CS250838B1 - High adhesion rubber compounds to galvanized or brass surface - Google Patents

Abstract

The subject of the solution are special rubber mixtures, which allow to achieve high adhesion to galvanized or brass-plated reinforcing material after vulcanization at elevated temperatures. The mixtures are prepared on the basis of natural, butadiene, styrene-butadiene, isoprene rubber or their combination and, in addition to vulcanization additives, fillers and other common rubber raw materials, contain a solution consisting of cobalt 2-ethylhexanoate, mineral oil and chlorinated hydrocarbon and enable adhesion in the rubber-metal system to be ensured. The solution can be used for the production of conveyor belts with steel ropes, tires with steel cord, or for the production of other rubber products that are reinforced with galvanized or brass-plated reinforcing materials.

Description

The subject of the invention are rubber mixtures based on elastomers such as natural, butadiene, butadiene-styrene, isoprene and their mutual combinations, ensuring high strength of the mixture's connection with galvanized steel ropes or with brass-plated steel cords.

Rubber products such as conveyor belts with steel cords, tires with steel cords, hoses with metal braids, etc. are currently reinforced with galvanized steel cords or brass-plated steel cords. The basic requirement for the application of these reinforcing elements is to ensure a perfect connection of the rubber mixture with the metal reinforcement after vulcanization of the product, without which it would not be possible to ensure its functional properties at the required technical level. For this reason, cobalt complex compounds of branched organic acids with a chain of 4 to 14 carbon atoms, most often 8 to 12 carbon atoms, are mixed into these special mixtures, for example according to patents USSR 107 337, CA 1 024 835, BE 876 349, JA 4 052 188, NDR 50 302, NDR 50 303, and the rubber mixtures modified in this way, after vulcanization onto the reinforcing material, ensure the connection of the rubber-metal system.

In practice, these cobalt adhesive preparations are usually modified with ions, resins or latexes in order to achieve the highest adhesive effects and reduce the degradation effect of the cobalt complex compound. In particular, the issue of degradation effects is carefully monitored and often decides on the use of a specific cobalt additive. Another serious problem is the perfect dispersion of the cobalt additive in the rubber mixture, which then fundamentally affects the level of adhesion achieved. In the case of cobalt complex compounds in branched organic acids, the problem of perfect mixing into the rubber mixture is even greater and more serious. When mixing these preparations, the shear stress in the expanded areas of the mixing chamber is significantly reduced due to their dosage, which results in an extension of the mixing time and places increased demands on additional homogenization of the rubber mixture. Other disadvantages include the composition of cobalt compounds, since a significant part of it consists of a branched organic acid, which acts as an effective plasticizer in the mixture after its vulcanization. It is known from experimental work that plasticizers in adhesive types of mixtures have a negative effect on adhesion values and on the physical properties of rubber. In addition, for mixing fillers and other additives, it is necessary to dose additional plasticizers into these mixtures, most often in the form of oils and resins, which further increases these negative effects of organic acids. For these reasons, cobalt adhesive additives based on so-called naphthenic acids are dosed as little as possible, which is often in conflict with the requirement to achieve maximum adhesion values in the case of their higher dosage.

The above disadvantages and shortcomings are eliminated or partially mitigated by using rubber mixtures based on natural, butadiene, butadiene-styrene, isoprene rubber or their combination with high adhesion to galvanized or brass-plated surfaces, containing per 100 parts by weight of rubber 1 to 7 parts by weight of a solution consisting of 40% to 60% by weight of cobalt 2-ethylhexanoate, 40% to 60% by weight of mineral oil and 1% to 5% by weight of chlorinated hydrocarbon. After mixing, the rubber mixture is vulcanized at elevated temperature onto galvanized steel rope or brass-plated steel cord, thereby achieving high cohesion between the rubber and the metal reinforcing material.

In experimental work and practical tests, solutions of 2-ethylhexanoate in mineral bearing oils of type B2, J3 and J4 proved to be the best, provided that the solution contained around 50% by weight of cobalt 2-ethylhexanoate, 48% of mineral oil of type B2 and 2% of chlorinated hydrocarbon, preferably perchloroethylene, which, due to its polarity, activates the adhesive effects of the cobalt compound and also acts as a stabilizer.

When using rubber mixtures according to the invention, higher adhesion values are achieved, which is reflected in higher values of resistance to tearing of metal reinforcing materials from test specimens or products. Furthermore, the solution mentioned above allows for a reduction in the dosage of plasticizers, mainly oils, while maintaining the required processing properties of the mixtures.

Also significant is the improved dispersibility into rubber mixtures, which in practice results in shorter mixing times and therefore higher productivity of the mixing equipment.

Specific embodiments of the invention are illustrated by the following examples of rubber mixture compositions.

Example 1

Adhesive rubber mixtures of the following composition were mixed in a rubber mixer:

Weight parts

mix with No. 1 mixture no. 2 mixture no. 3 Natural rubber 45.0 45.0 45.0 Styrene butadiene rubber 35.0 35.0 35.0 Butadiene rubber 20.0 20.0 20.0 Zinc oxide 20.0 20.0 20.0 Stearic acid 0.6 0.6 0.6 Antioxidant PBN 1.0 1.0 1.0 Antiozonant IP 1.5 1.5 1.5 HAF carbon black 40.0 40.0 40.0 Silicic acid 12.0 12.0 12.0 Aromatic oil 5.0 3.0 3.0 Lead oxide 80% 1.8 1.8 1.8 Naphthenate Co 10% 4.5 - - 2-Ethylhexanoate in oil 10% Co - 4.5 - 2-Ethylhexanoate in oil 7% Co - - 6.5 Sulfenamide accelerator 0.7 0.7 0.7 Ground sulfur 2.6 2.6 2.6

Test specimens were prepared from the above mixtures and galvanized steel ropes with a diameter of 5.94 mm at a temperature of 150 °C for determining adhesion according to DIN 22 131 using the DK 621.867.21:622.647.21 method. The following values of rope pull-out resistance were measured during tests on a tearing machine:

a) test specimens without thermal loading mixture no. 1 - average value 117 N.mm mixture no. 2 - average value 123 N.mm mixture no. 3 - average value 118 N.mm

b) test specimens after thermal loading at 140 °C for 150 minutes - decrease in values mixture no. 1 - average value 103 N.mm mixture no. 2 - average value 110 N.mm ¹ mixture no. 3 - average value 106 N.mm

Test specimens were also prepared from the mixtures for adhesion testing using the ASTM D 2229-75 method. Adhesion was determined on a brass-plated steel cord of construction 7x4x0.22+1 at a working length of 25 mm. The test specimens were vulcanized at a temperature of 150 °C for 30 minutes. The following cohesion values were measured in laboratory tests:

mixture no. 1 - average value 55 N.mm mixture no. 2 - average value 60 N.mm mixture no. 3 - average value 58 N.mm ^-1

AND

Example 2

The following mixtures were mixed in a rubber mixer:

Weight parts

Mixture No. 4 No. 5 No. 6 No. 7 No. 8 No. 9 No. 10 No. 11 Natural rubber 60.0 60.0 60.0 60.0 60.0 60.0 60.0 60.0 Styrene butadiene rubber 30.0 30.0 30.0 30.0 30.0 30.0 30.0 30.0 Isoprene rubber 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 Zinc oxide 18.0 18.0 18.0 18.0 18.0 18.0 18.0 18.0 Stearic acid 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 Antioxidant PBN 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Antiozonant IP 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 HAF carbon black 41.0 41.0 41.0 41.0 41.0 41.0 41.0 41.0 Silicic acid 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 Aromatic oil 5.0 5.0 5.0 5.0 3.0 3.0 3.0 3.0 Lead oxide 80% 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 Phenol-formaldehyde resin 5.0 5.0 - - 5.0 5.0 - - Resorcinol - - 2.0 2.0 - - 2.0 2.0 Hexamethylenetetramine 1.0 - 1.0 - 1.0 - 1.0 - Hexamethoxymethylmelamine - 2.5 - 2.5 - 2.5 - 2.5 Naphthaein Co 10% 4.5 4.5 4.5 4.5 - - - - 2-ethylhexanoate Co in oil with 8.5% cobalt content - - - 5.3 5.3 5.3 5.3 Sulfenamide accelerator 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 Ground sulfur 2.8 2.8 2.8 2.8 2.8 2.8 2.8 2.8

From the above mixtures and galvanized steel ropes with a diameter of 5.94 mm, test specimens were prepared at a vulcanization temperature of 150 °C for determining adhesion according to Dl 22 131 by method DK 621.867.21:622.647.21. The tests investigated the possibility of combining a solution of cobalt 2-ethylhexanoate in mineral oil with the addition of a chlorinated hydrocarbon with thermosetting resins based on phenol and resorcinol. The following values of resistance to rope tearing were measured from the test specimens during the tests:

mixture no. 4 - average value 125 N.mm ¹ mixture 6. 5 - average value 123 N.mm mixture no. 6 - average value 124 N.mm mixture no. 7 - average value 121 N.mm mixture no. 8 - average value 131 N.mm ¹ mixture no. 9 - average value 129 N.mm ¹ mixture no. 10 - average value 130 N.mm ³ mixture no. 11 - average value 128 N.mm

Example 3

Mixtures No. 1, 2 and 3 according to Example 1 were mixed in a laboratory mixer, with the exception that the cobalt adhesive additives, cobalt naphthenate 10% and cobalt 2-ethylhexanoate in mineral oil 10% Co, 7% Co were not dosed into the mixer. These additives were then mixed in a laboratory double-cylinder mixer, and the time required for their complete mixing into the mixtures was determined. The following times were measured:

for mixture no. 1 - 4.5 minutes for mixture no. 2 - 2.8 minutes for mixture no. 3 - 2.5 minutes

Furthermore, 5 samples were taken from random locations of the rubber honeycomb from the mixtures thus mixed and the Co content of the samples was determined, thereby determining the level of dispersion and homogeneity of the mixture. The following Co concentrations in % were found:

at mixtures p. 1 0.21 0.19 0.16 0.22 0.17 at mixtures No. 2 - 0.22 0.20 0.21 0.19 0.20 at mixtures e. 3 - 0.21 0.22 0.20 0.18 0.21

* In general, a wide range of other variations of these adhesive mixtures can be used, therefore the examples given should not be considered as limiting the scope of this invention.

The invention can be used in the production of conveyor belts with galvanized or brass-plated ropes, tires with brass-plated steel cord and hoses with brass-plated metal reinforcement.

Other rubber products that will be reinforced with galvanized or brass-plated materials are also being considered.

Claims (2)

SUBJECT OF THE INVENTION 1. Rubber mixtures having a high adhesion to a galvanized or brass-plated surface, based on natural, butadiene, butadiene-styrene rubber or combinations thereof, characterized in that they contain, per 100 parts by weight of rubber, 1 to 7 parts by weight of a solution composed of 40 to 60% by weight cobalt ethyl hexanoate, 40 to 60 wt.% mineral oil and 1 to 5 wt.% chlorinated hydrocarbon. 2. Rubber mixtures according to claim 1, characterized in that they contain a solution composed preferably of 50% by weight of cobalt 2-ethylhexanoate containing 16.5 to 17% by weight of cobalt metal, 48% by weight of mineral bearing oil and 2% by weight of perchlorethylene. .