Hot melt adhesive that has good open time at room temperature and can form cree-resistant bonds

Claim 2

Hot-melt adhesive comprising by weight (a) an ethylene/vinyl acetate copolymer having from 14 to 35% of vinyl acetate and a melt index of at least 150, and (b) from 50 to 200 parts of tackifying resin per 100 parts of the copolymer, which resin has a ring and ball softening point within the range of from 70° to 115°C and a combined aromatic and olefinic content within the range of from 0.5 to 50 mole % and is so selected that the adhesive has a shear storage modulus G′ of less than 10⁶ dynes/cm² for more than 5 seconds after being deposited onto an unheated substrate as a 50µm layer, and the adhesive has an ultimate shear storage modulus G′ of at least 5 x 10⁶ dynes/cm², and when either the melt index is less than 500 or there are less than 100 parts of the tackifying resin per 100 parts of copolymer, the ring and ball softening point and the combined aromatic and olefinic content are both near the central points of said ranges.

Claim 3

Hot-melt adhesive as defined in claim 1 wherein the ring and ball softening point of the tackifying resin is between 80° and 105°C.

Claim 4

Hot-melt adhesive as defined in claim 1 wherein the tackifying resin has an aromatic/olefinic content between 2 and 30 mole %.

Claim 5

Hot-melt adhesive as defined in claim 1 wherein the tackifying resin is selected from polyterpene resins, hydrogenated wood rosins, and derivatives thereof.

Claim 6

Hot-melt adhesive as defined in claim 1 wherein there are from 120 to 170 parts of the tackifying resin per 100 parts by weight of the ethylene/vinyl acetate copolymer.

Claim 7

Hot-melt adhesive as defined in claim 1 wherein the melt index of the ethylene/vinyl acetate copolymer exceeds 500.

Claim 8

Hot-melt adhesive as defined in claim 1 wherein the vinyl acetate content of the ethylene/vinyl acetate copolymer is from 23 to 30 weight %.

Claim 9

Hot-melt adhesive as defined in claim 1 wherein no more than 50 mole % of the saturated aliphatic content of the tackifying resin is cycloaliphatic.

Claim 10

Hot melt adhesive as defined in claim 1 and having a shear storage modulus G′ of less than 7 x 10⁵ dynes/cm² for more than 5 seconds after being deposited as a 50µm layer.

Claim 11

Hot-melt adhesive as defined in claim 1 and in stick form.

Claim 12

Hot-melt adhesive as defined in claim 1 and in the form of a rod that can be driven into the heat chamber of a hand-held dispenser.

Claim 13

A hot-melt adhesive rod that can be deposited from a hand-held dispenser onto an unheated surface to form a thin layer that remains tacky for at least 5 seconds at room temperature and then forms creep-resistant bonds without applying heat or more than hand pressure, said rod comprising by weight (a) an ethylene/vinyl acetate copolymer having from 14 to 35% of vinyl acetate and a melt index of at least 150, and (b) from 50 to 200 parts of tackifying resin per 100 parts of the copolymer, which resin has a ring and ball softening point within the range of from 70° to 115°C and a combined aromatic and olefinic content within the range of from 0.5 to 50 mole % and is so selected that the hot-melt adhesive has a shear storage modulus G′ of less than 10⁶ dynes/cm² for more than 5 seconds after being deposited onto an unheated substrate as a 50µm layer, and the adhesive has an ultimate shear storage modulus G′ of at least 5 x 10⁶ dynes/cm², and when either the melt index is less than 500 or there are less than 100 parts of the tackifying resin per 100 parts of copolymer, the ring and ball softening point and the combined aromatic and combined content are both near the central points of said ranges.

Claim 14

A hot-melt adhesive rod that can be deposited from a hand-held dispenser onto an unheated surface to form a thin layer that remains tacky for at least 5 seconds at room temperature and then forms creep-resistant bonds without applying heat or more than hand pressure, said rod comprising by weight (a) an ethylene/vinyl acetate copolymer having from 14 to 35% of vinyl acetate and a melt index of at least 150, and (b) from 50 to 200 parts of tackifying resin per 100 parts of the copolymer, which resin has a ring and ball softening point within the range of from 70° to 115°C and a combined aromatic and olefinic content within the range of from 0.5 to 50 mole % and is so selected that the hot-melt adhesive has a shear storage modulus G′ of less than 10⁶ dynes/cm² for more than 5 seconds after being deposited onto an unheated substrate as a 50µm layer, and the adhesive has an ultimate shear storage modulus G′ of at least 5 x 10⁶ dynes/cm², and when either the melt index is less than 500 or there are less than 100 parts of the tackifying resin per 100 parts of copolymer, the ring and ball softening point and the combined aromatic and combined content are both near the central points of said ranges.

Claim 15

A hot-melt adhesive rod as defined in claim 12 having two different adhesive compositions, one at its core and the other at its surface, wherein the shear storage modulus G′ of at least one of those compositions by itself exceeds 10⁶ dynes/cm² within 5 seconds after being deposited as a 50 µm layer and a blend of those two compositions meets the definition of claim 12.

Claim 16

Hot-melt adhesive rod as defined in claim 12 and having teeth by which it can be mechanically driven into the heat chamber of a dispenser.

Claim 17

A substrate bearing a layer of the adhesive of claim 1.