HOT MELT ADHESIVE COMPOSITION

1 . Hot melt adhesive composition comprising:

at least one styrene block copolymer,

at least one acid modified rubber, and

a tackifying resin comprising at least one acid tackifying resin, said acid tackifying resin comprising at least one carboxylic acid group and/or carboxylic anhydride group.

2 . The hot melt adhesive composition according to claim 1 , wherein the acid modified rubber is an acid modified rubber comprising carbon-carbon double bonds selected from acid modified polyisoprene, acid modified polybutadiene, acid modified polypentadiene, acid modified butadiene isoprene copolymer, acid modified isobutene isoprene copolymer, acid modified polychloroprene, acid modified nitrile butadiene copolymer, and mixtures thereof.

3 . The hot melt adhesive composition according to claim 1 , wherein the acid modified rubber is a rubber comprising carbon-carbon double bonds modified with at least one acid compound comprising at least one non-aromatic carbon-carbon double bond and at least one carboxylic acid group and/or carboxylic anhydride group.

4 . The hot melt adhesive composition according to claim 1 , wherein the acid modified rubber is liquid at 23° C. and at atmospheric pressure.

5 . The hot melt adhesive composition according to claim 1 , wherein the total content of the at least one acid modified rubber in the hot melt adhesive composition is comprised between 1% and 15% by weight with respect to the total weight of said composition.

6 . The hot melt adhesive composition according to claim 1 , wherein the acid tackifying resin is an acid modified tackifying resin.

7 . The hot melt adhesive composition according to claim 6 , wherein the acid modified tackifying resin is selected from acid modified phenolic terpene resins, acid modified petroleum resins and mixtures thereof.

8 . The hot melt adhesive composition according to claim 6 , wherein the acid modified tackifying resin is a tackifying resin modified with at least one acid compound comprising at least one non-aromatic carbon-carbon double bond and at least one carboxylic acid group and/or carboxylic anhydride group.

9 . The hot melt adhesive composition according to claim 1 , wherein the tackifying resin further comprises at least one non-acid tackifying resin.

10 . The hot melt adhesive composition according to claim 9 , wherein the non-acid tackifying resin is selected from:

glycerol and pentaerythritol esters of natural and modified rosins,

polyterpene resins, generally resulting from the polymerization of terpene hydrocarbons in the presence of Friedel-Crafts catalysts,

phenolic-modified terpene resins,

aliphatic petroleum hydrocarbon resins (C5) resulting from the polymerization of C5-hydrocarbon monomers,

aromatic petroleum hydrocarbon resins (C9), resulting from the polymerization of C9-hydrocarbon monomers,

petroleum hydrocarbon resins (C5/C9) resulting from the polymerization of a blend of aliphatic C5- and aromatic C9-hydrocarbon monomers,

dicyclopentadiene petroleum resins (DCPD) resulting from the polymerization of dicyclopentadiene monomers,

their corresponding totally or partially hydrogenated derivatives, and

mixtures thereof.

11 . Use of the hot melt adhesive composition according to claim 1 , as an adhesive for bonding two substrates together, or as a coating on the surface of a substrate.

12 . Method for bonding substrates comprising:

heating the hot melt adhesive composition according to claim 1 for at least a period of time long enough to render said composition liquid enough to be applied on a substrate, then

coating said composition on a surface of a first substrate, then

contacting the coated surface of the first substrate with a surface of a second substrate, so as to form an adhesive joint bonding the two substrates.

13 . Article comprising the hot melt adhesive composition according to claim 1 .

14 . Use of a combination of an acid modified rubber and an acid tackifying resin for improving the aged wet adhesiveness of a hot melt adhesive composition.

15 . Use of a non-acid tackifying resin having a softening point of at least 110° C. for improving the initial adhesiveness of a hot melt adhesive composition comprising a combination of an acid modified rubber and an acid tackifying resin.