Rubber-metal adhesion promoter, rubber composition, and tire

A method of adhering rubber and metal comprising applying a rubber-metal adhesion promoter to a rubber component or a metal component or both and vulcanizing the rubber to adhere the rubber component and the metal component;

• wherein the rubber-metal adhesion promoter comprises:
• a metal salt (1) of a carboxylic acid which is a metal salt of an aliphatic carboxylic acid having 2 to 25 carbon atoms and in which the metal is bismuth, copper, antimony, silver or niobium;
• or
• a compound (2) represented by the following general formula (A):
• [Chemical Formula 1]
• [(RCOO)xMO]3Z (A)
• wherein Z represents a structure selected from the following formulae (z-1) to (z-4);
• wherein M represents bismuth, copper, antimony, silver or niobium;
• (RCOO) represents a residue of an aliphatic carboxylic acid having 2 to 25 carbon atoms;
• and x represents an integer of {(valence of M)−1}.

A method of producing a rubber composition for use in tires and belt conveyors comprising applying a rubber-metal adhesion promoter to a rubber component or a metal component or both and vulcanizing the rubber to produce the rubber composition;

• wherein the rubber-metal adhesion promoter comprises:
• a metal salt (1) of a carboxylic acid which is a metal salt of an aliphatic carboxylic acid having 2 to 25 carbon atoms and in which the metal is bismuth, copper, antimony, silver or niobium;
• or
• a compound (2) represented by the following general formula (A):
• [Chemical Formula 1]
• [(RCOO)xMO]3Z (A)
• wherein Z represents a structure selected from the following formulae (z-1) to (z-4);
• wherein M represents bismuth, copper, antimony, silver or niobium;
• (RCOO) represents a residue of an aliphatic carboxylic acid having 2 to 25 carbon atoms;
• and x represents an integer of {(valence of M)−1}.