Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1989-10-02
1992-02-18
Marquis, Melvyn I.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525 98, 525250, 525271, 524764, C08F29704, C08L 5302, C08L 9304
Patent
active
050895508
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a block copolymer composition, to an adhesive composition containing said block copolymer composition and to a process for the preparation of said adhesive composition.
Straight-chain block copolymers made up of an aromatic vinyl compound and a conjugated diene are known in the art of anionic polymerization. They have been described, for instance, in Japanese patent specifications 40-23798 and 46-32415. However, when the block copolymers obtained by the methods described herein are used as tackifiers, the following two problems are encountered.
1) The adhesive properties on rough surfaces such as board and veneer board are insufficient and when products with adhesive properties are affixed to such surfaces and left there for a considerable length of time, the affixed products themselves will gradually peel off owing to shrinkage and outside forces.
2) Affixed products with adhesive properties are easily ripped off by shocks from outside.
Various attempts have already been made to solve these problems; for instance in Japanese Patent Specifications 60-221475, 60-223879, 60-223880, 60-226579, pressure-responsive adhesive compositions are described which are made up of block copolymers S.sub.1 -I.sub.1 and S.sub.2 -I.sub.2 -S.sub.3 (S.sub.1, S.sub.2, S.sub.3 being styrene block polymers or block polymers derived from a styrene homolog, and I.sub.1, I.sub.2 being isoprene block polymers or block polymers derived from an isoprene homolog).
However, although the problems described hereinbefore under 1) and 2) are solved for near ambient temperatures, the bonding force of these pressure responsive adhesive compositions at low and high temperatures is still unsatisfactory. The problem lies in the absence of balance between low temperature tack and high temperature retention force.
A block copolymer composition has now been found which when used as adhesive, makes hot melt moulded adhesive compositions with an excellent balance between low temperature tack and high temperature bonding force.
Accordingly, the invention provides a block copolymer composition comprising:
in the range of from 40 to 85% by weight of a block copolymer of the general formula (I) compound and a conjugated diene respectively, which block copolymer has a content of the polymer block of the aromatic vinyl compound A.sub.1 of less than 20% by weight of the total weight of A.sub.1 and B.sub.1, and A.sub.1 and B.sub.1 have a molecular weight of more than 12,000 and more than 150,000, respectively; and in the range of from 15 to 60% by weight of a block copolymer of the general formula (II) vinyl compound and B.sub.2 a polymer block of a conjugated diene, which block copolymer has a total content of the polymer blocks of the aromatic vinyl compound A.sub.2 and A.sub.3 of more than 20% by weight of the total weight of A.sub.2, B.sub.2 and A.sub.3 and A.sub.2 and A.sub.3 each have a molecular weight of higher than 12,000, and (molecular weight of B.sub.2).ltoreq.(molecular weight of B.sub.1)/1.5.
When the content of the polymer block of the aromatic vinyl compound is larger than 20% by weight, or the molecular weight of B.sub.1 is lower than 150,000, there will be insufficient low temperature tack, and when the molecular weight of A.sub.1 is lower than 12,000, the high temperature retention force will be insufficient.
In the block copolymer of the general formula I, the content of the polymer block of the aromatic vinyl compound A.sub.1 on the total amount of A.sub.1 and B.sub.1 is preferably more than 1% by weight, more preferably in the range of from 4 to 18% by weight, still more preferably 5 to 15% by weight; the molecular weight of A.sub.1 is preferably in the range of from 12,000 to 55,000, the molecular weight of B.sub.1 is preferably in the range of from 150,000 to 300,000.
In the block copolymer of the general formula II, the total content of the polymer blocks of the aromatic vinyl compounds A.sub.2 and A.sub.3 on the total amount of A.sub.2, B.sub.2 and A.sub.3 is preferably in the range of from 25 to 80% by weig
REFERENCES:
patent: 4792584 (1988-12-01), Shiraki et al.
patent: 4822653 (1989-04-01), Kauffman et al.
patent: 4892903 (1990-01-01), Himes
Ito Hisaharu
Miyachi Takumi
Sakagami Toshinori
Toyama Yasuo
Jagannathan Vasu S.
Marquis Melvyn I.
Shell Internationale Research Maatschappij B.V.
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