Radial block copolymers and adhesives based thereon with improved die-cutting performance

Abstract

Improved adhesives are provided through the use of styrenic radial block copolymers, containing at lest 40 wt % diblock copolymers, the adhesives have improved adhesive properties and a reduced elastic behaviour under die-cutting conditions. Compared to conventional linear block copolymers of similar molecular weight, radial copolymers offer higher holding power and lower melt viscosity for the adhesive. They therefore contribute to an improved balance between processability and end-use properties.

1 . A mixture of radial styrenic block copolymer and styrenic diblock copolymer comprising from 60 wt % to 10 wt % of radial styrenic block copolymer and from 40 wt % to 90 wt % of a styrene diene diblock copolymer wherein the styrene diene diblock copolymer is a styrene isoprene diblock copolymer and/or a styrene butadiene diblock copolymer and wherein when the diblock copolymer is a styrene butadiene diblock copolymer it has a styrene content of 10 wt % to 30 wt %.  
     
     
         2 . A mixture according to  claim 1  in which, in the case the radial styrenic block copolymer is a styrene isoprene block copolymer, it comprises i) a polystyrene block segment and ii) a polyisoprene block segment having an end which comprises butadiene, wherein the block copolymer is characterized by the formula: 
         (pS−pl−pB) n X 
       pS being polystyrene, pl being polyisoprene, pB being polybutadiene, X being the residue of a multifunctional coupling agent used in the production of the radial block copolymer and n being a number greater than or equal to 3 and representing the average number of branches appended to X, and further wherein the pS component is present in an amount of at least 10 parts to 30 parts per 100 parts by weight of the radial block copolymer; wherein the weight amount of polybutadiene in the pI−pB segment is less or equal to 10 wt %.  
     
     
         3 . Cancelled  
     
     
         4 . A mixture according to  claim 2  wherein the weight amount of polybutadiene in the pl−pB segment is less than or equal to 5 %.  
     
     
         5 . A mixture according to any of claims  1 ,  2  or  4  wherein the average number molecular weight of the polystyrene component is between 10,000 and 15,000.  
     
     
         6 . A mixture according to any of claims  2  or  4  wherein n is predominately 4.  
     
     
         7 . A mixture according to claims  1 ,  2  or  4  in which the radial block copolymer has a molecular weight (Mw) from 200,000 to 500,000 g/mole.  
     
     
         8 . A mixture according to claims  1 ,  2  or  4  in which the pure radial copolymer has an overall styrene content from 10 wt % to 30 wt %.  
     
     
         9 . A mixture according to claims  1 ,  2  or  4  in which the styrenic radial copolymer has a molecular weight from 240,000 to 400,000 g/mole.  
     
     
         10 . Cancelled  
     
     
         11 . A mixture according to claims  1 ,  2  or  4  in which the diblock copolymer contains from 10 to 30 wt % styrene.  
     
     
         12 . A mixture according to claims  1 ,  2  or  4  in which the styrene diene diblock copolymer is a styrene-butadiene diblock copolymer and has a molecular weight of from 50,000 to 150,000 g/mole.  
     
     
         13 . An adhesive comprising a tackifier and a mixture of a radial styrenic block copolymer and a styrene diene diblock copolymer comprising from 60 wt % to 10 wt % of the radial styrenic block copolymer and from 40 wt % to 90 wt % of the styrenic diene diblock copolymer wherein the styrene diene diblock copolymer is a styrene isoprene diblock copolymer and/or a styrene butadiene diblock copolymer; wherein when the diblock copolymer is a styrene butadiene diblock copolymer it has a styrene content of 10 to 30 wt %.  
     
     
         14 . An adhesive according to  claim 51  in which the radial block copolymer comprises a four arms radial copolymer.  
     
     
         15 . An adhesive according to any of claims  13 ,  51  or  14  in which the radial block copolymer has a molecular weight (Mw) from 200,000 to 500,000 g/mole.  
     
     
         16 . An adhesive according to any of claims  13 ,  51  or  14  in which the pure radial copolymer has an overall styrene content from 10 wt % to 30 wt %.  
     
     
         17 . Cancelled  
     
     
         18 . An adhesive according to claims  13 ,  51  or  14 , in which the diblock copolymer contains from 10 to 30 wt % styrene.  
     
     
         19 . An adhesive according to any of claims  13 ,  51  or  14  in which the styrenic radial copolymer has a molecular weight from 240,000 to 400,000 g/mole.  
     
     
         20 . Cancelled  
     
     
         21 . An adhesive according to any of claims  13 ,  51  or  14 , in which the tackifier is a hydrocarbon resin.  
     
     
         22 . An adhesive according to  claim 21  in which the tackifier is an aliphatic C 5  resin.  
     
     
         23 . An adhesive according to  claim 21  in which the tackifier is an aromatic resin.  
     
     
         24 . An adhesive according to  claim 21  in which the tackifier is an aromatic/aliphatic C 5 /C 9  resin.  
     
     
         25 . An adhesive according to any of  claims 22  to  24  in which the resin is hydrogenated.  
     
     
         26 . An adhesive according to any of claims  13 ,  51  or  14  in which the tackifier is a rosin, rosin ester or a polyterpene resin.  
     
     
         27 . An adhesive according to  claim 26  in which the tackifier is hydrogenated.  
     
     
         28 . An adhesive according to any of claims  13 ,  51  or  14  having a storage modulus plateau at low frequencies below 8,000 Pa, when measured at 20° C.  
     
     
         29 . An adhesive according to any of claims  13 ,  51  or  14  in which G′ intersects a value of 10,000 Pa at a frequency higher than 0.001 rad/s, when measured at 20° C.  
     
     
         30 . An adhesive according to any of claims  13 ,  51  or  14  having a loss factor Tan delta between 0.2 and 1.3 at the frequency at which the storage modulus intersects a value of 10000 Pa, when measured at 20° C.  
     
     
         31 . An adhesive according to any of claims  13 ,  51  or  14  further containing a plasticizing oil.  
     
     
         32 . An adhesive according to  claim 31  containing from 5 to 20 wt % of the plasticizing oil.  
     
     
         33 . A hot melt pressure sensitive adhesive which is an adhesive according to any of claims  13 ,  51  or  14 .  
     
     
         34 . A process for the production of labels comprising, applying as a hot melt an adhesive, according to any of the claims  13 ,  51  or  14  said adhesive being applied to a release liner, and subsequently laminating the coated release liner to a face stock, and converting the laminate into a label stock.  
     
     
         35 . The use in an adhesive of a mixture of a radial styrenic block copolymer and a styrene diene diblock copolymer comprising from 60 wt % to 10 wt % of the radial block copolymer and from 40 wt % to 90 wt % of the styrene diene diblock copolymer wherein the styrene diene diblock copolymer is a styrene isoprene diblock copolymer and/or a styrene butadiene diblock copolymer; wherein when the diblock copolymer is a styrene butadiene diblock copolymer it has a styrene content of 10 wt % to 30 wt %.  
     
     
         36 . The use according to  claim 52  in which the radial block copolymer comprises a four arms radial styrenic copolymer.  
     
     
         37 . The use according to any of claims  35 ,  52  or  36  in which the radial block copolymer has a molecular weight (Mw) from 200,000 g/mole to 500,000 g/mole.  
     
     
         38 . The use according to any of claims  35 ,  52  or  36  in which the radial copolymer has an overall styrenic content from 10 wt % to 30 wt %.  
     
     
         39 . Cancelled  
     
     
         40 . The use according to any of claims  35 ,  52  or  36  in which the diblock copolymer contains from 10 to 30 wt % styrene.  
     
     
         41 . The use according to any of claims  35 ,  52  or  36  in which the styrenic radial copolymer has a molecular weight from 240,000 to 400,000 g/mole.  
     
     
         42 . Cancelled  
     
     
         43 . The use according to any of claims  35 ,  52  or  36  together with a tackifier.  
     
     
         44 . The use according to  claim 43  in which the tackifier is a hydrocarbon resin.  
     
     
         45 . The use according to  claim 44  in which the tackifier is an aliphatic C 5  resin.  
     
     
         46 . The use according to  claim 44  in which the tackifier is an aromatic resin.  
     
     
         47 . The use according to  claim 44  in which the tackifier is an aromatic/aliphatic C 5 /C 9  resin.  
     
     
         48 . The use according to any of  claims 44  to  47  in which the resin is hydrogenated.  
     
     
         49 . The use according to  claim 43  in which the tackifier is a rosin, rosin ester or polyterpene resin.  
     
     
         50 . The use according to  claim 49  in which the tackifier is hydrogenated.  
     
     
         51 . An adhesive according to  claim 13  in which, in the case the radial styrenic block copolymer is a styrene isoprene block copolymer, it comprises i) a polystyrene block segment and ii) a polyisoprene block segment having an end which comprises butadiene, wherein the block copolymer is characterized by the formula: 
         (pS−pl−pB) n X 
       pS being polystyrene, pl being polyisoprene, pB being polybutadiene, X being the residue of a multifunctional coupling agent used in the production of the radial block copolymer and n being a number greater than or equal to 3 and representing the average number of branches appended to X, and further wherein the pS component is present in an amount of at least 10 parts to 30 parts per 100 parts by weight of the radial block copolymer; wherein the weight amount of polybutadiene in the pI−pB segment is less or equal to 10 wt %.  
     
     
         52 . The use according to  claim 35  in which, in the case the radial styrenic block copolymer is a styrene isoprene block copolymer, it comprises i) a polystyrene block segment and ii) a polyisoprene block segment having an end which comprises butadiene, wherein the block copolymer is characterized by the formula: 
         (pS−pl−pB) n X 
       pS being polystyrene, pl being polyisoprene, pB being polybutadiene, X being the residue of a multifunctional coupling agent used in the production of the radial block copolymer and n being a number greater than or equal to 3 and representing the average number of branches appended to X, and further wherein the pS component is present in an amount of at least 10 parts to 30 parts per 100 parts by weight of the radial block copolymer; wherein the weight amount of polybutadiene in the pI−pB segment is less or equal to 10 wt %.