f"1lowed b y Olle cuat of a clear 40 per cent solution. Recorder case 2 WRS given 1,wo C O H ~ Sof a black pyroxylin lacquer. At the t,ime Lhesa gtiotographs were taken, rcmnler case I was in excellent condition al't,er 29 nront,hs' service, and case 2 hurl failed bwdly io 15montI~s. paint,
S-I)-0, New Corrosion-Resisting Coating 0. 11. HAYDEN,Knbber Laboratory, E. 1. du Pont d e Nernours & Company, Wilmington, Del.
S
-1MJ i s a synthetic drying oil that was discovered during the course of the du Pant Company's research on syntlietic rnbber. It differs froni the natural drying oils in that its drying or hardening is due chiefly to polymerization rather than to absorption of oxygen from the air, and in that fully irardened S-D-0 films are unaffected by the action of all solvents and most corrosives (3). The synthesis of S-11-0 is closely related to that of the synthetic rubber, Duprene, for the first step in tho production of each is t.he reaction of acetylene with itself in the presence of a catalyst. When acetylene is passed into an aqueous solution of cuprous cliloride and annnoniuin chloride, two principal reactions take place (4):
(S-1)-0). Tlie rate of drying to its final hardness is inuch faster than that of natural dryiiig oils Ixxanse a very small amount of ahsorbed oxygen accelerates polymerizat.ion. The lilms t o wrinkle or craze upon drying is tendency of 9-1)-0 overcome by the addition to the solution of small amounts of antiwrinkling agents wliich slightly retard the rate of polymerir,at'ion. dDYANT.4GrjJ 01
S-D-0 PlINrE
S-1)-0 paints are prepared by grinding suitable fillers and pigments into 9-D-0 solutions. They are nsed as priming coats on metals because they are better than unpigmented solnt.ions and are also used as priming coats on concrete 2WC zz CH +HC a C -CH = CHz and other porous inaterials to prevent excessive penetration. (Monovinylacetylene) S-D-0 fdins usually dry dust-free in from 60 to 90 minutes, 3IIC =s CIS +CH, = CH--C C-CH = CHe and tack-free in from 1to 2 hours, depending on the thickness (Divinylacetylene) of the a m , temporature, air circulation, and the presence of .\loni~virrylacet~~lei~e is used for the preparation of Dn- driers or inhibitors. They reach a high degree of hardness in prerie (1). and divinylacetylene is polymerized to S-1)-0 (S). from 12 to 24 hours, and are fully polymerized in 48 hours. Tlie prilyinerization of diviiiylacetylene is promoted by S-1)-0 films are about fifteen times more impervious to imit. The lorvcr polynrers are liquid and mutually soluble, moisture than equally thick films of a linseed oil paint, but, iu 1iolyiirerization progresses, there is an increase in and about five times more so than filnis of glyptal resin osit,y follov~edby gelling, w-ith the ultimate formation of finishes. isoliiblc, infwiMe, and highly inert resin. Fully polymerized S-D-0 is uot dissolved or softened by The pro,liict of polynicriiring divinylacetylene to a degree any solvent or combination of solvents. Acids and alkalies iielrim tlir gel point is known as S-D-0 base. This is an have no effect except to cause darkening, vviiile corrosive amher-rolored viscous liquid tirat resembles a heavy-bodied vapors in the absence of moisture have no effect.. It is not I is soluble in all proportions in aromatic hydrocarbons. att.acked by chlorine, bromine, brine, ammonia (sointions or -1)-O lmse will eontiiioe to polymerize a t normal tem- anhydrous), hydrogen sulfide, crude oil, or refined petroleum prratiires. e\-cn in the absence of air, and for this reason can- products. The only cliemicals that do at.tack S-11-0 are not lie stored for any lcngth of tinre wibhout gelling. IIom- strong oxidizing agents, such as concentrated hydrogen perever, ivlicii it is diluted with an aromatic solvent it is no oxide, chromic acid, nitric acid, and hot eoncentrated sulfuric longer siiiijcct to spontaneous polynierization and may be acid. ITydroflnoric acid peneirates S-D-0 films, but does not stored n t uormal t,emperaturcs in the absence of light and air. dest.roy them. With tliese exceptions, no chemicals liavo S-U-0 i. t.Iierc.fore always sliijrpcd and used in the form of been found against vrliich S-D-0 does not give exceptional protootion. solutions, gencrally in solvent (coal tar) naphtha. f:ompletely polymerized S-11.0 is not thermoplastic and TYlicn a solution oi S-D-0 is applied to a surface or absorbed by a pmow material, the solvent evaporates, leaving a film will withstand temperatures as high as 200" C. without of S-D-0 b a g , which dries out rapidly t o a hard transparent cliange, but at higher temperatures tlrermal rlccoiiiponition ambrr-colored resin. It is due to this resemblance to natural sets in, with clrarring and the liberation of dense fumes. drying oils that it 1ia.s been named Synthetic Drying Oil Pigmented films withstand slig1it.ly higher ternperatores. 56 3
z~1'I'LICATIOX OF
S-U-0
S-D-0 may be applieil on almost any matorial other than glass or enamel, which because of their sin do not permit good anchorage. Wonil, pornus surfaces require no speck1 preparatirrii except that they sli(iiild lie reasonably clean and dry in order to permit adequate penetration arid anchorage. Xetal surfaces, however, sliould be rouglieireil bccause S-11-0 will not adliere if ttrcy are srrioot.h or dirty. The best treatnirrrt blast the surface and apply a prirner of S-11-0 p i i n possible (preferably withirr an hour) while the mctal is clean and dry. h less satisfactmy method of preparing the surface is to scratch with a wire briisli. A still poorer method is to pickle in acid. On wood, the best results are obt,ainc:d witli relatively uonresinous varieties, such as rnnple or fir. Poorer results arc obtained with cypress or yellow piiie, becaiise their pitclips exude during aging or under couditions of ele\w,ted temperatures and break the protective film. S-D-0 may be applied by briislii~igur dippiiig. Spraying is uiisatisfaetory because aeration promotes too rapid polymerization to give a smooth continuous film. The coverage of S-D-0 paints airii soluti~iiiscompares favorably witlr ordinary paints and varnisircs, arid depr:nds to a great extent on tlie porosity and smoothness of t i w surface. The only suitable thirniers for S-11-0 paints aud solutions are aromatic solveuts, such a.s high-flash coal bdr naplitlia am1 xylene. These tliinncrs may be added it1 any dcsired qhiantities, b u t turpentine, gasoline, and pebroleum nspiitha rnust be avoided. I n general, S-D-0 gives excellent protcction against ramsion. IIowever, certain limitatinns are rccognizcd with respect to its application arid use. Att,emiit,s to apply it in the same manner as ordinary fiirislios uniformly result i l l failure. Filrns of other nairik. varnislirs. and laeirucrs, regardless of their age, are si vehicle or solvent iii tlie new other finislies in that a fully hardened film is not softened by any solvent, nor by liquid S-D-0 itself. Because of this fact, successive coats must lie applied before the previous coat has fully hardened, or eke preceding coats must be treated simiiarly t.o a metal surface.
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1.lTERATUl~E CI.I.I?.D
and Kirby, J . Brit. ( ' h e m . Suc., (2) Collins. A Sf..U. S. I'Btent 1,812,X49 (June 30. 1951).
(3) Collins. A M., C. S.I'stont 1,812,544 (.June :iO. lCJ31). (4) iYieasliind, d. A,, U. S. Palent l.hl2.641 (June30. 1931'): Nicuwland. Cal-
Kcctiirin April 2. 1932.
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TEE*: ALCHEMIST by
S-11-0filrns, similer to vitreous enarriels, do not passess the same coefficient of expansion as metals; hence they will crack off most metals with sudden changes in temperature such as a channe of 100" C. in 5 minutes. lieat beine aaolied from only om: side. S-I)-0 is mildlv lirht-sensitive arid darkens tu a =olden-oak sliade oii expos& i o sunlight. Hence, it is impractical to prepare it in wliite or light colors. When fully dried the films are liarder and more brittle tliaii ordinary protective coating filim. It is useless to apply it on any but rigid surfaces that Till riot be bent or dented in service. S-D-0 paints and solutions will gel in containers during storage if exposed to air, and cannot t.hen be used because the gelling is irreversible. It is therefore necessary to keep S-D-0 tightly sealed in E cool place in fiiil cont.aincrs. Thick gelled residues from which t.he solvent has evaporated are liable to spontaneous combustion; lieuce, accumulations of 6-D-0, such as residue left in containers, puddles, and soaked rags or waste, constitute a fire hazard. The application of S-I>-0to concrete walls, either from tlie inside or outside, prevents seepage of moisture through the wall, even though it be submerged in water under moderate hydrostatic pressure. The treatment of a concrete floor with S-D-0 not only niakes it acid-, alkali-, arid moisture-proof, h u t also niakes it nondusting and considerably iriiproxs its wearing qualities. Concrete tanks, vats, absorption towers, etc., arc made acid- and aikali-proof by painting with 8-11-0, and tlie same treatmerit might be used for concret,e silos, swimming ~ O O ~ Swater , storage tanks, municipal water a.iid sewage lines, ate. B r i c k work and the various types of woodfiber board, insulating lumber, and other cellulose products may be similarly treated. S-D-0 has high dielectric strength arid may therefore be used as an impregnating agent for iiisulatiiig materials to render them moisture-proof.
.
E. Eichinger
1x0. 19 Of the Perouiatur seriea. See pwe 317 in our January k u e for conditions of sale.)
Proiessor E. EiclLingor oi Dresden, Germany, is an exponent of the Munich School. This painting is one of the few migiinnls of an alehemieat nature owned in this country.
