Ε. Ε. McSWEENEY and Ε. L. KROPA
I/EC
Battelle Memorial Institute, Columbus, Ohio
ANNUAL
R E V I E W
PLASTICS AND RESINS YEAR'S
perspective has not clari
fied the complicated situation A existing in the olefin polymerization
field. Further discussion on polypro pylene has created intense interest, but no plans for commercialization have been announced. More in formation on the properties of the polymer was disclosed. It will be competitive in price with polyethyl ene and is expected to achieve its major utility in molded products and in films. However, stability to oxida tion and a tendency to crystallize ex cessively on aging are said to be major problems which must be overcome. A noteworthy event was the an nouncement by Standard Oil of Indiana of a polyethylene process based on a heterogeneous catalyst. A considerable patent structure has been developed to cover this process and several licenses have been granted, but no production time tables have been set. Not to be outdone in this battle of new products and processes, ICI disclosed that high-density polymers approaching the properties of those made at low pressure can be made by a modification of the conven tional high-pressure process. These polymers havesufficiently high soften ing points to resist boiling water and so will compete with low-pressure polymers and polypropylene in mar kets where heat distortion is impor tant. Although no details of the process have been announced, it is reasonable to speculate that a hetero geneous process may be involved. If so, what are the real advantages of a low-pressure process? Appar ently there are still some, as the first U. S. company to announce its inten tion to use the ICI process also is a licensee under one of the low-pressure processes. Possibly the most confusion lies in the patent aspect. There are at 26 A
least three low-pressure polyethylene processes depending on three groups of patents, but too few U. S. patents have issued to indicate clearly the relative position. Polypropylene is apparently made by a process re lated to the Zicglcr catalyst, but rela tions among Ziegler, Natta, Montccatini, and various licensees are by no means clear. While the commercial aspects re main cloudy, significant advances were made on the scientific side. It appears now that a chemisorption system is the key to the low-pressure processes. Phillips described its proc ess and product in some detail at the Dallas meeting of the ACS [IND. ENG. CIIEM. 48, 1152 (1956)].
A chromia-alumina catalyst which must be strongly oxidized is the key to this process, which produces a linear crystalline polymer with essen tially no vinylidene branching and no trans-oleûn structure. Polyethylene was also the major attraction at the Gordon Conference and a later polymer conference at Notre Dame. Several important papers were also given at the 130th ACS meeting at Atlantic City. At these meetings some detail on the Indiana process was given. In contrast to the Phillips process, the key step in the preparation of the molybdenum oxide-alumina catalyst is a reduction. A metal hydride co-catalyst apparently promotes the reaction but is not essential. The product, however, appears to be very similar to the Phillips material. Indiana also disclosed a nickel-charcoal catalyst which is said to give a product with a somewhat more branched structure. Knowledge of the Ziegler process was also advanced at these meetings. From various disclosures it is apparent that this, too, is a heterogeneous catalysis system with the cocatalyst, of which a subhalide formed
INDUSTRIAL AND ENGINEERING CHEMISTRY
from titanium tetrachloride is the most common, acting as the substrate for an anionic polymerization. Interaction between catalyst and cocatalyst appears to be specific. Added to the complication was the recognition that certain isotatic polymers were prepared before they were christened. In this early work only a single catalyst was employed, but it is not impossible that the preformed polymer may have acted as the substrate. With the knowledge derived from styrene and from vinyl ether polymerization, it is possible that there may be a number of common factors involved. With new products, new processes, and new names in polyolefins in the offing, it would be easy to overlook other developments which are occurring very quietly and which may have important ramifications. While copolymers of styrene and isobutylene are certainly not new, their availability in tonnage quantities was an event of 1956. The 50-50 copolymer appears to be the optimum one. In many applications it will be competitive to polyethylene, over which it has the advantages of somewhat better water-vapor impermeability and better clarity. Several new resins were announced, as were significant advances in several older resins. A new polycarbonate resin made from bisphenol A and phosgene was announced in Germany in September. This is a thermoplastic of high softening point, which is said to have excellent resistance to weathering, to heat, and to oxidizing agents. It can be fabricated into clear films which are slightly stiff and possess a highly metallic ring. While it has been known that new polymers based on dichlorocyclaoxabutane have been in the offing, it is only during the last year that the
pilot-plant production of a definite product, tagged "Penton," has been officially disclosed. These polymers are purported to possess excellent electrical and mechanical properties and excellent resistance to organic and inorganic chemicals. Films with high tensile strength and good water-vapor impermeability have been prepared. Fiber properties are also said to be excellent. At the same time, there have been technical publications concerning other nonchlorine-containing cyclaoxabutane derivatives. Many of these derivatives are also crystalline and may have important applications, if and when the original material has been commercially established. Still another development which appears to have many ramifications in plastics technology was disclosed in several British patents describing high polymers derived from formaldehyde. Such polymers are byno means new; it has been known that formaldehyde polymerizes rapidly to unstable polymeric entities in the presence of a number of catalysts such as sulfuric acid, boron trichloride, and trimethylamine. To secure thermally stable products of high molecular weight, not only must the monomer be purified prior to polymerization, but entirely new catalysts such as triphenylphosphine must be employed at low temperatures. Under these novel polymerization conditions, formaldehyde
Two nursing bottles are shown after steam sterilization at 2 5 0 ° F. in a hospital autoclave. At left, a shapeless blob, is one of ordinary polyethylene. At right unaffected, is one of Marlex 50 thermoplastic (Phillips Petroleum Co.)
polymers arc formed that can be transformed to tough, stiff, translucent films on molding. Fiber structures can also be fabricated. In view of the large scale production of formaldehyde, these new polymeric formaldehyde derivatives may very quickly move into and secure a dominant position among the giants of the plastic world. Formaldehyde polymers would then stand on their
own instead of existing only as reaction products with other resin intermediates. A new fluoro-elastomer was announced which contains about 6 5 % fluorine. In this copolymer of vinylidene fluoride and perfluoropropylene, the perfluoromethyl group on the polymer chain diminishes symmetry and affords elasticity. Even though the polymer is saturated, it may be vulcanized by means of polyamines or by free radicals generated either from peroxides or by radiation. Such vulcanizates can be compounded and their properties varied depending on the nature of the reinforcing agent. Vinylidene fluoride is also being studied with other comonomers; much more will be heard of this material. A new molding type of polytetrafluoroethylene is available in experimental quantities and is being evaluated for a number of applications. It can be fabricated in conventional equipment at about 700° F. Except for heat resistance, which is understandably lower, its properties are very similar to Teflon. While the structure of this new thermoplasticlike polymer has not been disclosed, there have been a number of papers on the various crystalline transition points of Teflon ; this new product is possibly a result of these or similar studies. However, the possiV O l . 49, NO. 1
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JANUARY 1957
27 A
A new plastic bowling grip, cast from a specially developed plastisol formulation based on B. F. Goodrich Chemical Co. Geon resin 1 2 1 , is demonstrated here by Steve Nagy, famed A.B.C. bowler
bility of a copolymer structure must not be overlooked. Intense interest in isocyanates was shown by the large number of papers and large audience at a symposium at the ACS Atlantic City meeting. Flexible foam still is the one significant commercial use. But with a potential capacity of 75 million pounds and an estimated consumption of less than 5 million, new markets are being aggressively sought. Coatings and adhesives look like the most immediate prospects for large scale commercialization, but solid elastomeric compounds and high-melting rigid foams are also likely possibilities. The high price of isocyanates is still a serious detriment. Any substantial price reduction would depend on development of large-volume uses and even then some changes would have to be made in specifications of the purity of the finished iso-
American Cyanamid's Fortier, La., plant for acrylonitrile production 28 A
cyanates. Contamination with triisocyanates is the most serious problem. In some uses where flexibility is not important, these more highly functional materials might prove advantageous. Preparation of epoxides by reaction of unsaturated linkages with peracetic acid gives promise of lower cost raw materials for epoxy resins. Peracetic acid has also been used to prepare monomeric lactones in high yield by reaction with cyclic ketones, including those made from tar acids isolated from hydrogenated coal. Because these lactones are free of contaminants which might catalyze side reactions or inhibit polymerization, they are especially useful for making polymers for use in plastics, plasticizers, and lubricants. Preparation of these materials and their reaction with isocyanates were discussed at Atlantic City. Several significant developments occurred in the silicone field. Two of these involve procedures for synthesizing derivatives containing groupings such as amino and carbethoxy separated by two or more methylene groups from the silicon. In contrast to alpha substituents, these are resistant to hydrolysis and so may be retained in polymer structures. Treatment of glass fiber and oxide fillers to promote adhesion of resins is especially interesting. A fluorinated silicone with excellent high and low temperature properties as well as good solvent resistance was also announced. Production of polyesters again increased to an estimated 73 million pounds, but the automatic production process which would cause a large increase is still being sought. Apparently only three fabricators
INDUSTRIAL AND ENGINEERING CHEMISTRY
are doing in excess of a million dollar business, while many smaller ones are falling by the wayside. Interest seems to be growing in organic fibers such as nylon, Dynel, and Dacron as reinforcing agents. Intensive work on use of radiation in the polymer field is under way in many laboratories, but only limited results have been published. Another approach to radiationimproved polyethylene involves use of a special filler which activates the material toward radiation. But no other indication of commercial use of radiation was noted. However, extensive research is being carried out by both industry and Government. Interest in radiation-induced grafting of various monomers to preformed polymer is especially great, but it remains to be seen whether there will be developed any product uniquely different from those obtained by thermal grafting. The best possibility seems to be with preformed films when thermal grafting is difficult without affecting film properties. Whether polymers formed by irradiating a monomer are distinctly different from those polymerized by conventional means remains conjectural. At the moment, the best thinking is that radiation is another means of free radical polymerization ; monomers which are not susceptible to free radicals apparently are not polymerized by radiation. Radiation-induced polymers are reported to have better heat distortion and better resistance to solvents; differences in density have also been reported, but these are hard to understand and further work is needed to clarify the point. Business in general held up extremely well during the year. Indications were that the plastics world in 1956 would comprise a volume of 2 billion dollars with a production of about 4 billion pounds, indicating an average price of 50 cents per pound. There were no discernible commercial trends, except that there is some indication of a movement toward high-softening thermoplastics as opposed to thermosetting compounds for a number of applications in the automotive, electrical, and household fields. This trend will be accelerated not only by the high-melting polyolefins mentioned above, but also by o-methylstyrene polymers and methylstyrene-acrylonitrile copolymers, which should be available commercially in 1957.
