem. Eng. Prop. 5 7 , 62 (August 1961). 115B) Lasky. .I. S.: Garner, H. K.. Ewart? R. H., I d . Eng. Chem. Prod. ResParch Deueiofl. 1 , 82 (June 1962). (1GB) Mavon, S. H., von Fischer. LV., other; J . .4$$1. Polymcr 5, 308 (1961). (17B) Natta. G., Crespi, G.. Keu. gen. cuozdchiuc 37, 1003 (1961). (18B) Natla. G.. Crespi. G., Bruzzone, hl.:Kuufschuk 21. G‘zcnin~z 14, WT 54 (1961). (19B) Natta. G.. Crcspi, (2.. other, Rubber A g e (.V. I,.) 89, 636 (1961). (2OB) Piggott, E;. A,> Britain. .J. \\:,, orher. Znd. E q . Ciirm. Prod. Research Develoj 1, 28 (1962). (21B) Rehner. .J.. .Jr., \Vei. P. L., Rubbci C‘licm. nrd Technol., i n press. (22B) Robinson, A. E , >Marra. J. V.. Amberg, L. 0 , Ind. ~En:. Chem. Prod. Research Develoj. 1, 78 (June 1962). (23B) Roquemore, K . G.; Eddey, 1:. E.; Chon. En
