Patented Nov. 5, 1946 2,410,408 ' PATENT orric' UNITED STAB John R. Durland, Nitro, w. V8", assignor to Mon santo Chemical Company, St. Louis, Mo., a cor poration of Delaware No Dra. Application March 1, 1944, Serial No. 524,637 8 Claims. (Cl. 260-6685) The present invention relates to the stabiliza tion of vinyl compounds and to the stabilized compounds have been found to possess mar inhibiting action when incorporated into mono compositions so produced. meric styrene. It is to be understood that the - It is well known that vinyl ‘compounds as for above are merely illustrative of the invention and example vinyl esters, and vinyl aromatic com Cl other phenolic sul?des can be usedwhere con pounds such as styrene, its homologues and venient or desirable. , analogues tend to polymerize on standing. In The phenolic sul?des do not discolorvinyl com the manufacture of vinyl polymers premature pounds and are therefore eminently suitable for polymerization even to a very slight extent may incorporating into the compositions prior to stor render the monomer un?t for use since it may age. In addition, they are e?ective at elevated seriously a?ect the properties of the ?nally polyf merized product. For this and other reasons it temperatures as for example 100° (It-200° C. as well as at storage temperatures and effectively is essential to prevent premature polymerization prevent polymerization during distillation. They and for this purpose it is common practice to add are easily removed during distillation of the vinyl compound and in noway a?ect the polymeriza tion of the distilled products. The amount oi’ in hibitor to be used will of course vary according to the particular composition and conditions un an inhibiting agent to the liquid monomer. An object'of this invention is to provide a new and improved class of inhibiting agents. A further object of the invention is to provide a class of cheap materials' which are effective _ der which it is to be used'but in general propor inhibiting agents. A still further ‘object is to 20 tions within the range of 0.001 to 5% are satis provide a class of inhibiting agents which are easily removable from the liquid monomer after which the polymerization reaction can be carried out in a normal manner. Other and further ob jects will be apparent from the description fol lowing. In accordance with this invention it has been found that phenolic sul?des e?ectively inhibit the polymerization of vinyl compounds during stor- ~ factory. Often the merest traces are sumcient to prevent polymerization entirely. _ . Among vinyl monomers which can be preserved by incorporating therein a phenolic sul?de are . vinyl acetate, divinyl benzene, ¢~methyl styrene, p-methyl styrene, ethyl vinyl benzene, vinyl naphthalene, p-chloro styrene and the like. Asspeci?c examples of the invention which il lustrate the inhibiting power of phenolic sul?des age, shipment and distillation. The monosul?des 30 but which are not to be taken as limitative of the are the most effective and are therefore preferred invention, 0.250 part by weight of inhibitor was but higher sul?des as for example disul?des and polysul?des of phenols can be used with good rile-l" suits. One or more hydroxy groups may be pres charged with 25 parts by weight of freshly dis , tilled styrene into screw cap bottles of suitable capacity having the caps lined with tin foil. The samples were then immersed in a boiling water stituents such as alkoxy, alkyl and halogen ‘bath for a total of 20 hours. Viscosity tests were groups. In general, the phenolic sul?des possess then made at25° C. with a 10 ml. analytical the type formula = pipette measuring the time of ?ow from the up— per mark to a lower mark just below the bulb. where :c and n are integers or polymers or this 40 For monomeric styrene the time of ?ow was 11.5 seconds. The viscosities in the table below are nucleus, expressed as relative values with monomeric ent in the aromatic nucleus as well as other sub Typical examples of phenolic sul?des which can be used in the practice of this invention com styrene as one. As afurther measure of the in I hibiting action the polystyrene content was deter 45 mined by distillation. prise the following: di-(o-benzyl phenol) mono sul?de; di~(p. t-butyl catechol) monosul?de; di _ Inhibitor carvacrol monosul?de; di-catechol disul?de; dl~ catechol monosulilde: di-m-cresol monosul?de; may] catechol) mono'sul?de--.“ 1 dl-o-cresol monosul?de; di(di-t-butyl catechol) 50 Dl-(p. Dl-catechol monosul?de.._ _ .. monosul?de; di-?-hydroxy naphthyl disul?dc; (ii-phenol monosulflde; di-thymol monosuliide: Relative vim‘iw Polystyrene percent ' 1.01 0. so 1. 02 0. 45 ._ _. l. 02 l. 10 0. 85 O. 50 Di-thymol monosulilde ................ . - l. 03 0. 00 1.00 0.05 Di-m-cresol monosul?dc____ Dl-o-cresol' monosul?de.__ monosul?de of catechol monobenzyl ether; di Monosuliide cl cstechol monobenzyl ether .......... -. .............. ..‘ .... _. hydroquinone disul?de and di(2-methyl, 4 t butyl) phenol disul?de. All of the foregoing 65 2,410,405 . ' 3 4 By way of comparison styrene without an in Other polymerizable vinyl compounds can be hibitor was too viscous for test after heating for stabilized with the new inhibitors and other the same length or time. phenolic sul?des used. The method of adding Storage tests were carried out employing the inhibitor can be varied widely. This inven phenolic sul?des as storage inhibitors. Freshly 5 tion is limited solely by'the claims attached here distilled styrene was stored in the dark at ap to as part of the present speci?cation. proximately 25" C. in contact with 24 gauge sheet What is claimed is: ' steel. 0.01% oi’ inhibitor was incorporated into ’ 1. A liquid composition comprising a styrene the styrene and samples tested periodically for monomer and a proportion of a monosul?de of a. increase in viscosity. The condition _ of the i0 dihydric phenol su?icient'to inhibit polymeriza styrene showed no change after many months tion. ' storage. The results are summarized below: 2.'A liquid composition comprising a styrene monomer and a proportion of a monosul?de of a new °°““§££t3i°°“" monohydrocarbon substituted dihydric phenol .5 ‘suiiicient to inhibit polymerization. ‘ _3. A liquid composition comprising styrene monomer and a proportion of a, di-(p-tert. butyl None........................ -- swam.-." Visoousliquid. Do.... .............. thrash..-“ Solid. catechol) monosulilde sufficient to inhibit poly-- ‘ Di-g?tsbutylcatechol) mono- wmonths ._ Noapparentchange. Di-mcesol monosuliide ..... .. 10 months -Di-o-cresolmonoslniide ...... .- 10 mon Di-thymol mouosul?de ...... __ lilmonths--- "Dig-Iggy] m-cresol mono- 10 mon __ Di-carva'crol monosul?de ____ _. 10 months--. Do. Do. Do. merization. 20 Do. Do. - 4. A liquid composition comprising styrene monomer and a proportion 01’ di-catechol mono- ' sul?de su?lcient to inhibit polymerization. 5. The method of preventing polymerization of a styrene monomer which comprises incorporat It was iurther noted that the addition-oi the 25 ing therein a, proportion of a monosulilde of a inhibitor caused no discoloration and after ten months storage the styrene compositions contain- > diihydric phenol su?icient to inhibit polymeriza t on. > > ing the inhibitor were still perfectly colorless 6. The method of preventing polymerization of watery liquids. These results show that very a styrene monomer which comprises incorporat small proportions oi phenolic sul?des effectively 80 ing therein a proportion of a monosul?de of a preserve-styrene during storage. In this connec monohydrocarbon substituted dihydric phenol tion, mention should be made of the fact that vsu?icient to inhibit polymerization. Y the inhibitors may be employed in proportion 'I.‘ The method of preventing polymerization of su?icient to stabilize the vinyl compound at room styrene monomer which comprises incorporating temperature, or thereabout, but in proportion in- 35 - therein a proportion 01' di-(p-tert. butyl catechol) suilicient to stabilize the composition at elevated monosulfide su?icient to inhibit polymerization. temperature in which case the stabilizing agent 8. The method of preventing polymerization of need not be removed. The composition may when styrene monomer which comprises incorporating desired be heated to produce polymeric products therein a proportion of di-catecho'l monosul?de without removal of the stabilizing agent.’ 40 su?icient to inhibit polymerization. Again, the invention is not limited to the com positions set] forth to illustrate the invention. JOHN R. em.