Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1992-05-12
2002-04-02
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...
C526S308000, C526S348000, C526S348500, C526S348600
Reexamination Certificate
active
06365687
ABSTRACT:
This invention relates to a process for polymerizing unsaturated hydrocarbons of the formula
CH
2
═CHR
in which R is a saturated aliphatic, an alicyclic or an aromatic radical, alone, in mixture with one another, or in mixtures with small amounts, up to about 5%, of a monomer polymerizable therewith.
Uniquely, the initial polymerization products obtained by the present method are mixtures of linear, head-to-tail amorphous and crystalline polymers having no branches longer than R. The polymers can be separated from the polymerizate by fractional dissolution. The crystalline polymers may comprise as nigh as 30% or even up to 55% of the mixture and have high molecular weights and fiber forming properties. The amorphous polymers may also have relatively high molecular weights and may exhibit rubber-like properties.
It has been proposed, in the Belgian patent No. 533,362, to polymerize ethylene to polymers of high molecular weight of the order of 300,000 up to 2,000,000 or more, by using as reaction initiators, agents obtained by reacting a catalytic heavy metal compound and a catalytic metal alkyl compound.
The catalytic heavy metal compounds we use in preparing the catalyst for the polymerization of the alpha-olefins to polymers having the steric structures described below are halides of heavy metal selected from the sub-group of Groups IV to VI of the Periodic Table, including thorium, and uranium, i.e., halides of the elements of titanium, zirconium, hafnium, thorium, vanadium, tantalum, niobium, chromium, molybdenum, tungsten and uranium. These are metals belonging to Groups IVa, Va and VIa of the Mendeleeff Periodic Table.
The catalytic metal alkyl compounds we use in preparing our catalyst are alkyl compounds of elements selected from the group forming the 2nd and 3rd columns of the Periodic Table, i.e., beryllium, magnesium, zinc, cadmium and other elements of the 2nd group, as well as boron, aluminum and other elements of the 3rd group.
The valences of the aforesaid elements are linked to the same or different alkyl radicals such as ethyl, propyl, butyl, etc. One valence of the element may be satisfied by halogen, or alkoxy radicals.
Although, as stated, the polymerization aids obtained by reacting heavy metal compounds and metal alkyl compounds in a solvent inert to the polymer to be formed, such as a saturated aliphatic hydrocarbon, were found useful in the production of high polymers of ethylene, it was not apparent that those agents would be useful in the polymerization of the unsaturated hydrocarbons containing the vinyl group.
Processes and polymerization promoters that are useful for producing polyethylene of high molecular weight are not necessarily useful for producing high molecular weight polymers of the higher homologues of ethylene, such as, for instance, propylene.
In the past, it has been found that when various promoters or catalysts useful in producing high molecular weight polyethylene have been used with the higher homologues, for instance only dimers, trimers or tetramers forming light oils, or somewhat higher polymers comprising more or less viscous lubricating oils.
The products obtained by polymerizing the higher ethylene homologues by processes known in the art generally consist of mixtures of polymeric homologues containing variously branched isomers. The higher the temperature used, the smaller the degree of polymerization. But even when the known processes are carried out at relatively low temperature the products obtained are still mainly liquids or mixtures of liquids and amorphous products in which the liquid component is present in substantial amount.
Prior to this invention, it has been considered that polymerization of olefins CH
2
═CHR, i.e., olefins in which one of the hydrogen atoms of a CH
2
group is replaced by a CH
3
group, such as propylene, results in non-crystalline polymers. Thus, it has been stated in the literature (“Fibers from Synthetic Polymers”, Rowland Hill, Ed., Elsvier Publishing Co., 1953, p. 319) that:
“Polymers of olefins in which one of. the hydrogen atoms of a CH
2
group is replaced by a CH
3
group, are usually non-crystalline, owing to stereochemical irregularity.”
It was believed, further, that the low crystallinity exhibited by polyvinyl chloride for example, was due to the fact that over some short sections of the polymer main chain the configurations of the tertiary carbon atoms of the CHC1 groups are alternately levo and dextro.
Furthermore, it was assumed that, since the methyl group is similar in size to the chlorine atom, it was to be expected that polymers like polypropylene in which one could assume that tertiary asymmetric carbon atoms of the main chain having different steric configurations would occur in a random distribution, would be non-crystalline, owing to the stereochemical irregularity. (“Fibers Prom Synthetic Polymers”, supra, p. 235, Hill & Walker, Jr. of Polymer Science, Vol. III, 1948, p. 609).
It has been found, also, that even when ethylene is polymerized with the aid of the special promoters obtained by reaction of heavy metal and metal alkyl compounds, in the ratios proposed for promoting ethylene.
The slowness to polymerize exhibited by the higher olefins is not overcome by merely increasing the polymerization temperature, since when the special aids described herein are used, temperatures which promote the growth of the polymer chain, bound in the form of a metallo-organic compound, without appreciably favoring its disassociation into low molecular weight olefins must be used.
In view of the foregoing, it could not be predicted, from the work with ethylene, that our polymerization agents would be useful for the production of higher molecular weight polymers of the vinyl hydrocarbons of formula CH
2
═CHR as defined herein.
Surprisingly, we have now foud that, in fact it is possible to obtain high molecular weight polymers of propylene and other monomeric vinyl hydrocarbons of that type, i.e., containing more than three carbon atoms per molecule and including styrene, and to produce the polymers at commercially acceptable reaction rates and in good yields, with the aid of the aforesaid initiators if the initiator is prepared from the heavy metal halide and metal alkyl compound in appropriate molar ratios.
In accordance with the invention, the new polymerization products are obtained by polymerizing monomeric material comprising at least one of the vinyl hydrocarbons containing three or more carbon atoms per molecule in the presence of polymerization aids obtained by reacting the heavy metal halide and metal alkyl compound in molar ratios such that the metal alkyl component is not more than ten times the heavy metal halide and is preferably less than five times the heavy metal halide, as will be seen from the examples given hereinafter. The catalyst is the reaction product of (a) a chloride of titanium with (b) an alkyl aluminum compound in which at least two of the valences of aluminum are satisfied by alkyl groups, and in which the third valence can be satisfied by alkyl or halide. The catalyst may also be the reaction product of (a) a chloride of titanium with (b) an aluminum trialkyl compound, in which the alkyl groups have up to four carbons each. To obtain a highly active catalyst, and effect smooth polymerization of the olefin, it is important to carry out the reaction between the heavy metal halide and the metal alkyl compound in an inert solvent preferably a saturated hydrocarbon solvent. This insures that the reaction proceeds smoothly, without violence, and without a strong temperature increase which would be considerable if the catalyst were used without prior dilution thereof.
Solvents suitable for use in preparing the polymerization catalyst are paraffinic hydrocarbons such as, for instance, a light gasoline, (substantially free of olefinic bonds), n-heptane, iso-octane, and other substances preferably of the non-aromatic type. However, benzene has also been used.
The solvents selected should preferably have boiling points lower than 150° C. and not swell
Mazzanti Giorgio
Natta Giulio
Pino Piero
Basell Poliolefine S.p.A.
Teskin Fred
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