Hot melt thermoplastic adhesive foam system

The method of bonding with a hot melt thermoplastic adhesive foam which comprises

• heating a mixture of solid thermoplastic adhesive and blowing agent to convert the adhesive to a liquid state,
• pressurizing the mixture while further heating it so as to cause gas to be evolved from the blowing agent and forced into solution with the liquid adhesive,
• dispensing the liquid and gas solution at atmospheric pressure whereby said gas is released from solution and forms a hot adhesive foam,
• compressing said hot melt adhesive foam between two substrates to force gas from the foam, and
• cooling the compressed adhesive to form upon solidification a bond between said substrates.

The method of bonding with a hot melt thermoplastic adhesive having an extended open time in a foamed uncompressed state and a short set time in a foamed compressed state, which method comprises:

• heating a mixture of solid thermoplastic adhesive and blowing agent to convert the adhesive to a liquid state and to cause said blowing agent to evolve a gas,
• pressurizing the liquid adhesive and gas so as to force the gas into solution with the liquid adhesive,
• dispensing the liquid and gas solution at atmospheric pressure onto a substrate such that the dissolved gas comes out of solution and forms a hot cellular foam adhesive of extended open time,
• compressing the hot cellular foam adhesive between said substrate and a second substrate such that a substantial portion of the gas entrapped in said foam is released to atmosphere and the set time of the adhesive foam is substantially reduced by said compression, and
• cooling the compressed adhesive to form upon solidification a bond between said substrates.