Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1996-04-03
2002-10-08
Lipman, Bernard (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S163000, C526S169200
Reexamination Certificate
active
06462153
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a novel catalyst composition and to the polymerization of vinyl chloride using that composition. In particular, it relates to a catalyst composition that is a mixture of a vanadyl (V) catalyst and an alkyl aluminum cocatalyst.
Vinyl chloride monomer (VCM) is commercially polymerized to produce polyvinyl chloride (PVC) using peroxide initiators. Because peroxides are unstable and can even be explosive, they must be handled and stored very carefully at a low temperature, which complicates and adds to the cost of the manufacturing process. Moreover, elevated temperatures are usually required in polymerization reactions initiated by peroxides (50-80° C.), which could deteriorate the properties of the product. Besides, the free-radical nature of the traditional polymerization process implies that the product properties, like tacticity, molecular weight, and polydispersity, are not influenced in any way by the structure or composition of the radical initiator. Efforts have been made to find non-peroxide catalysts for polymerizing vinyl chloride. For example, U.S. Pat. Nos. 3,775,391, 3,786,032, and 4,129,702 disclose the polymerization of vinyl or vinylidene halides using as an initiator a transition metal compound, such as vanadium oxytrichloride, and an organoaluminum or organozinc compound, such as triethyl aluminum, including a ligand derived from an oxime or a hydroxy ester. These catalysts seem to be highly specific and, like most catalysts, small chemical variations thereof are nonfunctional.
SUMMARY OF THE INVENTION
We have discovered a novel organometallic catalyst composition that is useful for polymerizing vinyl chloride monomer alone or with comonomers. The catalyst composition of this invention is a mixture of a vanadyl (V) catalyst and an alkyl aluminum cocatalyst. Unlike peroxide initiators, which require elevated temperatures, the organometallic catalyst composition of this invention can be used not only at high temperatures, but also at ambient or below ambient temperatures. Besides, in the polymerization process using the new catalyst composition, the molecular weight of the PVC can be easily controlled through the catalyst concentration. Also, the catalyst composition is not explosive and the components can be stored at room temperature. The catalyst compositions of this invention can be used in solution, bulk, or vapor phase polymerization of vinyl chloride, the last two processes being the most attractive for economical reasons.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The catalyst composition of this invention is a mixture of a vanadyl (V) catalyst and an alkyl aluminum cocatalyst.
The vanadyl (V) catalyst has the general formula
where R is a group containing 1 to 14 carbon atoms and X is halogen or OR. Preferably, R is alkyl from C
1
to C
4
and X is OR because those catalysts are more readily available. Some of the catalysts where R is alkyl, such as vanadyl (V) triisopropoxide, are commercially available. Catalysts that can not be purchased can be easily made by reacting vanadium trihalide oxide with 1, 2, or 3 moles of an alcohol, a phenol, a carboxylic acid, an enolizable ketone, or their salts, a reaction that proceeds readily at room temperature. A vanadyl (V) catalyst can also be prepared by reacting vanadium trihalide oxide with a compound containing an oxirane ring. For example, one mole of vanadium trichloride oxide can be reacted with 1, 2, or 3 moles of ethylene oxide:
where p is 1, 2, or 3. This reaction proceeds readily at room temperature in 1 to 24 hours. Examples of suitable compounds having an oxirane ring include ethylene oxide, propylene oxide, epichlorohydrin, cyclohexene oxide, and cyclooctene oxide. The preferred vanadyl (V) catalyst is the reaction product of vanadium trichloride oxide and cyclohexene oxide because it is readily available and works well.
The alkyl aluminum cocatalyst has the general formula
(R′)
m
Al(X′)
3−m
where each R′ is independently selected from alkyl from C
1
to C
10
, X′ is halogen, —OR
1
, —OC(═O)R
1
, —OAl(R′)
2
or (OAlR′)
n
, —OAl(R′)
2
, R
1
is alkyl from C
1
to C
10
, haloalkyl from C
1
to C
10
, alkoxyalkyl where each alkyl group is independently selected from C
1
to C
10
, or aryl from C
6
to C
14
, m is 1 or 2, and n is 1 to 100. Preferably, R′ is alkyl from C
1
to C
4
, X′ is halogen, preferably chlorine, R
1
is alkyl from C
1
to C
4
, most preferably ethyl, m is 2, and n is 1 to 10, because those compounds are commercially available. Examples of alkyl aluminum compounds that can be used as cocatalysts include diethyl aluminum ethoxide, diethylaluminum chloride, ethylaluminum dichloride, dimethylaluminum chloride, diethylaluminum propionate, and diethylaluminum benzoate. The preferred alkyl aluminum cocatalyst is diethyl aluminum ethoxide because it is readily available and gives good results. Many of the alkyl aluminum compounds included within the scope of the above formula are commercially available. Alkylaluminum cocatalysts where X′ is OR
1
can be easily prepared by reacting a trialkylaluminum compound with an alcohol or a phenol. Similarly, compounds where X′ is OC(═O)R
1
can be easily made by reacting a trialkylaluminum compound with an aliphatic or aromatic carboxylic acid:
Compounds where X′ is —OAl(R′)
2
can be prepared by reacting two moles of trialkyl aluminum with one mole of water. For example, if two moles of triethyl aluminum are reacted with one mole of water the following alkyl aluminum compound is believed to be produced, where “Et” is ethyl:
Similarly, compounds where the X′ group is —(OAlR′)
n
OAl(R′)
2
can be made by reacting one mole of trialkyl aluminum with one mole of water. For example, if one mole of trialkyl aluminum is reacted with one mole of water, the following reaction occurs:
where q can be 1 to 100.
The molar ratio of the alkyl aluminum cocatalyst to the vanadyl (V) catalyst in the catalyst composition can vary from about 0.5 to about 15, but is preferably about 1.5 to about 4 as the optimum seems to be at about 2. If less of the alkyl aluminum cocatalyst is used the polymerization is less efficient and more of the alkyl aluminum cocatalyst results in no significant improvement.
The catalyst composition can be prepared by simply mixing together the alkyl aluminum cocatalyst and the vanadyl (V) catalyst in the desired proportion. This can be accomplished before the catalyst composition contacts the monomer or the catalyst and cocatalyst can be added separately to the monomer. For convenience in laboratory experiments, it is sometimes desirable to use a solvent such as hexane, toluene, or tetrahydrofuran (THF). Preferably, if a solvent is desired vinyl chloride monomer itself is used as the solvent so that problems of disposing of a solvent are avoided.
The catalyst composition is preferably supported, particularly if it is used for bulk or vapor phase polymerization. The support can be an insoluble particulate such as alumina, silica, clay, various other inorganic oxides, or polyvinyl chloride; fumed silica or other small particle size silica is preferred. The finely divided support can be mixed with a solution of the catalyst and the solvent removed by filtration, decanting, or evaporation, which deposits the catalyst on the support. The support holds the catalyst composition and prevents it from entering the solution phase. The support also controls the morphology of the polymer so that the polymer is produced as small particles, rather than in large clumps.
The catalyst composition is generally used in an amount of about 0.01 to about 50 mmole vanadium per mole of monomer; less is usually ineffective and more is unnecessary and may be deleterious to the stability of the PVC. Polymerization can occur within a temperature range of −40 to 80° C. and within a pressure range of 0 to 200 psig (0 to 1500/KPa). Most of the unsupported catalyst compositions within the scope of this inv
Nagy Sandor
Tyrell John
Fuerle Richard D.
Lipman Bernard
Occidental Chemical Corporation
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