Solution of dilithium polymerization initiator

Details Solution of dilithium polymerization initiator Solution of dilithium polymerization initiator

2002-01-10

2003-09-02

Teskin, Fred (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S173000, C526S335000, C525S331900, C525S332900, C502S157000, C260S66500B

Reexamination Certificate

active

06613858

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a novel dilithium polymerization initiator solution useful for the production of a block copolymer having narrow molecular weight distribution and excellent symmetric property or a telechelic polymer having, equally at both terminals thereof, a functional group, and relates to a production process thereof.
BACKGROUND ART
An attempt has long been made to polymerize a block copolymer having an SBS structure or SIS structure by using a dilithium compound as a polymerization initiator. This attempt has not always lead to practical industrial production. One of the reasons resides in that a polymerization initiator cannot be constituted of a dilithium compound alone. A polymer obtained using a polymerization initiator solution composed of many components involves such a drawback as inferior mechanical properties for example tensile strength, because such a polymer inevitably has a widened molecular weight distribution, and because polymerization proceeds only at one of the polymerization starting points of the dilithium compound, thereby making the resulting polymer to inevitably contain a copolymer having a diblock structure. Another reason resides in that in order to heighten a solubility of the dilithium compound in a nonpolar solvent and moreover to prepare a polymerization initiator as another-component free as possible, use of a sufficient amount of a polar substance containing a nitrogen or oxygen atom is indispensable during the preparation step of the polymerization initiator. This imposed a limitation on the bonding structure of a polymer in the subsequent polymerization step of a conjugated diene, resulting in the production of only a polymer having a large 1,2-vinyl-bound content. In addition, the polymer solution thus obtained cannot be provided for the subsequent reaction without any convenience. For example, upon hydrogenation reaction of the polymer, a tertiary amine compound, which is a nitrogen-containing compound among such polar substances, causes damage to a catalyst for hydrogenation of a conjugated diene polymer so that the polymer solution cannot be provided as is for hydrogenation.
For example, JP-B-63-5403 (The term “JP-B” as used herein means an “examined Japanese patent publication”) discloses a process for producing a polymer having narrow molecular weight distribution by using a dilithium polymerization initiator. JP-B-1-53681 or JP-B-6-67990 discloses a dilithium polymerization initiator for obtaining a polymer having narrow molecular weight distribution. The techniques disclosed in them are for obtaining a dilithium polymerization initiator by reacting a monolithium compound with 1,3-diisopropenylbenzene in the presence of a tertiary amine.
JP-A-8-48709 (EP690075A1) (The term “JP-A” as used herein means an “unexamined Japanese patent application”), discloses an improvement of the above-described polymerization process using a dilithium polymerization initiator. As the polymerization initiator, described is an &agr;,&ohgr;-dilithiopoly(conjugated diene) which is an oligomer obtained by reacting a monolithium compound with 1,3-diisopropenylbenzene in the presence of a tertiary amine and then reacting with a small amount of a conjugated diene. The object and means of the invention described above are to provide a polymer having narrow molecular weight distribution by forming an &agr;,&ohgr;-dilithiopoly(conjugated diene) from the dilithium compound thus obtained and a small amount of the conjugated diene and carrying out polymerization using this conjugated diene oligomer as a polymerization initiator. This process needs complex steps. A number of patent official gazettes and references were introduced in it as a prior art.
In the above-described prior art, a tertiary amine is used as an essential component so that, as described above, the polymer solution cannot be provided for hydrogenation reaction as is. In addition, many restrictions are imposed on it, for example, use of an oligomer polymerization initiator to control the initiation of the polymerization reaction, a decrease in the amount of the conjugated diene at the initial stage of the reaction and use of the polymerization initiator at a predetermined concentration.
“Macromolecules, 27, 2219-2255 (1994)” discloses a lithium polymerization initiator synthesized using sec-BuLi which initiator is soluble in toluene, cyclohexane or n-hexane and that a block copolymer can be prepared using this polymerization initiator. This system free of a polar substance, however, has a low polymerization rate and moreover, a polymer obtained using it does not have sufficiently narrow molecular weight distribution.
It is already known that use of durene, which is a &pgr; electron donor, in anionic polymerization changes the polymerization rate of styrene. According to J. of Polymer Science, Part A, 3, 1037-1044 (1965), when the molar ratio of durene to an active terminal Li is 1:5, the polymerization rate of styrene becomes about twice the rate of a durene-free case, suggesting the formation of a &pgr; complex by durene. It however includes neither an attempt to prepare a dilithium polymerization initiator by using durene nor an attempt to polymerize a conjugated diene by positively using a dilithium polymerization initiator prepared using durene in anionic polymerization.
An object of the present invention is to provide a dilithium polymerization initiator solution which is useful for the preparation of a block copolymer having narrow molecular weight distribution and excellent symmetric property or the preparation of a telechelic polymer having, equally at both terminals thereof, a functional group, and which is free of a nitrogen- or oxygen-containing polar substance. Another object of the invention is to prepare a (co)polymer having narrow molecular weight distribution by using the above-described polymerization initiator solution as it is. A further object of the invention is to obtain, when a conjugated diene is employed as a monomer, a polymer having a low content of a 1,2-bound structure in the conjugated diene polymer portion. A still further object of the invention is to obtain a novel telechelic polymer by reacting the (co)polymer with a functional-group-imparting compound.
DISCLOSURE OF THE INVENTION
The present inventors have carried out an extensive investigation with a view toward overcoming the above-described drawbacks of a dilithium polymerization initiator solution and production of a (co)polymer using the solution. As a result, they succeeded in the completion of the following invention.
In one aspect of the invention, there is thus provided a polymerization initiator solution which comprises a dilithium polymerization initiator having an average number of functional groups of from 1.8 to 2.0/molecule and a solvent selected from aliphatic hydrocarbon compounds and alicyclic compounds, and which is free of a polar substance and a conjugated diene.
In another aspect of the invention, there is also provided a production process of the above-described polymerization initiator solution, which comprises reacting, in a solvent selected from aliphatic hydrocarbon compounds and alicyclic compounds, a mono-organo lithium compound and a compound having two vinyl groups directly bonded to a benzene ring in the presence of at least one compound selected from benzene compounds substituted with at least three alkyl groups and 1,1-diphenyl-substituted ethylene compounds.
In a further aspect of the invention, there is also provided a production process of the above-described polymerization initiator solution, wherein the benzene compound substituted with at least three alkyl groups is 1,2,4,5-tetramethylbenzene (durene) or hexamethylbenzene and the 1,1-diphenyl-substituted ethylene compound is tetraphenylethylene.
In a still further aspect of the invention, there is also provided a production process of the above-described polymerization initiator solution, wherein the compound having two vinyl groups directly bonded to a benzene ring is 1,3-diisopropenylbenz

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