Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2002-07-17
2004-10-19
Teskin, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S098000, C525S271000, C524S575000, C156S334000
Reexamination Certificate
active
06806317
ABSTRACT:
TECHNICAL FIELD
The present invention relates to adhesive compositions and block copolymers suitable for them, and more particularly to adhesive compositions suitable for hot melt adhesive uses and block copolymers which may be suitably used for them.
BACKGROUND ART
As the base polymer of hot melt adhesives, various copolymers are used such as ethylene-vinyl acetate copolymers, block copolymers of styrene and conjugated diene and their hydrogenated products, ethylene-&agr;-olefin copolymers, polyester resins, etc. Particularly, block copolymers comprising styrene and conjugated diene have a long open time and relatively well balanced adhesion and holding power; therefore, they are preferably being used in the adhesives for various disposable sanitary goods etc. and for surface protection films. For example, an adhesive composition based on a straight-chain block copolymer such as polystyrene-polybutadiene-polystyrene or polystyrene-polyisoprene-polystyrene is disclosed in JP, B, 45-41518 (corresponding U.S. Pat. No. 3,427,269). Also JP, B, 56-49958 discloses a hot melt adhesive composition utilizing (polystyrene-polybutadiene)nX branched-chain block copolymer.
However, the adhesive compositions containing a block copolymer composed of styrene and conjugated diene have a problem in their cohesion (holding power) in high temperature conditions, which is caused by the fact that the glass transition temperature (Tg) of the polystyrene block, which is the base polymer of the block copolymer, is as low as about 100° C., and there is a strong desire for improving the cohesion (holding power) of these adhesive compositions.
DISCLOSURE OF THE INVENTION
The object of the present invention is to solve the above described problem providing an adhesive composition having good holding power, and a block copolymer suitable for the same.
The inventors of the present invention have conducted eager investigations to solve the above described problem and found that the problem may be solved by utilizing an adhesive composition containing a block copolymer composed of &agr;-methyl styrene and a conjugated diene; thereby they have eventually completed the present invention.
Accordingly, the present invention relates to an adhesive composition containing a block copolymer, wherein the block copolymer has a polymer block (A) which is principally composed of a &agr;-methyl styrene unit, and a polymer block (B) which is principally composed of a conjugated diene unit and of which at least part of the carbon-carbon unsaturated double bonds may be hydrogenated.
The present invention also relates to the above described adhesive composition wherein the conjugated diene unit in the polymer block (B) is principally a 1,3-butadiene unit.
The present invention further relates to the above described adhesive composition, characterized in that the block copolymer has (1) a polymer block (A) which has a number-average molecular weight of 1,000 to 300,000 and (2) a polymer block (B) including: a polymer block (b1) which has a number-average molecular weight of 500 to 10,000 and of which 1,4-bond content is less than 30%; and a polymer block (b2) which has a number-average molecular weight of 10,000 to 400,000 and of which 1,4-bond content is not less than 30%, and in that the block copolymer has at least one (A-b1-b2) structure.
The present invention also relates to the above described adhesive composition, characterized in that the block copolymer includes at least one (A-b1-b2) structure obtained by:
(1) forming a polymer block (A) by polymerizing &agr;-methyl styrene of 5 to 50% by weight concentration at a temperature from −30° C. to 30° C. in the presence of a polar compound of 0.1 to 10% by weight concentration using a organic lithium compound as an initiator in a nonpolar solvent; then
(2) forming a polymer block (b1) by polymerizing 1 to 100 mol equivalent of conjugated diene with respect to living poly-&agr;-methyl styryl lithium; and thereafter
(3) forming a polymer block (b2) by polymerizing remaining conjugated dienes at a temperature higher than 30° C.
The present invention further relates to the above described adhesive composition wherein the conjugated diene unit in the polymer block (B) is principally a 1,3-butadiene unit and/or an isoprene unit.
The present invention also relates to the above described adhesive composition, wherein the conjugated diene unit in the polymer block (B) is principally a 1,3-butadiene unit.
The present invention further relates to the above described adhesive composition, wherein at least part of the carbon-carbon unsaturated double bonds of the polymer block (B) are hydrogenated.
The present invention also relates to a block copolymer, having a polymer block (A) which is principally composed of a &agr;-methyl styrene unit, and a polymer block (B) which is principally composed of a conjugated diene unit and of which at least part of the carbon-carbon unsaturated double bonds may be hydrogenated, wherein said block copolymer includes:
(1) a polymer block (A) of a number-average molecular weight of 1,000 to 300,000; and
(2) a polymer block (B) including: a polymer block (b1) which has a number-average molecular weight of 500 to 10,000 and of which 1,4-bond content is less than 30%; and a polymer block (b2) which has a number-average molecular weight of 10,000 to 400,000 and of which 1,4-bond content is not less than 30%, and said block copolymer includes at least one (A-b1-b2) structure.
The present invention further relates to the above block copolymer, wherein the conjugated butadiene units forming the block b1 and the block b2 are 1,3-butadiene unit and/or isoprene unit.
The present invention also relates to the above described block copolymer, wherein each of the conjugated diene units forming the block b1 and the block b2 is 1,3-butadiene unit.
And the present invention relates to the above described block copolymer, wherein at least part of the carbon-carbon unsaturated double bonds resulting from the conjugated diene unit of the polymer block (B) are hydrogenated.
BEST MODE FOR CARRYING OUT THE INVENTION
The polymer block (A) of the block copolymer forming the adhesive composition of the present invention is principally composed of a &agr;-methyl styrene unit. To improve the holding power of the adhesive composition to be produced, the content of &agr;-methyl styrene unit within the polymer block (A) is preferably not less than 50% by weight, more preferably not less than 70% by weight, and still more preferably not less than 90% by weight.
The polymer block (A) of the block copolymer of the present invention may be copolymerized with other monomers within the scope of not compromising the spirit of the present invention. Out of those which are capable of anionic polymerization, such monomers include, though will not be limited to, vinyl aromatic compounds such as styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, 1,3-dimethyl styrene, and diphenyl ethylene; and conjugated dienes such as 1,3-butadiene, isoprene, and 2,3-dimethyl-1,3-butadiene. Particularly preferable are styrene, p-methyl styrene, 1,3-butadiene, and isoprene.
There is no limitation on the form of copolymerization in which the polymer block (A) is copolymerized with other monomers; it may be either a random form or a tapered form.
Examples of the conjugated dienes forming the polymer block (B) of the block copolymer constituting the adhesive composition of the present invention include conjugate dienes such as 1,3-butadiene, isoprene, and 2,3-dimethyl-1,3-butadiene. These may be used either individually or combining more than two kinds. Out of these conjugated dienes, 1,3-butadiene and isoprene are preferable, and particularly 1,3-butadiene is preferable.
Moreover, the polymer block (B) may be copolymerized with a monomer other than conjugated diene compounds, which is capable of anionic polymerization, excepting &agr;-methyl styrene. There is no limitation on the form of copolymerization, and it may be a random form or a tapered form. When &agr;-methyl styrene that remained dur
Hamada Kenichi
Ishiura Kazushige
Morishita Yoshihiro
Nakata Hiromichi
Kuraray Co. Ltd.
Teskin Fred
Wolf Greenfield & Sacks P.C.
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