• Abstract and Figures
• Public Full-text

More Than Meets The Eye The Stories Behind the Development of Plastic Lenses About the Author Joseph L. Bruneni is the author of "LOOKING BACK, an illustrated history of the American Ophthalmic Indusl1}', II a hard cover book pub­ lished in 1994 and still in print. He is a frequent contributor to most of the major optical trade publications and writes regularly-appearing colunUls in a number of them. He serves as a special consultant to the Optical Laboratories Association (OLA) and is a member of the Ocular Heritage Society. He currently serves as an assis­ tant professor teaching ophthalmic optics at the Southern California College of Optometry. On the Cover The cover illustrates key elements in the development of ophthalmic lenses. Upper rigbt: Tltis is the first known painting to show someone wearing eyeglasses. It was painted in the year 1252. Directly below: Pince-nez glasses were in vogue around the turn of the century. They often featured a chain or ribbon to catch them when they fell off the nose. At left: Frank Strain was one of the two inventive chemists at PPG who developed and patented allyl diglycol carbonate (CR-39® monomer) in 1940. Due to the war, ule patent was not issued until 1945. Center: Amodel of the atomic structure of CR-39 monomer. Bottom left: Tltis energy-efficient landmark glass tower in Pittsburgh, Pa., serves as international headquarters for PPG Industries, a global manufac­ turer of coatings, glass, fiber glass, and industrial and specialty chemicals. - (Ue Beginning under the rna erial s batch name "CR-39.' In By the time World War II began, the future year , more than 180 different plastics revolution was already well underway. compounds of this clear resin were Polystyrene resins had been produced individually researched and investigated. conunercially since 1937 and nylon, the first high-performance engineering plastic, was also THE 39TH COMPOUND a product of the 1930s. As the war began, both the Allies and the Axis powers faced sever The 39th attempt was the most promising shortages of natural raw materials. The plastics because it offered some unique characteristics. industly turned out to be a rich source of Among them was the fact that the resin could acceptable substitutes. Realization of this fact be combined with multiple layers of cloth, led to concentrated efforts by the industly to paper and other materials to produce develop other new plastics. exceptionally strong laminated products capable of being molded into a variety of With tlus heightened interest in plastics, reinforced shapes. Tlus discovelY marked the PPG Industries-known as Pittsburgh Plate beginning of what woul come to be majo~:,) Glass Co. until 1965-began searching for a new induStly called "reinforced plastics." L.. way to create an allyl resin with low-pressure "'0 thermosetting properties. Rohm & Haas had The first conunercial use for Pittsburgh ah'eady developed Plexiglas® resin and DuPont Plate Glass Co.'s new monomer iJwolved chenusts had invented Lucite® resin, both of combining the resiJ1 with fiberglass (another them thermoplastic materials. Pittsburgh Plate Pitts urgh Plate Glass Co. product) to form a)] Glass Co. owned a subsidialy company in molded fuel tank for the B-17 bomber, the () Barberton, Ohio, called Columbia Southern famous Army Air Force plane that saw service Chenucal Company where a research team was in evelY theater of operation during World War assigned responsibility for investigating clear II. The fuel tanks were molded of materials resins. The term' Columbia Resins" was lan1inated with CR-39® resin and lined \\ith a chosen to serve as the name of tms proje t. special rubber compound that became self­ sealing when the tank was pierced by bullets As a cowpound was isolated and worked on or shell fragments. ReplaciJ1g conventional fuel by the team, it was identified by a code tanks with tanks lanunated USiJ1g CR-39 resin number. By May 1940, one of the compounds made it possible to greatly reduce the plane's showed real pronuse. TIus particular resin was weight, extending the bomber's range and an allyl diglycol carbonate (ADC) monomer contributing substantially to the war effort. that Pittsourgh Plate Glass Co. trademarked • FUEL MONITORS did know that when it happened, ulstead of an expensive railroad tank car, they would end up Another umovative use for the new CR-39® with a useless steel-encased slab of plastic. resul in aircraft was production of transparent tubes that were embedded ill fuelliIles running THE SEARCH through the flight enguleers' compartment, FOR PEACETIME USES providillg the crew a visible gage to uldicate fuel flow to each engule. These tubes made of Avariety of uldustries were contacted in a CR-39 resin replaced tubes made of glass search to find customers for the left-over which were often shattered during combat, CR-39® resul. Afew individuals in the spraying gasoliI1e throughout the cockpit. ophthalnuc industry indicated some initial There was also some minor use of transparent interest, particularly because of the material's CR-39 resm for makiIlg lenses during the war resistance to ullpact. One company was but the lenses produced were Yz" to %" thick interested enough to set up a special research and prunarily used for reflector and department to tty to develop plastic eyeglass searchlight applications. lenses. The company was Uluvis Lens Company, at that time located Ul Dayton, Ohio. THE WAR ENDS Univis was a leading lens producer illvestulg large sums in an attempt to produce plastic When the war ended Ul 1945, all lenses from CR-39 resin. Their efforts are government contracts were cancelled, and explained in greater detail Ul Robert Graham's Pittsburgh Plate Glass Co. 's Barberton plant stOly (see page 14). Eventually Uluvis ended up with a railroad tank car full of allyl abandoned the project. It's interesting to note diglycol carbonate (CR-39® resin), all that that, following successful production of was left from wartune production. The 38,000 plastic lenses by Armorlite, SOLA and Essilor, pounds of resin rema.iIung ill the tank car Uluvis did eventually become a major plastic represented a costly mvestment for the lens producer. company, so a search was launched for civilian markets that could use this transparent resin. PPG old-wners involved durillg that period remember how tune-sensitive tius project became. CR-39 reSUl rema.iIls a liquid until a catalyst is added. Eventually, however, the ~ material polymerizes, or hardens, without a ~ >< Patented Feb. 27, 1945 2,370,565 catalyst. In those early days, no one knew how ~ long that self-curing process would take. They -.; -!..., I UNITED STATES PATENT OFFICE • FLAT SHEET MARKET THE TANK CAR Until 1960-61, PPG's primaty CR-39® resin Looking back to that tank car of CR-39® sales were for flat sheet applications. These monomer sitting forlornly on a siding in sheets of transparent plastic were used for Barberton, Ohio in 1946, the PPG employees personal safety equipment and clothing such who tried to sell the contents before the resin as welding helmets, industrial goggles, gas solidified uncovered two important facts. The masks, etc. Another widespread use of CR-39 first was that CR-39 monomer was remarkably resin during those post-war years was for stable with an amazingly long shelf life. The windshields of industrial crane cabs and other solidifying they feared never came to pass. vehicles used in industrial plants. Much of the Their other discovelY was that there was early work in developing optical lenses was indeed a viable market for a stable, concentrated on strong correction lenses, transparent, inlpact-resistant material for primarily high plus lenses used for post­ producing spectacle lenses. cataract patients. This was an inlportant segment of the lens industly in those days PPG-The Company before development of the inter-ocular lens. The company known today as PPG As the optical industly gradually learned Industries, Inc. was founded by two velY how to cast lenses from CR-39 resin, and how dissimilar men. John Pitcairn was a to edge and surface these new lenses, sales to conservative railroad official. In 1880, he Franklin Strain, standing at the right, the optical industly grew slowly but steadily linked up with Captain John B. Ford, a wa the co-developer ofallyl diglycol until 1975, when more than 90 percent of flamboyant entrepreneur. For some reason, carbonate (CR-3~ mOnOlllel) along with Frank A1Ils/wt. He is seen here PPG's CR-39 resin sales were to the optical now forgotten, these two men came to the di cussing the ojJticaljJrojJerties of CR­ trade. In 1975, PPG's marketing experts conclusion that they could produce and 39 monomer with several PPC marketing e:recutives. l\1uS/wt and predicted that plastic lenses-at that time market plate glass. This was an ambitious Strain's originaljJatent application, representing 15 percent of all eyewear in the undertaking because, at that point in time, dated October 15, 1940, stated, .S.-would grow to 30 percent by 1978. Few plate glass for the United States was almost "Thus, we have been able to jJrejJare comjJlex esters ofva rious polyglycols people outside of PPG believed that optimistic entirely imported from Europe. More than a such as diethylene, trieth)'lene, predictiol'i. Today, plastic lenses represent dozen U.S. companies tried to compete in this tetraethylene, jJentaet/l)'lene, dijJrojJ)'lene, triprojJylene, more than 80 percent of the .S. market. market but all ended as financial failures. tetraprojJ)'lene, dibut)'lene, or other Belgium, England, France and Germany polygl) col. ' Who could have jJredicted monopolized both the machinely and the skilled "'" how such an exotic chemical v~ ( co nbination would imjJact C)'ewear in technicians required to produce plate glass.

Load more

  40

Copy Link