Process for metalating halogenated polyolefins

A process for metalating a halogenated polyolefin so that only a very low percentage of the halogen originally present in the halogenated polyolefin is actually reacted during the process. The process comprises adding a solvated transmetalating organometallic compound to a cement mix of a halogenated polyolefin and a solvent. The transmetalating organometallic compound is present in the reaction in a molar amount less than the molar amount of the halogen content of the halogenated polyolefin. The reaction temperature is below 0.degree. C.

BACKGROUND OF THE INVENTION 
Metalation, especially lithiation, of halogenated polyolefins has long been 
recognized to yield useful intermediates. These intermediates can be used 
to produce graft copolymers, functionalized halogenated polyolefins and 
cross-linked copolymers. 
One recognized process for achieving the subject metalation comprises 
reacting a low molecular weight lithium organic compound and a halide 
derivative of polyethylene or polypropylene. This reaction can be 
represented by the following: 
##STR1## 
wherein R is a low molecular weight hydrocarbon radical, such as butyl, 
and X is a halogen, such as Cl. The lithium organic compound is provided 
in a molar amount about four times the molar content of the halogen in the 
polyolefin derivative. Th polyolefin derivative is added to the lithium 
organic compound which is at -20.degree. C. After addition, the 
temperature of the reaction mix is raised to 50.degree. C. to complete the 
desired reaction. The lithium organic compound is provided in a solvent 
such as heptane while the polyolefin derivative is solvated in anhydrous 
tetrahydrofuran for participation in the reaction. It is reported that 
there are two competing reactions, i.e., the Wurtz reaction and 
dehydrohalogenation. It is also possible that a third competing reaction, 
that is, alkylation of the polyolefin derivative, may also occur. These 
competing reactions are so significant that it is estimated that only 
about 22% of the halide reacted is replaced by lithium. The use of the 
large excess of lithium organic compound is reported to be necessary to 
achieve even this level of metalation. See: "Chemical Conversions of 
Halogenated Polyolefines Caused by Organo-Lithium Compounds", N. A. Plate 
et al, Vysokomol. soyed. 8: No. 9, pp. 1562-1567 (1966); "The Role of 
Chemico-Structural Effects in the Modification of Polymers", N. A. Plate, 
Vysokomol. soyed. A10: No. 12, pp. 2650-2661 (1968); and "Chemical 
Transformations and Catalytic Activity of Macromolecular Polylithium 
Compounds Polymerization", N. A. Plate et al, J. Polymer Sci.: Part C, No. 
22, pp. 547-568 (1969). 
Due to the competing Wurtz and dehydrohalogenation reactions, the resultant 
lithiated polymer product is not, strictly speaking, the HC-Li product 
shown by the above reaction but is rather a lithiated polymer which is 
cross linked, due to the Wurtz reaction, and has numerous unsaturated 
sites, due to the dehydrohalogenation reaction. Since an excess of lithium 
organic compound is used, the percentage of halogen sites involved in 
cross-linking, dehydrohalogenation and lithiation will be high, i.e., 40% 
to 70%. The high degree of cross-linking in the lithiated polymer product 
should evidence itself in the desired final product, be it a graft 
copolymer or a functionalized halogenated polyolefin, by rendering the 
final product more brittle and hard. Further, the loss of so many halide 
sites to dehydrohalogenation and lithiation will change the physical 
properties of the lithiated polymer product so that it will be more like a 
polyolefin than a halogenated polyolefin. For example, the elasticity 
exhibited by a chlorinated polyethylene starting material will be reduced 
in the more polyethylene-like lithiated polymer product. The greater the 
number of halogen sites used, the more polyolefin-like will be the 
lithiated polymer product. 
Since a purpose of metalating a halogenated polyolefin is to ultimately 
yield a graft copolymer or a functionalized polymer having those 
properties which would be expected to be contributed by the starting 
halogenated polyolefin, the obtainment of a metalated more polyolefin-like 
product, due to the required use of an excess of metalating compound, is a 
definite drawback of this prior art process. Furthermore, the use of an 
excess of metalating compound also insures the presence, at reaction end, 
of unreacted metalating compound which, because of its high reactivity, 
can interfere with subsequent grafting or functionalization procedures. 
Still another drawback is that the metalating compounds are expensive and 
thus the required use of an excess of these compounds in the process makes 
the process less desirable from an economic standpoint. 
Therefore, it is an object of the below described invention to provide a 
process for the metalation of halogenated polyolefins which process uses a 
metalating compound in a molar amount which is less than the molar amount 
of the halogen in the halogenated polyolefin and which, as a result, is 
capable of producing a metalated halogenated polyolefin which has had a 
low percentage of its halogen sites involved in cross-linking, 
dehydrohalogenation and metalation. 
THE INVENTION 
This invention relates to a process for metalating a halogenated polyolefin 
which comprises adding a solvated transmetalating organometallic compound 
to a cement mix of a halogenated polyolefin and a solvent, wherein the 
transmetalating organometallic compound is present in a molar amount less 
than the molar amount of the halogen content of the halogenated 
polyolefin. This process occurs under anhydrous conditions and at a 
temperature within the range of from about 0.degree. C. to about 
-80.degree. C. Halogen utilization by metalation, dehydrohalogenation, 
cross-linking, etc., is only from about 1 to about 20 percent of the 
halogen originally present in the halogenated polyolefin. Thus, the 
metalated halogenated polyolefin maintains most of its original physical 
properties for contribution to the final graft copolymer or functionalized 
polymer product. Interestingly, the use of less than a stochiometric 
amount of solvated transmetalating organometallic compound did not deprive 
the metalated sites on the polyolefin of their proportional share with 
regards to the dehydrohalogenation and cross-linkage sites--indeed, the 
percentage of the total halide reacted which was replaced by the metal was 
within the range of from about 15 to about 30%. This would not be expected 
in view of prior art teachings which show that an excess of metalating 
compound and raised reaction temperatures are needed to drive the 
before-illustrated metalation reaction to the right. Further, since the 
process of this invention utilizes most, if not all, of the metalating 
compound, there is little remaining in the reaction mix to hinder or 
interfere with subsequent grafting or functionalization procedures. 
By halogenated polyolefin, it is meant those polyolefins which are 
halogenated with chlorine, bromine or iodine. Fluorinated polyolefins are 
not believed suitable for the process of this invention due to their 
non-reactivity. The chlorinated and brominated polyolefins are preferred 
due to their ready availability and stability. Of these two, the 
chlorinated polyolefins are most preferred as the physical properties 
which they contribute, even after metalation, to the finally produced 
graft copolymers and functionalized polymers are highly desirable from a 
commercial standpoint. The molecular weight and degree of halogenation of 
the polyolefin are important as they are at least partially determinative 
of the solubility of the halogenated polyolefin in the solvent to yield 
the cement mix. High solubility is desired as it insures reactive access 
to the halogenated polymer chains by the transmetalating organometallic 
compound. For example, it has been found, for chlorinated polyethylene, 
that the chlorine content should not exceed 60 weight percent. For best 
solubility, those chlorinated polyethylene polymers which contain from 
about 34 to about 45 weight percent chlorine are most highly preferred. 
For other halogenated polyolefins, the suitability for any particular 
degree of halogenation can best be determined empirically. 
The polyolefin constituent of the halogenated polyolefin can generally be 
defined as one having an olefin repeating unit containing from about 2 to 
about 8 carbon atoms and having one or more double bonds. The polyolefin 
can be a long chain polymer so long as the halogenated polyolefin is 
soluble in the ether-containing solvent. For example, if the polyolefin is 
polyethylene, it can have a molecular weight within the range of from 
about 10,000 to about 750,000 and still be acceptably soluble in the 
solvent. Suitable polyolefins for the process of this invention are 
exemplified by polyethylene, polypropylene, polybutylene, polypiperylene, 
poly(4-methylpentene) and polyoctadiene. Solubility suitability for any 
particular halogenated polyolefin is best determined by observation of its 
solubility in the particular solvent at the selected reaction conditions. 
The halogenated polyolefins of this invention need not necessarily be 
homopolymers. Polyolefin copolymers which are subject to halogenation and 
which are soluble under reaction conditions ma be metalated in accordance 
with the process of this invention. U.S. Pat. No. 3,454,544, which is 
incorporated herein by reference, discloses a number of exemplary 
copolymers suitable for such metalation. 
The solvent utilized to dissolve the halogenated polyolefin should be one 
which is non-reactive towards the transmetalating organometallic compound 
used in the reaction, is a liquid at reaction temperatures and is 
anhydrous. Preferred solvents are ether-containing solvents. The ether 
constituent is preferably tetrahydrofuran, diethylether, 1,2-dimethoxy 
ethane or methoxy benzene. Generally, the weight percent of halogenated 
polyolefin in the ether containing solvent will be below about 10 weight 
percent and preferably within the range of from about 2 to about 5 weight 
percent, all based on the total weight of the solution. 
The transmetalating organometallic compounds used in the process of this 
invention are those which are capable of transferring a metal ion to the 
polymer under the process conditions. Due to their recognized 
transmetalating abilities, alkali metal alkyl compounds are preferred. The 
preferred alkali metal constituent is lithium. The alkyl constituent can 
contain up to about 8 carbon atoms and may have a tertiary, secondary or 
primary bond to the metal. For example, the alkyl constituent can be 
ethyl, n-butyl, sec-butyl, tert-butyl, methyl, phenyl, allyl, n-octyl, 
2-methyl-2-butyl, propyl and the like. The preferred alkyl constituent is 
n-butyl. The compound, n-butyl lithium, has received wide acceptance in 
the transmetalation art as a superior reactant and is a preferred reactant 
for the process of this invention. 
The high reactivity and high affinity for vigorous reaction with moisture 
makes it necessary to provide the transmetalating organometallic compounds 
to the process of this invention as anhydrous solutions. The solvents used 
are any of those which are commonly used by the chemical industry for 
handling such organometallic compounds and which remain a liquid and are 
non-reactive under process conditions. For example, hexane, pentane, 
benzene, toluene and various ethers are suitable. The molar concentration 
of the transmetalating organometallic compound in solution is preferably 
in the range of from about 1.0 to about 3.0. 
The transmetalating reaction of the process of this invention should occur 
at a temperature below 0.degree. C. and preferably within the range of 
from about -5.degree. C. to about -70.degree. C. Ambient pressure is 
suitable. To maintain anhydrous conditions and to prevent unwanted "sport" 
reactions, the reaction should be carried out under a moisture-free inert 
atmosphere such as that provided by dry nitrogen or argon. 
The relative amounts of the halogenated polyolefin and the transmetalating 
organometallic compound used for the reaction are an important aspect of 
the process of this invention. As mentioned previously, the organometallic 
compound is provided in an amount which is less than stochiometric with 
respect to the halogen present in the halogenated polyolefin. In a 
preferred form of this invention, the molar ratio of organometallic to 
halogen is within the range of from about 1/10 to about 3/10. The molar 
ratio chosen will be dependent on the extent of metalation desired. 
In order that the halogenated polyolefin does not see a stochiometric 
excess of the transmetalating organometallic compound, it is necessary 
that the latter be added to the former while the entire reaction mix is 
continuously blended. Blending of the reaction mix will expedite the 
homogeneity thereof and can be carried out by mechanical stirring, 
however, other conventional blending techniques may be used. The rate of 
addition of the transmetalating organometallic compound is any convenient 
rate which is in keeping with the capability of the blending method to 
insure substantial homogeneity of the reaction mix. 
The metalated halogenated polyolefins produced by the process of this 
invention are, as before mentioned, useful in the production of graft 
polymers and functionalized polymers. Such polymers are produced after the 
metalating reaction is substantially complete--such completion occurring 
within ten minutes of the organometallic addition and being indicated by 
the reaction mix obtaining a dark red/purple color. The grafting or 
functionalization procedure used can be any of those known to those 
skilled in the art. See, for example, the before-cited literature by N. A. 
Plate et al and N. A. Plate. For example, graft copolymers of halogenated 
polyolefins and electrophilic polymers can be produced by: adding an 
electrophilic polymer in a solvent, such as tetrahydrofuran, to the 
metalated halogenated polyolefin; precipitating the resultant product by 
the further addition of alcohol; and purifying the precipitate with an 
acetone wash. The reaction temperature is within the range of from about 
-70.degree. C. to about 50.degree. C. Especially useful graft copolymers 
are those in which one copolymer moiety is chlorinated polyethylene and 
the other is polymethylmethacrylate or styrene-acrylonitrile. 
Functionalization can be carried out by the reaction of the metalated 
halogenated polyolefin and carbon dioxide, oxalyl chloride, phosphorus 
oxychloride, sulfuryl chloride, dimethylfulvene, toluene diisocyanate and 
the like. 
The invention is illustrated by the following examples. These examples are 
given merely for purposes of illustration and are not intended in any way 
to restrict the scope of the invention nor the manner in which it can be 
practiced. 
The halogenated polyolefins used in the following examples were CPE 3615 
and CPE 4211 which are chlorinated polyethylene formulations sold by The 
Dow Chemical Company, Midland, Mich. 48640. CPE 3615 has a molecular 
weight of about 750,000 and contains about 36% weight percent chlorine. 
CPE 4211 has a molecular weight of about 100,000 and contains about 42% 
weight percent chlorine.

EXAMPLE I 
CPE 3615 (1.0 g) was dissolved in 50 mL anhydrous tetrahydrofuran at room 
temperature, under nitrogen, in a 100 mL RB flask fitted with thermometer, 
condenser, and nitrogen inlet. The opaque solution was cooled to 
-30.degree. C. by means of a dry ice/acetone bath. To the cooled solution, 
2 mL of a 1.55 M solution of n-butyl lithium in hexane was added dropwise 
from a syringe. The formation of lithiated CPE was evidenced by the 
appearance of pink/purple colored complex. Gel formation occurred due to 
the insolubility of the species. 
EXAMPLE II 
The procedure of Example I was repeated except that the tetrahydrofuran was 
cooled to -60.degree. C. before the CPE 3615 was added. It was observed 
that some portion of the CPE 3615 was not dissolved. After addition of the 
n-butyl lithium solution, a much fainter pink color was observed 
indicating that, due to the low solubility of the CPE 3615, fewer reactive 
sites were available for lithiation. 
EXAMPLE III 
CPE 4211, (1 g), was dissolved in 45 mL anhydrous tetrahydrofuran in a 100 
mL three-neck flask fitted with a mechanical stirrer, N.sub.2 inlet and 
stopper. A dilute solution of butyl lithium (2.7 M in hexane) was added to 
enough hexane to give 5 mL total. In different runs, the butyl lithium 
solution was added, dropwise, in varying amounts and under different 
reaction temperatures as shown in Table 1. Also, before analysis of the 
reaction product, varying amounts of time were allowed after addition of 
the butyl lithium solution as is also indicated in Table 1. The weight 
percent chlorine left unreacted was determined by thermogavimetric 
analyses on a Perkin-Elmer TGS-II system. The red/purple complex of 
metalated polymer forms after a brie induction period. 
TABLE I 
______________________________________ 
Unreacted Cl 
Li/Cl % Time As Wt. % of 
Run Temp. (.degree.C.) 
Molar Ratio (min.) 
CPE 4211 
______________________________________ 
1 -60.degree. 
18 2 37 
2 5 39 
3 10 38 
4 10 38 
5 20 36 
6 60 36 
7 -5.degree. 
18 2 37 
8 5 40 
9 8 36 
10 -60.degree. 
9 2 38 
11 5 38 
12 10 39 
13 20 38 
14 30 39 
15 -60.degree. 
36 2 38 
16 5 34 
17 10 38 
18 30 42 
19 40 38 
______________________________________ 
As can be seen from the results shown in Table 1 only up to about 6 weight 
percent of the chlorine originally present in the CPE 4211 was lithiated, 
cross-linked or involved in dehydrochlorination and thus, the lithiated 
chlorinated polyethylene will maintain, to a high degree, its original 
physical properties for contribution to a graft copolymer or 
functionalized polymer. 
EXAMPLE IV 
To determine the percentage of chlorine sites which are lithiated and, by 
difference, the percentage of chlorine sites involved in side reactions, 
the following procedure was followed. 
2 g of CPE 4211 were dissolved as extensively as possible in 1 hour in 
stirred 80-90 mL anhydrous tetrahydrofuran under nitrogen. This solution 
was immersed in a dry ice/acetone bath until the contents of the flask 
were at -45.degree. C. Butyl lithium (1.8 mL of 2.6 M solution in hexane, 
4.7.times.10.sup.-3 mole) was added to ca. 5 mL hexane, and added dropwise 
to the CPE/tetrahydrofuran mixture. The opaque mixture immediately 
darkened to a red/purple color. After addition was complete (ca. 2 
minutes), the reaction was allowed to continue for 4-5 minutes. Addition 
of a mixture of ethanol, tetrahydrofuran, and water (ca. 1:1:1) caused the 
reaction mixture to turn to pale yellow, signifying the "quenching" of 
reactive metalated sites on the CPE polymer. A few drops of 
phenolphthalein indicator in alcohol solution were added to the reaction 
vessel, and the mixture became purple, indicating the basicity of the 
mixture. A standard solution of HCl in H.sub.2 O (0.379 M) was added 
dropwise by means of a buret, until the purple indicator turned clear. The 
amount of HCl required for neutralization was 2.62 mL (9.9.times.10.sup.-4 
mole). The amount of butyl lithium remaining in the syringe and bottle was 
found by washing them in H.sub.2 O and titrating the resulting basic 
H.sub.2 O as above. Thus, the amount of butyl lithium remaining in the 
syringe and bottle was found to be neutralized by 1.0 mL HCl (0.379 M). 
The amount of butyl lithium actually used in the reaction was therefore 
(4.7-0.38) millimoles, i.e., 4.30 millimoles. The amount of active 
lithiated species is found to be (0.99/4.3).times.100 percent of the added 
butyl lithium, i.e., 23%. The extent of side reactions was therefore 77%. 
EXAMPLE V 
CPE 4211 lithiated in accordance with the procedure of Example III, run 11, 
and at about -60.degree. C., had added thereto lumps of dry ice. 
Mechanical mixing was necessary to insure that the CO.sub.2 contacted the 
lithiated CPE 4211 completely. The resultant product was precipitated by 
the addition of methanol. The precipitate was rigorously purified by 
repeatedly dissolving it in methylene chloride and reprecipitating it with 
methanol. The purified polymer product was prepared into a thin film and 
analyzed with a Perkin-Elmer 283 IR spectrometer. Absorption bands were 
found at about 1630 cm.sup.-1 indicating the presence of --CO.sub.2 Li 
functional groups on the CPE 4211.