Properties of Polyvinyl Chloride
Compounds EFFECT OF PHTHALATE ESTER STRUCTURE P. V. SMITH,
JR.,
R. G. NEWBERG,
AND
D. W. YOUNG
Standard Oil Development Company, Elisabeth, N . J .
A study has been made of the physical properties of the “isomeric octyl” esters of the three isomeric phthalic acids. Isomeric octyl alcohol is made commercially by the Oxo reaction. A selected mixture of seven-carbon olefins is converted to aldehydes with hydrogen and carbon monoxide under high pressures in the presence of a catalyst. The aldehydes are then hydrogenated to alcohols. The isomeric esters made from these alcohols were compounded with a copolymer of 95% vinyl chloride and 5% vinyl acetate. The plasticized resins were evaluated for tensile strength, 100% tensile stress (100% modulus), ultimate elongation, Shore hardness, Tinius Olsen (Tour-Marshall) stiffness, brittle temperature, and volume increase in standard fluids, and the effect of heat and light aging on the physical properties. The plasticized resin containing diisomeric octyl terephthalate has superior heat and light aging properties and a slightly better brittle temperature than the other two isomeric phthalate-resin compositions.
T
HE use of resins, such as copolymers of vinyl chloride, in
high pressure, in the presence of a catalyst, to form aldehydes which are then hydrogenated to alcohols. Sparks and Young (9) reported on several plasticizers derived from Oxo alcohols, such as diisomeric octyl phthalate and triisomeric octyl phosphate, and compared them with analogous commercial plasticizers. The present paper discusses the properties imparted to the esters and t o the vinyl blends thereof as obtained by esterifying the isomeric phthalic acids with commercial isomerlc octyl alcohol. The structures of these esters are:
elastomeric applications has grown t o the point where today millions of pounds of plasticizer are required per year. A wide variety of nonvolatile materials is available to vinyl technologists for such needs. The properties essential t o good performance have been discussed a t length in a number of earlier papers. Briefly, a plasticizer must meet several more or less fundamental requirements for each application for which it is to be used: compatibility, plasticizing efficiency, volatility, resistance t o migration, flammability, odor, color, electrical properties, toxicity, and resistance to heat and light. These characteristics are all properties of the plasticizer. I n many cases, the plasticizer must also impart good flexibility to the resin a t low temperatures. For a number of years, plasticizers of the ester type, such as di-2-ethylhexyl phthalate and di-n-octyl phthalate, have been widely used in vinyl resins because of the very good balance in their over-all physical properties. However, there has been a shortage of the primary Cg alcohols. To overcome this shortage the Esso Standard Oil Company recently began marketing a primary, C S alcohol, known as “iso-octyl” alcohol, which is made by the Oxo reaction. Olefins are made to react with hydrogen and rarbon monoxide under high pressure in the presence of a catalyst to form aldehydes, which are then hydrogenated to alcohols. To avoid any possible confusion with iso-octyl (6-methylheptanol), the Oxo product is referred t o &s isomeric octyl alcohol in this paper. Olefins react with hydrogen and carbon monoxide under
0 I\
COR
Carbon$l
422 1.1
NO;
Saponification No. Acid No. Specific gravity at 2Oo/2O0 C. Water content
nfi 0 0 0.835
Miscible with 19 vol. of
APHA color, Pt-Co scale Phthalate ester coIor (high temperature test), Pt-Co scale
60’ BE. naphtlia at 20’ C . 15
60
II
COR
COR
I1
0
Phthalate
TABLE I. PHYSICAL PROPERTIES O F ISOMERIC OCTYLALCOHOL Hvdroxvl No.
0
Isophthalate
Terephthalate
where R is an isomeric octyl radical. Theisomeric octyl alcohols used in this study were manufactured from C7 olefins available from refinery streams. Some physical properties of this alcohol are listed in Table I, and the A.S.T.M. distillation curve is shown in Figure 1. Knowledge of the vhemical reaction involved and some of the more readily available physical properties indirates that the isomeric octyl alcohols comprise a mixture of isomers having, on the average, two alkyl side groups along a carbon chain of four t o six carbon atoms. Although only phthalic anhydride is a t present in large scale commercial production, all the isomeric phthalic acids are potentially available by oxidation of the corresponding xylenes n hich can be wparated from refinery streams.
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I t amounted t o 340 grams of ester (87.2% of theoretical ). ISOMERIC OCTYLTEREPHTHALATE. A mixture of 203 grams (1.0 mole) of terephthalyl chloride, 286 grams (2.2 moles) of isomeric octyl alcohol, and 100 ml. of dioxane was refluxed until no more hydrogen chloride was evolved. The product was then waphed and dried as described above, and distilled to give a heart cut of 291 grams of ester boiling at 127" t o 138" C . and 4-micron pressure (74.670 theoretical). Some physical properties of the isomeric phthalates are listed in Table 11. The viscositytemperature curves for the three esters are plotted in Figure 2. The viscosity increases as
---
PHTHALATE ISOPHTHALATE
- TEREPHTHALATE -\ \
EY
\
% ' ?+ 10.
\-
-~ --
-
INDUSTRIAL AND ENGINEERING CHEMISTRY
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Vol. 42, No. 12
(JUS niii~ei,:il oil with an :tnilinc point of 255OF. (123.9"C.). Terephthalate OVENAGING. The effect of heat on the physical characteristics was deter0.987 -40 (-40' C.) 1.4893 mined by aging specimens in an oven 33.7 designed for circulation of the air. 5.65 Reproducible results were obtained by 38:40 averaging readings from multiple tests. 101.28 1170.0 The specimens were cut from molded 20,687 slabs with die C ( 2 ) . The physical 0.765 92 characteristics were determined after 286.0 aging a t 250" F. (121.1" C.) for both 401-418 3 and 7 days. The oven aging technique employed here has been describcd by Sayko and Robison (8) in detail. LIGHTAGING. For studying thc effect of light aging in ultraviolct light, 6 X 6 X 0.075 inch pressed slabs \ v e x placed in the Fade-Ometer t i t 125" F. (31.6" C.) for 150 horns.
TABLE11. PHYSICAL PROPERTIES O F DIISOMERIC OCTYLPHTHALATE ESTERS Ester Sp. gr., 6Oo/6O0 F. (15.6°/15.60 C . ) Pour point,, F. Refractive index, nZi? Surface tension, dynes/crri. Kinematic viscosity, i n centistokea A t 2100 F. (1000 C.) .kt 130' F. (54.4' C . ) A t 100' E'. (37.8' C . ) A t 68' F. ( Z O O C.) ..it 150 F. (-9.40 C.) .4t -26' F. (-31.7' C.) 4.S.T.M. slope, 100-210° F. Viscosity index daponification No., mg. KOH/r. Calcrilitted boiling point, corrected to 760nini. pressure, C .
Phthalate 0.990 -50 (-45.6' 1,4871 33.0 4.44 36:OO 79.08 935.0 17,690 0.827
Isophthalate C.)
0.987 -45 (-42.8' 1,4893 33.6 5.28 18.0 38.50 103.0
...
288.5
33
0 ,'803 65 284.2
429-437
408-423
e
*
ISOPHTHALATE
C.)
RESIJLTS O N HESIX B L E N D S
D a t a for the resin blends plasticized with three samples of isomeric octyl phthalates are listed in Table 111. The effwt of phthalate structure on the relative plasticizcr performance in vinyl resins can be determined from these data. Tensile strength data were all about the same. The structure of the phthalic acid did not alter the t,ensile strengt,h of the resin. TEMPERATURE 'C. Values for 10070 tensile stress indicate that Figure 3. Stiffness of Isomeric Phthalate Plasticizers in Resins diisomeric octyl phthalate imparts a slightly lower modulus than the esters made from either TEST METHODS terephthalic or isophthalic acid. Shore hardness and ultimate elongation data from these' tests Tensile strength, 100% tensile stress, and ultimate elongat,ion show t h a t the diisomeric oct>yl phthalates plasticize the vinyl were determined on a Scbtt tester (Model L-3) at 25" C. and 50% compounds to about the same degree of elasticity. relative humidity. The rate of jaw separation was 20 inc,hes per St,iffness indexes parallel somewhat the viscosity properties of minute. To determine elongation. the specimens were hcnch marked with a 1-inch die, the grips were adjusted to be 0.75 inch apart at zero load, and the elongation 1%-asmeasured TABLE 111. PllYSIC.41~1'ROPERTIES O F DIISOMERIC OCTYI, PHTH4LATE: PLASTICIZERS with a decimal scalc held close to the IN RESINS specimen. Composition, parts by weight Shore hardness data were obtained with Vinyl chloride-vinyl acetate co100 100 100 polymer a Shore A durometer ( 4 ) by averaging Dl!8omenc octyl phthalate 50 ... Diisomeric octyl isophthalate ... 56' ... multiple readings for each specimen. Diisomeric octyl terephthalate 50 , . Brittle temperatures were determined Basic PbC03 3 3 3 Stearic acid 1.5 1.5 1.5 with the instrument described by the Specific gravity 1.,251 1 246 1.248 Tensile strength, lb./ss. inch 3,100 2,900 3,290 American Society for Testing Materials 100% tensile stress, Ib./sq. inch 1,680 1,770 1,750 ( 5 ) . Before testing, the specimens Ultimate elongation, yo 283 346 336 Shore hardness (immediately) 90 85 85 were put in the air chamber for 25 Tinius Olsen (Tour-IbIarsliail) ,,titt'ness, lb./Rq. incli minutes to bring them t o equilibrium A t 75' F. (23.9O C . ) 1,180 2,170 1,500 .4t 35O F. (1.67O C . ) temperature. 16,720 14,200 14,050 At 10" F. (-12.2' C . ) 30,167 36,120 32,740 Stiffness index, in pounds per ,square Bell Telephone brittle teniiJri.atiirc, a t break point, F. 10 ( 2 8 . 3 0 C . ) 10 ( 2 3 . 8 0 C.) 20 ( - 2,s .90 C . ) inch, was determined for each sample Volume increase after 168 tioiiw at 75" F. (23.9' C . ) % with a Tinius Olsen (Tour-Marshall) I n A.S.T..M. fuel 1 -8.6 -5.7 +1.7 tester (6). I n A.S.T.M. fuel 2 -8.0 -7.0 -9.0 I n A.S.T.R.I. oil 1 -0.3 -0.2 -0.3 Volume increase was measured in each I n A.S.T:M. oil 3 -0,2 -0.1 +o: 1 Oven-aged3daysat25O0 E': ( 1 2 1 . I 0 C . ) of the four standard test fluids a t 7 5 O F. Tensile strength, lb./sq. 111t.h 2,930 (+1.0)" 3.030(-7.9) 3,050 ( - 1 . 6 ) 10070 tensile stress, lb/s
