Iron-based catalyst for producing high-vinyl polybutadiene

Details Iron-based catalyst for producing high-vinyl polybutadiene Iron-based catalyst for producing high-vinyl polybutadiene

2002-01-18

2003-06-10

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...

C526S169100, C526S335000, C502S117000, C502S121000, C502S155000, C502S162000

Reexamination Certificate

active

06576725

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to an iron-based catalyst composition for preparing high-vinyl conjugated diene polymers.
BACKGROUND OF THE INVENTION
High-vinyl polybutadiene, also called 1,2-polybutadiene, is typically characterized by having greater than about 60% of its monomeric units in the 1,2-(vinyl) configuration. Two forms of commercially useful high-vinyl polybutadiene include syndiotactic 1,2-polybutadiene and atactic 1,2-polybutadiene.
Syndiotactic 1,2-polybutadiene has a stereoregular structure in which the side-chain vinyl groups are located alternately on the opposite sides in relation to the polymeric main chain. Due to its stereoregular structure, syndiotactic 1,2-polybutadiene is a crystalline thermoplastic resin and has a melting temperature within the range of about 80° C. to about 215° C., depending on the 1,2-linkage content and syndiotacticity. For processability reasons, it is generally desirable for syndiotactic 1,2-polybutadiene to have a melting temperature of less than about 190° C.
Syndiotactic 1,2-polybutadiene uniquely exhibits the properties of both plastics and rubber, and therefore it has many uses. For example, films, fibers, and various molded articles can be made from syndiotactic 1,2-polybutadiene. It can also be blended into and co-cured with natural or synthetic rubbers in order to improve the properties thereof. Various transition metal catalyst systems based on cobalt, titanium, vanadium, chromium, and molybdenum for preparing syndiotactic 1,2-polybutadiene have been reported. The majority of these catalyst systems, however, have no practical utility because they have low catalytic activity or poor stereoselectivity, and in some cases they produce low molecular weight polymers or partially crosslinked polymers unsuitable for commercial use.
Atactic 1,2-polybutadiene has a stereoirregular structure in which the side-chain vinyl groups are located randomly on the opposite sides in relation to the polymeric main chain. Due to its stereoirregular structure, atactic 1,2-polybutadiene is an amorphous rubbery elastomer and is typically characterized by having a glass transition temperature from about −50° C. to about 0° C. without a readily detectable melting temperature. Atactic 1,2-polybutadiene is utilized in a variety of applications. For example, atactic 1,2-polybutadiene is useful in tire tread compositions because it provides a good balance of traction and rolling resistance.
Atactic 1,2-polybutadiene is commonly produced by anionic polymerization utilizing alkyllithium initiators which are modified with Lewis base modifiers such as chelating diamines, ethers, tertiary amines, acetals, ketals, and compounds of similar structures. The vinyl content of polybutadiene prepared utilizing these Lewis base modifiers decreases drastically as the polymerization temperature is increased. For this reason, it is difficult to prepare atactic 1,2-polybutadiene at high polymerization temperatures utilizing Lewis base modifiers. However, since high polymerization temperatures generally promote a higher polymerization rate, it is often desirable to utilize moderately high temperatures in commercial polymerizations in order to maximize productivity as well as to reduce the production cost.
Because syndiotactic 1,2-polybutadiene and atactic 1,2-polybutadiene are useful products and the catalysts known heretofore in the art have many shortcomings, it would be advantageous to develop new and significantly improved catalyst compositions that have high catalytic activity and stereoselectivity for polymerizing 1,3-butadiene into syndiotactic 1,2-polybutadiene or atactic 1,2-polybutadiene.
SUMMARY OF THE INVENTION
In general the present invention provides a catalyst composition that is the combination of or the reaction product of ingredients comprising an iron-containing compound, an organomagnesium compound, and an &agr;-acylphosphonate diester.
The present invention also includes a catalyst composition formed by a process comprising the step of combining an iron-containing compound, an organomagnesium compound, and an &agr;-acylphosphonate diester.
The present invention further provides process for forming conjugated diene polymers comprising the step of polymerizing conjugated diene monomers in the presence of a catalytically effective amount of a catalyst composition formed by combining an iron-containing compound, an organomagnesium compound, and an &agr;-acylphosphonate diester.
Advantageously, the catalyst composition of the present invention has very high catalytic activity and stereoselectivity for polymerizing conjugated diene monomers such as 1,3-butadiene. This activity and selectivity, among other advantages, allows conjugated diene polymers such as syndiotactic 1,2-polybutadiene and atactic 1,2-polybutadiene to be produced in high yields with low catalyst levels after relatively short polymerization times. In addition, the iron-containing compounds that are utilized in the catalyst composition of this invention are generally stable, inexpensive, relatively innocuous, and readily available. Further, the catalyst composition of this invention has high catalytic activity in a wide variety of solvents including the environmentally-preferred nonhalogenated solvents such as aliphatic and cycloaliphatic hydrocarbons. Furthermore, this catalyst composition is operational over a wide range of polymerization temperatures. Still further, the performance characteristics of the catalyst composition can be readily controlled by changing the steric and electronic characteristics of the organic substituents of the &agr;-acylphosphonate diester.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
The catalyst composition is formed by combining (a) an iron-containing compound, (b) an organomagnesium compound, and (c) an &agr;-acylphosphonate diester. In addition to the three catalyst ingredients (a), (b), and (c), other organometallic compounds or Lewis bases can also be added, if desired.
Various iron-containing compounds or mixtures thereof can be employed as ingredient (a). Iron-containing compounds that are soluble in a hydrocarbon solvent such as aromatic hydrocarbons, aliphatic hydrocarbons, or cycloaliphatic hydrocarbons are advantageously employed. Hydrocarbon-insoluble iron-containing compounds, however, can be suspended in the polymerization medium to form the catalytically active species and are therefore also useful.
The iron atom in the iron-containing compounds can be in various oxidation states including but not limited to the 0, +2, +3, and +4 oxidation states. Divalent iron compounds (also called ferrous compounds), wherein the iron atom is in the +2 oxidation state, and trivalent iron compounds (also called ferric compounds), wherein the iron atom is in the +3 oxidation state, are generally preferred. Suitable iron-containing compounds include, but are not limited to, iron carboxylates, iron organophosphates, iron organophosphonates, iron organophosphinates, iron carbamates, iron dithiocarbamates, iron xanthates, iron &bgr;-diketonates, iron alkoxides or aryloxides, iron halides, iron pseudo-halides, iron oxyhalides, and organoiron compounds.
Suitable iron carboxylates include iron(II) formate, iron(III) formate, iron(II) acetate, iron(III) acetate, iron(II) acrylate, iron(III) acrylate, iron(II) methacrylate, iron(III) methacrylate, iron(II) valerate, iron(III) valerate, iron(II) gluconate, iron(III) gluconate, iron(II) citrate, iron(III) citrate, iron(II) fumarate, iron(III) fumarate, iron(II) lactate, iron(III) lactate, iron(II) maleate, iron(III) maleate, iron(II) oxalate, iron(III) oxalate, iron(II) 2-ethylhexanoate, iron(III) 2-ethylhexanoate, iron(II) neodecanoate, iron(III) neodecanoate, iron(II) naphthenate, iron(III) naphthenate, iron(II) stearate, iron(III) stearate, iron(II) oleate, iron(III) oleate, iron(II) benzoate, iron(III) benzoate, iron(II) picolinate, and iron(III) picolinate.
Suitable iron organophosphates include iron(II) dibutyl phosphate, iron(III) dibutyl phosphate, iron(II) dip

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