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April 1955
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
85
temperature, the solubility was determined by contacting a
known volume of gas with a known volume of liquid. Th e es-
sential parts of the a pparatus are a gas buret for determining th e
volume
of
acetylene before and after absorption and a n absorption
flask for contacting th e acetylene with t he solvent.
In operation, t he entire system from the gas buret to the ab-
sorption flask is first swept free of air with acetylene. After the
system has been purged, th e pressure of the acetylene remaining
is brought to atmospheric pressure by adjusting the mercury
level in the gas buret. A reading of the gas buret is taken, and
a
known amount of solvent is introduced through
a
specially
designed funnel on the absorption flask. Th e solvent is then
cooled in an ice bath a nd stirred with a magnetic stirrer until no
more acetylene dissolves. Th e ice ba th is removed and allowed
to warm to room temperature, under constant stirring, until
equilibrium is established.
A
new reading on the gas buret is
take n with t he acetylene a t atmospheric pressure.
Table I11 shows the “normalized” experimental solubility of
acetylene in a number of solvents compared to the calculated
solubility.
,
LITERATURE CITED
(1) E. I. du Pont de Nemours
&
Co., Wilmington 98, Del., Grasse
(2)
Gilman, H. , “Organic Chemistry,” pp. 1844, 1847, Wiley, Ne
Chemicals Dept.,
product
information bull. (Feb. 2, 1951).
York. 1943.
(3) Hildebrand, J. E., “Solubility
of
Non-Electrolytes,” 2nd ed., p
(4) Huemer, H. , Library
of
Congress, Washington 25, D. C., Micro
(5) Levine, M., and Isham, R. AI . , U.
S.
Patent 2,623,611, 1953.
(6) Xieuwland, J . A., and Vogt, R. R., “Chemistry of Acetylene
(7) Ibid. pp. 154, 182.
(8) Pauling,
L.,
“Nature
of
the Chemical
Bond,” p. 64,
Corne
(9)
I b id . , pp.
154,
182.
104, Reinhold, New York, 1936.
film Reel PB 73508,
p.
7274, 1942.
p.
30, Reinhold, New
York,
1945.
University Press, Ithaca , N.
Y.,
1939.
(10)
Zellhoefer, G. F., and Copley,RI. J., J . Am Chem Soc., 60,
134
RECEIVEDor review Jun e 7, 1964. ACCEPTED ovember
12,
195
Division of Petroleum Chemistry, 125th Meeting, ACS, Kansas City, M o
1954.
(1938).
Plasticization of Polyvinyl
Chloride
with
Alky l
Esters
of Pinic
Acid
R .
F. CONYNE
AND
E.
A . Y E H L E
Rohm Haas Co., Philadelphia 37 Pa.
PlNlC
ACID
ESTERS
. . ave interesting plasticizing prop
.
.
.
may be useful secondary plasti
cizers
i f
they become commer
cially available
at
moderate cost
erties
HE large and growing usage
of
the esters of phthalic,
T
dipic, azelaic, and sebacic acids as plasticizers for poly-
vinyl chloride leads to an understandable interest in t he adapt-
ability of othe r dibasic acids as raw materials for the preparation
of simila r esters.
Such a raw material is pinic acid, prepared by th e oxidation of
a-pinene 3 )
cy
w
CH3 CH3
2 Steps
EVALUATION
METHODS
These esters were evaluated as plasticizers for polyviny
chloride in t he following formulation:
Polyvinyl chloride (Geon
101a)
60.0
Plasticizer 40.0
.
Tribasic lead sulfate (Tribaseb) 1. 0
Stearic acid 0 . 5
a
B. F.
Goodrich Chemical Co.
b
Xational Lead
Co.
The dry ingredients were blended;
the plasticizer was adde
to the dr y blend; and th e whole was thoroughly blended a
room temperature and charged immediately to a
6
X
12 inc
rubber mill operating
at a
rpll surface temperature of 325” F
The batch was mixed for 5 minutes after reaching the state
o
qualitative homogeneity which indicates that plasticizer an
resin ar e “fluxed.” At this point, th e batch was removed fro
the rolls in three portions:
Sheet, 0.100-inch th ick , subsequentl y molded (20 minute
at 323’ F.) t o yield 6 X 6
X
0.072 inch test panels
Sheet, 0.070 inch thick , for hea t stability tes ts
Film, 0.010 inch thick, fo r permanence testing
1.
2.
3.
Modulus in tension ( l o o ) , Shore A hardness, and low-tem
perature flexibility measurements were made on the 0,072-inc
molded panels. Th e lorn temperature flexibility tests used in
cluded determi nation of torsional modulus as a function
of
tem
perature (ASTM D-1043-49T) 1) nd determination of britt
point by
a
modification
of
ASTM D746-44T
2 ) .
Th e modifica
tion consisted of using tes t specimens that had been conditione
for 24 hours a t 5” C. immediately prior to testing.
Hea t stability was measured as the number o
/ \
\g/
0 CH,
~ 0 - c - c ~ CH-CH~-C-OH
hours
of
exposure a t 350” F. necessary to caus
the first abrupt discoloration of test samples cu
from the 70-mil te st shee t. Samp les of IO-mil film
were exposed in a Fade-0-Meter. The minimum
number of hours exposure required t o cause th e sample to crac
when folded sharply on itself was tak en as an index of ligh t sta
bility of t he film.
I1
H&
ck,
I
\ /
The alkyl esters
of
pinic acid listed in Tab le
I
were prepared and
characterized by th e Kava1 Stores Research Division of th e
U
S.
Depa rtme nt of Agriculture, Olustee, Fla.
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a54
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
Vol. 47 No. 4
In determining volatility,
a
tightly capped 16-ounce wide-
mout hed jar /containing a )
a
120-cc. layer of e/Ih-mesh Columbia
activated carbon, Grade AC; b ) a weighed 2
X 2 X
0.010 inch
specimen;
c )
a second 120-cc. layer of carbon;
d )
another test
specimen from the same film; and e ) a thi rd 120-cc. layer of t he
activated carbon was placed in an oven operating
at
90 C. for
24
hours. At th e end of th is time the jar was cooled in air for
15
minutes a t 25
C.,
the specimens were removed and brushed
free of carbon particles, an d th e loss in weight observed on re-
weighing was recorded as the volatility .
Table 1. Properties
of
Esters
Boiling Point
olecular
Weight
(Theory) n? C. M m . H g
_ .
Di-n-decyl pinate
In determining extraction losses, 3 X
3 X
0.010 inch samples
of film were immersed a ) in tap water for
10
days
at
room tem-
perature; b ) in refined mineral oil (Atreol
No. 9,
Atlantic
Refining
Co.)
for
10
days
at
room temperature; c ) in 1 solu-
tion of Ivor y soap in ta p wate r for 24 hours
at
60
C.; and
d )
in nonleaded gasoline for
1
hour at 25
C .
After immersion,
the test samples used in the soap solution and gasoline extrac-
tion tests were heated for 45 minutes a t 85' C. in
a
specially
designed volatility oven 4 ) . All samples were conditioned for
16
to
24
hours
at
25 C. and 50% relative humid ity before re-
weighing,
Compatibility comparisons were based on qualitative observa-
tion s of 0.072-inch molded panels a nd 0.010-inch film after various
periods of natu ral aging. Th e development of exudation during
accelerated light exposure was also observed. These observations
were supplemented b y quanti tative measurements of the amount
of plasticizer exuding from 4 X 4 X
0.010
inch film when placed
between two sheet s of showcard stock (Concoratex, Container
Corp. of America) and subject ed to a pressure
of
0.4 pound per
square inch for 7 days a t room temperature.
811 volatili ty, extraction, and compatibili ty values (Tabl e 11)
are th e averages of duplicate determinations.
DISCUSSION OF RESULTS
As plasticizers for polyvinyl chloride, the pinic acid esters
discussed here show average plasticizing efficiency, adequat e
heat- and light-stability properties, and permanence properties
which are character ist ic of monomer ic plasticizers of simil ar
molecular weights.
Low
temperature flexibility properties are
good to excellent, but compatibility properties are rather poor
(Table 11 . Since good low tem per atu re flexibility and marginal
compatibility, respectively, appear
to
be the major advantage and
th e major limitat ion of th e pinates as plasticizers, these proper-
ties meri t more detailed consideration.
Compatibility is th e critical property th at must be considered
in evaluating the performance
of
these esters versus that of com-
mercially accepted standards. A high degree of compatibil ity,
as indicated b y freedom from exudation, is of obvious importance
per Be. It is of equally great, albeit less obvious, importance in
th e interpretat ion of t he influence of these esters on mechanical
and permanence property values.
The differential between brittle point values and
TI
alues
(torsional modulus of 135,000 pounds per square inch) tends to
increase with decreasing compatibi lity between the polyvinyl
chloride and th e plasticizing ester (Tab le 111). Thi s trend is
believed t o result from the fact t ha t th e brittle-point t est is pri-
marily
a
measure of '%oughness7'a t low temperatures while the
torsional-modulus te st is a measure of softness. Th us with
polyvinyl chloride, t he less compatible e sters of pinic acid yield
two-phase or incipient two-phase compositions
at
low tempera-
tures, and, quite understandably, these compositions show rela-
tively poorer resistance to low temperatur e fracture
at
high rates
of loading (brittle point) tha n t o deformation a t low rates of
loading Tp).
Whether the low temperature flex contribution
of
the higher
alkyl pinates is better indicated by bri ttle point
or
by Tf s a moot
question since these pinates would appear to be disqualified for
use as sole plasticizers by their poor compatibility. Of greater
practical significance is the low temperature flex contribution of
pinic acid esters such as the octyldecyl pinate when used as sec-
onda ry plasticizers in more compatible compositions. Her e th e
low temperature performance
of
octyldecyl pinate
is
better
predicted by the
T ,
value contributed by th e pinate when used as
the
sole
plasticizer than by t he corresponding brittl e point.
Similar considerations indicate t he supe riority of modulus at
100% elongation over Shore A hardness as a n index of the plasti-
cizing efficiency of t he plasticizer (Table IV).
Mechanical properties
100 Modulus, lb./ sq. inch
Shore
A
hardness
Brittle point, C.
Torsional modulus
Tf),
C.
Table 11.
Properties
of
Alkyl Pinate Plasticized Polyvinyl Chloride
Alkyl Pinate with
Dioctyl Phthalateb
Alkyl Pinate as Sole Plasticizera (1: 1 Pinate-DOP) Controls
Di-n- Di-(butoxy- Di-n- Di(2-ethyl-
Octyl-
Octyl- Di-n-
Dioctylb DioctylC
hexyl ethy l) octyl hexyl)
decyl decyl decyl phthalate sebacat e
1110
1190
1300 1300
1310 1220 1280 1190 1020
65
66
72 70 78 69
70 68 66
- 4
- 7 -48 - 0 6
2 -43
-31
-
2
- 5 0 . 5 - 4 6 . 0 - 5 8 . 0 - 4 6 . 5 5 - 4 7 . 5 - 4 6 . 5 - 3 3 . 5 - 6 8 . 5
Permanence properties
Volatility
loss
2 0 . 4 1 2 . 1
4 . 7 7 . 4
6 . 1 4 . 5 4 . 3 8 . 4 4 . 1
Wat er ext'raction loss
0 . 4 2 . 3 0 . 5
0.1
0 . 3 0 . 0 4
0 . 0 5
0 . 0 2
0 . 0 4
Oil extraction
'
loss
2 3 . 7 2 0 . 7 1 4 . 7
16.9 10.1
2 0 . 5 1 8 . 1 1 3 . 2 1 7 . 5
soapy water Lxtraction
loss
1 4 . 2 2 3 . 4 3 . 4 1.9
2 . 3 0 . 7
0 . 7
2 . 0 + 0 . 4
Gasoline extracti on, loss 2 7 . 2 2 6 . 4 3 0 . 7 3 0 . 2
3 2 . 8 3 0 . 1
30
9
2 6 . 1 3 2 . 0
Stabili ty properties
Heat stability, hr. at
350
F.
Light stability, Fade-0-Meter hr.
3-4 1 x 4 3
3
252 252 323 2 52
Compatibility properties
Exudation after 1 day/rm . temp. Slight
Slight
Definite Slight Definite None Slight None Slight
Exudation after
1
month/r m. temp. Slight to Bad Bad Definite Bad Slight to Definite Kone Definite
Exudation after
41
Fade-0 -Meter hr. Slight
Definite
Definite
Slight Definite
Slight Slight None Slight
Quantit ative exudation test, loss 1 . 6 1.9
3 . 4 2 . 2
4 . 3 0.9
1 . 4 0 . 1 3 . 1
definite definite
Di-n-decyl pinate incompatible on mill.
b Flexol DOP, Carbide and Carbon Chemical Co.
C Monoplex DOS, Rohm
&
Haas
Co.
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April 1955 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
Table 111.
Low Temperature Flexibility and Plasticizing
Efficiency Related
to
Compatibility
(Alkyl pinate esters)
Octyl- Di-n - Di(2-et hyl- Di-butox y- Di-n-
dedyl
octyl hexyl) ethyl hexyl
Britile point, ‘C. -46 -48 -40 -47 -54
C . -65
-58 -46 .5 -46 -50 .5
;
brittle point - 9 - 0 - 0 . 5
+ I
f 3 . 5
Quantitative exuda-
tion test, ’X loss 4 . 3 3 . 4 2 . 2 1 . 9 1 . 6
Shore A hardness 78 72 70 66 65
Modulus
(lOO~o),
lb./sq. inch 1310 1300 1300
1190
1110
Table IV. Predicted versus Observed Behavior in Poly-
vinyl Chloride of 1: Octyldecyl Pinate-Dioctyl Phthalate
Octyldecyl Calcd. 1 :
1
Octyldecyl
Pinate DOP Mean Pinate-DOP
Britile point,
’
. 6 -31 -38 .5 -42
-
5 - 3 3 . 5 - 4 9 . 3 - 4 7 . 5
gkore? hardness 78 68 73 69
Modulus
( l o o ) ,
lb./sq. inch
1310 1190 1250 1220
Gross
differences in plasticizer permanence properties are in
accord with expectations-Le., a ) increased volatility with
decreasing molecular weight and with branching in the alkyl
group;
6)
increased water and soapy water sensitivity with
decreasing molecular weight and with the presence
of
an ether
linkage in t he alkyl group;
c)
increased gasoline extraction with
increaeing length of the alkyl group and decreased gasoline ex-
traction as a result of the presence
of
an et her linkage in the alkyl
group.
The observed apparent decrease in oil extraction with increas-
ing chain length of the alkyl group is probably caused by a ) a
tendency toward higher oil absorption by the films plasticiz
with th e higher alkyl pinates and 6 ) compensation for the pr
able inherently greater oil sensitivity
of
th e higher alkyl pina
by their lower rate s of diffusion.
Minor deviations from t he predic table order of influence of t
series
of
pinates on permanence properties can be interpreted
terms
of
th e extent of deviation from complete compatibil
Thus, t he abnormally high volatility an d soapy water extract
losses of th e octyldecyl pina te plasticized films are undoubte
composites of loss to t he indica ted haza rd plus loss throug h e
dation. This likelihood is borne out by the fact th at both
volatility and soapy water extraction values shown by
octyldecyl pinate-dioctyl phth alat e are much lower than
corresponding values
for
each of these two esters when pres
as th e sole plasticizer.
CONCLUSION
The permanence, stability, and low tempe rature propertie
th e n-octyl, octyldecyl, and 2-ethylhexyl diesters of pinic a
make these esters useful secondary plasticizers for polyvi
chloride. Pinic acid diesters derived from lower alcohols
excessively volati le while th e di-n-decyl ester is for most appl
tions inadequately compatible as
a
secondary plasticizer.
LITERATURE
CITED
(1) A.S.T.M.
Standards,
1949,
Part 6, p. 546.
(2)
Ibid.
p. 574
(3) Murphy, C. hl., O’Rear,
J.
G.,
and Zisman, W. A , , IND.
(4)Rider,
D.
K., and Sumner,
J.
K.,
IND. NG. HEiw., AN.~L
C H E M . ,5,
119 (1953).
17 730
(1945).
RECEIVEDor review August 20, 1954.
ACCEPTEDovernber
19, 1
Terpene-Derived Plasticizers
PREPARATI ON
O F
P I N I C A C ID A N D I T S E S T E R S
VIRGINIA ‘I.OEBLICH
Naval Stores Research St ati on, Ol ustee , Flu.
FRANK C. MAGNE
AND
ROBERT R M O D
South ern Regional Research Laboratory, New Orleans, La.
P’ THE
past few years the re has been increasing demand
for a
omestic supp ly of dibasic acids, such as sebacic acid, tha t
could be used in the preparation of synthetic lubricant s, low
tem pera tur e plasticizers, polymers, resins, an d fibers.
a-Pinene, t he main constituent of turpentine, will, by stepwise
oxidation, yield a series
of
dibasic acids; three
of
these are struc-
turall y identified as shown in Figure
1.
The st ructura l similarity
of these acids t o th e more common dicarboxylic acids suggests
the ir potentia l application in th e synthesis of plasticizers and low
temperature lubricants.
While the presence
of
cyclic groups, such as phenyl
or
cyclo-
hexyl, in diesters is generally considered unfavorable to the ir per-
formance as satisfactory low temperature lubricants by virtue
of th e large tempe ra ture coefficients of viscosity, high freezing
temperature,
or
pour points imparted, Murphy, O’Rear, and Zis-
man 6 )have shown th at the presence
of
the cyclobutane ring in
the pink acid
(I)
diesters does not cause such adverse effects.
Therefore, t he es ters of pinic acid should be potential ly good low
tem pera tur e plasticizers and those of sym-homopinic acid 11)
should be be tter ones because of th e more centered position
of
the
cyclobutane ring. Although severa l isomers of each acid (I
are indicated from st ruct ura l considerations, this stud y co
only esters of w hat is reported as th e d-trans isomer of pinic
and symhomo pinic acids 2,9) .
The octyl
P-(hydroxyisopropy1)pimelate
y-lactone 111) S),
th e other hand, with its oxygen-containing ring was hoped to h
an enhanced compatibility as well as the middle-range low t
pera tur e characteristics of an alkyl ester somewhere betwee
phthalate and a n adipate.
VINYL PLASTICIZERS
b sed
o n
d o m e s t i t u r p e n t i n e
co ns t i t uen ts
. . .are promising plasticizers for pol y
vinyl chloride and
PVC PVA
co
polymers
. . n some cases rival sebacic acid
esters in physical properties and
perf orma nce
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