Fused Zinc Resinates from Aldehvde-Modified Rosin J
WILLIAM E. ST. CLAIR AND RAY V. LAWRENCE Bureau of Agricultural and IndustrMl Chemistry, U. S . Department of Agriculture, Olustee, FIa.
T
HE production of zinc resinates is an important process in the preparation of resins for the surface coatings industry. Large quantities of zinc resinates go into the manufacture of paints, varnishes, and printing inks. Fused zinc resinates are excellent varnish materials, but when rosin is fused with a reactive zinc compound, such as zinc oxide, the zinc resinate formed frequently "blocks" (@-that is, i t sets up into a semicrystalline, infusible mass. Numerous attempts to prepare neutral fused zinc resinates from untreated rosin have been unsuccessful, since these fused zinc resinates frequently block when only a fraction of the stoichiometric quantity of zinc has reacted with the rosin. While blocking of untreated rosin can usually be circumvented in the laboratory, it is not practical to do so industrially. Palmer and Edelstein (6)prepared fused zinc resinates of high zinc content from a partially polymerized rosin. They found that if the rosin contained a sufficient amount of rosin polymer and a small amount of acetic acid, no difficulty was experienced with blocking. The present paper describes a simple method of preparing neutral, fused zinc resinates. Since fundamental investigations conducted in this laboratory on the reactions of resin acids with aldehydes gave products which formed crystalline derivatives only with extreme difficulty, it seemed likely that an aldehyde-modified rosin would be a good starting material for the preparation of noncrystalline fused metal resinates (6). As neutral, fused zinc resinates are quite difficult to prepare the fused zinc derivatives of the aldehydemodified rosins were investigated first. There are numerous patents on the hardening of rosin with formaldehyde under pressure and in the presence of acetic acid (1, 3, 4 ) , but these formaldehyde-modified rosins are incompletely soluble in the common varnish solvents, such as turpentine and mineral spirits. In contrast, the resinous zinc salts of formaldehyde-modified rosins are completely soluble in the common varnish solvents and are satisfactory for use in surface coatings. When unmodified rosin is reacted with zinc oxide the reaction probably proceeds in the expected manner with the formation of a zinc diabietate. If suitable amounts of acetic acid are incorporated into the reaction mass or if zinc acetate is used, the formation of a zinc acetate-abietate probably occurs. The formation of this zinc acetate-abietate is probably the explanation for the high zinc contents of certain fused zinc resinates prepared from heat treated or polymerized rosin (2). When suitable zinc compounds are reacted with an aldehydemodified rosin they apparently react with the carboxyl groups in the expected manner. But when such rosin derivatives as methyl abietate, ester gum, decarboxylated rosin, and rosin oil, which have acid numbers of less than 20 are modified by aldehydes and then zinc acetate reacted with this product, greater amounts of zinc can be caused to combine than can be accounted for either by the formation of a zinc diabietate or a zinc acetate-abietate. A wide variety of zinc compounds was used in the preparation of these fused zinc resinates from rosins which had been modified with an aldehyde. Satisfactory zinc resinates were prepared using zinc oxide, zinc-dust, zinc carbonate, zinc hydroxide, and several sin6 salts of volatile organic acids. In contrast to the
excessive arnounts of zinc acetate which react with the low acid number aldehydemodified rosin derivatives only that amount of zinc oxide required to neutralize the carboxyl groups present appears to react. PROCEDURE
In general, the preferred procedure was as follows: The rosin or the rosin derivative and the particular aldehyde were mixed together and the temperature raised to 230" C. over a period of about 1 hour without agitation, The agitation was then commenced and zinc oxide was added slowly while raising the temperature to 250" t o 2'75" C. Sufficient time wm allowed for the added zinc oxide to react and then another portion of zinc oxide w a gdded. When the starting material was a low acid number rosin derivative, the aldehyde and the rosin derivative were heated together without agitation t o about 230" C. and zinc acetate waa added slowly with stirring but without any substantial increase in the temperature. In some cases an acid catalyst was used with a particular aldehyde to help form the aldehyde-modified rosin. In such CBS~B it was necessary to remove the excess acid to prevent the formation of incompletely soluble zinc resinates. To avoid darkcolored resinates, it was desirable to use an inert atmosphere. When an inert atmosphere waa used excessive blowing or sparging of the mixture during the reaction was avoided to prevent excessive loss of aldehyde. In other cases, this latter difficulty was avoided by reacting the rosin and the aldehyde under pressure a t 200" C. and then reacting the aldehyde-modified rosin with the zinc compound. When nonvolatile aldehydes were used substantially quantitative yields were obtained.
TABLEI. ZINCRESINATESPREPARED FROM FORMALDEHYDE MODIFIED ROSIN
WW gum rosin used as starting material had an acid number 168 and a softening point of 72O C nngand ball. b Baker's 0.p. zinc oxi'6e. Softening p i n t s were determined according to procedure outlined in 8STM e-28-42 (1949) Part 4.
Another method of preparation was to react the rosin and aldehyde together in an inert solvent and then add a calculated amount of the zinc compound to the solution and reflux together, using a Dean Stark trap to trap out water and unreacted aldehyde until a clear, homogeneous solution resulted. When formaldehyde was used, to prevent excemive loss. of the gas, it wag necessary to react rosin with the formaldehyde first and then add the solvent and the zinc compound and reflux. A typical zinc resinate was prepared as follows: One thousand grama of WW gum rosin were added t o a %liter, three-necked, round-bottomed flask. Ten grams of para349
INDUSTRIAL AND ENGINEERING CHEMISTRY
350
Stability. Zinc resinates prepared from aldehyde-modified rosins showed improved stability to oxidation over unmodified rosin. On exposure to air in a dust-free cabinet a powdered zinc resinate containing 8.87@zinc prepared from a 6% formaldehyde-modified rosin gained only 0.06% in weight in 13 days, whereas a sample of the powdered rosin t o which no aldehyde had been added gained 2.8% in weight in the same time. Zinc Content. The maximum zinc content obtainable in a clear, homogeneous, varnish solvent-soluble zinc resinate prepared from the aldehyde-modified rosins using zinc oxide is approximately the stoichiometric amount of zinc which will react with the free carboxyl groups available to form a zinc diabietate. When zinc acetate was used the maximum zinc content obtainable was approximately twice the stoichiometric amount of that required for a zinc diabietate. The zinc content of the products obtained using rosin derivatives of low acid number modified by aldehydes varied widely. The theoretical and maximum zinc contents are listed in Table 111. Table I11 shows that 100 parts of a rosin having an acid number of 168, when modified with formaldehyde, reacted with 66 parts of zinc acetate (dihydrate), whereas only 33 parts would be necessary to form the zinc diabietate. This reaction seemed to follow the expected pattern and form the zinc acetate-abietate. The table shows that low acid number rosin derivatives such as methyl abietate, rosin oil, etc., which would require only small amounts of zinc acetate to form neutral products, reacted in a different manner. Them resinates have a zinc concentration of from 10 to 80 t h e S that which would be expected t o react with the free carboxyl groups present, and they may contain as much as 2 moles of zinc per mole of rosin derivative. Solubility. A]] the zinc resinates showed good solubility in the common varnish solvents. They were completely soluble in benzene, turpentine, mineral spirits, and ethyl acetate in concentrations up to 40 to 60% solids, The solubilities listed in Table Iv were determined by crushing approximately 2 grams of the zinc resinate to pass an 8-mesh
TABLE 11. . ZINC RR~INATES PREPARED FROM ALDEHYDEMODIFIED ROSIN@ Parts by Weight of Modifying Agent/lOO Parte Rosin 5
Softening Point Zinc Resinate ( ~ and i ~ BaTl),
Color Grade, u. 8. Reaction Modifying Te0mp.* Agent Used C. O c. Paraformaldehyde 250 105 H Aqueous formaldehyde 85 260 114 K Gaseous formaldehyde 5 250 103 G Trioxymethylene C 5 250 104 H Acetaldehyde 5 275 121 M Paraldehyde 1 260 123 N Propionaldehyde 1 260 111 I Butyraldehyde 5 260 128 H Isobutyreldehyde 1 275 104 H n-Heptaldehyde 5 260 105 G 2-Ethylhexaldehyde 5 275 108 K Stearic aldehyde 5 275 94 K Benzaldehyde 1 275 140 M 1 260 138 G Salicylaldehyde 5 260 112 G Anisaldehyde Crotonaldehyde 1 275 116 I Glyoxal 0.03d 275 113 G Acrolein 1 290 116 H 5 275 100 WG Acetal Dihydropyran 1 260 113 K M e t h y la1 5 275 108 N 5 10 parts of Baker's C.P. zinc oxide per 100 parts of WW gum rosin. 5 20 p a r t s of 40% aqueous solution. C Trioxymethylene used was D u Pont's Trioxane. d 0.1 p a r t of a 30% aqueous solution.
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Vol. 44, No. 2
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(Merck Ck c O ~ were added, and a thermometer, glass stirrer, and s, Dean tark moisture tra with a water were The char e was heate$ with a Type M Glas Col heating mantle to 170' for 1 hour. The agitation was commenced and the temperature was increased to 250° i 5' C. Then over a period Of 5 hours, 90 grams Of Zinc oxide (Baker's c.P.) were added in IO-gram increments allowing 30 minutes for each ortion to react. The temperature was held a t 250 ' i5°C. for 2 fours. The zinc resinate was cooled to 175'C. and poured. The zinc resinate had a color grade of M (U. s. Rosin Standard) and a softening point of 102' C. (ring and ball). The product w&9 soluble In turpentine, ethyl acetate, mineral spirits, and petroleum naphtha.
8.
PROPERTIE S
Color Grade and Softening Points. The fused zinc resinates prepared from the different aldehydemodified rosins were homogeneous, a m o r phous resins. The color grade and softening point varied widely with the amount and type of zinc compound used, the amount and type of aldehyde used, and the type of rosin or rosin derivative used. The properties of zinc resinates prepared from formaldehyde-modified WWgum rosin are shown in Table I. Table I1 shows that some higher molecular weight modifying agents gave resinates of better color grade and softening point than did formaldehyde. M o d i f y i n g agents such 88 c h l o r a l , chlorobenzaldehyde, nitrobenzaldehyde, and cinnamaldehyde gave zinc resinates whose color grades were darker than F by the U. S. Rosin Standard.
TABLE111. ZINC RESINATES PREPARED FROM ALDEHYDE-MODIFIED ROSINDERIVATIVES Rosin Derivative Used, 100 Parts Acid No. of rosin derivative used Aldehyde used, 5 parts Stoichiometric5 amount of zinc acetate (dihydrate), parts Fy weight Zinc acetate (dihydrate) reacted, parts by weight Softening point (ring and ball) C. Color i r a d e , U. S. rosin standard 0
b
Rosin
Methyl Abietate
Rosin Oil
Ester Gum
168 Formaldehyde
5 Formaldehyde
17 Formaldehyde
Formaldehyde
0.98
33 66
130
3.34
9
1.76
RosinQ D r ing ' &1
Methyl Abietate
60 Formaldehyde
5 Paraldehyde
Ester Gum
9 17 Butyral- Bensaldehyde dehyde
0.98
11.8
Rosin Oil
1.76
3.34
37
50
100
110
79
79
65
Liquid
Liquid
124
142
123
135
Liquid
...
...
F
N
B
G
D
...
The rosin drying oil was prepared b y the method outlined in U. 9 . Patent 2,429,264. Based on acid number of rosin derivative. OF FUSED ZINC RESINATES TABLE IV. SOLUBILITY
Modifying Agent, Parts by Wei ht/ 100 $arts Modifying Agent Rosin Paraformaldehyde 4 Paraformaldehyde 4 1 Acetaldehyde 5 Paraldehyde 2-Ethylhexaldehyde 5 5 Benzaldehyde 0.03= Glyoxal 1 Furfural Dihydropyran 5
Parts Zinc Oxide/ 100 Parts Rosin 7 5 10 10
10
10 10
lo6
PetroHex- leum Mineral Turpenane Naphtha Spirits tine P S S S S S S S I S P S P S S S S P S S S S S S P S S 6 S
s
S
S
S S
S S
Benzene S S
S
S
S
S
Methyl Acetate P P I P P
S S
S
0.1 part of 30% aqueous glyoxal. P = Partially soluble: more t h a n 90% of resin dissolved, b u t some residue remained. S = Soluble: completely dissolved. I = Insoluble; less t h a n 90% of resin dissolved, very heavy residue. 0
S
P P P
Ethyl Acetate S S S S
9 S S
S 9
Amyl Aoetate S S S
S S S S S
S
February 1952
INDUSTRIAL AND ENGINEERING CHEMISTRY
screen and adding the required amount of solvent at room temperature to give a solution containing 20% solids. The flask containing the resin and solvent was placed on a shaking machine and agitated until the resin dissolved or until no more of the resin would go into solution. All benzene solutions of zinc resinates reported in Table I V could be diluted with more than an equal volume of alcohol before the solution became cloudy.
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resinates may be prepared from rosin derivatives which have acid numbers of less than 20. LITERATURE CITED
(I) Bain, J. P. (to Nelio Resin Processing Co.), U. S. Patent 2,374,657 (May 1, 1945). (2)Borglin, J. N., Mosher, P. R., and Elliot, H. A., IND. ENQ.CHEM., 36,752-6 (1944). (3)Bried, E. A. (to Hercules Powder Co.), U. 5. Patent 2,383,289 (Aug. 21, 1945). (4)Low, F. S.,Ibid., 1,243,312(Oct. 16,1917). (5) Palmer, R. C., and Edelstein, E. (to Newport Industries), Ibid., 2,346,994(April 18, 1944). (6)St. Clair, W.E., and Lawrence, R. V. (tosecretaryof Agriculture), Ibid., 2,572,071(October 1951).
CONCLUSIONS
A simple method of preparing fused zinc resinates has been developed by modifying rosin with an aldehyde and fusing this aldehyde-modified rosin with a reactive zinc compound. Zinc resinates prepared from aldehyde-modified rosins do not block and show good solubility in the common varnish solvents. Zinc
RECEIVED June 27, 1951.
Rate of Isomerization of Cyclohexane J
EFFECT OF ALUMINUM CHLORIDE AND HYDROGEN CHLORIDE A. I?. LIEN, E. L. D'OUVILLE, B. L. EVERING, AND H. M. GRUBB Stundard Oil Co. (Indiana),Research Department, Whiting, Ind.
ANY publications on hydrocarbon isomerization have dealt with the catalytic activity of aluminum chloride in conjunction withother substances, most frequently hydrogen chloride. It has been postulated by Powell and Reid ( 1 1 ) that the actual catalyst is the strong acid HAlCI,, resulting from the association of the two catalyst components. However, all attempts to isolate HAlCld as such have been unsuccessful ( 1 , 16). Brown and Pearsall(1) have shown, on the other hand, that aluminum chloride and hydrogen chloride do interact stoichiometrically in the presence of a substance to which basic properties may be ascribed. Recent workers have found thqt, with carefully purified mat e r i a l ~aluminum ~ chloride-hydrogen chloride does not catalyze the isomerization of either alkanes ( 9 ) or cycloalkanes (13)a t moderate temperatures. However, these smne workers have shown further ( 9 , i O , is, 17) that traces of other substances, such as olefins, oxygen, or water, convert aluminum chloride 60 I 1 I or the aluminum chloridehydrogen chloride mixture into an a c t i v e c a t a l y s t . 50 Stevenson and Beeck (IS) have postulated a partially heterogeneous catalysis with aluminum chloride in the p r e s e n c e of w a t e r . The 340a nature of the catalyst in the I +=presence of these added substances has remained obscure kzi and the mutual effect of the 20 components in the hydrogen Y 0 chloride-aluminum chloride P system has not been clearly 10 established. The principal purpose of the present work was to inI I I 0 vestigate the effect of aluminum chloride and hydrogen chloride concentrations on
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the rate of isomerization of hydrocarbons, using c'ommercial reagents such as would be available in large scale industrial applications. Cyclohexane was chosen for investigation because of relative freedom from the side reactions normally encountered in isomerization of alkanes (3,6)and because of ease of analysis of the products. During the investigation the equilibrium between cyclohexane and methylcyclopentane was determined a t several temperatures and the effect of hydrogen pressure on reaction rate was investigated. METHODS AND EQUIPMENT
Commercial reagents were used in all cases, and the experiments were carried out in a steel reaction vessel without special precautions t o exclude traces of air-or moisture. I
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of 1.4262 at 20' C., from Dow Chemical Co., aluminum chloride from Hooker ' E l e c t r o c h e m i c a l Co., and anhydrous hydrogen chloride from Harshaw Chemical Co. were used as obtained. To ensure uniformity of particle size as well as of composition, the aluminum chloride used in all runs was from the same batch. APPARATUS.The reactions were carriedout in a 1550-ml. carbon-steel pressure reactor provided with a 1725-r.p.m. m e c h a n i c a l s t i r r e r . The reactor was so jacketed that
