Nitroparaffins and Derivatives as Heat Sensitizers for Rubber Latices ARTHUR WILLIAM CAMPBELL' Commercial Solvents Corporation, Terre Haute, Ind.
R
ECEKT research has made various nitroparaffins and For use in subsequent tests a sample of zinc oxide dispersion their derivatives available in commercial quantities was prepared by ball milling a composition prepared by the following recipe (in grams) : (3, 4), and large-scale applications for the materials are rapidly being found. A considerable number of these comZinc oxide (New Jersey Zinc Co. Horsehead Red XX4) 50 2 Dispersing Agent (Darvan, R. T: Vanderbilt Go.) pounds cause heat sensitization in rubber latices ( I ) , a Water 60 phenomenon that has been produced in the past by a number of materials (8, 5, 6) and is used extensively a t present in the I n the course of experiments on the use of nitroparaffins manufacture of foamed-rubber products. The use of nitroand their derivatives as heat sensitizers, two different samples paraffins in this application is quite new, however, and has of latex were used: Concentrated F, from the Heveatex Corporation, and Lotol NC-957, from the Naugatuck Chemirecently been the subject of extensive experimentation in this cal Company. Both had been concentrated to 60 per cent laboratory. In compounded latices it is rubber content by centrinot unusual to find three or fuging, and the former had The nitroparaffins and their derivatives been protected against coagumore different materials, each with a definite purpose. In a have been found to be heat sensitizers for lation by the addition of ammonia* study such as this, the use of latices containing zinc oxide. Of the group The compound to be tested completely latices of compounds recently made commercially was prepared in the followmould unduly complicate the problem; so an effort was made nitroethane produces gels ing manner: The latex was to avoid these complications quickly, and 2-nitro-2-methyl-l-propano1, stirred well, strained through while somewhat less active, produces a mix cheesecloth, and weighed. by running preliminary tests on that may be stored for long periods at 150 The proper amount of zinc theindividualingredientsalone without oxide dimersion was added in a latex-nitroparaffin mix. to give 2.grams of the oxide It was found that gelling could per 100 grams of dry rubber. not be produced by a nitroThe compounds to be tested as heat sensitizers were then paraffin alone, even though the test mixtures were heated for added slowly to the latex with rapid stirring. considerable periods a t 80-90" C. However, addition of a The determination of the gelling time was carried out in the small proportion of zinc oxide to these mixes quickly induced following way: Forty milliliters of the prepared latex were gelling. It was also found that the oxides and hydroxides of poured into a 25 X 200 mm. Pyrex test tube. An iron wire the elements of Periods 2-6 of the Second Group of the 20 om. long with a hook of about 1 cm. radius was placed in Periodic Table gave results similar t o those obtained with the latex. This assembly was stoppered with a cork having a zinc oxide: groove down one side, through which the wire extended. The 83 grams Formula: Lotol NC-957 test tube was placed in a thermostat at the desired tem1 Nitroethane 1 Metallio compound perature, and a t intervals the liquid was tested for gelling by 500 c. Temperature moving the wire gently up and down. Vigorous stirring was avoided, since this occasionally induced gelling. When the mass slipped readily in the tube, it was considered t o be gelled, and the elapsed time was recorded. In Table I the results of tests on a number of nitroparaffins and nitroparaffin derivatives are presented. All are shown to Compounds that roduoed no elling: be heat sensitizers. Group I NaOIf, KOH, Cuz%, AgCaHa02 I1 BeOb I n another series of tests the highly water-soluble crystalline I11 BnOs Al& Laz(SOS8 compound, 2-nitro-2-methyl-1-propanol, was used to study I V TiOz: ZrOi,'Sn(S,Oa)n, CeO, PbO, Th(N0s)r V H3vO4 AszOa Biz03 the effect of heat-sensitizer concentration on the rate of gelling V I CrOa, IhoOs, i V a ~ W ONanUOa, ~, UOa VI1 bInOz under various conditions. The results are listed in Table 11. VI11 COO, FeO, NiO Table I1 shows that compounds with a nitroalcohol concena Barium hydroxide always produced gelling when added to latex, even tration of three parts per hundred are stable enough a t room in t h e abience of nitroethane. b A 0.17 BUS ension in water was used. When carefully added t o a blank temperature for most process requirements, and other tests (no nitroet%aneY, this suspension produced gelling in 108 minutes. have shown that they can be stored a t 15" C. for more than a month Tyithout gelling. Present address, Thermatomic Carbon Company, Terre Haute, Ind. 1106
c.
1
September, 1942
INDUSTRIAL AND ENGINEERING CHEMISTRY
TABLE I. NITROPARAFFINS AND
DERIVATIVES h S
HEATSENRI-
TIZERS Concentrated F latex, .l.67 grams; sensitizer. 2) -Gelling Compound 28' C.
(Formula:
Blank Nitromethane Nitroethane 1-Nitropropane 2-Nitropropane 1-Nitro-2-methylpropane 2-Nitro-2-methylpropane 1-Nitrobutane 2-Nitrobutane I-Phenyl-1-nitroethane
Nitroparaffins No gel 48 24 48 48 ' 96 144 96 96 No gel
Halonitroparaffins 288 Chlor onitromethane 48 1-Chloro-1-nitroethane No eel 1,l-Dichloro-1-nitroethane 48 1-Chloro-1-nitropropane No gel 1,l-Dichloro-1-nitropropane No gel 2-Chloro-2-nitro~rotane 24 3-Chlo;o-l-njtropropane 48 1-Bromo-1-nitro ropane 24 I-Chloro-2-nitrogutane
e n 0 dispersion, 4: Time, Hr.50' C.
800
6.17 0.22 0.22 0.45 0.43 0.55 0.75 1.82 1.12
c.
0.13 0.05 0.07
0.07 0.07
2.77
0.10 0.10 0.08 0.08 0.08
1.17 0.50 4.60 0.50 4.60 1.35 0.20 0.35 0.35
0.07 0.10 0.08 0.10 0.10 0.10 0.05 0.08 0.08
Nitroalcohols* 120 2.20 3.33 240 4.63 288 4.53 192 4.53 288 2.13 120 192 0.47 4.03 120 96 4.03 72 0.65 120 0.53 144 0.53 0.90 216 312 2.78 .............. 264 0.37 4-Nitro-3-hexanol 2.42 264 3-Nitro-4-heptanol 264 3.25 5-Nitro-4-octanol a The nitroalcohols were added as 10% aqueous solutions, t o local coagulation; if added directly, coagulation occurred. 2-Nitro-2-propanol Nitro-2-methyl-1-propanol i-Nitro-2-butanol
heat
0.10 0.10 0.08 0.12 0.12
0.08 0.08 0.10 0.12 0.08 0.10 0.08 0.12
0.07
0.17 0.12 0.12 prevent
Nitroethane was tested in a series of artificial latices and was found to be a vigorous heat-sensitizing agent for these compounds, none of which would gel without it. The results are listed in Table 111. The true rate of gelling a t elevated temperatures is somewhat faster than the tables indicate, owing to poor heat transfer through the latex. Thin layers may be gelled quickly. When a test tube full of water a t 100" C. was
1107
TABLE 11. EFFECTO F
CONCENTRATION O F 2-NITRO-2-METHYLON GELLING RATE (Formula: Lotol NC-957, 167 grams: ZnO dispersion, 4: 2-nitro-2-methyl1-propanol 88 specified) Nitroalcohola -Gelling Time, Hr.G./100 G. Dry R i b b e r 28' C. 50' C. 800 c. 0.25 0.60 1.00 2.00 3.00 4.00 5.00
PROPANOL
0
Added as a 25% aqueous solution.
OF NITROETHANE ON VARIOUSDISPERSIONS TABLE 111. EFFECT
... ... ...
200
...
...
100
... ...
... ... ...
100
...
...
...
... io6 ...4 ... ... ... ... . . . ... ... 2
0.08
1 45
1 1
1 1
...
... ...
208 10 2 6
a The zinc compounds present in the reclaims were sufficient for the test so none were added.
dipped into a sensitized latex and withdrawn after 5 minutes, its outer surface was coated with a layer of gelled rubber that was 23.8 per cent heavier than the layer deposited by a nonsensitized latex. I n another test, a 25 X 200 mm. Pyrex test tube was filled with a sensitized latex to a depth of 50 mm. and was immersed in a thermostat at 90" C. At the end of 5 minutes the latex had gelled (according to the test described a t the beginning of this paper), but the center of the mass had not yet reached 75" C. The true time of gelling a t 90" C. must therefore be appreciably less then 5 minutes.
Literature Cited (1) Commercial Solvents Corp., U. S. Patent applioation. (2) Dunlop Rubber Co., Brit. Patent 351,937 (1930). (3) Gabriel, C. L., IND.ENQ.CHBM.,32, 887 (1940). (4) Hass, H. B.,Hodge, E. B., and Vanderbilt. B. M., Ibid., 28. 339 (1936). (5) Pestalozza, U.,S. Patent 1,717,248 (1929). (6) Ibid., 1,750,540 (1930).
ROTARY BURNERIN WHICH SULFURIs BURNEDTO SULFUR DIOXIDE Courtesy,C oUulf n p a wSulphur
