CS232200B1 - A method of increasing the consistency of rubber products, especially hoses, with multi-layer reinforcement - Google Patents

Abstract

The invention solves the problem of increasing the cohesion of layers of rubber products, especially hoses, with multi-layer reinforcement. The previously known methods of increasing the cohesion between the reinforcement and the rubber use either reinforcement treatments - impregnation - or rubber mixture treatments. However, cohesion between individual layers of reinforcement cannot be achieved by treating the rubber mixture. Here, adhesives must be used, most often a coating of rubber cements in a volatile solvent, or rubber intermediate layers. However, these operations do not ensure the cohesion of the outer layers of the reinforcement with the rubber, which must be ensured by other operations (treatment of the substrate or rubber mixture). The methods used so far to ensure the overall cohesion of the products are therefore not sufficiently effective or are economically demanding. The problems are solved by the method according to the invention, where a reactive adhesive composition is applied between the layers of reinforcement, which penetrates to the rubber layers and, when reacted, ensures the overall cohesion of the product. The adhesive is prepared from a telechelic polymer with reactive functional groups and a diisocyanate or diepoxide, the resulting liquid prepolymer is mixed with an extender, crosslinker, catalyst, drying agent as required. The mixture is applied between the reinforcing layers of the product, which is vulcanized.

Description

The invention relates to a method of increasing the cohesion of layers of rubber products, in particular hoses, with multilayer reinforcement.

The requirements for the cohesion of the layers of high-pressure and low-pressure hoses have a decisive influence on the production technology. Low values of the cohesion of the layers of hoses reinforced with braids or windings of yarn strands or wires have an adverse effect on the quality of the final products. The cohesion of the rubber of the inner tube and the casing with untreated natural and synthetic reinforcements is particularly low.

To increase cohesion, pre-impregnated yarn, the application of rubber cement in a volatile solvent or an admixture to rubber mixtures, most often based on resorcinol-formaldehyde resins, is most often used on an operational scale, and according to the latest procedures, liquid oligomeric compositions, for example hydroxyl-terminated oligobutadiene with diisocyanate, are added to rubber mixtures.

With the exception of rubber cements, the above methods can ensure sufficient adhesion of rubber to both textile and wire, but not adhesion between two completely overlapping textile or wire wraps or braids. In this - very common - case, it is necessary to use either a double layer of cement or a rubber intermediate layer.

The use of a double cement coating in a volatile solvent has some disadvantages. The drying of the cements must be taken into account, which is a diffusion operation that requires time. The capture and regeneration of solvents are capital and energy-intensive. In addition, the labor

232 200 The environment when working with solvents does not meet current regulatory requirements.

If rubber interlayers are used, the rubber compound for this interlayer must be treated - with an adhesion-enhancing additive - or the reinforcement material - by impregnation. The strip of compound that is to act as the interlayer must be separated in the winding to prevent it from sticking together. This separation, often carried out by a slide, then impairs the cohesion of the final product.

From a technological point of view, producing a rubber band means an additional operation.

The previously known methods of increasing the cohesion of rubber products with multilayer reinforcement are therefore not sufficiently effective - cohesion of 3GC-10CG N/m is achieved - and/or they are economically demanding.

The above disadvantages are eliminated by the method of increasing the cohesion of the layers of rubber products with multilayer reinforcement according to the invention. The essence of the invention consists in preparing a liquid prepolymer from a telechelic polymer with reactive functional groups, for example hydroxyl, amine, mercaptan, or carboxyl, and diisocyanate or diepoxide, this prepolymer is optionally mixed with an extender, catalyst, drying agent or some combination of these substances, wherein the reactive functional groups, including reactive groups contained in textile fibers and impurities, especially water, are in a stoichiometric ratio, the obtained reactive adhesive composition is applied between the reinforcing layers of the product, which is then vulcanized.

If an extender ^is used, it is a diol, in particular 1,4-butanediol or ethanediol. The crosslinker is, for example, triethanolamine or glycerin.

If a catalyst is required, as is the case in most cases, other catalysts must be used for prepolymers formed by the reaction of hydroxyls, amines or mercaptans with diisocyanates - here dibutyltin laurate or triethylenediamine is used for catalysis - and other catalysts in the case of a reacting mixture of carboxylic compounds with epoxides - then the catalyst is quinoline or a chromium complex with fatty acids.

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When processing viscose fiber, it is necessary to take into account a significant moisture content of the material, which reaches 5-7% by weight. Water reacts at the vulcanization temperature with isocyanate groups, which are partially destroyed, and carbon dioxide is released at the same time, which can act between the impermeable rubber layers as a separator. This problem is solved by adding a drying agent - calcium oxide in the form of an oil paste to the mixture of the reacting prepolymer. It binds both water and carbon dioxide.

The application of the reactive adhesive composition according to the invention is limited by certain factors, both from a chemical and a physical point of view.

The adhesive composition is capable of further reactions at the moment of application, namely:

- with added extenders and crosslinkers - formation of a solid bonding mass

- with reactive groups of reinforcement material - cotton, viscose, polyamide

- with rubber compound - co-vulcanization.

From a physical point of view, the viscosity of the reactive adhesive composition is an important factor. The viscosity must be low enough to allow the adhesive to penetrate between the fibers (strands) of the reinforcement to the rubber layers. The adhesive is applied between the layers of reinforcement in such a way that a layer is formed on one reinforcement layer and this layer is covered by a second reinforcement layer. Therefore, it is advantageous to adjust the reaction rate and the associated increase in the viscosity of the adhesive so that the second reinforcement layer does not slip after being applied to the layer of adhesive and is well fixed.

For the preparation of adhesive compositions, telechelic polymers with reactive groups, with an average molecular weight of 800—8000 and an average number functionality of 1.3-2.3, based on butadiene and its copolymers and acrylonitrile, styrene, polyisoprene and its copolymers, polyethers and polyesters are used.

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Examples of raw materials used for the preparation of the adhesive composition and their dosage are given in Table I.

Table I

Mixture δ. Reactive M_ polymer RP parts per 100 wt.d.RP Diiso- cyanate extension cord 1. Polybutadiene 2100 termed hydroxyls 2.1 15-35 (MDI) 0 2. ^rM - 2400 1.3 5-15 (TDI) 0 3. - - 3300 2.3 12-25 (TDI) 0 4· - - 2100 2.1 15-35 (MDI) 0.2-6 (Buol) 5. - - 2100 2.1 15-35 (MDI) 0.1-4 (glycol) 6· - - 2100 2.1 17-30 (TDI) 0.2-8 (Buol) 7. - - 2100 2.1 17-30 (TDI) 5-80 (PPG) 8. copolymer 2400 styrene/butadiene term. hydroxyl 1.7 10-25 (TDI) 0 9. copolymer 3000 butadiene/acrylonitrile term, hydroxyls 2.1 12-30 (MDI) 0.1-4 (glycol) 10. polybutadiene 3500 terminated by mercapt ane groups 1.9 8-20 0.1—8 (Buol) 11. copolymer 3300 butadiene/acrylonitrile term. amine groups 1.8 8-20 (TDI) 0 12. Polycaprolac- 8000 tons 2 2-10 (TDI) ⁰ 13. Polypropylene- 2000 oxide term, hydroxyls 2 8-35 0 14. Polybutadiene 3000 termin. carboxyl groups 2.2 15-40 (Diepoxide) 0

• 'P232 200 where MDI - 4,4 diphenylmethanediisocyanate

TDI - mixture of 2,4 and 2,6 toluene diisocyanate Buol- 1,4 butanediol

Glycol -ethynediol

Epoxide - 4,4*diphenylisopropyldiglycidyl ether PPG - polypropylene oxide diol

The composition is prepared in a reactor into which the necessary components are dosed. A prepolymer is formed under stirring, which is either applied to the first reinforcing layer by itself or mixed immediately before application with an extender or crosslinker, such as low molecular weight diols, ethylene glycol, butanediol, triols, triethanolamine, epoxides, etc., and with a catalyst, such as triethylenediamine, dibutyltin laurate.

Since liquid polybutadienes terminated with hydroxyl are more economically demanding than, for example, liquid polyethers, it is possible to use mixtures of these two substances for the preparation of the prepolymer. In general, an increased content of polybutadienes or their copolymers increases the cohesion with rubber due to the double bonds contained and thus the possibility of co-vulcanization.

The produced prepolymer can be stored without access to air and moisture theoretically indefinitely, practically (in the reactor) for several months. The prepared reactive composition lasts for 5-15 minutes depending on the type, therefore it is prepared in a proportionally smaller amount, but also in a closed space, so that the operator does not come into contact with liquid toluene diisocyanate or its vapors.

Individual specific embodiments of the method according to the invention are described in the following examples.

Example 1 (mixture composition according to No. 13 in Table I)

10C parts by weight of polypropylene oxidediol according to No. 13 with 32 parts by weight of diphenylmethane diisocyanate at 90 C and with the addition of 8 parts of calcium oxide react to form a prepolymer. Just before application to the first textile wrap - viscose silk

232 200 are mixed with 3 parts of ethylene glycol with .2.6% triethylendiamine. The reacting hot layer (70 °C) solidifies and the second wrap is immediately placed in it. A rubber casing is formed in the crosshead of the extruder. This is followed by vulcanization at 150 °C in hot water. The mixture of the core and the casing was based on butadiene-styrene rubber.

Example 2 (mixture composition according to No. 4 and 13 in Table I) *

parts by weight of polypropylene oxidediol according to No. 13 and 20 parts by weight of liquid polybutadiene according to No. 4 with 32 parts by weight of diphenylmethane diisocyanate and 8 parts by weight of calcium oxide form a prepolymer at 90 ^° C, before application 4.5 parts by weight of butarylene glycol with 2 parts by weight of triethylenediamine are added. The procedure is the same as in Example 1.

Example 3 (mixture composition according to No. 4 in Table I)

100 parts by weight of polybutadiene according to No. 4 form at 70 °C with 30 parts by weight of diphenylmethane diisocyanate a prepolymer which is applied to a textile roll as in Example 1.

In Examples 1-3, rubber mixtures based on nutadiene-styrene rubber were used for both the inner tube and the casing.

Example 4 (mixture composition according to No. 14 in Table Ϊ)

100 parts by weight of liquid polybutane-diene-acrylonitrile rubber according to No. 14 with 16 parts by weight of epoxide-4,4-diphenylisopropyldiglycidyl ether - and with 4 parts by weight of quinoline are mixed just before application to the first layer of viscose rayon. A second winding is made into this coating and a rubber cover is placed.

In this case, a mixture of inner tube and casing based on butadiene acrylonitrile rubber was used. After steam vulcanization and aging, the cohesion between the textile layers and between the textile and rubber was measured.

Table II shows the cohesions of the individual layers as averages from three measurements.

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Table II

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Fr. Cohesion core-textile N/m Cohesion of packaging-textile N/m Cohesion textile-textile N/m 1 750 820 3,450 2 1,600 1,850 3,200 3 2,100 2,080 \ 2,700 4 1,800 1,800 2^300

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Claims (5)

Method for increasing the cohesion of rubber products, in particular hoses, with multilayer reinforcement, in particular bilayer textile or wire reinforcement, by means of a reactive adhesive composition, characterized in that of a telechelic polymer with reactive functional groups, for example hydroxyl, amine, mercaptan or carboxyl, of a diisocyanate or diepoxide, a liquid prepolymer is prepared, optionally mixed with an extender, a crosslinker, a catalyst, a drying agent or any combination thereof, wherein the reactive functional groups, including reactive groups contained in textile fibers and in impurities, especially water, are in stoichiometric ratio , the obtained reactive composition is applied between the reinforcing layers of the article, which is then vulcanized. Method according to claim 1, characterized in that the extender is a diol, in particular 1,4-butanediol or ethanediol. 3. The method of claim 1 wherein the crosslinker is triethanolamine or glycerin. 4. The process of claim 1 wherein the catalyst is dibutyltin laurate or triethylenediamine for hydroxyl, amine, mercaptan-diisocyanate-terminated telechelic polymer compositions, or quinoline or chromium fatty acid complex for telechelic-terminated telechelide polymer compositions. 5. The method according to claim 1, wherein the drying agent used in the case of non-dried textile reinforcement is, for example, calcium oxide.