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
1999-03-02
2001-06-05
Lipman, Bernard (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...
C525S332800, C525S332900, C525S333100, C525S333200, C525S339000
Reexamination Certificate
active
06242537
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a gel-free process for making functionalized polymers, primarily functionalized anionic polymers which are made using multi-lithium initiators. More particularly, this invention relates to a gel-free process for making polydiene diols.
BACKGROUND OF THE INVENTION
Functionalized anionically polymerized polymers of conjugated dienes and other monomers wherein the functionalization is terminal and/or internal are known. Particularly, U.S. Pat. No. 5,393,843 describes polybutadiene polymers having terminal functional groups. One of the methods described for making such polymers involves anionic polymerization utilizing a dilithium initiator such as the adduct derived from the reaction of m-diisopropenylbenzene with two equivalents of s-BuLi. Monomer is added to the initiator in hydrocarbon solution and anionic living polymer chains grow outwardly from the ends of the dilithium initiator. These polymers are then capped to form functional end groups as described in U.S. Pat. Nos. 4,417,029, 4,518,753, and 4,753,991. Of particular interest herein are terminal hydroxyl, carboxyl, sulfonate, and amine groups.
It has been observed that when the living polymer is reacted with the commonly available “capping” agents, the polymer in the hydrocarbon solution forms a gel. For purposes of this invention, a polymer gel is defined as a blend of a polymer and a hydrocarbon solvent that has a yield stress, that is, it will not flow unless it is acted on by at least some critical stress. A polymer gel as defined herein will require a significant application of force in order to initiate flow through an orifice. Of particular interest are gels that will not flow under the force of their own weight. The presence of gel that will not flow under the force of its own weight is readily detected by visual observation. This effect is observed by inverting a bottle containing the solution to see whether it flows to the bottom of the inverted flask. Gelled solutions will not readily flow to the bottom of the bottle.
The physical characteristics of these gels make them more difficult to handle in equipment which is designed for moving, mixing, or combining freely flowing liquids, i.e. materials without a significant yield stress. Pumps, reactors, heat exchangers, and other equipment that are normally used for making polymer solutions that can be characterized as viscous fluids are not typically suited to handling polymer gels. Thus, one would expect that processing equipment likely to be found at a manufacturing location that is designed to handle liquid polymer solutions, as defined above, would be ill suited to handling gels of this nature.
If the living carbon-alkali metal endgroups (chain ends) are first transformed to the “ate” complex (aluminate) by reaction with a trialkylaluminum compound, the addition of EO occurs nearly quantitatively, without the formation of gel. Addition of a trialkylaluminum compound can also dissipate a gel of this kind that has already formed. The molar ratio of the trialkyl aluminum compound to the polymer chain ends is generally at least 0.1:1, preferably 0.33:1 and most preferably 0.66:1 to 1:1 since this results in a freely flowing solution. Unfortunately, at the preferred aluminum levels, the hydrogenation activity of the Ni/Al catalysts that are often used in the hydrogenation of these polymers is poor. Substantially more catalyst and longer reaction time are required to reach an acceptable level of residual unsaturation in the trialkylaluminum-containing cements than in controls prepared in the absence of aluminum. The present invention provides a method whereby polymers using trialkylaluminum to mitigate the gel problem can be efficiently hydrogenated.
SUMMARY OF THE INVENTION
This invention relates to a gel-free process for making functionalized polymers. When multi-alkali metal initiators are used to make these polymers anionically, the process comprises anionically polymerizing at least one monomer with a multi-alkali metal initiator in a hydrocarbon solvent, functionalizing the polymer by adding to the polymer a capping agent that reacts with the ends of the polymer chains such that strongly associating chain ends are formed leading to formation of a polymer gel, adding a trialkyl aluminum compound to the polymer gel whereby the gel dissipates, optionally terminating the polymerization by addition of an alcohol, washing the polymer, terminated or not, with an aqueous acid, preferably mineral acid, solution, and hydrogenating the polymer with a hydrogenation catalyst. The concentration of the acid solution and the aqueous phase ratio (ratio of aqueous acid to polymer solution) are chosen so as to insure solubility of the extracted alkali metal and aluminum salts. If phosphoric acid is used, it is preferable to add a sufficient amount such that there is at least one mole of acid per mole of alkali metal and at least three moles of acid per mole of aluminum.
In a second embodiment, the present invention relates to a process for making such polymers which comprises anionically polymerizing them as described, adding to the polymer a trialkyl aluminum compound, and then adding the functionalizing reagent, optionally adding a terminating agent, and washing and hydrogenating the polymer as described above. In this second embodiment, the aluminum trialkyl may be added before or during polymerization or before or with the capping agent (i.e., before a gel can form-prior to any reaction of the alkali metal with the gel-forming functionality). In the first embodiment, a gel is formed and then removed. In the second embodiment, the gel never is formed because of the presence of the trialkyl aluminum compound.
DETAILED DESCRIPTION OF THE INVENTION
This invention relates to functionalized polymers and processes for avoiding gel formation, especially when such polymers are made by anionic polymerization using di- or multi-alkali metal, generally lithium, initiators. Sodium or potassium initiators can also be used. For instance, polymers which can be made according the present invention are those made from any anionically polymerizable monomer, especially including terminal and internal functionalized polydiene polymers, including random and block copolymers with styrene. Styrene copolymers hereunder can be made in the same manner as the polydiene polymers and can be random or block copolymers with dienes.
In general, when solution anionic techniques are used, copolymers of conjugated diolefins, optionally with vinyl aromatic hydrocarbons, are prepared by contacting the monomer or monomers to be polymerized simultaneously or sequentially with an anionic polymerization initiator such as group IA metals, their alkyls, amides, silanolates, naphthalides, biphenyls or anthracenyl derivatives. It is preferred to use an organo alkali metal (such as lithium or sodium or potassium) compound in a suitable solvent at a temperature within the range from about −150° C. to about 150° C., preferably at a temperature within the range from about −70° C. to about 100° C. Particularly effective anionic polymerization initiators are organo lithium compounds having the general formula:
RLi
n
wherein R is an aliphatic, cycloaliphatic, aromatic or alkyl-substituted aromatic hydrocarbon radical having from 1 to about 20 carbon atoms and n is an integer of 1 to 4. The organolithium initiators are preferred for polymerization at higher temperatures because of their increased stability at elevated temperatures.
Functionalized polydiene polymers, especially terminally functionalized polybutadiene and polyisoprene polymers, optionally as copolymers, either random or block, with styrene, and their hydrogenated analogs are preferred for use herein. Especially preferred are polybutadiene diols. Such polymers are made as generally described above. One process for making these polymers is described in U.S. Pat. No. 5,393,843, which is herein incorporated by reference.
Using a polydiene diol as an example, butadiene is anionically polymerized using a di
Bening Robert Charles
Diaz Zaida
Donaho Charles Roy
Goodwin Daniel Earl
Wilkey John David
Haas Donald F.
Lipman Bernard
Shell Oil Company
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