Emulsion Polvmeri ation of iene
J
H . W . Starkweather', P . 0. Bare, '-1. S . Carter, F . 5 . Hill,J r . ,.'F R . Hicrka, C. J . ,Mighton, P . A . Sanders, H . W . U'alker, a n d M.A . Youker E. I. DU PONT DE NEMOURS
COMPANY, mc., B-YLWNGTON, DEL.
T h e results of an exploratory study of the emulsion polymerization of conjugated diene hydrocarbons to yield rubberlike polymers are summarized. Such polymerization variables are discussed as purity of reagents, nature and amount of a second monomer, emulsifying agents, alkali concentration, catalysts, catalyst activators, modifying agents, temperature, and yield. An investigation of the influence of some 214 different compounds copolymerized
w i t h butadiene re5eals wide differences in the polymerization rate and properties of the copollmers, depending u p o n the structure of the second monomer. Such vinyl cornpounds as methacrylic acid esters, methyl vinyl ketone, dimethyl vinyl ethynyl carbinol give with butadiene potentially useful copolymers. Convenient forms of equipment for the small scale preparation, compounding, and testing of new types of elastomers are described.
L
i n vile series of experiments the shift froin distilled water to the tap water available reduced the product yield from 90 to 40%i;,. While oxygen is generally Considered to be a cat'alyst for polymerization, the presence of an excessive amount of oxygen may retard or actually inhibit polymerization. Carbon dioxide has a retarding effect on the poIymerization rate in many systems, aiid results may be influenced by contamination of samples stored in %r dry-ice box.
ESS than a century ago milliams obtained isoprene by the
thermal decomposition of natural rubber. This discovery was an essential step in a series of researches in several different countries which has culminated in the production of over a million tons of synthetic rubberlike products in a single year. The chemist', like the rubber tree, is able to produce various types of rubber as aqueous emulsions, although the actual processes of manufacture are undoubtedly far different. Liquid butadiene, isoprene, 2,3dimethy1-1,3-butadieneJ and chloroprene have been polymerized to rubberlike materials without the addition of other chemicals, but the chemist and chemical engineer have been more successful in producing uniform products by commercially practical methods since the emulsion processes for polymerization were developed. This paper is an attempt to summarize the results obtained in investigating the emulsion polymerization of conjugated diene hydrocarbons in these laboratories from 1936-42. During the past four years other commercial and academic laboratories have investigated certain phase5 of this problem in more detail than is presented in this paper. Before discussing the properties of the products obtained from specific polymerizable compounds, it seems advisable to consider certain factors, such as purity of reagents, monomer-water ratio, etc., which may have a marked effect on the rate of polymerization or properties of the products.
RATIO OF MONOMER TO WATER
The concentration of the monomer in the emulsion may havr B marked influence on the rate of polymerization. For example, the yield obtained by polymerizing a butadiene-methyl methacrylate mixture in sodium oleate emulsion, under otherwise identicai conditions and with the ratio of monomers to all components except water the same, increased from 36 to 62 to 857, when the monomer content of the emulsion was increased from 20 to 30 to 45%, respectively. Although more concentrated emulsions may polymerize faster, their greater viqcosity results in poor heal transfer, and control of polymerization a t a fixed temperature becomes mole difficult. PREPARATION OF EMU1,SIOSS
Uniformity of initial nionomer emulsions is important in order to obtain reproducible polymerization cycles and uniform quality
PURITY OB REAGENTS
of polymer. I n small scale laboratory \vorli it is usually sufficient to agitate the polymerizing vessel during polymerizatiori. Frequently it is advantageous to form t,he emulsifying agrnt, in s i f l i (14) rather than to use a prepared material. When n-orking xith fatty acids, rosins, or long-chain amines, tve dissolre the oilJoluble material in the monomer and dissolve the mater-soluble, alkali or acid in the aqueous phase. -4uniform, well-dispersed emulsion is readily obtained when these two solutions are mixed and agitated in the preliminary stages of the polymerization process. Although we have not observed pronounced differences as li result of using a preformed emulsifying agent instead of that. formed in situ, the micellization of the agent could be different,. Variations might, be expected, therefore, in certain polymerizntion systems.
The purit,y of all materials used to prepare the emulsions must be carefully controlled since the addition of almost any compound is likely to accelerate or to ret'ard polymerization or to affect the quality of the product. I n preliminary work a t least, all monomers should be freshly distilled, preferably at reduced pressure, in order to minimize polymerization during distillation. The effect of exposure to air and possible formation of peroxides must be considered. Many of these peroxides are not only hazardous, but may have either a favorable or an unfavorable influence on polymerization. It is also advisable t o use distilled water in preliminary experiments since the presence of even minute traces of impurities, such as copper or iron, may alter the polymerization. 1
Deceased 31ay 18, 1946.
210
INDUSTRIAL AND ENGINEERING CHEMISTRY
February 1947
METHOD O F ADDITION
Experience has shown that misleading results may be obtained by failure to add everything to the polymerization system in the proper sequence. If the different monomers are mixed for some time before emulsification, there is a possibility of a Diels-Alder type of reaction taking place to a sufficient extent to alter the properties of the product or to reduce the yield. The addition of a catalyst activator to the aqueous solution too long before its use in the polymerization system may result in a retardation rather than an activation of the polymerization rate. I n investigating the copolymerization2 of butadiene and methyl vinyl ketone, it was discovered that the addition of the ketone to the aqueous solution of soap and catalyst a short time before the butadiene was added resulted in the formation of almost no polymer. When the two monomers were added simultaneously to the aqueous solution, a good yield of high grade product was obtained. EMULSIFYING AGENTS
The primary purpose of the emulsifying agent is to assist in the formation of a stable oil-in-water emulsion which will not break during polymerization but will give a latex capable of being readily broken or coagulated after polymerization is completed. However, it is well knonm that emulsifying agents not only serve as such. but also affect the rate of polymerization and the quality of the resulting elastomer. Typical emulsifying agents for use in alkaline systems include the alkali metal and ammonium salts of fatty acids, rosin, modified rosins, napththenic acids, alcohol sulfate esters, and various aliphatic and aromatic sulfonic acids. In acidic emulsions the hydrohalides of long-chain amines may be useful. Other nitrogen-containing compounds, such as the quaternary ammonium halides and substituted betaines, have given good results under various conditions. Mixtures of 75 butadiene-25 styrene were polymerized in the presence of D D mercaptan (Lorol mercaptan from C12-Cla alcohols) in potassium persulfate-activated systems containing 4 or 57, of some of the more promising emulsifying agents. The following results indicate that various types of emulsifying agents may be used successfully: Emulsifying .4gent, % F a t t y alcohol sulfate, 5
‘
PH
3 6 >10
Aliphatic (av. Cis) sodium sulfonate, 4 Sulfated meth 1 oleate 4 Sodium naphtgenate, 4 Sodium oleate, 4
>10 >10
>10 >10
Polymerization Ttrnz., Time, Product hr. YieldQ, % 50 12 70 50 12 90 50 12 95 40 40 40
40
20 20 20
17
96 84 93 92
5 Throughout this paper the term “product yield” is used to denote the yield based on original weight of monomeric material employed without correcting for the emulsifying agent or stabilizer included in the finished elastomer.
Satisfactory emulsions are obtained by using some of the commercially available soaps, such as Ivory and Palmolive, as well as sodium oleate. The merits of the Rubber Reserve soap are well known. Nancy mood rosin soap alone may give interesting polymers but is not very satisfactory for persulfate-activated butadiene systems, owing to the slow rate of polymerization. The rate of polymerization may be greatly increased by hydrogenating the rosin or subjecting it to hydrogen exchange. Combinations of rosin soaps with fatty acid soaps appear to be advantageous when employed in certain preferred polymerization systems. The use of the rosin soap tends to reduce the precoagulation during polymerization, to improve the mill behavior of the polymer, and to result in polymers that are more uniform with respect to tensile properties. The following results, obtained 2 Although the authors believe that the term “interpolymer” better describes a polymer in which z and y monomer units exist in the same molecule, they conform t o the customary “copolymer” terminology throughout this paper.
211
with 75 butadiene-25 styrene mixture, in potassium persulfatepotassium ferricyanide activated systems, indicate that a mixture of 4% oleic acid and 2% Nancy wood rosin gives desirable results: Oleic Acida,
%
Nancy Wood Rosin, %
0
4
’
Ratio, Rosin: Total Acid 1.0
Total Emulsifying Agent, %
Product Yield a t 40°C. for 20 Hr., %
4
25
Commercial red oil was used.
If neither rosin nor fatty acid is desired in the finished product. the sulfonic acid type of emulsifying agent may be preferred Conditions of coagulation may be such as to convert the sulfonic acid to an innocuous insoluble salt or t o leave it in a highly soluble form that can be washed out of the polymer. Some materials that are relatively ineffective as emulsifying agents in preparing the initial emulsion are quite effective as dispersing agents for preventing flocculation of the emulsion during polymerization. An example is the condensation product of a naphthalene sulfonic acid and formaldehyde (0, 13) such as that sold commercially as Daxad 11. The use of such an agent may permit decreasing the percentage of soap required. CONCENTRATION OF EMULSIFYING AGENT
The rate of polymerization may be markedly influenced by thc, concentration of the emulsifying agent. For example, monomer conversions of 50-6974 have been obtained by polymerizing butadiene for 64 hours a t 10” C., using 25% sodium oleate. Increasing the sodium oleate to 50% has given monomer conversions of 62-76%, depending on the catalyst, in 40 hours. By contrast, when 4% soap was used, several hundred hours were required for comparable polymer yields. The effect of variations in concentration of sodium oleate upon two different butadiene-styrene systems is shown by the following data; in each case 0.75 part excess sodium hydroxide, 1 part Daxad 11, and 1part potassium persulfate were used: Butadiene-styrene ratio Potassium ferricyanide, % Mercaptan % ours of pblyrneriaation Product yield, % ’ 4% N a oleate N a oleate N a oleate N a oleate
68
70:30 0 Pinene, 1 82 a t 40’ C .
76:26 0.15 DD, 0 . 7 6 10 a t 50’ C.
...
90 97 105
88 97 102
...
EFFECT OF ALKALINITY
The rate of polymerization is also influenced by the pH of the emulsion. The relations between the yield and varying amounts of excess sodium hydroxide for 75 butadiene-25 styrene mixtures polymerized in the presence of varying amounts of potassium persulfate in emulsions containing 4 parts oleic acid, 2 parts rosin, 1 part Daxad 11, 0.15 part potassium ferricyanide, and 1.75 part pinene mercaptan are shown in Figure 1. For each Concentration of persulfate, there is a concentration of sodium hydroxide which appears to give the optimum results. Figure 2 indicates that the rate of polymerization of a 75 butadiene-25 styrene mixture in sulfonated petroleum oil emulsions is influenced by the concentration of the emulsifying agent and the amount of excess caustic in much the same manner as in the fatty acid soap systems; but in these cases the optimum rates are obtained with somewhat lower concentrations of excess caustic. It appears that a t least 4Y0emulsifying agent is required t o give a stable emulsion with a suitable polymerization rate. The emulsion contained, in addition t o the sulfonated petroleum oil, 1 part Dasad 11, 0.75 part D D mercaptan, 1 part potassium per-
Vol. 39, No. 2
INDUSTRIAL AND ENGINEERING CHEMISTRY
212
1001
100
I
,
I
,
I
,
1
I
1 1
1
40 30 20
% EXCESS NoOH 20 hours at 40' C.
% EXCESS NaOH 13 hours a1 50' C.
Figure 1. Effect of Excess Sodium Hydroxide with Varying Persulfate o n Polymerization of 75 Butadieiie25 Styrene i n Oleate-Rosinate Emulsion (Dr'umbers on Curves Refer t o Per Cent P o t a s s i u m Persulfate)
3 0 L J 20
0.1 0.2 0.3 0.4 0.5 0.6 0.7
0.8
0.9
1.0
% EXCESS NaOH
Figure 2. Effect of Excess Sodium Hydroxide on Polymerization of i 5 B u t a d i e n e 4 5 Styrene in Sulfonated P e t r o l e u m Oil Emulsions for 20 Hours a t 40" 6. (Numbers o n Curves Refer t o Per Cent Sulfonated Petroleum Oil)
1
5 O L - d a25 0.5
1.0
0.75
1.25
1.5
% KZS~OB
Excess S a O H Daxad 11 DDmercaptan KsFe(CN)s KZSZOS
75
Butadiene Styrene Water Aliphatic (Cid sulfonate
25
160 4
\' -I
401
Figure 3. Effect of Persulfate on polymerization of Butadiene-Styrene in Aliphatic Sulfonate E m u l sion for 18 Hours a t 40" C. 0.15 1
0.75 0.1s X
0.2
0.4
0.6
0.8
% TERTIARY B U T Y L
1.0 1.2 HYDROPEROXIDE
Figure 5. Effect of tert-Butyl Hydroperoxide w i t h Varying Ferrocyanide on PolymeFization of Butadiene-Styrene in Oleate Emulsion for 16 Hours a t 40" C. (Curve R'umbers Refer t o Per Cent &Fe(CY), .3H20) Butadiene Styrene Water
76 25 150
4 0.75 1 1. 5
L 90
0
n
-07
2
4
6 8 IO I2 14 16 18 20 22 TIME IN HOURS
F i g u r e 4. Effect of P o t a s s i u m Ferricyanide o n Polymerization of 75 Butadiene-25 Styrene af 50" C. in Emulsion C o n t a i n i n g a P a r t s Palmolive Soap a n d 0.5 P a r t DD 3Iercaptan Curve Yo. IZzSnOs KsFe(C;1J)a Excess &&OH Daxad 11
1
2
3
0.6 1.25 0.6
... ..,. ... ..
OP
1.25 0.15
,. 1 .
4 0.601' 1.25 0 15 0 25 0 26
6 7 8 9 IO II 12 13 14 15 16 17 18 19 20 21 22 N O OF CARBON ATOMS IN MERCAPTAN
CHAIN
Figure 6. Effect of Chain L e n g t h of Merc a p t a n on Plasticity of Copolymer f r o m 75 B u t a d i e n e 2 5 Styrene Mixture w i t h 0.75 P a r t Mercaptan (100% Basis), 20 Hours a t 48" C. 0 = product yield of 85 to 95% X = product yield of 70 to 85%
INDUSTRIAL AND ENGINEERING CHEMISTRY
February 1947
ablr properties even when obtained in essentially 1007’ product yields. Potassium ferrocyanide also has a marked effect upon polymerizations activated with tert-butyl hydroperoxide (Figure 5 ) . These results indicate that there is an optimum concentration for both potassium ferrocyanide and tert-butyl hydroperoxide.
sulfate, and 0.15 part potassium ferricyanide. The addition of 27, rosin improves the stability of the emulsion, but, even here, the use of less than 4 7 , sulfonated hydrocarbon results in an excessively slow polymerization cycle. CATALYSTS
The use of catalysts or polymerization initiators is essential in order to obtain suitable polymerization rates. I n practice oxygenyielding compounds have been foun4 more effective and more adaptable to control than oxygen itself. Although the term “catalyst” has been applied to such compounds, they are not catalysts in the true sense since they are usually consumed. Compounds such as benzoyl peroxide or fatty acid peroxides, which are soluble in the oil phase, can be used as catalysts but in practice have given less favorable results than the water-soluble types. Hydrogen peroxide can be used but salts of per acids such as persulfates and perborates have given more consistently satisfactory results. The choice of catalyst depends upon the other components of the polymerization system. I n general, persulfates have been favored in the work covered by this report, but some interesting results with tert-butyl hydroperoxide also have been obtained. There is usually an optimum concentration of catalyst, which may vary with the different systems. The following data, obtained by polymerizing a mixture of butadiene and methyl methacrylate for 16 hours a t 60’ C. in alkaline-sodium oleate emulsion catalyzed with ammonium persulfate, indicate that 1%functions as a more effective catalyst than either smaller or larger amounts in this particular system: Ammonium Persulfate, % 0
Product Yield, % ’
Ammonium Persulfate, %
Product Yield, %
6 50
1.0 1.5 2.0
97 95 68
0.25
85
0.5
*
Similar variation in polymerization rates with variat’ions of potassium persulfate is shown by a more complicated butadienestyrene system in Figure 3. I t is possible that the lower yield with higher concentrations of persulfate may have been due to a variation in the pH of the emulsion, caused by the decomposition of the persulfate. CATALYST ACTIVATORS
The acceleration of polymerization by a primary catalyst such as a persulfate may be greatly increased by the use of a secondary catalyst or activator. As will be discussed later, compounds such as the mercaptans, used as modifying agents, may also affect the polymerization rate. For diene hydrocarbons certain iron and copper complex compounds, such as complex metal cyanides, have been found to be especially effective activators. Typical data follow which illustrate the favorable influence of potassium ferricyanide upon the polymerization rate of a 75 butadiene-25 styrene mixture in a system containing 4 parts oleic acid, 0.75 part excess sodium hydroxide, 0.75 part D D mercaptan, 1part Daxad 11, and 1 part potassium persulfate: potassiuln Ferricyanide,
7%
12 hours a
16 hours 70 80
potassium Ferricyanide,
%
0.1 0.15 Q 90 0.2 Low yield of polymer, too soft, and tacky t o mill
0.005 0.025 0.05 5
Product Yield at 40”c.7 % 0.
213
Product Pield a t 40’ c., % ’ 12 hours 16 hours .. 91 70 93 74 92
Figure 4 shows results obtained by polymerizing 75 butadiene-25 styrene in a 33% emulsion containing 5 parts Palmolive soap and 0.5 part D D mercaptan, with and without excess sodium hydroxide and Daxad 11. The ferricyanide considerably accelerates the polymerization, and in this soap system the addition of 0 . 1 5 ~ o appears most desirable. Several of these products had accept-
MODIFYING AGENTS
The term “modifying agent” or “regulator” is used to designate compounds which, when present in small amounts during poIymerization, markedly increase the plasticity and solubility of the resulting elastomers. They are important tools for improving the processability of the product. Mercaptans ( S 2 ) , thiuram , disulfides (IT),sulfur (26),selenium (B), disulfides ( S I T ) xanthic substituted phosphines ( d l ) , carbon tetrachloride ( 2 ) ,a,nd various nitrogen compounds such as hydrazines ( I ) , amines (19), Schiff bases (1 I ) , nit,roso compounds ( S I ) , and diazoamino compounds (4)b, 6 ) have been used to modify diene hydrocarbon polymera and copolymers. Mercaptans as a class are probably the most useful modifying agents, and an elastomer of almost any desired plasticity may be obtained from many different monomers by using the proper concentration of a suitable mercaptan. There appears to be a direct relation between the concentration of the mercaptan and the plasticity of the resulting elastomer. Unfortunately the more plastic products may yield vulcanizates which are inferior in resilience, tensile strength, tear resistance, and other properties. Since the effect of mercaptans of various chain lengths is not identical, a study was made of mercaptans produced from twentyone different readily available petroleum oils. The data in Table I were obtained by polymerizing mixtures of 75 butadiene25 styrene in 407’ emulsions containing 4 parts oleic acid, 1 part rosin, 0.75 part excess sodium hydroxide, 1 part potassium persulfate, 1 part Daxad 11, 0.15 part potassium ferricyanide, and 0.75 part of the mercaptan (active ingredient’s). One hundred parts of the elastomers were compounded with 50 parts MPC black, 2 parts stearic acid, 2 parts sulfur, 5 parts zinc oxide, and 1.25 parts 2-mercaptothiazoline. The Williams plasticity numbers (29) of elastomers modified with different samples of mercaptans are plotted against the number of carbon atoms in the mercaptan chain in Figure 6. Although experimental variations and inequalities in yield make it difficult to draw exact conclusions, primary mercaptans containing 11 to 14 carbon atoms appear to be most effective in the persulfate-catalyzed fatty acid soap systems used. Although aromatic mercaptans were not especially effective as modifying agents, interesting results \vere obtained with certain cyclic mercaptans, such as pinene mercaptan and menthene mercaptan, and with branched-chain mercaptans, such as Sharples 3B mercaptan (20). Table I1 gives results obtained with a ferricyanide-activated 4% sodium oleate emulsion of a 75 butadiene-25 styrene mixture polymerized a t 40’ C . I n each case the tensile data show the unfavorable influence of an exces8 of mercaptan. Table I11 shows results obtained in comparing D D , menthene, and 3B mercaptan in 36% emulsions containing 5 parts Palmolive soap and 0.6 part potassium persulfate, and polymerized at 50 C. The mercaptans not only affect the plasticity of the product but also the rate of polymerization. Figure 7 shows data obtained with 40% emulsions containing 4 parts oleic acid, 0.75 part excess sodium hydroxide, 1 part Daxad 11, 1 part potassium persulfate, and 0.15 part potassium ferricyanide. N o attempt was made to exclude air from this system, and whether the mercaptan affects induction period or actual polymerization rate remains to be determined. It was considered that a combination of mercaptans might be even more suitable than a single mercaptan. Thus, it might be possible to combine the greater modifying action of 3B mercap-
INDUSTRIAL AND ENGINEERING CHEMISTRY
214
TABLEI. EFFECT O F LIERCAPTASS LfADE FROM HYDROCARBONS ON 75 BCTADIESE-25 STYRENE POLYXERIZATION, WITH 0.757, XERCAPTAN FOR 20 HOURS AT 40' C.
A v. C Chain
Oil Dependip Octane
+ P naphtha Oleum apirits HFVRI
Tydol No. 1 Deobase Perfection kerosene Fortnite LTB No. 30 white oil Bayol D Tydol No. 2 No. 9 refined Control ( D D M ) Pure No. 1 Penn No. 1 Penn No. 2 Penn No. 3 No. 40 white Penn N o . 4 No. 50 xh!te No. 70 white
7.6 8 9.5 9.8 10.9 10.9 11 11.1 11.7 11.8 12
12.1 12.5 12.8 13.1 13.3 14.1 16 18.1 19 22.5
Product Yield, % 81 85 80 85 85 89 83 90 94 92 85 90 94 93 95 92 92 92
82 78 69
Modification Fair Fair Fair Fair Good Terv good Goid Good Very good Very good Good Good Very good Tery good Very good Good Fair Fair Poor Poor Poor
Stress-Strain D a t a Stress Tensile Cure, a t 3007,, strength, min. a t 1b.I 142OC. sq. in. s qlb:/ .in. 1360 60 45 1410 60 1700 45 1080 45 1070 45 1140 1480 60 45 1450 45 1160 1420 60 45 1020 45 1280 45 45 60 45 60 45 45 30 30
1250 1220 1510 2060 1880 1330 2060 1740 2470
Elongc tion a t break, %
Vol. 39, No. 2
ineit solvent. The antioxidants may serve to termhate polymerization, but in certain caqes other aeerits or inhibitors are also added.
-
COAGULATION
510 670 450 570 620 540 500 465 525 430
h suitable coagulation process should be complete, yield a readily washable coagulum, and have no adverse effect on thk properties of the product. Coagulation of most of the emulsions discussed in this report may be brought about by 620 adding salts of bi- or trivalent metals 540 such as barium, magnesium, or alumi3210 560 num, or by the addition of sodium 3410 560 3320 500 chloride brine or acidified brine, or b y 3840 440 3010 400 cooling or heating. An acidic coagulant 3590 495 is adva:itagcous for coagulation of soap 3780 435 3860 480 laticas since it converts the soap to free 2710 315 fat'ty acid or rosin and a highly solubie salt. When practical, cooling- or heating are preferred methods of coagulation because they involve no contamination of the finished product with coagulant. For example, neoprene latices containing sodium rosinate and Daxad 11 are acidified with sufficient acetic acid t,o precipitate the rosin and are then coagulated by freezing on a rotating drum. The resulting film is washed with water to remove sodium acetat,e. I n this laboratory an acidic sodium chloride brine is commonly used t o coagulate butadiene latices made with fatty acid or rosin soaps.
t a n with the accelerating action of DD mercaptan. The results obtained (Figure 8) indicate that the single and mixed mercaptans give distinct sets of nearly parallel curves; although the mixed mercaptans have a greater influence o n plasticity a t low yields, the single mercaptans are more effective in increasing t,he plasticity a t higher yields. It is possible that the acceleration of polymerization with mixed mercaptans accounts for these results. If the rate of diffusion of the modifier to the point where polymerization is in progress is involved, accelerat'ion of polymerizaYIELD tion might explain the anomaly of less modifier being more eff ecEvery manufacturer of elastomers k n o w that the properties tive under certain conditions. 'of his product are greatly affected by the yield a t which the prodh study of the mechanism of the action of modifying agents uct is isolated. However, i t is frequently possible, by the proper offers a promising field for academic research. Some of these use of modifiers and by polymerizing a t sufficient'ly low temperamodifying agents may function by terminating polymer chain t,ure, to polymerize to a yield of 90% or better and still obtain a growth or introducing easily rupturable linkages and, thereby, result in products of lower molecular weight. Other modifying good-processing polymer which yields suihble vulcanizates. The maximum yield obtainable Jyithout adversely affecting the agents may act by preventing cross linking or by interfering vvit'h cyclization. The utility of a given compound as a modifying agent depends upon the nature of the monomer, the emulsifying agent, the pH of the TABLE II. COUPARISOS OF PINESE ASD DD MERCAPTANS emulsion, or the method of catalysis. TEMPERATURE OF POLYMERIZATION
The rate of polymerization can be increased by raising the temperature, but our general experience has shown that, the quality of the elastomer is improved by polymerizing a t lower temperatures. I n some cases freeze resistance is increased by raising the temperature of polymerization, but processability, tensile strength, and elasticity are generally improved by polymerization a t lower temperatures. STABILIZERS
Elastomers made from diene hydrocarbons must be protected from oxidation during milling and processing. For this reason it is advisable to add an antioxidant, preferably in the form of an aqueous dispersion, to the lat,ex when the optimum yield is reached ( 2 7 ) . Such a dispersion may be prepared from any antioxidant by grinding with a suitable dispersing agent or emulsifying a solution of the antioxidant in an
Polymerization Product Time, Yield, % hlercaptan Hr. 70 Kone 24 60 Sone 49 93 0.25 D D 24 88 0.75 D D 20 95 1.5 D D 20 96 1.0 pinene 22 92 20 93 2.0 pinene 20 98 4.0 uinene a O n 2-AIT (2-mercaptothiaaoline) tread
Stress-Strain _ _ _ Dataa ~ Stress Tensile Williams a t 300%, strength, ElongaPlasGicitylb:/ lb./ tion Recovery s q . in. sq. in. break, 70 337-161 2550 3580 380 369-138 1845 190 271-180 2640 3465 360 134-173 1420 3180 500 82-5 995 2215 540 230-220 1620 3610 BOO 156-145 1280 3210 530 107-100 850 2215 380 stocks cured 45 minutes a t 142' C.
_
...
TABLE 111. COMPARISON OF D D , MENTHESE,AND 3B ~IERCAPTASS Polymerisation Time, Hr. 15
Product Williams PlasticityYield, Mercaptam Recovery % 0.5 D D 86 106-24 18 90 0.5 D D 135-107 21 95 0.5 DD 144-116 0.3 menthene 19 76 102-25 0.3 menthene 21 93 130-104 0.4 menthene 19 84 90-12 0.1 3n 19 56 133-144 0.2 3n 22 71 90-11 0.3 3 B 19 74 60-9 0.3 3n 22 78 65-9 0 On tread stocks cured 45 minutea at 142' C.
Stress-Strain Dataa Stress Tensile Elongaa t 300%, strength, tion a t Ib./ Ib./ break, sq. in. sq. in. % 1510 3130 490 I670 3580 490 1760 3090 430 1420 2980 so0 2186 2840 350 1450 2640 450 1645 3380 470 1620 2900 440 1460 2840 490 1045 3065 460
INDUSTRIAL AND ENGINEERING CHEMISTRY
February 1947
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% MERCAPTAN
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A , DD mercaptan; B , No. 30 white oil mercaptan; C , pinene mercaptan
1
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65
70
75
80
85
90
95
% PRODUCT YIELD
Figure 7. Effect of Mercaptan Concentration on Polymerization of 75 Butadiene25 Styrene in Oleate Emulsion for 20 Hours at 40'
Figure 8. Effect of Yield on Plasticity of Compounds Modified with Combinations of Mercaptans 1
Ciirvp -. .No. . ..
DD %
Medthene, % 3B, %
0.3
..
0.5
..
4 0.05
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0.3
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2
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5 0.05
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*.
, simple rotation in the water bath is sufficient. If, upon removal from the water bath, the tube is suspected of containing appreciable amounts of butadiene, it is cooled to about 0" C. before being opened. After coagulation, the polymers are washed on a 6 x 2 inch (15.2 X 5.1 em.) wash mill with one corrugated roll. The washed elastomer is dried first on a corrugated mill and finally on a smooth 6 X 2 inch mill with differential speed rolls. The samples are compounded on these small mills and cured a t conventional temperatures and pressures in small presses. The apparatus used in determining the tensile properties of these samples was described by Williams and Sturgis (SO). Since elastomers containing butadiene are notoriously inferior in gum stocks, black stocks were used in compounding. The usual cure was 30 minutes a t 153" C., and the formula generally employed was:
7OL
* 2ot I 100
/
5
200
300
400
500
POLYMERIZATION TIME, HOURS
Figure 9. Polymerization Rate of Butadiene i n Oleate Emulsion at 10" C. in Presence of Octyl Mercaptan and Ammonium Persulfate I. 1 % ammonium persulfate, 2 % octyl mercaptan
11. 0.5 %ammoniumpersulfate, 1% octyl mercaptan
product is influenced not only by the character of the modifying agents added to the system, but also by the nature and amount of impurities in the polymerizables, since impurities are frequently negative modifiers. LABORATORY PROCEDURE
Glass equipment appears to be most satisfactory for use in laboratory polymerization. With materials having boiling points appreciably above the temperature of polymerization, it is possible to carry out the emulsion polymerization a t atmospheric pressure. Since butadiene boils at -5" C., it is necessary in this case t o use closed systems. It has been found satisfactory to use thick-walled Pyrex tubes (approximately 3 X 40 cm.) enclosed in holders made from perforated metal tubes and rotated end to end (35 r.p.m.) in a water bath a t the desired temperature. These tubes are closed with neoprene stoppers which have been treated with caustic solution to remove extractable material. I n filling the tubes, the water and water-soluble ingredients are placed in the tube, and the mixture is frozen by placing the tube in an acetone-solid carbon dioxide bath. Liquid butadiene and butadiene-soIuble materials are then weighed into the tube, and the tubes are sealed and warmed to the desired temperature. After the aqueous phase has been thawed, the tube can be shaken rapidly, if necessary, to form the emulsion, but usually
Elastomer Phenyl- p-naphthylamine M P C black Stearic acid
100 2
50 2
Sulfur hfercaptobeneothiaeole Zinc oxide
2 1 5
I n some recent work more active accelerators, such as 2mercaptothiazoline, were employed. With some samples tensile strength measurements were made a t temperatures ranging from -40" t o +LOOo C. Resistance to swelling in solvents is usually determined by weighing the sample in air and in water a t room temperature before and after emersion in the solvent. Several more practical methods for the determination of freeze resistance have been devhloped since this Tyork was started, but valuable preliminary information was obtained by using a modification of the T-SO method described by Gibbons, Gerke, and Tingey ( 8 ) . I n this modification the temperature a t which each 10% retraction occurred is reported; that is, a T-10 of -40" C. means that a sample stretched 240% of its original length when frozen a t -70' C. and then released to allow free retraction, retracted 10% of the elongation when warmed t o -40" C. The T-20 is the temperature a t which it retracted 20%, etc. The hardness (Shore durometer Type A) and the Schoppcr rebound were measured with a pile of three slabs. Elastomers which gave interesting results in those preliminary tests were evaluated further by conventional rubber testing methods. ELASTOMERS FROM BUTADIENES
The sodium-catalyzed polymerization of 1,a-butadiene was used extensively in formulating the numbered Bunas in Germany and SKA and SKB in Russia (d6). Less attention has been given to the emulsion polymerization of butadiene alone, and it is generally assumed that the presence of another polymeriaable compound is essential in order to prevent excessive cross linkage or to give the preferred 1,4 addition and obtain the best products.
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
216
I
I
I
I
I
I
I
The polymerizatiou oi mixtures of l,3-butadiene and 2,3dimethyl-1,3-butadiene produces elastomers 1% luch are superior in stress-strain propertie. to thow obtained from butadiene alone under similar conditions:
I
I
; I
Butadiene,
Poh'merlZation TeOrnE:, Time, hr. 50 67 30 18 30 18 30 18 90 30 60 16
c/o
10 10 20 30 60 60
I
-70
I
I
-60
-50
Figure 10.
I
I
I
-40 -39 -20 TEMPERATURE ,OC.
1
1
-10
0
+I0
Freeze Resistance of Butadiene-Dimethylb u t a d i e n e Elastomers
Curve No. 1,3-Butadiene, % 70 2,3-Dimethyl-l,3-butadiene,
I 100
I1 40
I11 30
IT.
\ 10
VI
20
60
70
80
90
100
The present commercial processes do involve the use of another polynierizable compound with the butadiene, but it is possible to improve the elastomers obtained from butadiene alone by suitable emulsion technique. However, to obtain high-quality butadiene polymers in emulsion, it is necessary to polymerize a t lower temperatures than are commonly used commercially. The following data show the results of tests on straight butadiene polymers made in a 4y0sodium oleat'e emulsion containing persulfate and octyl mercaptan, and polymerized at. 10' C. : Ammonium Octyl PersulMercapfate, % tan, 7% 1 2
66
Sq. In. 820 630 850
...
Tensile Strength, I,b./Sq. I n 1500 2940 2180 1450
30 46 62
480 820 1130
1900 2090 1600
Product Yield,
"70
38 48
SO 0.5
1
Stress a t
3OO'Z, L b . /
Elongation a t Break, 95 420 640 460 250 620 460 350
I n both systems the product isolated a t an intermediat,e yield is superior to t h a t a t either the highest or the loxest yield. As Figure 9 shows, the polymerization rate is far slower than t'hat used in commercial systems, but it is possible to modify the sybtern so as t o obtain faster polymerizat,ion rates. For example, a 92% yield was obtained in 64 hours a t 10" C. by using a syst'em containing 25 parts oleic acid, 0.5 part excess sodium hydroxide, 1 part Daxad 11, 0.5 part sodium persulfate, 1 part D D mercaptan, 4 parts methanol, 0.1 part potassium ferrocyanide, and 200 parts water per 100 parts butadiene. The product, compounded in a typical channel black stock, gave a vulcanizate having a tensile st'rength of 2500 pounds per square inch and a n elongation at break of 650%. This shows that high yields of good quality butadiene polymers are possible. Isoprene gave reasonably good polymers, although in general they were inferior to those from butadiene. ' A 907, yield of isoprene polymer was obtained a t 30 C. and it gave vulcanizateb with a tensile strength of 1950 pounds per square inch a t G O ? { elongation. Practical road tests indicate that, in spite of these comparatively poor tensile properties, a tread of polyisoprene would give more than half as much service as a Grade A rubber tread. 2,3-Dimethyl-l,%butadiene gives better milling elastomers than either butadiene or isoprene, but loggy vulcanizates which have a greater tendency to freeze. They have good tensile strength, as indicated by the following data obtained viith polymers formed in a n alkaline oleate emulpion containing persulfate and cured 30 minutes a t 153 O C.: PolYmerization Tfmp., Time, C. hr. 4 100 60 65 60 17 30 90
Product Yield,
%
50 100
72 72
Stress a t 30076,Lb./ Sq. In. 1410 1900 1810 2040
Tensile Strength Lb./Bq. 1;. 2720 2900 3030 2660
vel. 39, No. 2
Clongation a t Break, 70 460 390 420 350
Product Yield.
7%
105 76 81 82 88 86
Stress a t 300%, Lb./Sq. I n 1810 1610 1700 1920 1410 1470
'Tens~le Strength, L h /Sq. Jn. 2770 2800 2940 2580 2550 1900
Elongation at Break. % 390 43a 430 360 430
360
The freeze resistance of these dimethylbutndiene-butadiene copolymers, as indicated by retraction during gradual VI arniikg in the T-50 apparatus, shows a definite improvement as the batadiene content is increased. This is shown by t>he curves of Figure 10. Even more freeze-resistant elastomers can be obtained by polymerizing mixtures of isoprene and butadiene (Figure 111). Tensile data follow on e1ast)oniers cured 30 minutes a t 153" C:. : Butadiene,
%
n
Tso-
prene,
Dic
Polymerization Time Product a t 35' C . , Yield, 70 Hr. 64 35 112 69 64 54 112 87 61 64
Tensile Strength, 1.b.ifiq. I n .
i2longation a t Break, V0
1330
41 n
...
These results were obtained with a system containing 4 p:%rt,e oleic acid, 1.5 parts ammonia, 1 part Dnxad 11, 1 part amnionium persulfate, and 2 parts octyl mercaptan. hlilled blends of the separately formed polymers from butadiene, isoprene, or dimethylbutadiene do not show the superiority in freeze resistance of the corresponding copolymers. This difference in freeze resistance is believed to be an indication of the formation of polymers which contain in n single chain, units of both polymerizing monomers. This work has served t'o demonstrate that' high quality polymers can be made from diene hydrocarbons alone by polymerization in emulsion, and t'hat some advantage may be expected from eopolynierizat'ion of different hydrocarbons. The emulsion polymerization of these diene hydrocarbons is worthy of more det,ailed investigation, and the development, of t'he proper system may result in an elastomer superior. t o GR-S for general use. COPOLYMERS OF BUTADIEXE ASD VIKYC COMPOtJ3DS
Although good elastomers can be made from butadiene alone, thus far it has been eabier to make n good qualit,? product, from mist,ures of butadiene with other polymcrizable compounds. The first ~yorlcwas that of Tschunkur, >leisenburg, and Bock: using htyrene and vinyl naphthalene ( I O ? 28). > I m y other types of compounds copolymerizable with but'adiene were studied later hy various investigators, but it' is not, possible t,o givc here a complpte bibliography of the extensive literature on the subject. I n general, the second polynierizable components are vinyl compounds vihich contain an act'ivatiiig group such as a second vinyl, a nitrile ( l a ) , a carboxyl ( I O ) , or a phenyl group. ;ictivat,ion may also be accomplished by unsymmetrical substitution of two. or more halogen atoms on a double-bonded carbon (25'). Many of these vinyl compounds have been investigated, but only a few have given sufficiently attractive products or are suficiently available commercially to be considered for the manufacture of' synthet,ic rubbers. Table 11' summarizes the properties of butadiene copolymers with vinyl compounds having different activating groups. I n this series of t,ests the second monomer !vas used on an equimolar rather than an equal weight basis, the ratio being 4.5 moles of butadiene per mole of the second vinyl compound. The mixed monomers were polymerized in an emulsion cont,aining 5,.
INDUSTRIAL AND ENGINEERING CHEMISTRY
February 1941
217
OF BUTADIENE COPOLYMERS WITH VARIOESMONONERS TABLE IV. PROPERTIES
(Struoture is CHz=CRRi) MethMethyl AcryloacryloMethnitrile nitrile acrylate H CHs CHa CN COiCHr CN 18.6 22.4 30
NO Second Monomer R group Ri group 2nd monomer, % by wt.
Hours a t 30' C. Product yield, yo
65 55
Butyl Methyl Meth- a-Chlora-M e thylacrylate acrylate Styrene styrene CHa C1 H CHn CO&He COzCHs CaHs CsHs 30.8 33.6 38 34
Polymerization D a t a 40 65 100 93
66
88
48 90
50 87
88 83
90 85
620 2900
1900 2290
650 3220
350 2410
'
Stress-Strain D a t a (Cured 30 Min. a t 141' C.) Tested a t 2b0 C. Stress,at 300oJ0,Ib./
900 2320
sq. in.
Tensile, Ib./sq. in. Elongation a t break,
%
470
Tested a t 70' C. Tensile, lb./sq. in. Elongation at break,
70
400-500
450
600
650
340
650
800
1030
1330
1470
650
2010
1700
250
150
260
470
590
200
620
860
Kerosene Absorption (48Hr. a t 100' C.) 42 62 135 203
64
150
195
Freeze Resistanoe -40 -33 -46 -30 -23 -37 -23 -11 -26
I
I
I
I
-55 -46 -36
-12 0 +6
-49 -41 -32
-47 -38 -29
and 30 parts of second component in an alkaline sodium oleate system with a suitable catalyst, usually a persulfate, and to agitate the emulsion a t 30' or 40' C. for 65 hours. The emulsion was then treated with an antioxidant and coagulated. The coagulum was washed on a mill with one corrugated roll and milled to constant weight. I n some cases, indicated b y j , an acid system was used with C-cetylbetaine as emulsifying agent. Many of these experiments were carried out before the present modifiers or catalyst activators were developed. The products, therefore, do not necessarily represent the best that can be obtained from the particular compounds. *
parts oleic acid, 1.06 parts sodium hydroxide, 1 part Daxad 11, 1 part ammonium persulfate, 0.5 part octyl mercaptan, and 116 parts water. Comparison with the results obtained on butadiene alone shows that the addition of the second monomer increases the rate of polymerization in all cases. When the second monomer contains a nitrile group, the rate is further increased by the introduction of alkyl groups. The kerosene resistance is increased by the presence of chlorine or, especially, nitrile radicals. The introduction of additional alkyl groups tends t o decrease the kerosene resistance, and the greater the chain length of the alkyl group, the greater the loss in kerosene resistance. The introduction of a methyl group decreases the freeze resistance, but the elastomers containing the butyl group are more freeze resistant than those containing the methyl group. I
740 2720
1160
- 65 - 34 -21
C. C. C.
1380 2970
850
>zoo
Vol. increase, %, T-10, T-50, T-80,
2000-2500
I
'
/'
820 I
IO
-70
-60
-30
-50
-40 TEMPERATURE,
I
OC.
100
...
I1 75 25
I11 50 60
IV
. ..
100 ~
The compounding formula was as follows: copolymer 100, phenyl-p-naphthylamine 2, stearic acid 2, zinc oxide 5, MPC black 50, sulfur 2 , and mercaptobenzothiazole 1. Table V summarizes data pertaining to the polymerization of mixtures of butadiene with a number of other polymerizable compounds. I n testing a new compound, the general procedure wa8 to form a 40y0 emulsion of a mixture of 70 parts butadiene
I
I
I
I
50 60 70 80 IN MONOMER MIXTURE
90
Figure 12. Relation between Composition of Monomer Mixture and Copolymer for Butadiene- Acrylonitrile
-20
Figure 11. Freeze Resistance of Butadiene-Isoprene Elastomers Curve No. 1 a-Butadiene, 70 Goprene, %
I
20 30 40 Sb ACRYLONITRILE
The second monomer is considered to have inhibited polymerization when the product yield was 25% or less of that which would have been obtained from the same amount of butadiene alone. Product yields 75-110y0 of that to be expected from the butadiene are considered normal; lower yields indicate retardai tion, and higher yields acceleration. I n all cases where polymerization was accelerated, copolymers are believed to have been formed. When possible, this was confirmed by determination of a characteristic element such as chlorine or nitrogen. Some combinations with normal or even retarded polymerization rates gave products which contain appreciable amounts of a second monomer.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
218
TABLE V.
i
1
/
5oi 1%
METHYL METHACRYLATE
20 80
X,
70
40
60
A
-
50
60
50
40
70 30
%BUTADIENE
Figure 13. Effect of lllonomer Ratio on Yield of Elastomer for Butadiene-Methyl &lethacrylate in Ammonium Oleate Emulsion
These results indicate that minor changes in the structure of the second monomer can have a pronounced effect upon its ability to form an interpolymer with butadiene, possibly as a result of differences in the firmness of the electron bondage. For example, high yields of elastomer were obtained from mixtures of butadiene and 2-nitro-2-methylprop~-lmethacrylate; mixtures of butadiene and 2-nitrobutyl methacrylate failed t,o yield significant amounts of elastomer in either acid or alkaline systems. A similar influence of struct,ure on ease of formation of polymers is found in the case of crotonic anilide and niethacrylic anilide. Mixtures of crotonic anilide (CH8-CH=CHCOSHC,H5) aiid butadiene gave only small amount's of cheesy product, in either acid or alkaline emulsions : butadiene and methacrylic anilide [CHz=C(CH,)CONHCsH,] gave high yields of elastoifier.
Vol. 39, No. 2
ELASTOMERS FROM BUTADIENE WITH VINYLCOMPOUXDS
Second Monomer Acyclic monoenes 1,l-Dichloroethylene 1-Bromo-1-chloroethylene 1-Fluoro-1-chloroethylene cis-l,2-Diohloroethylene trans-l,2-Dichloroethylene 1 12-Trichloroeth lene l~l~2-Trifluoro-2-c%loroethylene 1,1,2,2-Tetrachloroethylene 2-Chloro-1-propene 3-Chloro-1-propene 2-Methyl-3-chloro-1-propene 1,l-Dicliloro-2-methyl-l-propene 1,1,3-Trichloro-2-methyl-l-propene 2,4,4-Trimethyl-2-pentene Acyclic dienes I-Methvi-1.3-oentadiene
Chloro-2-methyl-1 3-butadiene 2-Chloro-3-methyl-l:3-butadiene 3-Chloro-2 ,4-heptadiene 2,3-Diohloro-l,3-butadiene 1,2,4-Trichloro-l,3-butadiene I 1,1,2,3,4-Pentachlor-l,3-butadiene Z-lIethyl-1,3-pentadiene 3-Chloro-2,5-dimethyl-l,6-hexadiene 1,3-13ichloro-2,4-hexadiene 3-Chloro-1,3,4,5-hexate~raene 5,6-Dichlorohexa-l-en-3-yne 3,5,6-Trichloro-1,3-hexadiene 2,5-Dimethyl-l,3,5hexatriene Acyclic hydroxy compounds Allyl alcohol 2-Chloro-2-propen-1-01 l-Hydroxy-3-chloro-2,4-hexadiene Dimethylvinylethynylcarbinol 2-Ethoxy-1-butene 3-~Iethoxy-2-chloro-1-propene 3-~lethoxy-2-methyl-l,l-dichloro-lpropene 1-Divinyl ether 2-Chloroallyl ether Isobutyl vlnyl etherf 2-Methyl amyl vinyl etherf Divinvl sulfide
Polymerization Rate"
Mill Appearanceb
Ace6 Norma Inh Ret Ret Normd Rete Ret Ret Rei, Ret Norme Ret A'orm
Fair Good Soft Tough Tough Tough Coherent Tough Thready Coherent Soft Flaky Stioky Poor
Korm Koram Ace Rets Acce ACCE Inh Ace* Norm Inh
Good Good Good Fair Crumbly
ilcce
Re? Acce Ink Inh Inh A-orme Ace' Inh Inh Inh Inh .icce Inh Rete Inh Ret Ret e Ret Ret Inh
Monorarboxylic acids Arrvlnnitrile ~.~ hIetl(i&iZtrile a-Chloroacrylonitrile a ,p-Dichloroacrylonirrile 3-Cyano-1-propene/ I-Cyano-2-butene 2-Cyano-1-chloro-1-propene/ 2-Cyano-3-chloro-1-propenel I-Cyano-3-chloro-1-propene
1-Cyano-2-methyl-1-propene Z-Cyano-4-1iiethyI-l,3-pentadiene l-Cyano-1,3-butadiene 2-Cyano-1,3-butadienel l-Acetoxy-1,3-butadienei 2-Aeetoxy-1,3-butadiene l-Acetoxy-3-chloro-2,4-hexadiene 1,l-l)ichloro-2-methyl-3-acetoxy-lpropene Vinyl formate S'inyl acetate Vinyl chloroacetatef Methyl methacrylate E t h y l methacrylate n-Propyl methacrylate n-Butyl methacrylate Butyl methacrylate n-Octyl methacrylate Vinyl methacrvlate Allyl methacrylate Methallyl methacrylate 3-Chloro-2-butenyl methacrylate 2-Kitropropyl methacrylate
Inh Inh Inh AceC Norme Inh Rec Ret Ret Ret Inh Norm Acc' .ICC#
ACCP Ace6 Inh Inh Inh Inh Inh
Fair Good Poor Fair Fair
Fair Fair
c
vG Fair
Po;,r
Poor
vc;
Poor
Fliky-' Fair
Fair Poor
P;br
...
...
...
VG
...
. I .
Gddd ' . . I .
Good
....
.,.,
Gddd
'
Good Soft
Poor
Poor POOP Good
Poor Fair
.. ,. .. ... ...
...
,..
... )..
Fair Poor
...,
Slime
.
I
Fair Fair
...
...
.
,.*
.(,
. . I .
VG ,...
VG
Gddd
....
...
Tender Fair Soft
....
.... ..
..(.
....
.
,
Crumbly
Poor Poor Poor Poor
...
...
I
.
Good
..(
VG
...
Poor
Poor Good Fair
. ~ .
...
Poor Poor
Poor Poor
...
.".
...
._. ...
...
n . .
i...
. i ;
..,
Good Crumbly
V'G. Poor
VG Poor
Tender
Poor Poor Poor Poor
Poor Fair VG Fair
Poor
Poor
~obr
Good Coherent Dry Good Sirupy
Good VG Good
VG
Good Good Poor Poor
...~ .
.
I
.
Fair Soft
...
...
.I..
..i
....
Sirupy .
.
I
.
Soft Powdery
Crumbly
ACCt Ace Ace5 ACCO Aces Ace* ACCB AceC Ame
Good Good Good Good Good Tender Good Good
Inh
17
... Fair ...
Fair Fair
Ret Inh Inh
Norma
...
Poor
... 1
.
.
;.. ... ...
... ,
.
.
.
..,
... Fair Poor
Fair
Good
Fair
Good
..
...
;
I
. I . .
gEzd
i
i . .
Good Poor
.. .. ..
Inh
vG
Fair Poor
....
.~~~..
Poor Fair Poor Fair
Poor
I~
Chloroaoetonel Crotonaldehyde a-Chlorocrotonaldehyde 1-Buten-3-one (methyl vinyl ketone) 2-Chloro-1-butan-3-one Mesityl oxide Phorone Divinylformal 1,l-Diethoxy-2-propene Dichlorovinyl ethyl e t h e r i Biacetyl Hexyl ketone dimerf
Good
...
VG Good
Poor Poor
O.x~. o coninminds . .
The polymerizatioii of mixtures of diflerent polymerizable materials may result in the formation of elast,omers consisting of long chains, each of which contains a variable number of units of each of the monomeric materials; or it may result in the formation of a mixt'ure of polymers, eac,h made up of units of only one of the polymerizable compounds. A given elastomer may contain mixtures of bot'h types of polymers. I n this laboratory it has been the custom to refer to the first class of elastomers as interpolymers and to the second as copolymers, although the term copolymers is used commonly to cover both classes. It is often difficult to determine precisely which type of polymer is present. I n some cases it is possible to determine t,he presence of a particular type by visual examination, physical separation, and analysis. Ti1 other cases simple ext>raction with solvents and analysis may serve to show the presence of different types of products. Comparison of the physical properties of t,he products formed by polymerization of mixtures with those formed by mill blends offers some indication of the presence of h i e interpolymers. Freeze resistance is believed to be a significant means of determining the difference between true interpolymers and mixtures. In cert'ain cases determination of th,e index of refract,ion gives valuable informa,tion.
Good Poor
Fair Good
..., STRUCTURE OF COPOLY.MERS
Tensile ClongaStrengthC tiond
....
...
VG Good Good Good Good
Poor
Poor Poor Poor
Poor
rib'
Fair Good Good Good Poor Poor Poor Poor
Poor
..
February 1947
INDUSTRIAL AND ENGINEERING CHEMISTRY
TABLE V. ELASTOMERS FROM BUTADIENE WITH Second Monomer ,Monocarboxylic acids ( C o n t ' d ) 2-Nitro-2-methyl propyl methacrylatef 2-Nitrobutyl methacrylate Ethylene glycol monomethacrylate Methoxy. methyl methacrylate E t h y l thiomethacrylatef
Polymerization Rates
VINYL COMPOUNDS
Mill hppearanceb
Tensile Strengthc
Elongationd
Good
VG
VG
Good Good
Fair Poor
Fair VG
Polycarboxylic acids Dimethyl fumaratef Diisobutyl fumarate Diallyl fumarate Dimethallyl fumarate Di(3-chloro-2-butenyI) fumarate 1,Z-Dicyanoethylene 2-Methyl-2-nitropropyl fumarate1 Dimethyl maleatef Dimethallyl maleate Diethyl methylene maleatel Diisobutyl maleate E t h y l cyanoacetate a-Cyanosorbic acid/ Methyl a-cyanosorbatef 2-Methyl-2-nitropropyl maleatel Di-2-nitrobutyl fumaratef
Acce 4cce Acce Acce Acc: Acc Acoa Ret Acce Ret ACCe Inh Ret Inh Aace Inh
Good Tacky Crumbly Crumbly Flaky Crumbly Fair Soft Crumbly Gqod Fair
Good Poor Poor
VG Good Poor
Poor Good Good
Poor Poor Good
Hydroxy carboxylic acids Diallyl carbonatel Dimethallyl carbonatel Acrolein cyanohydrin acetate 3-Cyano-3-acetoxy-1-butenel Cyanomethyl methacrylate P-Cyanoethyl methacrylstef Methacry1 isothiocyanatef Methacrylurea Diethoxymethylurea f Vinyl thiolacetate Dimethyllyl methallyloxy succinate!
Norm Ret Inh Rete Acc Ace" Inh Acce Norm Rete Ret
Po
Amines N-Allyl maleic half-amidel Inh Monomethacrylurea Iiorme AT-Dimethylcrotonamide Rete Dimethallylamine/ Acc Inh Methacry1 dimethylamide Inh N-Methyl maleic monoamide N-Butyl maleic monoamide Ret Ai-Methyl methacrylamide/ Norm N-Stearyl methacrylamidef Acoe Methallyl isothiocyanate Inh Dimethylaniine hexylmethacrylamide I n h iV-(b-Dimethyl aminoethsl) methacrylamide Acc8 Dimethylaminoethyl methacrylate/ Acce Diethvlaminoethvl methacrvlatef AccB 2-Cvs:?oiaJ>r , I ) V ~r n e r l i a c r y h i d e f Inh 2-P;opeiie ph ,;$xmic bisdiiitat hylamide Acc Isocyclic compounds Methylenecyclohexane (3- Pi nene Dipentene Cvclowentadienef p-kethylstyrene a-Methylstyrene p-Methyl-a-meth ylstyrene a-Chlorostyrene 2,5-Dichlorostyrene 0-Ni trostyrene! 3-Wethyl-(3-nitrostyrenef 3-@-Dinitrostyrene/ m-Nitrostvrenef
Isocyclic hydroxy compounds a-Ethoxystyrene Cinnamvl alcohol p-Methoxy-8-nitrostyrene Cyclohexyl methacrylate Pentachlorophenyl methacrylate
Ret Norm Norm Norm Acce Acce Acce Acc* Inh Inh Inh Inh Inh Inh Acce Ret Acce liorme
Inh Inh Inh Acca Inh
.... ....
Resinous
.... ....
... ...
...
... ,..
... ...
...
...
...
Fair Poor
VG Poor
FAG
Poor
... ...
I
.
.
...
...
... .
I
.
Poor Poor
Poor Poor
Crumbly Poor
Good Poor
Fair Poor
Cr L Z i l y Poor
FPoor Z~'
Poor Poor Good Poor
.... Good
Good Poor
....
Waxy Good Poor Soft
....
Soft
Poor Poor
... Poor Fair Poor
...
Good .
t
.... . . I .
Flaky
Good Tender Fair Poor Fair Coherent Fair Fair Dry Good
....
....
Poor Poor
...
Poor
Isocyclic oxo compounds P-Carvone Inh Sticky 1-Phenyl- 1-buten-3-one! Acce Good Good 1,3-Diphenyl-l-propen-3-one l Accs l-Phenyl-5-chloro-l-penten-3-one Inh 1,5-Diphenyl-l,4-pentadien-3-one Acce Fair 1-Phenyl-1 3-hexadien-5-one Inh l-Phenyl-5~methyl-l,4-hexadien-3-one Ame Gddd Cinnamic aldehyde-methylamine Inh l-(p-Nitrophenyl)-l-buten-3-onef Inh .... 1,4-Diphenyl-2-butene-1,4-dione Acoe Crumbly (Continued on page 810)
.... .....
...
Poor
Poor
Poor
Good Good Poor Poor VG VG VG VG Good VG
...
Poor Poor Poor VG VG VG VG
Poor VG
...
Fair Good VG
..I.
...
Poor Poor Poor
Cri'nibly Good Good , Good
.... .... Good
... ...
Poor Fair
....
....
. I .
Poor
Poor Poor
...
... ... ...
... ... ... ... ... .. .. ..
VG VG VG
... ...
... ...
Gddd
Good
...
v'd .
...
Good
G'o'o'd Fair
G'o'dd
G'o'o'd
Fair
Fair
... . . t
...
Fair
.
Relative Solubility
...
G'do'd
. .........
....
'
.. .. .. ...
Poor Good
v'G
I
Poor
The presence of an element, such as nitrogen or chlorine, which can readily be determined quantitatively is frequently helpful in studying copolymers. For example, a butadiene-acrylonitrile copolymer was dissolved in benzene (5% cement) and, a t 40 C., diluted with 58 grams ethyl alcohol per 100 grams cement. ' The mixture was cooled to 28" C. and, upon standing, separated into two lagers. The solvents were removed by evaporation, the product of higher molecular weight was redissolved, and the treatment repeated. The original elastomer was separated into four fractions of different solubilities. The data obtained with these fractions indicate there is comparatively little difference in the chemical composition of the various fractions, Le., the product is essentially a true interpolymer. The least soluble fraction does contain slightly less nitrogen than the most soluble fraction. The viscosities of cements made from these fractions, as determined in a Gardner-Holdt bubble tube, indicate a wide difference in molecular weight:
(COnt'd)
Acee Inh Inh Acce Ace e
...
...
...
Fair
219
.
. 1 2 3 4
yo of Original loo 23 23 18 36
iiitrogen Content, % ' 7.31% 7.30 7.24 7.34 6.99
Bubble-Tube Visoosity of 9.5% Benzene Cements, See. 9 2 3.7 12 300
Results obtained by polymerizing, in both acid and alkaline systems, a number of different mixtures of butadiene and acrylonitrile indicate that the composition of the copolymer is chiefly dependent upon the composition of the monomer mixture even if the polymerization rates vary widely. These data (Figure 12) indicate a linear relation between the compositions of the monomer mixture and the resulting copolymer. According t o these results, a monomer mixture containing a little over 35y0 acrylonitrile should give a quantitative yield of elastomer 'of the same Composition as indicated by the insection of the dotted line for a uniform copolymerization and the experimentally determined relation. Copolymers made from higher butadiene-acrylonitrile ratios contain a higher acrylonitrile content than the monomer mixtures; those made from low butadiene-acrylonitrile ratios contain a lesser portion of the nitrile. While this generalization holds for this particular combination of monomers, it is not necessarily applicable to all other combinations. In fact, with some mixtures one monomer may polymerize t o yield a product containing little or none of the second material. PROPERTIES OF CERTAIN COPOLYMERS
The proportion of the second monomer in the starting mixture markedly affects both the rate of polymerization and the properties of the resulting polymer. Improvements in certain properties obtained by a selected ratio of monomers may be accompanied by deficiencies in other .properties. For example, a higher retention of tensile strength at elevated temperatures may coexist with poorer freeze resistance (Table VIII). Certain of the second monomers listed in
INDUSTRIAL AND ENGINEERING CHEMISTRY
220
TABLE V. ELLSTOVERS FROM BUTADIESE TT-ITHVIKYLC O ~ ~ P O T J(Cont'd) KDS Second Monomer Isocvclic carboxvlic arids LCyanostyreGe @-Cyanostyrene , 1-Cyano-4-phenyl-1 3-butadiene l-Cyano-l,4-diphen;l-l,3-butadiene Vinyl benzoatef Ethylene glycol dicinnamate Methyl-4-nitrocinnamate Methyl a-cyano-@-phenyl acrylate 1-Phenvl-4-cvano-4-carboethoxv-1.3butaaene " Methyl-o-cganocinnamate 59' isomer 92' isomer "
Polymerization Ratea Ret Acce Sorm Ret Inh AooC Ret Aced
Rlill Appearanceb Waxy-brittle
....
\VaxJ*lGittle Noncdhtkent Soncoherent
....
Tensile ElongaStrengthC tiond
...
Fair Poor
... ... ...
pbbr
...
Fair Fair ,..
...
...
Poor
I
Isocyclic amines AminostyreneI Crotonanilide Methacry1 anilide Blethacryl p-nitroanilide h l ethaoryl-m-toluidide o-Cyanocinnamic anilide, trans 9 (m.p. 186-187° C.) o-Cyanooinnamic anilide, czs I (m.p. 130-135O C.) --Cvanocinnamic anilide m-nitroanilide hf ethacryl p-hydroxyanilide Rlethacryl p-aniside Heterocyclic compounds 2-Vinylpyridine 5-Ethyl-2-vinylpyridine ?(rr-Furyl) acrylic acid Fury1 acrylic acid Methyl p-fury1 acrylate Allyl p-fury1 acrylate Furfuryl methacrylate ?-Fury1 acrylonitrilef Ethyl a-cyano-8-furyl acrylate Furoic anilide 0-Nitrofurylethylene 1-Furyl- 1-buten-3-one l-Furyl-5-methyl-l,4-hexadien-3-one l-Furyl-3-phenyl-l-propen-3-one Chlorovinyl ethylene oxide Ethylene sulfide Propylene sulfide Indole 2-Methylindole A'-Methyl maleicimide 'V-Butyl maleicimidef A'-Cyclohexyi maleicimide A'-Methyl citroconicimide ?v--Allyl maleicamide iV-Tinyl succinimide Terpene peroxide
Acc"
Good
Fair
Good
Norm Acce
Good Good
Poor Good
Fair Good
Inh Inh
Powder Cheesy Flaky
G'0'0'd
VG '
Hard
Good
v'G '
Norm e
Fair
POOT
POOT
Rete Iiih
Fair
Poor
Poor
Bote
Inh Rete
....
Aco Aoc Inh Inh Acce ACCE Acce Inh Inh
Norme Inh ACCS Inh Acee Inh Inh Inh Inh Inh Inh Ret Ret Ret e Inh Inh Inh
.... Good Good
....
Good Dry Good
....
Poor
...
...
....
Inh Inh
...
t . .
...
,..
... VG VG
..*
Good Poor
VG VG
...
G'o'o'd Poor
1 .
.... ....
Good .I.. Good
l~owde;~ Plastic
Good
... ...
G'ddd
Good ,..
G'ddd
... ...
...
....
.... ....
Soft Good Good Powder
....
...
Fair
.. .. .. ...
.
.
VG
I
... ... ...
Vol. 39, No. 2
Data obtained in determiiiing properties, such as freeze resist'ance, kerosene absorption, Schopper rebound and Shore durometer hardness, of vulcaiiizates of elastomers formed from mixtures of butadiene or isoprene with methyl methacrylate or butyl methacrylate are pIotted in Figures 14 t80 18. Butyl methacrylat,e is superior to methyl methacrylate in imparting freeze resistance and resiliency, but' methyl methacrylate tends t o give harder, more oil-resistant vulcanizates. The T-10 results indicate that the t'endency of the polymer to become brittle a t very lox temperatures increases with increasing methyl methacrylate content'. The T-50 and T-80 results indicate that the presence of small amounts of methyl methacrylate actually improved the retention of "snap" a t intermediate temperatures. Butadiene is superior to isoprene in imparting freeze resistance. oil resistance, and resiliency. METHYLVINYLKETOSE COPOLYNERS.Mixtures of butadiene and methyl vinyl ketone can be polymerized to give good yields of copolymer@ whose vulcanizates exhibit to an unusual degree B combination of kerosene and freeze resistance (Table VII). I n fact, for a given freeze resistance they are superior to butadiene-acrylonitrile polymers in kerosene resistance. These particular elastomers were made by polymerizing a t 30" C. in a myristylamine I C H ~ ( C H . J ~ ~ C H ~ S H T ] - ~ ~ ~ ~ O chloric acid system catalyzed with ammonium persulfate and Containing no modifier; good elastomers have also been made in oleate, or preferably Lorol sulfate, systems. Methyl vinyl ketone is a strong lachrymator, and it is difficult, to obtain a vulcanizate of its diene copolymerE free from the characteristic odor.
DIYETHYLVINYLETHYNYLCARBIXOL IWTER~~OLY-
(CH,), COH-C=C-CH=CH2 gives excellent elastomers when interpolymerized wit'h butaa Acc = accelerated: Norm = normal; R e t = retarded: Inh = inhibited. diene. Typical data (Table VIII) were obtained Good means the band on the mill was smooth and unbroken: Fair, the band was someKhat broken and rough, Poor, the band was difficult t o maintain. Certain of the poorwith a system containing 4 parts oleic acid, I milling polymers are desbribed more specifically. Poor, less than 1500 lb./sq. in.; Fair, 1500-2000 Ib.; Good, 2000-3000 lb.; Very Good, part Daxad 11, 0.5 part sodium hydroxide ir above 3000 lb. excess of that required t'o neutralize the oleic d Poor, less than 250%; Fair, 250-350%; Good, 350-450%; Very Good, above 450%. Product contains a preciable amounts of second monomer. acid, 1 part potassium persulfate, 0.05 part I Polymerized in acifemulsions. potassium ferricyanide, and 1 part DD mercaptan. The data shox that good copolymers . . are obtained with 15 to 30 parts of the rarbinol. Table V, such as methyl and butyl methacrylate ( d 4 ) , methyl It is believed to be significant that the heat build-up reaches 8 vinyl ketone ( 1 5 ) , dimethylvinylethynylcarbinol (dd), in comminimum when 20-30 parts of carbinol are used. Thra iP bination with butadiene and isoprene, have been studied in bGtadiene-30 carbinol copolymer is especially interesting; st more detail, and some of the results are described in the followapproximately the same state of cure (judged by modulus) as ing sections. The copolymers were compounded according to the 10 and 15% carbinol copolymers, the tear resistance, heat the basic fox mula: copolymer 100, phenyl-p-naphthylamine 2, build-up, and tensile strength at 70" C. reach an optimum. stearic acid 2, zinc oxide 5, MPC black 50, sulfur 2, mercaptoThe possibility of using three or more monomers in forming an benzothiazole 1. elastomer is intriguing and susceptible of an infinite number of NETHACRYLATE CoPoLYxms. When mixtures of butadiene and methyl methacrylate were polymerized in an ammonium oleate emulsion containing 0.8 part excess ammonia and 1 part TABLEVI. PROPERTIES OF BUTADIBNE-METHYL ammonium persulfate, the polymer yield obtained in 40 hours a t METHACRYLATE ELASTOMERS 30' C. was found to increase considerably with increase in methyl (Cure, 30 minutes a t 153" C.) methacrylate-butadiene ratio (Figure 13). The variation in Tensile ElongaKerosene % Methyl Stress a t Meth300%, Strength tion a t Absorption=, properties with monomer ratio is shown by the data of Table VI. Lb./Sq. In. Lb./Sq. 1 .; Break, % ' Vol. F acrylate I n a practical road test a tire made from a 70 butadiene-30 methyl methacrylate elastomer was only slightly inferior to a high grade rubber control. These polymers made with methyl methacrylate compare favorably with those made with styrene in vulcanizate properties, and are actually superior in process0 Inorease in volume in 48 hours a t 100°.C. ability and oil resistance.
....
IIERS.
February 1947
INDUSTRIAL AND ENGINEERING CHEMISTRY I
I
I
I
6
10-
221
t
-
9
0-10-
9-20-
-z ,-30-
w 140
I
c -40-
9
-50-60
-"
,/
//'
IO 90
I
I
30
40
,
50
60
I
1
I
70
80
40
90
50
30
Figure 14. Freeze Resistance of Butadiene-Methyl Rlethacrylate Elastomers as Determined by T-50 Method
1
I
I
b
40
50
€0
L 70
% METHACRYLIC ACID ESTER
Figure 16. Effect of Methacrylic Acid Esters Mixed with Butadiene and Isoprene on Kerosene Absorption of Vulcanized Copolymers (Cured 30 Minutes at 153" C.)
70
60 40
50
30
INITIAL MONOMER
% METHYL METHACRYLATE 40 20 30 70 60 80 % BUTADIENE
60
-----
Butadiene copolymer Isoprene copolymer
r
,
mixtures of butadiene and many other polymerizable compounds. Several of these are superior to those made from butadiene and styrene in particular respects; but considering availability and cost of raw materials, this work has not uncovered any butadiene copolymers TThich would have been preferred over those made with styrene or acrylonitrile in the period of national emergency. The possibility of obtaining high grade elastomers from the diene hydrocarbons alone appears t'o justify further investigation.
90
ACKNOWLEDGRIENT
I): W
g 75
;
g70 I):
z
N-BUTYLESTER
6 1
,
*;
, , ,,//: ------ --..+----h I
,
6
% METHACRYLIC ACID ESTER IN INITIAL MONOMER
Figure 17. Effect of Methacrylic Acid Erterr Mixed with Butadiene and IsoDrene on Resilience of Vulcanized kopolymers (Cured 30 Minutes at 153" C.)
30
50
40
60
70
80
% METHACRYLIC ACID ESTER IN INITIAL
MONOMER
The authors wish to express their appreciation t o F. W. Johnson, \T. F. Anzilotti, A. F. Benning, L. A. Hamilton, J. E. blallonee, S. F. Toussaint, V. TT'einmayr, and A. V. Willett of this laboratory for the preparation of many of the compounds used in this investigation.
Figure 18. Effect of Methacrylic Acid Esters Mixed with Butadiene on Hardness of Vulcanized Copolymers (Cured 30 Minutes at 153" C.)
variations. The replacement of part of the styrene in the GR-9 formula with dimethylvinylethynylcarbinol was investigated in 8ome detail, and mixtures of 75 butadiene-20 styrene-5 dimethylvinylethynylcarbinol gave (18) elastomers superior to GR-S in millability, tensile properties, and low heat build-up under flexing, but not superior to those made from butadiene with 20 or 30 parts of the carbinol and no styrene. CONCLUSION
In any study of polymerization, careful consideration must be given to factors such as type and concentration of emulsifying agent, concentration of monomer, temperature, catalyst, and certain added chemicals which may have a marked effect upon the results obtained. It is possible to make elastomers of considerable utility from
LITERATURE CITED
(1) Bachle, Otto (to I. G. Farbenindustrie), German Patent 702,209 (Feb. 1, 1941).
(2) Bock, Walter, and Tschunkur, Eduard (to I. G. Farbenindus-
trie), Brit. Patent 349,499 (May 26, 1931) : German Patent 532,271 (Aug. 22, 1931); U. S. Patent 1,898,522 (Feb. 21, 1933). (3) Browning, G. L., Jr. (to B. F. Goodrich Co.), U. S. Patent 2,385,190 (Sept. 18, 1945). (4) Bysow, B. W. (to Resinotrest), Brit. Patent 314,933 (July 6, 1929); German Patent 521,903 (Mar. 31, 1936). (5) Dogadkin, B. A., Beresan, K. B., and Lapuk, M. G., Russian Patent 46,354 (Mar. 31, 1936). (6) Fryling, C. F. (to B. F. Goodrich Co.), U. 8.Patent 2,313,233 (Mar. 9, 1943). (7) Ibid., 2,376,350 (May 22, 1945).
INDUSTRIAL AND ENGINEERING CHEMISTRY
222
Vel. 39, No. 2
(14) Luther, Martin, and Heuck, Ciaus (to I. G. Farbenindustrie) , Brit. Patent 318,296 (Sept. 2, 1929); (to I. G. Farbenindustrie to Jasco Methyl Stress Tensile Inc.), U. S. Patent 1,896,491 (Feb. 7, 1933). Vinyl a t 300%, Strength, Kerosene Ketone, Yield, Lb./ Lb./ Elonga- Absorp- !??ez2Resistance, c. (15) Meisenburg, Kurt (to I. G . Farbenindustrie). % % Sq. In. Sa. In. tion, tionQ, 70 T-10 T-50 Brit. Patent 349.976 (June 5 . 1931): Germax 20 93 .. 1210 120 94 - 63 - 54 Patent 543.343 (Feb. 4. 1932): , , C . S.Patmt 30 80 1020 2720 520 76 50 -1,901,354 (Mar. 14, 1933). 40 91 1640 3080 420 35 - 42 -- 40 37 (10) Meisenburg; Kurt, and Bock, Walter (to I. G. 50 91 2890 3050 310 23 --2836 - 30 60 82 1780 3450 470 14 - 20 Fnrbenindustrie) Brit. Patent 358,877 (Sept. 80 32 1210 2890 520 5 - 20 - 10 29, 1931): German Patent 573,568 (-4pr. 3, 1933) : U. S. Patent 1,938,751 (Dcc. 12, 1933). a 48 hours a t 100’C. (17) Meisenburg. Kurt. Dennstedt. Inrofroh, and Zauiker; Ewald (to I. G. Farbenindustrie to TABLEVIII. PROPERTIES OF R~~,~DTDNE--DI?IIETHYLT.ISI~LJascoInc.),U. S.Patent2,248,107 (Julys, 1941) ETHYNYLCARBINOL ELASTOMERS (18) RIighton, C. J. (to Du Pont Co.), Brit. Patent 568,964 (-%pi.27, 1915). C O M P O U N D IFNOGR M U L(AC K R E D30 MI.?-.A T 141‘ C . ) Elastomers 100 (19) Murke, Hans (to I. G. Farbenindustrie), Frenrh Patent 850,210 Phenyl-&naphthylamine 2 (Dee. 11, 1939); Brit. Patent 525,733 (Sept. 3 1940); (tc” Zinc oxide 5 I G. Farbeninciustrie to Jasco Jnc.), U S. Patent 2,260,475 MPC black 50 (Oct. 28, 1941). Stearic acid 2 Sulfur 1.5 (20) O h , J. F. (to SharpIei Chemicals Inc.), U. S.Patent 2,378,030 Helioeone 1.5 (June 12. 1945). Process oil 3 (21) Parker, J. L. (to Du Pont Co.), Ibid., 2,382,812 (Aug. 14, 1045) Benaothiazyl-2-monocyclohexylsulfonamide 1.3 Brit. Patent 578,214 (June 19, 1946). Dimethylvinylethynylcarbinol, parts 10 15 20 30 50 (22) Sandhaas, Wilhelm, Daniel, Walter, and Muhlhauzen, KoineTested a t 25’ C. 1050 1525 1100 1390 lius (to I. G . Farbenindustrie), U. S.Patent 2,200,705 (Mav Stress a t 300%, Ib./sq. in. 900 2275 2875 3000 4400 3220 Tensile strength, lb./sq. in. 14. 1940). 465 580 480 655 480 Elomation a t break. % (23) Sebrell, L. B. (to JYingfoot Corp.), l b i d . , 2,235,379 (Sept. 17 175 145 165 290 . . * Tear-resistance. Ih. 1940): Brit. Patent 533.142 (Feb. 6. 1941). 59 Shore durometer hardness 59 58 . . . 57 Heat build-up in 20 min. on Goodrich (24) Starkweather, H. W., and Coilins. 8.M. ’(to Du Pont Co ) ” 44 44 . . ” 52 flexometer (l/a-in. stroke) 53 U. S.Patent 2,218.362 Q c t . 15, 1940). 54 . . . Resiliency (Yerzley) 56 53 49 (25) Starkweather, H. TI’, and Youker, 11~A, Ibid., 2,234,204 Tested a t 70” C. (Mar. 11, 1941). 1025 1400 1850 2450 Tensile Btrength, Ib./sq. in. 140 180 135 285 Tear resistance, lb. (26) Talalav, Anselm. and RI mat. Michel. “Synthetic Rubber iron, vol. inorease i n Kerosene absorption, Alcohol”, New York, Interscience Publishers, Inc., 1945. 130 103 . . I 180 155 48 hr, a t 100°oC. (27) Tochtermann, Hans, and Heuck, Claus (6I. G. FarbenindusFreeze resistance, C. T-10 - .. - 62 - 57 - 46 -29 - 16 trie), Brit. Patent 329,969 (May 27, 1930); U. S. Patent T-50 - 43 - 42 -36 - 22 -7 1,814,420 (July 14. 1931); German Patent, 577,731 (June 3, -1 -32 -31 - 28 - 14 T-80 1933). (28) Tschunltur, Eduard, and Bock, Walter (to I. G. Farbenindustrie), Brit. Patent 339,255 (Dec. 1, 1930); German Patent 570,980 (Feb. 27, 1933); (t,o I. G. Farbenindustrie t,o Jasco (8) Gibbons, W.A , , Gerke, R. H., and Tingey, H. C., ISD.E s o . h e . ) , U. S.Patent 1,938,731 (Dec. 12, 1933). CHEM.,ANAL.ED.,5 279 (1933). (29) Williams. Ira. IKD.FSG.CHEM..16. 362 (1924). (9) Gunther, Fritz, Hopff, Heinrich, and Schuster, Curt (to I. G. (30) Williams, Ira, and Sturgis. B. M , Ibid., 31, 1303 (1939). Farbenindustrie). Brit. Patent 294.412 (Julv 26. 1928) : (31) Wolfe, W. D. (to Wingfoot Corp.), U. S. Patent 2,217,031 German Patent 519,483 (Feb. 28, 1931); U.. S.patent 1,838,(Oct. 8, 1940). 826 (Dee. 29, 1931). (32) Wollthan, Heinz. and Becker. ‘CVilhelm(to I. G. rarbenindustriei (10) I. G. Farbenindustrie, Brit. Patent 360,822 (Oct. 30, 1931): French Patent 843,903 (July 12, 1939); Brit. Patent 519,730 German Patent 667.163 (Nov. 5* 1938). (April 4, 1940): (to I. G . Farbenindustrie, to Jasco Inc.), (11) I. G . Farbenindustrie, German Patent 704,039 (Feb. 20, 1941) U. S.Patent 2,281,613 (May 5, 1942). (12) Konrad, Erich, and Tschunkur, Eduard (to I. G. Farbenindus(33) Youker, M.A. (to Du Pont Co.), U. S . Patent 2,333.403 (?;ow trie) Brit. Patent 300,821 (Oct. 30, 1931); (to I. G. rarbeii2, 1943). industrie t o Jasco Inc.), U. S. Patent 1,973,000 (Sept. 11. 1934). (13) Luther, Martin, and Heuck, Claus (to I. G. Farbenindustrie), P R E S Z N T Ebefoie D t h e Division of Rubber Chemistry a t t h e 109th Meetinp Biit. Patent 312,201 (May 21, 1939); U. S.Patent 1,864,078 of the - ~ W E R I C A XCHEMICAL SOCIETY, Atlantic City, N. J. Contribution 4f (June 21, 1932); German Patent 558,890 (Sept. 19, 1932). fiom Jackson Laboratory, Du Pont Company.
TABLE VII. PROPERTIES OF BUTADIESE-METHYL VINYLKETONE ELASTOMERS O
~~
~
is
d
EFFECT ON THE NOKiWAE AGLV J . P. HOLLIHAN AND SANFORD A. Mc1BSS, JR. American Viscose Corporation, Marcus Hook, Pa.
URING the aging of viscose, the cellulose xanthate becomes steadily more precipitable; this behavior is probably due largely to the gradual loss of the solubilising xanthate groups (2, 9). Some authors, however, contend that the effcct is primarily physical or colloidal (6, 9). Whatever the mechanism, the effect is of great practical importance inasmuch as viscose solutions are always aged to a definite degree of precipitability before being spun. This optimum spinning age is gcnerally determined by standard tests involving a Ealting out of the cellulose
xanthate, the results being expressed as salt index, Hottcnroth number, etc. A number of substances are ltnomn n hich, when added t o viscose, substantially affect the rate of aging (9). The effect of these compounds, however, is entirely a retardation of thc normal rate of aging, and no immediate increase or change in the salt index is observed when they are added. I n contrast, acrylonitrile and certain related compounds (4) have a marked solubilizing action and cause a n immediate rise in salt test, as indicated by the data of Tables I and 11.
