700
INDUSTRIAL AND ENGINEERING CHEMISTRY
tlemoiistrat,ed most readily by measurement of t'he relaxation or compressive st'ress a t 0" C. Such set data following a conditioning Iwriod of 7 days are summarized in the bar graph chart Figure 10. All stocks were loa.ded with 40 volumes of MT carbon black and cured 45 minutes a t 153" C. The Neoprene Type GK vulcaiiizat,e, with 15 parts of ester plasticizer, takes a set of essentially 100%. The addition of sullur to this compound or the replacement' of the ester with an cyual amount of PI-IC effect an appreciable reduct,ion in set. I stock combining the advaiitages of both P H C and sulfur reduces the set value markedly, and the substitution of n'eoprene Type ItT for Seopreiie Type GN in this latter compound brings ahout un even greater improvrmc:nt. SUMMARY
Crystallization and its consequences in neoprene may be conlrolled in both uncured and vulcanized stat,eby: 1. The copolymerization of a small amount of a second niononier, such as styrene, during the manufacture of the elastomer. 2 . The addition of certain types of polymerized hydrocarbons cqiable of physically interfering Trith crystdlization. 111 addition,
vulcanizate crystalliza.tion may also be inhibited by:
3. Vulcanization to a high state of cure.
4. Vulcanization by a long or accelerated cure in the presence of added sulfur.
These methods may be used successfully in combination mit,h
Vol.. 42, No. 4
benefits which are least additive. In all cases consideration should be given to possible effects on other required properties. The seriousness of problems arising from the crystallization oi' neoprene is tempered by the reversibility of the process which eliminates or minimizes crystallization in products subject even intermittently t o fairly high temperatures or mechanical work. LITEHATURE CITED
(1) AIEi,ey, T., a n d Mark, H., K u b h e i Chern. T'eci~nol.,14, 526 (1941). ( 2 ) ,Ani. Soc. T e s t i n g Materials, Designation D 832-46T, p. 203 (1949).
(8) Hekkedahl,
K.,J . Research S a t l . B U T . S'fundards, 13, 411 (1934); Rubber L'hem. Technol., 8, 5 (1935). (1) Clark, G . I,., Kothius, E., and S m i t h , W ,H., J . Re Bur. S t a n d a d s , 19, 479 (1937). (5) Forman, D. R.,du Pont Co.. Rubber C h e m . Div.. Rept. BE-196 (1945). (6) Formail, D. B., ISD. >;.VC:. CHERT., 36, 738 (1944). and Rndcliff, R.R., Ibid.,38, 1048 (1946). and Field, 3 . E.. J . A p p l i e d Phys., 10, 564 (1939). D. Exa. CHEM., 36, 40 (1944). (10) h l o r r i s , R. E.. Hollister. J. TY,, aiid Slallard. 1'. -i., I n d i a Rubber F o r l d , 112, 455 (1945). ( I I) Rostler, F. S.,and Sterriberg, IT. W , , 1x1).&:NO. C:EII:II.. 41, 598 (1949). (12) Smith, W . H., a n d Saylor, C . P...I. Bbaenrch, AVatl. Bur. ,S'ta7~durds, 21, 257 (1938). (13) IYood, L. A , , Eekkedahl. N . , and Gibson, 1%.E , , Ihid.. 35, 876 (1945). R E C E I V EJune D 2 5 , 1949, l'reeerited befose the spring meeting of the Division of Rubber Chemistry of the A V ~ R I C A SCHENICAL S o c I m y , Boston, Mass., M a y 1949.
J
N. R. BHOBV
AN^
Polytechnic I n s t i t u t e
Styrene is copolymerized by the mass method with commercial fatty acids having conjugated unsaturation, and the rates of reaction are reported for various amounts of excess styrene. Alkyd resins are made by reacting the sty-renated fatty acids of dehydrated castor oil with phthalic anhydride and glycerol. A laboratory process is described for completing both the copolymerization and the alkyd resin reactions i n from 4 to 6 hours. Evalua-
s
NEIB'MX- F. PAIPiE
of Brooklyn, Brooklyn, S. Y .
T P R E N E is becoming an increasingly important raw niaterial for use in organic surface coatings. However, a t the present time it is riot used in coatings as monomer nor as polystyrene but rat,her as copolymers with such materials as butadiene, drying oils, and most recently nith alkyd resins. The volatility of the monomer and lack of compatibility of the polymer are the principal deterrents from the use of these niaterials as such. The advantages obtained from the styrene-copolyinerized oils and alkyds are faster drying, harder film, and bett,er water arid chemical resistance t,han can be o b t a i n d rrith the straight oils or alkyd resins. However, the copolymers of styrene and various niaterials retain some of the sensitivity of polystyrene to certain hydrocarbon solvents. The tremendous 1)roduction capacity for styrene, resulting from its extensive use i n the synthetic rubber program during the last war, its wlarively loa cost, and very high degree of purity make it of defiriit'e iuterest for the surface-coating industry. One of the first methods proposed for the reaction of styrene with a drying oil was disclosed in a British patent (6) in 1931.
tion of the experimental stj-renated alkyds in clear films and in white enamels shows that they have superior t l r j i n p time and chemical resistance to conventional phthalic alkyds. In view- of the present and possible future price structure of styrene and the other resin-forming ingredients i t appears certain thal styrenated alkyds will be important in the surface-coating industry from both economic and performance considerations.
This describes the polymerization of an aqueous emulsion of styrene and tung oil with hydrogen peroxide as catalyst. The next development was the use of the solvent method for copolymerization of styrene and film-forming materials in inert solvents in 1934 ( 7 ) . This work was investigated further by 14'akoford and Hewitt ( 8 ) , Wakeford, Hewitt, and Armitage ( I O ) , and Wakeford, Hewitt, and Davidson ( 1 1 ) from 1942 on\vards in a number of British patents. The mechanism of copolymerization between styrene and various drying oils i s described by IIewitt and A4rinitagc.( 5 ) anti the effect of various solvents waR studied by Armitage, IIewit't,, and Sleightholme ( 2 ) . They used as a standard formula 50 parts solvent, 25 parts oil, and 25 parts styrene without catalyst. They also applied the same method for styrenation of a prepared alkyd; however, t,he method requires about 30 hours for reaction. Dunlap (4)and Takrford, €iewit,t, and Armitage (8) in 1945 investigated the mass method of copolymerizing styrene and various drying oils. The Inass method is much faster than the solve~itmethod hut only limited amounts of styrene can be co-
April 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 C H E M I S T R Y
polymerized and still maintain homogeneous products. I n this country the Dow Chemical Company (3) developed a system for obtaining homogeneous products by the mass method by replacing part of the styrene with a-methylstyrene. This combination produced homogeneous products with drying oils containing a conjugated system of unsaturation. \;\rith oils such as linseed and soya, it is recommended t h a t blends be made with tung or dehydrated castor oil t o introduce some conjugated unsaturation. However, the use of a-methylstyrene has been found to detract from the fast drying time and also t o reduce the resistance t o solvents and chemicals. It is obvious t h a t it would be desirable t o use the mass method because of its speed of reaction and t o avoid the use of a-methylstyrene, if possible. The present work shows that this may be done by first styrenating the fatty acids followed by esterification with phthalic anhydride and glycerol t o produce a styrenated alkyd resin. STYRENATION O F FATTY ACIDS
The copolymerization reaction between styrene and drying oil fatty acids depends on the type of the fatty acids used. With the conjugated fatty acids, like tung and oiticica fatty acids, the reaction is believed t o be similar to that between styrene and butadiene in GR-S manufacture. I n this case, styrene is joined to butadiene by 1,4-and 1,a-additions (1). With dehydrated castor oil fatty acid and isomerized linseed fatty acid (diene value 22 and 20, respectively) i t is believed t h a t there is some polystyrene formed along with the copolymer. Armitage, Hewitt, and Sleightholme (9)have stated t h a t polystyrene of high molecular weight was not formed, but they had not proved t h a t polystyrene of low molecular weight was absent. There is every reason for believing t h a t polystyrene of low molecular weight might be present. With linseed fatty acid, where there is a nonconjugated double bond system, the copolymerization reaction does not take place to any appreciable extent. This can be seen from other similar systems such as vinyl chloride (nonconjugated) and styrene (conjugated) which does not copolymerize. I n general, a monomer containing a conjugated double bond system will copolymerize with another molecule containing a conjugated double bond. However, Armitage et al. (6) have recently suggested that copolymerization with nonconjugated systems might take place by the shift hydrogen mechanism in special circumstances. MATERIALS
The fatty acids used were those commercially available; tung from Archer Daniels Midland Company and oiticica, dehydrated castor oil, and linseed from Woburn Degreasing Company. Styrene was obtained from the Dow Chemical Company and i t was found from a few experiments that it was not necessary to remove the inhibitor. Benzoyl peroxide was used as catalyst.
701
after vacuum distillation. This value was checked from acid number determinations. The ratio of actual acid number t o the theoretical of 195 for fatty acid indicates the per cent fatty acid present. The method of calculation is shown by the following illustration : Styrenation of Tung Oil Fatty Acid Grams % by weight Tung f a t t y acid (1 mole) 288.0 30.6 Styrene (6 moles) 624.0 67.4 Benzoyl peroxide 18.7 2.0 930.7 100.0 Sample Withdrawn after 3 Hours of Reaction Wt. of sample taken 9.814 Wt. of sample after vacuum distillation 5.076 Free styrene 4.738 Styrene i n original -67.4 X 9.814 , 6.600 Styrene removed b y vacuum distillation 4.738 Styrene reacted 1.862 1.862 % styrene reacted = = 28.2% 6.6 1.862 yo styrene i n product = = 37% 5.076 Acid number after vacuum distillation 121 Acid number of f a t t y acid 195
121 = 62% fatty acid, 38% styrene in product 195
The value for the per cent styrene in the product as determined by the vacuum distillation method checks rather closely with that obtained by the acid number method. Copolymerization of styrene with tung, oiticica, and dehydrated castor oil fatty acids was carried out using various molal ratios of styrene. The rate of reaction increased with increased ratio of styrene and the values are plotted in Figure 1. The corresponding values for per cent styrene reacted and actual and theoretical acid numbers are given in Table I.
TABLEI. PER CENT STYRENEREACTED AND ACTUALA N D THEORETICAL ACID NUMBERS Styrenated Tung F a t t y Acid Moles Styrene t o 1 Reaction yo Styrene Actual Theoretical Nature Mole F a t t y Acid Time, Hr. in Product Acid No. Acid No. of Product 2 . 22 35 127 126.8 Via. liquid 6 67 13.5 66 64.5 Vis. liquid 8 72.5 13 56 54 Clear solid resin 11 10 77 45 45 Clear solid resin 14 10 80 36 34.2 Clear solid resin Styrenated Oiticica F a t t y Acid 2 12.5 15.0 121 120.2 Vis. liquid 4 12.0 53.0 87 87.0 Vis. liquid 11.0 63.2 6 68 68.0 Semisolid 8 4.5 69.5 56 I 56.5 Solid resin Styrenated Dehydrated Castor Oil F a t t y Acid 2 19 41.0 117 118 Vis. liquid 4 13 57.6 83 84.8 Vis. liquid 6 9 67.1 66 65.8 VIS. liqu/d 8 9 72.9 54 54.2 Solid resin Styrenated Isomerized Linseed Aoid 6 9 65.5 63 66.5 Semisolid 10 7.5 75.0 43 44.0 Solid resin
PROCEDURE
The copolymerization reaction between styrene and tung oil fatty acid, oiticica oil fatty acid, dehydrated castor oil fatty acid, linseed oil fatty acid, or isomerized linseed oil fatty acid was carried out by the mass method. I n all cases 3% benzoyl peroxide on the weight of styrene was used. The fatty acid and styrene with catalyst were placed in a 4necked flask and heated to 145" C. by a n electric mantel. Through the central neck a stirrer with mercury seal was attached. I n the three side necks were attached a thermometer, a condenser, and a n arrangement for withdrawing samples. I n the case of dehydrated castor oil, linseed, and isomerized linseed fatty acids a separatory funnel was attached in one of the side necks through a Y-bend connection, and styrene catalyst mixture was added slowly to the fatty acid in the reaction flask. Samples were withdrawn at various intervals of time and the per cent styrene which had reacted was determined by removing the unreacted styrene using vacuum distillation (6 to 8 mm., 40" C.). The amount of styrene which had reacted with the fatty acid was calculated from the difference between the known percentage of styrene present originally and the percentage found
Attempts were made to styrenate standard linseed fatty acids but the products obtained were heterogeneous which is related to the nonconjugated unsaturation in this fatty acid. The isomerized linseed acids shown in Table I have a diene value of 20 and consequently produced homogeneous products after styrenation. The styrenated products containing less than about 70% styrene are clear viscous liquids, with increasing viscosity as the styrene content is increased. Above 70% styrene content the products are hard resins. These styrenated products are mixtures of mutually soluble materials which include t h e copolymer of styrene and fatty acid in the largest amount and considerably smaller proportions of polystyrene and free fatty acid. RATE O F STYRENATION O F FATTY ACIDS
The general average values for rate of styrenation of a series of experiments are plotted in Figure 1; a comparison of thcse
INDUSTRIAL AND ENGINEERING CHEMISTRY
702
Vol. 42, No. 4
T h e saving in time would be offs omewhat by the added C O * I of removing a larger quantity of free styrene and by the largcr reactor capacity m hich would be required.
The rat,es for the three fatty acids are in the reverse order from what might be expected, from a consideration of the fact that tung contains the greatest percentage of conjugated unsaturation and dehydrated castor oil contains the least. This reversal of the order of the rate of reaction may be due to a smooth copolymerization reaction with the tung acids and a relatively low molecular weight product. The ketonic group in the oiticica fatty acid may be expected to exert an accelerating effect on the copolymerization r e a d o n , hence a faster rate than t,he tung acid. Iri the dehydrated castor oil acid reaction there i s formed, most probably, some polystyrene in addition to the copolymer. Because the rate of react,ion for the Iiolymer is faster than that. for the copolymer, the over-all rate is higher as shown. Although the styrenatccl product from the dehydrated castor oil reaction was sufficieritly homogeneous for normal use in alkyd resins it, \vas not so smooth as the others, indicating some polystyrene present. A marked difference in rate of rcaction and type of product fornicd could be obtained by varyiug the manner in which the styrene was added to thc dehydrated rastor oil fatt,y acid. When the styrene and dehydrated castor oil fatty acid are hoat'ed together a rapid, exothermic reaction develops xhen the tempcrature reaches 120 ' C. and the product is very viscous and turbid. Hoyever, if the styrene is added to the fatty acid a t a slow ratc the reaction is smooth and the product is clear and apparently homogeneous. This method was adopted in making the styrenated fatty acids for the alkyd resins described later because it yields a honiogeneous product with a minimum of polystyrcric and a maximum of the copolymer.
70
w 40--
PROCESS FOR STYRENATED ALKYDS
,-FI
ISTYqENE] CATALYST
T I M E I N HOURS
Figure 1. A.
H. C.
aylfi I
Hate of Reaction
lloles of st>rene to 1 mole of fatt? acid Sttrene with tung fattv acid Sttrene wdth oiticica fatty arid Styrene with dehjdrated castor oil fatt) acld
VACUUM DISTILL
EXCESS STYRENE
INERT GAS
t
.)
PHTHALIC ANHYDRIDE
STY RE NATE D
curves shows the slowest reaction rate for tung fatty acid, a sonic'what faster rate for oiticica, and the fastest rate for dehydrated castor oil. These differences in rate apply a t all ratios of styrene to fatty acid but in each case a faster rate is obtained by increasing the amount of excess styrene. Fast reaction rates are always desirable in commercial operations and these map be obtained by using about 4-niole ratio 01 2-mole ratio of cscess styrene.
in
.I B
SOLVENT
Figure 2
T.ABI,E 11. STTRE:NATED .ALKYD I t ~ s ~ s s --
Res-
Solid Resin % by Weight Styrenated Phthalic oil anhydride
, Glyceryl phthalate 2G.8 89.2
73.2 60.8
20.8 30.4
Styrene 28.1 22.1
GLYCEROL
I
Acid No.
11 9.2
Solrent hI.S,a 50 M.S. 30 xylol
Solids,
Resin Solution Visrouity.
70 Oardner FIOldt
60 50
.J
1-
Color, 1938
(;
11 12
Clear Film Properties Drying _-___ Time Set t o
A B a
touch, inin.
Dust-free,
Dry hard,
20 1.5
3
4
Mineral siiirits.
hr. 2
hr. 3
Air Dry 24 hr. 18 36
48 hr. 22
40
Bw.ard_IIardness _ _ _ _ _ _ _ _ - ~ . . Bake .150° F., 2 X 0 F.. 3 0 F 168 hr. 30 Inin. 2 0 inin. 10 min. 24 22 34 26 4 8 12 52 46
INDUSTRIAL AND ENGINEERING CHEMISTRY
April 1950
TABLE
111.
WHITE
E ~ A M E LFORMULATION Parts by Weight 200 500 210
Titanium dioxide Resin solution (50Y0solids) Xylol
Cobalt naphthenate ( 5 % C o )
1.5
Resins Used Styrenated alkyd resin A Styrenated alkyd resin B Phthalic alkyd, Resyl 3 8 7 - f ~ ~ Phthalic alkyd SO%, urea formaldehyde ZO%, Rezyl 387-5a, and Beetle 227-8& E $5 Phthalic alkyd, E’CD 515b E G Styreneted alkyd, Cycopol S 10:-lu E 7 Styrenated alkyd, Styresol 4400 ( I American Cyanamid Co. b France, Campbell & Darling, Inc. C Reichhold Chemicals, Inc.
E 1 E 2 E3 15 4
703
The enamels xere sprayed one coat on bare steel panels except the weatherom-ter panels which were given one coat of chromate primer, Navy Specification 52-P-18, and one coat of white enamel. The results show the experimental styrenated alkyd? to have excellent air drying and baking characteristics. The resin used in E 5 is a longer oil alkyd and would be expected to have slower drying properties and lower chemical resistance. The styrenated alkyds are faster drying than conventional short oil alkyds or the alkyd-amino resin mixture and they exhibit verv good film properties. The general results show that satisfactory styrenated alkyds may be made bv the styrenated fatty acid process described in this paper. SUMiMARY AND CONCLUSIONS
Styrenated dehydrated castor oil phthalic alkyd T4HLB. I V KNAMEL C H \ R I (rIcRx,rrCs A V D FILM1’RopE:xrrei resins may be made by first styrenating- the dehySward drated castor oil fatty acids and then allowing Hard\-lbCOEness, them to react with phthalic anhydride and glycerol. 1t). Gloss, 60’ Glossmeter Air Dry Hake See.. Sq;t, Hard, 2’oo F., Weatherometer When made by the mass method, without solNo. 4 min. hr. 30 niin. Original 50 hr. 250 hr. 450 hr. vent, the process is quite rapid, requiring only 4 Ford Resin 15 3 30 95 89 55 40 4o to 6 hours. By adding the styrene to the dehy80 E l 10 2 10 95 82 50 77 E 2 20 5 28 95 85 43 40 drated castor oil fatty arid slowly a homogeneous E 3 55 80 E 4 . . . 32 10 95 80 75 80 40 35 product is obtained without resorting to modi4 0 18 40 E 4 70 E 6 10 2 -10 90 80 52 35 fication with a-methylstyrene. The use of an es10 1 . 5 5 2 0 0 80 50 40 E 7 75 cess of styrene during the reaction speeds the procCliemicai Resistance ess considerably. 270 Acetic, Fruit Acid, Gasoline, Comparison of the experimental styrenated Resin 2Ei 24 Hr. 24 IIr. 3 Hr. alkyds with recent commercial products shows E l 3 O.K. O.K. v. SI. soft E 2 4 O.K. 0.K. v. sl. soft them to be rather similar in film characteristics, E3 3 Soft SI. soft SI. soft although no attempt was made to duplicate these E 4 5 O.K. O.K. O.K. E 5 1 Soft Boft Soft products. SI. soft v. sl. soft $1. soft E6 3 The styrenated alkyds have faster air drying O.K. Soft s1. soft E7 3 and baking properties than medium or short oil phthalic alkyds. They also compare favorably in general film properties and show somewhat better STYRENATED ALKYD RESINS cshemical resistance. It is apparent that these materials have a definite field of usefulness in the surface-coating industry both Styrenated alkyd resins were made by the reaction of styrenfrom a performance and an economic viewpoint. ated dehydrated castor oil acids with phthalic anhydride and glycerol The st,yrenated acids were made by using the 2-mole ACKNOWLEDGMENT excess of styrene described previously and adding it to the dehydrated castor oil acids slowly over a 1.5-hour period. The Thanks are due to the Hilo Varnish Corporation for their 4-mole curve in Figute 1, C, shows that the styrenated dehydrated cooperation and use of their laboratories, and t o the late J. J. castor oil acids contained 41% styrene at this point. The Mattiello for his advice and suggestions. phthalic anhydride and glycerol were added to the styrenated fatty acids and heated to 430”F. in 30 minutes. The batch was held LITERATURE CITED a t 450” F. for 50 minutes giving a total processing time of 80 minutes. A4stream of carbon dioxide was passed through the (1) Aleksewa, E. N., and Bettitskaya, R. M,,J . Gen. Chem. (U.S. resins during processing. Resin A (Table 11) was thinned to 60% S.R.), 11, 358-62 (1941). (2) Armitage, F., Hewitt, D. H., and Sleightholme, J. J., J . Oil & solids with mineral spirits and resin B was thinned to 50% solids Colour dhemists’ Assoc., 31, 437 (1948). with a 50 t o 50 mixture of mineral spirits and xylol. The over-all (3) Dow Chemical Co., “Styrenated Drying Oils,” Coatings process is shown in Figure 2. Cobalt naphthenate drier was Technical Service Bull., 1948. added to the resin solution to give 0.02% cobalt as metal to resin (4) Dunlap, Lawrence H., U.S. Patent 2,382,312 (August 15, 1945). solids and the solutions applied to tin and glass panels with a (5) Hewitt, D. H., and Armitage F , J 0 2 1 &: Colour Chenzzsts’ draw-down blade having a 3-mil clearance. The composition Assoc., 29, 103 (1946). and film properties of styrenated alkyd resins A and B are shown (6) I. G. Farbenindustrie, A.-G., Brit. Patent 362,845 (Dec. 7, 1931). in Table 11. (7) Lawson. W. E., and Sandborn, L. T , U S . Patent 1,975,353 The composition of the resins A and B in Table I1 mas deter(Oct. 9, 1934). 181 mined theoretically from known input. No attempt was made ~, Wakeford. L. E.. and Hewitt, D. H.. Ibid., 573,803 (July 28, 1942); U.S. Pat. 2,392,710 (Jan. 6, 1945). t o analyze for these characteristics, because it is recognized that (9) Wakeford, L. E., Hewitt, D. H., and Armitage F., Brit. Patent the actual resins are more complicated in structure than is im573,835. plied in the composition given. The fast air drying and baking (10) Ibid., 580,912 (Sept. 24, 1946). properties of the clear films indicate that these resins are quite (11) Wakeford, L. E., Hewitt, D. H., and Davidson, R. R., Ibid., desirable for surface-coating materials. 580,313.
!i
2
-
4
EVALUATION IN WHITE ENAMELS
were made with resins A and B and several White commercial resins. The formulations are given in Table I11 and the evaluation results in Table IV.
RECEIVED August 10, 1949. Presented before the Division of Paint, Varnish, and Plastics Chemistry a t the 116th Meeting of the ASfERICAN CHEZ.11CAL SOCIETY, Atlantic City, N. J. This work is part of the requirements for the D,ChE. - submitted bv N , R, Bhow to the faculty of Polytechnic Institute of Brooklyn, Brooklyn, N. Y.
