INDUSTRIAL AND ENGINEERING CHEMISTRY
February 1950
~
4
The 0.8% of constituents not accounted for in the analysis is believed to consist of iodine lost during the weighing and dissolving of the sample taken for the analysis. Another run similar to the above was performed, but a large excess of iodine was used (507.6 instead of 126.9 grams). Starting with a charge of 50 grams of Altam 70%, 24.68 grams of titanium were recovered as the iodide. Thus 49.36% of the weight of Altam 70% was recovered as titanium in titanium iodide. As was shown above, the calculated percentage of free titanium in the alloy, based on analytical data, was something over 46.087o. The recovery of titanium as iodide was, therefore, in reasonable agreement with the expectation from the analysis of the alloy. It was found that 98% of the carbon disulfide was recovered during the distillation step, and 98% of the iodine used was recovered in the following: 1. The titanium tetraiodide product. 2. The aluminum salt in flask 2: by passing dry air through the red-hot molten salt, elementary iodine was released, according to the following reaction: 4KAlId 302 +4KI 2A110a 612 The recovery of potassium iodide a t this point is an asset to the economy of the process. 3. The carbon disulfide distillate: this contained about 0.02% iodine. which was serviceable in a succeeding DreDaration of titanium tetraiodide. 4. Various iodides remaining with the alloy residue: this iodine was recoverable by treatment with sulfuric acid and manganese dioxide.
+
+
+
-. .
Disonssion The method described here makes possible the preparation of anhydrous titanium tetraiodide from an inexpensive raw material, such as the alloy Altam 70%. The iodination at room temperature eliminates the inconvenience and cost of refractory reaction vessels, conduits, and gaskeb which must be used when the tetraiodide is prepared by the reaction of iodine vapor with titanium metal or alloy. When regarding the product as a source of pure titanium metal, virtually the sole raw material cost is that of the alloy, since the carbon bisulfide, iodine, and potassium iodide are all recoverable. The van Arkel-de Boer process for preparing titanium has been particularly successful in yielding metal free of the harmful gases, oxygen and nitrogen, and of carbon. However, 0.1 to 0.2% of metallic impurities were commonly found ( 4 ) . It seems likely that the present process for preparing pure titanium tetra-
2!3X
iodide will permit even purer titanium metal to be prepared by the van Arkel-de Boer process. The method for preparing titanium tetraiodide described cannot be used for preparing the analogous zirconium tetraiodide because of the relative insolubility of zirconium tetraiodide in carbon disulfide and other nonoxygenated organic solvents. The process has served as a qualitative test for elementary titanium in certain samples of metal, the components of which formed iodides soluble in carbon disulfide. The procedure consisted in refluxing the pulverized metal briefly in a solution of iodine in carbon disulfide. When titanium metal was present, it went into solution as the tetraiodide. It was subsequently identified by extraction into acidulated water and precipitating as the phosphate, or forming the colored peroxide. It is believed likely that this method is amenable to the quantitative determination of elementary titanium in metals and alloys.
Literatare Cited (1) Arkel, A. E. van, andde Boer, J. H.,
(1928).
U. 8. Patent 1,671,213
(2) Biltz, W.,and Keunecke, E., 2. anorg. u. allgem. Chem., 147, 171-87 (1925). (3) Blocher, J. M.,Jr., and Campbell, I. E., J . Am. Chem. Soc., 69,2100-1 (1947). (4) Campbell, I. E.,Jaffee, R. I., Blocher, J. M., Jr., Gurland, J., and Gonser, B. W., J . Electrochem. Soc., 93,271-85 (1948). (5) Defagqz, E.,and Copaux, H., Compt. rend., 147,65 (1908). (6) Fast, J. D., Rec. trau. chim., 58,174-80 (1939). (7) Fast, J. D., 2.anorg. u. allgem. Chem., 241,42-56 (1939). (8) Gustavson, G.,J.prakt. Chem. (2),63,112 (1901). (9) Hassel, O.,and Kringstad, H., 2. physik. Chem., B15, 274-80 (1932). (10) Hock, L., and Knauff, W., 2.anorg. u. allgem. Chem., 228,204-8 (1936). (11) Karantassis, T.,Ann. chim., 8,71-119 (1927). (12) Karantassis, T., Compt. rend., 196,1894-6 (1933). (13) Klernm, W.,and Grimrn, L., 2. anorg. u. allgem. Chem., 249, 198-208 (1941). . ~ . , (14)Ibid., pp. 209-218. (15) Klernm, W., andTilk, W., Ibid., 207,161-74 (1932). (16) Klemm, W.,Tilk, W., and Mallenheim, S. von, Ibid., 176, 1-22 (1928). (17) Mellor, J. W.,“A Comprehensive Treatise on Inorganic and Theoretical Chemistry,” Vol. VII, p. 89, New York, Longmans, Green and Co., 1930. (18) Nespital, W., 2. physik. Chem., 16B,164 (1932). (19) Pascal, P., “Trait6 de Chirnie Minbrale,” Vol. V, p. 568,Paris, Masson et Cie, 1932. RBCBIVED September 8, 1949.
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OlRGANIC COMPOUNDS OF TITANIUM Tetraalkyl Orthotitanates, New Waterproofing Agents Robert J. Speer and D. R. Carmody Texas Research Foundation, Renner, Tex.
T
HE tetraalkyl orthotitanates, which have the general
T h e alkyl titanates, derived from the action of titanium tetrachloride on alcohols, have been found to be very effective waterproofing agents. These compounds, the titanium analogs of alkyl silicates, are capable of imparting a water-repellent finish to such diverse materials as paper, cotton, wool, rayons, nylon, silk, felt, and wood. Certain potential industrial applications appear feasible.
formula Ti(OC,H2,+ were first described by Demarcay (8) in 1875. However, they received little attention until Bischoff and Adkins (I) in 1924 undertook their synthesis and a study of their properties. Even today, the published literature contains very little relative to the preparation, properties, and uses of these interesting compounds. Since 1947, a research program in this laboratory (9) has been directed toward an elucidation of the chemistry of organic compounds of titanium and a survey of their potential industrial applications.
INDUSTRIAL AND ENGINEERING CHEMISTRY
252
Unlike the corresponding alkyl esters of silicic acid, alkyl titanates cannot be formed by the simple interaction of titanium tetrachloride and an alcohol (6). Their preparation requires the action of a condensing agent such as sodium ( I ) , ammonia (6),or an organic nitrogen base ( 5 )on the mixture of reagents described above. The generalized equation for their formation may be written as: Tic14
+ 4NaOR (+ 5s. ROH)
=
Ti(OR)c
+ 4NaC1 (+ROH)
In general terms, the tetraalkyl orthotitanates may be described as high boiling, clear, viscous oils; they vary in color from water-white to light yellow, depending upon the care with which purification is accomplished. These esters are soluble in a wide variety of organic solvents such as iso-octane, isohexane, benzene, chloroform, alcohols, and ethers; however, they react rapidly with water, acetone, acetic acid, and certain esters to form white, insoluble precipitates. They tend to become extremely viscous at room temperature, and in the case of the isobutyl ester a low melting solid is formed. When pure, these products have a very mild, fruitlike odor. Probably the most characteristic property of these titanic acid esters is their ease of hydrolysis. Thus, for example, when a thin film of tetraethyl orthotitanate is spread on wood or glass in contact with moist air, it hydrolyzes rapidly to deposit a film of hydrated orthotitanic acid. Alkyl titanates have been reported to show promise in the formation of enamel-like polymers ( 8 ) , as mordants for sulfonated dyes ( 4 ) , in the preparation of white-pigmented lacquers (S), and as paint vehicles (Y). However, no mention has been found in the published literature of the application of these unique substances as water repellents and waterproofing agents. It has been the experience of-this laboratory that these products are exceptionally effective for this latter purpose. The results are still somewhat qualitative in nature; however, a more extensive and detailed investigation is planned for the near future.
Experimentrrl The tetraalkyl esters employed in this study were prepared as previously described (1, 9). These include tetraethyl, tetra-npropyl, tetra-n-butyl, tetraisobutyl, tetra-n-octyl, tetra-secbutyl, and tetra-tert-butyl orthotitanates. Qualitatively, there is little or no difference in the results achieved by these different compounds as waterproofing agents. Solvents which have been shown to be satisfactory include isohexane, iso-octane, V.M.P. naphtha, benzene, chloroform, ethyl alcohol, carbon tetrachloride, and diethyl ether. Undoubtedly many others would be equally suitable. These employed uere of commercial anhydrous quality and were purified only when known to contain water as a contaminant. The waterproofing process can be accomplished in a vaiiety of ways. These include simple immersion, immersion a t reduced or elevated pressure, brush coating, and spraying. The method of application affects the results and would doubtless h a w to be investigated in detail for each new product or process. Many different substances have been treated with these alkyl titanates. Apparently, t,he waterproofing action is virtually independent of the chemical or physical nature of the substrate treated; in general, a very effective water-repellent &ish is secured. The substances studied in this investigation include cotton, wool, silk, acetate and viscose rayons, and nylon as yarn as well as fabricated cloth; wood; certain mineral and plastic-forming powder; felt, suede, chamois, and others. No especial effort was made to optimize the treatment process for each individual material considered; hence, the techniques and results described below are primarily qualitative in nature. Water Repellent Cotton. A solution was prepared by dissolving 2.0 grams of tetraethyl orthotitanate, Ti(OC2H&, in 98.0 grams of anhydrous iso-octane. In this solution (2% by weight of active ingredient) were immersed sample test squares of air-dried, laundered white cotton cloth (ca. 4 X 4 inches).
Vol. 42, No. 2
After gentle agitation for 5 minutes at room temperature, the test squares were withdrawn from the treating bath, excesB solvent was squeezed out, and the cloth was finally air-dried for 1 hour (ca. 30” C.). Control strips of the original, untreated cotton cloth were used for comparison purposes to determine the effectiveness of water repellency thus obtained. The cloth, treated with ethyl titanate as described above, ww not altered to any appreciable extent in color, texture, and feel. However, its hydrophilic properties had undergone a marked change. This newly acquired water repellency was demonstrated qualitatively in the following manner: When control test strips of the original, untreated cotton cloth were “floated” carefully on the surface of warm, distilled water (50” C.) they became saturated and sank within 2 to 5 seconds. The treated test squares, on the other hand, remained afloat and dry for more than 24 hours. Water droplets, placed on the surface of these treated squares, did not wet the surface or penetrate into the fabric, but instead formed large, discrete, spherical drops which could be easily shaken from the surface. The stability and durability of the water-repellent finish were remarkable in themselves. Repeated washings in dry cleaners’ naphtha did not appear to have any adverse effect; the fabric was just as water resistant after these cleanings as before. Laundering in warm soap solution appeared to destroy the finish more rapidly; however, even here the desirable characteristics usually persisted for five to eight washings. Water-Repellent Wool. A treating solution was prepared by dissolving one part by weight of tetra-sec-butyl orthotitanate in 99 parts of isohexane. Small test squares (ea. 4 X 4 inches) of dry, laundered wool were placed in this solution and agitated in a closed vessel for about 15 minutes a t room temperature. An air pressure of 35 pounds per square inch was applied to the vessel to facilitate penetration of the treating solution into the wool fabric. The cloth was then removed, excess solvent wa8 squeezed out, and the test strips were air dried for 1 hour.
No visible change had occurred as a result of this treatment. As with the cotton described above, the wool retained its color, texture, and body. As before, the fabric retained its air-porosity, but it had acquired marked water-repellent characteristics. When treated test strips of this wool were placed on the surface of warm water, they remained afloat and dry for more than 48 hours. No signs of wetting or water penetration were apparent. As with the treated cotton, water droplets could be sprinkled on the surface without wetting the fabric; in fact, they would evaporate before penetration occurred. Untreated wool, on the other hand, absorbed water rapidly under the conditions of this test; it became saturated and sank within 2 to 12 seconds. Water-Repellent Felt. A 2.57, solution of tetra-n-octyl orthotitanate in V.JI.P. naphtha was employed for the processing of wool-mohair felt, although several other titanic acid esters appeared equally suitable. Several small pieces of commercial, brown, hat felt were placed in the above solution and agitated for 15 minutes in a closed vessel at room temperature. During this period, the pressure within the vessel was lowered slowly until the solvent began t o boil, then raised quickly to atmospheric. This alternate lowering and raising of pressure was repeated several times during the 15-minute interval in order to achieve better impregnation of the sample specimens. After the treatment process, air drying for 1 hour sufficed to remove the last traces of solvent. Felt treated in this manner acquired a very satisfactory water-repellent finish. When submitted to the float test described above, it resisted wetting and water penetration for several hours longer than untreated felt. I t had an additional interesting feature not exhibited by the untreated felt. Because of its water-repellent finish, the felt was not subject to water spotting. Whereas the original felt became wet and allowed its dyestuff to be leached out or “bleed,” the treated material could be sprinkled with water for over 50 hours without apparent spotting or leaching of dyestuff.
February 1950
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
Discussion
x
d
The alkyl esters of orthotitanic acid, the tetraalkyl orthotitanates, have been shown to be effective waterproofing agents for a wide variety of materials. The manner or technique of their application does not appear to be critical. Such diverse products as cotton cloth, felt, wood, and suede leather can be given a very marked water-repellent finish without change in the original physical characteristics. To account for the nonspecificity of the alkyl titanates as waterproofing agents, a hypothetical reaction mechanism has been proposed. Space does not permit an elaboration of the evidence to support this theory; however, in simplest terms one may visualize it as a hydrolysis reaction followed by dehydration. Thus, the fiber, wood, or other material treated has on its surface an adsorbed film of moisture which reacts with the watersensitive alkyl titanate to precipitate hydrated orthotitanic acid. On dehydration a t room temperature, this substance gradually changes t o various hydrated forms of titanium dioxide. It is felt that these hydrated oxides of titanium provide the ultimate water-repelling surface. However, because certain evidence has been accumulated in the course of this work which appears inexplicable in the light of such a mechanism, this postulated mechanism should be considered only as a partial explanation of the process described above. The advantages of this method of waterproofing might be itemized as follows: An effective water-repellent finish No drastic alteration in physical characteristics of substance treated-that is, color, texture, or body Unim aired air-porosity of fabrics Dry cfeaning permanence and laundering resistance Asimple method of application A list of its limitations should include: No information as to cost of materials (they are not commercially available a t present)
253
Storage difficult because of water-sensitive. nature of alkyl titanates Tendency to yellow and stiffen fabrics where additional body is not desired if applied in excessively large amounts With these relative advantages and disadvantages in mind, a number of potential industrial applications which might be feasible can be visualized: Water-repellent cotton, wool, rayon, and silk fabrics for wearing apparel Waterproof fabrics for sail cloth, tent material, awnings, and other outdoor applications Water-oil selective filter cloth or cartridges Spotproof and water-resistant felt goods such as hats, handbags, and shoes Water-repellent wood for marine and outdoor use Spotproof and water-repellent suede leather goods such as jackets and shoes Weather-resistant finish for statuarv. buildine stone. and similar materials Nonhygroscopic surface for powdered products, etc. "
I
I
All these potential uses must, of course, be predicated on the commercial availability of the titanic acid esters themselves a t a reasonable cost.
Literature Cited (1) Bischoff and Adkins, J. Am. Chem. Soc., 46,256 (1924). (2) Demarcay, Compt. rend., 80,51 (1875). (3) Gardner and Bielouss, Am. Paint and Varnish Mfrs. Assoc.,
Circ. 366,327 (1930). (4)Hancock and Stevens, J. Oil Color Chem. Assoc., 24,293(1941). (5) I. G.Farbenindustrie, A.-G., Brit. Patent 479,470(Feb. 7,1938). (6) Jennings, Wardlaw, and Way, J. Chem. SOC.,1936,637. (7) Krrtitzer, McTaggart, and Winter, Australia Degt. Munitions, Paint Notes, 2,304,348 (1947). (8) Rothrock, U. S. Patent 2,258,718(Oct. 14,1942). (9) Speer, R. J., J.Org. Chem., 14,655 (1949). RECEIVED May 16, 1949.
TITANIUM IN PORCELAIN ENAMELS G. H. Spencer-Strong and Robert F. Patrick Pemco Corporation, Baltimore, M d . *
T
HE commercial utilization of titanium, chiefly in the form of titanium dioxide, as the major opacifying agent in porcelain enamels is a comparatively recent development. This step, taking place within the last 4 or 5 years, constitutes one of the major advances in enamel technology. It makes possible the production of a porcelain enamel cover-coat or finish having extreme covering power, brilliance, and hardness together with a high degree of acid resistance. At the same time, the application weight has been reduced by almost 50%. The titaniaopacified porcelain enamels combine the more desirable properties of several enamel types. Previously, such properties were unavailable in any one material. They have, t o a large extent, eliminated the need for special types or combinations of porcelain
enamels for specific end uses. These factors have resulted in an unusually rapid acceptance of the materials by the industry and have necessitated a highly accelerated research program wherein results, previously requiring many months of investigation and study, have been demanded and obtained in days or weeks. While it was not exceptional for prior art enamels to have an active commercial life of from 5 to 10 years, the fact that the new titania-opacified enamels are often obsolete within 6 months is an indication of the rapid progress being made in this field. This development has given rise t o many problems of an unusual nature, some of which are discussed in the following pages.
Although the superior quaIities of titanium dioxide as an opacification agent have been known for many years its commercial utilization as the major opacifying agent in porcelain enamels is a comparatively recent development. This paper presents a review of the development
of titanium-opacified enamels and discusses in detail their physical properties. Probably the most interesting development in connection with these enamels is their application directly to the metal without the need for an intermediate ground-coat.
