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Plasticized Sulfur Compositions for Traffic Marking C. KINNEY HANCOCK Texas Engineering Experiment Station, Texas A. & M. College System, College Station, Tex. THE marked increase in motor traffic since 1900 has resulted It is believed that Koebig's procedure is of questionable value in ever-increasing demands for suitable materials for high since, on subsequent drying, it would lead to the simultaneous way and street traffic markings to promote safer driving. Thedeposition of water-soluble matter along with the water-insoluble magnitude of this problem, in terms of cost of materials and of pigment and this would result later in disintegration of the pig labor, is not generally appreciated. For example, the highway ment by leaching action of rain. motorist who relies so much on the center line traffic stripe of a As a source of yellow aggregate, crushed, integrally colored two-lane highway knows little about the cost and effort required concrete appeared to be of some interest. Mortar briquets were for its installation and maintenance. According to a practical made using yellow pigment and white Portland cement along with formula used by highway paint engineers, the number of gallons either sand or small limestone chips. After curing, the briquets of paint required per mile for a continuous 4-inch traffic stripe is were crushed and tested for color retention and for resistance to approximately equal to the thickness of the applied paint film in loss by abrasion. Satisfactory color retention was found for mils. several commercially available yellow cement colors, and the Much research has been, and remains to be, carried out on crushed aggregate from colored briquets showed resistance to loss traffic marking materials. The principal factors of interest are: by abrasion equal to or greater than that for crushed aggregate color and color retention, both day and night visibility, resistance from uncolored control briquets. However, as the crushed, yellow to weathering and traffic abrasion, and quick drying without ac aggregate showed much greater loss by abrasion than did crushed companying difficulties in application. The literature concerning limestone aggregate, no more studies were made along this line. these factors is abundant; a compact treatment may be found in Sulfur appeared to be a promising material for yellow traffic ten articles and an annotated bibliography of the Highway Re markings because of its low cost, stability, yellow color, and shorl search Board (7). setting-up time. The natural color is not sufficiently intense for For several years, the Texas Engineering Experiment Station traffic marking, but is helpful in that leas additional yellow pig has conducted studies of traffic marking materials. Keese and ment would be required to obtain the desired color. In spite of Benson (8, 9) have reported successful results of one of these its low cost, sulfur has been in short supply until recently, when studies which led to the development of a very serviceable hot- the situation eased up considerably, melt rosin-alkyd resin striping composition. The present article The results of preliminary' traffic marking tests with molten is concerned with another aspect of this research. sulfur alone were not encouraging because, after solidifying, the The study reported herein was concentrated on the develop sulfur was not bonded satisfactorily to the pavement and more ment of a more suitable yellow striping material to be used as a over was brittle and underwent early and extensive loss by traffic dash stripe next to and parallel to the highway center stripe to abrasion. If the sulfur was overheated during the melting opera Indicate no-passing zones in areas where visibility ahead is in tion, the resulting viscous product was dark in color and showed sufficient for safe passing. This method for marking no-passing no better service performance as a traffic marking material than zones is the practice of the Texas Highway Department. that discussed above. In this connection, the viscosity-tempera For many years, the Texas Highway Department and others ture behavior of liquid Bulfur, as found by Bacon and Fanelli (1). have used a very serviceable white center line stripe whioh is is of interest. At the melting point (119 C.) liquid sulfur has a laid by first striping the pavement with hot asphalt and then ap viscosity of about 11 centipoises. With rising temperature, the plying a layer of small, crushed limestone aggregate, most of viscosity slowly falls to about 9 centipoises at about 158 C., then which is cemented in place as the asphalt cools. Surface traffic rises rapidly to about 93,200 centipoises at about 187 C., and abrasion of the relatively soft limestone serves to restore the thereafter falls rapidly. white color and offset traffic soiling. Moreover, the slight eleva tion of this stripe above the pavement is of some value to the motorist, in that it "tells" him when he has unintentionally SULFUR PLASTICIZERS passed over the stripe. For the present study, the success of this In view of the unsuccessful results obtained with molten sulfur white stripe directed interest toward the development of a similar alone, it appeared necessary to plasticize the sulfur by adding a stripe using yellow aggregate. It was found that limestone ag suitable material. The following materials have been tested as gregate could be stained by impregnating the aggregate with an plasticizers of sulfur: Thiokol Type A (polyethylene tetrasulfide). ammoniacal solution of an ammonia-soluble, water-insoluble yel Thiokol Type A plus wood rosin, fcrf-butyl polysulfides (14), low pigment (such as zinc chromate), draining, and then allowing Aroclor (chlorinated diphenyl), Halowax (chlorinated naphthal the ammonia to evaporate. On crushing the dried, stained ag ene), wood rosin, natural rubber, Butyl rubber, olive oil, dibutyl gregate, it was found that the staining did not extend far below phthalate, p-dichlorobenzene, and alkyd resin (No. 31 Solid Beck- the surface. As a result, further study along this line was aban osol, Reichhold Chemicals, Inc.). doned, as integral staining was needed in order to achieve the In most cases, the results of small scale laboratory tests were color-restoring feature resulting from traffic abrasion. The above- sufficient for tentative evaluation of the material as a plasticizer described method of staining aggregate is a simpler variation of of sulfur. These tests involved melting the mixture, thoroughly that of Koebig (11), in which the aggregate is impregnated with a agitating, making a smear on a concrete test block, and then ob mixture of ammonia and solutions of two salts which will form, serving the time-oooling behavior of the mixture while stirring by metathesis, the water-insoluble, ammonia-soluble pigment. after heating was discontinued. A powdery or brittle smear with 2431 2432 INDUSTRIAL AND ENGINEERING CHEMISTRY Vol, 46, No. 11. no appreciable lowering of the solidifying point of the sulfur was considered sufficient to discard the material. In some cases, it was visually apparent that the sulfur and additive were incom patible. In more promising oases, larger batches of molten mix ture were prepared and test traffic stripes laid in order to observe performance under traffic loads. The first three of the above-listed materials showed the best plasticizing action on sulfur. Initial results with sulfur plasticized with teri-butyl polysulfides showed great promise, but this indica tion was short-lived, for test traffic stripes laid with such com positions failed rapidly after rains, owing to water solubility of the plasticizer. Succeeding studies were largely concentrated on the use of Thiokol Type A a9 a plasticizer. Recently, some very prom ising results have been obtained by using Thiokol Type A with wood rosin for plasticizing sulfur. Credit for the use of Thiokol as a sulfur plasticizer is due Rueckel and Duecker (13), who used a mixture of 60 parts of sulfur, .10 parts of Thiokol, and 30 parts of aggregate as a jointing material for clay products. YELLOW PIGMENTS FOR PLASTICIZED SULFUR Very good results were obtained with two pigments of the Hansa Yellow type: Reichhold's 1550 Hansa Yellow (the cou pling product between diazotized p-nitroaniline and acetoacetanilide) and Du Pout's Toluidine Yellow YT-445-D (the coupling product between diazotized -ra-nitro-p-toluidinc and acetoacetanilide). Contrary to expectations, cadmium sulfide was unsatis factory. The yellow inorganic chromate pigments were of specu lative interest, but they were not tried because of skepticism con cerning the advisability of heating a mixture of sulfur, organic plasticizer, and a metallic chromate. Moreover, technical per sonnel of the Texas Gulf Sulphur Co. (3) questioned the advis ability of using chromates for the purpose. Kobbe (10) claims that certain aromatic diamines ore miscible with and react with sulfur at about 200 C. to form a yellow color. This method for coloring sulfur was not tried in the present study because it was not considered advisable to heat the sulfur above about 155 C. EXPERIMENTAL PROCEDURE Usually, 600- to 1200-gram (not including glass beads or filler) batches of plastioized sulfur were prepared, using l-quart motor oil cans for containers. Larger batches were prepared in 40ounce cans. For convenience on the small scale, crude sulfur (09.5 to 99.9% sulfur) was crushed to pass a No. 10 sieve. The sulfur was mixed thoroughly with the pigment on a flat surface and the mixture transferred to tho can and placed in a 2-quart mineral oil bath. A desiccator plate in tho bottom of the bath supported the can and prevented local overheating of the sulfur. The mixture was melted and mixed without allowing the oil bath temperature to exceed 100 C., this maximum bath temperature applying throughout the remainder of the procedure. The plasticizer was added in small portions with good stirring. When Thiokol Type A was used, in spite of slow addition with stirring, the majority of this plasticizer balled up and did not begin to disperse into the sulfur until stirring had been prolonged; thereafter, the Thiokol dispersed rapidly to give a viscous mix ture, depending on the percentage, which finally became more mobile after further stirring and heating. Considerable frothing always occurred during the addition of Thiokol to the molten sulfur. Technical personnel of the Thiokol Chemical Covp. (15) attribute this frothing to entrapped air in the Thiokol, which is in agreement with observations made in this study. Other additives, if used, were incorporated into the molten mixture and the material taken from the laboratory to the test area (streets on the campus of the A. and M. College of Texas). A portable gasoline camp stove was used to keep tho mixture hot until used. The pavement was swept and a 4-inch transverse stripe was laid from the center line of the street toward the curb, using a wooden screed box (inside dimensions: 4 inches wide, 5 inches long, 4 inches deep) with a steel gate which could be raised or lowered to control the film thickness. The excess of plastic material in the can was kept for compari son in observing the color retention of the test stripe. After lay ing. the test stripes were observed at various times for resistance to traffic abrasion and for color retention. As reported in the tables, per cent loss indicates the percentage of exposed pavement within the area which was originally covered by the stripe. In most cases where beads had been used in the plastic mixture, ad ditional beads were sprinkled on the hot test stripe immediately after laying. About 1100 vehicles passed over these test stripes daily. The approximate traffic classification was: 90% passenger cars, 7% trucks, and 3% busses. BACTERICIDES AND OTHER ADDITIVES Previously reported evidence indicates that traffic stripes laid with plasticized sulfur compositions might undergo bacterial at tack that would result in deterioration and loss of bond to the pavement. Beckwith and Bovard (2) attributed breakdown of pipeline joints to bacterial attack upon the sulfur-containing seal ing compound. Duecker and associates (4) and Frederick and Starkey (6) found that sulfur sealing compounds were attacked hy the sulfur bacterium Thiobarillus thiooxidans. Both groups of these investigators found that bacterial attack could be retarded or prevented by the use of suitable bactericides. Duecker and associates concluded that the use of water-soluble salts, as bac tericides, in sulfur cements is deleterious. Of a large number of bactericides tested, Frederick and Starkey found Monsanto's Santobrite (sodium pentaehlorophenate) most effective. In this study, Monsanto's Santophen 1 (o-benzyl-p-chlorophenol) and Dow's Dowicide 7 (pentaclilorophenol) were tested. Results indicate that the presence of a small amount of either of these bactericides is beneficial. Serviceable plastio compositions resulted when powdered silica and Ottawa sand (20- to 30-mesh) were tested as fillers for plasti cized sulfur. In many tests, glass beads (largely 20- to 50-mesh) have been UBed in plasticized sulfur compositions to improve night visibility of the resulting traffic stripe. The use of both glass beads and Ottawa sand in traffic stripes resulted in greater impairment of color as the result of accumulation of foreign matter on the rough surface. RESULTS In addition to very extensive small-scale laboratory tests, 99 traffic test stripes were laid during this investigation. The serv ice performance of the majority of these stripes led to the re jection or further study of certain materials or of processing con ditions; the conclusions reached have been discussed semiquantitatively above. Data for certain other representative traffic test stripes are presented below. In a series of experiments, mixtures of 855 grams of crude sulfur, 45 grams of Thiokol Type A, 3 grams of bactericide (except as noted), and 200 grams of beads (except as noted) at about 130 C. were used to lay 4-inch transverse traffic stripes with ii film thickness of 0.5 mm, Except as noted, beads were sprinkled onto the stripes immediately after laying. In all eases, the stripes had set up and were ready to receive traffic within 5 minutes after laying. No pigment was used in any of the stripes and they all showed a fair light olive-vellow color. The variable factors and results of observations of loss by traffic abrasion and weathering are shown in Table 1. The results of the 45- and 67-week observations are misleading and are unfair as concerns the merits of the test stripes. Some time prior to the 45-week observation, construction was begun on a new boulevard which was designed to intersect the test stripe area. During this construction, the test stripes wore sub jected to abnormal wear from heavy construction equipment and this contributed an undetermined amount to the large losses ob served after 45 and 67 weeks. These eight stripes suffered considerable traffic discoloration November 1954 INDUSTRIAL AND ENGINEERING CHEMISTRY 2433 Table I. Performance of Traffic Stripes without Pigment No. of Test Bactericide Loss after Weeks Indicated, % 10 29 34 45* 07" 148* None 15 80 85 149* Dowicide 7 25 80 85 150 i> Santophen 1 25 80 90 157 Santophen 1 1 10 10 32 00 158 Dowicide 7 0.5 10 20 35 07 159 None O.o 20 32 55 76 mc Dowicide 7 0 0.5 3 15 85 101e N one 2 20 30 40 95 with increasing content of Thiokol. From over-all summer re sults of this project, it has been noted, as a very rough approxima tion, that the setting-up time in minutes is about equal to the percentage of Thiokol in the plastic mixture. Tile results of test stripes laid with compositions contain ing some other plasticizers are shown in Table III. The stripes were laid with 600-gram portions of molten mixture at about 130 C. The gate opening on the screed box was 0.5 mm., but spreading occurred after laying in most cases. All of the stripes set up in leas than 3 minutes and showed a fairly good " See discussion. * No beads used. c Laid on asphalt pavement, other stripes laid on conorete pavement. lemon-yellow or light olive-yellow color. No pigment, bactericide, or beads were used in these stripes. Table II. Performance, of Traffic Stripes with Pigment No. of Test Type of Pavemeat Bactericide Loss after Weeks Indicated, % 8 12 10 20 29 34 39 45 49 07 119*c 120 *. 152* 153* 155* 156* Asphalt Concrete Asphalt Concrete Asphalt Concrete None None Santophen 1 Santophen 1 Dowicide 7 Dowicide 7 5 , . 25 50 70 75 0 .. 0 67 .. io 70 12 75 20 87 30 0 . . 4 5 25 45 0 . . 20 22 25 35 0 .. 2 5 25 00 See disoussion in connection with Table I, * No beads added to plastic mixture before laying. c Toluidine Yellow YT-445-D used. * 1650 Hansa Yellow used. The results shown in Table III indicate that the Aroclors and Halowaxes, in the concen trations and under the condi tions used, do not have suf ficient plasticizing action on sulfur. The results of tests 130, 128, 142, and 131 show no significant difference in per formance of the compositions on asphalt pavement as com pared to that on concrete during the first, few days after laying, but thereafter the color progressively improved from weathering and traffic abrasion until it was as good as (in some cases, better than) the original color. The results of the first three tests strongly indicate that glass beads increase service performance in addition to improving night visibility. From the results of tests 159 and 161, it appears that the addition of bactericide is beneficial, but there is insuffi cient evidence from other tests to warrant a comparison of the effectiveness of the two bactericides used. In another series of tests, mixtures of 792 grams of crude sulfur, 90 grams of Thiokol Type A, 18 grams of pigment, 3 grams of bactericide (except as noted), ana 200 grams of beads (except as noted) at about 130 C. were used to lay 4-inch transverse traffic stripes with a film thickness of 0.5 mm. In all cases, beads were sprinkled onto the stripes immediately after laying. All of the stripes had set up and were ready to receive traffic within 5 to 10 minutes after laying, and all showed a good olivevellow color. pavement. The results of some recent tests with compositions containing small amounts of wood rosin show considerable promise. It will be necessary to observe the test stripes for a much longer period before a true evaluation can be made, but the results to date are of interest. Using a mixture of 1200 grams of plasticized material plus 300 grams of beads, 4-inch transverse stripes with a film thickness of 1 mm. were laid at 140 C. on concrete pavement. Additional beads were sprinkled heavily on the stripes immediately after laying. All of the stripes were set up and ready to receive traffic within 15 minutes after laying. The variable conditions of laying and the results of observa tions to date are shown in Table IV. All these test stripes showed a good yellow at first, and under went early traffic discoloration, but gradually the color returned more or less to the original. These stripes show fairly good light reflectance from the beading. From the results to date, it ap- The variable factors and results of observations of loss by traffic abrasion and weathering are shown in Table II. It is apparent from Table II that stripes represented by tests 119 and 120 were inferior to the other four. Evidence from other Table III. Tests with Othf.r Plasticizers experiments has shown that Toluidine Yellow-YT-445-D and 1550 Hansa Yellow have about the same merits as pigments for plas ticized sulfur, so the early failure of these two stripes cannot be attributed to the use of a different pigment. In view of the results shown in Table I, it is concluded that the poor performance of these two stripes was due to the absence of both bactericide and Compoaition, % No. Crude Thio of sul- kol Test fur A Other plasticizer 5 140 95 0 Aroclor 1254 5 141 95 0 Aroclor 1260 Loss after Weeks Indicated % 59 17 30 3f) o 90 93 95 12 60 65 92 beads in the plastic mixture. The results shown in the last four lines of Table II indicate slightly better performance on concrete pavement than on asphalt pavement. All six of the stripes under went early traffic discoloration, but the color soon recovered and held up fairly well thereafter. Perhaps, the early traffic dis coloration (nearly always noted) might be corrected by using a surface drier--e.g., a cobalt drier; however, Keese (8) made such studies with hot-melt rosin-alkyd resin striping compositions and obtained results which were largely inconclusive. These six plastic compositions containing 10% of Thiokol Type A (excluding the beads) striped well with the screed box and did not spread after laying. On the other hand, considerable 130 95 0 Aroclor 5460 5 128 95 0 Aroclor 5460 10 67 80 90 10 75 92 97 142 95 0 Halowax 1000 I 40 50 8S 131 95 0 Halowax 1001 10 50 60 80 132 95 0 Halowax 1001 10 33 50 85 10 138 90 0 Aroclor 5460 10 80 85 95 _ 140 90 5 Aroclor 1264 0 147 90 5 Aroclor 1260 0 1 50 65 0 0 40 50 143 90 5 Aroclor 5400 0 45 50 52 145 90 5 Halowax 1000 0 5 50 50 spreading after laying occurred with the compositions containing 144 90 5 Halowax 1001 0 10 40 50 5% of Thiokol Type A (see Table I). At the same time, however, Laid on asphalt pavement, other stripes laid on conorete, the setting-up time required before opening to traffic increased 2434 INDUSTRIAL AND ENGINEERING CHEMISTRY Vol. 46, No. II Table IV. Results with Sulfur-Thiokol Type A.-Wood Rosin- Mixtures N'o. of Test Composition of Plastic Mixture, % Crude Thiokol Pig- Bacteri- Wood sulfur cide rosin 172" 176 82.6 76 12 15 o5b6 0.5* 0.5* 0 3.5 178 84.6 10 36 0.5<* 2 179 82.5 12 3 0.5<t 2 180/ 82.5 12 3 0.5<* 2 181* 82.5 12 3' 0.3<f 2 a Pavement swept only. 6 1550 Hansa Yellow'. c Dowicide 7. * Santophen 1. e Tohnaine Yellow YT-445-D. / Swept, scrubbed, and dried with blowtorch. a Swept, scrubbed, and air dried. 8 42 0 0 0 0 0 Loss after Weeks Indicated, ' u 14 .16 21 26 30 55 70 85 85 87 88 00 000 1 00 1 2 6 0 8 IS 20 30 36 0 0 (1 0 0 0 000000 30 93 2 13 43 0 3 41 93 4 24 0 10 Duecker and Schofield (5). in discussing the use of plas ticized sulfur (60% sulfur, 10% olefin polysulfide, and 30% aggregate) as a jointing material for clay products, re ported that the applied com position emitted a rather ob jectionable odor. In the pres ent study in which heating temperatures were kept below 1603 C., some objectionable odor was noticed during plas ticization and application, pears that the incorporation of a small amount of wood rosin is beneficial. The film thickness was greater and the laving temper ature higher than in previously reported tests. but none was observed after application. Probably, the objectionable odor reported by Duecker and Schofield (5) resulted from decomposition caused by higher processing temperatures. The results of tests 179, 180, and 181 are of interest because the only difference in these three tests was in the pretreatment of the pavement. The late partial failure of stripe 181 may be The service performance of the traffic stripes described in this article was determined under rather severe conditions. The ob ject of the project was to develop a more suitable material for the largely attributed to faulty laying which resulted from fouling of yellow dash stripe parallel to and immediately adjacent to the the screed box. From these results, it appears that the pavement highway center stripe, but all test stripes were laid at right angles should be washed before the stripe is laid, but this indication is to the center stripe. In all cases of slight or moderate loss by inconclusive in view of the results of tests 176 and 178 and earlier traffic abrasion, practically all such loss occurred in the rather tests. narrowly defined tire lanes where the traffic load was high. Other Paint Stripe Controls. N'o traffic test stripes, using conven portions of these stripes were subjected to occasional traffic loads, tional traffic paints, were laid in this project, but this was un which were, however, probably more frequent than the traffic necessary, as Keese (8), working on a parallel project, laid several loads received close to and parallel to the center line. Usually, in representative traffic paint test stripes in the same test area and such cases, no loss occurred in the 1- to 2-foot sections next to the at the same time. A chlorinated rubber traffic paint test stripe center line and next to the curb. had an effective life of 7 months, while a stripe laid with Pliolite traffic paint gave about 10 months of effective service, Several SUMMARY other traffic paint test stripes had to be repainted several times during 8 to 10 months of testing. It is evident from Table IV that some of the plasticized sulfur test stripes have given 10 months or more of effective sendee. Performance tests with plasticized sulfur compositions indicate that such materials aro promising as traffic marking materials. Optimum results are obtained with a sulfur composition contain ing 5 to 15% of Thiokol Type A, 1 to 3% of a Hansa Yellow' type DISCUSSION The studies reported in this article were conducted on a small laboratory-field scale. Studies of larger scale apparatus were not made because Keese (8) had already developed a simple, service able machine for the purpose and also because of the assurance by highway engineers that the required apparatus would be pro vided if plasticized sulfur proved to be useful for traffic marking. Certainly, uniform heating will be a problem in preparing and laying molten sulfur compositions. As direct heating is appar ently not feasible, an oil-jacketed kettle will probably be required to prevent local overheating. Because of this heating problem, some early studies were made with carbon disulfide solutions of sulfur. Such solutions were used to paint stripes on pavement, but the resulting film was excessively thin even after several ap plications of the solution and extensive loss from traffic abrasion and weathering occurred almost immediately. In an effort to improve such solutions for traffic marking, unsuccessful attempts were made to incorporate wood rosin in carbon disulfide solutions of sulfur. It is believed that the development of a cold-mix plastic sulfur pigment, and 0.5% of a suitable bactericide. The incorporation of glass beads results in fairly' good light reflectance; beading increases the effective life of the material. The results of recent tests, which will require longer observation, indicate that the in corporation of about 2% of wood rosin is significantly beneficial. The rosin has an auxiliary' plasticizing action which results in better retention of bond to the pavement and smaller loss by fracture from traffic loads. Traffic stripes laid with such materials show' a good initial yel low color, but early traffic discoloration occurs; how'ever, the initial color is restored to some extent by weathering and traffic abrasion. The use of surface drying materials for correcting the early' traffic discoloration should be investigated. These plastic sulfur compositions show about the same per formance on both asphalt and concrete pavements. With Thiokol Type A contents of 5 to 15%, the setting-up time in minutes re quired before opening to traffic is very roughly equal to the per centage of Thiokol. The film thickness can be controlled well with compositions containing 8 to 15% of Thiokol, but w'ith 5% or less, considerable spreading after laying occurs. composition deserves further investigation. Recently, Massa, Colon, and Schurig {12) reported on the results of an extensive ACKNOWLEDGMENT study of Thiokol polymers dispersed in solvents containing other The author is grateful to the many companies and individuals resins as protective coatings for steel. An appropriate adaptation who generously' gave technical information and materials for the of their technique might lead to a successful method for cold studies, and acknowledges the assistance of the following student mixing plastic sulfur compositions. Unsuccessful tests were made technicians whoworked on the project at various times: R. L, of sulfun-Thiokol Type A compositions as coating materials for Burdick, J. R, Eccles, J. E. Halkias, A. B. Hoefelmeyer, R. B. steel. However, no primers were used in any of the tests, though Johnson, L. D. Ross, E. V. Ruhnke, E. E. Schilhab, and B. E. Massa and associates found that primers were required for coating Zimmerman. Laboratory facilities were provided by the De steel. partment of Chemistry', A. & M. College of Texas. November 1954 INDUSTRIAL AND ENGINEERING CHEMISTRY 2435 LITERATURE CITED (1) Bacon, R. F., and Fanelli, 11., J. Am, Chem. Soc., 65, 639 (1943). (2) Beckwith, T. D,, and Bovard, P. F., Chem. <& Met. Eng., 40, 530 (1933). (3) Duecker, W. W,, private communication, Oct. 28, 1952. (4) Duecker, W. W., and assooiates, J. Am. Water Works Assoc., 40, 715 (1948). (6) Duecker, W. W., and Schofield, H. Z., Bull. Am. Ceram. Soc,, 16, 435 (1937). (6) Frederick, L. R., and Starkey, R. L., J. Am. Water Works Assoc., 40, 729 (1948), (7) Highway Research Board, Washington, D. C., "Pavement Marking Materials," Bull. 57 (1952). (8) Keese, C. J., Roads and Streets, 95, No. 10, 66 (1952); Texas Eng. Expt. Sta., Bull. 130 (March 1953). (9) Keese, C. J., and Benson, F. J,, Highway Research Board, Bull. 57,49 (1952). (10) Kobbe, W. H., U. S. Patent 1,655,504 (Jan. 10, 1928). (11) Koebig, J,, Ibid., 1,577,729 (March 23, 1926). (12) Massa, A. P., Colon, H., and Schurig, W. F., Ind. Eno. Chem., 45, 775 (1953). (13) Rueckel, W. C., and Duecker, W. W., Bull, Am. Ceram. Soc., 14,329 (1935). (14) Schulze, W. A., Short, G. H., and Crouch, W. W., Ind. Eno. Chem., 42, 918 (1950). (15) White, R. S., private communication, Dec. 1, 1953. Received for review February 6, 1944. Accepted June 10, 1954. Presented before the Engineering and Industrial Section of the American Chemical Society Regional Conclave, New Orleans, La., December 11 1943. Sulfonation Products from Polymers of Styrene and Vinyltoluene . H. H. ROTH Physical Research Laboratory, The Dow Chemical Co., Midland, Mich. THE tonnage quantity production of polystyrene, as well excellent work of Signer and Demagistri (18) which discusses as its low price, has made it look attractive as a starting the properties of noncrosslinked sulfonic acid derivatives of a material for a new synthetic gum. Coupled with this is themolding grade polystyrene. Jones (12) discusses the production further potential lowering of price due to the use of low-priced of other water-soluble derivatives of polystyrene by chloro- sulfonating agents which are available to convert the polystyrene methylation and subsequent amination. to water-soluble products (98% sulfuric acid at 1 cent, chlorosul- This paper discusses further the production of noncrosslinked fonic acid at 4 cents, and sulfur trioxide at 3 cents). As a syn sulfonation products of molding grade polystyrene as well as thetic gum the sulfonation products should find application as other products of comparable linearity. The products under aqueous thickeners, impregnants, adhesives, and textile sizes. discussion could not be produced in the author's laboratory by They may be produced as a white powder which readily dissolves any of the methods of sulfonation taught in the available pat in cold water. Their solubility is little affected by acid, alkali, ents (1, 2, 7,16,17, 21, 23). It was only upon the development or temperature. Because they are polyelectrolytes, they also of a new sulfonation technique (mixed solvents of Method B) that have potential application in soil conditioning. It was the po it became possible to sulfonate polystyrenes without undue tential wide utility of the sulfonation products that attracted this crosslinking. laboratory to studies in this field. Because of the competitiveness of the market today, a new METHODS OF SULFONATION synthetic gum will be required to meet rather stringent specifica tions. One of these will be water viscosity. As sulfone cross linking during sulfonation will cause the water viscosity of the sulfonation products to vary over an extremely wide range of values, it is ofgreat importance to prevent the side reaction, particu larly where commercial production is desired. Heretofore it was deemed necessary to sulfonate only to the extent of water solu bility in order to have a marketable product, while the problem of crosslinking was almost universally ignored. The present lack of commercialization is probably due to an inability of known sulfonation processes to prevent or control this crosslinking. Not only is the prevention of crosslinking necessary from a processing viewpoint, but the noncrosslinked products are also more de sirable, They have a molecular configuration which is the same as the well known polystyrene molecule, their water viscosity is dependent upon the molecular weight of the starting polymer, and their behavior a8 a polyelectrolyte becomes predictable. The sulfonation of polystyrene to produce water-soluble prod ucts has been the subject of several patents (1, 2, 7, 16, 17, 21, S3). These patents and others (3, 4, 8, 9, 11, IS, 15) show the potential, and some proved, utilities of the sulfonation products. Also of interest should be the patents eoneerning sulfonation Method A. Dissolve 10 grams of Styron 666 ia 480 ml. of dry carbon tetrachloride. Adjust to the desired temperature and agitate in a jacketed Waring Blendor jar with blades rotating at about 1650 r.p.m. To this solution add 200 ml. of dry carbon tetrachloride containing 6.6 ml. of monomeric sulfur trioxide over about a 10- to 15-mmute period of time. Dry nitrogen is blanketed over the surface of the solvent to minimize moisture pickup during the sulfonation. Allow the slurry to agitate for 10 minutes after the sulfur trioxide solution has been added. Drain the excess carbon tetrachloride from the sulfonation roduct. Immediately disperse the product in dry ether, everal extractions are necessary to purify to a sulfuric acid- free product. The final product is a white powder of low volume density. Method B. Dissolve 10 grams of Styron 666 in 300 ml. of dry carbon tetrachloride. Transfer the solution to a glass-lined pressure vessel containing an agitator. To the solution in the sealed pressure vessel add 240 ml. of liquid sulfur dioxide under pressure. Adjust the contents in the vessel to the desired temperature and agitate at about 2200 r.p.m. To the polymer solution add 400 ml. of liquid sulfur dioxide containing 6.6 ml. of substantially pure monomeric liquid sulfur trioxide over a 5- to 10-minute period. Agitate further for 10 minutes and then cool the vessel to below --10 G. Remove the slurry, filter, and purify the sulfonation product in dry ether. The final product is a white powder of low volume density. products of copolymers of styrene and maleic anhydride (10) Method C. The sulfonation temperature of about --10 C. and of polymethylstyrene (19). Of the considerable literature allows the handling of liquid sulfur dioxide in open vessels. At now available on this subject, almost all is contained in patents. this temperature it was found desirable to modify Method B to Only one paper has been published to date on the subject--the a concurrent reactant feed mode of sulfonation. This minimizes