Styrenated Esters of BisphenolEpichlorohydrin Condensates ROY W.TESS, ROBERT H. JAKOB, AND THEODORE F. RR4DLEY Shell D e v e l o p m e n t Co., Emeryville, Culif.
T
HE so-called styrrnated drying oils and styrenated oil-
modified alkyd resins are among the recent additions to the commercially available materials useful for the production of surface coatings (16). Styrenated products are formed by subjecting mixtures of styrene and drying oils ( 7 , 12, 1 3 ) or their derivatives to conditions conducive to the formation of vinyl-type polymers. These conditions include the use of peroxides ( 7 , IS), ionic-type catalysts such ax boron trifluoride (1O), and heat without added catalyst (12). In the production of styrenated alkyd resinr, the styrene may be intwporated a t various stages in the production of the resinei.e., the stryene may be combined with fatty acids (Z), monoglyc.eride&( 6 ) )or the alkyd resin itself (18). Styrene also has been polymerized with tall oil (3) and with methyl esters of drying oil acids (8). Mixtures of anietliylstyrene and styrene have been ueed widely in polymeriaations with drying oils and derivatives (6, 19). Numerous investigators have expressed opinions concerning the cheniical nature of the products. Some evidence has led to the bcllirf that the styrenated oils and related styrenated products contain styrene chemically bound with oil (1, 11, 18, 1 9 ) ) while other evidence has led to the roncluuion that they are essentially o r wholly solutions of polystyrene in an oil medium (4, 8, 27). Many of the differences of opinion on mechanism of styrenation :tnd structure of the products may be the result of widely differing
polymerization techniques and raw materials. Regardless of the true chemical nature of the products, they have been found to bc, valuable surface coating materials. FILM-FORMING PROPERTIES OF STYRENATED ESTERS Ob BISPHENOL-EPICHLOROHYDRIN CONDENSATES
Of the commercially available styrenated drying oil derivatives, the styrenated alkyds appear to be the most widely accepted. Their success has been achieved mainly because of their rapid drying rate and good hardness. Moreover, compared to the alkyd resins from which they are derived, they have improved soap and chemical resistanre. On the other hand, the styrenateti alkyds are deficient in mar or scratch resistance, flexibility, durability, and hydrocarbon resistance for many applications in aiidried and baked finishes. There has been developed a new type of styrenated drying oil derivative that retains the desirable drying rate and hardness of the styrenated alkyds and, moreover, overcomes many of the deficiencies of them materiah. These new styrenated products are made by polymerizing Ptyrcne with drying oil esters of resinous bisphenol-epichlorohydrin condensates (9) which are marketed commercially as the Epon' resiris made by Shell Chemical Corp Some similar styrenated producbts have been described by the present authors (20) and hy 3lcn':thb and Puync (16). The Epon
Figure 1. Clear Styrenated Coatings on Wood Exposed for 1 Year at 45" Angle Facing South, Oakland, Calif. a = Styrenated soybean-dehydrated castor ester of Rpon 1004 b = Commercial stjrenated alkyd resin C
385
e = Commercial bt,renated alkyd resin A d = Commercial styrenated alkyd resin B
INDUSTRIAL AND ENGINEERING CHEMISTRY
386
TABLE I.
CLE.4R
FILMT'ROPERTIES
OF
STYRENATED
Btyrenated Soybean-Dehydrated Castor Ester of Epon 1004 33
Coating Desciiption Styrene content on solids, % Adid S o . on solihs, m g . KOR/g Properties of solution Viscosity, Gardner Nonvolatile, % Color, Gardner Solvent
Styrenated Linseed Ester of Epon 1004 33 6.2
5.8
E-F
io
E P O N E S T E R S AXD Sl'YREX kTF.1) .&I.KYD
E-F $0.2
4
a
Driers added for testing. Amt. and type, on solids (Co), "b Contact time before testing, week Drying time, 1 mil d r y films, min. Set touch Dried hard
Xylene
Xylene
0.03
0.03 1
I
OH
CH3 CH,
OOH,CHO~~,~,I-O-C)--~-~--OCH,CH--CH:
0
/\
CHa Uost of the work described here was performed using a condensate called Epon 1004, which on the aveiage has molecular weight of 1400, a combining weight (with acids) of 174, and eight hydroxyl or potential hydroxyl groups per molecule: this potential hydroxyl content is comprised of about 1.47 epoxy groups and 5 1 hydroxyl groups per molecule. The Epon resin was esterified by linseed acids and also by a mixture of soybean (80%) and dehydrated castor (20%) acids; these products were styrenated in xylene solution a i t h the aid of di-te, t-butyl peroxide. Although various quantities of styrene vc.ere incorporated with these esters, detailed film propertiee were carried out mainly on final st) renated esters containing one third styrene. Comparisons were made to commercial styrenated alkyd resins, at least two of which contained approximately the same quantity of styrene as the styrenated Epon esters. -4s shown by the film data in Table I, drying rates of the styrenated Epon ester films a ere aimilai to the rapid drying rates of the styrenated alkyds of comparable styrene content. One styrenated alkyd which dried more rapidly had a greater styrene
content. Actually, styrenated Epon esters containing more styiene (up to 50%) were found to possess drying rates t.ucwxiing: that of all commercial styrenated alkyds tested. The s t y mated Epon esters also are similar to the styrenated alkyds in water resistance and approximate or exceed the hardness of thc latter. One of the major deficiencies of the styrenated alkyd-. -poor mar reaistance-was overcome to a considerable degree by the styrenated Epon esters, and in this regard the linseed eiltei was superior to the soybean-dehydrated castor ester. The styrenated Epon esters had excellent alkali resistance and in this pioperty excelled the styrenated alkyds by a wide margin. Whereas the styrenated alkyds were attacked b y 3% sodium hydroxide nithin 10 to 30 minutes, the styrenated Epon esters ere not affected until after 3 hours to several days immersion. The flexibility of the styrenated Epon esters was good as shown by the ability to be bent without rupture around a one-eighth inch mandrel; the styrenated alkyds failed in this test. Only when the styrene content oi the Epon esters was raised substantially above 33% did the coatings fail in the mandiel test. When clear coatings on wood were exposed outdoors at an angle of 45" facing south in Oakland, Calif., the styrenated soybeandehydrated castor esters of Epon 1004 showed remarkably good durability. After 1 year of exposure there was only a very slight failure due to cracking. Three commercial styrenated alkyde had failed badly after a similar exposure. A photograph of sections of the exposed panels is reproduced in Figure 1 The styrenated linseed ester of Epon 1004 was inferior to the styrenated soybean-dehydrated castor ester; it failed at about the same rate as the best of the styrenated alkyds shown in the photograph. The styrenated linseed ester of Epon 1004, containing 33% styrene, also was evaluated in red and yellow drum enamels and compared to similar pigmented coatings made from the two commercial styrenated alkyd resins (shown in Table I ) containing about the same quantity of styrene. The styrenated Epon,
INDUSTRIAL AND ENGINEERING CHEMISTRY
February 1954
linseed ester dried more rapidly than the styrenated alkyd coatings and possessed satisfactory water resistance and impact resistance. Moreover, the styrenated Epon ester was superior to the styrenated alkyds in abrasion resistance and alkali resistance. One deficiency of the styrenated alkyds is their poor hydrocarbon solvent resistance; unfortunately, the styrenated Epon linseed ester was no better than the styrenated alkyds in solvent resistance when tested in drum paints. This means that recoating of films, if desired, should be performed with care. In clear coatings described earlier, no difficulty with recoating was experienced. Outdoor durability test of the red and yellow drum enamels were carried out by applying one spray coat on hot rolled steel using no primer. Tests have been in progress for one year; a t this time both the styrenated Epon linseed ester and the commercial styrenated alkyds were in sound condition and suffered from no checking or cracking; in all cases chalking was very slight and dirt retention was slight. Deep scratches placed on each panel before exposure showed good resistance to growth and were a maximum of one eighth inch wide after one year. I n addition to the 1004 grade of Epon resin, two other grades of Epon resin were used in the formulation of styrenated linseed esters. -4higher molecular weight grade (Epon 1007, MW 2900) gave a product, containing one third styrene, which had good film properties but possessed excessive viscosity and poor can stability. A lower molecular weight grade (Epon 864, MW 710) was converted to a styrenated linseed ester having one third styrene content. This product was slightly softer and dried a little more slowly than the conventional styrenated Epon ester but had good durability and flexibility. METHODS OF PREPARATION
Source
Material
Epon resins 1004,864, 1007
Shell Chemical Corp. Linseed fatty acids, water-white grade Archer-Daniels-Midland Dehydrated castor acids Wohurn Chemical Corp. Isoline Baker Castor Oil Co. 911 Acids Wohurn Chemical Corp. Soybean fatty acids Koppers Co. Styrene Dow Chemical Co. Vinyltoluene Shell Chemical Corp. Di-tert-butyl peroxide PREPARlTION O F
ESTERSO F
EPOii
RESIX. Esters of Euon
resin can be made from fatty acids of any type, but for this work only the linseed and mixed soybean-dehydrated castor (80-20) esters were used. Soybean esters of Epon 1004 yielded slightly cloudy films when styrenated; however, this investigation has indicated promising means of overcoming this slight nonhomogeneity, as by use of larger quantities of peroxide catalyst. The esters utilized in the styrenations were made from 45 to 50% Epon and 55 to 50% fatty acid. Esters were made either by the solvent method which utilized refluxing xylene or other hydrocarbon or by the fusion method which utilized a rapid stream of nitrogen to facilitate removal of water. I n the solvent method, the reaction was carried out in a borosilicate glass flask equipped with stainless steel stirrer, thermometer well, nitrogen bubbler and a phase separating condenser. Epon, fatty acid, and a smali quantity of xylene were heated to 250" C. in 1 to 4 hours and held a t that temperature until an acid number of about 10 mg. of potassium hydroxide per gram was reached. It, is important that prolonged cooking time or very high viscosities of esters be avoided, because these factors tend to promote the attainment of excessively high viscosity (or in the extreme case, possible gelation) of the final styrenated products. The esters were thinned with xylene to about 50 to 75y0 solids and filtered with the aid of Super-cel prior t o styrenation. I n the fusion method of esterification, similar equipment was used except that the phase separating reflux condenser was replaced by an ordinary condenser. Temperatures of 250' to 260" C. were used in this method. Examples of both methods of preparation are shown in Table TT
IL.
STYRENATION OF EPONESTERS.Styrenation of the Epon esters was carried out in a borosilicate glass flask equipped with
387
stainless steel stirrer, reflux condenser, dropping funnel, thermometer well, and nitrogen bubbler. The Epon ester, a t a concentration of 60 to 75% in xylene, was heated to reflux temperature (145' to 150" C.). T o the ester was added fresh commercial inhibited styrene containing di-tert-butyl peroxide catalyst. Addition of styrene over a period of about 1 hour was preferred to addition of styrene all a t once. The reaction mixture was maintained under reflux conditions during and after the addition of styrene, the temperature being governed by the concentration of xylene and styrene monomer. The extent of polymerization of styrene was followed by determining the nonvolatile content (ASTM D 1 5 4 4 3 ; 1.5 grams of sample heated 3 hours at 105" C.). Heating was continued for 2 to 6 hours until the polymerization had leveled off or was complete. The product was diluted further with xylene and filtered with the aid of Super-cel. The quantity of catalyst preferred depends upon the amount of styrene, type of f a t t y acid, and other factors; for a final product containing one third styrene, a recommended amount of ditert-butyl peroxide is 1.5% based on styrene to be added with the styrene and one or two portions of 0.5% each to be added 1 to 3 hours after complete addition of styrene. Three examples of specific preparations are given in detail in Table 11.
TABLE 11.
PREPARBTIOX O F STYRENSTED ESTERS
Example No. Esterification reaction Method Reactants, grams Epon 1004 Linseed acids Soybean acids Dehydrated castor acids Temperature, C. Upheat time, hr. Time a t temp hr. Final Droduot" h'onvolatile, % Visoositv. Gardner-Holdt Viscosity Color Gardner Ga'rdner Arid Acid N o mg KOH/g., solids styrenation ;&action Styrene content, final product, 3 '% X Reactants Ester solids Styrene Xylene Di-tert-butyl peroxide, % of styrene Bdded with styrene 1 hr.
1
3
Solvent Fujion
600
5850
,..
586 147 250 4 2.23
3760 940 260 1.5 3 0
48.1
75
B
5 9.6
X-Y
7-8 12.5
Solvent
1000 1000 ,
.,
250 2.0 1.5 50 J 7 9.6
33
33
33
300 150 324
500 260 500
1955 980 665
2.0 , . .
14;-6 5.0
1.0 2.0 2.25 3.0 3.5 4.0 4.5 5.0 5 6
2
57.0 71 .O 82.4
...
86.6
...
89.1
... ...
90.7
1.0 0.5 0.5 0 5 146
2.0 ,..
... ,..
150
6.0
4.0
... ... 82.5 ... 85.5 ... 92.3 ...
... ...
64.0
... ,.. , . .
lob'iapprox.)
... ... ...
...
98.0 98.5
56.3 T'-W
59.3
60.0
6 5.8
5-6 7.8
6-7 7.0
X
...
U
EFFECT OF TEMPERATURE VARIATION UPON THE REACTION OF STYRENE WITH EPON ESTERS
An investigation was made of some of the factors that appeared to influence the rate of polymerization and final conversion of styrene in the reaction with Epon esters. The effect of the temperature of reaction was investigated qualitatively by carrying out the reaction of styrene with Epon 1004 linseedate a t two different temperatures. When Epon linseedate a t 60% concentration in xylene was employed, the temperature of reaction was 145' C., but when the ester was used a t 75% concentration in xylene, the temperature of reaction was 153' to 162' C.; the temperature in each case was determined by the reflux conditions. I n the latter case the temperature rose slowly as the styrene polymerized, but in the former case the larger quantity
INDUSTRIAL AND ENGINEERING CHEMISTRY
388
Vol. 46, No. 2
may be ascribed to some degrcc! t,o the larger percentagcs of catalyst, if i t is calculated as based on total solids or total charge. This possibility seems obviated, however, by a second study of the effect of Ptyrene concentration on rate of the styrenat>ioii react,ion. I n this second series of experiments, the rate of polymerizat,ion of styrene with Epon 1004 linmedate was followed, as showti in Table IH and Figure 4. Based 011 styrene and Epon ester solids, thv styrene concentlation was 20, 35, and 43%, and the catalyst based on stypen($ was 4,2, and 1.35%,respectively, in tfw three cases. I n this case if the catalyst is calculated as based on styrene plus ester, styrene plur c>stcr k 10 plus xylene, or on ester alone, the. quantity of catalyst remains conrtant, or berornes larger, with decrea-ing I 1 , stjrene content. Therefore, if thc ratc 1 2 3 4 5 6 Hour1 of Reaction Hoiwi k r a c l on of polymerization of styrene is greatei Figure 3. Reaction of Stsrene nith greater concentrations of styrcnc , Figure 2. Effect of Temperature with Soybean-Dehydrated Castor on Reaction of Styrene with Epon this cirrumstance cannot be attrihEster of Epon 1004 Using Various 1004 Linseedate uted to greater catalyst roncentreQuanti ties of Styrene tions, regardless of the basis of calculation. The results of this yerivs was accomplished in 4 hours a t 152" to 163" C., only 897, of the of styrenat#ion react,ions shon. that the rat'e of polymerization of styrene polymerized in the same time a t 145" C. The polystyrene increases markedly with greater concentration of styrene. merization of styrene was still proceeding at an appreciable rate Indeed, when only 20% styrene was present, the polymerizaafter 4 hours at 145' C., but experience had shown that the rate tion of styrene leveled off when only 59% had react,ed. leveled off considerably after this period. The Epon liiiseedate Properties of the styrenated 1Spon esters varied depending on used for this comparison was made from 55 p a r h of linseed acid the styrene (.ontent. With increasing styrene content films of and 45 parts of Epon 1004, and sufficient styrenc was used to the product's have more rapid drying rat'es, poorer flexibility, make a final product of one-third styrene content. The styreand lem mar resistance, while the solutions of the products arc: nated ester made at 162' to 163 C. had somewhat, limited storage greater in viwosity, poorer iii can stability, and greater i n stability and for pract,ical purposes i t was deemed preferable to clarity. limit the reaction temperature to 150' C. of xylene kept the temperature low in spite of polyiiicrization of styrene. The rate of polymerization of styrene ~i'asappreciably greater at the high temperatuyea, and what is more important,, the reaction of styrene was more complete. The course of the reactions is shown graphically in Figure 2; the time indicated is the elapsed time aft'er complete addition of st'yrenc over a period of 1 hour. Although complete polymerization of st'yrcnc
q
i t
0,
IYFLUEhCE O F CATALYST Oh S'I'YRENATIOY REACTIOW
EFFECT O F VARIATIOY IN STYREYE COYCEY'rR4TION ON REACTIOY OF STYRENE WIT11 EPON ESTERS
Some isolated experiments indicated that the rate of polymerization of styrene with Epon ebtcrs as well as the homogeneity of the product was influenced by the amount of catalyst present. A similar conclusion was reached in an investigation of t h e styrenation of an alkyd resin of the follon-ing csomposition:
The rate of polymerimtion of stj-rme with Epon esters \{as greater with larger concentrations of styrene in the reaction mixture. Compartttivc. rates r e r e followed for tlic tollowing two systems: ( 1 ) 33% -fyi'riie and 67% bo3.bean-dcliytlInted castor ester of Epon 1004 t l i ~ l ~ in e dxylene, and (2) 40% styrene iund 60% soybeail-
was employed. In spite of the fact g that more styrene (40%) JWS used in - o- h@ 0 4.05.DTBP Styrene the one case, the entire amount n-as 0 2.0% DTBP on Styrene , A 1.0% D I B P o n S I y r e n e polymerized after : h u t 4.5 hours, 0 4,% styrene, on styrene PI". hrlrr 1 0 u. 54. DTBP on styrene sr 0 >>+styrene. s1yrenc PIVS E s t e r whereas when the Icswr :tmount~ of 1 0 2 0 5 soyrene. on Slyrene Ester IO styrene (33%) was u s r d : :%bout6 hours I I I I I I 1 were required for virtually complete I 1 I 1 2 3 4 5 6 ' 1 2 3 4 5 6 Hours oi Reaction polymerization of sty1 rntl. The course H o u r s 01 Reaction Figure j. Effect of Concentration of the polymeri~ation of styrene is Figure t . Reaction of Styrene of Di-Trrt-Butyl Peroxide on Rata shown in Figure 3. In thiq comparison with Epon 1004 Linseedate Using of Styrenation of Linseed Uksd equal quantities of rtrta1y.t based on Various Quantities of Sts r e m Repi 11 styrene were used. thii of (aourse meanq that a greater pcrrciitage of catalyst 61 .OTCliii~ccdacids. 25.9TCphthalic a n h y d r i d ~20.0% , glycerol. was used in the C R W of the product containing 40% styrene if U&g no wlvent, a temperature of 145" to 150" C., styrene equal the catalyst is coii~idt~rcd as based on styrene plup ester or on styrene plus ester plur wlvent. It icl a moot point as to which to one half the weight of alkyd, and 4, 2, 1, and 0.5% di-tertbutyl peroxide, the rate of polymerization of styrene increased method is correct hut csonventionally the catslyst concwitration markedly with inrreasing catalyst concentration. as shown in has been based upon i t y r n r I n a later section it i q -hewn that the rate of styrenation increavs markedly with incrmsed cataFigure 5. Where only 0.5% peroxide was used, the resulting lyst concentration Themfore, it is possible that the accelerated styrenated alkyd gave cloudy films whereas in all other cahes rate of styrenation t l u ~to the larger concentration of styrene the filins were clear. I n this regard, Falkenburg, Hill, and D:
0~
(10
YI
1
0"
PlVS
t
INDUSTRIAL AND ENGINEERING CHEMISTRY
February 1954
'TABI'E
1x1. PREPARATION O F STYREiYATED EPONLINSEEDATE USIXGVARIOUSQTAXTITIES OF STYRENE Temperature 145' C. All catalyst added with styrene
Styrene, based on styrene plus ester, % Composition of charge Styrene, yo Epon linseedate. % Xylene. %
DTBP %
Di-teTt-bdtyl peroxide, %, calculated as based on Styrene Styrene plus ester Styrene, ester, a n d xylene Ester Styrene reacted, % Hours after addn. of styrenen 0,5 I 2 3 4
20
35
43
16.9 67.8 14 7 0.68
27.2 54.4 17 9 0.54
36.5 48.7 14.3
4 0.80 0.68 1.00
0.67
I
.
.
55
... ..,
59
2 0.55 1.00
79 85 6 90 94 99
0.49
1.35 0.57 0.49 1.00
...
97
...
'Time indicated is the elapsed time after complete addition of styrene during a period of 1 hour. By interpolation. 0
Wolii' ( 8 ) obtained clear products when alkali refined linseed oil methyl oleate (among other esters) were polymerized with styrene using 10% benzoyl peroxide based on styrene; heterogeneous products (nonvolatile films) were obtained when only 1 or .5% catalyst was used under the same conditions. The amount of catalyst is important, and a critical niininium amount appears to be necessary to obtain homogeneous products in various cases of styrenations. The mode of addition of catalyst also has been found to havr an effect on the rate of the styrenation of Epon esters. When only part of the catalyst is added with the styrenc, and the balanre added in increments, the rate of polymerization of styrene is dower a t first but eventually becomes more rapid. This is illustrated by the data in Table IV which shows the rate of styrenation of Epon 1004 linseedate by the standard technique where xylene solvent was used, a temperature of 145" C. was maintained, 2% total di-tert-butyl peroxide was used, and the weight of styrene charged was one half the weight of ester solids. 01
389
the final product, vinyltoluene, and styrene were generally similar in behavior when combined with Epon esters, as shown in Tables V and VI. The final product in each case contained one third vinyl hydrocarbon on a solids basis.
TABLEV. CO~~PARISON BETWEEX VISYLTOLUENEAND STYRENE
Ipr'
PO1,YRIERIZATION WITH SOYA-DEHYDRATED &TER O F EPoN 1004
Vinyl conatitnent Total di-terl-butyl peroxide Method of adding catalyst Vinyl compound, %, reacted after I .O hr. 2 . 0 hr. 2 . 2 5 hr. 3 . 0 hr. 3 . 6 hr. 4 . 0 hr. 4 . 5 hr. 5 . 0 hr. 5 . 5 hr. 6 . 0 hr. Prouerties of final -product Solids in xylene, % Viscosity, Gardner Color, Gardnei
CASTOR
Vinyltoluene 2 . 5 % on vinyltoluene
2 . 5Y0 on styrene
Styrene
1% with vinyltoluene; 0.5% after 1 hour; 0 . 5 % after 2 hours; 0 . 5 % after 3 hours
1 % with styrene: 0.5% after 1 hour; 0.5% after 2.5 hours: 0.5% a f t e r 3.5 hours
64.8 82.9
64.0
...
... 90.2 ...
82,s
...
85.6
95.4 ,
.
92 6
~
. .
100
...
100
98.0 98.5
58
60
$5- 6
5-6
X
Z
TABLEVI. FILM D A T A S H O W I N G CO3IPARISON BETWEEN VINYLTOLUENE AKD STYRENE IN COMBITATION WITH SOYBEANDEHYDRATED CASTOR E5TER O F IGPON 1004 Vinyl constituent
Boiling water. 15 min. Appearance Recoverv time. min. Cold water, 18 fir. Appearance Recover time, Rkcover time min. Sward harJness. i1 week Mandrel, 1/8 inch YaOH) fiist Alkali resistance (3% XaOH) first appearance of haze, days3
Yinyltoluene
Atyirne
Very slight haze 1
Very slight haze 5
Slight haze 6 20 0 IC
0 I
