NO151591B - METAL ALARMED RUBBER LAMINATE WHICH THE RUBBER MENTION IMPROVED ADHESION TO A METAL PART IN CONTACT WITH THE RUBBER MIXTURE - Google Patents

Description

The present invention relates to a metal-reinforced rubber

laminate where the rubber part has improved adhesion to a metal part in contact with the rubber mixture which contains a significant proportion of natural rubber or mixtures of natural

rubber and butadiene rubber, and the peculiarity of the metal

reinforced rubber laminate according to the invention is that it contains 0.5 to 8.0 parts cobalt and/or nickel salt of p-aminobenzoic acid per 100 pieces of rubber.

These features of the invention appear in the patent claim.

US patent 3,517,722 describes a rubber-metal adhesion system which includes the formation of a resorcinol-formaldehyde resin in the interface between rubber and metal to thereby bind these elements together. During the formation of the resin, compounds are added which are able to release the methylene to resorcinol in the rubber mixture. When vulcanizing none, the methylene and resorcinol react to form the resorcinol-formaldehyde resin.

According to US patent 3,846,160, the adhesion force between steel cord and rubber is improved by applying a mineral oil solution such as contains an organic acid salt of a higher aliphatic amine on zinc-plated or brass-plated steel cord.

Adhesion of rubber to metal such as e.g. wire-tyre cord is improved according to US Patent 3,847,727 by incorporating a halogenated quinone and the condensation product of resorcinol and acetaldehyde into the rubber before application to the metal and vulcanizing neither composition.

US patent 3,903,026 teaches the production of a rubber compound with improved metal adhesion properties even after temperature aging and this is shown to be achieved by mixing cobalt carboxylate and magnesium oxide (0.1 to 4%) into the rubber.

US Patent 3,738,948 relates to a fiber-reinforced rubber compound that can be used in tire construction. The fibers can consist of glass, nylon, rayon or metal wire. The mixture contains a finely divided silicon oxide, hexamethylenetetramine, resorcinol and a miscible metal soap such as calcium tearate. Similar compositions containing discontinuous fiber filaments are disclosed in US Patent 3,746,669.

US Patent 3,340,214 teaches the use of benzoic acid or nitrobenzoic acid as an additive to reduce the elasticity of rubber used e.g. in the manufacture of wheel tyres.

In the present invention, the cobalt and nickel salts of p-aminobenzoic acid (PABA) have been shown to be very effective.

In the method for producing the said mixture, the said metal salts of PABA are mixed into a rubber mixture which is described below, after which the obtained mixture is brought into contact with a metal element in an unvulcanized product and the product is vulcanized to give a final product.

The para-aminobenzoic acid used to illustrate the present invention was specified to have a molecular weight of 137.14, a melting range of 188 to 189°C and a density at the melting point of 1.374. It was classified as 99% pure.

The aforementioned salts of p-aminobenzoic acid can be prepared by adding p-aminobenzoic acid (1 mol) to a solution of sodium hydroxide (1 mol) in 900 ml of distilled water at room temperature under mechanical stirring. To the resulting brown solution of the sodium salt of p-aminobenzoic acid is slowly added a solution of the chloride salt of the metal used (0.506 mol) in 100 ml of distilled water at room temperature with stirring. A reaction immediately takes place which forms a precipitate. After the addition is complete, the reaction mixture is stirred at room temperature for a further 3 hours. The solid is then collected on a filter, washed with a small amount of water and dried at 120°C

overnight under vacuum. After this drying step, the used metal salt of p-aminobenzoic acid is obtained in high yield.

Cobalt p-aminobenzoic acid was prepared by adding p-aminobenzoic acid (137 g, 1 mol) to a solution of sodium hydroxide (40 g, 1 mol) in 900 mL of distilled water at room temperature with mechanical stirring. To the resulting brown solution of the sodium salt of p-aminobenzoic acid was slowly added a solution of cobalt (II) chloride (120 g, 0.506 mol) in 100 mL of distilled water at room temperature with stirring. A reaction took place immediately to form a pink precipitate. After the addition was complete, the reaction mixture was stirred at room temperature for a further 3 hours. The solid was collected on a filter, washed with a small amount of water and dried at 120°C under vacuum overnight. After this drying step, dark purple solid cobalt-p-aminobenzoic acid was obtained in 81% yield (135 g).

Use of the aforementioned cobalt and/or nickel salts of PABA will significantly improve the adhesion to metal in contact with the rubber mixture.

The rubber mixture is described with all components based on the total rubber component in the mixture as 100 parts by weight.

The mixture used in the examples consists of 100 parts rubber, 40 to 70 parts carbon black per 100 parts, 4 to 10 parts zinc oxide per 100 parts, 10 to 30 parts silicon oxide' per 100 parts, 0.5 to 1 part antioxidant per 100 parts, 0.5 to 1 part stearic acid per 100 parts, 0.2 to 2.0 parts accelerator per 100 parts, 1 to 10 parts hydrocarbon resin per 100 parts, 2 to 6 parts resorcinol per 100 parts, 1 to 5 parts "Manobond C" per 100 parts, 4 to 9 parts sulphur/oil, 80/20, per 100 parts, 4 to 9 parts melamine resin per 100 parts and 2 to 8 parts of the mentioned metal salts of PABA per 100 parts.

The following examples illustrate the invention. Mixing component quantities are expressed in parts per 100 parts rubber, unless otherwise stated. These components are generally within the limits stated in the following:

Starting mixture Final mixture

Specific detailed examples of usable mixtures within the above stated limits are:

EXAMPLE 1

The following mixture was processed in a Banbury mixer at about 138 to 171°C for 7 minutes, or at 171°C for the same time, and a rotor speed of 80 rpm. minute. The resulting starting mixture was then withdrawn. The Banbury mixer was a so-called "Type B Internal Mixer".

The hydrocarbon resin was in flake form, had a softening temperature between 100 and 110°C, an iodine number of 125 to 167 and an ash content of 0.05%. The starting mixture obtained was then end-roll mill mixed for 4 to 8 minutes until dispersion was achieved at a mill speed of about 50 revolutions per minute. minute and a temperature of from 71 to 82°C. The resulting final mixture was then withdrawn. The mix components added to the starting mix before the final roll mill mix was made were as follows:

This product was cured for 30 minutes at 149°C, a curing pressure

of 55.2 to 62.1 kg/cm 2 and constitutes the mixture according to

invention listed in the following table I. The blank is the identical mixture without nickel-p-aminobenzoic acid.

Table I which follows illustrates the properties of the Ni-PABA containing mixture in combination with ordinary steel wire (uncoated) and shows two contents of Ni-PABA.

EXAMPLE 2

Approximately the same results as in Table I are obtained when the following starting mix and additive mix are added before the final roll mill mix:

Output mixture

Blend added to the above starting blend

EXAMPLE 3

A starting mixture identical to that described in Example

1 was mixed. This starting mixture was mixed into a final mixture using the method described in example 1 in which the following components were added to the final mixture:

This product was cured for 30 minutes at 149°C, a curing pressure of 55.2 to 62.1 kg/cm 2 and the properties of this mixture are given in the following Table II. The control sample is the identical mixture without cobalt-p-amino-benzoic acid.

The following Table II illustrates the properties of the Co-PABA-containing mixture in combination with ordinary uncoated steel wire.

EXAMPLE 4

Approximately the same results as in Table II are obtained when the following starting mix and additive mix are added before the final roll mill mix is made:

Starting mixture Mixture added to the above starting mixture

The results for the wire adhesion testing indicated

for plain steel wire (uncoated) in the preceding examples was determined by the following T-adhesion method.

T-adhes j ontest

1. Using a cutting machine and a mold approximately 15.2 x 1.27 cm in size, an appropriate number of experimental and control samples for patch construction were prepared. 2. A piece of calendered textile backing (1.3 mm) was used. 3. A piece of control rubber compound (1.52 mm) was applied to the textile-fabric substrate. 4. The sample was placed in the construction device with the textile side down. 5. 10 iron wires with a length of approximately 17.8 cm were placed at an equal distance from each other on top of the composition of the two pieces.

6. Another two-layer composition, prepared as in points 1,

2 and 3 above were reversed on top of the threads so that the threads were between the two layers of pulp to be tested.

7. This composition should now fit well into the mold.

8. Adhesion patches must be cured for 30 minutes at 149°C and then allowed to dry for 24 hours.

9. Testing machine; 1130 "Instron Universal Tester".

10. Test speed 25 cm/minute; temperature 110°C after a

20 minute pre-heating.

11. The top grip must be made with a special holder made for the hardened sample, with a slot in the bottom so that the sample can be inserted with the wire sticking out. The bottom grip should be of the wedge type so that it exerts increasing locking when the thread is pulled out. 12. 10 draws are made and the average is determined. It is multiplied by two to determine kg of adhesion per embedded cm' wire.

Properties of some of the components indicated in the examples are listed below. These definitions are to be regarded as illustrative of known materials which have proved useful in this invention.

The rubber mixture also preferably contains a suitable amount of a conventional organic cobalt complex, e.g. a material sold under the name "Manobond C". Such materials, including "Manobond C" are known to facilitate rubber-to-metal adhesion.

"Manobond C" is a commercially available source of a cobalt and boron containing additive which is miscible with the present rubber compound and is believed to have the structure:

wherein each "R" is an alkyl radical having from 9 to 12 carbon atoms. "Manobond C" is available as a blue, viscous liquid. It contains 15.5 to 16.5% cobalt ("Manobond C 16") or it contains 17.5 to 18.5% cobalt (Manobond C 18"). It has a specific viscosity (at 25°C) of 3000 to 9000 eps. The ash content is from 22 to 25% by weight.

The rubber used in the practice of this invention includes vulcanizable rubber types with a significant content of natural rubber or a mixture of natural rubber and polybutadiene. An extender oil may optionally be used and may consist of any known additive oil derived from aromatic or naphthenic hydrocarbons.

The antioxidant can e.g. be N-(1,3-dimethyl-butyl)-N'-phenyl-p-phenylenediamine known as "Santoflex 13" or other phenyl-p-phenylenediamine derivatives.

The accelerator that is preferred is used during exercise

of the invention is N-oxydiethylene-benzothiazole-2-sulfenamide which is commercially available as "NOBS Special".

Other accelerators such as N-t-butyl-2-benzothiazole sulfenamide can also be used. The particular accelerator chosen is not critical.

Any known rubber-reinforcing carbon black products can be used, such as e.g. "FE F ";"I SAF "and other carbon black products. Curing is preferably achieved by using sulfur as a sulphur/oil mixture preferably used in a quantity ratio of 80/20. The use of "FEF" carbon black is preferred.

The pelletized hydrated silica is commercially available. The preferred silica is designated "Hi-Sil 233".

Commercially available hydrocarbon resins used in the invention include e.g. "Betaprene 105" and "Picco 14215". Included are the intermediate and aliphatic hydrocarbon resins that are otherwise commercially available. The preferred hydrocarbon resin preferably has a softening point of from about 100 to about 110°C, an iodine value of from about 125 to about 167 and a maximum ash content of 0.05%.

The melamine resin is preferably "Cyrez 963".

The preceding examples can be varied within a framework, as will be understood by the person skilled in the art, to achieve the same results. Equivalent reaction components can be used within the specified ranges.

Additives that are commonly used in the rubber mixing technique can be added to the rubber mixes according to the invention and include accelerators, antioxidants, bactericides and the like, color pigments, extenders, strengthening pigments, plasticizers, vulcanizing agents, etc. The mixing ingredients are added in quantities necessary to achieve the desired properties in the resulting vulcanizate as is well known to the person skilled in the art.

The rubber mixture used in the present invention can be applied by means of calendering devices, spraying devices or other known application methods. Significant areas of application include but are not limited to radiator hoses, pneumatic wheel tyres, air springs, metal-reinforced products such as e.g. rubber fenders and sporting goods such as e.g. golf club handle.

In each of these representative areas of use, the rubber mixture can be used to increase adhesion and adhesion-retention properties between metal and rubber, including applications where there are shiny steel surfaces.

When the metal-reinforced laminate is included, e.g. in the construction of tires with steel cords, it is absolutely necessary both in the construction of new tires and track laying or repairs that the bond between the rubber - the mixture and the thread-textile is as flexible and strong as possible for efficient use under operating conditions. This is particularly important in the case of lorry tires which are exposed to high loads and speeds with the resulting heat build-up due to rapid bending of the layers.

The invention can also find application in e.g. metal-rubber items such as engine mounts, bearings, torsion-elastic springs, drive belts, pressure rollers, metal wire for strong or woven stocking, electric de-icers, shoe heels and wherever it is desired to attach rubber to coated or uncoated metal to provide a flexible and strong joint between these components .

Usable results are obtained by using brass or zinc-coated steel wire instead of the bare steel wire in Tables I and II. The coated thread when practicing the invention can e.g. be brass-coated wire, i.e. 70% Cu, 30% Zn, zinc-coated or bright (non-coated) steel wire. The thread can be in the form of a thread bundle, mat,

web, layer or weave.

Claims (1)

Metal-reinforced rubber laminate where the rubber part has improved adhesion to a metal part in contact with the rubber mixture which contains a significant proportion of natural rubber or mixtures of natural rubber and butadiene rubber, characterized in that it contains 0.5 to 8.0 parts cobalt and/or nickel salt of p- amino-benzoic acid per 100 pieces of rubber.