EP0110953A1

EP0110953A1 - Uncured rubber compositions containing aromatic furazan oxides

Info

Publication number: EP0110953A1
Application number: EP83902018A
Authority: EP
Inventors: Walter R. Hausch; Daniel F. Graves
Original assignee: Firestone Tire and Rubber Co
Current assignee: Bridgestone Firestone Inc
Priority date: 1982-05-20
Filing date: 1983-05-09
Publication date: 1984-06-20
Also published as: WO1983004031A1; EP0110953A4; CA1229940A; ES8505699A1; AU1702983A; PH22898A; IT1162863B; NO831760L; PT76728A; NO163622B; KR920001045B1; NO163622C; IT8367550A0; ES522553A0; AU568502B2; KR840004920A; PT76728B

Abstract

Des compositions de caoutchouc non-polymérisées contenant des oxydes de furazane aromatiques fusionnés présentent une aptitude améliorée au traitement et une viscosité réduite. Des oxydes de furazane utiles ont les deux carbones de l'anneau furazane comme faisant partie d'un anneau aromatique fusionné et comprennent l'oxyde de benzofurazane et ses analogues de méthyle et de méthoxy. Des améliorations à l'aptitude au traitement, à la résistance au vert et à la liquéfaction de NR peuvent être obtenues en utilisant ces oxydes de furazane dans des compositions de caoutchouc non-polymérisées. Des produits de vulcanisation de caoutchouc plein contenant des oxydes de furazane aromatiques présentent de nombreuses propriétés améliorées telles qu'une interaction accrue entre le matériau de remplissage et le caoutchouc et une hystérèse réduite. Des oxydes de furazane utiles ont les deux carbones de l'anneau de furazane comme partie d'un anneau aromatique fusionné. Des exemples caractéristiques sont l'oxyde de benzofurazane et ses analogues de méthyle et de méthoxy. Des pneumatiques fabriqués à partir des produits de vulcanisation de l'invention ont des températures de roulement plus faibles et une résistance au roulis améliorée.Unpolymerized rubber compositions containing fused aromatic furazan oxides have improved processability and reduced viscosity. Useful furazane oxides have the two carbons of the furazane ring as part of a fused aromatic ring and include benzofurazane oxide and its methyl and methoxy analogs. Improvements in the processability, green strength and liquefaction of NR can be achieved by using these furazan oxides in unpolymerized rubber compositions. Solid rubber vulcanizers containing aromatic furazan oxides have many improved properties such as increased interaction between the filler and rubber and reduced hysteresis. Useful furazan oxides have the two carbons of the furazan ring as part of a fused aromatic ring. Typical examples are benzofurazane oxide and its methyl and methoxy analogs. Tires made from the vulcanization products of the invention have lower rolling temperatures and improved rolling resistance.

Description

UNCURED RUBBER COMPOSITIONS CONTAINING AROMATIC FURAZAN OXIDES

This invention relates to uncured rubber compositions and filled vulcanizates made therefrom. More particularly, it relates to such compositions exhibiting improved properties and containing aromatic furazan oxides. It also relates to methods of improving the processability, green strength and viscosity properties of uncured rubber compositions and articles made from the vulcanizates, such as tires, and methods of improving the rolling resistance and running temperatures of such tires.

BACKGROUND OF THE INVENTION.

It is well-known that, with very few exceptions, rubber compositions are combined with various other materials before being cured and/or put into use. Some of these added materials improve the properties of the end product in service while others improve processing proper¬ ties of the uncured compositions. In some instances, both effects may be achieved. It is also known that the various chemicals, pigments and other materials so used, both organic and inorganic, can interact in various ways to produce desirable or deleterious effects. For further discussions of rubber processing and materials used therein, see, for example, Encyclopedia of Polymer Science and Technology, published by John Wiley and Sons, New

York (1970), particularly volume 12, page 280 and The Vanderbilt Rubber Handbook, R. T. Vanderbilt Company, Norwalk, Connecticut, 06855 (1968), particularly Sections 6, 7, 8, 9 and 11. Benzofurazan oxides, and their analogs and isomers are known compounds, and many descriptions of them and procedures for their preparation have appeared. See, for example, Kaufman, et al., "Chemical Reviews," volume 9, page 429 and following (1959) and Mallory,. et al., "Organic Synthesis" collective volume IV^*, pages 74 and 75, John Wiley and Sons, New York (1963). The following U.S. Patents also describe procedures for preparing furazan oxides of various types: U.S. Patent 4,185,018 to Fah; U.S. Patent 3,528,098 to Shaw; and U.S. Patent 2,424,199 to Ter Horst. In considering previous descriptions of furazan oxides and related compounds, it should be noted that nomenclature used for these compounds has not been consistant, in part due to uncertainty as to their structures and predominant isomeric form. For example, they have been described as furazan oxides, as ortho dinitroso benzenes or di (nitrile oxides) . At other points, they have been referred to as isobenzofuroxans, benzofuroxans, benzofurazan-N-oxides and benzofurazan oxides. It is believed that the latter term is the modern and preferred nomenclature, and it shall be used in this specification and the appended claims.

Studies of furazan oxides and related compounds in rubber have been reported. For example, Rehner and Flory state in Industrial and Engineering Chemistry, volume 38, page 500 et sec, that ortho dinitroso benzene is inactive in butyl rubber as a vulcanizing agent. In contrast, the para isomer is said to be very active by Rehner and Flory. U.S. Patent 3,931,121 to Davis, et al. , describes the curing of elastomeric polymers with poly (chloronitroso) compounds. U.S. Patent 3,931,106 to Crosby, et al., describes the use of dinitrile oxides, which can be generated in situ from furazans, in rubber cross-linking. In this regard, it should be noted that the aromatic furazan oxides of this invention cannot isomerize to di (nitrile oxides) because the bond between the adjacent carbon atoms is part of an aromatic ring. U.S. Patent 2,974,120 to Miller describes the use of nonaromatic furoxans as antioxidants and antidegradants in rubber. U.S. Patent 2,905,582 to Coleman, et al. , describes the use of nitroso compounds, including dinitroso compounds wherein the nitroso groups are on nonadjacent carbons in a method for bonding polyurethane resin to rubber bodies. Morita has described the use of N, 4-dinitroso-N-methyl aniline as an active chemical promoter for carbon black reinforcement of IIR, NR and SBR. See Rubber Chemistry and Technology, volume 49, page 119 and following (1976). Tanaka, et al. , have reported studies of nitroso benzene in rubber where chain cleavage S-zas observed in Kogyo Kagaku Zasshi .74(8), pages 1701-6 (1971).

SUMMARY OF THE INVENTION.

According to one aspect of this invention, uncured rubber compositions comprising at least one rubber having an unsaturated carbon chain and minor, property-improving, amounts of at least one aromatic furazan oxide of a partial formula

wherein the depicted carbon atoms are part of a fused aromatic ring, are improved in processability and/or green strength. Such compositions may also exhibit desirably

SUBSTITUTE SHEET reduced viscosity and other beneficial properties. The invention includes methods of improving processability, enhancing green strength and reducing viscosity of uncured compositions by adding aromatic furazan oxides to them. Liquid rubber compositions are also within the scope of the invention.

In another aspect of the invention, a filled vulcanizate made by vulcanizing a composition comprising at least one rubber having an unsaturated carbon chain, filler and a minor, cured property-improving amount of at least one aromatic furazan oxide of the partial formula

wherein the depicted carbon atoms are part of, a second, single aromatic ring, is improved in filler interaction, hysteresis, modulus, compression set and resiliency. Rubber articles and portions thereof made from such vulcanizates such as tires, hoses, belts, treads, sidewalls and the like are also within the scope of the invention as are methods for reducing the rolling resistance and running temperatures of such tires.

DETAILED DESCRIPTION OF THE INVENTION The rubber compositions of the first aspect of this invention are not cured, that is, they are uncured and not vulcanized. In some instances, they contain curing agents (systems) and thus are capable of being cured. In other words, they are vulcanizable. In other instances, the compositions of this invention do not contain curing agents, either because they are

SUBSTITUTE SHEET OMPI intermediate compositions to which a curing system will be, but not yet have been, added or because they are to be put in use without the addition of curing agents in such applications as sealants, caulks, adhesives and the like. In any event, the invention includes uncured rubber compositions containing aromatic furazan oxides whether or not they contain, in addition, curing agents, and whether or not they are intermediates to which curing agents are to be added. Said curing agents, when present, are of the conventional type such as sulfur-or peroxide-based curing systems and the like. They are used in conventional amounts and incorporated in the uncured compositions of this invention by known techniques and procedures. Fillers (pigments) may be, and often are present as is known to those skilled in the art. Typical fillers include carbon black in its various forms, glass, silica, talc and similar finely divided mineral materials.

The rubbers used in the uncured compositions of this invention have unsaturated carbon chains. That is, their polymer backbones contain a significant amount of unsaturation, in contrast to the pendent or vinyl saturation as found in some other types of rubbers. Typically, the chains of such unsaturated rubbers have at least about 20% of their carbon to carbon bonds as unsaturated bonds. Characterization of rubber as having unsaturated carbon chains it well-known in the art as shown by ANSI/ASTM Standard D 1418-79A where unsaturated-chain rubbers are referred to as R rubbers. Class R rubbers include natural rubber and various synthetic rubbers derived at least partly from diolefins.

SUBSTITUTE SHEET

OMPI__ The following is a non-exclusive list of R class rubbers which can be used in the compositions of the present invention:

ABR--Acry1ate-butadiene BIIR--Bromo-isobutene-isoprene

BR--Butadiene

CIIR—Chloro-isobutene-isoprene CR—Chloroprene IIR--1sobutene-isoprene IR—Isoprene, synthetic

NBR-_^-Nitrile-butadiene NCR—Nitrile-chloroprene NIR—Nitrile-isoprene NR--Natural rubber PBR—Pyridine-butadiene

PSB —Pyridine-styrene-butadiene SBR--Styrene-butadiene SCR--Styrene-chloroprene SIR--Styrene-isoprene rubbers. Of these, compositions where the rubber is NR, IR, BR,

SBR, CR, CIIR, NIR or mixtures of two or more of these are typically used. Many compositions are made wherein the rubber is NR, SBR or a mixture containing at least about 50 percent of one of these. Compositions containing only NR as the rubber portion are often used. In the con-text of this invention, NR includes both heava and guayule rubber as well as mixtures thereof.

The compositions of the present aspect of this invention can also contain materials used in conventional rubber formulations such as antioxidants, accelerators, retarders, promoters and the like in addition to the curing systems and fillers noted above. It should be noted, however, that it is sometimes desirable to choose such materials with care since they may interact with the essential furazan oxides.

SUBSTITUTE SHEET OMPI The rubbers of another aspect of this invention, that relating to vulcanizates (i.e., cured stocks) are essentially the same as those described above.

The vulcanizates of the present invention also contain fillers of the conventional type such as carbon black in its many forms, clays, talc, pyrophyllite, silica and other inorganic, finely divided materials. In addition, they contain conventional curing systems and agents, such as sulfur, antioxidants, accelerators, retarders, coupling agents, promoters and the like. It should be noted, however, that it. is sometimes desirable to take care in choosing such materials since they may interact with the furazan oxides.

The furazan oxides used in both the vulcanizable and vulcanized (cured) compositions of this invention are fused aromatic, that is, they have an aromatic ring fused to the N-oxidized heterocyclic furazan ring. They are of the partial formula

wherein the depicted carbon atoms are part of a fused, single aromatic ring. This aromatic ring can be carbocyclic such as a benzene ring or it may be heterocyclic, such as a pyridine ring. It can be the only additional ring in the furazan compound, or it can be part of a linked or fused ring system. It is only necessary that both depicted carbon atoms be part of the same aromatic ring.

SUBSTITUTE SHEET Examples of the furazan oxides useful in the vulcanizable and cured compositions of this invention are those that can be represented by the formulae

wherein none, one or any two of the ring positions can be substituted with lower hydrocarbyl, halogen, hydroxyl, lower hydrocarbyl oxy, lower hydrocarbyl thio, lower hydrocarbyl carbonyl, carbonyl lower hydrocarbyl oxy, nitro, amino or amine groups and Y is a linking atom or group. In this context, lower hydrocarbyl refers to groups of carbon and hydrogen having eight or less carbon atoms such as methyl, ethyl, butyl, pentyl, heptyl, octyl (all isomers) . Linking atoms or groups include ether, thio ether, sulfoxide, sulfone, amine, methylene and the like (including simple covalent bonds such as found in biphenyl) and the other linking groups shown in U.S.

ξV -lEA

SUBSTITUTE SHEET OMPI Patent 3,528,098 (which is incorporated by reference herein for its disclosures in this regard). Hydrocarbyl- oxa, hydrocarbyl this and mixed hydrocarbyl oxa-thia substitutents are also possible where the hydrocarbyl groups are typically lower alkylene moieties. Such are often made from glycols, dithiols, epoxides and episulfides. Often the furazan oxide is a benzofurazan oxide of the formula

wherein none, one or any two of ring positions can be substituted with lower hydrocarbyl, halogen, low hydrocarbyl oxy, lower hydrocarbyl thio, lower hydrocarbyl carbonyl, carbonyl lower hydrocarbyl oxy, nitro, amine or amino groups. Typically, the furazan oxide is benzofurazan oxide or the methyl or methoxy analog thereof. Methods for preparing, purifying and handling these compounds are known to the art as is shown by the references cited hereinabove. It should be noted that some of these furazan oxides, particulary those containing relatively large amounts of nitrogen and oxygen, such as benzotri (furazan oxide) and 4, 6-di (nitro) benzofurazan oxide, are prone to rapid decomposition to the point of explosions; all may be physiologically active to varying degrees. Therefore, care in their handling and use should be exercised.

OMPI

SUBSTITUTE SHEET ,.~Y?IPO- The vulcanizable compositions of the present invention can be prepared by conventional techniques using various types of mills, blenders and mixers known to the art. The cured compositions can be made by the same techniques followed by curing. Usually the amount of furazan oxide used is a property-improving amount, such as an amount which will improve the processability of the composition and, in certain instances, its green strength and viscosity properties. Processability properties are those related to the ease and efficiency of mixing, mastication and handling of a rubber composition in its unvulcanized, that is, uncured state. They include viscosity and often the speed and efficiency with which various other components are dispersed in the rubber. Similar amounts are used in the cured compositions to improve such vulcanizate properties as filler interaction, modulus, resiliency, hysteresis, rolling resistance, running temperature and the like. Typically, this property-improving amount will range from about 0.1 to 10 parts per 100 parts (by weight) rubber (phr) . Often the furazan oxide will be used in an amount ranging from 0.5-5 phr. The temperatures used in formulating the rubber compositions of this invention range from ambient to those normally used in the art, such as 75 degrees to 175 degrees or ambient, say 20°, to those conventionally used such as 150° to 200°. In its broader aspects, the formulations can be made from about 20 degrees to 220 degrees. Although in many instances, narrower temperature ranges such as about 50 degrees to 190 degrees are employed. As noted hereinabove fillers, promoters, curing agents and other conventional rubber additives are also often included in these precured mixtures in conventional amounts.

SUBSTITUTE The vulcanizates of this invention are prepared by curing the furazan oxide containing compositions under conditions of temperature and time customarily used in the art, and the invention is not significantly dependent on such curing variables. Typically the rubber and filler (or pigment) are first mixed and then the mixture treated with furazan oxide before curing. Other sequences can also be used but it is essential to have the rubber, filler (pigment) and furazan oxide intimately combined before vulcanization.

Among the desirable and beneficial properties exhibited by the compositions of the present invention are improved processability, enhanced green strength and in some instances reduced viscosity. Compositions containing substantial amounts (greater than 50 percent) of NR, IR or CR show improved processability and enhanced green strength. Improved processability of uncured rubber formulations is often desirable because it permits savings in energy and time while compounding and subsequent processing of the rubber by techniques such as calendering, milling, remilling, extrusion and the like. Such savings are important in the current period of shortages and rising costs. In general processability is an inclusive term used also to describe the decreased viscosity and/or high green strength such as found in the compositions of this invention. Heretofore, it has often been found that decreasing viscosity of an uncured composition also results in decreased green strength. Similarly, increasing green strength has been found to increase viscosity. It is a particularly desirable feature of the compositions of the present invention that viscosity reductions are achieved in combination with green strength increases.

SUBSTITUTE SHEET >

- 12

In general, NR, IR and CR containing compositions show viscosity reductions of about 20 Mooney units for about 0.5-1.5 phr furazan oxide with accompanying increases in green strength of about 20-100 psi. Similar levels of furazan oxide in synthetic rubbers such as, for example, SBR show Mooney viscosity increases of about 10 units while when peak green strength is increased about 5-50 psi. With higher levels of furazan oxides (e.g. 2-5 phr), the extreme in viscosity reduction can be reached with liquefaction of NR and IR. Such liquid rubbers are useful in sealants and as processing aids where they are combined with other types of rubber to aid in plasticizing rubber. Liquid rubbers, also known as depolymerized rubber (DPR) , are well-known in the art and need not be further described here. It is sometimes found that the viscosity reductions observed in the compositions of the present invention are accentuated by the inclusion of antioxidants and materials such as carbon black and silica which are believed to interact and trap polymer free radials prior to their cross-linking. Thus maximum viscosity reductions can usually be achieved by adjusting the concentrations of the furazan oxide and the antioxidant or radial trapping materials (fillers) in a given rubber composition.

EXAMPLES

The following, nonlimiting examples exemplify the practice of the invention and include the best mode presently known. In these examples, as elsewhere in the specification and claims, all parts and percentages are by weight (pbw), unless specified otherwise, and temperatures are in degrees centigrade. Conventional rubber compounding materials, conditions, temperatures, procedures and evaluation techniques are used unless noted to the contrary.

OMPI ~ ~ MASTERBATCH PREPARATION

In the following examples, an internal mixer, such as a Brabender or small size Banbury mixer, was used. The usual technique was to add various materials, often in portions, to the mixer and continue mixing for the indicated time period. Further additions followed by mixing are then made to the masterbatches thus prepared. The standard technique was according to the following schedule:

TIME, (Min) ADD TO MIXER

0 Polymer, 100 parts

.5 half charge filler plus furazan oxide

1.5 Balance filler plus zinc oxide, stearic acid

3.0 Processing oil 6.0 Drop mixed composition at 160-170°F

The uncured masterbatch was then immediately banded and sheeted on a small twin roll mill set at 60 gauge. Mooney viscosities were measured using the large rotor in a four minute cycle at 100 degrees. This procedure was used to make masterbatches from NR (Hevea) and SBR (trade name Duradene, available from The Firestone Tire & Rubber Company, Akron, Ohio, USA) .

EXAMPLE ONE

A series of typical tire belt skim formulations were prepared using 100 percent natural rubber containing zinc oxide (5 phr), stearic acid (2 phr), carbon black (40 ^• parts) and varying amounts and types of furazan oxides. Each was mixed 5 minutes and dropped at 143°. The additives used and results were as follows

UBSTITUTE SHEET . _,o OMPI

. Y.^*IPO < Additive Mooney Green Strength, psi

Stock Type Amount Vis init(f) peak(d) Elong(

Control 41 25 135 810

IA BFO (a) 28 20 340 670

IB BF0^(b^ 24 25 300 650

Comparison

Pepton 44 (c) 26 25 80 735

a - benzofurazan oxide b - 6 - methyl benzofurazan oxide c - Pepton 44, a commercial peptizer sold by American Cyanamid Co. , d - break same as peak e - percent elongation f - at 50% elongation

As can be seen from the preceeding Table, stocks IA and IB, both of which contained furazan oxides, exhibited decreased Mooney viscosities and, at the same time, increased green strengths.

EXAMPLE TWO A SBR-based passenger tire tread stock composition was prepared containing about 60 phr carbon black and conventional amounts of zinc oxide, stearic oxide and a waxy antioxidant. A similar formulation containing in addition 1.0 phr benzofurazan oxide was prepared under comparable conditions. The Mooney viscosity

SUBSTITUTE SHEET OMPI of the control was 60.0 and of the furazan oxide containing composition, 68.9. The green stress-strain properties of the two compositions were as follows:

Control Control Plus BFO

Intial 33 50

Peak 43 84

Break 27 84 ation, % 545 570

EXAMPLE THREE A NR composition was prepared containing about 40 parts ISAF black, about 20 parts Hi-sil silica and conven¬ tional amounts of zinc oxide, antioxidants, softener, resin, sulfenamide accelerator, sulfur and retarder. An essentially identical composition was prepared containing, in addition, 1 phr benzofurazan oxide. The control had a Mooney viscosity of 64.4 and the furazan oxide formula¬ tion, a viscosity of 49.0. Thus, 1.0 part furazan oxide causes a 15 unit decrease in viscosity under identical mixing conditions.

EXAMPLE FOUR

Two typical truck tire tread compositions were prepared from grade B NR containing silica filler (about 80 phr Hi-sil silica) . Conventional amounts of silane coupling agent, plasticizer, antioxidant, processing oil, sulfur, accelerator, retarder, resin and activator were also included. The composition without furazan oxide was hard to mix in a 1.3 kg Banbury and when dropped was very dry, stiff and had the appearance of sawdust. A second

SUBSTITUTE SHEET " ^O P^ compound of the same formula containing, in addition, 1 phr benzofurazan oxide was ready to drop after only six minutes of mixing but was given the same 12 minute mix as the control. It dropped smoothly from the Banbury and was not stiff.

EXAMPLE FIVE(A)

A series of rubber compounds based on IR was prepared. The compounds were free of filler and curing agents; they contained varying amounts of methyl benzofurazan oxide, ranging from O to 2.5 phr and, in some instances, 2.0 phr commercial antioxidant (Santoflex 13). Each was mixed 6 minutes at 150°F and then the Mooney viscosity determined. The results are shown in Table 5A. As can be seen, with the compounds containing no anti- oxidant, viscosity increases up to 1.5 phr furazan oxide and tnen falls sharply. This increase is believed to be due to cross-linking reactions which compete with chain scission. At high levels of furazan oxide scission overtakes cross-linking and viscosity reduction results. Other observations revealed that in the presence of carbon black viscosity increases do not occur. Rather, only a steady decrease in viscosity with increasing furazan oxide is observed.

In the stocks containing both furazan oxide and antioxidant, a similar steady decrease in viscosity was observed. It is believed that the antioxidant impedes crosslinking and the decrease due to chain scission is evident.

SUBSTIT TABLE 5A

Additive, phr Mooney Vis. , 100°

MBFO SANTOFLEX 13^(a)

0 0 40

0.5 0 46

1.0 0 53

1.5 0 55

2.5 0 19

0 2.0 70

1.0 2.0 40

2.0 2.0 19

(a') - A commercial antioxidant available from the

Monsanto Chemical Co. of St. Louis, Missouri, USA.

EXAMPLE 5(B) A similar series of rubber compounds based on SBR was prepared containing methyl benzofurazan oxide and, in some instances, Santoflex 13. In the absence of the latter, a steady increase in viscosity is observed. When antioxidant is also present, a steady decrease in viscosity resulted as shown by the data in Table 5B.

TABLE 5B

Addit,ive, phr Mooney Vis. , 100°

MBFO SANTOFLEX 13

0 0 47

0.5 0 54

1.0 0 59

1.5 0 65

2.5 0 ^•67

0 2.0 45

1.0 2.0 30

2.0 2.0 23

SUBSTITUTE SHEET OMPI Master batches prepared according to the procedure described above were immediately banded and sheeted on a small twin roll mill for two minutes set at 60 gauge. Mooney viscosities were measured using the large rotor, and a four minute cycle at 212°F. Master batches prepared essentially according to this schedule were combined with conventional elastomer curing systems in typical amounts and cured for 15, 23 and 30 minutes at 300° F to provide test specimens. Typical conventional curing systems include sulfur-, peroxide-, urethane-, and benzoquinone dioxime systems.

EXAMPLE SIX

A series of vulcanizates was prepared using a conventional carbon black containing forumulation and sulfur based curing system. The vulcanizates also contained about 20 parts Hi-Sil silica and conventional amounts of zinc oxide, antioxidants, softener, resin, sulfenamide accelerator, sulfur and retarder. The first (the control) contained no promoter, the second 0.6 phr Nitrol (Monsanto Chem Co.) and the third 1.0 phr benzo¬ furazan oxide. Nitrol is a known promoter and was used at its recommended level. Evaluation data for each vulcani¬ zate are shown in Table I. Clearly the benzofurazanoxide- containing vulcanizate is superior in most properties and exhibits no significant deficiencies in any property.

EXAMPLE SEVEN

Typical truck tire tread vulcanizates were prepared from grade B natural rubber filled with silica (about 80 parts phr Hi-Sil) and containing conventional amounts of silane coupling agent, plasticizer, antioxi¬ dants, processing oil, sulfur, accelerator retarder, resin

SUBSTITUTE SHEET OMPI

Λ V/IPO

^' and activator. It was noted that the conventional composition was hard to mix in a 1.3 Kg Banbury and when dropped was very dry and stiff with the appearance of sawdust. The same mixture containing, in addition, 1 phr benzofurazan oxide was ready to drop after only six minutes but was given the same 12 minute mix as the control. It dropped smoothly from the Banbury and did not exhibit the stiffness and appearance of the control. The two compounds were cured in the same manner and evaluated in a number of standard tests. The results of these evaluations are shown in Table II. Clearly the vulcanizate containing 1 phr benzofurazan showed improved (that is, lower) running temperature and increased rebound. Other properties are not significantly diminished by the presence of the furazan oxide.

EXAMPLE EIGHT

A series of typical tread stocks was prepared from synthetic rubber according to a typical tread stock recipe calling for about 60 parts carbon black. The control contained no additive and Examples 3A and 3B contained one phr of methoxy benzofurazan oxide and benzo- furazan oxide, respectively. Each stock was cured in the usual manner and the vulcanizate specimens evaluated in a number of standard tests. As can be seen from the data in Table III, the stocks containing the benzofurazan oxides showed superior properties.

HEET TABLE I

Benzo¬

None furaz romoter/Feature (Control) Nitrol Oxid onsanto Rheometer 300°F S(2) 7.4 7.7 8. C(90) 21.3 21.3 19. in. Torque 9.8 10.8 7. orque at 90% Cure 38.0 38.1 37. ax. Torque 41.1 41.1 40. RI 7.2 7.4 9. hore "A" Hardness 3-°F 72 71 71 12°F 66 65 63 ing Tear at 212°F

558 552 433 ing Tensile at ambient temp. 00% Modulus 1914 1947 2410 ensile 2573 2479 2868 longation 391 368 352 ged Ring Tensile 2 days at 212°F 00% Modulus 1614 1628 1848 ensile 2211 2307 2542 longation 275 280 270 ebound 73°F 39.5 42.0 51. irestone Flexometer 5501bs, .4" throw Deflection 26 22.7 22. low-out, min. 9 9 13 irestone Flexometer 2501bs, .3" throw Deflection 8 8 10. unning Temp., °F 340 317 268

O

SUBSTITUTE SHEET Λ, I - -

TABLE III

Methox

None Benzofurazan Benzofuraza romoter/Feature (Control) Oxide Oxide onsanto Rheometer 300°F S (2 ) 14.3 16.3 16.4 C( 90 ) 23.3 22.3 23.2 in. Torque 11.3 12.0 9.6 orque at 90% Cure 39.5 39.3 38.4 ax. Torque 42.6 42.3 41.6 RI 11.1 16.7 14.7

hore "A" Hardness 3°F 60 57 58 12°F 58 56 56 ing Tear at 212°F

147 137 147 ing Tensile at ambient temp 00% Modulus (cured 30" 1594 2065 1806 ensile at 300°F) 2375 2154 2172 longation 399 311 345 ebound: 73°F 43 51.0 49.0 ebound: 212^c F 63 69 68 irestone Flexometer 2501bs, 3" throw Deflection 15.3 16 15.3 nning Temp., °F 254 235 245 sistivity, 30' at 300° F -11 . -0.4 -1.2 .B. Dispersion, % 93 91 95 rbon Bound Rubber, % 19.6 36.0 28.2 lling Resistance, % par -5 -5

OMPI UTE SHEET - 21 -

TABLE I I

1 Phr, BenzO'

Control Furazan Oxide

Shore "A" Hardness

73°F 68' 69

212°F 67 63

Ring Stress-Strain

23^! cure - 300% Mod. 1619 1178

Tensile 2546 2072

Elongation 449 463

MTS 7% Deflection, lOlbs, 10 HZ

K' 1400 1130

K" 302.8 247.5

Tan delta .216 .219

Monsanto Rheometer at 300°F

TS(2) 10.3 8.7

TC(90) 15.3 16.1

Min. Torque 15.5 12.8

Torque at 90% Cure 51.1 40.8

Max. Torque . 55.0 43.9

CRI 20.0 13.5

% Rebound

73°F 36 41

212°F 53 55

Ring Tear at 212°F

490 344

Firestone Flex - 2501bs, .3" throw

% Deflection 7.3 14.0

Running Temp. , °F 385 295

UTE SHEET OMPI TABLE III (Continued)

Methox

None Benzofurazan Benzofuraza romoter/Feature (Control) Oxide Oxide TS 7% Deflection, lOlbs, 10 FIZ ' (Ambient Temp. ) . 95, 900 930 " (Ambient Temp.) 197 144 156 an delta (Ambient Temp. ) .207 .160 16 ' delta (212°F) 800 750 770 " delta (212°F) 137 99 112 an delta (212°F) 171 131 .14

OMPI UTE SHEET While the invention has been described and exemplified herein by reference, specific materials, machinery, techniques, procedures and examples, it is understood that it is not restricted to any of these numerous variations, combinations, and permutations can be made within the scope of the invention as is clear to those skilled in the art.

_ _.._-_-- OMPI TE SHEET ^"W ^"

Claims

WHAT IS CLAIMED IS:

1. An uncured rubber composition comprising at least one rubber having an unsaturated carbon chain and a minor, property-improving amount of at least one aromatic furazan oxide of the partial formula

wherein the depicted carbon atoms are part of a single fused aromatic ring.

The composition of Claim 1 wherein the rubber is NR, IR, BR, SBR, CR, CIIR, NIR or mixtures of two or more of these.

The composition of Claim 2 wherein the rubber is NR, SBR or a mixture containing at least about 50 percent of one of these and a filler is present.

4. The composition of Claim 1, 2 or 3 wherein the furazan oxide is of the formula

TUTE SHEET

wherein none, one or any two of the ring positions can be substituted with lower hydrocarbyl, halogen, hydroxyl, lower hydrocarbyl oxy, lower hydrocarbyl thio, lower hydrocarbylthia-, -oxa, and -thia, -oxa, lower hydrocarbyl carbonyl carbonyl lower hydrocarbyl oxy, nitro, amine or amino groups and Y is a linking atom or group.

The composition of Claims 1, 2 or 3 wherein the furazan oxide of the formula

wherein none, one or any two of ring positions can be substituted with lower hydrocarbyl, halogen, hydroxyl lower hydrocarbyl oxy, lower hydrocarbyl thio, lower hydrocarbyl carbonyl, carbonyl lower hydrocarbyl oxy, nitro, amine or amino groups.

OMPI The composition of Claims 1, 2 or 3 wherein the furazan oxide is a benzofurazan oxide or the methyl or methoxy analog thereof.

A method of improving the processability and/or reducing viscosity of uncured rubber compositions containing at least one rubber having unsaturated carbon backbone chains which comprise including in the composition an effective amount of at least one aromatic furazan oxide of the partial formula

wherein the depicted carbon atoms are part of a single fused aromatic ring.

8. The method of Claim 7 wherein the furazan oxide is a benzofurazan oxide of the formula

wherein none, one or any two of the ring positions 4, 5, 6 or 7 can be substituted with with lower hydrocarbyl, hydroxyl halogen, lower hydrocarbyl oxy, lower hydrocarbyl thio, lower hydrocarbyl carbonyl, carbonyl lower hydrocarbyl oxy, nitro, amine or amino groups with balance

Tϋ EXζ/

OMPI substituted with hydrogen atoms and Y is a linking atom or group.

9. The method of Claim 7 or 8 wherein the rubber is NR, IR or CR and a filler and curing agent present.

10. The method of Claim 7 or 8 wherein the rubber is NR and a carbon black filler is present.

11. A method of liquifying NR- which comprises mixing therein a liquifying amount of at least one aromatic furazan oxide of the partial formula

wherein the depicted carbon atoms are part of a second single fused aromatic ring.

12. A method of enhancing the processability of NR, SBR, or IR, or mixtures containing at least one thereof, according to Claim 7.

13. A filled vulcanizate made by vulcanizing a composition comprising at least one rubber having an unsaturated carbon chain, filler and a minor, cured property- improving amount of at least one aromatic furazan oxide of the partial formula: - 29 -

wherein the depicted carbon atoms are part of a single aromatic ring.

14. The vulcanizate of Claim 13 wherein the rubber is NR, IR, BR, SBR, CR, CIIR, NIR or a mixture of two or more of these.

15. The vulcanizate of Claim 13 wherein the rubber is NR, SBR or a mixture containing at least about 50 percent NR, and the filler is carbon black, silica or a mixture of these.

6, The vulcanizate of Claims 13-15 wherein the furazan oxide is of the formula

wherein none, one or any two of positions 4, 5, 6 or 7 can be substituted with lower hydrocarbyl, halogen, lower hydrocarbyl oxy, lower hydrocarbyl thio, lower carbonyl, carbonyl hydrocarbyl oxy, nitro, amino or amine groups and Y is a linking atom or group.

OMPI 17. The vulcanizate of Claims 13-14 wherein the furazan oxide is benzofurazan oxide or a methyl or methoxy analog thereof.

18. A tire having at least a portion thereof made of the vulcanizate of Claims 13 or 14.

19. A tire having at least a portion thereof made of the vulcanizate of Claims 13 or 14, said vulcanizate comprising NR or a mixture containing at least 50 percent NR.

20. A method of reducing the rolling resistance of a tire which comprises making the tread portion of the tire from a vulcanizate of Claims 13 or 14.

21. A method of reducing the running temperature of a tire which comprises making at least a portion of the tire from a filled vulcanizate comprising at least one rubber having an unsaturated carbon chain, filler and a minor, running temperature reducing amount of at least one aromatic furazan oxide of the partial formula

wherei^'n the depicted carbon atoms are part of a single aromatic ring. 22. A method of promoting rubber-filled interaction in a filled vulcanizate containing at least one rubber having an unsaturated carbon chain and carbon black and/or silica filler which comprises including in the vulcanizate a minor, ₍ filler-interaction-promoting amount of aromatic furazan oxide of the partial formula:

C N

C N >

wherein the depicted carbon atoms are part of a single aromatic ring.

S ' ^