I N D U S T R I A L AND E N G I N E E R I N G CHEMISTRY
488
made along the following lines: First, to evaluate the p values (6) for the liquid polymer-resin systems, and, secondly, to specify in detail the microcrystalline order of the liquid polymer plasticized polyvinyl chloride resin according to the physical methods employed in the studies of Alfrey, Wiederhorn, Stein, and Tobolsky (3). Lastly, the plasticizing action of the liquid polymers described here refers only to the systems listed in Tables I1 and 111, and the results are not in any way representative of the plasticizing action of the various other polymeric-type plasticizers produced by industry. ACKNOWLEDGMENT
The authors wish to exDress their a~ureciatlon to Turner
(1) Biken, Alfrey, Janssen, and XIa,rk, J . Polymer Sei., 2, 178 (1.947). (2) Alfrey and Harrison, J . Am. Chem. Soc., 68, 299 (1946). (3) Alfrey, Wiederhorn, Stein, and Tobolsky, IND. ENG.CHEM.,41, 701 (1949). (4) Bartlett a n d Altschul, J . Am. Chem. SOC.,67, 812, 816 (1948). (5) Boyer and Spencer, J . Polglmer Sci., 2 157 (1947). (6) Eugene, Moffet, and Smith (to Pittsburgh Plate Glass Co.), U. S.P a t e n t 2,356.873 (August 1944). (7) Fligor and Sumner, IXD. ENG.CHEM.,37, 504 (1945). (8) Flory, J. Am. Chem. Soc., 59, 241 (1937). (9) Young, Newberry, and Howlett, IND.ENG.CHmf., 39, 1448 (1947). RECEIVED October 28. 1949. Presented before Division of Paint, Varnish.
-
physical test measurements.
Vol. 42, No. 3
LITERATURE CP1‘EI)
-
nients for the degree of doctor iif philosophy.
(Creep Behavior of Plasticized Polyvinyl Chloride)
DIPHOSPHATE ESTER PLASTICIZERS RICHARD H. OLIVER, NORMAN M. WIEDERHORN’, AND ROBERT €3. MESROBIAN Polytechnic Institute of Brooklyn, Brooklyn, !V. Y Studies on the creep behavior of vinyl chloride resin plasticized with new derivatives of phosphate esters are reported. The most satisfactory method of preparation 0
//
of a series of phosphate esters of the type ( R 0 ) r P 0
//
This compound type may be considered to represent a polymeric condensation product of a phosphate ester, delimited to a degree of polymerization of two. Practical interest in these compounds arises from their potentialities as low temperature plasticizers comparable with TOP and possessing, because of their dimeric structure, oil extractability, volatile loss, and other related properties that are superior to TOP.
O-(CH~),-O-P-(OR)2
was found to be reaction of stoichiometric quantities of mono- and dihydric alcohols with phosphorus oxychloride. The plasticizing efficiency of the diphosphate esters, compared by tensile creep with commercially used plasticizers, is quite satisfactory over a wide temperature range.
A””““
PREPARATZOh OF DIPHOSPHATE ESTERS
Preparation of n-decamethylenebis(o,o-dibutyl phosphate) was first attempted in the following way:
3C4HoOH
+ PCl,
-0 ” C.
/o”
P
\
+ C4HgCI + 2HCl
(1)
(OC4HQ)Z L G the widely used plasticizers for vinyl resins are the two organic ester derivatives of phosphoric acid, tricresyl P phosphate (TCP) and trioctyl phosphate (TOP). Both of these Clr 0 ° C . O=P HCI (2) materials have specific advantages and disadvantages which I_j \ govern their applicability t o practical use. Aside from cost >oC4&):: (OCa&)s factors, TOP has the distinct advantage C~HQO OC&Q of possessing superior low temperature C’1 / / \ properties to TCP and Other 20=P HO(CH,)loOH Pyridine O=P-O-(CH~)IO-O-P=O 2HC”l (3) olasticizers (1. 6). On the other hand, \ \ / S41& Od4& TOP suffers the disadvantageof high oil exiOCaHp)n tractability. Several authors ( I , 8) have The dibutyl hydrogen phosphite formed in Equation 1 is eommented on the relation between low temperature flexibility of converted to dibutyl chlorophosphonate by reaction with chlorine plasticized vinyl chloride films and oil extractability of plasticizers. gas at ice temperature. The experimental details for the prepaIn continuing the studies on polymeric plasticizers for vinyl ration of compounds similar to the phosphite and chlorochloride resins ( 3 ) , the authors have attempted to prepare a phosphonate intermediates have been reported (4, 6). The series of phosphate esters of the type given below: final reaction product is obtained by condenmtion of 2 moles of RO dibutyl chlorophosphonate with 1 mole of decamethylene glycol \ (Equation 3). Pyridine is used to remove liberated hydrogen O=P-O-(CH2)n-O-P=O (A) \ chloride. The yield by this method of preparation was low / OR RO (50%) and considerable difficulty was always encountered in the purification of the reaction intermediates and the final product. where n = 4,6,or 10, and R = CIHp-, C~HU-, or CaHIT-. Phosphite derivatives have been noted to be unstable inter1 Present address, United Shoe Machinery Corporation, Beverly, Mass.
/””
+
/””
+
--
7’
+
+
INDUSTRIAL AND ENGINEERING CHEMISTRY
March 1950
mediates that decompose readily with the liberation of phosphine during vacuum distillation a t elevated temperatures (6). In order to effect a more satisfactory preparation of the diphosphate esters, the following procedure was used:
~
The glycol was first added to phosphorus oxychloride in a molar ratio of 1 : 2. After complete reaction, sufficient rLonohydricalcohol was added to react with all the remaining chlorine functional groups of the decamethylenebis(dich1orophosphonate). By this simple procedure, the expected diphosphate esters are formed in two steps re uiring purification in the last step on&. The final product obtained in this manner is most likely a mixture of the desired product and small amounts of mono-, tri-, and higher order phosphate ester derivatives.
489
TABLEI. PROPERTIES OF DIPHOSPHATE ESTERPLASTICIZERS
Code Name
Compound n = R = n = R =
10
R
n-ChHg-
Butadec
n--C6H,a-
Hexadeo
o0
n-CdH9-
Octadec Butahex
0 78
Hexahex
0 60
10
n = 10 nR = = 6nCnH1i=
n = 6
R = n-CrH17n = 6 R = t-CsH17-
a
ConsistencyG
32 3J~
811
Compatible
7811
Caprahex
n = 4 R = n-GH9n = 4 R = Z-C8H17
.
0 0 // // (RO)aP-O(CH&O-P(OR)z Free Hydroxyl Com atibility Content, wit{ ~7lnyi Chloride %G OH/G (Geon 101) Product Resin
...
"
..
..
Molecular Weight Calcd as pure Experidimer mental
Flows
558
516
Flows
670
778
Viscous
782
980
Flows
502
620
Flows
614
691
Flows
726
913
...
...
Incompatible
1
...
Flows
Room temperature
The glycol was added to the phosphorus oxychloride before the monohydric alcohol to establish first the diphosphate linkage. The apparent tendency for the first chlorine in phosphorus oxychloride to react more readily than the two chlorines in, the monosubstituted derivative ( 7 ) facilitates the formation of the glycol ester bridge. I t has been reported by Gerrard ( 7 ) that the dropwise addition of 1 mole of butyl alcohol to 1.45 moles of phosphorus oxychloride yields 80% of the monosubstituted (POC120Bu) product. Statistically it may be calculated that the yields under these conditions should be 45.8% unsubstituted, 40.8% monosubstituted, and 13.4% di- and trisubstituted products, assuming the chlorine groups of the various derivatives to be of equal reactivity. In view of the high yield (80%) of monosubstituted product found experimentally, it might be assumed that the reactivities of the remaining chlorine functional groups progressively decrease with substitution. In these studies, no attempts were made to purify the final product from the point of view of removing phosphate esters other than the dimer. The extent of completion of the condensation reaction was estimated by determination of the free hydroxyl
content of the final product. Since the condensation reactions can be driven to near completion, the yield of the final product by this method of preparation is most sahisfactory. EXPERIMENTAL
The eight diphosphate esters listed in Table I were prepared for evaluation as plasticizers by the method which follows. 7.2
1
7 -
6.0
4.8
2
3.6
\
2.4
1.2
1
10
100
1000
10000
Time, Seconds 7.2
Figure 2.
Comparison of Plasticizers by Tensile Creep 30' C.; 45% plasticizer
6.0
.B ,? Y
'4.8
\
3.6
2.4
I
I
1
10
.
,
.
,
,
.,I
100
1
1000
,
.
.
..J
10000
1
Time, Seconds
Figure 1. Comparison of Plasticizers by Tensile Creep 50" C.; 45% plasticizer
10
100
1000
10000
Time, Seconds
Figure 3.
Comparison of Plasticizers by Tensile Creep 10' C.; 45% plasticizer
INDUSTRIAL A N D ENGINEERING CHEMISTRY
490
1
10
Figure 4.
100 Time, Seconds
1000
10000
Comparison of Plasticizers by Tensile Creep -20' C.; 45% plasticizer
Vol. 42, No. 3
tions ( 1 ) . The effect of temperature on creep for the systems studied is more readily apparent from the curves of Figures 5 and 8, where the compliances after 10 seconds and after 1000 seconds are plotted as functions of temperature. The excellent temperature characteristics of TOP and the diphosphates as compared to TCP are evidenced by the greater slope of the TCP curves. Creep studies have also been made on films containing 25% plasticizer. Since the same trends of behavior were noted at this plasticizer content as with films containing 45% plasticizer, the curves a t 25% plasticizer concentration are not given.
TABLE11.
011, EXTR4CTABILITY ANI) PHYSICAL PROPERTIES OF
PLASTICIZED GEON101 TJI timn t P ~~~~
Tensile ~ l Strengtha,b, ~ ~ Plasticizer ~ Loss ~ from - 5-Mil Lb./Sq. Thick Filmsb, % P!astition at cizer, Breaka,b, Inch 24 48 72 % % ' X 10-3 hours hours hours 25 4.1 45 22.0 24.0 25.5 1.7 25 4.7 45 1.9 5.0 7.5 7.0 25 4.3 45 14.5 18.5 1.8 17.5 25 3.9 45 1.8 11.0 15.5 13.5 25 4.9 21.5 45 2.0 16.5 19.0 25 4.6 45 2.2 8.0 6.5 9.0 4.2 25 2.8 45 16.0 14.5 17.5 25 4.7 14.0 45 16.5 18.5 1.8 Average of three measurements. Measurements at room temperature.
PREPARATION OF TL-DECAMETHYLE;VEBIS(O,O-DIBUTYL PHOSPHATE). Decamethylene-1,lO-glycol (solid) was added to phosphorus oxychloride (molar ratio 1:2) in diethyl ether solution. The mixture was stirred and nitrogen was bubbled through. TOP The reaction was mildly exothermic, and the temperature was maintained at about 35" C . The reaction was considered comTCP plete when all the solid glycol had dissolved and hydrogen Butadec chloride no longer evolved. The nitrogen blow was continued for 10 hours after the dissolution of the glycol in order to remove Hexadec as much excess hydrogen chloride as possible. Butyl alcohol Octadec was then added dropwise a t less than 5 " C. The molar ratio of butanol to starting glycol was 4:l. The reaction was quite Butahex exothermic and hydrogen chloride was evolved copiously. When Hexahex the reaction appeared complete, pyridine was added to the sohtion in the molar ratio of 6 pyridine to 1 glycol. The over-all Caprahex desired reaction is as follows: HO(CHJio0H
+ 4C4HgOH + 2POC13 + GCcHJJ +
a
b
The data on tensile strength and oil extractability of all the plasticized films are summarized in Table 11. With regard to the oil extraction data there are two points of significant interest: After filtering off the pyridine hydrochloride the final product was washed with water, dried over anhydrous sodium sulfate, and then stripped in vacuo for 10 hours a t room temperature to remove ether and pyridine. Attempts to fractionate the reaction product into the different phosphate ester components were unsuccessful. At high temperatures (250 o C.) and 1 mm. pressure the product decomposed, evolving the unmistakable odor of phosphine. The small amount of unreacted alcohol in the final product was estimated by reaction with acetic anhydride followed by titration for unesterified acetic acid. The values for the Feight % of free hydroxyl are given in Table I. The seven remaining diphosphate esters listed in Table I were prepared in the same manner as the decamethylenebis(dibutylphosphate). The preparation of cast plasticized polyvinyl chloride (Geon 101) films and the measurements of tensile creep and other physical properties are described in a previous paper (3) and elsewhere (1). Experiments on the oil extractability of the various plasticized films were carried out at room temperature according to the method of Reed (8).
On comparing the -20" C. compliances and the oil extraction data of TCP and Butahex with TOP and Butadec it is immediately apparent that the former two plasticizers impart relatively little softening action (as measured by creep) to the resin composition but exhibit good oil extraction resistance. The opposite is found for the latter two plasticizers. These results give supporting evidence to the earlier observation (1) that high oil extractability and good low temperature flex properties of plasticized films are directly related, in so far as the -20" C. tensile creep data give a measure of the brittle temperature of the films. The oil extractability properties of all six compatible diphosphate ester plasticizers listed in Table I1 proved to be better than that of TOP. However, the oil extraction properties of
RESULTS AND DISCUSSION
O
/
I ~
s d
The phosphate esters shoivn in Tttble I were incorporated into Geon 101 resin a t 25 and 45% concentration. The esters exhibited good compatibility in the base resin with the exception of the butylene-1,4-glycol derivatives. In Figures 1to 4 are shown the creep curves at 45% plasticizer content for all the compatible compositions a t 50°, 30°, lo", and -20" C., respectively. For purposes of comparisons, the creep curves of films containing 45% TOP and TCP are also given in Figures 1to 4. With the exception of the TCP plasticized films, all the compositions maintained the same relative compliances throughout the temperature range -20' to 50 C. This effect is not surprising in view of the known poor temperature characteristics of TCP plasticized composi-
/"
6.6
/
/('
5.4 4.2
d
'-. 8
v
3.0
1.8
0.6 -20
Figure 5. X = TCP
-10
0 10 Temperature,
20
30
40
50
C.
Comparison of Plasticizers at Various Temperatures by 10-Second Compliance 45% plasticizer 0 = Butadec A = Hexadec 0 = Octadec 0 = TOP 0 = Caprahex = Butahex A = Hexahex
March 1950
INDUSTRIAL AND ENGINEERING CHEMISTRY
7.8 6.6
3 x
5.4
6‘ 3.0 3
\
1.8 x
0.6 -20
Figure 6. X = TCP
-10
1
0 10 Temperature,
20 C.
30
40
60
Comparison of Plasticizers at Various Temperatures by 1000-Second Compliance 45% plasticizer 0 = Butadeo A = Hexadec 0 = Octadec 0 = Caprahex W = Butahex A = Hexahex
=
TOP
those diphosphate esters which are superior or comparable to TOP in creep, are, nevertheless, somewhat poorer than anticipated, on the basis of their dimeric structure. The greater plasticizing effectiveness of the decamethylene glycol derivatives as compared to the hexamethylene derivatives is probably due to the former being better solvents for Geon 101 (9). Furthermore, as noted previously, the butylene glycol derivatives exhibit limited compatibility wjth the base resin. Presumably, increasing the glycol linkage from 4 to 6 to 10 results
491
in the formation of products which are superior solvents for Geon 101. Whether or not ten carbons is the optimum length for the glycol bridge has not been specified. Table I1 shows that the diphosphate ester plasticized films exhibit a somewhat greater elongation a t break than the standards. The tensile strengths of both the standard and diphosphate ester plasticized films, on the other hand, are fairly uniform and appear unaffected by plasticizer type. This result is quite different from results on tensile strength measurements (3) for the liquid polymer plasticized films, where limited increased softening action was reached a t 25% plasticizer content. Although no measurements of volatility loss of plasticizer from the resin were made, it is reasonable to assume that the compatible diphosphates will be more permanent than conventional monophosphate plasticizers. The increased molecular weight and consequent lower vapor pressure of the diphosphate esters should enhance the performance of these materials in this respect. LITERATURE CITED
(1) Aiken, Alfrey, Janssen, and Mark, J . Polymer Sci., 3, 178 (1947). (2) Alfrey, Wiederhorn, Stein, and Tobolsky, J . Colloid Sci., 4, 211 (1949). (3) Ali, Mark, and Mesrobian, IND. ENQ.CHEM.,42,484 (1950). (4) Atherton, Openshaw, and Todd, J . Chem. SOC.,1945, p. 382; 1948,p. 1106. ( 5 ) Clash and Berg, Modern Plastics, 21, 119 (1944). (6) Cook, McCombie, and Saunders, J.Chem. Soc., 1945,p. 873. (7) Gerrard, Ibid., 1940,p. 1464. (8) Reed, IND.ENG.CHEM., 35,896 (1943). RECEIVED October 28, 1949. Presented before the Division of Paint, Varnish, and Plastics Chemistry at the 116th Meeting of the AnmRIcAN CHEMICAL SOCIETY. Atlantio City, N. J. Portion of thesis submitted t o the Polytechnic Institute of Brooklyn by R. H. Oliver in partial fulfillment of the requirements for the degree of master of science in chemistry.
Use of Amine Additives to Prevent Drying Loss on Aging A. C. ZETTLEMOYER AND DONALD M. NACE National Printing Ink Research Institute, Lehigh University, Bethlehem, Pa.
To prevent loss of drying on
aging of printing inks pigmented with alumina hydrate lakes, the investigation of hemin, o-phenanthroline complexes of the drier metals, and many other nitrogen-containing additives has been undertaken. The compound DMP-30[2,4,6-tri(dimethylaminomethyl)phenol] has been found to be the most effective and at the same time the most practical agent of those tested. Excess DMP-30 tends to inhibit drying and to accelerate livering; therefore, it should be used only when needed and then only’in amounts of 1 to 2% of the pigment. The mechanism of the activity of DMP-30 has been investigated. The DMP-30 is almost completely adsorbed by the pigment and the amount of cobalt adsorbed is not reduced by its presence. The conclusion is reached that DMP-30 is effective because it changes the acidic nature of the pigment surface.
D
ECREASE of drying rate on aging is a phenomenon re-
stricted to certain paints and printing inks which dry by oxidation and polymerization upon exposure to air in thin films. When certain pigments are used, the paint or printing ink may dry satisfaetorily soon after it is made up, but after storage for
several weeks or months it may dry slowly or not a t all. Apparently, the pigment adsorbs or reacts chemically with the drier metal, and thus the drier is removed from the vehicle and ita activity lost. Among the offending pigments are titanium dioxide, alumina hydrate lakes, and long carbon blacks. In an earlier report (8) it was shown that drier loss could be counteracted by the use of a feeder drier consisting of an insoluble cobalt compound feeding drier metal into the vehicle to replace that lost to the pigment. The present report contains the results obtained by the use of nitrogen-containing compounds. These studies have been concentrated on the alumina hydrate lakes because of their wide use in printing inks and the intensity of the drier loss frequently encountered with them. The long carbon blacks seem to present a distinct problem not solved by the remedies discussed here. This study of the use of amine additives to attempt to prevent drier loss was prompted by the interesting work of Nicholson (3) on o-phenanthroline-drier metal complexes. The present authors’ consideration of the problem led to the conclusion that hemin, obtained from hemoglobin of the blood, might serve as a suitable drier catalyst which also would not be adsorbed by pigments. This idea of the use of hemin as a drier was supported
