-
development
Master Batches from Carbon Blacks with G -S latices JAMES W. ADAMS, W. EARL MESSER,
AND
LOUIS H. HOWLAND
UNITED STATES RUBBER CO., NAUGATUCK, CONN.
Recent advances in the manufacture of GR-S types of synthetic rubber and carbon blacks prompted a thorough investigation of processes for producing master batches from improved butadiene-styrene copolymers and fine furnace blacks. Investigations that were conducted to develop satisfactory processes for mixing and coprecipitating “cold” GR-S latices and high abrasion furnace carbon black slurries also revealed useful information about the production of other types of latex master batches. Carbon black slurry preparations, carbon black properties, the stability of carbon black-latex systems, carbon black dispersions in
master batch compounds, processing of carbon blaclilatex mixtures, and flocculation variables were studied. Supplying manufacturers of rubber goods with elastomers containing carbon blacks has made i t possible for them to realize improvements in product quality, maintain cleaner fabricating plants, reduce milling time and power consumption during mixing, and simplify materials handling. S e w developments in methods of producing latex master batches made it possible to obtain greater quality improvements and reduce the cost of manufacturing GR-S latex-incorporated carbon black master batches.
T
in the Borger plant and one in Baytown, Tex., has steadily increased, as illustrated in Figure 1. The research and development work preceding plant scale operations was necessarily involved because of the nature of elastomer latices and carbon black slurries. Both systems are aqueous dispersions of very small particles with diameters of 10 to 300 millimicrons, which from physical, chemical, and production standpoints present many problems. A single, polydispersed system such as latex itself is inherently complex, and it is difficult to analyze mixtures of two such systems of dissimilar materials. For this reason only a few of the possible variables in the process, those that were considered to have the greatest influence on the quality of master batches, were investigated.
H E R E are two general methods for compounding carbon blacks with synthetic rubbers. The first consists of mixing the two materials in a dry state in powerful masticating equipment, and the second consists of coprecipitating mixtures of carbon black and liquid latex to produce pigmented compounds. The latter method, known as latex masterbatching, has received considerable attention since 1943, primarily because of certain desirable features of supplying manufacturers of rubber goods with rubbers already containing carbon black. Recent work along the lines of improving the quality of latex-incorporated carbon black master batches has been centered around developing methods for producing compounds from the new low temperature types of GR-S latices and fine furnace carbon blacks. Aside from this phase of the investigation, much of the work reported deals with overcoming difficulties encountered in producing latex master batch compounds containing good carbon black dispersions. GR-S latex-incorporated carbon black master batches, or “black” types of GR-S as they are often called, are made commercially by coprecipitating mixtures of latices and carbon black slurries to produce pigmented compounds. Because the details of the process have been described (4,6, 7, IO),this paper presents certain advances in production of latex master batches with particular reference to tire tread compounds of high abrasion furnace (HAF) carbon blacks in GR-S polymerized a t low temperatures. Most types of elastomer latices can be mixed with aqueous carbon black dispersions and the resulting mixtures coprecipitated to produce master batches. Prior to 1948, however, this particular process in the synthetic rubber industry was centered around producing latex master batch compounds from easy processing channel (EPC) carbon blacks and copolymers of butadiene and styrene that were copolymerized in emulsions a t temperatures around 50” C. Early in 1948 new types of “cold” GR-S and fine furnace carbon blacks became available for the first time in substantial quantities for compounding. At that time plant production of low temperature GR-S latex (5” C. polymerization) incorporated HAF black master batches began a t Borger, Tex., in one of the Government’s synthetic rubber plants. The quantity of these master batches produced
DISPERSING CARBON B L 4 C K S IN W4TER
A study of the fundamental and practical aspects of preparing concentrated carbon black slurries for producing latex master batches established that surface active agents were required to stabilize and reduce the viscosity of slurries, render them compatible with latices, and prevent excessive corrosion of equipment. The most effective surface active materials for these applications were products classified as dispersing agents that stabilized and reduced the viscosity of concentrated aqueous suspensions. Because the action of dispersing agents on suspended particles was found to be specific for the type of material being dispersed, it was necessary to use various carbon blacks for testing purposes rather than interpret results obtained on different pigments. Other factors which governed the selection of test methods were the observations that dry carbon blacks even in the “fluffy” or uncompressed state did not produce well dispersed systems when added to dilute dispersing agent solutions under conditions of standard agitation, and the amount of dispersing agent required to produce fluid slurries varied xith the size of the dispersed particles. Daniel ( 2 ) cites several conventional methods for determining the relative merits of dispersing agents, none of which m r e found to be applicable to testing a large number of surface active agents 754
INDUSTRIAL AND ENGINEERING CHEMISTRY
March 1951
in a variety of solutions that comprise dispersing media for carbon blacks. Other methods (3, 6, 9, 11) evaluated were found to be satisfactory for specific applications but inadequate €or general use in testing dispersing agents under different conditions that affected their dispersing efficiencies.
755
APPLICATIONS OF TEST
During the course of evaluating a large number of surface active agents it was found that alkalies, particularly sodium hydroxide, increased the dispersing efficiencies of some materials more than others, The relative viscosity-reducing powers a t various sodium hydroxide concentrations of two commercially available dispersing agents (Figures 3 and 4) were determined and graphed to illustrate this effect. The following materials were used in the experiments:
1. TRITON R-100. An anionic dispersing agent comprised of condensed sodium salts of alkylnaphthalene sulfonates supplied by the Rohm & Haas Co., Philadelphia, Pa. 2. HORNKEM No. 12. A glucoside type of anionic dispersing agent supplied by the Warwick Chemical Co., Long Island City, N. Y. 3. PHILBLACK 0. A high abrasion furnace (HAF) type of rubber compounding carbon black supplied by the Phillips Petroleum Co., Philblack Division, Akron, Ohio. 4. KOSMOBILE 77. An easy processing channel (EPC) type of rubber compounding carbon black supplied by the United Carbon Co., Charleston, W. Va. 5. STATEX93. A high modulus furnace (HMF) type of rubber compounding carbon black supplied by the Columbian Carbon Co., Xew York, N. Y.
-
ALL MASTERBATCH TYPES LOW TEMP. OR-S HAF BLACK TYPES
-
Figure 1. Production of Master Batches in All GR-S Plants
Experience gained from evaluating various methods indicated that procedures for obtaining uniformly well dispersed systems were a prime requisite for determining the relative merits of various products, Ball milling, “colloid” milling, and hand mulling techniques were rejected in favor of haud homogenizers (Fisher Scientific Co., Pittsburgh, Pa., Catalog No. 7-042) and various high speed mixers such as a Waring Blendor (Waring Product Corp., New York, N. Y . )for laboratory scale operations. Mixers of the latter type that operated a t speeds between 5000 and 20,000 r.p.m. were used to determine the dispersing agent requirements of 20% carbon black slurries.
Because channel types of carbon black are acidic, whereas furnace types are alkaline, the expected greater benefits were observed when the alkalinity of slurries containing EPC black was increased. On the other hand, unexpected results were obtained when the complementary effects of alkali on the viscosity-reducing powers of certain natural glucoside and wood lignin products were determined. Hornkem No. 12 served as a specific example where the addition of 0.7% sodium hydroxide
T E S T PROCEDURE
Forty grams of carbon black were weighed out into the mixing bowl of a Waring Blendor. The desired amount of 1 N sodium hydroxide diluted to 150 ml. with distilled water was added, and the slurry was mixed for 30 seconds to moisten the carbon black. The dispersing agent solution (0.1gram per ml.) was added from a buret in less than 1-ml. increments, with subsequent mixing after adding each portion, until a fluid dispersion was obtained. When the condition of fluidity had been reached, the slurry was mixed for an additional minute to check the end point. If thickening occurred within 5 minutes more dispersing agent was added.
% sodium hydroxide on carbon black L
d
yo dispersing agent for fluid slurry
=
= 0.18
M(190
v -
~
16
18 20 22 PSRCENT CARBON BLACK IN SLURRY
24
Figure 2. Dispersing Agent Requirements of Slurries
+M )
800
where S = milliliters of 1 N sodium hydroxide added and M = milliliters of dispersing agent solution added. The original carbon black-alkali-water pastes contained 21% carbon black by weight, which allowed for adding 10 ml. of dispersing agent solutions to produce 2001, slurries. Because the amounts of dispersing agent solutions varied, the concentrations of carbon black in the final, fluid suspensions were also variable. Calculations for reporting the results in terms of per cent dispersing agent on the carbon black required to produce fluid 20% slurries compensated for dispersing agent solution volumes above or below 10 ml. This correction was justified by the fact that a linear relationship was found to exist between the dispersing agent (Marasperse CB) requirements of slurries and their carbon black contents within the range of 15 t o 25% carbon black (Figure 2).
to EPC black slurries reduced the amount of material required to prepare a fluid 20% slurry from 4.3% on the carbon black, when no additional alkali was used, to 1.0%. Twelve different dispersing agents were evaluated in this manner and it was found that dispersing powers could best be compared in HAF black slurries. Materials that were used in concentrations of less than 6% on a particular lot of HAF black used in testing to produce fluid 20y0 slurries were considered as possible dispersing agents for GR-S latex-carbon black incorporation processes. The surface active agents listed and described in Table I were those found to be most effective. PARTICLE SIZE OF SLURRIED CARBON BLACKS
In addition to their ability to lower the viscosity of slurries, dispersing agents also act as grinding aids by preventing the reagglomeration of suspended particles that have been disin-
INDUSTRIAL AND ENGINEERING CHEMISTRY
756
tegrated by mechanical methods. This property was considered to be important for some applications and test methods for evaluating dispersing agents in this respect have been reported (9, 11). Various methods were considered; the one best suited to investigating the particle size of slurried carbon blacks entailed the determination of light-absorbing properties of dilute slurry suspensions.
Vol. 43, No. 3
then (12,0000) - ___
d = 137 d
=
K = m = b = D =
C S W P
=
= = =
(SWP) average particle diameter extinction coefficient slopeof line constant optical density of suspension concentration of carbon black, grams per liter aliquot of diluted suspension taken for final dilution weight of sample, grams per cent carbon black in slurry
The measurements relied on processes for obtaining good dispersions of the black in water and in no case could it be assumed that conditions of ultimate dispersion were obtained. For this reason, the method chosen for calculating results was not in accord with reported findings on absolute carbon black particle size-light absorption relations. Because the measurements included an ease of dispersion factor, the term [‘particle size index” was used to report results. APPLICATIONS QF TEST I 0
2 PERCENT
Figure 3.
NoOH
4 6 ON CARBON B L A C K
I
The test method was employed for evaluating equipment used mechanically dispersing carbon blacks for preparing slurries. In a typical example a \Taring Blendor was used to prepare 20% slurries of Philblack 0 (HAF) and Kosmobile 77 (EPC) blacks containing variable amounts of Marasperse CB and sodium
.e
111
Triton R-100 in 20% Carbon Black Slurries
A proximately 2.5 grams of carbon black slurry were accurate& B-eighed out into an aluminum foil dish. The dish plus contents was added to 1liter of water contained in a 2-liter beaker and the suspension was mixed thoroughly. Two- and 4-ml. aliquots of the diluted slurry were pipetted into 100-ml. volumetric flasks and diluted to 100 ml. with water. The optical densities of the suspensions were determined a t a Kave length of 400 mp in a Coleman Model 11 spectrophotometer. A PC-4 (blue) filter and square cuvettes giving a solution thickness of 13.2 mm. vere used. Particle size index = 137
- (12,0000) -__
T.4BLE
I. DISPERSIXG -4GENTS
7%
DisiJersing Agent Marasperse CB
(SWP)
Western hemlock bark extract Indulin A Triton R-100
The test method was calibrated by determining the estinction coefficient, K , of well dispersed very h e furnace (VFF) and semireinforcing furnace (SRF) carbon blacks that were reported to have average particle diameters of 30 and 80 mp, respectively. The equation of a straight line connecting the t v o points on a graph of extinction coefficients versus average particle diameters provided the calculation used in the procedure. Av. Particle Diameter, mil 30 80
Extinction Coefficient, R 89 47.5
d = K m f b
+b 80 = 47.5m + b
30 = 89m
-50 = 41.3m m b b d
when
K
D -
c
10,0000 STVP
(’
1
‘2)
(1) - ( 2 )
= -1.20 = (89 X 1.20) = 137 = 137 - 1.20K
+ 30
Source XIwathon Corp., Rothschild,
Preparation Method -4
Dispel sing Agent for Fluid 2 0 7 EIAF Blact Blurry 2 3
WlS.
Silvacon 490 extract (78% of hark) Hornkem 12
where 0 = optical density at 400 mp X = aliquot of diluted suspension taken for final dilution W = weight of sample, grams P = per cent carbon black in original slurry
Carbon Black VFF SRF
FOR CARBON BLACK
Hornkem 3G Chestnut extract Tomlinite Silvacon $90 suspension Vnltramine R Triton R-150 hIasonite oil well treating agent Ammonia-base sulfite liquor ~ o p c oGUF Daxad 11 Hornkem 1 Redwood bark dust extract ( 5 0 7 ~of bark) Bark 49-126 extract (43% of bark) Lomar PTV Indulin C
Co.,
C
Warwick Chemical Go., Long Island City N. Y. Crown Zellerdaoh Corp., Camas, Wash.
A
2 ,9
C
3.4
D
3 3
Weyerhaeuser Timber Longview, Wash.
W. Va. Pulp & Paper Co., Charleston, S. C. Rohm & Haas Co., Philadelphia, Pa. Warwick Chemical Co. Xead Corp Lynchbiiio. \’a. Howard S k t h Paver Co., Cornaall Ont. Canada TeyerhaeuAer Tiinber Co.
2.7
. I
3.8
.k E D
3 8 3.8 3.8
B
3.8
General Dyestuff Corp., Philadelphia Pa. Rohm Bi Haas Co. Xasonite Corp., New Y o r k , N. Y .
A
4.0
Crown Zellerbach Corp.
E
4.7
;?;opco -Chemical Co., I-Iarrison, N. J . Dewey & Almy Chemical Co., Cambridge. Mass. Warwick Chemical Co. Pacific Lumber Co., San Fraucisco, Calif.
A
4 8
A
4.9
A
c
5.0 5.2
W. Va. Pulp & Paper Co.
C
5.2
Jac ues Wolf Bi Co., Brighton, dass. W. Va. Pulp & Paper Co.
A
5.5
A
5.7
A
E
4.4
4.4
-4. 10 grams of dry material dissolved in water and solution diluted to 100 mi. B 10 grams of pulverized bark reacted with 2 grams of NaOH in 80 ml. of witer for 20 minutes a t 90° C. Cooled suspension diluted to 100 ml. C, Suspensions prepared by method B centrifuged for 15 minutes a t 1500 r.p.in. Clarified portion analyzed for per cent solids and evaluated. D. 10 grams of dry material reacted with 1.2 grams of NaOH in water. Solution diluted t o 100 ml. E. 10 grams of dry material dissolved in 90 ml. of water. pH of solution adjusted t o 9.0 before diluting to 100 nil.
INDUSTRIAL AND ENGINEERING CHEMISTRY
March 1951
*
t
757
These facts seemed to contradict previous findings that less dispersing agent was required to produce fluid concentrated slurries of larger black particles, but the ones concerned in those cases were particles compacted in the dry state which presented relatively small surface areas to the action of dispersing agents. When the slurry was disintegrated and the conditions in the slurry were such that the particles coalesced, the resulting loosely packed agglomerates formed a netwoqklike system that had a large surface area. From this i t was apparent that a certain number of loose agglomerates of carbon black could be present in slurries without appreciably increasing their viscosities. CARBON BLACK PROPERTIES
. .
PERCENT N a O H ON CARBON BLACK
Figure 4. Hornkern No. 12 i n 20940 Carbon Black Slurries
Rubber compounding carbon blacks exhibit different properties when dispersed in water for incorporation with elastomer latices. The acidic DroDerties exhibited bv of channel carbons “ disDersions . have been attributed to the chemical composition of the black surfaces. The various carbon-oxygen complexes produced during carbon formation in an oxidizing atmosphere react to combine with anions when the material is suspended in water. These reactions, which disrupt the pH equilibrium by removing hydroxyl ions, lower the pH of the aqueous phase. Furnace blacks, on the other hand, behaved differently, in that water suspensions of these materials exhibited alkaline properties. The mechanics of the reactions involved have not been definitely established. Most investigators believe that inorganic salts derived from the water used for cooling the black impart the high p H values.
*
hydroxide in the dispersing media. Samples of the slurries were removed a t several time intervals during mixing and the particle size index of the slurried carbon black in each sample was determined. Data collected in this manner (Figures 5 and 6) indicated that well dispersed slurries could be prepared by treating proper mixtures of carbon black, dispersing agent, and sodium hydroxide for a t least 90 seconds in a Waring Blendor. It was also observed that both the dispersing agent and sodium hydroxide concentrations affected the particle size of the dispersed black. Additional work along these lines revealed that 0.4% sodium hydroxide on both carbon blacks plus 3.5 and 2.0% Marasperse CB on slurried Philblack 0 and Kosmobile 77, respectively, produced the best dispersions. The amounts of dispersing agent necessary to produce fluid slurries of these carbon blacks were considerably less than the amounts required to obtain minimum particle sizes of the dispersed blacks. As i t is known that the Waring Blendor is capable of disintegrating carbon black agglomerate;, this difference was explained by the fact that fluid slurries prepared in this or similar mixers initially contained well dispersed carbon black which reagglomerated when insufficient dispersing agent was present in the system to keep the suspended particles separated by electrical repulsion forces. Definite evidence of this reagglomeration phenomenon was witnessed when concentrated slurries containing small amounts of dispersing agents were masticated and upon standing became [‘livered” or gel-like. Subsequent mixing of the thixotropic mixtures returned them to a fluid state.
The degree of acidity or basicity of rubber compounding carbon blacks was determined by dispersing 40 grams of the black in 360 ml. of water (pH 7.0) that contained 0.8 gram of Triton R-100. The slurry was transferred to a 600-ml. beaker and its H determined. If the initial p H was below 7.0, 0.1 N sodium fydroxide was added until a H of 9.0 was reached. If the initial p H was above 7.0,O.l N sufiuuric acid was added to adjust it to 4.0. Neutralization equivalent = IOORAT where
$ $
~
~
g:f~$:z
Neutralization equivalent =
~
~
- lOOAN
where A = milliliters of standard sulfuric acid N = normality of standard sulfuric acid The term “neutralization equivalent” expressed in units of milligrams of sodium hydroxide per 100 grams of carbon black was chosen as a means of reporting all results. Negative values denoted titrations with sulfuric acid. Various samples of
P
MlXlNQ
Figure 5.
T I M E , SECONDS
HAF Black Dispersed with Waring Blendor
M I X I N O TIYE,SECONOS
Figure 6.
EPC Black Dispersed with Waring Blendor
~
758
Vol. 43, No. 3
INDUSTRIAL AND ENGINEERING CHEMISTRY
the aame GR-S type and carbon blacks showed normal c u r i n g p r o p e r t i e s . The cure-retarding action imparted by reducing the black alkalinity and incorporating organic acids derived from dispersing agents used for slurrying the carbon blacks was responsible for the improvement. A n a l y t i c a l procedures used for evaluating dispersing agents were combined and modified to determine the dispersing agent requirements and particle size indexes o f carbon blacks in water. Increments of a 0.1 gram per ml. solution of Marasperse CB were added under conditions of violent agitation to a slurry of 100 grams of carbon black in 10 ml. of 1 iV sodium hydroside diluted to 350 ml. with water. The volume of dispersing agent sohtion required to produce a fluid slurry was converted to per cent dry material on the carbon black in a 20oj, slurry. Maras erse CB solution was Figure 7. Carbon Black Dispersions Produced by Black-Latex Creaming added to the &id slurry until a total of 50 ml. had been added. Five grams Left to rialir. B-349, B-348, B-3.50, B-339 of the slurry were weighed out and diluted to 2 liters with water, and duplicate Zml. aliquots were pipetted into 100-ml. volumetric flasks. The portions were diluted to 100 ml. different types of black were analyzed by this test method and and the optical densities of the suspensions were determined at a the range of values obtained for each type (Table 11) indicated wavc length of 400 mp. significant differences. The differences in neutralization equivalents of the E P C carbon blacks provided an explanation for one yo rCIaraspcrse CB for fluid 20% slurry = (450 M ) operat,ional problem frequently encountered when slurries of (500) channel blacks are prepared for latex incorporation. It was GOOD Particle size index = 137 - __ necessary to adjust the pH of t.hese durries to 9.0 to 10.0 to make the most efficient use of dispersing agents and render the where slurries latex-compatible. Inasmuch its approximately 14,000 A? = nlillilit,ers of Marasperse CB solution added pounds of carbon black w r e slurried for one plant batch and D = optical density of the diluted suspension neut,ralization equivalen ts of various EPC black shipments would W = weight of slurry sample, grams vary as much as 300 units, this represented a sodium hydroxide requirement varia.tion of 42 pounds per batch. Tho range of values shown in Table I1 indicatcd that r a c h Carbon blacks that exhibited acidic proprrties generally carbon black classification included materials with relativcly retarded curing when vulcaniaatcs wcre prrpared from dry wide variations in dispersing agent requirements and particle mixed elastomer-black compounds; conversely, blacks that ~ v c r c size indexes. Because the conventional dispersing agent concenbasic either accelerated or had no effect on the rate of curc. trations of 1 . 5 to 2.25% used in preparing EPC, HMF, and SRF I n latex master batch comuounds the situation was somewhat different, because all carbon blacks incorporated in TARLE 11. CARBOSBLACK PROPERTIES this manner were subjected to condiNeutralization Dispersing Agent tions of low pH (2.5 to 3.5) when the Equivalent, Requirement, Particle 11g. NaOH/100 G. Siae b l a c k - l a t e x mixtiires were coprecipiCarbon Black Type Black 6BMarasperse on Blark Index tated. This was suggested as one of Philblack O",lot 1 11SF - 1.55 2.4 46 Philblaok 0, lot 2 ETAF - 157 41 2.0 the reason8 why compounds from la3.6 182 47 Improved Kosmos 60 ', lot 1 HAF tex-incorporated black master batches Improved Rosmoa GO, lot 2 TlAF - 230 4.7 48 usually cured more slowly than similar 49 Vulcan 3'. lot 1 IIAF -11.5 2.9 IIAF 120 2 . 6 35 Vulcan 3, lot 2 dry mixed stocks. It was also indiI-IAF - 168 2.8 38 Aromexd H.4F '-96 2.9 43 Statex R d cated that the largest, differences be- 490 2.5 62 Kosmos 62' RF tween the cure rates of compounds - 175 2.7 RF Statex I< from latex master batches and mill- 580 2.0 RF Witco FF/ - 580 2.7 RF 50 Witco EFF mixed stocks were found when master 77 HMF - 95 1.4 Sterling SOc batches were made of blacks with very HMF 1.3 76 - 100 Philblaok A n 0.7 91 HMF - 200 ICosmos 40 b low neutralization equivalents (very 0.8 53 EPC Kosmobile 77 180 h i g h a l k a l i n i t y ) . Mill-mixed com0.7 52 240 EPC Wyexd pounds of GR-S and the alkaline, fine ... EPC 118 Spheron 9 furnace blacks exhibited uncontrollable curing properties (scorch) when special precautions were not taken to modify the formulations, whereas compounds from latex master batches containing
+
w
March 1951
INDUSTRIAL A N D ENGINEERING CHEMISTRY
black slurries for latex incorporation were above the highest minimum requirements, little trouble was encountered with nonfluid slurries. On the other hand, HAF blacks were difficult to slurry because of their high and variable dispersing agent requirements. For these reasons slurries containing less than 20% carbon black were prepared or a special make-up procedure described below was used. Dispersing agent requirement values were compared with carbon black properties reported by the black manufacturers and it was indicated that an increase in particle size and a depease in structure (reticulate chains), surface area (porosity), or ash content lowered dispersing agent requirements.
459
Phillips Petroleum CO. for a program set up to determihe the relative merits of these products and pulverized black pellets. Results obtained from evaluating vulcanizates from various types of latex-incorporated master batches containing the special carbon blacks revealed them t o be equivalent and in some instances superior t o vulcanizates from similar master batches made from pulverized pellets. Stocks from the f i s t master batches prepared from loose, unpelleted EPC blacks exhibited exceptionally good wearing properties, but those that were prepared and tested subsequently did not confirm the. original findings. The work did indicate that free carbon blacks could be used satisfactorily for preparing latex master batches, provided it is economically feasible.
CARBON BLACK SLURRY PREPARATlON STABILITY OF CARBON BLACK-LATEX
u
i
When studying the slurrying characteristics of the carbon blacks it was found that the order in which the ingredients were added in preparing slurries was important in obtaining maximum viscosity-reducing benefits from the dispersing agents. For the system, carbon black-water-dispersing; agent-alkali, it was found that the smallest amount of any one dispersing agent was required when the carbon black was mixed with a solution of alkali in water and the dispersing agent solution was added in increments while the mixture was agitated. From this it was apparent that when surface active agents were used in minimum quantities to stabilize, deflocculate, and reduce the viscosity of dispersions, a “competitive” reaction occurred in which particle surfaces competed for adsorbable materials. For purposes of illustration it was assumed that a carbon black particle could adsorb enough dispersing agent to cover three fourths of its surface area, yet coverage of only one fourth of the surface was necessary to cause it to repel a particle similarly coated. Some slurry preparation methods entailed adding pulverized carbon blacks to solutions of dispersing agent plus alkali in sufficient water to make slurries of the desired concentration. When a similar procedure was used, the carbon black first entering the dispersing medium adsorbed enough material to satisfy ita maximum requirements. As black addition progressed, less dispersing agent was available in solution for adsorption, and when small amounts of dispersing agents were used insufficient material was available t o disperse the last portion of black added. In one typical experiment it was found that 2.5% Marasperse CB was required to prepare a fluid 20% slurry of an HAF black when the Marasperse was added in increments to the wet black. When portions of the same carbon black were pulverized and added to solutions containing various amounts of Marasperse CB, 3.070 was required. At the outset of the program it was felt that the poor quality of certain latex-incorporated carbon black master batches could be attributed to the use of slurries that contained poorly dispersed carbon blacks. Extensive testing of mlcanizates from master batches prepared from slurries of varying quality indicated this assumption t o be false. Apparently, the fragments of incompletely disintegrated carbon black pellets that were present a t times in plant slurries could be dispersed in master batches by normal GR-S compounding procedures. It was observed, however, that the quality of carbon black dispersions had to be reasonably good to obtain satisfactory black retention during flocculating and washing operations. Carbon blacks received a t the copolymer plants in the form of pellets are micropulverized for preparing slurries. Because a certain amount of expense is involved in pelletizing operations a t the carbon black plants and pulverizing operations a t the copolymer plants to produce carbon blacks suitable for slurrying, it seemed logical from a cost reduction standpoint to evaluate various unpelletized forms of carbon blacks that could be introduced into the master batching process directly. Special lots of dry and slurried ‘(free” blacks (loose, unpelleted, and not micropulverized) were supplied by the J. M. Huber Corp. and
SYSTEMS
When two polydispersed systems such as carbon black slurries and GR-S latices were mixed, it was proposed that surface active agent equilibria that existed in the systems before mixing would be disrupted to cause agglomeration of black and/or GR-S particles. The extent of agglomeration would be determined largely by the type, concentration, and distribution. of the surface active agents together with the amount of electrolytes present in the mixed dispersions. The expected flocculation was observed when channel blacks that were normally acidic were incorporated without dispersing agents in GR-S latex. Conversely, it was found that alkaline (furnace) types of carbon black or slurries made alkaline with sodium hydroxide were compatible t o a certain degree with the same latex. Because blacks in these forms existed as agglomerates that were tremendous in size when compared with GR-S latex particles, the relatively small carbon black surface areas were rapidly covered with GR-S. A gray, grainy appearing dispersion was produced. When slurries containing small amounts (0.5% Triton R100) were mixed with latex they were
N 0 . 3 RUBBER
STOPPER
20mm. GLASS TUBlNO
V 8 ‘ COVER QLASS
OROSS SAMPLE
Figure 8. Apparatus for Preparing Thin Films of GR-S Compounds
initially compatible but on standing they became gray in appearance, which indicated an excess of copolymer particles. As the concentrations of dispersing agent in the slurries increased, the mixtures formed by adding them to latex aamples were increasingly darker in color. These qualitative observations indisated that surface active agent equilibria in one or both systems were ’disrupted when the two dispersions were mixed. When well stabilized latex-black dispersions were coprecipitated with a dilute solution of sodium chloride and sulfuric acid the larger
760 TABLE 111.
Yol. 43, No. 3
INDUSTRIAL AND ENGINEERING CHEMISTRY EFFECT OF
SALTCREAMIXG OR‘ 1\IASTER BATCH \rcI,CAhTzATE
Sample
B-349 100 50
5’ C. GR-S (X-526 latex), parts
HAF carbon black
B-348 100 50
. .. . _
2.5
B-3,50 100
B-339 100 50
60
...
acid diluted to 100 ml. Two hundred and seventy grams of each batch werr compounded with 8 grams of zinc oxide, 3.6 grams of sulfur, 5 grams of benzothiazyl disulfide, and 2.7 grams of stearic acid.
PROPERTIES
B-338 100 50
... ...
...
The physical properties of compounds and vulcanizates from these stocks were Acid compared (Table 111)with similar propshock flocculaerties of master batch B-338 that was tion 7:3 74 “shock” flocculated by adding a solution Poor Excellent of 8 grams of sulfuric acid diluted t o 1 liter with water to the black-latex mixtuiq. Photomicrographs of cut surfaces 1350 1180 1700 1430 of vulcanizates from the first four master 2210 ... batches (Figure 7 ) were made a t a mag1530 3290 3700 1610 nification of 14X with a Bausch & Lomb 3940 1580 450 570 Type H camera equipped with a 32-mm. 540 340 3licro Tessar lens. These photomicro470 300 graphs indicated that inferior physical aroaerties and carbon black dimersions I . were obtained when Liquid Marasperse and Silvacon 490 xere used in black-latex mixtures that weie creamed with salt. Uniformly poor vulcanizates were not obtained in all cases when salt creaming was employed, because some dispersing agents were found to be less sensitive to neutralization by sodium chloride than others. The poorest master batch, B-339, mas improved to one of excellent quality by using a shock-type flocculation method. Tensile strength values increased markedly as the carbon black dispersions were improved.
...
2.5
‘l‘ype of floccrilation
70
72
Good
Fair
Fair
50 100
1280 1810 2240 3710 3830 3660
50 100
540 430
1270 1820 2220 3410 3680 3470 590
1230 1860 2460 3340 3340 3340 570 440 390
Compounded Mooney viscosity Quality of black dispersion in vulcanizates 300% modulus Ib./sq. inch. (curing temperature 145” C.) Tensile strength, lb./sq. inch. Elongation a t break,
73
Cure, Min. 25 50 100 25
25
650
71
520
410
particles Qf copolymer-coated black coalesced first, after which the coprecipitate was coated with a layer of precipitated GR-S. This was confirmed by the fact that all latex-incorporated master batches were found t o be substantially noncrocking in nature. The term “noncrocking” described a compound in which the pigment was enveloped by elastomer. On several occasions it was noted that the methods used in flocculabing carbon black-lat,ex mixtures with sodium chloride and sulfuric acid affected the quality of vulcanizates from latex master batches. A check on the possible variables causing this condition was made and it was found that when sodium chloride was added first to cream the mixture and the sulfuric acid later to complete the flocculation, inferior products were often obtained. Typical experiments conducted during this investigation involved t,he preparation of small latex-black master batches in which Indulin A, Marasperse CB, and Liquid Marasperse solutions and Silvacon 490 suspension were used as dispersing agents for an HhF-type carbon black. The following formulas were used for preparing the carbon black slurries: Sainple
B-349
B-348
B-350
B-338
B-338
High abrasion furnace (HAW 100 100 100 black, grams 100 100 Dispersing agent solution, nil. 50’ 30b 3OC 50d 50’ ., . 10 10 ... ... 1 A‘ sodium hydroxide, nil. 350 360 360 350 360 Water, Inl. 10 grams of Indulin A reacted with 1.2 gram? of S a O H in water. Solution diluted t o 100 inl. Solution diluted to b 10 grams of Marasperse C B dissolved in water. 100 ml. 38 grams of 26,.4% solids Liquid Slafasperse solution diluted t o 100 ml. 10 grains of Silvacon 490 reacted with 2 g!ains,of N a O H i n 80 ml. of water for 20 minutes a t 90‘ C . Cooled suspension diluted t o 100 ml.
The carbon black, water, and sodium hydroxide solution, when the latter was required, were added t o the mixing bowl of a Waring Blendor. The ingredients were mixed for 30 seconds to moisten the carbon black, and dispersing agent solutions were added slowly to the pastes during mixing. After the dispersing agent was added, the fluid slurries were mixed for 2 minutes. The carbon black dispersions were added to 1200-gram portions of 16.7’% solids X-526 GR-S latex (200 grams GR-S) prepared by copolymerizing 71 parts of butadiene and 29 parts of styrene a t 5 ” C. in a sugar-free emulsion. Three grams of emulsified BLE (U. S. Rubber Co.) antioxidant were added to the latex before the black slurry was incorporated. Master batches B-349, 13-348, B-350, and B-339 were prepared by creaming each black-latex mixture with 24 grams of sodium chloride in 500 ml. of water and the flocculation was completed by adding 4 grams of sulfuric
TABLE IT’.
COMPARISON OF FLOCCL-LATION METHODS
An attempt was made to determine the reason for differencrs between salt weanling-acid flocculation and shock types of flocculation. One hundred grams of carbon black-latex mixtures containing various dispersing agents for the black were treated with sodium chloride solutions until creaming occurred (viscosit,y rise). The resulting “creams” or precipitates were filtered on a 54-mesh screen, treated with 0,5% sulfuric acid, washed, and dried. The filtrates from screening operations were completely precipitated with dilute acid, washed, and dried under the same conditions as the creams. Both fractions were weighed and analyzed for carbon black contents by the test method specified by the Office of Rubber Reserve (8) to determine the distribution of black and GR-S after creaming. Data collected for eight tests on 5 ” C. GR-S master batches containing 50 parts (33.3%) of HAF carbon black and four tests on similar master batches containing 50 parts of E P C carbon black are summarized in Table IT:. Some difficulty was encountered when attempts were made to separate and precipitate the solids
nISTRIBUTION O F
Dispersing Bgent
CARBOX BLACK.4FTER BLACK-LATEX CREAMING
% on Black
Precipitate yo of total Black black-GR-S content, %
Solids ~ Filtrate _ _ _ % of total Black black-GR-S content, %
H.4F Black, 5’ C. GR-SLatex Marasperse C B hIarasperse C B Liquid Marasperse Indulin A Silvacon 490 Marasperse C B Diesinate S-143u Marasperse C B Indulin A
+ + Maraspelse C B + Sil\acon 490
3.0 4 .0 3.0 5.0 5,0 2.0 1.0
28
8
55 60 50
33
47.8 44.6 45.2 39.3 49.7 42.3
72 92 45 40 50 67
28.5 31.1 16.8 15 6 10.5 25.1
?,o
47
45.3
53
11.0
2 0
43
47 2
37
8 1
1 u
10 E P C Black, ( 5 O C.) Latex 36 46.0 32 48 1 36 44.8 41 49.8
2.0 Triton R-100 2.0 Marasperse C B 2.0 Liquid Marasperse 2.0 Silvsoon 490 e IIercules Powder Co., W‘ilrnington, Del.
_
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
March 1951
761
CARBON BLACK DISPERSIONS IN GR-S COMPOUNDS
In much of the work t o follow, I method for cxamining elastomer compounds under the microscope was required. Allen’s (1)method for examining compounds was found to be unsatisfactory for determining small differences in the quality of carbon black dispersions in masticated compounds. Another method for determining undispersed carbon black in tread stocks requilpd a microtome for preparing specimens. Because a microtome was not immediately available, other methods were evaluated; the one found t o be most satisfactory involved fixing the thin film formed by expanding a bubble of sheeted compound.
MASTE RBATCH
i
I
0
W F W
1 E
3000
Y
4
5 P
About 20 grams of compounded stock were sheeted out on a 12inch laboratory rubber mill with the rolls in a hand-tight position. The sheet was spread out on a piece of cardboard and the apparatus, detailed in Figure 8, was placed in the position shown. The microscope slide cover glass that adhered t o the center glass tube of the a paratus bore a coating of Canada balsam or Permount (Fisher gcientific Co., Pittsburgh, Pa.) on both sides. When the pressure within the larger glass cylinder was reduced, a bubble of the compound was formed, which came in contact with the adhesive cover glass surface just before breaking. After a satisfactory film was deposited, the cover glass was removed and mounted, film side down, on a glass microscope slide. It was recognized that the specimens mounted in this manner were examined in a stretched form, but the forces acting upon the compound films were evenly distributed over their surfaces, which tended to “dilute” the carbon black dispersion by expanding the dispersing media. A Bausch & Lomb Model BAV-8 microscope; Fish-Schurman Zirconarc lamp; Bausch & Lomb Model H camera; and Eastman M photographic plates were used to obtain photomicrographs of mounted specimens. PROCESSING CARBON BLACK-LATEX M I X T U R E S
2000
8124
8119
8 2 0 0 E199 0201 8202 MASTERBATGM
8242 8241
CONTROL
MASTERBATCH
Figure 9. x
Effects of Homogenizing Black-Latex Mixtures
from the EPC black master batch filtrates, for which reason no analyses were reported. The amounts of precipitate formed during creaming varied from 8 to 60% of the total carbon black plus GR-S, and the carbon black contents varied from 39.3 to 49.8%. It was concluded that these highly loaded particles were responsible for the poor quality of vulcanizates prepared from master batches flocculated by salt creaming-acid floc procedures. Apparently the agglomerates formed were cemented tightly on drying t o produce tough, somewhat resilient particles that could not be completely disintegrated during compounding. No dispersing agent or dispersing agent-wetting agent combination investigated produced an even distribution of carbon black throughout the GR-S after addition of sodium chloride. For this reason it was evident that sufficient amounts of dispersing agents should be used to stabilize the black-latex mixtures during storage, and when flocculated, the materials should be coprecipitated as rapidly as possible.
After it had been established that carbon black-GR-S agglomerates formed just prior to or during the flocculating step were responsible for imparting poor qualities t o master batch vulcaniaates, several meshanical methods for obtaining more uniform coprecipitations were investigated. Preliminary experiments with a Waring Blendor, that was used for preparing carbon black slurries, indicated that certain improvements could be imparted to vulcanieates from master batches by violently agitating the carbon black-latex mixtures. Four latex-incorporated master batches were prepared t o determine the relative merits of very mild, 750 r.p.m. for 5 minutes, 750 r.p.m. for 30 minutes, and a violent type of black-latex mixing. These batches, described in Table V, were tested and it was found that the violent mixing produced vulcanizates having significantly higher 30070 moduli and tensile strengths with lower elongations a t break. Additional work indicated that these improvements could be reproduced. Test results that supported this statement were summarized and graphed in Figure 9. Because it was suspected that improved carbon black dispersions were responsible for the changes, specimens from several compounds mixed for vulcaniza.tion were examined under the microscope. Plates 19 and 20 (Figure 10) represent carbon black dispersions resent in compounded stocks from 5 ” C. GR-S latex master Katches contained 50 parts of an HAF black that was slurried with 2.5% Marasperse CB on the black. Plates 24 and 25 represent black dispersions in stocks from master batches in which 4.0y0 Indulin A, added as the sodium salt, was used to prepare the carbon black slurries. The improved dispersions shown in plates 20 and 25 were obtained by violently mixing the black-latex mixtures before flocculation. These photomicrographs, taken a t a magnification of 1300X, indicated that the carbon black in stocks containing Indulin A was better dispersed than in stocks containing acids derived from Marasperse CB. However, more of the former material was used in preparing the black slurries, which would account for these differences. . Several large units for homogenizing carbon black-latex mixtures that could be adapted to plant scale operations were investi-
762
INDUSTRIAL AND ENGINEERING CHEMISTRY
VOl. 43,
No. 3
liminary cxpcrirncnts indicated that two cationic surface active agents, Hyamine 2389 and Amine 220, were compatible with flocculating solutions containing sulfuric acid and could he used to neutralize condensed sodium alkylnaphthalene sulfonate types of surface active agents. A number of other organic nitrogen compounds were subjected to the following tests: Dilute solutions (0.5 gram
per ml.) of the amines in 2.5%
acetic acid were prepared and 250-gram portions of 20% EPC black slurries containing 37” Triton R-100 oq the black were titrated with the solutions to the point of sharp viscosity rise. The dilute amine acetate solutions were mixed with acidified Triton R-100 solutions to determine whether or not precipitates were formed. The dilute amine acetate s o l u t i o n s were mixed with sodium chloride-sulfuric acid solutions used for flocculating GR-S l a t e x t o d e t e r m i n e whether or not the amine sulfates precipitated. Figiire 10. Improved Carbon Black Dispersions Produced by Homogenizing BlaclrPortions of the serum obLatex Mixtures tained by flocculating a 9R-8 latex polymerized a t 5 C., which contained 0.1yo Triton R-100 on the GR-S, by a standard sodium chloride-sulfuric gated and it was found that an E n t o l e t ~ r(Safety Car Heating acid procedurp were titrated with 0.0005 gram per ml. soluand Lighting Go., Ken, Haven, Conn.) could be used for this purtions of the amine acetates. The point a t which substantially pose. The peripheral or tip speed of the rotor in the Entoleter, all suspended “fines” were flocculated served as an end point. which was 12,000 feet per minute, exceeded the tip speed of the The data rrported in Table VI1 served to show that the polyWaring Blendor impeller, which was from 5000 to 8000 feet per ethylene polyamines, particularly the materials of higher molecuminute. For this reason, it was anticipated that a t least the same lar weight, were very effective for neutralizing dispersing agents or gieater benefits could be obtained by treating the carbon blackin acidic, aqueous media. Additional experiments were perlatex mixtures with the former machine. A 5-hp. Entoleter was formed t,o check the relative merits of tetraethylenepentamine installed in the pilot plant and two runs made thus far have indiand Hyamine 2389. Two portions of the same latex used in the cated that definite improvements in abrasion resistance properwork above were further stabilized by adding 0.2 and 0.4% on the ties were imparted to vulcanizates from master batches prepared GR-S of Triton R-100 before the two latices were flocculated by from black-latex mixtures passed through this unit (Table VI). salt creaming and sulfuric acid flocculating procedures. Portions KO handling troubles were encountered when passing the mixed of the cloudy serums were titrated with 0.0005 gram per ml. soludispersions through the homogenizer a t rates up t o 15 gallons per tions of tetraethylenepentamine and Hyamine 2389 t o the point minute, but it was noted that a very spongy, voluminous crumb where the suspended copolvmpr was precipitated. The results of was obtained after the mixtures were coprecipitated. Coprecipiof this work (Table TIII) and subsequent experiments indicated tates of this type were more easily washed and dried than the more that the polyethylene polyamines were the most effective anionic compact crumbs produced in standard operations. DEACTIVATION OF DI SPER S I 1 G AGENTS
When lignin or sulfolignin types of dispersing agents up to 3.0% on the carbon blacks were used for preparing slurries for master batches, little trouble was encountelEd in obtaining rapid and complete flocculation. On the other hand, materials such as the condensed sodium salts of alkylnaphthalene sulfonates, that were not neutralized by inorganic salts and acids, could not be tolerated in concentrations greater than 2.0% on the black. Conditions under which these materials could be used in larger amounts were inveetigated. Pre-
T.4BLE
\?, I,ABORATORY
XIASTER B A T C H E S FROXI
Ssiuple j0 C. GR-S (X--132 latex) parte H A F carbon black Daxad 11 hIarasperse CB Black-latex treatment
B-I 5 2
B-156
100 50
100 50
100
...
1.25 Mixed with glass stirring rod
300% modulus, lb./sq. inch (cured at 145’ C.) Tensile strength, lb./sq. inch. Elongation, %
HOJIOQENIZED BLACK-LATEX MIXTURES
B-124
Cure Alin. 23 50 100 28 50 100 25 50
100
2.5
...
Impeller a t
750 r.p.m.
5 mine.
50 2.5
Imdeiier a t 750 r.p.m. 30 mins.
270
260
230
1260
1240
1230
1190
600 1840 3000
740
2780 3180 1010 896 630
530
940
730
650
560
500 1010
3050 640 720 560
B-119 100 50
...
1.25
Waring Blendor, 1 Inin. 410 920
1420 1870 2960 3310 900 675 565
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
March 1951
163
30" to 70' C. The combined serums from filtering and washing we- analyzed MIXTURES for sumended solids content t o determine Master batch 5-2763 3-3150 5-3151 5-2945 material losses that were reported as 5' C. GR-S (X-526latex), parts 100 100 100 100 grams loss per 100 grams of master H A F carbon black 55 55 55 55 Marasperse C B 1 3 , 1.3 1.0 10 batch. The results of this work (Figure Black-latex through Entoleter N O Yes No 11)indicated that a temperature of 50 'C. COMPOUNDINQ FORXULA, PARTS for the flocculating solution was desirable 155 3 Zinc Master oxide batch for coprecipitating these types of carbon Sulfur 2.5 black-latex mixtures. The conclusion Benzothiazyl disulfide 1.5 waa restricted no further because blackCompounded Mooney viscosity 79 81 75 latex temperatures would be difficult t o Cure, IMin. maintain a t levels around 70" C. where 300% modulus lb./sq. inch 1610 25 1470 1260 additional improvements in flocculation (cured a t 148' C.) 50 2390 2380 1970 100 3320 3230 2590 2620 were indicated. Tensile strength, Ib./sq. inoh. 50 3310 3540 3710 3260 Before this method for improving Elongation a t break, % 50 400 450 500 470 Abrasion rasistance rating, 130 148 116 156 flocculation was recommended, the effect % of standarda Of temperature variations during a Laboratory abrasion resistance determined using variable slip abrader and E P C blaok-GR-S latex master batoh vulcanieate a s standard. lation on the physical properties of compounds and vulcanizates from master batches was determined. The method for preparing each series of batches was dispersing agent deactivators. Tetraethylenepentamine used in standardized in so far as possible to eliminate all variations othor amounts that were approximately one tenth of the weight of conthan flocculation temperatures. The master batch compositions densed sodium alkylnaphthalene sulfonates in latices was reand compounding formulas used were as follows: quired t o obtain the best flocculations.
TABLE VI. PILOTPLANT MASTERBATCHES FROM HOMOQENIZED BLACK-LATEX
3
MASTEBBATCHCOMPOSITION
TABLE VII.
ANIONICDISPERSING AGENTDEACTIVATORS
Parts 100 50 1.6 1.5 0.2
5 ' C. GR-S (X-510GR-S latex) IL4F black BLE i & a , CB
% on Black Precipitate Precipitate yoon GR-S t o Gel Slurry
Material
with Triton with NaCIR-100 HzSOd S o h .
Tetraethylenepentamine 0 .9 Yes Triethylenetetramine 1.0 Yes Dodecylamine 0.7 Yes Diethylenetriamine 1.2 Yes Rosin amine Da 1.1 Yes Amine 220b 0.9 Yes Bone (animal) k l u e 4.3 Yes Hyamine 2389 1.0 Yes Benzvl trimethvl ammonium ohlotide 0.9 No Di-n-amylamine 0.8 Yes Aniline 1.1 NO 1.1 o-Phenylaniline Yes Monoethanolamine 3.7 No 2.4 Diethanolamine No Triethanolamine 2.1 No Ethylenediamine 3.4 NO > 10 Acetic acid No a Hercules Powder Co Wilmington Del Carbide and Carbon"Chemica1s Cdrp., New York, Rohm & Haas Co., Philadelphia, P a .
'
No NO Yes NO
Yes No No No NO
No NO
NO No No
No
No
No
t o Clear Serum 0.002
0,008 0.030 0.033 0.038 0.Q48 0.048 0.052
COMPOUNDINQ FORMULA Master batch Zinc oxide Sulfur BenzothiaFyl disulfide Stearia acid
150 5.0 2.0 3.0 1.6
N.G. N.G. N.G. N.G. N.G.
N.G.
N.G. N.G. N.G.
N. Y.
Most of the dispersing agents used for dispersing carbon blacks in water were found t o be adsorbed on the carbon black surfaces. For this reason the concentrations of dispersing agent deactivators already mentioned were not required for coprecipitating carbon black-latex mixtures that contained relatively high concentrations of Triton R-100, Daxad 11, or similar materials. When EPC black-GR-S (45 C. polymerization) latex mixtures containing 1.5 parts (3% on black) of Triton R-100 were treated with sodium chloride-sulfuric acid solutions, a considerable amount of suspended fines remained in the serum. In most cases these fmes were agglomerated into recoverable particles by adding 0.005 to 0.025 part of tetraethylenepentamine to the crumb slurry.
FLOC SOLUTION TEMP, * C
Figure 11. Temperature Variations in Latex Master Batch Flocculation
O
auks on the compounds and vulcanieates were ain the graphs shown in Figure 12. It q-as indicompounded Mooney viscosity and high tensile were obtained for batches that were prepared by
FLOCCULATlON TEMPERATURES
It was found that the temperatures a t which carbon blacklatex mixtures were flocculated influenced the completeness of coprecipitation. A series of HAF black GR-S (5" C. polymerization) latex master batches, purposely formulated to produce more than normal amounts of nonfilterable solids during flocculation, were prepared in the laboratory by varying the temperature of black-latex mixtures and flocculating solutions over the range of
OMPARISON OF
TETRAETHYLENEPENTAMINE AND % on GR-S t o Clear Serum
Tetraethylenepentamine Hyamine 2389
+
+
Original latex
Original latex 0.2 part T r i t o n R-100
Original latex 0.4 p a r t T r i t o n
0.002 0.052
0.012 0.141
0.020 0.280
R-100
IN DU STR IA
764
L A N D E N G I N E E R IN G C H E M,IS T R Y
a t 50" C. It was important to note that these were about the same conditiona under vhich the best flocculations were obtained. Moduli and elongation values did not pass through minimum or maximum points, but a trend toward slower curing compounds v hcn flocculating tcmpcratures n-cre increased \vas apparent.
BLACK- LATEX TEMP., 'C.
50
30
Vol. 43, No. 3
70
, c 0
L"
'BO
SUMMARY
). z
Y
Several conventioiial test methods and new analytical procedures that vxrc developed were used to investigate various phascxs of producing GR-S latex-carbon black master batches. The investigations revealed the f o l l o ~ ~ i ninformation g about carbon black slurry preparations, carbon black properties, the stability of carbon black-latex systems, carbon black dispersions in mastcr batch compounds, processing carbon black-latex mixtures, and flocculation variables.
0 0
0 L
60
1-30
----1
I
E
-
50-70FLOG. SOLUTION TEMP., *C.
BLACK- LATEX
T E M P . *C.
2600
2 W In^
$5 I 'g
rr0 g
2200
1000 -30-
-50FLOC.
-70-
SOLUTlON
BLACK-LATEX
50
30
TEMP.,
I
TEMP.. 'C.
70
-50-
-30-
*C.
-70-
F L O C . SOLUTION TEMP., ' C .
"""I
BLACK- L A T E ? TEMP.,*C.
mmm 30
60
70
A linear relationship existed between the dispersing agent requirements of slurries and their carbon black contents within the range of 15 to 2570 carbon black. Sodium hydroxide increased the dispersing efficiencies of most anionic dispersing agents for carbon black in water. The benefits imparted by this hydroxide varied with the type of dispersing agent and carbon black. Twenty products were found t o be effectivc dispersing agents for carbon black in water. Dispersing agent and sodium hydroxide concentrations both affected the Darticle size of dispersed carbon black in aqueous dispersions. A certain number of loose aaelomerates of carbon black could be present in slurries a-ithout -&creasing their viscosities appreciably. The sodium hydroxide requirements (acidity) of various shipments of easy processing channel blacks were significantly different. Each carbon black classification-i.e., HAF, EPC, HNFwas found to include materials with relatively wide variations in dispersing agent requirements and particle size indexes. For the system carbon black-water-dispersing agent-alkali the smallest amount of any one dispersing agent was required when the carbon black was mixed with a solution of alkali in water and the dispersing agent added in increments while the mixture was agitated. Unpelletized or "free" types of carbon blacks could be used satisfactorily for making latex master batches. When sodium chloride creaming-sulfuric acid flocculating processes were used to coprecipitate carbon black-latex mixtures inferior products were obtained. The highly loaded particles formed during creaming, which contained from 40 to 5oy0carbon black, were responsible for poor vulcanizate quality. Vulcanizates from master batches prepared from homogenized carbon black-latex mixtures were found to exhibit higher than normal moduli and tensile strengths and improved resistance to abrasion. These changes in physical properties were produced by improved carbon black dispersions. The temperature a t which carbon black-GR-S latex mixtures were flocculated influenced the completeness of coprecipitation and the properties of vulcanixates from master batches. The best temperature for flocculation was 50' C. Polyethylene polyamines were the most effective materials for deactivating condensed sodium alkylnaphthalene sulfonate types of dispersing agents.
rr L
2
coIvcLusIoNs
400
E
m-Y
2% z
pF: 4 -
5
200
J
0
30-
-30-
L
FLOC
Figure 12.
-70-
SOLUTION ? € U P . ' C
Effect of Flocculation Temperature on Master Batch Properties
I n addition t o the advantages cited in a previous publication ( 5 ) , other benefits derived from using latex master batch compounds have been recognized. Foremost, sufficient information regarding the wearing properties of automobile tire treads has been obtained to indicate that tire treads fabricated from latex master batch stocks exhibit about a 7% improvement in roadwear quality over similar treads fabricated from dry mixed carbon black-GR-S compounds. It is predicted that the research efforts described herein that were expended on problems involved in producing latex-incorporated carbon black master batches will be instrumental in obtaining greater quality improvements and reduce the cost of manufacturing these products.
INDUSTRIAL AND ENGINEERING CHEMISTRY
March 1951
ACKNOWLEDGMENT
This work was carried out under the sponsorship of the Office of Rubber Reserve in connection with the government’s synthetic rubber program. The authors wish to thank that agency for permission to release this publication and to thank R. L. Provost, W. H. Leukhardt, a n d R. A. Reynolds, who supervised the pilot plant work involved in evaluating methods for homogenizing carbon black-latex mixtures. The assistance of J. A. Reynolds, who drew the graphs and supplied information for Figure 1, J. W. Zayatz who conducted many of the master batching experiments, and the physical testing laboratory personnel is appreciated. LITERATURE CITED
(1) Allen, R. P., IND. ENQ.CHEM.,ANAL.ED.,2,311 (1930). (2) Daniel. F.X..Rubber Chem. and Technol.. 13,619-32 (1940). (3j Daniel] F. K.; and Goldman, P., IND.ENG.CHEM.,ANAL’.ED.,
18,26 (1946).
765
(4) McMahon, W., and Kemp, A. R., IND.ENQ. CHEM.,36, 735 (1944). (5) Madigan, J. C., and Adams, J. W., Chem. Eng. Progress, 44, 81520 (1948). (0) Marathon Corp., Rothschild, Wis., Physical Chemistry Laboratory Report, “Study of Effectiveness of Marasperse CB as the Dispersing Agent for Aqueous Suspensions of Carbon Blacks,” Oct. 11, 1946. (7) O’Connor, H.F., and Sweitzer, C. W., Rubber A g e , 54, 423-7 (1944). (8) Reconstruction Finance Corp., Office of Rubber Reserve, “Specifications for Government Synthetic Rubbers,” revised ed., Jan. 1, 1949. (9) Riley, G. C., “Evaluation of Dispersing Agents,” private communication from Rohm & Haas Go. (10) Rongone, R. L., Frost C. B., and Swart, G. H., Rubber Age, 55, 577-82 (1944). (11) Tesoro, G. C., Donahue, W. T., and Casey, J. A., Ibid., 60, 31920 (1946). RECEIVED April 21, 1950. Presented before the Division of Rubber Chemist r y at the 117th Meeting of the AMERICAN CHEMICAL SOCIETY,Detroit, Mich.
Spray Gun for Polymeric and Solutions
development I
CARL A. NIELSON AND FRED LEONARD A R M Y PROSTHETICS RESEARCH LABORATORY, A R M Y MEDICAL CENTER, W A S H I N G T O N , D. C.
I n the course of an investigation of processing methods for the fabrication of a cosmetic glove to be worn by amputees, from a synthetic elastomeric type latex, it became necessary to devise a spray gun which would be free from the troublesome difficulties of cobwebbing and clogging attendant the use of the conventional types of guns. It is possible, using this gun, to spray high solids (55 to 65%) latices of natural rubber, synthe latices of ethyl acrylate and acrylonitrile and ithout specifically compounding for spraying applications. Films 0.030 inch thick by 9 inches long b y 7 inches wide have been sprayed on a glass plate using ethyl acrylate-acrylonitrile copolymer latices. The gun eliminates, in the samples tested, the necessity for diluting the latices, addition of stabilizers, and other procedures for preparing the samples for spraying. The major difficulties of spray gun clogging and cobwebbing have been eliminated.
*
c
LOGGING of spray guns and cobwebbing are the major difficulties to be overcome in the spraying of high solids natural and synthetic rubber latices and concentrated polymeric solutions. Indeed, present practice dictates the use of dilute emulsions and addition of stabilizing agents to latices; techniques for spraying polymeric solutions such as lacquers involve use of dilute solutions, low molecular weight polymers, hot spraying, or the use of vehicles with high solvent power. These methods have serious disadvantages economically and sometimes result in films with inferior properties-for example, addition of stabilizing agents to emulsions usually results in increased water sensitivity of the film, and the use of dilute emulsions increases the time necessary to build up a film of desired thickness. In polymeric solutions, the incorporation of low molecular weight resins to reduce viscosity may deleteriously affect the strength properties of the film. Despite the use of the artifices mentioned, clogging of the conventional spray gun and cobwebbing often are not eliminated.
SOL VENT VAPOR OLYMERIC EMULS/ON
OR
sourioN
ASSEMBLY H O L D E R SHOWN IN SECTION
Figure 1. Detail and Assembly of Spray Gun
