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EP-3543177-B1 - ADHESION AGING PROTECTION IN STEEL CORDED RUBBER ARTICLES USING ZINC OXIDE

EP3543177B1EP 3543177 B1EP3543177 B1EP 3543177B1EP-3543177-B1

Inventors

  • HENNING, KATJA
  • MAGUIRE, DAVID J.

Dates

Publication Date
20260513
Application Date
20190221

Claims (10)

  1. A conveyor belt (1) which is comprised of a carry cover layer (2), a reinforcement layer (4) which is situated below the carry cover layer (2), and a pulley cover layer (7) which is situated below the reinforcement layer (4), wherein the reinforcement layer (4) is comprised of steel cordage (6) and rubber matrix (8), wherein the steel cordage (6) comprised in reinforcement layer (4) are zinc coated steel cords; and, characterized in that the rubber matrix (8) comprises zinc oxide in an amount of 11 phr to 16 phr.
  2. The conveyor belt (1) according to any of the preceding claims, wherein the rubber matrix (8) comprises zinc oxide in an amount of 16 phr.
  3. The conveyor belt (1) according to any of the preceding claims, wherein the carry cover layer (2) comprises at least one rubbery polymer selected from the group consisting of styrene-butadiene rubber, synthetic polyisoprene rubber, nitrile rubber, isoprene-butadiene rubber, polybutadiene rubber, styrene-isoprene-butadiene rubber, chloroprene rubber and ethylene-propylene-diene rubber.
  4. The conveyor belt (1) according to any of the preceding claims, wherein the pulley cover layer (7) comprises at least one rubbery polymer selected from the group consisting of styrene-butadiene rubber, synthetic polyisoprene rubber, nitrile rubber, isoprene-butadiene rubber, polybutadiene rubber, styrene-isoprene-butadiene rubber, chloroprene rubber and ethylene-propylene-diene rubber.
  5. The conveyor belt (1) according to any of the preceding claims, wherein the rubber matrix (8) comprises at least one rubbery polymer selected from the group consisting of styrene-butadiene rubber, synthetic polyisoprene rubber, nitrile rubber, isoprene-butadiene rubber, polybutadiene rubber, styrene-isoprene-butadiene rubber, chloroprene rubber and ethylene-propylene-diene rubber.
  6. The conveyor belt (1) according to any of the preceding claims, wherein the carry cover layer (2) includes zinc oxide at a level of greater than 5 phr.
  7. The conveyor belt (1) according to any of the preceding claims, wherein the pulley cover layer (7) includes zinc oxide at a level of greater than 5 phr.
  8. The conveyor belt (1) according to any of the preceding claims, wherein the carry cover layer (2) is devoid of lead oxide.
  9. The conveyor belt (1) according to any of the preceding claims, wherein the pulley cover layer (7) is devoid of lead oxide.
  10. The conveyor belt (1) according to any of the preceding claims, wherein the rubber matrix (8) is devoid of lead oxide.

Description

FIELD The field to which the disclosure relates is conveyor belts having zinc coated steel reinforcement cords therein. BACKGROUND Many rubber articles, such as conveyor belts, automobile tires, hoses, power train belts, e.g., transmission belts, and the like, are usually reinforced with fibrous or metal cords. In all such instances, the fiber or metal cord must be firmly bonded to the rubber. This is so whether the fiber or cord is a natural or synthetic polymer, or metallic, and whether the rubbers are natural or synthetic. Conventional conveyor belts which are used in heavy duty applications are typically comprised of a cured rubber or polyvinyl chloride (PVC) based material as a top layer, a cured rubber or PVC based material as a bottom layer, and one or more reinforcement layers (a carcass) disposed between the top layer and the bottom layer. The cured rubber or polyvinyl chloride based material may also serve to adhere various components of the reinforcing carcass. For example, individual layers and reinforcing elements included in the carcass may be encapsulated in a matrix of polymeric elastomeric resin, such as a polyvinylchloride based material. The individual layers are commonly saturated with the liquid elastomer-forming polymeric resin prior to being joined together, and the reinforcing elements may be inserted, for example, by tufting, sewing, or stitch-bonding. In cases where the liquid saturate is a polyvinylchloride plastisol, the resin is gelled, or otherwise cured, by application of heat. Some conveyor belts contain reinforcement elements which include zinc coated steel cords. Conveyor belts of these types can offer excellent performance characteristics and a relatively long service life. However, under some conditions where the conveyor belts are exposed to repeated high temperatures and/or humidity over long periods of time, the zinc coated steel cord reinforcements can delaminate, or otherwise lose adhesion, from the rubber matrix of the conveyor belt. For bonding the rubber to the zinc coated steel cord surface, special rubber formulations have been known to be used in the form of adhesion compounds. One solution to provide protection against aging/corrosion and loss of adhesion has been addition of lead oxide (PbO). However, PbO is considered a hazardous substance and is rated as SVHC substance in the REACH regulation, which could ultimately be banned for use. Also, currently available alternative compounds without PbO can achieve good adhesion to the cord surface, but the generated bonding is more susceptible to aging/corrosion than with compounds containing PbO. The document US 3 221 869 A discloses conveyor belts with embedded rubber layers comprising metal cables and 5 phr zinc oxide. Thus, there is an ongoing need for conveyor belts including zinc coated steel cordage with improved bonding between the zinc coated steel cord surface and rubber matrix, while be exposed to thermal and/or humidity aging conditions, such need met, at least in part, with embodiments according to the following disclosure. SUMMARY In a first aspect of the disclosure, a conveyor belt includes a carry cover layer, a reinforcement layer which is situated below the carry cover layer, and a pulley cover layer which is situated below the reinforcement layer, where the reinforcement layer has steel cordage and rubber matrix, wherein the steel cordage comprised in the reinforcement layer are zinc coated steel cords, and wherein the rubber matrix includes zinc oxide in an amount of 11 phr to 16 phr. In some cases the rubber matrix includes zinc oxide in an amount of 16 phr. BRIEF DESCRIPTION OF THE DRAWINGS Certain embodiments of the disclosure will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. FIG. 1 is a cross-sectional view of a conveyor belt having a carry cover layer, a reinforcement layer which is situated below the carry cover layer, where the reinforcement layer includes steel reinforcing elements, and a pulley cover layer which is situated below the reinforcement layer, according to an embodiment of the disclosure;FIG. 2 is a cross-sectional view of a conveyor belt having a carry cover layer, a reinforcement layer which is situated below the carry cover layer, where the reinforcement layer includes three layers of reinforcements, and a pulley cover layer which is situated below the reinforcement layer, according to another embodiment of the disclosure.FIG. 3 is a cross-sectional view of a conveyor belt having a carry cover layer, a second layer in the cover, which is situated immediately below the carry cover layer, a reinforcement layer which is situated below the cover, and a pulley cover layer which is situated below the reinforcement layer, according to another embodiment of the disclosure; and,FIG. 4 is a cross-sectional view of a conveyor belt having a carry cover layer, a second layer in the cover, which is situated imme