CA1162674A - Method and skim stock composition for improving steel cord adhesion in multiple ply tire building - Google Patents

Abstract

A rubber ply skim stock anchored and reinforced by means of brass plated steel wire cords in said ply useful in the manufacture of multiple ply tires, characterized in that the skim stock includes the synergistic combination of at least one aromatic triazole and a cobalt or nickel soap of an oil soluble organic acid wherein in one hundred parts by weight of the rubber in said skim stock said triazole is present in an effective amount which does not exceed 0.5 parts by weight and said soap is present in an effective amount which does not exceed about 3.0 parts by weight. This form of skim stock when used in a pneumatic vehicle tire provides improved adhesion between the rubber of the tire and the brass plated steel cords.

Description

1 1 6267~

~ his invention relates to the building or manufacturing of steel cord reinforced belted ply rubber products and more specifically poly ply pneumatic tire casings primarily used in automotive vehicles.
More particularly, according to one aspect this invention relates to an improved ply skim stock formulation involving two additives which when used together in minor quantities enhance the adhesion of the skim stock for the brass plated steel reinforcing cords normally calendered in a sandwich between layers of skim stock to make up the belted plies used in building pneumatic tire casings.
Specifically, this invention provides a combination of additives in the ply skim stock, when used as described, act synergistically to enhance adhesion between rubber skim stock and the brass plated steel reinforcing wires. ~he said combination consists essentially of not materially greater than about 3.0 parts preferably not greater than 2.5 parts of a nickel or co-balt soap of an oil soluble oreanic acid.
According to an aspect of the present invention there is provided a composition of rubber having improved adhesion to metal which comprises for each 100 parts by weight of rubber a) a triazole in an amount not exceeding 0.5 parts by weight and b) a substantially oil soluble metal compound of an organic acid in an amount not exceeding 3.0 parts by weight, wherein the metal of the metal compound is selected from the group consisting of nickel, cobalt and combinations of nickel and cobalt.
A composition of rubber having improved adhesion to metal may com-prise at least about 0.01 part by weight for each 100 parts by weight of rubber of at least one triazole selected from the group consisting of benzo-triazole and lower alkyl derivatives of benzotriazole and at least about 0.5 parts by weight for each 100 parts by weight of the rubber of at least one '~

i.

i 3 626~4 substantially oil soluble metal compound of an organic acid wherein the metal is selected from the group consistin~ of nickel, cobalt and combina-tions of nickel and cobalt.
The triazole may be an aromatic triazole such as, for example7 benzotriazole, tolyltriazole or mixtures thereof.
The present invention also provides a rubber ply skim stock an-chored and reinforced by means of brass plated steel wire cords in said ply useful in the manufacture of multiple ply tires, characterized in that the skim stock comprises the synergistic combination of a triazole and a cobalt or nickel soap of an oil soluble organic acid wherein in one hundred parts by weight of the rubber in said skim stock said triazole is present in an effective amount which does not exceed 0.5 parts by weight and said soap is present in an effective amount which does not exceed about 3.0 parts by weight. Preferably the soap is a cobalt salt of an oil soluble aliphatic acid. Preferably the triazole is tolyltriazole.
According to the present invention triazole may be present in an amount not exceeding 0.2 parts by weight and the soap may be present in an amount not exceeding 2.5 parts by weight.
Also according to the present invention the soap may be present in an amount of from about 1.0 part to less than 3 phr and the triazole may be present in an amount of from about 0.05 parts to not more than 0.5 phr in the said skim stock.
According to another aspect of the present invention there is pro-vided the method of increasing adhesion of bra~s plated steel reinforcing cords integrally within tire cord ply skim stock which comprises masticating in the skim stock formula prior to incorporation of said steel cords and vul-canization of said ply about a multiple ply tire, a quantity but not more than about 0.2 phr of a triazole and a quantity but not more than 3 phr of a 1 1 ~2674 metal salt of an oil soluble organic acid where the metal is selected from cobalt and nickel ions. The triazole may be benzotriazole and/or the alkyl (e.g. lower) derivatives thereof and the metal salt may be a cobalt salt of an oil soluble aliphatic organic acid.
By oil soluble organic acid is intended those acids commonly used to manufacture oil soluble metal soaps or salts as are illustratively used as catalysts to promote oxidation and polymerization of drying oils, as driers in the paint and varnish industry. ~hese acids range from the strai~Pt aliphatic acids having about 8 carbon atoms to about 22 carbon atoms, both saturated and unsaturated. Also included are acids containing aromatic groups of complex nature including as illustrative, naphthenic acids. Some of these acids have been selected for use in rubber formulations. So far as has been determined, the structures of the acid co~ponent is not critical, only that it be compatible (soluble~ in hydrocarbon acids, drying acids, etc., so as to provide intimate contact of the metal cation of the product metal soap or salt with the rubber formulation. ~he other essential compon-ent as indicated above should not be in excess of about 0.5 parts by weight comprising a triazole, e.g. benzotriazole or an alkyl derivative, per hundred parts of rubber (hereinafter sometimes identified as phr) in the ply. His-torically, aliphatic long chain fatty acids have been used of themselves inrubber compounding and are suitable for the ends of this invention as a source of oil soluble organic anion.
In recent year~ in the United States brass plated steel cords have come into prominence as replacement for earlier organic cord material used in both bias ply and radial ply construction. Concern has developed over ; the dangers inherent in steel belted tires should water and corrosion agents associated therewith reach the surfaces of the reinforcing steel cords em-bedded in the ply skim stock. It is known that under such physical condi-1 1 8267~

tions the surfaces of the brass coated steel cords corrode or rust progressively from a point of any break in adhesion between ply stock and wire band. With entry of water borne contaminants, the bond between the metal cord and skim stock progressively deteriorates and adhesion is destroyed, much as a zipper opens serially from a point of beginning. The United States Department of Transportation has been openly concerned with the obvious danger.
It is known, for example, that Shemenski of Goodyear in German Offenlegensschrift 2,611,761 of October 28, 1976 disclosed a process for treat-ment of brass coated steel tire cords to increase adhesion. In that disclosure reference is made to prior art where a mineral oil solution of a salt of a long chain fatty acid and a very small amount of triazole (benzotriazole) were used in a treatment (immersion) of the plated brass coated steel cord.
The Shemenski disclosure appears to suggest treatment of a clean brass coated steel tire cord with, among other things, selected triazoles. The steel cord is apparently treated with a complex polymer film-former consisting of benzotriazole and anions selected from the group consisting of chromates, nitrites, tungstates, molybdates, dichromates, arsenites and sulfites and cations of a salt which contains these anions including cyclohexylamine, iron, cobalt, nickel, tin or zinc. As the reference is understood, a single aqueous solution containing all the additives is most efficient and economical.
United States Patent 3,413,227*discloses broadly that triazoles are useful in synthetic polymers and polishes to inhibit corrosion.
German Offenlegensschrift 2,227,013 of Decmeber 13, 1973 (based on a Yokohama Rubber Co., application) also relates to improvement of adhesion of variously plated steel tire cords. It is also understood to suggest surface *Issued November 26, 1969 to Geigy Chemical Corp.
!~ - 4 -treatment of the plated steel cords with an aqueous medium. The treatment is said to be effective after exposure to high humidity of liquid water.
Coconut amine acetate, tallow amine salicylate in mineral oil and aqueous triazoles in water are listed. The rubbers in which the treated wires are embedded are shown to contain in one instance (Table 2) 10 parts of cobalt naphthenate and 0.5 parts of methylbenzotriazole per 100 parts of rubber. Most rubber stocks disclosed contain no oil soluble metals soaps, but all contain methylbenzotriazole.
The objective of the reference patent permits long periods of time between embedment of the plate steel cord in the unvulcanized rubber stock in humid atmospheres and vulcanized thereafter of the aged stock without loss of adhesion of the steel cords to the rubber ply stock.
United States Patent 3,849,433(1) discloses use of specific tetra-hydrobenzotriazole derivatives as corrosion inhibitors for copper and copper alloys (brass) and anti-aging agents or antioxidants.
United States Patent 3,367,907(2) is directed to the stabilization of polyethylene polymers due to contact with copper by use of benzotriazole referred to as azimido benzene which new nomenclature more stickly calls l,H-benzotriazole.
The latter references are relevant to show use of various traizoles in polymeric stocks of elastomeric value as useful to inhibit copper plated steel cord corrosion.

(1) Issued November 19, 1972 assigned to Rhein - Chemie Rheiman GmbH.

(2) Issued February 6, 1968 assigned to Bell Telephone Labs.

7 1 6~G7 4 The following discloses the best known practice of the invention:
A series of ply skim stocks were prepared in which the variations were only in the presence or absence of a cobalt (soap), the presence or absence of a triazole (tolyltriazole was chosen for the study) and as to the treatment of the brass (65 - 25% copper, remainder zinc) plated steel reinforcing cord, whether treated with triazole or untreated and whether the steel - 5a -i J 62674 cord was sub~ected to aging at higll humidity environment (containing a des-sicant or siccative agent such as silica gel).
The basic poly skim stock formula or recipe selected for the tests is considered relatively standard in the manufacture of pneumatic tire ply stock. Manufacture of the green, uncured or unvulcanized, rubber formulas followed standard mixing procedure using a Banbury mixer. The term "phr" as used herein indicates the parts by weight of the named ingredient per hundred parts by weight of the selected volcanization elastomer or rubber. Rubber is used herein in a generic sense and is intended to include both natural and synthetic rubbers.
All of the test formulas were made over the following schedules:
The Banbury water temperature was 150F and the rotor speed held at 45 rpm.
One hundred parts of rubber were weighed into the mixer and after 4 minutes, 2 parts of an anti-ozonate (Santoflex 13* of Monsanto: N-(1,3, dimethylbutyl)-N-phenyl-P-phenlenediamine); 0.4 parts P.V.I.* (Pre-vulcaniza-tion inhibitor, a proprietary Monsanto product being a blend of a sulfenamide accelerator and an organic inhibitor or retarder). P.V.I.* imparts scorch safety in later processing; 27 1/2 parts of a black pigmented rubber master batch (N 330 HAF)* a high abrasion furnace carbon black; 1 part stearic acid;
and when a part of the test formula, 2.5 parts of a 16% cobalt containing oil soluble metal soap (cobalt naphthenate). Sometimes these soaps are called the metal salts of oil soluble organic acids such as naphthenic and octoic acids.
Manobond* C-16**(Manche~,Ltd.) has been used in illustrating specific formulas identified herein. Tolyltriazole is representative of the azoles.
After four minutes of heavy shear in the Banbury, another 27 1/2 ** (Manobond C-16 is stated to contain a compound of the formula (R-CO2-Co-0)3B
where R is a branched hydrocarbon chain having an average of 21 carbon atoms, 5 of which were in methyl radicals; R may have a value of 18 to 22.) * Trade Mark ~. ., parts of the black pigment master batch and ~ parts of naphthenic oil were incorporated. Into the rubber next was milled 5 parts Crystex* Sulfur (a Stauffer Chemical product containing a minimum of 90% amorphoruks allotrope of sulfur and the remainder principally rhombic sulfur in 2 to 3 micron size state insoluble in oil); 0.75 parts of Vulkacit* DZ, (Bayer-Germany, under-stood to be N,N-dicyclohexyl-2-benzothiazyl sulfenamide, and after ten minutes the mill is cleaned and dumped. The temperature was recorded at the end of the mixing time.
In all the examples produced for test the stocks handled well, processed normally and the temperature before dumping was 275F. These ex-amples are summarized in the following "Summary Table".

1 ~ 62674 SUMMARY TAB_ PLY SKIM STOCK FORMVLATIONS
TEST BLOCKS VULCANIZED
Material Blank ControlExp. 1 Exp. 2 Exp. 3 Natural Rubber 100.0 100.0 100.0 100.0 100.0 N330 (HAF) Black 55.O 55.0 55.0 55.0 55.0 Naphthenic Oil 4.0 4.0 4.0 4.0 4.0 Zinc Oxide 6.0 6.0 6.0 6.0 6.0 Stearic Acid l.O l.O 1.0 l.O l.O
(Metal Soap*) --- 2.5 --- ___ ___ Santoflex 13 2.0 2.0 2.0 2.0 2.0 COBRATEC TT-100$ ** --- --- 0.2 0.2 0.5 TT-100 Treated Steel Cord --- --- No Yes No Crystex Sulfur 5.0 5.0 5.0 5.0 5.0 Vulkacit DZ 0.75 0.75 0.75 0.75 0.75 P.V.I. 0.40 0-40 0.40 0 40-174.15 176.65 174.35 174.35 174.65 SUMMARY TABLE CO~TINUED
MaterialExp. 4 Exp. 5 Exp. 6 Exp. 7 Exp. 8 Natural Rubber 100.0 100.0 lOO.0 100.0 100.0 N330 (HAF) Black 55.0 55.0 55.0 55.0 55.0 Naphthenic Oil 4.0 4.0 4.0 4.0 4.0 Zinc Oxide 6.0 6.0 6.0 6.0 6.0 Stearic Acid 1.0 l.O 1.0 1.0 l.O
Metal Soap*) --- 2.5 2.5 2.5 2.5 Santoflex 13 2.0 2.0 2.0 2.0 2.0 COBRATEC TT-100~ 0.5 0.05 0.5 0.2 0.2 TT-100 Treated Steel Cord Yes No Yes No Yes Crystex Sulfur 5.0 5.0 5.0 5.0 5.0 Vulkacit DZ 0.75 0.75 0.75 0.75 0.75 P.V.I. 0.40 0.40 0.40 0.40 0 40 174.65 176.60 176.60 176.85 176.85 * Manobond C-16 (Cobalt soap of long chain oil soluble organic acid.) Refers to totyl triazole.
** Trade Mark ~ 1 6~674 One aliquot portion of each batch was subJected to standard rhe-ometer testing according to ASTM D-2084 standards at 290F, using 3 of arc in the conical head, 100 cpm (cycles per minute), MPC Dyes (micro production control dye) in the press, 20 seconds to preheat and a 60 minute test scan.
Time torque curves were automatically plotted as a data source on graph paper.
A second aliquot portion was used on unaged brass plated steel cord, 12 steel wire cords are used in each test block. The cords were in-corporated into the unvulcanized test rubber stocks by calendqring the test portions and forming a compressed sandwich of the steel cord strands in the rubber matrix. Each set of cords in the test blocks were then vulcanized in place at optimum cure as determined by rheometer (Monsanto) data at 290F.
Standard adhesion tests as in ASTM D-2229 were performed, and the data recorded. Additionally, sets of wires vulcanized in skim stock test strips were aged for seven (7) days at 70~ to 80% R.H. Comparative sets not so aged were compared as reported in Table II.
In the tests herein identified as "Blank" or "B", there was no oil ~oluble organic cobalt soap or salt, nor tolyltriazole and the steel was not treated with triazole. The "Control" of C skim stock contained a standard amount of cobalt soap or salt of an oil soluble organic acid and the steel cord was not triazole treated. Experiment 1 had no cobalt soap but 0.2 phr of tolyltriazole. The steel cord was not treated. Experiment 2, no cobalt soap, but the wire was tolyltriazole treated. Treatment consists of immers-ing brass coat~d steel wire in a 0.2% by weight triazole in water solution at 140F for two minutes. Wire loops are withdrawn, rinsed with distilled water, dried for 1 hour in an oven at 100F, and stored in a dessicated atmosphere for test. Experiment 3 was identical with Experiment 1 except the amount of triazole was increased to 0.5 parts, the wire was not treated.

_ g _ ,:

Experiment 4 was identical to Experiment 3, but the wire was triazole treated. Experiment 5, the amount of the cobalt soap was 2.5 parts; the triazole was reduced to only 0.05 parts and the steel wire cord was not triazole treated. Experiment 6 was identical to Experiment 5 except the wire cord was triazole treated. Experiment 7 had increased triazole in the skim stock of 0.2 part or four times as ~uch as in Experiment 5, but was otherwise identical to Experiment 5. Experiment 8 was identical to Exper-iment 7, except the wire cord was treated with triazole ttolyltriazole).
All wire surface treatment, with tolyltriazole were the same. The above data and test results are set out in the Tables which follow.
The wire adhesions were separately determined on each of the thir-teen cords of brass plated steel wire (5 separate strands were in each cord bundle) both aged and unaged and the average figure is reported, along with the high and the low values in each of the foregoing adhesion experiments.
To facilitate the essential comparisons, the observed readings are set out in the following Tables I and II. In order that concepts involved in this disclosure may be fresh in mind, definitions below may be helpful.
In rheometer cure and adhesion tests (see ASTM D-2084 and D-2229, respectively) and from data inherent therein the following factors are to be found:
Minimum torque or ~ is the lowest point on the curve and is be-fore vulcanization begins. The maximum torque or ~ is the maxi~um torque developed during the sixty minutes of the test run. The scorch time is de-noted by tS2. As vulcanized or crosslinking begins, the foot pounds of torque increase. The time in minutes from ~ to a two number point rise in torque defines the "scorch time". This time is representative of the safety period available in commercial ~llcanization operations and it is important that it not be materially shortened. It is desirable to have a relatively 1 3 6267~

long time period to onset of the defined two point rise in torque. Ti~le to 90% of maximum torque tc (90) is recorded. While the selection of 90% is arbitrary, optimum physical properties are developed in the test specimen by this time. It is also desirable that the curve flatten out substantially parallel with the time axis, as this flat characteristic of the curve demon-strates control over the final cure quality that it can be held uniform from batch to batch. This control data where collected of record then allows knowledge of a predictable state of cure. It is useful in a study of addi-tives, as additives to ply skim stock studies determine influence of use of the additives on the final rubber tire quality.
In t}le wire cord pullout tests used in measuring adhesion of the ply wire cord, the pullout forces essentially change with time after vulcan-ization. It is desirable, therefore, to keep this time uniform in compar-ative testing. Wire adhesion is reported in the pounds of force required to pull each one of the thirteen steel wire cords individually from the vulcan-ized rubber test block.
The following tables present the various test data and identify briefly the foregoing skim stock formulation identity.

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As Table II is ~irected specifical~y to the adhesion tests, an analysis of the data there presented is of specific i~portance.
Example 6 is ~irst noted as the adhesion i5 the poorest ~alue on the unaged sample. It will be found that the skim stock here i6 identical to that in Example 5, except that the unaged sample was pretreated with tri-azole. Example 5, on the other hand, is outstanding in that the unaged sample required 126.2 lbs. of pull to break the rubber-wire adhesion in the unaged sample and 114.6 lbs. with the aged sample, a loss of 12 or 9.52%.
Example 6, ~arying only in the pre-treatment of the sa~ple witb triazole, lost 90 lbs. of adhesion force or 71.4% of its unaged adhesive strength throuBh pre-coating the wire with the triazole, when the skim stock con-tained the synergistic combination of metal soap and triazole alone, as in Example 5.
It is also obser~ed that the aged sample in number 6 is practically identical in value to the unaged sample, no apparent effect, for better or worse. Howe~er, the adhesion in both cases is very poor.
Returning to Example 5, we find not only the highest adhesion of wire to skim value in the unaged sample, but also in the aged sample, with a 1088 upon aging o~ 9.52%. Example 7, identical in composition to Example 5~
except it has 0.20 parts triazole, about 4 times the quantity, has about 11%
less adhesion resulting in the unaged sample, but 7 1/4Z less adhesion after aging. This suggests that the amount o~ triazole used in the skim stock is critical and while 0.2 part (phr) in the synergistic combination is not max-imum, further attention should be given to other cited factors in the skim stock, as may be shown and more clearly apparent from the rheometer tests (~able I).
Referring to Table I, it is observed that Example 5 and Example 7 provide no unusual data, except it is noted that the scorch time is somewhat ~ 3 ~2674 reduced over the Blank. This sugeests that one or both the additives are adversely affecting the safe or scorch period. The Control, which contains the oil soluble, organometallic soap only has an extremely shortened scorch time of the order of about 39% decrease over the Blank Ex. 1 contains no metal soap but some T~ (tolyltriazole) and has lost only about 5% of scorch time t9.0 to 8.5). However, Ex. 1 (Table II) is over 48% poorer in adhesion (unaged) and over 22% poorer in adhesion that the (aged) wire tests. Atten-tion having been called to the rheometer data of Table I as to Ex. 1, it is also startling to find the time to 90% cure for the Blank. Ex. 1 containing no (metallic soap), and also Ex. 3 which contains no metallic soap as having 90% cure-times over 125% greater than when the metallic soap is in the syn-ergistic combination (with the triazole) as in Examples 5 and 7. One also observes in Table I that the Examples 5 and 7 have gained back most of the safety period scorch time lost between the Blank (no metal soap) and the Con-trol (metal salt alone) was used. Note Examples 5 and 7 both contain the combination and demonstrate a desirable recovery in scorch time and a min-imal effect on cure time.
There are several other observations and conclusion~ of consider-able intere~t that can be formed upon study of the data presented in the Tables which suggest other areas of exploration which may be of value. We leave these for further study and consideration.
One should preferably avoid use of brass plated reinforcing wire treated with triazole, for in all observed instances where brass plated steel cord was exposed to the triazole prior to incorporation in the green or unvulcanized skim stock, the skim stock adhesion to the plated wire after vulcanization was not above 44 pounds (See Ex. 4, aged wire). Such wire treatment in the practice of this invention does not appear to be advan-tageous ~

i 1 62674 In summary, one finds that less than 3 parts by weight of an oil soluble me~al compound of an oreanic acid wherein the metal is selected from cobalt, nickel and mixtures thereof per 100 parts of rubber stock and from trace amounts to not ~ore than 0.5 parts of a triazole and preferably less than 0.2 parts of triazole in combination with selected metal soaps or salts of oil soluble fatty acids in an amount but not greater than about 2.5 phr produces an unexpected increase in adhesion of the brass plated steel tire cord when part of the original skim stock recipe (after vulcanization).
Amounts within the preferred synergistic combination of triazole (e.g. benzo-triazole and the lower alkyl derivatives thereof) ana metal soaps are also found not to interfere with the scorch time and the cure time. Xowever, when larger amounts of the named additives are used, the latter values, critical to practical application and adhesion increase may be materially altered.
An example is where the metal soap component is from about one part to less than about 3.0 phr and the triazole is from 0.05 parts to not m~re than 0.5 phr in the said skim stock.
Specifically, the quantity of triazole is not more than about 0.2 phr and the quantity of metal salt of an oil soluble organic acid where the metal is selected from cobalt and nickel ions is not more than 3.0 phr.
~he present invention also relates to a pneumatic vehicle tire con-taining rubber, filler, curing agent, brass-to-rubber bonding agent other than cobalt, cure accelerator, carbon black and zinc oxide, the tire being reinforced at least in part with brass plated steel cord, and characterized by the presence of an effective amount of an aromatic triazole in the rubber surrounding the steel cord.
The present invention further relates to a pneumatic vehicle tire containing rubber, filler, curing agent, brass-to-rubber bonding agent other than cobalt, cure accelerator, carbon black and zinc oxide, the tire being reinforced at least in part with brass plated steel cord, whereln the im-provement comprises the presence of up to 0.5 phr of an aromatic triazole in the rubber surrounding the steel cord.
The triazole may be selected from the group consisting of benzo-triazole and totyltriazole.
The tire may include the presence of effective amounts of a rub-ber-to-brass adhesion promoter containing cobalt in the rubber surrounding the steel cord, preferably including the presence of up to 2.5 phr of the adhesion promoter containing cobalt. An antioxidant may be present in the rubber surroundine the steel cord.

Claims (20)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A rubber ply skim stock anchored and reinforced by means of brass plated steel wire cords in said ply useful in the manu-factur of multiple ply tires, characterized in that the skim stock includes the synergistic combination of at least one aromatic triazole and a cobalt or nickel soap of an oil soluble organic acid wherein in one hundred parts by weight of the rubber in said skim stock said triazole is present in an effective amount which does not exceed 0.5 parts by weight and said soap is present in an effec-tive amount which does not exceed about 3.0 parts by weight.

2. A rubber ply skim stock as claimed in claim 1 where the soap is the cobalt salt of an oil soluble aliphatic acid.

3. A rubber ply skim stock as claimed in claim 1 wherein the triazole is present in an amount not exceeding 0.2 parts by weight and the soap is present in an amount not exceeding 2.5 parts by weight.

4. A rubber ply skim stock as claimed in claim 2 where the triazole is tolyltriazole.

5. A rubber ply skim stock as claimed in claim 4 wherein the soap is present in an amount of from about 1.0 part to less than about 3 phr and the triazole is present in an amount of from about 0.05 parts to not more than 0.5 phr in the said skim stock.

6. The method of increasing adhesion of brass plated steel reinforcing cords integrally within tire cord ply skim stock which comprises masticating in the skim stock formula prior to incorpora-tion of said steel cords and vulcanization of said ply about a multiple ply tire, a quantity but not more than about 0.2 phr of at least one aromatic triazole and a quantity but not more than 3 phr of a metal salt of an oil soluble organic acid where the metal is selected from cobalt and nickel ions.

7. The process of claim 6 where the triazole is benzotriazole and/or the alkyl derivatives thereof and the metal salt is the co-balt salt of an oil soluble aliphatic organic acid.

8. A composition of rubber having improved adhesion to metal which includes for each 100 parts by weight of rubber a) at least one aromatic triazole in an amount not exceeding 0.5 parts by weight; and b) a metal compound of an oil soluble organic acid in an amount not exceeding 3.0 parts by weight, wherein the metal of the metal compound is selected from the group consisting of nickel, cobalt and combinations of nickel and cobalt.

9. A composition of rubber as claimed in claim 8 which in-cludes at least about 0.01 part by weight of each 100 parts by weight of rubber of at least one triazole selected from the group consisting of benzotriazole and lower alkyl derivatives of benzo-triazole and at least about 0.5 parts by weight for each 100 parts by weight of the rubber of at least one metal compound of an oil soluble organic acid wherein the metal is selected from the group consisting of nickel, cobalt and combinations of nickel and cobalt.

10. A rubber-based pneumatic vehicle tire reinforced at least in part with brass plated steel cord, characterized by the presence in the rubber surrounding the steel cord of a synergistic combination of at least one aromatic triazole and a cobalt or nickel soap of an oil soluble organic acid wherein in one hundred parts by weight of the rubber in said skim stock said triazole is present in an effective amount which does not exceed 0.5 parts by weight and said soap is present in an effective amount which does not exceed about 3.0 parts by weight.

11. The tire of claim 10 further characterized by the triazole being selected from the group consisting of benzotriazole and tolyltriazole.

12. The tire of claim 10 characterized by the presence of effective amounts of a cobalt soap in the rubber surrounding the steel cord.

13. The tire of claim 10 characterized by the presence of up to 2.5 phr of a cobalt soap in the rubber surrounding the steel cord.

14. The tire of claim 10 wherein an antioxidant is present in the rubber surrounding the steel cord.

i 1 62674

15. A composition of rubber having improved adhesion to metal which includes for each 100 parts by weight of rubber a) at least one aromatic triazole in an amount not exceeding 0.5 parts by weight; and b) a cobalt compound of an oil soluble organic acid in an amount not exceeding 3.0 parts by weight.

16. The composition of claim 15 wherein an antioxidant is present in the rubber.

17. A rubber ply skim stock anchored and reinforced by means of brass plated steel wire cords in said ply useful in the manufacture of multiple ply tires, characterized in that the skim stock includes the synergistic combination of at least one aromatic triazole and a cobalt compound of an oil soluble organic acid wherein in one hundred parts by weight of the rubber in said skim stock said triazole is present in an effective amount which does not exceed 0.5 parts by weight and said compound is present in an effective amount which does not exceed about 3.0 parts by weight.

18. A rubber ply skim stock of claim 17 wherein an antioxidant is present in the rubber.

19. A rubber-based pneumatic vehicle tire reinforced at least in part with brass plated steel cord, characterized by the presence in the rubber surrounding the steel cord of a synergistic combination of at least one aromatic triazole and a cobalt compound of an oil soluble organic acid wherein in one hundred parts by weight of the rubber in said skim stock said triazole is present in an effective amount which does not exceed 0.5 parts by weight and said compound is present in an effective amount which does not exceed about 3.0 parts by weight.

20. The tire of claim 19 wherein an antioxidant is present in the rubber surrounding the steel cord.