Abstract:
Unstabilized vinylbenzyl chloride and substituted vinylbenzyl chlorides are essentially inert with respect to surfaces of aluminum or alloys containing at least 90 percent by weight of aluminum in sharp contrast to benzyl chloride and similar substituted benzyl halides. Aluminum and such alloys of aluminum are thus practical materials of construction for making containers, pipes, stills, still column packing and the like for handling vinylbenzyl chloride.

Description:
BACKGROUND OF THE INVENTION 
     The present invention concerns a new use of a material in an application where the material has heretofore been considered entirely inappropriate. 
     Aliphatically bound halogen is known to be relatively reactive with many metals, particularly active metals such as aluminum. The reactivity of certain halides such as carbon tetrachloride and methyl chloroform with aluminum and aluminum alloys is well known and has been responsible for a great deal of work in the field of solvent stabilization. Activated halides such as allyl chloride, benzyl chloride, and substituted benzyl halides are generally known to be particularly reactive, and such halides are customarily handled in special containers or apparatus constructed of resin-lined metal, glass, ceramic materials, nickel, titanium or tantalum. Such halides have been considered essentially equivalent in reactivity so that a particular material of construction has been assumed to be suitable or unsuitable for contact with all members of the class depending upon its behavior with respect to one or two members. For example, benzyl chloride is known to react vigorously with an aluminum surface and the presumption has been that substituted benzyl chlorides behave in the same way. 
     SUMMARY OF THE INVENTION 
     It has now been found, completely unexpectedly, that although benzyl chloride and most substituted benzyl chlorides do react so vigorously with aluminum and aluminum alloys that contact between these substances must be carefully avoided, vinylbenzyl chloride and substituted vinylbenzyl chlorides as defined below behave entirely differently in this respect. The defined vinylbenzyl chlorides have the formula ##STR1## wherein R is an alkyl radical of 1-4 carbon atoms, m and n are independently one or two, and p is zero or one. These have been found to be so inert in the presence of a surface of aluminum or an alloy containing at least about 90 percent by weight of aluminum that such metals are suitable materials of construction for making shipping and storage containers, pipes, stills, or other processing equipment for containing, transferring, distilling, filtering, polymerizing, or otherwise processing these compounds without need for any stabilizer or inhibitor. 
     DETAILED DESCRIPTION 
     The peculiar unreactivity with aluminum is characteristic of all of the position isomers of the defined vinylbenzyl chlorides. Even the presence of water or small amounts of HCl, either anhydrous or aqueous, as in the crude material, has no significant effect. The presence or absence of atmospheric oxygen also appears to have no effect. The unreactivity persists at least to about 150° C. which covers those temperatures necessary in processing and is shown by both liquid and vapor phases. The only substantial deleterious changes observed in extended tests under these conditions are those caused by polymerization of the vinyl group. 
     It is thought that the reason for this unusual lack of reaction and corrosion of the metal surface is the formation of a protective film of some kind. Experiments wherein previous contact with a vinylbenzyl chloride appears to delay reaction when the metal surface is subsequently contacted with the reactive benzyl chloride seem to support this theory. Similarly, mixtures of benzyl chloride with substantial proportions of a vinylbenzyl chloride fail to react with aluminum. 
     The unreactivity of the defined vinylbenzyl chlorides with aluminum is particularly surprising in view of the fact that other closely related chlorides react vigorously, even at lower temperatures. Such reactive chlorides include benzyl chloride, ethylbenzyl chloride, and (1- and 2-chlorovinyl) toluene. Mixtures such as styrene plus benzyl chloride and vinyltoluene plus benzyl chloride are also reactive showing that a vinyl group per se is not an inhibitor to the reaction of benzyl chloride with aluminum. 
     The term aluminum is used herein, except where the distinction is made clear, to mean both essentially pure aluminum and alloys of at least 90% by weight aluminum content. Many such alloys are in commercial use and the alloying metals are typically one or more of the elements Si, Fe, Cu, Mn, Mg, Cr, Zn, and Ti. Less commonly used elements include Ni, Bi, Pb, Be, V, Zr, and B. 
    
    
     EXAMPLE 1 
     Liquid phase corrosion tests were run by refluxing vinylbenzyl chloride or other such chloride in contact with aluminum foil or coupon of sheet aluminum in a test tube with attached reflux condenser. These tests were made at 125° C. liquid temperature by maintaining the absolute pressure in the system at about 35 mm Hg. The aluminum used was either commercial aluminum foil or a coupon of sheet aluminum corresponding in analysis to aluminum 3003. VBC is used to designate mixed meta and para isomers of vinylbenzyl chloride in 60:40 ratio. The vinyltoluene, (α-chlorovinyl)toluene, and ethylbenzyl chloride tested were also mixed meta and para isomers. 
     
                                           TABLE I__________________________________________________________________________Test Material Aluminum               Time  Remarks__________________________________________________________________________pure VBC      sheet --    no apparent reaction.sup.1crude, wet VBC.sup.2         foil  --    no apparent reaction                     slow polymerizationbenzyl chloride.sup.3         foil  --    vigorous reaction                     with Al in approximately                     3-6 minutes1:1 styrene-  foil  --    vigorous reaction benzyl chloride1:1 vinyltoluene-         foil  --    vigorous reaction benzyl chloride1:1 VBC-benzyl chloride         foil  3 days                     no apparent reactionpure VBC,.sup.4         foil  3 days                     no apparent reactionthen benzyl chloride               30 minutes                     usual rapid reaction                     (see 3 above)                     delayed 30 min.ethylbenzyl chloride         foil  minutes                     rapid reaction with discoloration                     and gas evolution(α-chlorovinyl)toluene         foil  3 days                     pitting of aluminum and                     darkening of liquid1-(chloromethyl)naphthalene         foil  --    vigorous reaction__________________________________________________________________________ .sup.1 There was no visual evidence of reaction or corrosion of the metal even after the metal surface was scored under the liquid. The liquid itself was crystal clear and colorless. .sup.2 Crude product from vapor phase chlorination of vinyltoluene at 500° C. after lights were flashed off, contained about ten percent vinylbenzal chloride and vinylbenzotrichloride plus 0.5% each tertbutylpyrocatechol, onitrophenol, and dinitroo-cresol as polymerizatio inhibitors. .sup.3 Same results with both pure benzyl chloride and benzyl chloride containing inhibitors as in (2). .sup.4 The vinylbenzyl chloride was heated at 125° C. for 3 days with no apparent effect on the Al foil, then the benzyl chloride was adde and heating was continued. 
    
     EXAMPLE 2 
     Additional liquid phase corrosion tests were run according to the procedure of Example 1 using 0.5-1 g. coupons of various sheet aluminum alloys and of zinc. The vinylbenzyl chloride used was crude product from the vapor phase chlorination of vinyltoluene at about 500° C. from which the low boilers had been flash distilled. It contained about ten percent of higher chlorinated products, largely vinylbenzal chloride and vinylbenzotrichloride plus 0.5% each of tert-butylpyrocatechol, o-nitrophenol, and dinitro-o-cresol as polymerization inhibitors. The tests were run at 125° C. as before for 6 days. 
     
                       TABLE II______________________________________   Original    Final        AppearanceMetal   Weight, grams               Weight, grams                            Of Metal______________________________________Al 3003 0.4545      0.4545       UnchangedAl 1100 0.8380      0.8385       UnchangedAl 5052 0.8015      0.8020       UnchangedAl 2024-T3   0.5800      0.5810       UnchangedAl 6061-0   1.0200      1.0200       UnchangedAl 6061-T6   0.6845      0.6850       UnchangedZinc    0.7210      0.7695       pitted, black                            resinous layer                            on surface______________________________________ 
    
     EXAMPLE 3 
     Coupons of the aluminum alloys identified in Example 2 and a piece of wire mesh packing of 5056 aluminum clad with 6253 aluminum were placed in glass containers with both wet and dry vinylbenzyl chloride so that the metal test pieces were partially immersed in the liquid. The vinylbenzyl chloride used was the isomeric mixture of Example 1. The containers were sealed and stored at room temperature for two months. At the end of this time, there was no visible change in any of the metal test pieces. 
     EXAMPLE 4 
     Vinylbenzyl chloride vapor tests were run at various temperatures in the presence of air and nitrogen using as the test apparatus a pair of 200 ml. distillation flasks each connected to a column packed with 3003 Al rings which in turn was topped by a reflux condenser. Both condensers were connected to the same vacuum pump and pressure regulating means whereby the pressure in the system and the vapor temperature in each column was regulated. Each flask had a glass capillary through which air, oxygen, or nitrogen was admitted below the liquid surface. The vinylbenzyl chloride used was the inhibited crude reactor product described in Example 2. One hundred milliliter samples were used in each flask for the separate experiments. Results are tabulated below. 
     
                                           TABLE 3__________________________________________________________________________   Vapor Temp.ColumnGas   °C.          Time, hrs.                Results__________________________________________________________________________A    O.sub.2   125    43    some discoloration and polymerization                Al unaffectedB    N.sub.2   125    43    less discoloration, more polymerization                than A -Al unaffectedA    air   150    14    polymerized, Al unaffectedB    N.sub.2   150    14    polymerized, Al unaffectedA    air   175     4    polymerized, Al unaffectedB    N.sub.2   175     4    polymerized, Al unaffected__________________________________________________________________________ 
    
     In all six of the above experiments, the aluminum test pieces appeared to be unchanged by visual examination. Weights of the test pieces either remained the same or increased by a very small amount. 
     EXAMPLE 5 
     The general procedure of Example 4 was repeated twice at vapor temperature 125° C. and N 2  admitted through the capillary bubbler. The column in each case was packed with 5056 aluminum mesh clad with 6253 aluminum and the still flask also contained some of this aluminum. In one experiment, after 3 hrs. at reflux, 3 ml. of conc. HCl was admitted to the flask in three equal portions, then refluxing was continued for 3 hrs. In the second experiment, anhydrous HCl was admitted through the capillary bubbler for one hour, total reflux time being the same as before. 
     The concentrated HCl caused some attack on the aluminum and the liquid turned light amber in color. The anhydrous HCl apparently did not attack the aluminum and the liquid appeared unchanged. 
     EXAMPLES 6-7 
     Divinylbenzyl chloride (mixed isomers) and ar-bis(chloromethyl) vinyltoluene (mixed isomers) are contacted with coupons of aluminum under conditions described in the foregoing examples. In each case, no significant decomposition of the organic liquid or corrosion of the aluminum is observed. 
     The test described in Example 1 was repeated using the same grade of vinylbenzyl chloride and coupons of lead, tantalum, three kinds of stainless steel, tin, copper, brass, mild steel, zinc, Monel metal, and nickel. In each case, the metal surface was attacked to some extent and there was either or both of polymer formation and discoloration of the vinylbenzyl chloride. With zinc, tin, and steel, the reaction was strongly exothermic and a solid mass of cross-linked Friedel-Crafts type of polymer was formed. Results are listed in Table 4. 
     
                       TABLE 4______________________________________Metal      Results______________________________________Zinc       violent reaction with discoloration,      formation of polymer, and attack      on metal surfaceCopper     dark discoloration, some polymer formation,      metal attackedBrass      discoloration, metal attackedLead       polymer formation, metal darkenedTin        much discoloration, severe corrosion of      metal, polymer formedSteel      similar to zinc316 Stainless steel      polymer formation, some darkening of metal18-8-2 Stainless steel.sup.1      similar to 31620-Cb-3 Stainless steel.sup.2      more polymer than 316Nickel     similar to 20-Cb-3Monel      similar to 20-Cb-3Tantalum   similar to 20-Cb-3______________________________________ .sup.1 18% Cr, 18% Ni, 2% Sn .sup.2 a columbiumcontaining stainless steel produced by Carpenter Steel Co.