Hot-melt adhesive composition for non-wovens

1. A hot-melt adhesive composition used in non-woven assemblies, comprising

(a) 100 parts by weight of a block copolymer of the formula [S-(I/B)] n X, wherein S represents a predominantly poly(styrene) block and (I/B) represents a polymer block obtained by a random copolymerization of a mixture of predominantly isoprene and butadiene in a weight ratio in the range of from 70:30 to 30:70, wherein n is an integer in the range of from 3 to 5, and wherein X is the remainder of a coupling agent, wherein the block copolymer has a poly(styrene) content of from 28 to 50 wt % and a coupling efficiency of from 50 to 100%, and a melt flow index measured at 200° C./5 kg ranging from 1.0 to 12 g/10 min,

(b) from 250 to 300 parts by weight of a tackifying resin,

(c) from 50 to 150 parts by weight of a plasticizer, and

(d) from 0 to 3 parts by weight of one or more stabilizers and/or antioxidants.

2. The adhesive composition of claim 1 , wherein the block (I/B) has been obtained by a random polymerization of a mixture of butadiene and isoprene in a weight ratio of from 60:40 to 40:60.

3. The adhesive composition of claim 1 , wherein the block (I/B) has been obtained by a random polymerization of a mixture of butadiene and isoprene in a weight ratio of from 55:45 to 45:55.

4. The adhesive composition of claim 2 , wherein the (I/B) block has a vinyl content in the polymerized butadiene in the range of from 7 to 12 wt % and a vinyl content in the polymerized isoprene in the range of from 4 to 8 wt %.

5. The adhesive composition of claim 1 , wherein the (I/B) block, has a vinyl content in the polymerized butadiene in the range of from 7 to 9 wt % and a vinyl content in the polymerized isoprene in the range of from 4 to 6 wt %.

6. The adhesive composition of claim 4 , wherein the block copolymer S-(I/B)-S has a polystyrene content of from 28 to 35 wt %.

7. The adhesive composition of claim 1 , wherein the block copolymer S-(I/B)-S has a polystyrene content of from 29 to 33 wt %.

8. The adhesive composition of claim 1 , wherein from 250 to 280 parts by weight of hydrocarbon resin per 100 parts by weight of block copolymer have been included.

9. The adhesive composition of claim 1 , wherein the coupling efficiency of the block copolymer [S-(I/B)] n X is from 50 to 85%.

10. The adhesive composition of claim 6 , wherein the coupling efficiency of the block copolymer [S-(I/B)] n X is from 50 to 85%.

11. The adhesive composition of claim 10 , wherein the one or more stabilizers and/or antioxidants are present in an amount from 0.5 to 3 parts by weight.

12. A disposable article selected from the group consisting of infant and adult diapers or sanitary napkins, incontinent pads, bed pads, feminine pads, and panty shields, comprising at least one non-woven element and assembled by the use of the hot-melt adhesive comprising

(a) 100 parts by weight of a block copolymer of the formula [S-(I/B)] n X, wherein S represents a predominantly poly(styrene) block and (I/B) represents a polymer block obtained by a random copolymerization of a mixture of predominantly isoprene and butadiene in a weight ratio in the range of from 70:30 to 30:70, wherein n is an integer in the range of from 3 to 5, and wherein X is the remainder of a coupling agent, wherein the block copolymer has a poly(styrene) content of from 28 to 50 wt % and a coupling efficiency of from 50 to 100%, and a melt flow index measured at 200° C./5 kg ranging from 1.0 to 12 g/10 min,

(b) from 250 to 300 parts by weight of a tackifying resin,

(c) from 50 to 150 parts by weight of a plasticizer, and

(d) from 0 to 3 parts by weight of one or more stabilizers and/or antioxidants.

13. A block copolymer of the formula [S-(I/B)] n X wherein S represents a predominantly poly(styrene) block and (I/B) represents a polymer block obtained by a random copolymerization of a mixture of predominantly isoprene and butadiene in a weight ratio in the range of from 60:40 to 40:60, wherein n is an integer in the range of from 3 to 5, wherein X is the residue of a coupling agent and wherein the total block copolymer has a melt flow index measured at 200° C./5 kg in the range of from 1.0 to 12 g/10 min., and has a poly(styrene content of from 28 to 50 wt % and a coupling efficiency of from 50 to 100%.

14. The block copolymer of claim 13 , wherein the S blocks have been derived from substantially pure styrene.

15. The block copolymer of claim 14 , wherein the (I/B) block has a vinyl content in the polymerized butadiene in the range of from 7 to 12 wt % and a vinyl content in the polymerized isoprene in the range of from 4 to 8 wt %.

16. The block copolymer of claim 13 , wherein the (I/B) block has a vinyl content in the polymerized butadiene in the range of from 7 to 9 wt % and a vinyl content in the polymerized isoprene in the range of from 4 to 6 wt %.

17. The block copolymer of claim 15 , wherein the block copolymer [S-(I/B)] n X has a polystyrene content of from 28 to 35 wt %.

18. The block copolymer of claim 13 , wherein the block copolymer [S-(I/B)] n X has a polystyrene content of from 28 to 35 wt %.

19. The block copolymer of claim 13 , wherein the block copolymer [S-(I/B)] n X has a coupling efficiency of from 50 to 85%.

20. The block copolymer of claim 17 , wherein the block copolymer [S-(I/B)] n X has a coupling efficiency of from 50 to 85%.