V O L U M E 20, N O . 1, J A N U A R Y 1 9 4 8
47
acknowledge the cooperation and assistance of N. W. Kempf and
F. V. Kenney of the Walter Baker staff. LITERATURE CITFD
(1) Am. 800. Testing Materials, "1935 Manual on Presentation of Data." 3rd printing. 1945. (2) Assoo. QfficialAgr. Chem., Official and Tentative Methods of Analysis. 6th ed.. 1945. (3) Boie, H.. P h m . Zty., 75,968 (1930). (4) Cortes, F. F., 2. Untersuch. Lebaam., 74,106 (19371. (5) Dekker. M.J.,Ree. 1rm. chin., 22,143 (1903). (6) Emery, W.O., and Spencer. G. C., J . Ind. Eng. Chem.. 10, 606 (1918). (7) Griebel, C., 2. Untwsuch. Lebasm., 71,534 (1936). (8) I h y , J.,and Haywood, P. J. C.,Anadysb, 71,162 (1946).
E. (to General Foods Corp.) US.Patent 2,416.484 (Feb. 25. 1947,. (10) Kunue, W.E.,Z. anal. Chha., 33, 1 (1894); Analyst, 11, 194 (9) Kremers, R.
(1894). (11) Maupy,Ibid., 22. 191 (1897). (12) Moir and Hinks. Ibid., 60,439(1935). R. F,, IND, ENG_ CHEM,, ANAL_ Eo,,15,361 (1943), (13) (14) Richardson, A. G.,and Campbell. Y X . , J . Am. Pharm. Assoc., Sci. Ed., 31. 24 (1942). (15) Wadsworth, R.V., Analyst. 46,32 (1921). (16) Ibid.. 47, 152 (1922). (17) Watson, Sheth. and Sudborouph. J . Indian Inst. Sci.. 5, 177-207 (1923). R ~ c ~ m eMhY n 5, 1947. Presented before the Division of Analytiod and Micro Chemistry &tthe 111th Meeting of the A r ~ n r m C ~x s m c ~ rSOCIETT. . AtlsnticCity,N. J.
Improved Polymerization Techniques e-Sealing Gaskets f o r Polymerisation in Bottles AND E. R. MEINCKE, The B.
F. Goodrich Company, Akron, Ohio
mernoa of conducting emulsion bolymerizations in beverage bottles equipped special puncture-sealing gaskets is discussed. The sealing gasket is de?d i n detail and the advantages realized through its use are pointed out. this type of closure, materials can be injected against pressures up to 70 ds per square inch or more by means of a hypodermic syringe. The presin the bottle can be determined quickly by a gage equipped with a hypodermic needle. From the pressure measurements, the per cent conversion of monomecs to polymer can be determined over a wide range with good aecuraoy. A
B
EVERAGE bottles &reused extensively in the laboratory as resotion vessels for a-ng out emulsion polymeriaations of synthetic rubber. When used with ordinary caps, the bottle polymerizations suffer certain disadvantages: Nothing can be added to the system without int,errupting the polymerization, and the conversion cannot be determined with any degree of accuracy without coagulating the polymer. The method of following the degree of couversion described by Fryling (8) for tube polymerieations by measuring the change in volume of the system is not satisfactory for bottle polymerizations. Following a suggestion by W. L. Semon, a puncture-seding cap has been developed mnsisting of a n ordinary crown cap with a oenter hole covered by a sealing insert and an oil-resistant gasket that can he used to advantage in bottle polymerizations. [Frank and Shepherd of the University of Illinois have developed a similar cap, ( I ) . ] Using this cap it is possible to add materials during polymerization with a hypodermic syringe and needle and t o determine the degree af conversion in the latter stages of the polymerization by pressure measurements through a needle. This method has been used successfully in laboratory synthetic ruhher polymeriaittions for several years.
members are died out of stock 0.04 inch thick which hits been compounded and cured in the recipe given in Table I. This stock swells,op eqntact yith butadiene and styrene to seal the
APPARATUS AND MATERIALS
Bottles. Heavy crown-cap bottles are used. The quart bottles weighat least 800 grams. Caw. A l l a x inch hole is drilled in the center of a crown cap
Table I.
Butvl Kuhher Sealant Stock
GR
Sen SUI1
1
TW
Cured 3"
minute^
Captax Stearic acid Zinc oxide
a t 286" x'. w m m e cheesecloth backing.
0 .s
1.0 5.0
Figure 1. Syringe Assembly and Self-sealing Caps A . Yale R-D Lok-syringe W E E . B. Luer-Lok stopcock No. WS1 C. Yale B-D stainless steel hmodumio needle (20-gaga) D. Rottlo cap with center hole E. Butyl rubber aesling momher F. Solvent-resistant gsaket
I
ANALYTICAL CHEMISTRY
48
Table 11. Solvent-Resistant Gasket Stock 100.0 100.0 F"
0
Table 111. Polymerization Butsdiene styrene Dodecyl mercaptan S.F. Bakes (purified a o a flakes) ~ Potassium Persulihte water Temperature, C . PolymerlratlO" co""em~on, ,% t:--
75.0 25.0 0.5
5.0 0.3 180.0 50
!5I*
The following procedure is used in charging a 24ounce bottle. To B clean bottle are added 175 grams of a map solution consisting of 5 grams of S.F. flakes dissolved in 170 grams of distilled water. The bottle is then chilled in an ice hsth and 10 cc. of a 3% by volume solution of potassium persulfate are added, followed by 25 grams of styrene containing 0.5 gram of dodeeyl mercaptan. The chilled bottle is now weighed on a balance sensitive to 0.1 gram, and 75 grams of butadiene are poured in from a thermos bottle equipped with pouring tube. Enough butadiene (4 to 5 grams) should he volatilized to ensure displacement of tho air from the bottle. (This should always be done under B good hood.) The bottle, capped with a hand capper, is ready to be placed in a constant-temperature water bath a t 50" C. in which a group of these bottles me rotated so that they turn end over end from 25 to 30 times per minute. Though bottles rarely break, the following precautions should be taken: Bottles should be examined for flaws or cracks before use. A bottle should never be taken directly from the ice bath and put into the 50' C. bath or vice versa. A face shield and rubber gloves should be worn when bottles are hnnd led under pressure.
It is frequently desirable or necessary to inject initiator (PO. tassium persulfate solution), soap solution, cII. monomers into the battle before the conversionis complete. This is done by dmwing the desired m o u n t of material into a gradurtted syringe, pushing the needle through the gasket, and injectin,5 the contents of the syGnge directly into the polymerization em)ulsion. When materials are injected into bottles at 50" C., a SJiringe no larger than 5 cc. should be used. The operation is madl2 somewhat easier by using a small valve on the syringe, which is opened after the needle has been inserted. As an addition2d precaution at high pressures a guard can he used to prevent thi3 plunger from flying aut of the syringe. I n determining the pressure, the bottle shoNuld be kept in an u p right position long enough for the foam ani2 latex to flow away from the cap before the needle is inserted. The mze should always be heated to a temperature equal to 01 ' slightly higher than the polymerisation bath temperature. If car e has been taken m displacing the air when the recipe was cliarged, the pressure . .. " . method of determining converslon, after the pressure drop has started, is accurate, giving vdues of +2'% or better. I n order to use this method, one must first determine the pressure-conversion curve for the system being run. Thereafter, the conversion can be determined quickly in the latter stages of polymerization. The pressure-conversion curve for the polymerization recipe given in Table Ill is shown in Figure 3. Figure 2.
Pressure Gage
assembled for rcadisg pressures through hypalsrmia nscdls B, C,0, E. Component p ~ r f sof adapter B . Fitting to reduce from ' l a inch pipe ei- to E//s inoh O.D.
A.
60
Gege,
coppr tubing
C. A,% inoh length of V S inch O.D. ooppor tubing
D. E.
LueeLok Btting feom aytingc a8 shown in F%g"re1 Yale B-D sfninless steel hypodermic needle ( 2 0 - w ~ )
..e
$
&-
50
-
2 40 -
00
I
Solvent-Resistant Gasket. The solvent-resistant gasket goes
30
-
.il
s
~~
~~~~~
T h i s stook is not affected appreciably by 6utadieneatyrene blends. Before we, the gaskets are extracted for 0.5 hour with ethyl alcohol, washed with hexane, and dried, in order to remove any materials present in the stock which could inhibit or retard polymeriaation. Hypodermic Syringes and Needles. Yale B-D Lok syringes with capacities of 0.5,1, 2, 5, and 10 cc., equipped with 20-gage Yale B-D rustless hvnodermic needles. are used as shown in ". Figure 1. Pressure Gages. Pressure gages (0 to 60 pounds per square inoh) and (0 to 30 pounds per square inch) ranges, equipped with adanter. Luer-Lok. and hvuodermic needle. as shown in Figure -2,~~&e ~ i s e d . The'adapG; is assembled by soldering the copper tubing. to the Luer-Lak, slipping the ring and nut shown in Rover the tubing, and sorewing them together. PROCEDURE
I n Table III n typiod butndiene-styrene copolymerization recipe is given.
c"
20-
; 8 IOE 0
IO
20
Figure 3.
30 40 50 60 Per c e n t Convemon
70
80
90
Pressure-Conversion Relation
The method described here for polymerization studies can also be applied to any system where it is necessary to add materials under moderate pressure while a reaction is in progress. LITERATURE CITED
Frank. R. L., and Shepherd, D. A.. unpublished report. (2) Fryling, C.F., INn. ENG.CHFM.,ANAL.ED., 16, 1 (1944). (1)
REOEIPDD January 17,1847.
.
