CZ306283B6 - Treatment method of reinforcing wire for increasing adhesion of elastomeric mixture - Google Patents

Abstract

The present invention relates to a surface treatment method of a reinforcing wire particularly that of tire bead reinforcement, in order to enhance adhesion of the elastomeric mixture. The treatment is realized without need to apply chemicals acting as adhesion promoters.

Description

Method of modifying a reinforcing wire to increase the adhesion of an elastomeric mixture

Field of technology

The invention relates to a method of modifying a reinforcing wire, in particular a tire bead reinforcement, to increase the adhesion of an elastomeric mixture. It is a treatment without the need to apply chemicals that act as adhesion promoters.

Prior art

At present, in addition to modifications of the reinforcing materials to increase the adhesion of the elastomeric mixture by various adhesion promoters, combinations of these substances with an ionized atmosphere treatment are also known. For example, U.S. Pat. No. 3,477,902 addresses the treatment of a reinforcing fabric in a discharge ionized gas atmosphere followed by the application of resorcinol-formaldehyde latex (RFL) as an adhesion promoter. Similarly, in the solution according to European patent application EP 1 109 669 (or the analogous patent U.S. Pat. No. 6,096,156), the fabric is first treated with a plasma with a dispersed vinyl compound and then a resorcinol-formaldehyde latex (RFL) adhesion promoter is applied.

A series of other patents use a process consisting of spraying the fabric, resp. The elastomeric mixture to modify the reinforcing cords to increase the adhesion of the elastomeric mixture. mixtures of adhesion promoters, the subsequent generation of plasma from the atomized mixture and the exposure of the reinforcing cords to this plasma at atmospheric pressure. In European patent application EP 2 716 695 (or analogous patent application US 2014/099 463), atmospheric plasma from a dispersed (atomized) mixture of hydrocarbon sulfide + solvent acts on the cord. In European patent application EP 2 371 882 (analogous patent US 8 445 074 and analogous patent applications US 2011/241269 and 2014/072741) the cord for increasing the adhesion of the rubber compound is treated by the action of atmospheric plasma from a dispersed mixture of monomer + halogenated hydrocarbon. In the solution according to European patent application EP 2 716 694 (or patent application US 2014/099460), the cord is in turn treated with an atmospheric plasma from a dispersed mixture of halogenated hydrocarbon + sulfide or monomer hydrocarbon.

The essence of the invention

A method of treating a reinforcing wire, in particular for tire beads, to increase the adhesion of an elastomeric mixture without the need for chemicals acting as adhesion promoters, subjecting the wire surface to pre-treatment by cleaning and activation by ionizing atmosphere, atmospheric plasma.

The atmospheric pressure plasma technology used for the pretreatment is preferably based on a diffuse coupling of a surface barrier discharge. This discharge has an optimum power of 250 to 800 W and is applied optimally for 1 to 20 s. Pretreatment by atmospheric pressure plasma technology based on diffusion coupling of the surface barrier discharge is preferably carried out continuously.

Preferred applications of the reinforcing wire surface-treated according to the invention are the production of rubber ropes for automobile tires and reinforcements for conveyor belts.

Plasma is, like a corona discharge, an electrical ionization of a gas. Atmospheric plasma heat discharge creates a smooth, undifferentiated cloud of ionized gas without visible electrical fibers. Unlike the corona, plasma is formed at much lower voltage levels. Gases or mixtures

-1 CZ 306283 B6 gases used for plasma surface treatment may contain air, nitrogen, argon, oxygen, nitrous oxide, helium, carbon dioxide, methane, ammonia and other gases. Each gas produces a unique plasma composition and leads to different surface properties. For example, surface energy can be increased very rapidly and efficiently by plasma-induced oxidation, nitration or hydrolysis.

The interaction of atmospheric plasma with the surface of the substrates causes several effects, each of which affects the resulting adhesion process. These effects can be, for example (but not limited to) the following: etching (surface bombardment with energetic particles, eg free radicals, electrons or ions), cleaning from organic impurities, change of chemical properties on the surface.

During surface bombardment with energetic particles, eg free radicals, electrons or ions, the covalent bonds of organic molecules are broken from surface contamination or oxidation products on the metal surface. As far as free radical scavengers are not present, bonds are formed with the surrounding free radicals. The depth of micro-etching of the surface by atmospheric plasma is usually around 40 to 60 nm and thus there is no change in the properties in the mass of the material, but only a significant increase in surface adhesion.

Surface contamination with organic substances in the form of low molecular weight organic substances is the most common problem that prevents adequate surface adhesion. These contaminations exist in the form of residues of processing aids and other organic compounds.

The change in chemical properties on the surface of the substrate caused by the action of free radicals gives the possibility of the formation of polar functional groups and the subsequent formation of strong covalent bonds between the metal surface and the deposit layer formed by the rubber mixture.

To generate a low temperature plasma, a type of diffuse coplanar surface barrier discharge that burns in a normal working gas at atmospheric pressure is preferred. The discharge even burns in strongly electronegative gases, such as oxygen, and does not need to be stabilized by helium or other noble gases.

The diffuse coplanar surface barrier discharge generates a macroscopically homogeneous plasma only in a thin layer above the surface of the lamp (0.3 mm) with a high energy density. This type of discharge is therefore suitable for surface modification of smooth materials. A substantial part of the power is directly used for plasma processing. This allows a short machining time and allows the use of a diffuse coplanar surface barrier discharge directly in production lines operating in the so-called "in line" mode.

Explanation of drawings

To further elucidate the essence of the invention, the accompanying drawings serve, where Fig. 1 - peel strength of the deposition layer of unvulcanized rubber mixture (initial adhesion) on the time of plasma exposure of steel substrate, Fig. 2 - dependence of steel substrate wetting angle with plasma on plasma exposure time. , Fig. 3 - dependence of surface energy (surface contact angle) of steel substrate on water on plasma exposure time, Fig. 4 - XPS Cis spectrum of steel surface layer depending on plasma exposure time, Fig. 5 - XPS Ol with spectrum of steel surface layer in depending on the plasma exposure time.

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Examples of embodiments of the invention

Example 1

To verify the effectiveness of the solution according to the invention, a model experiment was carried out with carbon steel plates of the same composition as the steel wire used for the production of the tire bead reinforcement. Prior to plasma exposure, the plates were surface cleaned in acetone and subsequently subjected to a diffuse coplanar surface barrier discharge at a distance of 0.3 mm. The surface exposure lasted from 0 to 8 s at a power of 350 W / s.

This was followed by a combination with a deposited rubber mixture based on natural rubber (NR 1 or NR 2 mixture), which was placed on a support consisting of a 1 mm thick rubberized polyester fabric, the semi-finished product being preheated together to 90 ° C in a hot air oven. This was followed by the actual connection to a surface-treated metal plate and pressing at a pressure of 10 MPa for 10 s. The stated parameters were close to the process in the extrusion head during rubberizing on an extrusion line.

The initial adhesion was evaluated by measuring the peel strength of the deposit layer of raw rubber compound from the metal surface. The measured dependences of the peel strength of the deposit layer on the exposure time during plasma treatment of the steel surface are shown in Fig. 1. The initial strength increases with the exposure time in diffuse wobbling of the surface barrier discharge and reaches the maximum value at exposure time 6 s.

Example 2

The surface polarity of steel plates exposed from 0 to 14 s at a power of 400 W / s in a diffuse wobble surface barrier discharge at a distance of 0.3 mm was evaluated by measuring the wetting angle on a SEE (Surface Energy Evaluation) - a system from Advex Instruments s.r.o. according to ISO 27448: 2009. The SEE system uses a CCD chip to record the profile of the microdroplet (with a volume of approx. 2 to 4 μΐ) and then the wetting angle is determined using the appropriate software.

From the measured values (see Fig. 2) it is evident that the angle of wetting with water reaches its minimum at an exposure time of 6 s, which is also in accordance with the measurement of the surface energy value.

Example 3

The surface energy of steel plates exposed from 0 to 14 s at a power of 400 W / s in a diffuse wobble surface barrier discharge at a distance of 0.3 mm was evaluated on the basis of measured contact angles of the test material and test liquids (water, iodomethane) on SEE ( Surface Energy Evaluation) System with System for Surface Energy Measurement software from Advex Instruments sro

From the measured values (see Fig. 3) it is clear that the surface energy reaches its maximum at the exposure time 6, which is in accordance with the measurement of the surface polarity (values of the wetting angle with water).

Example 4

The X-ray method was used to determine the composition of the surface layer of oxidation reaction products on the surface of carbon steel after exposure in a diffuse burst surface barrier discharge.

-3 CZ 306283 B6 spectral analysis (XPS - X ray photoelectron microscopy) using a PHI 5000 VersaProbe instrument manufactured by ULVAC-PHI jsc Japan. Samples of steel plates were exposed for 0 to 12 s at a power of 350 W / s. The measurement of the X-ray spectral analysis spectra was performed at a pressure in the measuring chamber of 7.9χ 10 ^-8 Pa and a measurement angle of 45 deg.

The measured Cis and Ols spectra of the surface oxidation layer are shown in Fig. 4 and Fig. 5. The composition in atomic percentages is shown in Tab. 1. As the plasma exposure time increases, the oxygen content of the layer on the metal surface increases, which is associated with the formation of hydroxyl, aldehyde, hydroperoxide groups with the highest value at the exposure time of 6 s, which is consistent with surface energy measurements. time of maximum value.

At the same time, at this exposure time, the lowest values of the water wetting angle on the metal surface and the maximum values of the initial adhesion of the coated rubber mixture to the steel surface of the test plates were reached.

Table 1: Composition of the surface layer of steel as a function of the time of plasma exposure, converted to carbon and oxygen

Plasma treatment time [s] Atom. Γ% 1 C O 0 74.6 25.4 2 72.8 27.2 4 55.6 44.4 6 45.5 54.5 8 45.6 54.4 10 48.4 51.6 12 54.4 45.6

PATENT CLAIMS

Claims (5)

PATENT CLAIMS 1. A method of treating a reinforcing wire, in particular for tire beads, to increase the adhesion of an elastomeric composition without the need for chemicals acting as adhesion promoters, characterized in that the wire surface is pretreated by cleaning and activation by tilting before applying the elastomeric composition. atmospheric plasma for 1 to 20 s. The method according to claim 1, characterized in that the plasma technology used in the pretreatment at atmospheric pressure is based on a diffuse coupling of a surface barrier discharge with a power of 250 to 800 W. Method according to one of Claims 1 and 2, characterized in that the pretreatment by atmospheric pressure plasma technology based on a diffuse coplanar surface barrier discharge takes place continuously. Car tire casing, characterized in that it comprises in the bead ropes a reinforcing wire surface-treated according to one of claims 1 to 3. -4CZ 306283 B6 Conveyor belt, characterized in that it comprises a reinforcing wire surface-treated according to one of claims 1 to 3.