Star-block interpolymers and preparation of the same

Details Star-block interpolymers and preparation of the same Star-block interpolymers and preparation of the same

2001-10-18

2002-10-08

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...

C525S244000, C525S255000, C525S256000, C525S258000, C525S259000, C525S271000, C525S272000, C525S901000

Reexamination Certificate

active

06462137

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to star-block interpolymers of conjugated diene and monovinyl aromatic monomer and preparation of the same. More particularly, the present invention relates to star-block interpolymers having the following structure:
(X-Y)
n
-C
wherein X represents a random copolymer block derived from conjugated diene and monovinyl aromatic monomer;
Y represents a polyconjugated diene block;
C represents a residue derived from a multifunctional lithium based initiator; and
n represents the functionality of the initiator and has a value of not less than 3;
and preparation of the same.
2. Brief Description of Art
Generally, representative block interpolymers based on butadiene, isoprene and styrene are SBS and SIS, wherein SBS is butadiene/styrene triblock copolymers(wherein B represents a polybutadiene block and S represents a polystyrene block), and SIS is isoprene/styrene triblock copolymers(wherein I represents a polyisoprene block and S represents a polystyrene block). By employing difunctional lithium based initiators and changing the charging order of butadiene, isoprene and styrene, block interpolymers having various different structures can be obtained. Such block interpolymers comprise those having the following symmetric structures: (1) S-I-B-I-S(wherein butadiene, isoprene and styrene are charged sequentially); (2) S-B-1-B-S(wherein isoprene, butadiene and styrene are charged sequentially); (3) S-I-BI-I-S(wherein butadiene and isoprene are charged simultaneously at first, and then styrene is charged); (4) S-BS-B-I-B-BS-S(wherein isoprene is charged at first, and then butadiene and styrene are charged simultaneously); (5) S-IS-I-B-I-IS-S(wherein butadiene is charged at first, and then isoprene and styrene are charged simultaneously); and (6) S-IS-I-BI-B-I-IS-S (wherein butadiene, isoprene and styrene are charged simultaneously). In the above formulae, S represents a polystyrene block, B represents a polybutadiene block, I represents a polyisoprene block, BI represents a tapered copolymer block derived from butadiene and isoprene, BS represents a tapered copolymer block derived from butadiene and styrene and IS represents a tapered copolymer block derived from isoprene and styrene.
When butadiene and styrene are charged simultaneously, only a pentablock copolymer represented by the formula S-BS-B-BS-S, which contains a tapered copolymer block derived from butadiene and styrene, can be obtained, due to the difference between the reactivity ratio of butadiene and that of styrene. If a polar modifier is charged while charging butadiene and styrene, the reactivity ratio of butadiene and that of styrene can be changed, and thus butadiene and styrene can be polymerized in a random manner, whereby obtaining a random butadiene/styrene copolymer block SBR.
BRIEF SUMMARY OF THE INVENTION
Based on the above polymer design, the present inventors truly realize the chemical compounding of random conjugated diene/monovinyl aromatic monomer copolymer rubbers and polyconjugated diene rubbers, by firstly synthesizing a rubber block selected from the group consisting of a homopolymer block derived from conjugated diene, a tapered copolymer block derived from conjugated dienes, a random copolymer block derived from conjugated dienes and combinations thereof, and then synthesizing a random copolymer block derived from conjugated diene and monovinyl aromatic monomer, in the presence of a multifunctional lithium based initiator, so as to obtain star-block interpolymers having in the same molecule both said random copolymer block and said rubber block. However, the conventional method for carrying out rubber compounding is to physically blend various rubbers in an open mill or an internal mixer, and thus, the chemically compounding method employed by the present inventors is simpler and the resultant effects are superior.
Therefore, the object of the present invention is to provide novel star-block interpolymers derived from conjugated diene and monovinyl aromatic monomer, which have in the same molecule both a random copolymer block derived from conjugated diene and monovinyl aromatic monomer and a rubber block selected from the group consisting of a homopolymer block derived from conjugated diene, a tapered copolymer block derived from conjugated dienes, a random copolymer block derived from conjugated dienes and combinations thereof, and hence possess excellent properties of the both kinds of rubbers, and can be used widely as elastomeric materials, for example, for preparing tires, especially as rubbers for making tire tread having excellent properties, such a reduced rolling resistance and an improved traction characteristic. The star-block interpolymers according to the present invention can also be further functionalized, for example, hydrogenated, epoxidated, hydroxylated, carboxylated, and the like, and furthermore, can be used to modify plastic materials by blending therewith.
Another object of the present invention is to provide processes for the preparation of the above star-block interpolymers, by which one can realize the chemical compounding in situ in a single reactor instead of physically blending.
Therefore, in one aspect, the present invention relates to star-block interpolymers having the following structure:
(X-Y)
n
-C
wherein X represents a random copolymer block derived from conjugated diene and monovinyl aromatic monomer;
Y represents a polyconjugated diene block;
C represents a residue derived from a multifunctional lithium based initiator; and
n represents the functionality of the initiator and has a value of not less than 3.
In another aspect, the present invention relates to processes for the preparation of the present star-block interpolymers by anionic polymerization.
In still another aspect, the present invention relates to use of the present star-block interpolymers as elastomeric materials.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in more detail as follows.
The term “conjugated diene” used in the present invention means any monomer having in its molecule conjugated double bonds, such as C
4
-C
6
conjugated dienes. The specific examples preferably include butadiene, isoprene, 1,3-pentadiene, 1,3-hexadiene, 2,3-dimethylbutadiene, and mixtures thereof, with butadiene and isoprene being more preferred. The term “monovinyl aromatic monomer” used in the present invention means any aromatic monomer carrying one vinyl substituent on its aromatic ring. The specific examples preferably include styrene or alkyl substituted styrenes such as vinyl toluene(including all isomers), &agr;-methylstyrene, 4-tert.-butylstyrene, 4-methylstyrene, 3,5-diethylstyrene, 3,5-di-n-butylstyrene, 4-n-propylstyrene, 4-dodecylstyrene and mixtures thereof, more preferably styrene, vinyl toluene, &agr;-methylstyrene and mixtures thereof, most preferably styrene.
In the star-block interpolymers according to the present invention, block X is a random copolymer block derived from conjugated diene and monovinyl aromatic monomer. It is preferred that the conjugated diene in block X is butadiene, isoprene or mixture thereof, with butadiene being more preferred. It is preferred that the monovinyl aromatic monomer in block X is styrene or alkyl substituted styrenes, with styrene being more preferred.
In block X, the content of 1,2- or 3,4-addition polymerization structure of the conjugated diene is preferably 6 to 80 percent by weight, more preferably 10 to 50 percent by weight, based on the total weight of the units derived from the conjugated diene in block X.
In block X, the content of the units derived from the monovinyl aromatic monomer is generally 10 to 50 percent by weight, preferably 15 to 35 percent by weight, based on the total weight of block X; and the content of the units derived from the conjugated diene is generally 50 to 90 percent by weight, preferably 65 to 85 percent by weight, based on the total weight of block X.
In the star-block interpolymers according to the present inven

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