Low application temperature hot melt adhesive

Abstract

A hot melt adhesive composition, comprising a blend of components including about 10% to about 40% by weight of an elastomeric block copolymer, preferably styrene-isoprene-styrene (SIS) or styrene-butadiene-styrene (SBS), about 15% to about 70% by weight of a first midblock tackifying resin having a softening point of at least about 110° C. and having an aromatic content of at least about 1.5% by weight; about 0 to 55% of second midblock tackifying resin, about 5% to about 35% by weight of a plasticizer; and about 0% to about 20% by weight of an end block resin having a softening point lower than 125° C.; wherein the components total 100% by weight of the composition, the viscosity of the composition is equal to or less than about 20,000 mPa.s at 120° C., and is applied at a temperature lower that 150° C. and initial bond retention of the composition on elastic strands is at least about 60%. Also, the elastic modulus G′ of the composition is higher than about 5000 Pa, the vicous modules G″ is higher than about 50 Pa, and the tan delta value is between about 0.5 and about 60. Laminates, especially those used in disposable soft goods, and methods of making such laminates are also described. The adhesive composition and/or laminate may be used in making a variety of end products such as a disposable diaper, a sanitary napkin, a bed pad, a bandage, a surgical drape, a tape, a label, a plastic sheet, a nonwoven sheet, a paper sheet, a cardboard, a book, a filter, or a package.

1 . A hot melt adhesive composition, comprising a blend of the following components: 
 about 10% to about 40% by weight of an elastomeric block copolymer having a structure represented by A-B, A-B-A, A-(B-A) n -B, or (A-B) n -Y wherein A comprises a polyvinyl aromatic block having a Tg higher than 80° C., B comprises a rubbery midblock having a Tg lower than −10° C., Y comprises a multivalent compound, and n is an integer of at least 3;    about 15% to about 70% by weight of a first midblock tackifying resin having a softening point of at least about 110° C. and having an aromatic content of at least about 1.5% by weight;    about 0 to 55% of second midblock tackifying resin    about 5% to about 35% by weight of a plasticizer; and    about 0% to about 20% by weight of an end block tackifying resin having a softening point lower than 125° C.;    wherein the components total 100% by weight of the composition, the viscosity of the composition is equal to or less than about 20,000 mPa.s at 120° C., and may be applied at a temperature lower than 150° C. and initial bond retention of the composition on elastic strands is at least about 60%.    
   
   
       2 . The composition of  claim 1  wherein said block copolymer is selected from the group consisting of SB, SBS, SIS, SIBS, SEBS, SEP, SEPS, SBBS, SEEPS and blends thereof.  
   
   
       3 . The composition of  claim 1  wherein said block copolymer is SIS.  
   
   
       4 . The composition of  claim 1  wherein said block copolymer is SBS  
   
   
       5 . The composition of  claim 1  wherein said block copolymer is a mixture of SIS and SBS block copolymers.  
   
   
       6 . The composition of  claim 2  wherein said block copolymer has a styrene content of from about 20% to about 51% by weight.  
   
   
       7 . The composition of  claim 1  wherein said first midblock resin has a softening point of at least about 115° C.  
   
   
       8 . The composition of  claim 1  wherein said first midblock resin has an aromatic content of at least about 2% by weight  
   
   
       9 . The composition of  claim 1  wherein a fraction x of said total midblock resin has a softening point z of at least about 115° C., so that z≧−60x+146, and has an aromaticity content y so that y≧−17x +18.  
   
   
       10 . The composition of  claim 1  wherein said composition has a viscosity equal to or less than 15,000 mPa.s at 120° C.  
   
   
       11 . The composition of  claim 1  wherein said composition has a viscosity equal to or less than 12,000 mPa.s at 120° C.  
   
   
       12 . The composition of  claim 1  wherein the end-block tackifying resin is a product from pure monomer polymerization.  
   
   
       13 . The composition of  claim 1  wherein the end-block tackifying resin has a softening point of from 50 to 120° C.  
   
   
       14 . The composition of  claim 1  wherein the end-block tackifying resin has a softening point of from 70 to 115° C.  
   
   
       15 . The composition of  claim 1  having about 40% to about 65% by weight of said first midblock tackifying resin.  
   
   
       16 . The composition of  claim 1  having about 50% to about 62% by weight of said first midblock tackifying resin.  
   
   
       17 . The composition of  claim 1  wherein said composition has an initial bond retention of at least about 70%.  
   
   
       18 . The composition of  claim 1  wherein said composition has an initial bond retention of at least about 75%.  
   
   
       19 . The composition of  claim 1  wherein said composition has an initial bond retention of at least about 80%.  
   
   
       20 . The composition of  claim 1  further having a one-week-aged bond retention of at least about 50%.  
   
   
       21 . The composition of  claim 1  further having a one-week-aged bond retention of at least about 60%.  
   
   
       22 . The composition of  claim 1  further having a one-week-aged bond retention of at least about 70%.  
   
   
       23 . The composition of  claim 1  wherein the mid-block tackifying resin is selected from the group consisting of aliphatic hydrocarbon resins and their hydrogenated derivatives, hydrogenated cycloaliphatic hydrocarbon resins, aromatic modified aliphatic or hydrogenated cycloaliphatic hydrocarbon resins, aliphatic modified aromatic hydrocarbon resins, partially or fully hydrogenated aromatic hydrocarbon resins, polyterpene and styrenated polyterpene resins.  
   
   
       24 . The composition of  claim 1  further including a plasticizer is selected from the group consisting of mineral oil and liquid polybutene.  
   
   
       25 . The composition of  claim 1  wherein further including a wax is selected from the group consisting of petroleum waxes, microcrystalline waxes, low molecular weight polyethylene and polypropylene, synthetic waxes and polyolefin waxes.  
   
   
       26 . A hot melt adhesive composition, comprising a blend of the following components: 
 about 10% to about 40% by weight of an elastomeric block copolymer having a structure represented by A-B, A-B-A, A-(B-A) n -B, or (A-B) n -Y wherein A comprises a polyvinyl aromatic block having a Tg higher than 80° C., B comprises a rubbery midblock having a Tg lower than −10° C., Y comprises a multivalent compound, and n is an integer of at least 3;    about 15% to about 70% by weight of a first midblock tackifying resin having a softening point of at least about 110° C. and having an aromatic content of at least about 1.5% by weight;    about 0 to 55% of second midblock tackifying resin;    about 5% to about 35% by weight of a plasticizer; and    about 0% to about 20% by weight of an end block tackifying resin having a softening point lower than 125° C.;    wherein the components total 100% by weight of the composition, the viscosity of the composition is equal to or less than about 20,000 mPa.s at 120° C., and may be applied at a temperature lower than 150° C., and the elastic modulus G′ at 60° C. is higher than about 5000 Pa, and the viscous modulus G″ at 120° C. is higher than about 50 Pa, and the tan delta value at 100° C. is between about 0.5 and 20 about 60.    
   
   
       27 . The composition of  claim 26  wherein said elastic modulus G′ is higher than about 6000 Pa.  
   
   
       28 . The composition of  claim 26  wherein said viscous modulus G″ is between about 50 Pa and about 500 Pa.  
   
   
       29 . The composition of  claim 26  wherein said tan delta value is between about 1 and about 50.  
   
   
       30 . The composition of  claim 26  wherein said tan delta value is between about 2 and about 30.  
   
   
       31 . The composition of  claim 26  wherein said block copolymer is selected from the group consisting of SB, SBS, SIS, SIBS, SEBS, SEP, SEPS, SBBS, SEEPS and blends thereof.  
   
   
       32 . The composition of  claim 26  wherein said block copolymer is SIS.  
   
   
       33 . The composition of  claim 26  wherein said block copolymer is SBS  
   
   
       34 . The composition of  claim 26  wherein said block copolymer is a mixture of SIS and SBS block copolymers.  
   
   
       35 . The composition of  claim 26  wherein said block copolymer has a styrene content of from about 20% to about 51% by weight.  
   
   
       36 . The composition of  claim 26  wherein said first midblock resin has a softening point of at least about 115° C.  
   
   
       37 . The composition of  claim 26  wherein said first midblock resin has an aromatic content of at least about 2% by weight.  
   
   
       38 . The composition of  claim 26  wherein a fraction x of said total midblock resin has a softening point z of at least about 115° C., so that z≧−60x+146, and has an aromaticity content y so that y≧−17x+18.  
   
   
       39 . The composition of  claim 26  wherein said composition has a viscosity equal to or less than 15,000 mPa.s at 120° C.  
   
   
       40 . The composition of  claim 26  wherein said composition has a viscosity equal to or less than 12,000 mPa.s at 120° C.  
   
   
       41 . The composition of  claim 26  wherein the end-block tackifying resin is a product from pure monomer polymerization.  
   
   
       42 . The composition of  claim 26  wherein the end-block tackifying resin has a softening point of from 50 to 120° C.  
   
   
       43 . The composition of  claim 26  wherein the end-block tackifying resin has a softening point of from 70 to 115° C.  
   
   
       44 . The composition of  claim 26  having about 40% to about 65% by weight of said first midblock tackifying resin.  
   
   
       45 . The composition of  claim 26  having about 50% to about 62% by weight of said first midblock tackifying resin.  
   
   
       46 . The composition of  claim 26  wherein the mid-block tackifying resin is selected from the group consisting of aliphatic hydrocarbon resins and their hydrogenated derivatives, hydrogenated cycloaliphatic hydrocarbon resins, aromatic modified aliphatic or hydrogenated cycloaliphatic hydrocarbon resins, aliphatic modified aromatic hydrocarbon resins, partially or fully hydrogenated aromatic hydrocarbon resins, polyterpene and styrenated polyterpene resins.  
   
   
       47 . The composition of claim  26 further including a plasticizer is selected from the group consisting of mineral oil and liquid polybutene.  
   
   
       48 . The composition of  claim 26  wherein further including a wax is selected from the group consisting of petroleum waxes, microcrystalline waxes, low molecular weight polyethylene and polypropylene, synthetic waxes and polyolefin waxes.  
   
   
       49 . An elastic laminate comprising a first layer of nonwoven material, a second layer of nonwoven material, and one or a plurality of elastomeric substrates disposed between said first and second nonwoven layers, bonded together with the adhesive composition of  claim 1 .  
   
   
       50 . The elastic laminate of  claim 49  wherein the said one or a plurality of elastomeric substrates are elastic strands.  
   
   
       51 . An elastic laminate comprising a first layer of nonwoven material, a second layer of film material, and one or a plurality of elastomeric substrates disposed between said first and second layers, bonded together with the adhesive composition of  claim 1 .  
   
   
       52 . The elastic laminate of  claim 51  where the said film comprises a polyethylene film, a polypropylene film, an ethylene-propylene copolymer film or a cloth-like coated film material  
   
   
       53 . The elastic laminate of  claim 51  wherein the said one or a plurality of elastomeric substrates are elastic strands.  
   
   
       54 . A laminate comprising a first layer of nonwoven material bonded to a second layer of film material with the adhesive composition of  claim 1 .  
   
   
       55 . The laminate of  claim 54  where the said film material comprises a polyethylene film, a polypropylene film, an ethylene-propylene copolymer film or a cloth-like coated film material.  
   
   
       56 . An article comprising the adhesive composition of  claim 1 .  
   
   
       57 . The article of  claim 56  comprising a disposable diaper, a sanitary napkin, a bed pad, a bandage, a surgical drape, a tape, a label, a plastic sheet, a nonwoven sheet, a paper sheet, a cardboard, a book, a filter, or a package.  
   
   
       58 . A method of making an elastic laminate comprising the steps of: 
 feeding a first substrate in a first direction;    feeding a second substrate spaced from said first substrate in said first direction;    feeding one or a plurality of elastomeric substrate or substrates between said first and second substrates in said first direction, said elastomeric substrates are stretched before, during or after adhesive application;    applying an adhesive composition of  claim 1  to either said elastomeric substrate or substrates or one or both of said substrates; and    compressing said substrates together to form said elastic laminate.    
   
   
       59 . The method of  claim 58  wherein the said one or a plurality of elastomeric substrate or substrates are elastic strands, stretched in said first direction  
   
   
       60 . The method of  claim 58  wherein said first or second substrate comprises a polyethylene film, a polypropylene film, an ethylene-propylene copolymer film or a cloth-like coated film material, or a nonwoven material.  
   
   
       61 . The method of  claim 58  wherein said elastomeric substrate or substrates are stretched up to about 500% from their initial relaxed state.  
   
   
       62 . The method of  claim 58  wherein the said adhesive is applied continuously or intermittently in the form of a fiber.  
   
   
       63 . The method of  claim 58  wherein the said adhesive is applied continuously or intermittently in the form of a bead, dot, or film.  
   
   
       64 . A method of making a laminate comprising the steps of: 
 feeding a first substrate in a first direction;    feeding a second substrate spaced from said first substrate in said first direction;    applying an adhesive composition of  claim 1  to one or both of said substrates; and    compressing said substrates together to form said laminate.    
   
   
       65 . The method of  claim 64  wherein said first or second substrate comprises a polyethylene film, a polypropylene film, an ethylene-propylene copolymer film or a cloth-like coated film material, or a nonwoven material.  
   
   
       66 . The method of  claim 64  wherein at least one of the said first and second substrate is elastomeric in nature.  
   
   
       67 . The method of  claim 64  wherein the said adhesive is applied continuously or intermittently in the form of a fiber.  
   
   
       68 . The method of  claim 64  wherein the said adhesive is applied continuously or intermittently in the form of a bead, dot, or film.