CS241834B1 - Process for the preparation of powdery cobaltic salts of organic acids - Google Patents

Abstract

The method of preparing powdered cobalt salts of organic acids with a branched carbon chain consists in introducing, at elevated temperature and with constant stirring, icoloid silica into a solution of a cobalt salt of a branched fatty acid in mineral oil, and stirring is continued until a homogeneous mixture of powdery character is formed. The above procedure produces a product with a cobalt content of 2.5 to 6% by weight, which is dosed very well, does not dust during application, is easily dispersed into rubber mixtures and does not stick together or change its original properties during storage. It is intended primarily as an adhesive for bonding rubber with galvanized or brass-plated reinforcing materials, which are used in the production of conveyor belts with steel ropes, tires with brass-plated steel cord, or in other rubber products such as hoses and V-belts with metal reinforcement coated with zinc or brass.

Description

The invention relates to a method for preparing cobalt-containing organic acid compounds.

Cobalt compounds, especially salts with branched organic acids, are used in a number of technical sectors. Examples include their application in bonding rubber to zinc, galvanized or zinc-containing surfaces, in accelerating the drying process of oil paints, in curing unsaturated polyesters, epoxy resins, paints, etc.

Preferably, salts of branched fatty acids with a carbon chain containing 6 to 14 carbon atoms are used for these applications, such as 2-ethylhexanoic acid, 2,2-dimethyloctanoic acid, 2,4-diethyloctanoic acid. Cobalt salts of these acids exhibit a high viscosity in concentrated form, of the order of up to about 100 Pas at 20 °C. In this form, they are difficult to dose, weigh and mix. In particular, their mixing into rubber mixtures intended for bonding with metals is very difficult, as they significantly extend the mixing time, cause technological difficulties after the mixture is discharged from the kneader and are very difficult to disperse.

The final application form for rubber mixtures is loose powders or granulates. It is possible to prepare a powder form of cobalt salts of organic acids by the method according to AO No. 222 736. The principle of preparing a powder product consists in mixing a solution of cobalt salt in an organic solvent with colloidal silicon dioxide under certain specific conditions and removing the organic solvent from the resulting dispersion, thereby obtaining a powder form of cobalt complex salt.

The above-mentioned procedure is distinguished by its undemanding requirements for the intensity of mixing and the resulting homogeneity of the prepared product. A certain 'shortcoming of this' procedure is the considerable demand for equipping the production facility with a powerful evaporation and suction device with the unconditional use of a recovery unit for solvent recovery after its evaporation from the dispersion.

In practice, these requirements represent a special production line equipped with explosion-proof drive units and usually other difficulties associated with fire safety and hygiene regulations.

The above-mentioned shortcomings are eliminated by powdered cobalt salts prepared by the process according to the present invention. The essence of the preparation consists in gradually mixing colloidal silicon dioxide in a solution of a cobalt salt of a fatty acid with 6 to 14 carbon atoms in a branched carbon chain in mineral oil, containing 5 to 10% cobalt and 40 to 60% mineral oil, preferably at a temperature of 40 to 80°C, in a ratio of 5 parts by weight of solution to 3 to 5 parts by weight of colloidal silicon dioxide.

A particularly preferred embodiment consists in using as the cobalt salt a salt of 2-ethylhexanoic acid in a solution of mineral oil J3 or J4, the solution containing 7.5 to 9% cobalt and 45 to 5.5% mineral oil, and colloidal silicon dioxide is mixed into this solution in a ratio of 5 parts of solution to 3 to 4 parts of silicon dioxide.

A wide range of mineral oils can be used for the solution of cobalt complex salts of fatty acids, but in practice their selection is limited by quality considerations. These include, in particular, the flash point, which must be higher than the temperature in the mixing and vulcanizing equipment, and the effect of the oil on the adhesive properties of the cobalt binder.

Emphasis is also placed on the viscosity of the oil, which should range from 10 dio to 40 mui' ² /s at 50 °C. As regards the type of colloidal silica, satisfactory results have been achieved with precipitated silicic acids, the particle size of which ranged from 0.015 to 0.03 gm and the acidity from 6 to 7 pH degrees.

The mixing method used is of decisive importance for the final properties of the composition according to the present invention. It has been found that, for example, cobalt octoate or naphthenate with a dry matter content of about 95% by weight cannot produce a homogeneous mixture with colloidal silica even after several hours of kneading in a laboratory kneader.

Inhomogeneous lumps with different cobalt contents are formed, which is unacceptable for the precise dosing of the cobalt adhesive additive. Similarly, it was not possible to prepare homogeneous mixtures from highly concentrated solutions of other cobalt salts of organic acids. For perfect dispersion of the cobalt salt in the mass of powdered or colloidal silica, it is necessary to create a well-mixable dispersion, which is gradually thickened by further additions of colloidal silica until a powdered product is formed.

The formation of a well-mixable dispersion in the first phase of product preparation will be enabled by a solution of the cobalt salt of a fatty acid in mineral oil. Since diffusion processes are apparently used in the preparation, the mixing time, mixing intensity and mixing temperature are also important. When mixing in a mixing device equipped with profiled rotors that engage the cylindrical bottom of the mixing chamber, at a speed of 30 to 120 revolutions per minute as a proportion of the size of the mixing device and at a temperature of 50 to 60 °C, the mixture reaches its optimum properties in about 20 minutes.

According to principles known from the theory of mixing and diffusion processes, the necessary time can be shortened by more intensive mixing and using a higher working temperature.

The process according to the invention produces a purple or light purple powdery bulk material that disperses well in rubber materials.

With mixtures, it does not show the slightest degree of dustiness, does not caking when stored in closed containers and is stable during storage.

The preparation method according to the invention further enables the use of existing production equipment without the need for extraction, recovery of organic solvents and special fire and hygiene protection of the workplace.

The following examples illustrate the method of preparing the composition according to the invention.

Example 1

A solution containing 9% cobalt and 52% oil is prepared from the cobalt salt of 2-ethylhexanoic acid containing 16.8% cobalt by weight and mineral bearing oil J3. 3.5% silicon dioxide is added to 5 parts by weight of this solution with constant stirring.

Intensive mixing at 80 rpm, temperature 60 °C, for 15 minutes produces a purple powdery product containing approximately 4.8% cobalt. The properties of the product did not change after storage for 6 months in a closed container.

Example 2

A solution in mineral bearing oil J4 is prepared from the cobalt salt of 2-ethylhexanoic acid containing 16.8% cobalt. The solution contains 8.2% cobalt and 48% oil. 3 parts by weight of colloidal silicon dioxide are gradually mixed into 5 parts by weight of this solution at a temperature of 80 °C.

Intensive mixing at 60 rpm for 20 minutes yields a purple powder product containing approximately 5% cobalt. The product does not create dust when applied and does not caking or change its properties after storage in a closed container for 6 months.

Example 3

5 parts of colloidal silicon dioxide are gradually mixed into 5 parts by weight of the cobalt salt of a fatty acid in mineral oil according to Example 1 at a temperature of 50 °C and a rotor speed of 80 per minute. After mixing and complete dispersion, a light violet powder product containing 4.5% cobalt is obtained. The preparation does not dust during handling and does not caking or change its original properties after storage in a closed container for 6 months.

The powdered icobalt salts prepared according to the invention can be used in the bonding of rubber mixtures with zinc, galvanized and/or zinc-containing surfaces by vulcanization at elevated temperatures. Exemplary embodiments of the application of powdered icobalt salts to adhesive rubber mixtures are documented in the following examples.

Example 4

A mixture of natural and styrene-butadiene rubber with the following composition was mixed in a laboratory mixer:

mass parts natural rubber, RSS I 60.0 styrene butadiene rubber 40.0 zinc oxide 20.0 stearic acid 0.7 antioxidant 1.5 soot· HAF 60.0 aromatic oil 4.0 lead oxide 1.5 sulfenamide accelerator 0.7 ground sulfur 2.5

The mixture was mixed in a larger quantity and divided into 6 equal parts by weight. Into each of these parts was added a powdered salt of 2-ethylhexanoic acid with a cobalt content of 5%, prepared according to Example 2. The powdered salt was added in the following quantity:

mixture no. 1 mixture no. 2 mixture no. 3 parts by weight mixture no. 4 parts by weight mixture no. 5 parts by weight mixture no. 6 parts by weight parts by weight 12 parts by weight

Test specimens were prepared from these rubber mixtures and galvanized steel ropes with a diameter of 5.94 mm at a temperature of 145 °C for determining adhesion using the method according to mixture no. 1 34 N. mm' ¹ mixture no. 2 68 N. mm ^-1 mixture no. 3 87 N. mm ^-1

DIN 22131 (DK 621.867.21:622.647.21]. During the tear tests, the following average values of resistance to tearing were measured:

on the rubber test sample: mixture no. 4 1115 N. mm" ¹ mixture no. 5 118 N. mm ^-1 mixture no. 6 116 N. mm" ¹

Example 5

A base mixture of the following composition was mixed from natural rubber:

material parts

natural rubber, RSS I 100.0 stearic acid 0.5 zinc oxide 10.0 aromatic oil 12.0 HAF carbon black 60.0 antioxidant 2.0 mixture no. 1 0 mass parts mixture no. 2 1 mass work mixture no. 3 2 mass parts

From the above mixtures and from a brass-plated steel cord of construction 7 x 4 X 0.2.2 -j+1, test specimens were prepared for adhesion testing by the AST.MD 2 2.29—75 method. The samples were vulcanized at a temperature of 145 mixture no. 1 35 N . mm ¹ mixture no. 2 15 N . mm ¹ mixture no. 3 40 N . mm ¹ parts by weight silicic acid '6.0 sulfenamide accelerator '0.8 sulfur N 4.0

The mixture was mixed in a larger quantity and divided into 6 equal parts by weight. The powdered salt of 2-ethylhexanoic acid with a cobalt content of 4.8%, prepared according to example 1, was then mixed into the individual parts of the base. The powdered salt was mixed in the following quantities:

mixture no. 4 ,3 parts by weight mixture no. 5 4 parts by weight mixture no. 6 5 parts by weight degrees C for 35 minutes. Adhesion was monitored at a working length of 25 mm. During the tear tests, the following values of resistance to pulling out of the brass-plated ‘cord’ from the test sample were found:

mixture no. 4 54 N . mm ^-1 mixture no. 5 53 N . mm ¹ mixture no. 6 51 N . mm ^-1

In practice, powdered cobalt salts can be used in the production of conveyor belts with galvanized steel ropes and tires with brass-plated steel cord. In these products, high adhesion between the reinforcing material and the rubber mixture of the product must be ensured, which can be ensured by applying the powdered product according to the invention.

Claims (2)

печет 1. A process for the preparation of powdered cobalt organic acid salts, characterized in that, in a mineral oil containing from 5 to 10% by weight, a solution of a co-ballasted salt of an organic acid of 6 to 14 carbon atoms in a branched carbon chain. % cobalt and 40 to 60 wt. The mineral oil is mixed, preferably at a temperature of 40 to 80 ° C, with 5% by weight of colloidal silicon dioxide. parts of the solution to 3 to 5 parts by weight of silica. OF THE INVENTION 2. A process according to claim 1, wherein the salt of 2-ethylhexanoic acid in a p-arafinic-type mineral oil solution is preferably used as the asbaltate salt, wherein the solution contains from 7.5 to 9% by weight of the composition. . % cobalt and 45 to 55 wt. of colloidal silicon dioxide in a ratio of 5 wt. parts of the solution to 3 to 4 wt. parts of silica. Severography, n, p., Plant 7, Most