NEW CYCLIC OLIGOMERS Metal Alkoxide Oxides Metal Acylate Oxides J. RINSE
formed by inducing maximum cyclizaT.he oligomers of metal alkoxides and acylates are the bop
subject of this article. The search for linear polymers of metal alkoxides has met with little succes, because of the tendmey of metal-oxygen chaii to form cyclic compounds. We went in another direction, and tried b d to obtain maximum cyclization by primary bonds. This has led to four new groups of compounds. The principle involved appears to be quite general-it is expected that similar oligomers can be prepared with all tri-and tetravalent metalp. The compounds of interest are completely condensed and stable oligomets. Trivaknt metalp form trimers which associate to form hexamers. Tetravalent metals form tetramerethese combine into octamcxs. Compounds containing aluminum, silicon, titanium, zirconium, and tin are reported here. A large number of thm cyclic oligomers have been prepared and shidied. They differ from compounds previously reported by containing only one alkoxy or acylate ligand bound to each metal atom. I n the remainder of this &e, such compounds will be called “condensed” oligomers to distinguish them from similar compoundswhich contain more than one alkoxide or acylate p u p p a metal atom. Because of similarity of s!ructure and preparation, silicon is included as a tetravalent metal. We difFerentiate four groups of compounds: h i m mfdom‘& alkoxides-(RO)r MIOI
himnmctnloxidColylafe~(R’C00)~ Ma01 ~~~mcfdoxidCdkoxidcs(R0)4M4’0~ fchamnnratnl oxidcaglafcs-(R’COO)4 M,‘O, The aluminum oxide acylates were developed firs, and are available commercially. Aluminum oxide stearate and the palmitate are used in preparing multipurpose lubricating greases. These compounds are A?
INDUSTRIAL AND ENGINEERING CHEMISTRY
used as Diesel lubricant additives, for binding sulfur oxides and reducing corrosion. The new compounds are all nonvolatile and soluble in hydrocarbons to form low-viscosity solutions. They have considerable surface activity, suggesting use as catalysts and wetting agents. The condensed alkoxides (with the exception of the silicon compounds) are infusible solids, hydrolyzing easily and capable of binding acids. The condensed acylates and silicon oxide alkoxides are more stable to heat and hydrolysis. They are liquids or meltable solids. Possible uses of specific compounds are listed later in this artide. In most cases, only enough exploratory work has been done to establish that the compound has the desired functional properties. Optimum formulations have not been developed, and details of the experiments have not been published. With so many compounds to investigate, we were forced to choose between screening many uses, or developing only a few. Molecular Shudunr
I t is believed that primary bonds are formed in the cyclic trimer and tetramer. Coordination bonding is not considered to be prevailing. The molecules can be shown as drawn in the title, above. Figures 1-5 show the most probable structures of these compounds. I t is proposed that the basic arrangement of the atoms in the double trimer (hexamer) is a core composed of a n octahedron of six close-packed oxygen atoms, bound together by six trivalent metal atoms Figures 1 and 2. The six organic radicals are bound to themetalatoms, andarelocatedat theoutsideofthiscore. The core of the tetramer is again an octahedron of six oxygen atoms, bound by four tetravalent metal atoms in the shape of a tetrahedron. The four organic ligands
.
@ e
e .e
are attached one to each metal atom, and are at the outside of this core. Figure 3 shows this shape, with distances between atoms exaggerated. When two tetramer units combine to form the octamer the structure may be a cube of eight metal atomsone on each corner. Twelve oxygen atoms closepacked in three layers of four atoms would have their centers in a cube slightly smaller (or larger) than the cube of the metal atoms. Such a configuration is shown in Figure 4. It can be seen that each metal atom is adjacent to three oxygen atoms. The molecule is completed by adding one alkoxide or acylate group to each of the metal atoms. Again, these ligands are a t the outside of the central metal-oxygen core. Background Information
A rather extensive literature exists in the field of metal alkoxides. I n particular, Wardlaw, Bradley, and collaborators (77-73, 45), have described the preparation and properties of such compounds. Anderson gave chemical and economic surveys (3, 4 ) . Blumenthal has supplied data about the chemistry of organic zirconium compounds and their possible structures (9, 70). The literature regarding siloxanes is abundant and can best be consulted through recent monographs (7, 7, 79) When structures are discussed, several authors give considerable consideration to the coordination numbers of the metals, in particular of aluminum, titanium, and zirconium. The number of molecules associated to form so-called polymers by secondary bonds has been determined by molecular weight determinations. For example, degree of association of aluminum isopropoxide has been found to be three or four (24). Preparation of linear polymers by controlled hydrolysis has been investigated for alcoholic solutions of alkoxides of silicon, titanium, zirconium, tin, and other metals. The reactions of these alkoxides with organic acids have also been studied, and the existence of some oligomers has been mentioned. The resulting compounds were frequently undefined mixtures with low stability to moisture and heat. Metal-oxygen chains with more than three or four metal atoms prefer cyclization rather than linear polymerization. Higher temperatures and the presence of solvents favor cyclization, while lower temperatures and higher concentration favor the formation of linear polymers. Preparation of linear as well as cyclic compounds has been successful only in the case of the siloxanes containing alkyl or aryl groups. The cyclic siloxanes (77) are trimers and tetramers with two ligands per silicon atom or with alkyl groups (8, 42, 46) as shown below. A cyclic zirconium oxide tetramer is also known (9, 70). I
RO
I
OR
I
RO- Si- 0 - Si- RO I I
0
I
0
I
RO, ,OR o'si\o RO\ I ,Si, RO
I
/OR
,Si 0 'OR
RO-Si -0 -Si -RO
I RO
I
OR
We succeeded in replacing two alkoxy groups from a simple trivalent metal alkoxide with bonds to oxygen, 44
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
Figure 5. The metal-oxjgen core of the hexamer &#ped of its organic groubs is shown on the left. Six trivalent metal atoms bind si* oxygen atoms in this compact form. A t the right. four tetravalent metal atoms andsix oxygen atomsform the core of the tetramer
by adding the calculated quantity of water and condensing the intermediate hydrolysis product to form cyclic oligomers. The first products of this work \\-ere cyclic trimers of aluminum oxide acylates (30, 38). For tetravalent metals, it has recently been found that by similar methods, the number of organic groups attached to the metal atom could be reduced to one. The result is a tightly bound group of four metal and six oxygen atoms as the center of the tetramer with four alkoxide or acylate groups at the outside. Preparation
Preparation of Simple Metal Alkoxides. General procedures for preparing the monomers are well known and fully described elsewhere. T o summarize, metal chlorides of tri- and tetravalent metals react easily with alcohols forming metal alkoxides and hydrochloric acid. The acid is neutralized at low temperature (30" C.) to prevent reaction with the alkyl group of the alcohol. This is done with ammonia or with amines (in particular triethylamine), and the precipitated salt is concentrated by distillation. Conversion is practically quantitative and yields are high (95-100%). Sometimes variations of this method are needed-these \-ariations will be discussed later in the article. Preparation of the Condensed Alkoxides. A solution of the metal alkoxide in a hydrocarbon or an alcohol is mixed with water in the molar ratio of 1 : 1 for the trivalent metals and 1 : 1.5 for the tretravalent metals. It is necessary to avoid local excess of water, because this would cause complete, irreversible hydrolysis of part of the alkoxide. Thewfore a diluent (ethanol, isopropanol, or butanol) is used for the water, and the batch is agitated vigorously during the addition. The solvent and the alcohol liberated by the reaction are removed by distillation. At the same time, the condensation proceeds until no more hydroxyl groups remain. Prolonged heating at 130-150' C. is required. No catalyst is needed except in the case of silicon where a small amount of acid is used. Preparation of the Condensed Acylates. The condensed alkoxide oligomer is transformed into an
acylate with similar structure by the addition of one mole of monobasic organic acid per metal atom. Alcohol is removed by distillation. A suitable solvent (usually xylene) is required to complete the reaction. This method does not apply in the case of silicon. Here the acid anhydrides must be used instead of the acids, since acids depolymerize the siloxane, yielding insoluble products. I n some cases it is possible to prepare the acylate directly from the monomeric alkoxide by adding water and acid together. The reactions are represented by the following equations : M(OR)3
1
acid
(OMOR)3 (OMOOCR’)3 HzO
ROH
M’Clr
-
HzO
ROH
MC13 ----+
M’(0R)h
acid
A
(R0)qMq’OB ___t (R ’COO)4M4’0s
Polycondensation. The formation of the metal oxygen-metal (MOM) group proceeds by one of the following reactions : -MOR -MOH -MOR -MOR
+ HOM+ HOM+ ROM-
+ R’COOM-
2 (-MOR)
+ --+
-+
-MOM-MOM-MOM-
+ -MOM-
+ R’COOR
---f
+ R O H (a) + HzO ( b ) + R O R (c) + R’COOR
-MOMOOCR’
+ ROR
(d) (e)
For most of the metals, Reaction ( a ) dominates, though there are indications that with zirconium and tin, Reaction ( b ) also participates. It is generally accepted that for silicon, a t least a t lower temperatures, Reaction ( b ) proceeds. T h e liberated water then hydrolyzes another SiOR group to SiOH; which reacts again with another similar group, liberating water and alcohol. This is repeated until all O H has disappeared. T o complete this reaction, alcohol must be removed above 100’ C. using vacuum. It is probable that at such temperatures the condensation in its last phase proceeds by Reaction ( a ) . Polycondensation by Reaction (c) requires temperatures of 150-250’ C. and is often accompanied by such side reactions as decomposition of alkoxy group or oxidation, yielding impure end products. Reaction ( d ) is of practical interest because no water is needed. For this purpose one mole of acid is added to the trivalent metal alkoxide (such as aluminum isopropoxide) liberating one mole of alcohol, which is removed by distillation. Ester formation and polycon-
J . Rinse is a Consulting Chemist, Chemical Research Associates, Bernardsville, N . J . T h e following chemists AUTHOR
have partic$ated in the experimental part of this paper: F. H. Arendell, J . ten Broeke, C. Buizert, A . J . Dontje, H. Jonge Poerink, S. K . L i m , T . Morel, J . F. van Peppen, P. Voorthuyzen, A . M . Ztzrella.
densation take place simultaneously. Then, upon addition of a second mole of acid and heating at 200’ C., the polycondensation is completed with formation of a total of one mole of ester per aluminum atom (37). This reaction is only partially successful for tetravalent metal alcoholates because intermolecular condensation proceeds as well as the intramolecular condensation. Apparently the acylate group is more strongly bound than the hydroxyl group, requiring higher temperatures with increased chance for crosslinking of oligomers. T h e type of condensation represented by Reaction (d) has also been used to prepare siloxanes by adding acetic acid to ethyl silicate (25). The reaction between a n ester and a metal alkoxide, Reaction (e), needs a temperature of 250’ C. and is accompanied by side reactions, such as formation of unsaturated hydrocarbons, which make it difficult to obtain pure oligomers of the desired type. The practical reactions leading to the formation of tetrameric metal oxide alkoxides are of the types ( a ) and ( b ) . Both equations can be either inter- or intramolecular. After linear tetramers have been formed by intermolecular condensation, further reaction should proceed intramolecularly; therefore reaction conditions which promote this should be chosen. I n general, this means a relatively low concentration of the oligomers in a suitable solvent. If ( b ) is the leading reaction, the solvent (e.g., alcohols) should be able to retain water because water is needed to complete the hydrolysis of partly reacted molecules. If Reaction ( a ) dominates, solvents such as xylene can be used. Temperatures over 100’ C. are needed for intramolecular reactions, while intermolecular Reaction ( b ) frequently proceeds at room temperature, causing gel formation which is irreversible. For example, partly condensed silicon oxide ethoxides and butoxides will react in this way. I n the presence of acylate groups, when acid and water have been added in a common solvent, the cyclization reaction and final intramolecular condensation need more time for completion than is the case for tetrameric alkoxides. During this phase, too high temperatures (150’ C. and higher) should be avoided to prevent intermolecular Reaction (d) . High boiling solvents (such as mineral spirits) can be helpful in speeding up final internal condensation. Support for the Proposed Molecular Structures
The structures depicted in Figures 1-5 are supported by qualitative infrared spectroscopy, molecular weight determinations, consideration of physical and chemical properties, and by analogy with proved structures of similar compounds. Final proof of the structural model must await quantitative infrared measurements. I n addition, the course of the reaction has been followed by determination of ester a t each step during the preparation of the aluminum oxide stearate. The material balances so obtained are in agreement only with the cyclic trimer concept, not with a cyclic hexamer. Infrared Spectroscopy. Qualitative studies of condensed aluminum oxide stearate, silicon oxide butoxide, VOL. 5 6
NO. 5
MAY 1964
45
m d titanium w i d e Stearate yield spectra that are csnsistent with the assumed structures. Although molecular weights indicate that six MqOOCR') units make up the d e d e , a cydic hexamer is ruled out by the spectra. A double trimer is t h d o r e indicated. 1 Mole& Weigh-. The molecular weights of gyqal of the compounds have been determined by dqmsion of the melting point of naphthalene. For %his purpose 100 gramnof naphthalene was uacd for each dctamination with 1-5 g m m s of the metal compound. This mcthod dowx heating of the solution to higher tcmpaatures (such as 150' C.) immediately before the solidification point d e t h t i o n . The followingvalues have been observed : M a m Wm@
w AIIlminvmoxidc~ h p m p y h t e 1:1n-te 1:F SS&loride*bXiClC
?ntimmmmddcstcarate
921 (for*a) 1228' 614' 1220 (for octamer) 1344 (for teeamex)
06nrOrd
1800 1190 619 1060 1350
Prop&ies. Physical and c h e m b l properties of the compounds are in agreement with the structures assumed. The specific gravities are high (Table I), indicating close-packing, and the solubility in hydrocarbons and alcohols is excellent, because of relatively low molecular weight and absence of hydrogen bonding. TABLE I-SPECIFIC
GRAVJTIES OF METAL
omnE OT~ARATES
Aluminum oxide stearate Aluminum stearate Titanium oxide & r a t e Titanium distearatc Zirmnium oxide stearate Zirconium diatearate Tin oxide stearate
i.055 1.01 1.12 1.045 1.264 1.125 1.21bcdshlymndc 1 .M .Ra 24 hours 0.99"' '' . ,:
I
Stannowstcarate
~
,
..
,
Stability to hydrolysis of the condensed acylates is excellent, except for the case of silicon oxide acylates. The condensed &oxides hydrolyze more slowly than the simple metal alkoxides. The high specific gravity and stability to hydrolysis must be attributed to a decrease in distance between the atoms. For phosphorus pentoxide, it has been found (47) that the 0s distance in the P.0, center 4shortened by 10%. 'This means that the atomic radius of the oxygen atoms was depressed from 1.40 (ionic radius) to 1.26.. Similar decreaPes must be expected for ,@e oxygen itom of the o l i i e n . of hi- and tetravalent metals. Because the ionic character of the metal-oxygen b n d s is larger than .that of the P-0 bonds, it is expected that the depression of the atomic radius of the oxygen atoms will also b i a r g e r . Aluminum Duivdlwr
/
\
RO OR purified by vacoum distillation. I n Europe the butoxide is also used industrially. AIP is made from aluminum metal by means of an autocatalytic reaction: AI
+ 3 ROH -+ Al(0R)z + 3 H+
Anhydrous isopropanol is used and mercuric chloride 88 the catalyst. AIP itself can also act as a startcr for the reaction. After this reaction is camed out in a batch p'occss (41) the crude product is heated at 150' C. and distilled
w iudine is added
1
.
This new compound, a polymer of aluminum oxide acylate (R’COOAlO), is stable, easily soluble in alcohols and hydrocarbons and reacts with acids a t room temperatures, with water on slight heating (38).
AI (OR)3 ALUMINUM TRldlKQXlDE
Hz
QDCR’
(OAlOOCR’), 4- n HzO + n (HO)z A 1 0 0 C R ’ (OAlOOCR’),
k ROH UM TRlACYlATE
i.
Figure 6. Ternary diagram for aluminum compounds. Key, 7-aluminum trialkoxide; 2-aluminum monoacylate dialkoxide; 3-aluminum diacylate monoalkoxide; 4-aluminum triacylate; 5-aluminum monohydroxide monoacylate monoalkoxide; 6-aluminum dihydroxide monoacy late ; 7-aluminum monohydroxide diacylate
Molecular weight determinations indicate that n equals six. I n presence of ester, lower values are found (see page 46), indicating that the pure compound is an association of two trimers. The acid addition opens the possibility of preparing complex aluminum soaps, e.g., the benzoate-stearate or the lactate-oleate. These soaps can be prepared in the medium in which they have to be used, for example in a mineral oil medium. I t is possible to prepare the trimers without water by using an extra molecule of acid (37, 43). The resulting product is a solution of the trimer in isopropyl ester (e.g., stearate or oleate) at about 50y0concentration. 3 Al(OR)a
under vacuum. A clear, water-white liquid is recovered, which after several days converts into a more stable solid form with melting point of 118” C. The liquid consists of trimeric associated molecules and the solid is made u p of units of four molecules (24). AIP is soluble in alcohols and in hydrocarbons including mineral oils. I t reacts rapidly with water and with acids, releasing isopropanol. Aluminum Soaps. The relation between simple aluminum alkoxides and acylates, and aluminum hydroxide is given in the ternary diagram, Figure 6. In the following, only compounds made from alkoxides with 2-5 carbon atoms and acylates with 10 or more carbon atoms (frequently called soaps) will be discussed. The industrially made aluminum soaps are indicated by Points 6 and 7 on the base line. The existence of trisoaps (Point 4) has been questioned (2), but recently they have been made via AIP (23, 3 7 ) . If AIP is added to fatty acid and the mixture is heated above the boiling point of isopropanol (82’ C.), allowing all alcohol to escape rapidly, the resulting product is a trisoap. Its properties, easy solubility, and heat stability had been predicted by McGee (22). Small amounts of water hydrolyze trisoaps to the disoaps -solids which swell in hydrocarbons. Only the trioleate and linoleate are viscous liquids (37). The other trisoaps are solids. The center of the diagram suggests that a compound should exist with three different groups on the aluminuni atom. Such a compound (Point 5 ) can be produced either by adding water to the dialkoxy soap or by adding a mixture of fatty acid and water to AIP (36). I t can be converted into the regular hydroxy soaps by adding water or acid (32). Condensed Aluminum Oxide Acylates. The new product represented by Point 5 appeared to release another molecule of alcohol when it was heated above 100” C. and all of the alcohol distilled off under vacuum.
+ n HOOCR’ + n HOAl(00CR’)z
+ 6 HOOCR’+(OAlOOCR’)3
f
3 ROOCR’
+ 6 ROH
Applications of Aluminum Oxide Acylates. T h e condensed acylates are now in commercial use in two products : -All purpose lubricating greases. By dissolving 6-970 of the condensed aluminum oxide stearate or palmitate in mineral oil and reacting with 2-370 benzoic acid, greases are made with dropping points of 500’ F. and high stability toward water and mechanical action (27). -Additives for lubricants for Diesel engines. Aluminum oxide stearate binds sulfur oxides, thereby reducing corrosion (26).
Based upon the capacity to bind water as well as acids and upon surface-active properties, several other applications have been developed or are visualized : -Gelling agents. These compounds are used with alkyd resins to prepare truly thixotropic paints which dry through without wrinkling (20, 28, 33, 35, 44). Napalm is produced by simple mixing of two liquid components (naphthenic acid and trimer oleate in gasoline). They are thickening agents for cosmetic and pharmaceutical oils. -Surface coatings. Coating for pigments reduces hydrophilic nature and improues wetting by organic birrah. A s a water-proojng agent for textiles, low viscosity solutions of the condensed stearate penetrate betweeax fhe,bbers and react with available water. -Binders and resins. Acylates can be used as resins in core binders for .rand (hardening during storage or by slight heating), additiues to pitches used for ,floor tiles, and for linoleum from tall oil ( 5 ) . They also form resinsfor nitro-cellulose lucquers. -Ability to bind azid, as in pharmaceutical uses (34). -Ability to bind water, as in spray for rapid drying of printing inks and in rubber mixtures. --Mod$ers of rheological properties. T f q can act as agents for the prevention of alligatoring of asphalt, modijers of waxes and modijers for rubher mixtures. as in lubricating oil detergents (aluminum oxide -Emulsijers, sulfonates).
Condensed Aluminum Oxide Alkoxides. The reaction between AIP and water can be directed in such a VOL. 5 6
NO. 5
MAY 1964
47
per aluminum atom have been replaced by 1 oxygen atom (38).
3 AI(0R)r
+ 3 HxO
--t
(OAIOR),
during storage. Completely condensed siloxane has bxn stored for over three years without viscosity increak.
+ 6 ROH
This solid, infusible, but hydrocarbon-soluble product wWstiD teact with water and with acids. l t k a Saong ,acid bier, binding t w molecules ~ of acid to form .the Mvlate. l I t reacts with ,tau oil,,fatty acids and , a c e ~ c y l i i cacid at room temperature. n;js. ma& it Suitable for reducing ,the acid number @ oils of aluminum pitches and for the p di$&+g ,aF% , . vkt,ei*,I t Cfm alw be @ceit releases lqs alcohol than the s i m p l e , W + . t :T)iEarboxylic anhydricka .we hound -gh an' addi-
si- 0 - si
~*
I\ /I 00 00 I/ \I
car-
. tion reaction:
(0XtoR)i ....
QR):
+ 3 CaHa(C0)rO + (OAIOOGH4COOR)r
+ 3 C+MCO),O
-
(OAIOOCH4HCOOR)r Phthalate and malate adducts,.made in thb manfrom 60% .ph+alic anhydride or 49% maleic anh-de, are dear rea+ of good color which are soluble inuomahc hyslmcadwnr;and.almhols.aeasrr,cQgupatiblewithdt&dlulose.. lfthisreacrioaisruniamer solvent, -suchas styrene or vinyl acetate, pplymgiption af &Ivent is initiated, fprming cqplymer?. .
%*
.
pure acylates. . In addition, combireti& of more rings can be +de by condensing two 6f the mixed trimer molecules above 200' C. hvo or
4 l
Mt5YSTIIAL A N 0 ENGINSERING CHEMISTRY
si-0-si
organic r i d per Si atom. Some tetram~may be present. We have OM that when the ratio is 1 $0 r/'l the fonnafion of the w n d d tetrama is
favored,apparendybythemactionbelewwhkh~ ? with release of alcohol (39). (RO),Si-O-Si(RO),
I
I
ROS-O--BiOR
+
2Hao
--c
I\
/I
I/
\I
000 0
ROSi-0-SiOR
I
Siloxanes can also be made by adding acetic acid to ethyl silicate and removal of ethyl acetate (25). Properties. The condensed siloxanes, (RO),Si,O,, are solids or liquids, as soluble in hydrocarbons as in alcohols. The specific gravities of some of the compounds are:
Siloxane Ethoxy Isopropoxy Butoxy tert-Butoxy Allyloxy Cresyloxy Hexyloxy
1
Specific Gravity, 20°C. 1.305 1.246 1.146 1.19 1.23 1.22 1.07
1
1
State Qt2O0C. Solid Solid Liquid Solid Liquid Solid Liquid
All compounds are nonvolatile and nondistillable. They do not crystallize. Temperature stability above 200" C. can be increased by benzyl alcohol and by antioxidants. Hydrolytic stability is fair, and varies with size and type of alkoxy (or phenoxy) group. Titanium alkoxides promote hydrolysis by humid air. Metal oxides react with several of the tetramers to form metal silicates. Silicon oxide acetate and isopropoxide are solids, soluble in toluene. They hydrolyze rapidly when exposed to moisture. Applications of Condensed Siloxanes. Because of ease of preparation and low material cost, the new siloxanes may be of interest. They can form binders for heat resistant paints in combination with such metal powders as aluminum and copper bronzes. The coatings are air-drying and resist the heat of a Bunsen burner indefinitely without cracking or flaking. Apparently a coating of metal silicate is formed. Phenoxysiloxanes can be used as binders for colored and nearly white pigments. Other possible uses are as modifying agents for alkyd resins, hydraulic liquids, core binders, temperature resistant greases, and so forth. These siloxanes may be considered as the poor man's silicones. Titanium Derivatives
The simple alkoxide, titanium tetraisopropoxide (TPT), is manufactured commercially from titanium tetrachloride, and is used for metal treatment, as an ester exchange catalyst, in heat resistant paints, and so forth. Several polymeric titanium compounds with two organic ligands per titanium atom have been described as dispersion agents (78, 21). The condensed alkoxides can be easily prepared by addition of an alcoholic solution of 1.5 moles of water to 1 mole of TPT dissolved in alcohol, followed by addition of xylene and heating to 140" C. As in the other compounds described, the resulting oligomer has one (R0)-ligand per metal atom. The oligomer is a crystalline solid, soluble in aromatic hydrocarbons. It hydrolyzes slowly when exposed to humid air. I t forms a
clear coating, which gradually cracks and becomes a white powder. When the isopropoxy group is replaced by the hexyloxy group or the cyclohexyloxy group the hydrolysis is much slower. The phenoxy compounds are strongly colored. As described for other compounds, organic acids convert the condensed titanium alkoxides into the corresponding acylates and by-product alcohol. The latter is removed by distillation. The condensed titanium acylates are solids with the exception of the oleate and linoleate. The stearate melts at 40" C., and is soluble in aliphatic hydrocarbons. The octanoate is infusible and dissolves in aromatic hydrocarbons. The dodecylbenzenesulfonate is soluble in mineral oils ( 3 9 ) . The condensed acylates are very stable products, which are not hydrolyzed by moist air or by water. The stearate and octanoate, when applied on paper or on cotton, exercise a strong water repellancy. Dilute solutions of 1/4-1/2% in hexane make filter paper water repellant ; leather requires higher concentrations. They may be used as dispersion agents for pigments. The sulfonates are lubricating oil detergents ; they cause mineral oil to wet surfaces better and are capable of emulsifying water into oil. Titanium oxide lactate is a strong acid, indicating that the lactic acid has combined with titanium via the hydroxyl group. Its p H in a 10% aqueous solution is 2, and it is highly soluble in water. Upon addition of alkali, the solution becomes milky and finally gels. The compound reacts with polyvinyl alcohol, insolubilizing this binder in a coating or in a filament spun from polyvinyl alcohol. Probably the Ti compound reacts with the hydroxyl groups, forming large crosslinked polymers. Titanium oxide phthalate and oxide malenate have been made in a way similar to that used for the aluminum resins. They are soluble resin-like materials with a phthalic content of 53%, maleic content of 43%. Zirconium Derivatives
Starting with ZrC14, the simple tetralkoxides are easily made and converted into the condensed form by adding the required amount of water and heating to 140' C. in xylene solution. The condensed materials are solids, soluble in aromatic hydrocarbons. They hydrolyze in contact with water vapor. The condensed acylates are made in a way similar to the preparation of titanium oxide acylates-by adding acid to a solution of the condensed zirconium alkoxide and then removing the liberated alcohol. Alternatively a solution of water and acid can be added to a solution of the alkoxide (39). The acylates are solids which are soluble in hydrocarbons, and which do not hydrolyze. Zirconium oxide octanoate is an effective dryer for linseed oil and alkyd resins if it is combined with a very small quantity of cobalt dryer. This combination acts quickly without discoloration or wrinkling of the coating. The stearate and octanoate have waterproofing properties, and the sulfonates are oil-soluble detergents. VOL. 5 6
NO. 5
M A Y 1964
49
Tin Derivatives
Stannic chloride is converted into the simple tin(1V) alkoxides, and then to the condensed form by the methods described earlier. These are again water sensitive compounds, and they also react with acids to form acylates. The condensed compounds have a darker color than the titanium and zirconium compounds, and a higher specific gravity ( 3 9 ) . Several of the condensed tin compounds have catalytic activity, in particular as dryers for oils and alkyd resins (and very likely in urethane reactions). Their tin contents are higher than those of other tin compounds; for example, the octanoate has a tin content of 417, against 29y0 for the commercially used stannousoctanate. There is also evidence of fungicide activity.
Metal Oxide Butoxide Cost of metal chloride, cents/lb.
a
Cost of metal, cents per lb. product
89
5.8
20.5
Cost of butanol, cents per lb. product
10.9
10.0
8.7
6.6
5.8
Total raw material cost, cents/lb.
16.7
30.5
46.7
53.5
113.2
23.2
56.6
14.0
13.0
37.3
69.6
Cost of metal, cents per lb. product
’ ~
Cost of fatty acid, cents per lb. product Total raw material cents/lb.
1 I
COST,
Formation of Bimetallic Compounds
Tetrameric metal oxide derivatives may condense to larger molecules, as indicated in the discussion of aluminum and silicon. The melting point of the stearates, (usually around 50” C.) rises quickly with degree of condensation, while solubility decreases. Naturally, the size and nature of the ligand play a large part in determining the solubility. By condensing oligomers of two different elementse.g., aluminum oxide stearate and silicon oxide butoxide, bimetallic oligomers can be formed. In this case the products are aluminum silicates, soluble in organic liquids, with butyl stearate as a by-product. If the reaction proceeds in mineral oil, greases are obtained, which have no dropping points. Soluble silicates of titanium, zirconium, and tin have been made in a similar way. I n addition to the listed metals, it is expected that other tetra1Talent metals, in particular lead, germanium, cerium, thorium, and uranium will form tetramers of the same structure.
15
!
2.2
1
17.2 19.4
107.4
16.8
’
15.6
I
, 32.4
~
LITERATURE CITED (11 Abbort, A. D., e t a l . , J.Chem. En?.Dafo 6 , 437 (1961). (2) Alexander, A. E., J. Oi! Colour Chemists Assoc. 37, 378 (1954). (3) .4nderson, A. R., Chem. Week, Sept. 17, 1960. ( 4 ) Anderson L\ R . Thomas I. M . “Metal Alkoxides,” in Kirk-Othmer Encyelopedia of Chkmkal’Technoldgy, Zn6 Ed., Vol. 1, p. 832, Interscience, N.Y., 1963. (5) Ayers, J. W., U. S. Patent 2,936,243 and 2,936,244 (May 10, 1960). (6) Balthis, I. H. (to du Pont Co.), U. S. Patent 2,621,194 (Dec. 9, 1 9 5 2 ) . ( 7 ) Balthis, J. H., U. S . Patent 2,681,922 (June 22, 1754). (8) Barry, A. J. Gilkey, J. W. (to Dow Corning Co.), U. S. Patent 2,465,188 (March 27, l j 4 8 ) . (9) Blumenthal? W. B., “The Chemical Behavior of Zirconium,” Van Nostrand, Princeton, N. J., 1958. (10) Blumenthal, W. B., IXD.ENC.CHEM.55, 4, 50 (1963). (11) Bradley, D. C., “Metal Alkoxides,” Aduan. C h e m , S e r . 23, Sept. 1959. (12) Bradley, D. C., Can. J . Cizem. 39, 1434 and 1818 (1961), 40, 15, 62, and 117G (1 962). (13) Bradley, D . C., in Cotton, “Progress in Inorganic Chemistry,” Vol. 2, 303, Interscience, N. Y.,1960. (14) Bradley, D. C., Prevedorou-Demas, C., Can. J . Chem. 41, 629 (1963). (15) Decker, H. C. J. de, “Phosphorpentoxide,” Diss. Amsterdam, 1941, (16) Decker, H. C. J. de, MacGillavry, C. H., R e r . Trov. Chim. 60,153 (1941). (17) Eaborn, C., “Organosilicon Compounds,” Academic, N. Y.,1960. (18) Haslam, J. H. (to d u Pont Co.), U. S. Parent 2,621,195 (Dec. 9, 1952). (19) Hunyar, A,, “Chemie der Silikone,” 2nd Ed., VEB Verlag Technik, Berlin, 1959. (20) Korf, Chr., Verfkroniek 28, 137 (1955). (21) Langerkammer, C. M. (to du Porit Co.), U. S. Patent 2,621,193 (June 27, 1950).
Economics
Because the conversion of metal chlorides into alkoxides and the consecutive hydrolysis and soap formation reactions proceed nearly quantitatively, the raw material costs of condensed products can be calculated as shown in the table. Cost data are taken from Chemical and Engineering ,Yews,Octobcr 28. 1963. The cost of ammonia required to neutralize liberated hydrochloric acid is not taken into account because it can be compensated by the yield of ammonium chloride. Technical stearic acid of 20 cents per lb. contains palmitic acid. The molecular weight of the mixture is taken at 165. Less costly saturated fatty acids are sometimes available. The price of butanol is taken at 17 cents per lb. Not all alcohol and solvent are recoverable because of small losses during distillation. Accordingly, 1-2 cents per lb. must be added. Production costs are estimated at 5-25 cents per Ib. depending upon size of batch and costs of labor and heat. 50
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
(22) MeGee, C. G., J . Am. Chem. Sot. 71, 278 (1949). (23) Mehrotra, R. C., Pande, K. G., J . Inorg. Nuc!. Chem. 2, 60 (1956). (24) Mehrotra, R . C., J.Indian Chem. SOC.31, 25 (1954). (25) Olson, M. M., Christenson, R. M., U. S. Patent 2,848,425 (Aug. 19, 1958) and U. S . Patent 2,917,467 (Dec. 1 5 , 1959). (26) Pethrick, S. R., Welch, T h . R. (to British Petr. Co.), U. S. Patent 9,089,853 (May 1963). ( 2 7 ) Polishuk, A. T., Lubr. Eng. 19, 76 (1963). (28) Rinse, J., Paint Varnish Prod., July 1958. (29) Rinse, J., A m . Paini J., Apr. 23, 1956. (30) Ibid., May 4, 1959. (31) Rinse, J., U. S . Patent 2,835,685 (May 20, 1958). (32) Ibid., 2,852,411 (Sept. 16, 1958). (33) Ibid., 2,892,780 (June 30, 1959). (34) Ibid., 2,910,493 and 2,910,494 (Oct. 27, 1959). (35) Ibid.,2,911,316 (Nov. 3, 1959). ( 3 G ) Zbid., 2,913,468 (Nov. 17, 1959). (37) Ibid., 2,948,743 (.4ug. 9, 1960). (38) Ibid.,2,979,497 (Apr. 11, 1961) and 3,054,816 (Sept. 18, 1962). (39) Zbid.,3,087,949 (.4pr. 3C, 1955). (40) Sehechter, W. H. (to Callery Chem. Co.), Ibid,, 2,891,086 (June 16 1959). (41) Smith W. E., .4nderson, A. R., (to Anderson Chem. Co.), Ibid., 2,965,663 (Dec. 1960). (42) Sprung, 14. M., Guenther, F. O., J . A m . Chem. SOC.77, 3990 (1955). (43) Theobald, C1. W. (to du Pont Co.), U. S. Patent 2,744,074 (May 1, 1956). (44) Turner, J. H. W., Kemp, S. G., Harson, S. E., J,Oil Coiour Chemists Assoc. 41, 769 (1958). (45) Wardlaw, I+ J .‘Chem. ., SOL.3569 ( l o s s ) , 4004 (1956). (46) Wiberg, E., Simmler, W., Z . Anorg. A!lgem. Chem. 282, 330 (1955). (47) Zijp, D. H., “Vibrational Spectrum and Analvsis of XiYeZa Molecules,” Diss. Amsterdam, 1960.
