They are manufactured by impregnating various fibrous base materials, such as paper, canvas, linen, or asbestos, with the resin a n d s u b s e q u e n t l y laminating the impregnated base by the application of heat and pressure. Some of the better known products of this character are offered under the trade names Celoron, Dilecto, Formica, Micarta, Smuldite, Phenolite, Synthane, and Textolite. A few chemical manufacturers have used moducts of this kind for manv Y years; but it is only recently that th”e industry generally has become aware of their usefulness. A few examples of their successful a p p l i c a t i o n t o chemical problems will illustrate the field of their utility: One installation of piping made of laminated synthetic resinous construction was destined for use in handling a h o t brine solution. This particular installation required approximately 6200 f e e t of 2-inch i. d., 2.5-inch 0. d. piping assembled from 80- to 84-inch lengths with Dresser couplings of special design involving the use of a laminated resinous sleeve having the same resistance as the piping itself. The piping was of paper-base construction, coming within the specification of “XX Rolled Natural,” which is the most satisfactory grade for service of this class. Elbows and tees of molded macerated fabric base construction were used as required. Another similar installation is now under way for the same purpose involving some 12,000 feet of piping. A successful application of laminated piping of synthetic resin composition is found in handling dilute acetic acid solutions in the vinegar industry. Resistance to the action of acetic acid in all concentrations plus the desirability of keeping the product free from even the slightest trace of metals make synthetic resins ideal materials for this application. Figure 1 shows a portion of an installation of some 4200 feet of piping in this industry. This particular installation required 2-, 3-, and 4inch piping assembled by threaded couplings and fittings. It is typical of many other installations in the vinegar industry. Another particularly successful installation of pipe and fittings in another industry is handling a zinc chloride solution of 70” B6. concentration which is used in a manufacturing operation and subsequently recovered from the acidified and considerably diluted solution in a double-effect evaporator.
Plastics
I
-
Industry
in LESTER W. TARR
Haveg Corporation, Newark, Del.
A
LTHOUGH synthetic resins have been recognized almost since their introduction as possessing marked resistance to chemical attack, their application on a substantial scale to the solution of the problems of the chemical manufacturer has only recently become important. This growing utility of synthetic resins as materials of chemical construction has developed largely from two causes: improvements in the fabrication of large pieces through the application of a new molding technic, and improvements in the resins themselves which have adapted them for use in this field. Although these causes are mentioned separately here, it should be understood that a distinct separation of the two is nearly impossible, so closely are they interwoven one with the other. At present the use of chemical equipment built of synthetic resins is of increasing importance in the industry since materials of this type avoid completely many serious problems of corrosion. The use of synthetic resins in chemical industry has been limited almost entirely to those resins of the phenol-aldehyde type (Bakelite) since these resins offer complete resistance to acids of all types except those having an oxidizing action. Phenol-aldehyde resins are not resistant to strong alkalies (sodium and potassium hydroxides, etc.) even in dilute solutions, and this fact places a limitation on their application. There is, however, no fundamental reason why alkali-resistant resins should not be made. and in the course of further development they undoubtedly will be available. For the present it is necessary to realize this limitation and in the following discussion the use of such e q u i p m e n t to combat only acid corrosion will be considered. Synthetic resins are in themselves mechanically weak, and consequently the use of the pure resins alone is restricted. With the exceptions of their important use in varnish form as a protective resistant coating and a few minor applications in limited fields (measuring instruments for hydrofluoric acid, etc.), the equipment made from resins contains various fibrous materials to provide mechanical strength. Laminated Products Laminated synthetic resinous products h s t engaged attention since these products were early developed and used in chemical industry.
FIGURE1. 1284
SYNTHETIC
RESIN P I P E WITH THRE.4DED CHEMICAL PLANTUSE
COUPLINGS,
FOR
NOVEMBER, 1935
INDUSTRIAL AND ENGINEERING CHEMISTRY
1285
FIGURE2. SYXTHETIC RESINPIPINGFOR HANDLISG70' BE. ZINC CHLORIDE SOLUTION
The first use of a laminated synthetic resinous product in this case was in the construction of the impeller to replace the bronze impeller operating the pump between the first and second stages of the evaporator. The impeller of laminated synthetic resinous composition was examined and found to be in perfect condition after 12,000 hours of operation, whereas the bronze impellers had failed consistently in less than 700 hours. The corrosion problem presented by this installation was particularly severe when metals were used, since the acidified zinc chloride attacked and dissolved copper from the tubes of the evaporator, and the dissolved copper precipitated out on and dissolved iron with which it came in contact, all to the serious detriment of the equipment itself. Oddly enough the electrolytic nature of this corrosion was not a t first recognized, and consideration was given to the replacement of steel pipe lines with copper which was considered to be resistant to zinc chloride solution. The proposed remedy in this case would, of course, have been worse than the disease. When the real nature of the problem was eventually recognized, the answer was provided by installing a 3inch pipe line of laminated synthetic resinous composition extending indoors and outdoors for a distance of 750 feet and assembled with Dresser couplings of modifled construction. (Figure 2). The complete cost of the erected line was $2070 as compared with the estimated cost of $2186 for the copper line considered originally. In addition to the applications of piping in the chemical industry so far considered, numerous other requirements of the industry are met by using laminated sheets and molded products which latter have been used in even larger amounts than piping or sheets.
Molded Products Molded resinous products, largely of the so-called macerated fabric base type, are particularly useful in the rayon industry where they serve as spinning buckets, bucket covers, bobbins, funnel brackets, compartment covers, and gears, to mention only the most important. In other branches of chemical industry, drying trays, bearings, and pipe fittings are typical applications of molded parts. Numerous other applications could be mentioned, but these are sufficiently illustrative of the principles of their use. The essential properties of synthetic resinous products which make them especially valuable in chemical industry are: (1) Resistance t o chemical corrosion. (2) Unusual strength and toughness per unit of weight.
(3)
Reasonable cost.
(4) Elimination of electrolytic corrosion. ( 5 ) Resistance to thermal shock and to temperatures up to 150' C. (6) Elimination of contamination by metals. Ease of assembly due to lightness (specific gravity 1.35). (7) (8) Machinability.
Despite the obvious usefulness of laminated resins described there are two serious drawbacks to their wider use in chemical industry. Although the resins themselves are markedly resistant to nonoxidizing acid solutions, the cellulosic base materials ordinarily employed in the laminating process are distinct points of weakness through which the whole structure may be destroyed. The second weakness of laminated resins in this application is that no practicable way has been found to fabricate vessels of substantial size from them. A new technic for handling the resins and for making the composition required for forming large vessels to overcome the weaknesses of laminated resins is now available to American chemical manufacturers under the trade name of Haveg.l
Haveg The resinous compound used in fabricating equipment of the new kind consists of a special resin of the phenol-aldehyde type compounded with acid-washed asbestos fiber, instead of cellulose materials, which gives the body a uniform resistance t o chemical action. This compound is handled in fabrication by a new molding and curing technic which avoids the extraordinary expense of pressure-molding and allows vessels as large as 9 feet in diameter by 10 feet in height to be made with a mold cost which is so low that single vessels can be manufactured economically. These two unique features of Haveg, when applied with an engineering skill that takes into account both the problem to be solved and the properties of the material itself, make it very nearly the ideal solution to many of the most vexing problems of chemical manufacture. The finished vessels possess all of the advantages outlined above for the resins themselves and in addition have a compact, impervious, homogeneous structure with smooth jointless surfaces. The chemical resistance of the material is well understood and with the exceptions of the strong alkalies and oxidizing acids is practically complete. Where hydrofluoric acid is to be handled, a special resin composition is available made with graphite instead of asbestos. There are a few other exceptions 1
Killeffer. D. H., IND. EM. CHEM.,25. 1217-19 (1933).
fYlifi
VOI.. 27, NO. 1 I
F I w t ~ 3 (Ir*:YT) . '"E'
A1mjn"-
TlON T O W E R S
tivt: oi the cotisbruetion employed in asseintding units to build equipruent uf unrisual dimiensions. This particular evaporat,ing ptii is 15 feet brig, 10 feet wide, and 5 feet. deep. The tanks shown in Figure 5 are typical of Haveg cmstrnction Each is 9 feet in diameter and 6 feet higih. The tank in each case is reenforced with x,ooden slats held in place by steel bands. These tanks arc now in successful use for digestion of scrap copper wit1i acid. Tliese few typical examples of the utility uf syuthetic resins in the const,ruction of tire special equiliment needed by tire rlieniical industry are by no ineam exhaustive, bot they do indicate the breadth of applications of these products in the ~(ilutiunof many serious prohlerirs of clieniical manufact,ure. Alt,liough by no means a cure-all, plastic equipment serves niany needs admirably. Inrproveinents ill the resius theuselves t o overcome some of their present ~eaknessesare sure to fok!w continuing develqnnent. Already resins are avail-
Fza,.,w 1.
I1 ~
(R,
