IL36995A - Carbon black pigments and rubber compositions - Google Patents

Description

CARBON BLACK PIGMENTS AND RUBBER COMPOSITIONS black products. In particular, this invention relates to novel' and important carbon black products which exhibit relatively low porosity and possess an unusually high numerical product for a combination of hydrogen content in millimoles per gram and the specific surface areas thereof and also an exceptionally high ' numerical product for a combination of carbon monoxide con- tent expressed in millimoles per gram of the particular carbon blacks and the specific surface areas in square meters per gram · thereof. The numerical products are hereinafter referred to as the activity factors of the present novel carbon blacks. Furthermore, this invention relates to the use of the novel active carbon blacks in the preparation of new and useful natural and synthetic rubber compositions having improved physical properties.

Normally, there have been widely employed as fillers and reinforcing pigments in the compounding and preparation of rubber compositions various conventional carbon blacks known heretofore. Ordinarily, the conventional carbon blacks are effective in the preparation of rubber vulcanizates having improved reinforcement properties such as tensile strength or elongation. The improvement in properties exhibited by an elastomeric article or rubber stock filled with a carbon black will depend to a great extent upon the type of elastomer util- ized and the . particular carbon black incorporated therein. How- ever, the development of suitable carbon blacks for use .with several of the more recently developed synthetic rubbers has proven difficult as a result of the increased inertness and ^ reduced reactivity thereof. Typically, the newer synthetic rubbers are commercially desirable for use. as general purpose or heavy duty rubber stocks because of the low amount of unsaturation contained therein'. Although some improvements have been achieved, for example, by aftertrea ing carbon blacks,' it has now been made possible by using the Active carbon black products of the present invention to provide finished products having still further improved tensile, hardness, modulus and abrasion-resistant qualities.

Accordingly, it is a primary object of this invention to .provide' a .novel ty.pe of active carbon black products.

It is' a further object of this invention to provide a suitable carbon black reinforcing additive for natural and synthetic rubbers which provides, the desired physical properties to the resultant composition.

Other objects and advantages of the present invention will be apparent to those skilled in the art from the following detailed description and claims.

In accordance with this invention, it has been found that the. above and still further objects are achieved by the preparation of novel active .carbon blacks which possess rela-, tively low pbrosity and which are further characterized by •having an unusually high numerical product of carbon monoxide content expresse n m mo es per gram an BET specific sur¬ face area where the carbon black is non-porous or "t" curve ^ specific surface area where the black is porous, an unusually high numerical product of hydrogen content and non-porous sur- 5 face area : expressed in similar units, and additionally, a rela¬ tively high dibutyl phthalate. (DBP) absorption value. Specific¬ ally, the novel carbon blacks possess an activity factor numer¬ ical value representing the numerical product of non-porous \ surface area of the blacks in square meters per gram multiplied 10. by the hydrogen content in millimoles per gram which is greater than. 175 and also a numerical product of BET surface area, in the instance of non-porous blacks, or "t" curve area where "the blacks exhibit. porosity , and the carbon monoxide content, which „' ". is at least 62, a ratio of non-porous "t" curve area to total 15 BET surface area of the carbon black which is at least about 0.8, . ■ ■ and a DBP absorption value of at least 110. It is preferred, however, that in respect ' to . this novel class of carbon blacks, .. . the. numerical value for activity factors representing products •of. hydrogen content and non-porous surface area exceed 185 and more preferably be in the range of 210 to about 250, and in ' "' · .' combination therewith,' the numerical value for the activity factors representing carbon monoxide content and non-porous • surface area should vary from about 62 to about 125, and in a more preferred embodiment, from about 65 to about 99. Moreover, • \ · ! . :. .with regard to the porosity of the active carbon blacks it is surface area of the carbon blacks to the total specific sur- ^ face area thereof exceed 0.9. It is further preferred that the DBP absorption values of these carbon blacks range from about 130 to about 180 or higher and, in a particularly pre- • ferred embodiment, the novel active carbon blacks possess DBP . values ranging from about 150 to 170.

Generally, amounts of the active carbon black product ranging from about 10 to about 250 parts by weight can be used for each 100 parts by weight of rubber in order to impart a significant degree of reinforcement thereto. It is,, however, preferred to use. amounts varying from about 2Q to about 100 ". parts by weight of carbon black per 100 parts by weight of rubber and especially preferred is the utilization of from about 40 to about 80 parts of carbon black per 100 parts of rubber. . . . ...·' _ The rubbers for which the novel active carbon blacks . of this invention are effective as reinforcing agents include ■ natural rubber and synthetic rubbers. Amont the rubbers suit- able for Use with the present invention are natural rubber and its derivatives such as chlorinated rubber; copolymers of from about 10 to about 70 percent by weight of styrene and from about 90 to about' 30 percent by weight of butadiene such as a' -■ . dopolymer of 10 parts styrene and- 90 parts butadiene, a co- \ ' ■ · polymer of i9 parts styrene and 81 parts butadiene ,. a copolymer 'of 23.5 parts styrene and 76.5 parts butadiene, a copolymer of 30 parts styrene and 70 parts butadiene, a copolymer of 43 parts styrene and' 57 parts butadiene and. a copolymer of 50 parts styrene and 50 parts butadiene; polymers and copolymers of conjugated dienes such as polybutadiene , .polyisoprene , polychloro- prene, and the like, and copolymers of such conjugated dienes with an ethy.lenic group-containing .monomer copolymerizable therewith such as styrene, methyl styrene, chlorostyrene, aerylonitrile , 2-viny lpy idine , 5 -methy 1-2-viny lpyridine , 5 -ethy 1-2 -vinylpyridine , 2-methyl-5-vinylpyridine, alky l-subs tituted acrylates such as methyl aery late, alky l-subs tituted methacry lates such as methyl methacry late , ethyl acrylate, ethy 1 methacrylate , ethyl vinyl ke.tone., methyl i&opropeny 1.ketone, .methyl vinyl ether, alpha-- methylene carboxylic acids and the esters and amides thereof such as acrylic acid and dialky lacry lie acid amide; also suitable for use herein are copolymers of ethylene and other high alpha olefins such as propylene, butene-1 and pentene-l ; particularly preferred are the ethylene-propylene copolymers wherein the ethylene content ranges from 20 to 90 percent by weight and also, the ethylene-propylene polymers which, additionally contain a third monomer such as dicy lopentadiene , 1,4-hexadiene and methylene norbornene. The heretofore- described class of novel active carbon blacks are readily- ^prepared by contacting a carbon black-producing feedstock with a stream, of hot combustion .gases flowing at an average for preparing the novel carbon blacks of the present inventions, will be described in greater detail hereinafter. i .In the preparation of the hot combustion gases employed in producing the active carbon blacks of the present invention there are reacted in any conventional .combustion chamber a liquid or gaseous fuel and an oxygen-containing oxidant stream. Exemplary oxidant streams include air, oxygen,' mixtures of air and oxygen, nitrogen and oxygen, and other mixtures of oxygen with common gases. It is preferred, however, that the oxidant stream to be used in the present invention comprise an amount greater than about 507o molar concentration of oxygen. Among the fuels suitable for use in' reacting with an oxidant stream in a combustion chamber to 'generate hot combustion gases there are included any of the readily combustible gas, vapor or liquid streams such as hydrogen, carbon monoxide , 1 methane , acetylene, alcohol's., kerosene and the like. It is generally preferred, however, to utilize fuels having a high content of carbon-containing components and, in particular, hydrocarbons.. For example, streams rich in methane such as natural gas and modified or enriched natural gas are excellent fuels as well as other streams containing high amounts of hydrocarbons such as various petroleum gases and liquids and refinery by-products including ethane through pentane fractions, fuel oils and the like. In general, the heavier and more viscous tars and residual • ype o s s ou p e e a y e use w e more concentrate or relatively pure oxygen-containing oxidant streams. ~* The novel active carbon blacks of the present invention are prepared by reacting the aforementioned combustion reaction products with any of a wide variety of hydrocarbon feedstocks which are readily yolatilizable under the conditions of the reaction. Suitable for use in the present invention as hydrocarbon feedstocks are unsaturated hydrocarbons such as acetylene, olefins such as ethylene, propylene, butylene, aromatics such as benzene, toluene and xylene, saturated hydrocarbons such as kerosenes, naphthalenes, terpenes , ethylene tars, aromatic cycle stocks and the like. " : '.

Accordingly, the above-described novel class of active carbon blacks are prepared by reacting a carbon black-yielding hydrocarbon feedstock with hot gaseous products of an initial combustion reaction which are flowing at a high linear velocity in a suitable reaction zone. The hot combustion gases are readily, generated by contacting the desired oxidant stream with a combustible fuel in any type of conventionally known burner designed to produce a stream of hot combustion gases flowing at a high linear velocity. In a preferred embodiment of the present invention, a combustible fuel is contacted with an- oxidant stream containing at least 507o molar concentration ■ of oxygen in a suitable · burner under a pressure . ranging up to about 120 psig with the mos preferred combustion varying, from about 5 to about 75 psig. Under these conditions, there is , produced a stream of gaseous ■ combustion products possessing sufficient energy to convert a carbon black- ielding hydrocarbon feedstock to the desired active car.bon black products. The resultant combustion gases emanating from the combustion zone may attain temperatures up to and' greater than 5000 to 6000°F, with the most preferable temperatures for the present process' being at least about 3000°F. The hot combustion gases are propelled in an upstream direction at a high, linear velocity which may be effectuated by passing the combustion gases through any suitable passage or inlet which- may be tapered or restricted such as a conventional venturi throat. Into the resultant stream of .hot combus.t.i.on ..gas.es traveling .at a high velocity there is then introduced a suitable carbon black-yielding hydrocarbon feedstock thus insuring a high rate of mixing and shearing of the hot combustion gases and the. hydrocarbon feedstock so as to rapidly and completely decompose and convert the feedstock to •the novel carbon blacks in high yields. The manner in which the carbon black-yielding hydrocarbon feedstock is introduced into the hot combustion gases traveling upstream at a high linear velocity may be varied considerably. For example, the hydrocarbon feedstock may be introduced into the hot combustion gases through an opening in the reaction chamber which causes the entry • to be in a direction perpendicula ' to the longitudinal "axis of the flow of combustion gases. Alternately, the hydrocarbon feedstock may be introduced through a suitable probe type device into the reaction zone in a direction paralleling that of the flow of the combustion gases. It is preferred, however, that the hydrocarbon feedstock be injected substantially transversely from the periphery of the stream of hot combustion gases in.the form of a single or a plurality of small, coherent jets which penetrate into the interior regions of the stream of combustion gases. It is to be understood, of course, that in practicing the present process the hydrocarbon feedstock may be introduced into the reaction zone as a liquid or liquid spray by means of a conventional atomizer or spray nozzle as well as in the form of a gas or vapor. Following the period .of .reaction'i.n .the .reaction zone, the effluent gases containing the novel active carbon black products suspended therein are passed downstream to any conventional cooling and separating means whereby the novel active carbon blacks are recovered." . The separation of the carbon black from the gas stream is readily accomplished by conventional means such as a precipitator, cyclone separator and bag filter. The amounts of oxidant gas, fuel and carbon black-yielding hydrocarbon feedstock may be readily determined to obtain the desired active carbon blacks having controlled physical properties. Moreover, although the residence time ,for each instance depends upon the particular reaction conditions and the particular carbon black desired, the residence time of the present process may vary from about 1 to about TOO milliseconds, or even shorter periods of time.

The following testing procedures are used 'in the determination and evaluation of the physical properties and efficiency of the novel active carbon blacks of the present invention; DBP Absorption - In accordance with the procedure set forth in ASTM D-2414-65T, absorption characteristics of pelleted carbon blacks are determined. In brief, the test procedure entails adding dibutyl phthalate (DBP) to a pelleted carbon black until a transition from a free-flowing powder to a semi- plastic agglomerate results in a sharp increase in viscosity.

Carbon Monoxide Content - Carbon monoxide content of -carbon blac-ks -is determined by a pyrolytic volatile analysis · (PVA) technique wherein the carbon black is devolatilized at a linear heating rate up to a temperature of 1500°C and the gases evolved thereby are quantitatively determined by gas chromato- » graphic procedures. A more complete description of the pyrolytic volatile analysis procedure appears in an article by Cotten, Boonstra, Rivin arid Williams entitled "Effect of Chemical Modification of. Carbon Black on Its Behavior in Rubber," Kautschuk Und Gummi. Kuns ts offe 22 (9), 477-485 (1969).

Hydrogen Content - Hydrogen content of carbon blacks is determined by a pyrolytie volatile analys is . technique wherein the carbon black is devolatilized at a linear heating rate up to a temperature of 1500°C and the evolved gases are quantitatively determined by gas chromatography. A more complete description of this procedure appears in an article by Cotten, Boonstra, Rivin and Williams entitled "Effect of Chemical Modification of Carbon Black on Its Behavior in Rubber," Kautschuk Und Gummi . Runst s toffe 22(9), 477-485 (1969).

°^£L1U ^ac e ea - The total surface area of the carbon blacks is measured in accordance with' the well-known.

BET technique utilizing nitrogen isotherms. The BET (Brunauer-Emmct-Telle ) method is ' completely described in an article appearing in the Journal ■ of the American Chemical Society, vol. 60, page 309 (1938). Surface areas obtained in the usual manner by BET technique include the external surface area as well as the internal surface area contributed by the presence of pores. "t" Area - Surface area of carbon black measured in accordance with a "t curve method" is referred to herein as "t" area. The "t curve method" for evaluating microporos ity of carbon black is a comparative procedure and is fully described i an article by Mikhail, Brunauer and Bodor entitled "Investigations of a Complete Pore Structure Analysis" in the Journal of Colloid and Interface Science, vol. 26, pages 45-53 (1968). The technique taught in this article' is followed with the exception that the "master t curve" utilized is one for which Sterling FT carbon black extracted with benzene serves as the non-porous, solid standard adsorbent inasmuch as it is more advantageous to employ a carbon black as the master selected as the standard, i. e. , Sterling FT, is manufactured and sold by Cabot Corporation and is characterized by having a Nigrometer scale value of 107, a surface area of 13 square meters per gram, an electron micrograph particle diameter of 180 millimicrons and an oil absorption value of 38 lbs. of oil per 100 lbs. of carbon black.. The difference, if. any, between the surface area value obtained on a carbon black sample by BET technique and by means of the " t curve method" provides a measure of the extent of porosity in the carbon black.

• The invention will be more readily understood by .. reference to the following examples which describe the detailed preparation of representative compounds. There are, of course, many other forms' of this invention which will become obvious to one skilled in the' art , once the invention has been fully disclosed, and it will accordingly be recognized that these examples are given for the purpose of illustration only, and are not to be construed as limiting the scope of this invention in any way; . . .

Example 1 In this example, there is employed a suitable reaction apparatus provided with means for supplying the combustion gas-producing reactants, i.e., a fuel and an oxidant stream, either as separate streams or as pre-conibus ted gaseous reaction products and also means for supplying the carbon black-yielding hydrocarbc of any ..uitable material, such as metal and either provided ^ with a refractory insulation or surrounded by means for cooling with a recirculating liquid which is preferably water.

Additionally, the reaction apparatus is equipped with temperature and pressure recording means, means for quenching the carbon black-forming reaction' such as spray nozzles, means for cooling the resultant carbon, black product and means for separating and recovering the carbon black from other undesired by-products. Accordingly, in carrying out the present process for preparing this class of novel active carbon blacks, the following procedure is employed. In order to obtain the desired flame, there are charged into a combustion zone of the apparatus through one or more inlets oxygen at a rate of 2000. SCFH and natural gas at a rate of 625 SCFH thereby generating a stream of combustion gases flowing in a downstream direction at a high linear velocity. In a preferred embodiment of the present invention, however, the rapidly flowing stream of combustion gases is passed through a constricted or tapered portion of the apparatus having a fixed cross-section or throat such as a conventional venturi throat in order to increase the linear velocity of the stream of combustion gases. There is then introduced into the resultant stream of hot combustion gases a carbon black-yielding hydrocarbon feedstock through one or more passages or inlets located peripherally to the stream of combustion gases at a rate is Sun ay DX which is a fuel having a carbon content of 91.1% by weight, a hydrogen content of 7.9% by weight, a sulfur con- tent of 1.3% by weight, a hydrogen to carbon, ratio of 1.04, a 5 75. M.C.I. Correlation Index of 133, a specific gravity in accordance with ASTM. D-287 of 1.09, an API gravity in accordance with • · ASTM D-287 of -2.6, an SSU viscosity (ASTM D-88) at 130°F of 350, an SSU viscosity (ASTM D-88) at 2l6°F of 58 and an asphaltenes content of 5.7 percent. The reaction conditions 0 used in this instance are such as to provide an overall combustion of 30.1 percent. The carbon black-forming reaction is then quenched with water in a separate zone downstream of the reaction zone and the resultant carbon black-containing gases arc sub ected, to the conventional steps of cooling, sep-5' aration and recovery of the carbon black product. The carbon black product thus obtained is characterized by having a carbon monoxide content of 1.54 millimoles/gm, a hydrogen content of 3.I6 millimoles/gm, a BET total surface area of 130 m2 /gm, a "t curve" area of 130 m2/gm, a ratio of RET area to "t" area of 0 1.0, an activity factor representing the product of hydrogen content and non-porous surface area of 411, an activity factor representing the product of carbon monoxide content and non-porous surface area of 237, and a DBP value of 151. Other characteristics of the resultant black product include a Nigrometer scale 5 reading of 80 which value represents the relative amount of an a -t nt ng strengt o w c va ue represents t e re ative covering power of a carbon black when incorporated in a one. part in thirty parts ratio with a standard zinc oxide dis-. persion in a standard oil and compared to a series of standard reference blacks tested under similar conditions.

Exaup le A suitable reaction apparatus as described in Example 1 is charged with oxygen at a rate of 2000 SCFl-1 and natural gas at a rate of 625 SCFH in. order to produce a suitable flame for carrying out the reaction. To the downstream-flowing combustion gases which have been passed through a constricted or tapered portion of the apparatus there is then fed a hydro-carbon feedstock i the form of -a vapor at a rate of 16.97 gallons per hour. The feedstock employed herein is Sunray DX as described hereinbefore. In this run, the reaction conditions are maintained in a manner such as to provide an overall combustion of 28.9 percent. At the conclusion of the. eaction there is produced a novel carbon black exhibiting unusual activity which is characterized by possessing a carbon monoxide content of 0.75 niillimoles/gm, a hydrogen content of 2.27 millimoles/ gm, a BET total surface area of 119 m2/gm, a "t curve" surface area of 119 m2/gm, a ratio of "t curve" area to BET area of 1.0, an activity factor represen iiig. the product of hydrogen content and non-porous surface area of 270, an activity factor representing area of 120.?., and. a DBP value of 169. Additional physical properties att ibutable to this carbon black product include a Nigrometer .scale value of 80, a tinting strength of 214 and an extract value of 0.4 percent by weight which is the amount of matter removed from the carbon black by refluxing a sample of the black in ten times its weight of benzene for a 12 to 22 hour period.

Exam le 3 Following the procedure of Example 1 there are charged to a combustion zone a stream of oxygen at a rate of 2000 SCFH and a stream of natural gas at a rate of 625 of the combustion reaction, there is then fed as the hydrocarbon feedstock Sunray DX at a rate of 15.8 gallons per hour and the reaction conditions are maintained so as to produce an overall combustion of 30.3 percent. The resultant reaction product comprises an active carbon black having a carbon monoxide content of 0.45 millimoles/gm, a hydrogen content of 1.72 m llimoles/gm, a BET total surface area of 147 m2/gm, a "t curve" area of 147 m?'/gm, a ratio of "t" area to BET area o 1.0, an activity factor representing the product of hydrogen content and non-porous surface area of 253, an activity factor of 98.5 representing the product of carbon monoxide content and non-porous surface area and a DBP value of 163. The product o , a n ng s reng o an an ex rac va ue o . percent.

Example 4 In accordance with the procedure of Example 1, oxygen at a rate of 2000 SCFH and natural gas at a rate of 625 SCFH are fed into the combustion zone of the reaction apparatus. To the resultant downstream flow of hot combustion gases there is charged Sunray DX hydrocarbon feedstock ■ a -a rate of 16.9 gallons per hour. Prior to adding the feedstock, potassium chloride is added to the stream of hot combustion gases in small amounts. The reaction is carried out at an overall combustion of 28.9 percent. .There is obtained a car-bon black product having a carbon monoxide content of 0.51 -millimoles/gm, a'hydrogen content of 1.74 millimoles /gm, a BET total surface area of 122 m2 /gm, a "t curve" surface area of 122 mz/gm, a ratio of "t" area to' BET area of 1.0, an activity factor of 62.2 representing the product of carbon monoxide content and non-porous surface area, an activity factor representing the product of hydrogen content and non-porous surface area of 212, and a DBP value of 129. In addition, the carbon black product possesses a Nigrometer scale reading of 80.5, a tinting strength of 242, and an extract value of 0.29 percent.

Following the procedure . of Example 1, there are introduced into the combustion zone of the apparatus oxygen at a rate of 2000 SCFH and natural gas at a rate of 625 SCFH in order to produce the desired flame. Into the flow of hot combustio gases emanating from the combustion zone, there is then charged, as the hydrocarbon feedstock, Sunray DX at a rate of 16.74 gallons per hour. Following the' reaction period which is sufficient to provide an overall combustion of 29.2 percent, quenching of the reaction is completed and the carbon black product is cooled, separated and recovered. The resultant novel active carbon black product produced hereby is characterized by having a carbon monoxide content of 0.65 milli- moles/gm, a hydrogen content of 1.64 millimoles/gm, a BET total "surface area of 125 mz/gm, a "t curve" . area of 125 m2/gm, a ratio of "t" area to BET total area of 1.0, an activity factor of 81.3 representing the product of carbon monoxide content and non-porous surface area, an activity factor representing the product of hydrogen content and non-porous surface area of 205", and a DBF value of 139. It has furthermore been determined that the carbon black product possesses a Nigrometer scale value of 82 , a tinting strength of 255, and an extract value of 0.32 percent.

Exampl-e >' To a suitable reaction apparatus as described in 2000 'SCFH and a stream of natural gas at a rate of 625 SCFH. * _^ Having produced the desired flame, the hot combustion gases produced therein are passed in a downstream direction through a portion, of the apparatus which is restricted or tapered by means of a conventional venturi throat so as to accelerate the linear velocity of the stream of combustion gases. Subsequently, there is charged into the fast-flowing stream of combustion gases a stream of Sunray DX hydrocarbon feedstock at a rate of 1 6.4 gallons per hour. As an. additive potassium chloride is added in small quantities and the reaction conditions are maintained so as to result in an. overall combustion of 30 percent. Thereafter, the carbon black producing reaction is quenched with a spray of water and the carbon black is separated and recovered in conventional fashion. The active carbon black product thus obtained is characterized by having a carbon monoxide content of 0.69 millimoles/gm, a hydrogen content of 1.43 millimoles/ gm, a BET total surface area of 143 mz /gm, a "t curve" area of 138 m2/gm, a ratio of "t" area to BET total area of 0.97, an activity factor of 98.7 representing the product of carbon monoxide content and non-porous surface area, an activity factor of 197 representing the product of hydrogen content and non-porous surface area,. nd a DBP value of 163. The car-bon black product is further defined by having a Nigrometer scale reading of 80.5, a tinting strength of 257 and an extract value of 0.12 percent. prepared by conventional mechanical methods. For example, the "~ rubber and the active carbon black reinforcing agent are intim¬ ately admixed together on. a conventional mixing machine of the type normally used for mixing rubber or plastics such as a roll mill or a Banbury mixer in order to insure efficient dispersion.

The rubber compositions are compounded according to standard industry formulations for both natural rubber and synthetic rubber-co tai ing formulations. The resulting vulcanizates to be tested are cured at 293°F for 30 minutes when natural rubber is used and for 50 minutes when a synthetic rubber, styrene- butadiene rubber in this, instance, is employed. In evaluating Cf the performance of the novel active carbon, blacks of the present invention, the following formulations are utilized wherein the quantities are specified in parts by weight.

Natural Rubber Synthetic Rubber Synthetic Rubber Ingredient Recipe Recipe No. 1 Reci e No. 2 Polymer 100 (Natural 100 (styrene- 89.38 (styrene- Rubber) butadiene) butadiene) (cis-4 poly- butadiene) Zinc Oxide 3 3 Sulfur 1.75 1.75 Stearic Acid 1.5 2 Flexamine 1 Softener Mix 8 Santocure (CBS) 1.25 1.4 Alt x (MBTS) Sundex 7 0 25.62 n.gre en .^S-Jle . e p . e o.

Wings ay 100 - - 2 * Sunproof Improved - - 2.5 Carbon Black 50 50 75 With regard to the foregoing formulations, the Softener Mix comprises equal portions of naphtbenic oil sold under the trade designation Circosol 42XH by Sun Oil Company and a satur¬ ated polymeric petroleum hydrocarbon sold under the trade name Pa ap lex by C. P. Hall Company. Al ax (MBTS) is the trade name of R. T. Vanderbilt Company for mercaptobenzothiazy 1 disulfide accelerator. Flexamine is the trade designation of an anti¬ oxidant sold by U. S. Rubber Company:' Santocure (CBS) is the trade designation for N-cyclohexy 1-2 -benzothiazole-sulfenamide , a curing agent for rubber systems. Sundex 790 is the trade name for a lastieizer sold by Sun Oil Company. Sunproof Improved is the trade. ame for an antiozonant sold by Uniroyal Chemical Company. Wingstay 100 is the trade name for a stabilizer com¬ prising mixed diary l-p-phenylene- diamines sold by Goodyear Tire and Rubber Company.

In the following examples there is demonstrated the advantageous and unexpected results achieved by the use of the active carbon black products described, hereinabove as additives in rubber formulations. It will, of course, be apparent that the examples, v.'hile being illustrative of the present invention, should not be. construed as limiting or restrictive in any way.

On a conventional roll mill there are mixed to a homogeneous blend 100 parts by weight of natural rubber, 5 parts by weight of zinc oxide, 3 parts by weight of stearic acid, 2.5 parts by weight of sulfur,.0.6 parts by weight of mercaptobenzothiazy 1 disulfide (MBTS) and 50 parts by weight of the carbon black prepared in accordance with Example 1.

The resulting compound is subsequently cured at 293 °F for a period of 30 minutes. A determination of properties · of the vulcanizate gives a value of 72 for Mooney viscosity ML- ' at 212°F.,- a.Mooney Scorch value T5/T10 of 19.5/21, a tensile strength of 3600 psi, a 300%, modulus of 2130 psi, an elongation of 4607o, a Shore hardness of 67, a tear resistance of 406 l"bs. /inch of thi'c'knes-s and an Akron -angle abrasion volume index of 316. Utilizing a Goodrich Flexometer wherein the oven is maintained at a temperature of 212°F, the stroke is .175 inches, the load is 143 psi, and the period of time is 20 minutes, there are obtained a static compression value of 10.7%, a dynamic compression value of 13.1% and a permanent set value of 16.8 percent.

Example 8 One hundred parts by weight of a copolymer of 23.5 parts styrene and 76.5 parts butadiene, 1.5 parts by weight of stearic acid, 3 parts by weight of zinc oxide, 8 parts by welg' of softener mix, 1.75 parts by weight of sulfur, 1.0 parts by an -50 parts y we g t o t e car on ac pro uct escr e V* in Example 1 are mixed on a mill roll to a homogeneous blend.

The carbon black utilized has an activity factor representing the numerical product of carbon monoxide content-.and surface area of 237, an activity factor representing the numerical product of hydrogen content and surface area of 411, a ratio of "t" curve surface area to BET surface area of 1.0 and a DBP absorption value of 151. The resulting compound is then cured at 293 °F for a period of 50 minutes. Testing of the blend for conventional rubber properties reveals a value for Mooney vis¬ cosity ML-4' at 212°F of 92, a Mooney Scorch T5/T10 of 24.5/ 26.5, an extrusion shrinkage of 44.67» at 122°F, a tensile σ Cil fcijg u i i O x! J J i U p S , H 'uU/o tl'iOU J.Ua O J. I ? ¾ « p i JL , ait <e J. v liga tion of 470%, a Shore. hardness of 68, a bound rubber value of 31.77., and a tear resistance of 312 lbs. /inch of thickness.

Furthermore, using the Goodrich Flexometer of Example 7, it is determined that the static compression is 11.1%, the dynamic compression is 10.87., and the permanent set is 17.1 percent.

Example 9 In this example there is utilized for rubber evaluation purposes a second synthetic rubber recipe. In particular, there are mixed on a Banbury mixer at 150 rpm to a homogeneous blend 89.38 parts by weight of a copolymer of 23.5 parts styrene butadiene rubber, 25.62 parts by weight of Sundex 790 plasti- . cizer, 3 parts by weight of zinc oxide, 2.5 parts by weight of Sunproof Improved antiozonant , 2 parts by weight of Wingstay 100 stabilizer, 2 parts by weight of stearic acid, 1.75 parts by weight of sulfur, 1.4 parts by weight of Santocure and 75 parts by weight of the carbon black of Example 4. The carbon black of Example 4 is characterized by having an activity factor representing the numerical product of carbon monoxide content •and., surface area of 62.2, an activity factor representing the numerical product of hydrogen content and surface area of 212, a ratio of "t" area to BET area of 1.0 and a DBP absorption value of 129. A determination of" test measurements on the vul- .canizate cured at 293 °F for 60 minutes reveals a Mooney viscosity -.of 47, a Mooney Scorch- T5/T10 of 20.5/22.5 , an extrusion shrinkage of 39.9%, a tensile strength of 2790 psi, a 300% modulus of 1090 psi, an elongation of 570%, a Shore hardness of 58 and, utilizing the Goodrich Flexometer, a static compression of .6%, a dynamic compression of 5.5% and a permanent set of 10.7 percent.

Example 10 Following the procedure of Example 9 and using for the carbon black employed therein a carbon black as prepared in Example 5 which has an activity factor of 81.3 representing the numerical product of carbon monoxide content and surface hydrogen content and surface area of 205, a ratio of "t" area to ΒΕΪ area of 1.0 and a DBP absorption value of 139, there is obtained a cured rubber vulcanizate. The results obtained o this vulcanizate show a Mooney viscosity of 49, a Mooney Scorch T5/T10 of 19/21, an extrusion shrinkage of 35.4%, a tensile strength of 2840 psi, a 3007, modulus of 1260 psi, an elongation of 5.307>, a Shore hardness of 59, and, in accordance with measurements on the Goodrich Flexometer, a static compression of 23..5%, a dynamic compression of 6.27. and a permanent set of 12 percent.

Exam le 11 · . ' . ' A cured rubber vulcanizate is produced according to Example 9 with the exception that, for the carbon black utilized therein, 75; parts by weight of carbon black manufactured as described in Example 6 is employed herein. The carbon black of Example 6 possesses an activity factor of 98.7 representing the numerical product of carbon, monoxide' content and surface area, an activity factor of 197 representing the numerical product of hydrogen .content and surface area, a ratio of "t" area to BET area of 0.97 and a DBP absorption value of 163.

Measurements on this vulcanizate reveal a Mooney viscosity of 48, a Mooney Scorch 1 /Tl 0 of 19/21, an extrusion shrinkage of 40.77o, a tensile strength of 2910 psi, a 300% modulus of 1060 psi, an elongation of 5807>, a Shore hardness of 59 and, util-izing the Goodrich Flexometer, a static compression of 24. l70, cent.: · It will become readily apparent from the foregoing results that the novel group of active carbon black products disclosed herein, impart to natural and synthetic rubber compositions extremely desirable properties and therefore constitute a valuable group of effective reinforcing carbon blacks for rubber systems. For example, it will be noted that the present novel and important class of active carbon blacks are effective in imparting to rubber compositions properties such as abrasion resistance, modulus, extrusion shrinkage and/or activity. Additionally, it is found that while these properties are achieved, other desirable processing characteristics o tine compositions or the present invention are not unduly affected by the incorporation of the active carbon blacks in the compositions of this invention.

Numerous chemical curing systems have been found use-ful in promoting the interaction of the active carbon black reinforcement and the natural or synthetic rubber in practicing the present invention. Exemplary of the chemical curing agents are ercaptobenzothiazy 1 disulfide (MBTS) , N-cyclobexy 1-2-ben othiazole-sulfenamide and tetramethy lthiuramdisulfide (TMTD). Furthermore, for many purposes, it: may be desirable to compound the rubber compositions of the present invention with other conventional rubber additives. Illustrative of such s cpn ox e, z nc ox e, ca c um car ona e, c ays, ca c um silicate, zinc sulfide, hydrous alumina and calcined magnesia; thermoplastic resins such as polyvinyl chloride and epoxy resins as compounding substances ; vulcanizing agents; vulcanization accelerators; accelerator activators, sulfur curatives; anti¬ oxidants; decelerators ; heat stabilizers; plas ticizers , softeners or extender oils such as mineral oil, resins, fats, waxes, petroleum distillates, vegetable oils, e.g. , linseed ■ oil and soybean oil, butyl cellosolve pelargonate, di-n-hexyl adipate, trioctyl phosphate, chlorinated hydrocarbons, ether, ketones, terpenes, gum turpentine, rosin, pine tar, coal tar products including alkyl naphthalenes and polynuclear aromatics be apparent that compositions containing such other additives are within the scope of this invention. Moreover, it is further apparent from the foregoing data that the use in rubber of the present carbon 'black products having very high activity factors, virtual non-porosity and DBP absorption values greater than 110, result in reinforced rubber compositions having extremely desir¬ able physical properties.

While this invention has been described with respect to certain embodiments, it is not so limited, and it should be understood that variations and modifications thereof may be made which are obvious to those skilled in the art without departing v ' from the spirit or scope of the invention.

Claims (10)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows :

1. A carbon black product characterized by having an activity factor representing the numerical product of carbon monoxide content of the carbon black expressed in millimoles per gram and the non-porous surface area thereof which is at least 62, an activity factor representing the numerical product of hydrogen content of the carbon black and the non-porous surface area thereof which is greater than 175, a value for the ratio of non-porous surface area of the carbon black to total surface area thereof which is at least 0.8 and a DBP absorption value of at least 110 milliliters of dibutyl phthalate absorbed per 100 grams of pelleted carbon . black. ·

2. A carbon black product as defined in Claim 1. wherein the activity factor representing the numerical product of carbon monoxide content and. non-porous surface area ranges from 62 to about 125.

3. A carbon black product as defined in Claim 1 wherein the activrty—factor representing the numerical product of hydrogen content and non-porous surface area is greater than ',185. ' .

4. . A carbon black product as defined in Claim 1 ^ wherein the ratio of non-porous surface area of the carbon black to total surface area of the carbon black is greater than 0.9.

5. A composition of matter comprising a rubber selected" from the group consisting of natural and synthetic rubbers and a carbon black product selected from the group consisting of carbon blacks characterized by having an activity factor, which is the numerical product of the non-porous surface area in square meters per gram of the carbon black and the carbon monoxide content in millimoles per gram of the carbon black of at- least 62, an activity factor representing the numerical product of hydrogen content of the carbon black expressed in millimoles per gram and the non-porous surface area in square meters per gram of the carbon black which is ·.. greater than 175, a value for the ratio of non-porous specific surface area of the carbon black to total specific surface area of the carbon black which, is at least 0.8 and a DBF absorption value of at least 110 milliliters of dibutyl phthalate absorbed per 100 grams of pelleted carbon black, wherein the carbon black product is present in amounts of from about 10 to about 250 parts by weight of rubber.

6.' A composition as defined in Claim 5 wherein the rubber is natural rubber.

7. A composition as defined in Claim 5 wherein the^ rubber is synthetic rubber.

8. A process for preparing a rubber composition having improved properties which comprises mixing a rubber selected from the group consisting of natural and synthetic rubbers with a carbon black product selected from the group consisting of carbon blacks characterized by having an activity factor, which is the numerical product of the non-porous surface, area in square meters per gram of the carbon black and the carbon monoxide content in millimoles per gram of the carbon black of at least 62, an activity factor representing the numerical product of the non-pbrous surface area in square meters per gram of the carbon black and the hydrogen content in millimoles per gram of the carbon black which is greater than 175, a value for the ratio of non-porous specific surface area of the carbon black to' total specific surface area of the carbon black which is at least 0..8 and a DBP absorption value of at least 110 milliliters of dibutyl phth'alate absorbed per 100 grams of pelleted carbon black, said carbon black product being present in amounts of from about 10 to about 250 parts by weight per 100 parts by weight of rubber, and vulcanizing the mixture. · * ' ■Ί ■'' ■ ' '■ ' ' ■

9. A process' as defined in Claim 8 wherein the carbon black product is present in amounts of from about 20 to about about 100 parts by weight per 100 parts by weight of rubber.

10. A process as defined in Claim 9 wherein the carbon black product is present in amounts of from about 40 to about 80 parts by weight per 1.00 parts by weight of rubber Tel-Aviv, June 6, 1971 AGENT FOR APPLICANTS