Pressure-sensitive adhesives based on preferentially tackified immiscible elastomers

A pressure-sensitive adhesive comprising:

• a) a first elastomer selected from the group consisting of polybutadiene, styrene-butadiene-styrene block copolymers, styrene-butadiene block copolymers and mixtures thereof, said first elastomer exhibiting a first glass transition temperature and a first value of tangent delta measured as a function of temperature;
• b) a second elastomer selected from the group consisting of natural rubber, polyisoprene, styrene-isoprene-styrene block copolymers, styrene-isoprene block copolymers, multiarmed styrene-isoprene block copolymers and mixtures thereof, said second elastomer exhibiting a second glass transition temperature greater than the glass transition temperature of the first elastomer and a second value of tangent delta measured as a function of temperature, the second elastomer being immiscible in the first elastomer, said first and second elastomers provided in a weight ratio of first elastomer to second elastomer of above 0.4:1 to about 5:1 and wherein the dynamic mechanical spectrum of the mixture exhibits a first glass transition temperature peak attributable to the first elastomer which is separate from and lower than a second glass transition temperature peak attributable to the second elastomer;
• and
• c) a tackifying system comprising at least one tackifier component which is preferentially soluble in the polymerized isoprene portion of the second elastomer, said tackifying system being present in and amount of 50% to about 80% by weight based on the total weight of said immiscible elastomers and said tackifying system, and sufficient to cause an increase in the temperature difference between the first elastomer attributable glass transition temperature peak and the second elastomer attributable glass transition temperature peak and an increase in the tangent delta value at the second elastomer glass transition temperature peak.

A pressure-sensitive adhesive comprising:

• a) a mixture of immiscible elastomers comprising a first elastomer which is selected from the group consisting of styrene-butadiene, styrene-butadiene-styrene block copolymers and mixtures thereof which first elastomer exhibits a first glass transition temperature peak attributable to polymerized butadiene and a second elastomer selected from the group consisting of multiarmed styrene-isoprene block copolymers, styrene-isoprene block copolymers, styrene-isoprene-styrene block copolymers and mixtures thereof, which second elastomer exhibits a second glass transition peak temperature which is attributable to polymerized isoprene, and is greater than the first glass transition temperature peak, said first and second elastomers provided in a weight ratio of from above 0.4:1 to about 5:1, said first and second glass transition temperature peaks being exhibited on a dynamic mechanical spectrum plot of tangent delta as a function of temperature;
• and
• b) a tackifying system present in an amount of from 50% to about 80% by weight based on the total weight of the said elastomers and said tackifying system, said tackifying system containing at least one tackifier which is preferentially soluble in the polymerized isoprene component of the second elastomer and comprising normally solid resin tackifiers obtained by polymerization of a stream of aliphatic petroleum derivatives in the form of dienes and mono-olefins containing 5 or 6 carbon atoms and having a softening point of 95.degree. C. said tackifying system causing an increase in the second glass transition peak to maintain a second glass transition temperature greater than the first glass transition temperature and an increase in tangent delta at the second glass transition temperature.

A pressure-sensitive adhesive comprising:

• a) a first elastomer selected from the group consisting of polybutadiene, styrene-butadiene-styrene block copolymers, styrene-butadiene block copolymers and mixtures thereof, said first elastomer exhibiting a first glass transition temperature and a first value of tangent delta measured as a function of temperature which is attributable to polymerized butadiene;
• b) a second elastomer selected from the group consisting of natural rubber, polyisoprene, styrene-isoprene-styrene block copolymers, styrene-isoprene block copolymers, styrene-isoprene multiarmed block copolymers and mixtures thereof, said second elastomer exhibiting a second glass transition temperature greater than the first glass transition temperature and a second value of tangent delta measured as a function of temperature which is attributable to polymerized isoprene, the second elastomer being immiscible in the first elastomer, said first and second elastomers provided in proportions at which a dynamic mechanical spectrum plot of tangent delta as a function of temperature exhibits a polymerized butadiene-attributable first glass transition temperature peak determinable separate from and lower than a polymerized isoprene-attributable second glass transition temperature peak;
• c) a first tackifying system comprising at least one tackifying component which is preferentially miscible with the second elastomer and present in an amount sufficient to cause an increase in the second glass transition temperature and an increase in the temperature difference between the polymerized butadiene-attributable glass transition temperature peak and the polymerized isoprene-attributable glass transition temperature peak and an increase in the tangent delta value determined at the glass transition temperature peak attributable to polymerized isoprene;
• and
• d) a second tackifier selected from the group consisting of rosins, rosin esters, polyterpenes and mixtures thereof said tackifiers being present in an amount of from 50% to about 80% by weight based on the total weight of said elastomers and said tackifiers.

A pressure-sensitive adhesive comprising:

• a) a first elastomer selected from the group consisting of styrene-butadiene-styrene block copolymers, styrene-butadiene block copolymers and mixtures thereof, said first elastomer exhibiting a first glass transition temperature and a first value of tangent delta measured as a function of temperature;
• b) a second elastomer providing a polymerized isoprene portion and selected from the group consisting of styrene-isoprene-styrene block copolymers, styrene-isoprene block copolymers, multiarmed styrene-isoprene block copolymers and mixtures thereof, said second elastomer exhibiting a second glass transition temperature greater than the glass transition temperature of the first elastomer and a second value of tangent delta measured as a function of temperature, the second elastomer being immiscible in the first elastomer, the mixture providing a dynamic mechanical spectrum which exhibits a first glass transition temperature peak attributable to the first elastomer which is separate from and lower than a second glass transition temperature peak attributable to the second elastomer;
• and
• c) a tackifying system comprising at least one tackifier component which is preferentially soluble in the polymerized isoprene portion of the second elastomer said tackifying system being present in and amount of 50% to about 80% by weight based on the total weight of said immiscible elastomers and said tackifying system, and sufficient to cause an increase in the temperature difference between a glass transition temperature peak attributable to the first elastomer and a glass transition temperature peak attributable to the second elastomer and an increase in the tangent delta value at the second elastomer glass transition temperature peak.

A pressure-sensitive adhesive comprising a mixture of:

• a) mixture of elastomers comprised of:
• i. a first elastomer selected from the group consisting of styrene-butadiene-styrene block copolymers, styrene-butadiene block copolymers and mixtures thereof, said first elastomer exhibiting in the mixture a first glass transition temperature and a first value of tangent delta measured as a function of temperature;
• ii. a second elastomer selected from the group consisting of styrene-isoprene-styrene block copolymers, styrene-isoprene block copolymers, and mixtures thereof, said second elastomer exhibiting in the mixture a second glass transition temperature greater than the first glass transition temperature and a second value of tangent delta measured as a function of temperature, the second elastomer being immiscible in the first elastomer, said first and second elastomers provided in proportions to provide a dynamic mechanical spectrum plot of tangent delta as a function of temperature which exhibits a polybutadiene-attributable first glass transition temperature peak determinably separate from and lower than a polyisoprene-attributable second glass transition temperature peak, said mixture of immiscible elastomers being combined with;
• iii. a tackifying system comprising normally solid and normally liquid tackifying components in which at least one tackifying component is preferentially miscible with the second elastomer, said tackifying system being present in an amount of from 50% to about 80% by weight based on the mixture of said elastomer and said tackifying system and sufficient to cause an increase in the second glass transition temperature and an increase in the temperature difference between the polybutadiene-attributable glass transition temperature peak and the polyisoprene-attributable glass transition temperature peak and an increase in the tangent delta value determined at the polyisoprene glass transition temperature peak, said normally solid and normally liquid tackifying components being separately obtained by polymerization of a stream of aliphatic petroleum derivatives in the form of dienes and mono-olefins containing 5 or 6 carbon atoms;
• and
• b) a plasticizer oil.