STYRENATED ISOPHTHALIC ALKYDS Styrene Content and Rates of Sprenation bv Vapor-Phase Chromatograpky W. K. SEIFERT AND D.
F. P E R C I V A L
California Research Cor$., Richmond, Calq.
A rapid, accurate method for determining styrene conversion in styrenated alkyds uses vapor-phase chromatography, Dependence of rates of styrenation on mode of catalyst and styrene addition and of styrene content on properties was investigated. Useful styrenated alkyd formulations based on isophthalic acid are described and physical properties are given.
alkyds have been of commercial importance for many years, and many authors have pointed out that the properties of these products depend on the amount and kind of oil used as well as the styrene content (3, 9, 70). Others have studied the rate of styrenation (7) and the chemical jtructure of the reaction products (,5). I n all of these investigations, it is necessary to determine the amount of unreacted monomer a t various stages of the reaction and 'or in the final product. The literature reveals that this is accomplished by nonvolatile tests of one type or another. Hempel (7) flashed off monomer a t 147' C. in a ventilated oven over a 30-minute period. Bhow and Payne ( 4 ) used vacuum distillation to determine per cent styrene reacted with fatty acids. Benner t-t a / . (2) point out that this type of analysis is considered accurate to within about 5%. T h e authors have found that a much faster and more accurate analysis can be achieved with vapor-phase chromatography. iVith this technique, the effect of catalyst and styrene addition on the rate of styrenation is shown and that the properties are drastically affected by styrene content. Yo attempt was made to elucidate the structure or structures of the styrenated products. Much has already been published on the chemical structure argument (5). TYRENATED
Experimental MAPreparation of Alkyds and Styrenated Alkyds. All oils used were commercially available from the TERIALS. Pacific Vegetable Oil Co. Pentaerythritol was 88% com-
300 300F I
ADD
ADO
AN 2 3 4 160 122* V l Z A T 6 6 6 % T S IN XYLENE K P- T
*
I Loo
7/
80
z V1S.OF REACTION M I X
I
1
P E = PENTAERYTHRITOL
,I
Figure 2 illustrates the separation of a mixture of 5% styrene and 95% commercial xylene a t a helium flolv rate of 50 ml. per minute, operating temperature of 145' C., sample size of 2 pl., injection temperature of 260' C.?detector temperature of 280' C., and recorder speed of l l ' 2 inch per minute. Styrene is clearly separated from o-xylene and the latter from the mixture of m-xylene. p-xylene, and ethylbenzene. Rrtention times measured from the point of injection are:
..
'm
Air
IP ISOPHTHALIC ACID VIS.= GARDNER HOLDT VISCOSITY AFTER COOLING TO ROOM TEMPERATURE Y
2
3
4
5
Preparation of styrenated alkyd on 20-kg. scale Corresponds to alkyd 1 , Table I
222
Analysis. The amount of unreacted styrene \vas determined by vapor-phase chromatography. T h e mixture of alkyd, xylene, and styrene was diluted with a n approximately equal amount of benzene to decrease the viscosity and facilitate sample injection. A Wilkens herograph 350 with a 10-foot X 0.25-inch 0.d. column (19c?, Carbowax 20 M on Chromosorb W, hexamethyldisilazane-treated) with a hot wire thermoconductivity detector and a Leeds and Northrup (1 mv.) recorder were used.
L
HOURS Figure 1.
,411 alkyds were prepared by a normal fusion process and are described in 'Table I. 'They were formulated to calculated molecular weights ( S ) of 1300 to 1500, which are low enough to be far below the points of gelation by esterification. 'Table I1 shows the various styrenation reactions, while Table 111 gives the physical properties of the styrenated alkyds. Styrenations were carried out in refluxing xylene. 'I'he amount of di-tert-butyl peroxide catalyst was kept small for reasons of commercial significance. Typical cooking logs for the alkyds and for styrenation are shown in Figure 1
-40
* FINAL VALUES 0
, , W z
/.
1
*
mercial grade from the Hercules Powder Co. SLyrene \vas rubber grade from the DOW Chemical Co. Glycerol was commercial grade from the Shell Chemical Co. Baker's analyzed xylene was used for solvent. Isophthalic acid was obtained from the California Chemical Co., Oronite Division. Procedure. Styrenated isophthalic alkyds could be prepared by any of the routes outlined by Payne (70) : styrenation of the fatty acid, of the oil, of the monoglycerides. or of the alkyd resin directly. T h e latter was used because of the commercial significance of this method. T h e kinds of alkyds (oils, oil length, type of polyol, etc.) that one might study are virtually unlimited ; but, in order to compare various products, experiments were restricted to a narrow oil length range (62 to 66.57,) and to glycerol-pentaerythritolalkyds.
I&EC P R O D U C T RESEARCH A N D DEVELOPMENT
m-Xylene 1' $-Xylene } Ethylbenzene j o-Xylenr Styrene
Minuter 1.6 8.3
10 6 13.0
I n four runs containing 5 to 10% styrene, the styrenexylene area ratio was divided by the stvrene-xylene weight
e T
6
9
r-4
\3 Ln
n
M.
0
-
r'r 3
i
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7
W
1
w
0
1
2
3
4
5
6
7
8
HOURS
Figure 3. Effect of mode renation
Figure 2. rene
1 2 3 4 5
44 44 24 34 24
9 12 12 12 ~~
11
14 14 14 13 13
catalyst addition on sty-
Alkyd 1, Table I. Styrene-xylene weight ratio 1 :0.66 :1.1 1, charged together at beginning A A. 3% DTB charged at start of cook B 0 . 1 % DTB charged a t start, 2% added after 5 hours C 0.6% DTB charged at start, 0.6% added after 1,2,3, and 4 hours
..
Vapor-phase chromatogram of xylene and sty-
Table 111.
of
Properties of Styrenated Alkyds
17 22 17 14 19
44
No Cracks No Cracks No Cracks
48
~~
26 14 150
d,*
No Cracks
After 15 days of aping. 0.03% Co and 0.03% Mn, 3-mil wet f i l m on 20-gage bonderized steel panels dried at 215' C. and SOY0 relative humidity. Product 1 is still better than 2 when bent further than ' / 8 inch. Aftrr 4 5 days of a,ying. e Cracks. to l / 2 inch on Reichhold brittleness mandrel, I / s to l l / s inches on conical mandrel.
ratio and a factor of 1.01 f 0.015 was found by which an analyzed styrene peak area has to be divided to correspond to weight. Since the weight ratio of styrene to xylene a t the start of the cook was known, the amount of unreacted styrene a t any time was easily calculated. T h e time from taking the sample to finished calculation was about 25 minutes. Other columns, gas chromatographs, detectors, and recorders may be used as outlined by ASTM Committee D 16 (7) and the factor to transform areas to weights will vary. However, the smallest degree of separation of isomers of xylene and ethylbenzene from each other will result in the smallest experimental error, provided that styrene is completely separated from o-xylene. T h e experimental error mainly depends on the accuracy of styrene area measurement, which, in turn, depends on the size of the styrene peak and thus on styrene conversion. In Figure 2, the experimental error is about 2 to 370 of the styrene present. T h e measuring of rates of styrenation in different alkyds is illustrated in Table 11. For comparison, the amount of styrene in the final product was also determined by a nonvolatile measurement. Table I1 shoivs that the nonvolatile tests, in spite of inhibition with diphenylquinone. generally resulted in too high styrene conversion values. Results and Discussion
reactants at the 5 t x i of the cook gives the fastest rate of reaction. Run C, which contains one fifth as much catalyst as run A during the first hour, reacts about 0.4 as fast as run A during that time. R u n B, which contains one third the amount of catalyst of run .4 during the first 5 hours, reacts 0.7 as fast as run A during that time. All three runs gelled a t 84 to 877, conversion of styrene, indicating that as styrene concentration decreases crosslinking of the product predominates. The reaction time or mode of catalyst addition does not affect maximum styrene conversion. Influence of Mode of Styrene Addition on Rate of Styrenation. Runs A and B were repeated, except that styrene was added dropwise during the first hour of reaction. This mode of addition gave a slower rate in the case of run A, faster viscositn build-up, and earlier gelation (76% styrene conversion). In thr case of run B. the rate of reaction, viscosity build-up? any
Table IV.
Effect of Styrene Content on Properties Viscosity Stvrene at 5Oc7n Dry Hard Sward Coitent, Total pime, Hardness, %a Solidsb Minutes 75 Days Flexibilitj 47.6 X+ 14 58 Brittle 36.7 X 44 44'1 No cracks on l / 8 29.8 1%' 295 381 inch mandrel Xylene solvent. Styrenation of alkyd 1, Table I. I
+
Influence of Mode of Catalyst Addition on Rate of Styrenation. Figure 3 shows that charging all the catalyst with the 224
I&EC PRODUCT RESEARCH A N D DEVELOPMENT
"
Table
V. Comparison of lsophthalic with Orthophthalic Styrenated Alkyd
acid
Alkyd 0 il 1P ng tha
Calcd. niol. lot. ( 8 )
IP P;I
66.5 64.0
1330 1350
-~
Dibasic
05:5 linrerd: tung.
b
0.65; total solids in .x$ene.
x
36.7 38.2
H+
507, total solids in xylene.
gelation \cere very similar. These results indicate that a t low s t y e n c concentration and high peroxide level crosslinking of the alkyd is occurring. D e p e n d e n c e of Properties on Styrene Content. Dry time, h a r d n r s . and flexibility of styrenated alkyds are markedly affrctrtl b>-styrene content. as shown in Table I\-. An increase decreases the dry time in styrene content from 20.8% to 36. from approximately 5 hours to3;i hour. Dry timecan be further reduced by a further increase in styenation. but flexibility is then diminished. A comparison of acid numbers before and after qtyrenation shoxced that no further esterification occurred during styrenatioii. and hence the observed change in properties is attributed solely to change in styrene contcnt of the s t y m a t e d alkyd. An almost 20% increase in styrene content showed little effrct on viscosity. For a 5y0 tung oil9.57, linheed oil isophthalic alkyd of 66.57, oil length, a 377, styrenr content appears to be optimum. \\‘hen alkyd 1 was styrenatrd (iring a different mode of addition than described in ‘[‘able II----by heating all ingredients together (run A. Figure 3) identical phyical properties \cere observed, a ? dewribed in Table 111. Alkyds containing other oils are shown in Tables I , 11. and 111. Although isophthalic alkyds us. phthalic anhydride alkyds \vex :Tot exhauutively studied, the results of a limited investigation are of interest. A‘phthalic anhydride alkyd and an isophthalic alkyd \cere formulated to the same calculated molecular bveight is(’). prepared under identical conditions, and then st)-renated to approximately the same styrene content. A s sho\vn in Table L7. the Etyrenated isophthalic alkyd was more viscous before. and after styrenation had more impact resistance and more flexibility (’l‘able 111). ~
Rd
T
2.5 2.0
3-mil z w t j l m s drawn down on 20-:a,fe bonderitrd steel panels.
Conclusions
A rapid, accurate method for determining styrene conversion in styrenated alkyds has been developed. T h e properties of styrenated alkyds are very dependent on the amount of styrene in the alkyd and rather small changes in styrene content cause large differences in dry time, flexibility, and hardness. I t is important. therefore, to know and control the styrene content in the finished alkyd within narrow limits. L’apor-phase chromatography allows one to analyze the alkyd quickly and accurately, and hence to control styrenation. Acknowledgment
-1he authors express their appreciation to the Oronite Division, California Chemical Co., for its intereyt in this study. literature Cited (1) Am. Sac. Testing Materials, Committee D 16, Industrial Aromatic Hydrocarbons,” Proposed Method for Xylene Isomer Analysis by Gas Chromatography. (2) Benner, F., Hannemann, D. E., Golding, B.,Morgan, K. A , , Xlbright, L. I?., Ofic. Ihqest Federation Sac. Paint Technal. 31, 1143 (September 1959). (3) Bevan, E. A,, Ibid., 23, 165 (March 1951). Payne, €1. F.: Ind. E q . Chem. 42, 700 (1950). (4) Rhow. N. K., ( 5 ) Crofts, .T. B., J . Appl. Chrm. 5 , 8 8 (1955). (6) Doehnert, D. F., Mageli, 0 . I,,, ‘Mod. Pla.rtics 36, 142 (February 1959). (?) Hcmpel, A. K., A m . Paint J . 38, 72 (1954). (8) Lum, F. G., Carlston, E. F., Znd. Eng. Chem. 44, 1595 (1952). (9) Martens, C!. R.,“Alkyd Resins,” pp. 105-15, lieinhold, New York, 1961. (10) Payne, H . F., “Organic Coating Technology,” Vol. I, pp. 304-1 I , LViley, London, 1954.
RECEIVF.D for re\iew March 9, 1964 ACCEPTED J u n e 29, 1964
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