High modulus polyketones

Thermoplastic compositions of polyketones having an increased flexural modulus are made by intermixing alternating aliphatic polyketones with a stiffening quantity of pentaerythritol.

BACKGROUND OF THE INVENTION 
Some polymer applications call for a high degree of stiffness (high 
flexural modulus). Examples include some film applications such as 
photographic film base and packaging material. One approach to obtain such 
stiff materials is to add fillers such as carbon or silica, or to 
incorporate fibers, such as glass and carbon fibers into a relatively 
flexible polymer, thereby forming a composite material. Unfortunately, 
composites are difficult to repair and recycle. These and other drawbacks 
can make composites unsuitable in a number of applications. 
Polymers of carbon monoxide and ethylenically unsaturated hydrocarbons 
commonly referred to as aliphatic alternating polyketones (hereafter, 
"polyketones") are now well known. High molecular weight alternating 
aliphatic polyketones are of considerable interest because they exhibit a 
good overall set of physical and chemical properties. This class of 
polymers is disclosed in numerous U.S. patents assigned to Shell Oil 
Company exemplified by U.S. Pat. Nos. 4,880,903 and 4,880,904 which are 
incorporated herein by reference. 
Stiffening polyketones has previously been attained through the formation 
of composites with the addition of materials such as various glasses and 
fibers. U.S. Patent No. 5,122,564 provides an example of this approach of 
the prior art. Stiffening polyketones without necessarily resorting to 
composite formations would help expand the range of applications for 
polyketones. 
SUMMARY OF THE INVENTION 
High modulus polyketone is obtained by the addition of a stiffening 
quantity of pentaerythritol (i.e., tetrakis(hydroxymethyl)methane) to 
polyketone polymer. 
DETAILED DESCRIPTION 
The polyketone polymers which are employed in this invention are of an 
alternating structure and contain substantially one molecule of carbon 
monoxide for each molecule of ethylenically unsaturated hydrocarbon. The 
portions of the polymer attributable to CO alternates with those 
attributable to the ethylenically unsaturated hydrocarbon. 
It is possible to employ a number of different ethylenically unsaturated 
hydrocarbons as monomers within the same polymer but the preferred 
polyketone polymers are copolymers of carbon monoxide and ethylene or 
terpolymers of carbon monoxide, ethylene and a second ethylenically 
unsaturated hydrocarbon of at least 3 carbon atoms, particularly an 
.alpha.-olefin such as propene. Additional monomers can also be used and 
still come within the scope of polyketone polymers described herein. That 
is, polyketone polymers can be made from four, five, or more combinations 
of monomers. Such polyketone polymers are aliphatic in that there is an 
absence of aromatic groups along the polymer backbone. However, 
alternating polyketones may have aromatic groups substituted or added to 
side chains and yet still be considered alternating aliphatic polyketones. 
When the preferred polyketone terpolymers are employed, there will be 
within the terpolymer at least about 2 units incorporating a moiety of 
ethylene for each unit incorporating a moiety of the second or subsequent 
hydrocarbon. Preferably, there will be from about 10 units to about 100 
units incorporating a moiety of the second hydrocarbon. The polymer chain 
of the preferred polyketone polymers is therefore represented by the 
repeating formula 
EQU --[--CO--(--CH.sub.2 --CH.sub.2 --)--].sub.x --[--CO--(--G--)--].sub.y -- 
where G is the moiety of ethylenically unsaturated hydrocarbon of at least 
three carbon atoms polymerized through the ethyllenic unsaturation and the 
ratio of y:x is no more than about 0.5. When copolymers of carbon monoxide 
and ethylene are employed in the compositions of the invention, there will 
be no second hydrocarbon present and the copolymers are represented by the 
above formula wherein y is zero. When y is other than zero, i.e. 
terpolymers are employed, the --CO--(--CH.sub.2 --CH.sub.2 --)--units and 
the --CO--(--G)--units are found randomly throughout the polymer chain, 
and preferred ratios of y:x are from about 0.01 to about 0.1.The precise 
nature of the end groups does not appear to influence the properties of 
the polymer to any considerable extent so that the polymers are fairly 
represented by the formula for the polymer chains as depicted above. 
Of particular interest are the polyketone polymers of number average 
molecular weight from about 1000 to about 200,000, particularly those of 
number average molecular weight from about 20,000 to about 90,000 as 
determined by gel permeation chromatography. The physical properties of 
the polymer will depend in part upon the molecular weight, whether the 
polymer is a copolymer or a terpolymer, and in the case of terpolymers the 
nature of the proportion of the second hydrocarbon present. Typical 
melting points for the polymers are from about 175.degree. C. to about 
300.degree. C., more typically from about 210.degree. C. to about 
270.degree. C. The polymers have a limiting viscosity number (LVN) , 
measured in m-cresol at 60.degree. C. in a standard capillary viscosity 
measuring device, of from about 0.5 dl/g to about 10 dl/g, more frequently 
of from about 0.8 dl/g to about 4 dl/g. The backbone chemistry of 
aliphatic polyketones precludes chain scission by hydrolysis. As a result, 
they generally exhibit long term maintenance of their property set in a 
wide variety of environments. 
The production of polyketone polymers is described in U.S. Pat. Nos. 
4,808,699 and 4,868,282 to van Broekhoven, et al which issued on Feb. 28, 
1989 and Sep. 19, 1989 respectively, and are herein incorporated by 
reference. U.S. Pat. No. 4,808,699 teaches the production of linear 
alternating polymers by contacting ethylenically unsaturated compounds and 
carbon monoxide in the presence of a catalyst comprising a Group VIII 
metal compound, an anion of a nonhydrohalogenic acid with a pKa less than 
6 and a bidentate phosphorous, arsenic or antimony ligand. U.S. Pat. No. 
4,868,282 teaches the production of linear alternating terpolymers by 
contacting carbon monoxide and ethylene in the presence of one or more 
hydrocarbons having an ethylenically unsaturated group with a similar 
catalyst. 
The high modulus polyketone of this invention is made by intermixing a 
stiffening quantity of pentaerythritol with polyketone. The 
pentaerythritol may be incorporated into the polyketone polymer at any 
stage of its processing. Any of the conventional methods suitable for 
forming an intimate mixture of the polymer and additive may be used to 
form the mixture so long as the method results in a substantially uniform 
blend of the composition components. A twin screw compounding extruder 
with injection capability is preferred. For example, a 30 mm Haake or 25mm 
Berstorff counterrotating intermeshing extruder is suitable for this 
purpose. 
A stiffening quantity of pentaerythritol is a quantity which will result in 
a significant increase in the tensile modulus of the polymer relative to 
the same polyketone polymer composition without pentaerythritol. 
Generally, this is an increase of about 10% or more, preferably about 15% 
or more, and most preferably at least 150%. In general, the desired 
increase in modulus of the polyketone composition is obtained by the 
addition of at least about 10% wt (based on total weight of polymer and 
pentaerythritol) . Preferably, at least about 15% wt pentaerythritol is 
added. Most preferably, between about 15% and 40% wt is added. 
The compositions of the invention may also contain other conventional 
polymer additives and which improve or otherwise alter the properties of 
the compositions such as: fillers, extenders, lubricants, pigments, 
stabilizers, impact modifiers, and other polymeric materials. Such 
additives may be added to the composition by blending or by other 
conventional methods. 
The resulting thermoplastic composition can then be extruded, solvent-cast 
into a film, spun into fibers or filaments, or molded into a shaped 
object. Uses for such materials include stiff but breakable packaging such 
as those used to contain some medicine tablets.

The invention will be further illustrated by the following nonlimiting 
examples. 
EXAMPLE 1 (Polyketone Formation) 
A terpolymer of carbon monoxide, ethene, and propene was produced in the 
presence of a catalyst composition formed from palladium acetate, the 
anion of triflouroacetatic acid and 1,3-bis(diphenylphosphino)-propane. 
The melting point of the linear terpolymer was 220.degree. C. and it had a 
limiting viscosity number (LVN) of 1.75 measured at 60.degree. C. in 
m-cresol. 
EXAMPLES 2-5 (Addition of Stiffening Agent) 
The polymer of Example 1 was cryogenically ground in a Mikro Pulverizer. 
The cryoground polymer was then cooled with liquid nitrogen to form a 
coarse powder and tumblemixed with varying quantities of pentaerythritol 
(98% pure grade, obtained commercially from Aldrich Chemical Company) to 
form mixtures. The mixture were then melt mixed using a 30 mm Haake 
co-rotating twin screw extruder operating at 250 rpm at 250.degree. C. 
This melt mixed combination was then injection molded using an Engell ES 
250 molder to produce standard specimens for ASTM D790 tensile and 
flexural testing. Flexural modulus testing results are listed in the 
following table. 
TABLE 1 
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Plasticizer 
Flexural 
Loading Modulus 
Example (Wt %) (MPa) 
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1 0 1786.0 
2 5 1820.7 
3 10 2048.3 
4 20 2786.2 
5 40 3400.0 
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This examples illustrates the improved stiffness attained through the 
addition of pentaerythritol to polyketone.