Block copolymer and adhesive composition

Abstract

Disclosure provides a block copolymer composition having 20% by mass or more and 90% by mass or less of a component (A) and 10% by mass or more and 80% by mass or less of a component (B), wherein the component (A) is a block copolymer having a polymer block mainly comprising a vinyl aromatic monomer unit and a polymer block mainly comprising a conjugated diene monomer unit, and having a weight-average molecular weight of 30,000 or higher and 190,000 or lower; and the component (B) is a block copolymer having a polymer block mainly comprising a vinyl aromatic monomer unit and a polymer block mainly comprising a conjugated diene monomer unit, and having a weight-average molecular weight of 60,000 or higher and 500,000 or lower.

The invention claimed is: 
     
       1. An adhesive composition, comprising:
 100 parts by mass of a block copolymer composition; 
 1 to 600 parts by mass of a tackifier; and 
 0 to 200 parts by mass of a softening agent; 
 wherein the block copolymer composition, comprising 
 20% by mass or more and 90% by mass or less of a component (A) and 
 10% by mass or more and 80% by mass or less of a component (B), 
 wherein the component (A) is a block copolymer having a polymer block (Ar) mainly comprising a vinyl aromatic monomer unit and a polymer block (D) mainly comprising a conjugated diene monomer unit, and having a weight-average molecular weight of 30,000 or higher and 190,000 or lower; 
 the component (A) comprises a block copolymer(s) represented by formulae Ar-D, Ar-D-X, and/or D-Ar-D, wherein X represents a residue of a coupling agent or a residue of a polymerization initiator, 
 the component (B) is a block copolymer having a polymer block (Ar) mainly comprising a vinyl aromatic monomer unit and a polymer block (D) mainly comprising a conjugated diene monomer unit, and having a weight-average molecular weight of 60,000 or higher and 500,000 or lower; and 
 the component (B) comprises a three-branched block copolymer(s) represented by formulae (D-Ar-D) 3 -X and/or (Ar-D) 3 -X, wherein X represents a residue of a coupling agent or a residue of a polymerization initiator, 
 wherein a hydrogenation ratio of the conjugated diene monomer units in the component (A) and the component (B) is 10 to 80% by mol based on the total amount of conjugated diene monomer units in the components (A) and (B); and 
 a ratio of a weight-average molecular weight of the component (B) to a weight-average molecular weight of the component (A) is 1.3 to 10. 
 
     
     
       2. The adhesive composition according to  claim 1 , wherein a vinyl bond content of the conjugated diene monomer units in the component (A) and the component (B) before hydrogenation is 5% by mol or larger and smaller than 30% by mol based on a total amount of the conjugated diene monomer units in the component (A) and the component (B). 
     
     
       3. The adhesive composition according to  claim 1 , wherein the weight-average molecular weight of the component (B) is 100,000 or higher and 500,000 or lower. 
     
     
       4. The adhesive composition according to  claim 1 , wherein the coupling agent comprises a halogen-free coupling agent. 
     
     
       5. The adhesive composition according to  claim 1 , wherein the content of the vinyl aromatic monomer units is 5% by mass or higher and lower than 35% by mass based on 100% by mass of the component (A) and the component (B). 
     
     
       6. The adhesive composition according to  claim 1 , wherein the content of the vinyl aromatic monomer units is 5% by mass or higher and lower than 30% by mass based on 100% by mass of the component (A) and the component (B). 
     
     
       7. The adhesive composition according to  claim 1 , wherein the content of the vinyl aromatic monomer units is 5% by mass or higher and lower than 20% by mass based on 100% by mass of the component (A) and the component (B). 
     
     
       8. The adhesive composition according to  claim 1 , wherein a content of the tackifier is 50 to 400 parts by mass. 
     
     
       9. The adhesive composition according to  claim 1 , further comprising a vinyl aromatic elastomer. 
     
     
       10. The adhesive composition according to  claim 1 , further comprising a conjugated diene rubber. 
     
     
       11. The adhesive composition according to  claim 1 , further comprising a natural rubber. 
     
     
       12. The adhesive composition according to  claim 1 , wherein the component (A) comprises a block copolymer(s) represented by the formulae Ar-D. 
     
     
       13. The adhesive composition according to  claim 1 , wherein the component (A) comprises a block copolymer(s) represented by the formulae Ar-D-X. 
     
     
       14. The adhesive composition according to  claim 1 , wherein the component (A) comprises a block copolymer(s) represented by the formulae D-Ar-D. 
     
     
       15. The adhesive composition according to  claim 1 , wherein the component (B) comprises a block copolymer(s) represented by the formulae (D-Ar-D) 3 -X. 
     
     
       16. The adhesive composition according to  claim 1 , wherein the component (B) comprises a block copolymer(s) represented by the formulae (Ar-D) 3 -X. 
     
     
       17. The adhesive composition according to  claim 1 , wherein the color fastness of the adhesive composition as measured by the difference in the b value using a color difference meter before and after heating the adhesive composition at 180° C. for 180 min is less than 15. 
     
     
       18. The adhesive composition according to  claim 1 , wherein the proportion of the area of the adhesive composition remaining on the surface of a SUS plate to a pressure-sensitive adhesive tape-pasted area after the pressure-sensitive adhesive tape was peeled off is less than 5% of the total taped area.