February 1951
4
INDUSTRIAL AND ENGINEERING CHEMISTRY
dered, injection molded, or extruded a t temperatures between 100' and 130O C., although not very easily. The photostability of the products can be improved b y photoinhibitors or by pigments, t h a t may also be added for other purposes. All products have a fair amount of crystallinity, and softeners can be incorporated only t o a limited extent; macromolecular softeners can be used t o counteract crystallization, especially the aftercrystallization that results in a n often undesirable gradual hardening of the products. Several applications, like floor tiles and pipes, have been developed on a semitechnical scale. Various methods of low temperature processing have been worked out. The products obtained in this way still possess the original high molecular weight and stability. Films and various other products of remarkable mechanical properties have been manufactured on a semitechnical scale; full advantage can be taken of the possibility of producing highly oriented products from the crystalline polymer (patent application pending). Cyclized Rubber. The technology of latex cyclized rubber has been studied from the following points of view. Its use as a plastic as such is difficult because i t starts t o soften considerably a t 50" C., whereas it does not flow easily at temperatures considerably above 50" C. Only little improvement of flow properties results from milling of the material; better results may be obtained after addition of softeners of the paraffinic oil type and cheap fillers. The most interesting application of latex cyclized rubber found up t o this moment is its use as a reinforcing filler in rubber. The best method of using it for this purpose is t o mix rubber latex and a cyclized rubber latex. This intimate mechanical mixture of latices can be processed and vulcanized as a n ordinary rubber latex, or i t can be dried and then treated according t o normal solid rubber technology. These combinations of rubber and cyclized rubber have very remarkable mechanical properties (26). The modulus at 300% elongation of a 70 rubber-30 cyclized rubber vulcanizate is high (150 kg. per sq. cm.), resilience is good (75% Ltipke), and heat build-up is rather low (20" t o 25" C. Goodrich flexometer )
.
319
Literature Cited (1) Amerongen, G. J. van, Brit. Patent 634,241 (1950). (2) Amerongen, G. J. van, and Koningsberger, C., J . Polymer Sci., 5, 653 (1950). (3) Amerongen, G. J. van, Koningsberger, C., and Salomon, G., Ibid., p. 639. (4) Bloomfield, G. F.,J . Chem. SOC.,1944,114. (5) Bloomfield, G. F.,and Farmer, E. H., J . SOC.Chem. Ind., 53, 121T (1934). (6) Blow, C. M.,Proc. Rubber Tech. Conf. London, 1938,186. (7) Gehman, S. D., Field, J. E., and Dinsmore, R. P., Ibid., p. 961. (8) Gordon, M.,IND.ENG.CHEM.,43,386 (1951). (9) Hirano, Sumito, and Oda, Ryohei, J . SOC.Chem. I d . J a p a n , 47, 833 (1944). (10) I. G. Farbenindustrie, Dutch Patent 44,662(1938). (11) Kambara, Shu, et al., J . SOC.Chem. I n d . J a p a n , 46,41-4,676-84, 761-7 (1943); Bull. Rubber Research Znst. J a p a n , No. 1, 14 (1945). (12)Le Bras, J., and Delalande, A., "Les DBrivbs Chimiques du Caoutchouc Naturel," Paris, Dunod, 1950. (13) Morris, J. C.,J . Am. Chem. SOC.,68, 1692 (1936). (14) Rumscheidt, G. E., and Nie, W. L. J. de, Dutch Patents 59,013, 59,323,59,325,59,731 (1947); U.S. Patent 2,469,847(1949). (15) Salomon, G.,Chimie et Industrie, 63, 567 (1950); 21st Congr. Intern. Chimie Industrielle. (16) Salomon, G., Discussions Faraday SOC.,2,353 (1947); Rec. trav. chirn., 68,903(1949). (17) Salomon, G., J. Polymer Sci., 3,32 (1948). (18) Salomon, G.,Schweiz. Arch. angew. Wiss. u. Tech., 16, 161 (1950). (19) Salomon, G.,and Koningsberger, C., J . Polumer Sci., 2, 522 (1947). (20) Salomon, G., Koningsberger, C., and UltBe, A. J., Proc. Second Rubber Tech. Conf. London, 1948,106; Rec. trav. chim., 69,95, 711 (1950). (21) Salomon, G.,Sohee, 8.C. van der, Ketelaar, J. A. A., and Eyk, B. J. van, Discussions Faraday Soc., in press, (22) Taft, R. W.,J . Am. Chem. SOC.,70,3364 (1948). (23) Veersen, G. J. van, J . Polgmer Sci., 5,S23 (1950). (24) Veersen, G. J. van, Proc. Second Rubber Tech. Conf. London, 1948,87. (25) Veersen, G. J. van, Rec. trav. chim., 69, 1365 (1950). (26) Veersen, G. J. van, and Boonstra, B. €4. S. T., Rubber A g e , 68,57 (1950). RECEIVEDOctober 4, 1950.
Communication 149, Rubber-Stichting.
ButadieneDStyrene Resinous Copolymers 4
-
Although high-styrene resins have become of great commercial importance during the past 5 years (approximately 25,000,000 pounds manufactured in 1949), comparatively little information on the polymerization processes or any systematic review of their properties can be found in the technical literature. The object of the present paper is t o supply such information. A series of butadiene-styrene copolymers with charging ratios of 50/50, 40160, 30170, 20180, and 10/90 was prepared. Polystyrene, prepared under the same conditions, was included as a control. Properties of the latices and resins obtained, presented in a systematic manner, were found to be largely dependent on the monomer ratio employed in the polymerization. For the first time a coherent picture is presented of the entire plastic range of the styrene-butadiene resins. This should encourage the further development of this large and expanding field, which includes such applications as natural and synthetic rubber reinforcing, impact resistant compositions, protective coatings, and latex paints.
-
J. D. D'Ianni, L. D. Hess, and W. C. Mast The Goodwear Tire & Rubber Co., Akren, Ohio
I
N THE past 5 years resinous copolymers of butadiene and
styrene have become of great commercial importance. This development has been spurred by the availability of these monomers in large quantities and a t low prices as a result of the synthetic rubber program sponsored by the Government in cooperation with the rubber and chemical industries. I n the period before World War 11, the rubber industry had become interested in resinous copolymers, particularly those obtained by chemical reactions of natural rubber. At t h a t time were developed such products as chlorinated rubber (Parlon, Hercules Powder Co.), cyclized rubber (Pliolite, Goodyear Tire & Rubber Co., and Marboq, Marbon Corp.), and rubber hydrochloride (Pliofilm, Goodyear Tire & Rubber Co.). Cyclized rubber has been of special interest as a rubber reinforcing agent and a s the vehicle or binder for pigments in special protective coatings, such as concrete paints and corrosion-resistant coatings.
320 '
INDUSTRIAL AND ENGINEERING CHEMISTRY
Table 1. Preparation of Butadiene- Styrene Copolymers at 50" C." Butadiene, parts Styrene, parts Dodecyl,mercaptan, parts Polymerization time, hours
1 0 100 0.10 17
2 10 90 0.15
3 8200 0.20
30 70 0.25
5 40 60 0.30
19.5
19.5
20
20
4
i;: i;: it :; i:: E it
6 50 50 0.35 20.5
i!:
; Total so@, 70 Conversion, % 10.1 10.0 pH of latex 10.45 10.2 9.8 9.65 Recipe. Water, 180 parts; monomers, 100 parts; sodium myristate, 1.5 parts of Wingstay S added to 5 parts' potassium p e h l f a t e , 0.3 part. each laiex before coagulation. Q
These promising developments, however, were cut short by the war, during which a large portion of the research and development effort of the rubber industry was channeled into the synthetic rubber program. It was recognized, however, that butadiene and styrene could be used to make resinous copolymers as well as rubbery copolymers, by proper selection of the charging ratio of the monomers. The first description of the properties and applications of a commercially available resin (Pliolite 5-3, a 15/85 butadiene-styrene copolymer) was published in 1946 as the outgron-th of work by Borders, Juve, and Hess ( 5 ) . Other highstyrene resins were subsequently described by Jones and P r a t t (16) and Fox (11). General information on high-styrene polymers was summarized by Rinkelmann (%?), Fordyce ( I O ) , and others (3).
Polymerization Studies The patent literature of the early thirties is filled Lvith references to butadiene-styrene copolymers, as a result of the German n-ork to develop Buna synthetic rubbers, but as early as 1930 scattered ( S I , 36) references may be found to German and British
Table 11. Preparation of IIore Highly Modified ButadieneStyrene Copolymers at 50" C." PolyDodecyl merization Total Mercaptan, Time, Solids, Conversion, NO. % Part Hours 70 % 7 0.15 18 36.9 99.5 0 37.2 0.20 18 100 0 8 36.9 18 99.5 0 0.25 9 37.2 18 100 0.20 10 10 37.2 100 10 0.25 18 11 37.2 18 100 12 10 0.30 37.2 18 100 0.30 13 20 37.2 20 18 100 0.35 14 36.7 18 20 0.40 98.8 15 37.2 30 0.40 20 100 16 36.9 99.5 20 30 0.45 17 36.8 99.0 20 30 0.50 18 37.2 20 0.50 100 19 40 36.5 20 98.0 0.60 40 20 36.6 20 98.5 21 50 0.50 37.2 20 50 0.55 100 22 37.2 20 50 0.60 100 23 0 Recipe. Water, 180 parts; monomers, 100 parts, sodium myristate 5 parts' potassium persulfate. 0.3 part. One part of P B N A added to eaod latex bkfore coagulation. Sample
Butadiene,
work on copolymers containing large amounts of styrene and small amounts of butadiene. No particular effort was made a t t h a t time to commercialize these findings. Konrad and Ludwig (18) prepared emulsion copolymers of butadiene-styrene containing 47.5 to 70% styrene, but were more interested in the rubberlike properties of the products. A recent patent (38)claimed copolymers of butadiene and styrene containing 80 to 95% styrene. Smith (29) claimed a waterproof coating consisting of a high styrene-low butadiene copolymer admixed with polyisobutylene and a waxlike material. Sparks and co-workers (SO) claimed that electrical insulating compositions of high-styrene resins and polyisobutylene were of particular value in the construction of ultra-high-frequency radio transmitting and receiving systems. TeGrotenhuis (34)mixed a relatively tough butadiene-
Vol. 43, No. 2
styrene in latex form with a well modified butadiene-styrene copolymer and isolated the product by co-coagulation. A blend suitable for shoe soles, wire covering, etc., was claimed (12) by mixing GR-S with 25 to 100 parts of a high styrene-low butadiene resin (5 t o 30y0)butadiene content and 10 to 25 parts of a cellulosic floc, Comparatively little information on polymerization processes leading to high-styrene resins can be found in the scientific literature. MacLean, Morton, and Nichols (22)recentlystudied butadiene-styrene copolymers over the entire range of monomer composition. By the use of tert-hexadecyl mercaptan (hexanethiol) as modifier and isolation of polymer a t low conversion, products of relatively narrow range of molecular weight and relatively homogeneous as to comonomer composition of the chains were obtained. Meehan (23) and Koningsberger and Salomon (17) also studied butadiene-styrene copolymers of various ratios. hIitchell and Williams ( 2 4 ) recently completed an excellent laboratory study of high styrene-low butadiene copolymers, and observed that the polymerization characteristics were similar to those found with GR-S, although by no means identical.
Preparation of Butadiene-Styrene Resinous Copolymers It was considered of interest to prepare under carefully controlled laboratory conditions a series of butadiene-styrene copolymers with charging ratios of 50/50, 40/60, 30/70, 20/80, and 10/90. Polystyrene was prepared under the same conditions as a control. The polymerization recipe employed was of the GR-S type, a s shown in Tables I and 11.
-4stock solution of sodium myristate was prepared from Seofat 13 (technical myristic acid, Armour & Co.) and used for all the polymerizations. The ingredients were measured into a 1-quart beverage bottle, with a monomer charge of 180 grams, closed with a cap having a Chemigum sealer and Teflon gasket, and rotated a t 30 r.p.m. in a water bath maintained a t 50' C. After an appropriate time the bottle was pressured with nitrogen and a syringe sample was removed for determination of solids content. After reaction was substantially complete, the contents of the bottles were blended and a portion was set aside for determination of latex properties. Then JVingPtay S (Goodyear Tire & Rubber Co.), a nonstaining antioxidant, or phenyl-2-naphthylamine (PBNA), was added to the remaining latex, which was coagulated with dilute hydrochloric acid. The product was washed free of chloride ion in a centrifuge and vacuum-dried a t 50" C. KO special study was made of changes occurring during polymerization, because the objective was to carry each polymerization to substantial completion. The amount of mercaptan modifier v a s increased in proportion to the amount of butadiene employed (Table I). To obtain significant flom- tests, another series of more highly modified resins was prepared (Table 11). The reaction time required to attain 97 to 99% conversion gradually increased as the ratio of butadiene charged was increased. The p H of the latex as obtained from the reactor exhibited a small but regular decreaEe with increasing butadiene content, but no ready explanation for this is available.
Butadiene-Styrene Copolymer Latices The latex samples were diluted to 30% solids content, vacuum-stripped free of monomers and other volatile impurities (maximum temperature 50" to 60" C.) and diluted again to 30% solids. Table I11 summarizes the properties determined on these samples, The p H values on the copolymer samples were practically constant, whereas the polystyrene latex exhibited a somewhat higher value. The Brookfield viscosities were uniformly lorn and independent of the spindle speed employed (2, 4, 10, and 20 r.p.m,), thus indicating lack of thixotropy. Surface tension values were fairly constant, but tended to increase with increasing butadiene content. This behavior probably is related to the p H values. The soap requirement and turbidity measurements ( 6 ) indicated t h a t the average latex particle size decreased with in-
INDUSTRIAL AND ENGINEERING CHEMISTRY
February 1951
Table 111. Properties of Butadiene-Styrene Copolymer Latices" 5
6
10/90
20/80
30/70
40/60
50/50
20 20 10.32 9 . 9 3
20 9.88
20 9.88
20 9.88
20 9.88
55.0
55.5
55.2
58.0
58.2
59.0
4.8 0.29
4.9 0.30
5.6 0.28
6.2 0.25
7.15 0.24
7.25 0.19
30
4 0 man. min.
Flakes Flakes Checks easily Chemical stability 0.323 0.306 0.302 (sa1t)e 1.45 Coagulation (sa1t)f 1 . 6 0 1 . 5 0 a Properties determined on stripped latices
321
only 1to 2 millimoles of salt per gram of polymer, the copolymers of higher butadiene content were not completely coagulated with more than 13.5 millimoles of salt. The mechanical and chemical stability data are plotted in Figure 1 as a function of butadiene content. Mechanical and chemical stabilities were also determined on latices 7 through 23 to confirm the results given in Figure 1.
Soft, rubbery
>08 >13.5
0.63 > 0.8 5.65 >13.5 at 30% solids.
b , c Ree (6).
See CZ~)'. ml. of 1 M NaCl solution Chemical stability = ml. of latex ml. of 1 M NaCl solution. f Millimoles of NaCl per gram of polymer for complete coagulation. d
+
e
creasing butadiene content, but the over-all change was small. I n comparison, Type I1 GR-S latex gives values in the same range covered by these experimental latices. The mechanical stability of the latex varied greatly with copolymer composition. Polystyrene and the 10/90 butadienestyrene copolymer exhibited a high degree of mechanical stability, the 20/80 and 30/70 copolymers a moderate degree, and the 40/60 and 50/50 copolymers a low degree of stability. The differences are so great t h a t it must be concluded that polymer composition is capable of exerting a specific effect upon the mechanical stability of the corresponding latex. On the other hand, the chemical stability of these latices upon addition of 1 M sodium chloride solution was found t o increase markedly as the butadiene content of the polymer was increased. The end point was taken as the point at which the small discrete particles, formed upon initial addition of the salt solution, suddenly lumped together in one mass. Whereas polystyrene and the copolymers of low butadiene content were completely coagulated by the addition of
Table IV.
Physical Characteristics of Butadiene-Styrene Copolymers
B-S charge ratio Butadiene content (from ioqine number) Tensile strength, lb./ s q . inch Ultimate elongation,
%
Hardness Shore AC Shore D Water absorption, %d
Olsen stiffness, inch1b.e Refractive index, 25' C.h Specific gravity, 250 c.% h o d impact, notched, inch-1b.t Heat distortion point,
1
2
0/100
10/90
0
.. 1.25a
3 20/80
4 30/70
5 40/60
28 8
37.6
6 50/50
10 8
19.2
3750a
2300a
800b
200b
100s
1 Sa
270a
400a
440b
5OOb
98468
84 38
35 16
27 12
0.10
0.10
0.10
0.10
0.10
0.10
10.56f
12.OO'J
3.2
0.25
0 07
0.05
1.5935
1.5893
1.5858
1.5769
1.5682 1.5592
1.0530
1.0467
1.0335
1.0179
0.9976 0.9795
2
2
2
..
..
..
142 106 66 33 21 5 a Determined on horizontal Scott tester: this machine not suitable for polystyrene. b DeJeLmLned o n Goodyear autographic tensile elongation testing machine. 0 A.S.'Y.M, U 676-47T. d A.S.T.M. D 570-42. e A.S.T.M. D 747-48T. f Sample brittle broke at 27O. 0 Sample stiff, rbached max. load at 24O. h Determined on Abbe refractometer by grazing technique. i A.S.T.M. D 792-48T. j A.S.T.M. D 256-47T. k A.S.T.M. D 648-48Ta. F.k
-z
Figure 1.
~
IO
20 30 BUTADIENE,
I 0
40
50
0
Latex Stability us. Butadiene Content
Films were cast from each latex for examination of their properties. Polystyrene and the 10/90 copolymer flaked when scratched, and the 20/80 copolymer gave a checked surface on drying. The 30/70 copolymer produced a tough, coherent film, whereas the 40/60 and 50/50 copolymers were definitely rubbery.
Physical Properties of Batadiene-Styrene Copolymers Table IV summarizes the various properties determined on the six solid experimental polymers. The butadiene content, as obtained by iodine number determination, was within 1 to 3% of the charging ratio employed. Physical properties of the raw polymers were determined by American Society for Testing Materials specifications wherever applicable. Samples for testing purposes were molded a s follows. Following a 3-minute warm-u period, the samples n-ere molded for 10 minutes and the mol% were cooled before removal of samples. The first three were molded at 290' F., the last three at 250" F,
47 3
g8&
98+ 81
122 - 10
As the butadiene content increased, the maximum tensile strength dropped rapidly from 3750 to 100 pounds per square inch, whereas the ultimate elongation increased from 1.5 t o 500%. The tensile strength and elongation values are plotted as a function of butadiene content in Figure 2. The Shore hardness exhibited a marked drop with increasing butadiene content, the D values ranging from 80 to 12. Water absorption values were low and independent of the copolymer composition. Olsen stiffness values varied tremendously with increasing butadiene content, a s would be expected in view of the change from the hard plastic stage to a soft, rubbery stage. Refractive index and specific gravity values decreased in a fairly regular fashion with increasing butadiene content, as one could predict from the polymer composition. However, as plotted in Figures 3 and 4, the variation in these values is not a strictly linear function of the butadiene content. Notched Izod impact values of 2 inch-pounds were obtained on the first three polymers. The last three polymers were not sufficiently rigid for this determination.
INDUSTRIAL AND ENGINEERING CHEMISTRY
322
The heat distortion points varied in a regular fashion from 142' to 5' F. in a comparison of polystyrene with the copolymers of increasing butadiene content, and are plotted in Figure 5 . The values obtained in this test are dependent upon the stress imposed on the sample; considerably higher values can be obtained a t lower stress.
properties. The purified polymers were also used for determination of refractive index. For comparison, samples of polystyrene were prepared by ordinary coagulation and by the procedure just described. The latter sample exhibited significantly lower power and loss factors. With increasing butadiene content, no significant change occurred in the dielectric constant, but the power factor and loss factor increased appreciably. Oxygen absorption measurements were also carried out on the raw polymers a t 150" C. It was found that whereas polystyrene absorbed no appreciable oxygen in 100 hours, the polymers containing butadiene absorbed appreciable amounts of oxygen proportional to the butadiene content of the polymer. The data are only of qualitative significance, however, because under the conditions of test these uncured polymers tended to shrink unevenly, thus changing the amount of exposed surface area.
0 so00
-vj 0:
4000
I
c
3000 W
a
tl
-g
Vol. 43, No. 2
2000
W
Applications of High-Styrene Resins
-I
1000
No compounding evaluation of the polymers prepared for this study was carried out. I n view of the great importance which high-styrene resins have achieved in the past few years in the rubber and plastics industry, however, it seems appropriate a t this point to refer to the voluminous technical literature on the applications which have been made with the commercially available resins, The use of the various commercial resins in rubber compounding has been described by a number of authors (2, 5, 11, 16, 28, 33,35). The usual procedure in mixing the compound is to band the resin on a hot mill and then slowly add the rubber, Either natural rubber or a wide variety of synthetic polymers exhibits varying degrees of mechanical compatibility with these resins. The rest of the compounding ingredients (sulfur, accelerator, etc.) can subsequently be added on a cool mill. Banbury mixing of all the ingredients except sulfur is readily accomplished, and the sulfur is added later by mill mixing. Recently, considerable interest has been show-n in so-called easy processing resins ( I S , $7). The high-styrene resins have been shown to be of particular benefit when compounded with synthetic rubbers, although valuable results can also be obtained with natural rubber. In general, the effects of adding increasing amounts of the resins to GR-S, for example, are to increase the tensile strength, per cent elongation, tear resistance, hardness, stiffness, and flex life. Other advantages noted are improved processing, primarily due to less "nerve" in the stock, and improved electrical properties of the finished article. Calender shrinkage is also greatly reduced. The properties of natural rubber vulcanizates containing highstyrene resins are different in some respects from those obtained with GR-S or nitrile rubbers. The stiffness, haidness, and abra-
W
I-
BUTADIENE,
Figure 2.
Wd
Tensile Strength and Elongation 2's. Butadiene Content
Data obtained with the 01sen flow tester illustrate the effect of temperature and pressure upon these polymers (Table V). For a given polymer it is readily seen t h a t with increase in temperature from 212' to 270' F., a large increase in rate of extrusion occurs a t a fixed pressure. As the butadiene content of the polymer increases, a large increase in rate of extrusion occurs; the change appeared t o be directly related to the polymer composition up to 40% butadiene. The modifier content also had a significant effect upon the extrusion rates. Presumably the lower rates obtained with the 50/50 copolymer were due to the rubberlike rather than plastic nature of the material. Compression deflections are plotted in Figure 6 for polystyrene and the 10/90 and 20/80 butadiene-styrene copolymers. The first two exhibited practically identical behavior, shattering before any appreciable deflection occurred. The 20/80 copolymer, however, behaved entirely differently, producing a well defmed yield point. The polymers containing larger amounts of butadiene were not suitable for this test. Electrical properties, as listed in Table VI, were determined on samples prepared by coagulating a portion of antioxidanbfree latex with 2-propanol and washing the .precipitated polymer three times with fresh alcohol for 5 minutes. The polymers were vacuum-dried a t 60' C. for 20 hours. The dried polymers were then molded in special molds before determination of electrical
r
1.06r $120
1.55
I
0
IO 20 30 BUTADIENE, (g\
40
Figure 3. Refractive Index z's. Butadiene Content
50
0
I
I
20 30 IO BUTAOIENE, Wd
I
40
I
50
Figure 4. Specific Gravity as Function of Butadiene Content
B U T A D I E N E , 1%)
Figure 5 . Heat Distortion Point us. Butadiene Content A.S.T.M. D 648.4
INDUSTRIAL AND ENGINEERING CHEMISTRY
February 1951
COMPRESSION, LBS. PER I N f
Figure 6.
Compression Deflection as Function of Butadiene Content X.
B-S
A.
B-S 20/80
0. B-S
0/100 10/90
sion resistance are increased, but the tensile strength, per cent elongation, tear resistance, and flex life tend to decrease, although the deterioration is not severe with 10 to 20 parts of resin per 100 parts of rubber. These differences are not unexpected, if one recalls that the gum stock pfoperties of natural rubber are excellent, whereas those of the synthetic rubbers mentioned are relatively poor. The properties imparted to rubber stocks by the addition of these resins have been well summarized by Aiken (1). In the rubber reinforcing field, these resins have found particular application in the manufacture of shoe soles and heels, rubber flooring, hard board stocks, gaskets, caster wheels, electrical insulation, hard rubber stocks, and many other mechanical goods. Hoover (14) recently stated that 3570 of "leather" shoe soles made in 1949 probably consisted of combinations of synthetic rubber and special butadiene-styrene resins. In the impact-resistant plastics field, where a relatively small amount of rubber is used to plasticize the resin, many interesting applications (2)have been made, such as golf ball covers, cutting
Table V. Olsen Flow Characteristics of Butadiene-Styrene Copolymers
L
Sample No. 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Butadiene,
%
0 0
0
10 10
10 20 20 20 30 30 30 40 40 50 50 50
Table VI.
Dodecyl Mercsptan, Part 0.15 0.20 0.25 0.20 0.25 0.30 0.30 0.35 0.40 0.40 0.45 0.50 0.50 0.60 0.50 0.55
0.60
Electrical Characteristics of ButadieneStyrene Copolymers" 1U 0/100 2.74 2.73 0.0163 0.0235 0.00045 0.00064 1
B-6 charge ratio Dielectric c o n s t p t Power factor Loss factor
Olsen Flow,Inches per Minute 212O F. 240° F. 270° F.' 0.15 1500 0.18 1500 0.21 1500 1500 1.70 2.15 1500 2.04 1500 0.45 500 0.52 500 0.59 500 0.66 500 500 1.02 1.45 500 1.38 500 3.40 500 0.77 500 1.20 500 1.80 500
Lb./sq.in.
O/lOO
2 10/90 2.80 0.025 0.0007
3 20/80 2.70 0.146 0.004
4 5b 6b 30/70 40/60 50/50 2.73 .. 0.79 .. .. 0.02 .. ..
..
All polymers extracted with 2-propanol except 1U. Tests made on dry samples a t 35" C. and 1 ko. frequency. b Satisfactory test samples could not be molded from raw polymers.
323
blocks or beam punch pads, football helmets, bowling balls, luggage, printing plates, and golf club heads. High-styrene resins have also found considerable utility in protective coatings and other solution applications. The use of such a resin (Pliolite 5-5)in concrete floor finishes, stucco paints, traffic paints, and plaster sealers has been reported by several investigators (7, 9, 36, 40). Coatings based upon this resin are characterized by alkali resistance, waterproofness, abrasion resistance, and good adhesion. Another recent solution application of considerable interest is in the formulation of heat-sealing, creaseproof, water vaporproof coatings for paper. For this use another high-styrene resin, Pliolite &7, has appeared on the market in solution form or in compounded forms. Because the high-styrene resins are usually prepared by emulsion polymerization methods, the unique opportunity exists of applying them to latex compounding. Little has been published in this field, but large scale applications are rapidly being developed. Irvin (16) described the water dispersion (Marmix) of a highstyrene resin and its application to latex compounding with GR-S and butadiene-acrylonitrile copolymer latices. Weatherford and Knapp (37) discussed the properties and applications of a latex (Pliolite Latex 190) containing a resinous copolymer of about 10% butadiene and 90% styrene. Applications mentioned are molded toys and sport equipment, dipped goods, latex threads, paper impregnants, fabric coatings, latex foams, and wire and cable insulation. Storey and Williams (32) studied latex blends of styrene resins and GR-S. Finally, the use of high-styrene latices in emulsion paints is rapidly assuming prominence. Ludwig (90)and Ryden, Britt, and Visger (26') recently described the use of Dow Latex 512-K (containing a 40/60 butadiene-styrene copolymer), with and without the use of high-styrene resin latex, in this application. Ryden (26) claimed a paint comprising a butadiene-styrene copolymer latex of a certain composition, plus pigments and other suitable compounding ingredients. Emulsion paints based on Chemigum Latex 101 (containing a 45/55 butadiene-styrene copolymer) were also described recently by Burr and hlatvey (8). Emulsion paints exhibit a number of advantages over the conventional oil paints, such as freedom from paint odor, excellent washability, and inertness to alkaline materials. McIntyre and co-workers (21)discussed styrene-butadiene copolymer latices as raw materials for the coatings industry. During the past 5 years the use of high-styrene resins has shown a continuous growth because of their enthusiastic reception in the rubber, plastics, paint, and other fields. It is conservatively estimated (4) that 25,000,000pounds of these resins were manufactured in 1949. As new and better polymers specifically tailored for specific applications become available, it is certain that the total production of butadiene-styrene resinous copolymers will show a substantial increase in the near future.
Acknowledgment The authors are grateful to W. T. Van Orman and the Rubber and Plastics Testing Department for obtaining molding and test data, to S. D. Gehman and R. B. Stambaugh of the Physical Research Division for electrical data, and to the Goodyear Tire and Rubber Co. for permission to publish this paper.
Literature Cited (1) Aiken, W. H., Modern Plastics, 24, No. 6, 100-2 (1947); 27, No.0,724 (1950). (2)Ibid., 26, NO.2,99-103 (1948). (3)Anon, Ibid., 25, No. 11, 93-8 (1948). (4) Ibid., 27, No. 6,62 (1950). (6) Borders, A. M., Juve, R. D., and Hess, L. D., IND.ENQ.CHEM., 38, 955-8 (1948). (0) Borders, A. M., and Pierson, R. M., Ibid., 40,1473-7 (1948). (7) Burr, W. W., Oflcial Digest Federation Paint & Varnish Production Clubs, 277, 198-207 (1948).
INDUSTRIAL AND ENGINEERING CHEMISTRY
324
(8) Burr, W.W., and Matvey, P. R., Ibid., 304,347-58 (1950). (9) Endres, H. A., Am. P a i n f J., 32,86, 88-92 (1947). (10) Fordyce, R. G., I n d i a Rubber W o r l d , 118,377-8 (1948). (11) FOX,K. M., Ibid., 117,487-91 (1948). (12) Gates, G. H. (to Wingfoot Carp.), Can. Patent 459,736 (Sept. 13, 1949). (13) Holt, C. R., Susie, A. G., and Jones, M.E., I n d i a Rubber World, 121, 416-18, 423 (1950). (14) Hoover, J. R., quoted in I n d i a Rubber J . , 116,595 (1949). (1.5) Irvin, H. H., I n d i a Rubbe7 World, 114, 680-2 (1946). (16) Jones, M. E., and Pratt, D. M., Ibid., 117, 609-10 (1948). (17) Koningsberger, C., and Salomon, G., J . Polymer Sci., 1, 353-79 (1946). (18) Konrad, E., and Ludwig, R., U. S. Patent 2,335,124 (Nov. 23, 1943). (19) Lindbeck, W.A., and TVoltz, F. E., private communication to Office of Rubber Reserve. Oct. 24. 1946. (20) Ludwig, L. E., Oficial Digest Federation P a i n t & Varnish Production Clubs, 276, 122-4 (1948). (21) McIntyre, 0. R., Taber, D. A., and Young, A. E., Program, Chemical Institute of Canada, p. 29, Toronto, June 19-22, 1950. (22) RlacLean, D. B., Morton, M., and Nichols, R. V. V., IXD. ENG. CHEW.,41, 1622-6 (1949). (23) Illeehan, E. J., J . Polymer Sei., 1, 318-28 (1946). (24) Mitchell, J . M., and Williams, H. L., Can. J . Research, 27F,3546 (1949). (25) Ryden, L. L. (to Dow Chemical Co.), U. S. Patent 2,498,712 (Feb. 28, 1960). (26) Ryden, L. L., Britt, h-,G., and Visger. R. D., OJSiciaZ Digest Federation Paint & T'arnish Prodtaction Clubs, 303, 292-30 1 (1950).
Vol. 43, No. 2
( 2 7 ) Sell, H. S.,and McCutcheon, R. J., I n d i a Rubber World, 119,66-
68, 116 (1948). (28) Ibid., 121,687 (1950) (abstract). (29) Smith, W. C. (to Standard Oil Development Co.), U. S. Patent 2,396,293 (March 12, 1946). (30) Sparks, W.J., Gleason, A . H., and Frolich, P. K. (to Standard Oil Development Co.), U. S. Patent 2,477,316 (July 26, 1949); Brit. Patent 577,860 (June 4, 1946). (31) Standard Telephones and Cables, Ltd., Ibid., 345,939 (June 6, 1930); 357,624 (June 20, 1930). (32) Storey, E. G., and Williams, H. L., Program, Chemical Institute of Canada, p. 35, Toronto, June 19-22, 1950. (33) Susie, A. G., and Wald, W. J.. Rubber Age (S.Y . ) , 65, 537-40 (1949). (34) TeGrotenhuis, T. A , , U. S.Patent 2,457,097 (Dec. 21, 1948). (35) Thies, H. R., and Aiken, W.H., Rubber B g e (.V. Y . ) ,61,51-8 (1948). (36) Tschunkur, E., and Bock, W.,Ger. Patent 588,785 (Nov. 27, 1933). (37) Weatherford, J. A, and Knapp, F. J., India Rubber World, 117, 743-4, 748 (1948). (38) Wingfoot Corp., Brit. Patent 606,980 (Aug. 24, 1948). (39) Winkelmann, H. A., I n d i a Rubber World, 113,799-804 (1946). (40) Workman, R. E., Oficial Digest Federation Paint & V a r n i s h Production Clubs, 291, 177-87 (1949). REcElVED October 6, 1950. The greater portion of this payer was first presented a t the Rubber Chemistry Division lIeeting, Chemical Institute of Canada. Toronto, Ontario, J u n e 21, 1950. Contribution 183 from Goodyear Tire B- Rubber Co.
Polysulfide Liquid Polymers e
J. S. Jorezak and E. M. Fettes Thiokol Corp., Trenton, N . J. T h e development of the polysulfide liquid rubbers was begun with the aim of obtaining a compatible vulcanizable plasticizer for the polysulfide rubbers. I t developed that the liquid polymer produced was unique in being a solventfree flowable liquid which could be vulcanized even at room temperature to a rubber. The cured rubbers have the physical properties characteristic of the polysulfide polymers, but are useful in a wide variety of applications, owing to the ease of handling a liquid material. The liquid polymers can be used with soluble curing
agents for the impregnation of leather, fabrics, and wood. The polymers can be compounded on a paint mill, in a ball mill, or in an internal mixer with fillers and reinforcing pigments. In the compounded form, they can be used as adhesives, casting compounds, coatings, and sealers. The cured liquid polymers are substantially odorless and have a service temperature from -70' to 300' F. The polymers are resistant to oils, aliphatic and aromatic fuels, and most solvents. They have good electrical properties and excellent ozone and oxidation resistance.
T
temperature properties are inherent in the polymer and are not dependent on special compounding techniques.
HE polysulfide liquid polymers are a comparatively recent
development conceived a t the Thiokol Laboratories in 1943. The development was initiated by the problem of finding methods t o reduce the molecular weight of a polysulfide rubber which was too tough t o process upon conventional rubber milling equipment. T h e problem was solved by reduction of a few of the disulfide links present in the polymer chain. I t was soon found that the method was applicable to the preparation of polymers low enough in molecular weight to be liquids. The method produces dimercaptans (dithiols) of high purity which are extremely active in a wide variety of chemical reactions. Some formulations have been developed which depend on conversion from the liquid to rubber state at temperatures as low as 50' F. in a period of about 30 minutes. Most of the converting agents function through oxidation with hydrogen removal from the thiol and a linkage of sulfurs to reform the disulfide group. The converted polymer has the general properties of the polysulfide polymers: good solvent resistance t o a wide range of solvents, low diffusion rate of gases, good resistance t o oxidation, ozone, and weathering, and a service temperature range from -65" to +250° F. (Some compounds can withstand intermittent temperatures as high as +350' F.) The low
Preparation The preparation of polysulfide polymers by the reaction of organic dihalides and sodium polysulfide
ClCH*CH?CI
+ K a 8 , --+(CH,CH&). + 2NaCl
(5 varies
from 1.0 to 5.0)
has been known for some time ( 5 , 7 ) . If an excess of sodium polysulfide is used, rubbers of high molecular weight can be readily produced. It is popsible to prepare liquids of low molecular weight in many cases by using a deficiency of sodium polysulfide. The products have chlorine terminals which are not easily coupled t o form products of high molecular weight. Thermal depolymerization has also been used to make liquid polymers (Q),but this reaction is not readily reversed t o reform the rubber. The most practical method found has been reductive cleavage of disulfide groups t o yield products which have thiol terminals.
