Metal Cord, Rubber-Cord Complex and Pneumatic Tire Using the Same

Abstract

A rubber-cord complex having an improved wet heat adhesive property between a rubber and a cord comprising a drawn plated wire, and including a metal cord comprising a drawn plated wire prepared by providing a brass plated layer on the surface of an element wire and drawing the resulting plated wire, and a rubber vulcanized and bonded to the cord, wherein in a wet heat deterioration state of the drawn plated wire after being subjected to the vulcanization to bond the rubber thereto and further held under an atmosphere having a temperature of 50 to 100° C. and a humidity of 60 to 100% for one hour to 20 days, the average grain size of crystal grains present in the brass plated layer is not more than 50 nm, and the grain boundary of the crystal grains has a fractal dimension of 1.001 to 1.500.

1 . A rubber-cord complex obtained by vulcanizing and bonding a rubber to a metal cord comprising a drawn plated wire prepared by providing a brass plated layer containing copper and zinc on the surface of a metal wire and drawing the resulting plated wire, wherein in the wet heat deterioration state of the metal cord to which the rubber has been vulcanized and bonded and which has been held in an atmosphere having a temperature of 50 to 100° C. and a humidity of 60 to 100% for one hour to 20 days, the average grain size of crystal grains present in the brass plated layer is not more than 50 nm, and the grain boundary of the crystal grains has a fractal dimension of 1.001 to 1.500. 
   
   
       2 . The rubber-cord complex of  claim 1 , wherein the brass plated layer contains 0.1 to 5.0 parts by weight of cobalt or 1.0 to 10.0 parts by weight of nickel per 100 parts by weight of the plating. 
   
   
       3 . The rubber-cord complex of  claim 1 , wherein the rubber has, on the interface with the brass plated layer, an adhesion reaction layer formed by cross-linking reaction between sulfur in the rubber and copper in the brass plated layer, and in the wet heat deterioration state, the average thickness of the adhesion reaction layer is from 50 to 1,000 nm. 
   
   
       4 . The rubber-cord complex of  claim 1 , wherein the brass plated layer is formed by thermal diffusion of a copper plated layer and a zinc plated layer formed in layers on the metal wire, in which the copper plated layer is formed by plating at a current density of 15 to 25 A/dm 2 , the zinc plated layer is formed by plating at a current density of 40 to 60 A/dm 2 , and the thermal diffusion is conducted by a low temperature diffusion at a temperature of 500 to 550° C. 
   
   
       5 . The rubber-cord complex of  claim 1 , wherein the metal cord comprises at least one said drawn plated wire. 
   
   
       6 . A metal cord for use in the rubber-cord complex according to  claim 1 , wherein the brass plated layer is formed by thermal diffusion of a copper plated layer and a zinc plated layer formed by plating in layers on the metal wire, in which the copper plated layer is formed by plating at a current density of 15 to 25 A/dm 2 , the zinc plated layer is formed by plating at a current density of 40 to 60 A/dm 2 , and the thermal diffusion is conducted by a low temperature diffusion at a temperature of 500 to 550° C. 
   
   
       7 . A metal cord for use in the rubber-cord complex according to  claim 1 , wherein the brass plated layer is formed by thermal diffusion of a copper plated layer and a plated layer of a zinc alloy selected from a zinc-nickel alloy and a zinc-cobalt alloy, the layers being formed in layers on the metal wire, in which the copper plated layer is formed by plating at a current density of 15 to 25 A/dm 2 , the zinc alloy plated layer is formed by plating at a current density of 40 to 60 A/dm 2 , and the thermal diffusion is conducted by a low temperature diffusion at a temperature of 500 to 550° C. 
   
   
       8 . A pneumatic tire in which the rubber-cord complex according to  claim 1  is used as a ply for tire reinforcement. 
   
   
       9 . The rubber-cord complex of  claim 2 , wherein the rubber has, on the interface with the brass plated layer, an adhesion reaction layer formed by cross-linking reaction between sulfur in the rubber and copper in the brass plated layer, and in the wet heat deterioration state, the average thickness of the adhesion reaction layer is from 50 to 1,000 nm. 
   
   
       10 . The rubber-cord complex of  claim 2 , wherein the brass plated layer is formed by thermal diffusion of a copper plated layer and a zinc plated layer formed in layers on the metal wire, in which the copper plated layer is formed by plating at a current density of 15 to 25 A/dm 2 , the zinc plated layer is formed by plating at a current density of 40 to 60 A/dm 2 , and the thermal diffusion is conducted by a low temperature diffusion at a temperature of 500 to 550° C. 
   
   
       11 . The rubber-cord complex of  claim 3 , wherein the brass plated layer is formed by thermal diffusion of a copper plated layer and a zinc plated layer formed in layers on the metal wire, in which the copper plated layer is formed by plating at a current density of 15 to 25 A/dm 2 , the zinc plated layer is formed by plating at a current density of 40 to 60 A/dm 2 , and the thermal diffusion is conducted by a low temperature diffusion at a temperature of 500 to 550° C. 
   
   
       12 . The rubber-cord complex of  claim 2 , wherein the metal cord comprises at least one said drawn plated wire. 
   
   
       13 . The rubber-cord complex of  claim 3 , wherein the metal cord comprises at least one said drawn plated wire. 
   
   
       14 . The rubber-cord complex of  claim 4 , wherein the metal cord comprises at least one said drawn plated wire. 
   
   
       15 . A metal cord for use in the rubber-cord complex according to  claim 2 , wherein the brass plated layer is formed by thermal diffusion of a copper plated layer and a zinc plated layer formed by plating in layers on the metal wire, in which the copper plated layer is formed by plating at a current density of 15 to 25 A/dm 2 , the zinc plated layer is formed by plating at a current density of 40 to 60 A/dm 2 , and the thermal diffusion is conducted by a low temperature diffusion at a temperature of 500 to 550° C. 
   
   
       16 . A metal cord for use in the rubber-cord complex according to  claim 3 , wherein the brass plated layer is formed by thermal diffusion of a copper plated layer and a zinc plated layer formed by plating in layers on the metal wire, in which the copper plated layer is formed by plating at a current density of 15 to 25 A/dm 2 , the zinc plated layer is formed by plating at a current density of 40 to 60 A/dm 2 , and the thermal diffusion is conducted by a low temperature diffusion at a temperature of 500 to 550° C. 
   
   
       17 . A metal cord for use in the rubber-cord complex according to  claim 2 , wherein the brass plated layer is formed by thermal diffusion of a copper plated layer and a plated layer of a zinc alloy selected from a zinc-nickel alloy and a zinc-cobalt alloy, the layers being formed in layers on the metal wire, in which the copper plated layer is formed by plating at a current density of 15 to 25 A/dm 2 , the zinc alloy plated layer is formed by plating at a current density of 40 to 60 A/dm 2 , and the thermal diffusion is conducted by a low temperature diffusion at a temperature of 500 to 550° C. 
   
   
       18 . A metal cord for use in the rubber-cord complex according to  claim 3 , wherein the brass plated layer is formed by thermal diffusion of a copper plated layer and a plated layer of a zinc alloy selected from a zinc-nickel alloy and a zinc-cobalt alloy, the layers being formed in layers on the metal wire, in which the copper plated layer is formed by plating at a current density of 15 to 25 A/dm 2 , the zinc alloy plated layer is formed by plating at a current density of 40 to 60 A/dm 2 , and the thermal diffusion is conducted by a low temperature diffusion at a temperature of 500 to 550° C. 
   
   
       19 . A pneumatic tire in which the rubber-cord complex according to  claim 2  is used as a ply for tire reinforcement. 
   
   
       20 . A pneumatic tire in which the rubber-cord complex according to  claim 3  is used as a ply for tire reinforcement.