Processing aid for polymers

Polymer blend composition having improved processibility and comprising: PA0 (a) a major portion of a difficultly melt-processible polymer, and PA0 (b) a minor portion of: PA1 (1) at least an effective amount, to improve processibility, of a fluorocarbon copolymer which at the melt-processing temperature of (a) is either in a melted form if crystalline, or is above its glass transition temperature if amorphous, and PA1 (2) at least an effective amount, to improve processibility, of at least one tetrafluoroethylene homopolymer or copolymer of tetrafluoroethylene and at least one monomer copolymerizable therewith, wherein the mole ratio of fluorine to hydrogen is at least 1:1, and which is solid at the melt-processing temperature of (a); masterbatches comprised of the processing aid; and processes utilizing the processing aid.

FIELD OF THE INVENTION 
The present invention relates to a processing aid for polymers, and to 
polymers having improved processibility, particularly improved extrusion 
characteristics. 
BACKGROUND 
The melt extrusion of high molecular weight polymers, for example, 
hydrocarbon polymers, into shaped structures such as tubing, pipe, wire 
coating or film is accomplished by well-known procedures wherein a 
rotating screw pushes a heated, molten and viscous polymer melt through 
the extruder barrel into a die in which the polymer is shaped to the 
desired form and is then subsequently cooled and resolidified, by various 
means, into the general shape of the die. 
In order to achieve low production costs it is desirable to extrude at high 
rates. Although the extrusion rate is readily increased by increasing the 
rate of revolution of the extruder screw, there is a technical limit to 
these increases because of the viscoelastic properties of the polymer. At 
rates above this limit the polymer may be mechanically heated to 
temperatures at which thermal decomposition can occur, or extrudates with 
a rough surface are obtained. The latter phenomenon can generate an 
undesirable pattern on the surface of the extrudate. One way of avoiding 
this occurrence is to extrude at a higher temperature, but this adds to 
the processing costs and makes cooling of the extrudate more difficult. 
More seriously many polyolefins are already extruded at temperatures near 
their decomposition temperatures, and further increases are not feasible. 
It is desirable, therefore, to find highly efficient means of increasing 
the extrusion rate, without raising the melt temperature, while producing 
products with smooth surfaces. Changes in extruder and die configuration 
can improve melt flow but are not always practical or economically 
feasible Another approach involves the addition of conventional wax-type 
process aids which reduce bulk viscosity and in some cases improve 
processing properties. However, the efficiency is marginal and the high 
levels of additive required often adversely affect other properties. In 
Blatz, U.S. Pat. No. 3,125,547, it is disclosed that the use of 0.01-2.0 
wt. % of a fluorocarbon polymer that is in a fluid state at process 
temperature, such as a fluoroelastomer, will reduce die pressure and 
significantly increase the extrusion rate at which melt fracture occurs 
for high and low density polyethylenes and other polyolefins. It is 
further taught in U.S. Pat. No. 3,125,547 that fluororesins which are 
solids at process temperature afford little or no improvements in 
extrusion characteristics of hydrocarbon polymers. By the term solid, it 
is meant that the fluororesin, if crystalline in nature, is not melted, 
or, if amorphous in nature, is not above the glass transition temperature. 
Kamiya and Inui, in Japanese Patent Application Publication Kokoku No. 
45-30574 (1970, examined) cite the use of crystalline fluorocarbon 
polymers at temperatures below their melting points to eliminate die 
build-up but say nothing of other extrusion improvements. Nishida, Tate 
and Kitani, in Japanese Patent Application Publication Kokai No. 62-64847, 
disclose injection molding compositions comprising an ethylene/alpha 
olefin copolymer having an MFR Of 0.2-200 g/10 min., a density of 
0.850-0.945 g/cm3, and a Q value of 2.5-12, and 0.001-1% by weight of a 
fluorinated hydrocarbon polymer having an F/C ratio of at least 1:2. 
Chu, in U.S. Pat. No. 4,740,341, discloses blends having improved 
extrudability and comprising a linear polymer of ethylene having 
incorporated therein 0.01-0.5 wt. %, based on the composition, of a 
fluorocarbon polymer having an F/C ratio of at least 1:2 and which is 
fluid at 120.degree.-300.degree. C., and 0.01-0.5 wt. %, based on the 
composition, of a polysiloxane. 
Larsen, in U.S. Pat. No. 3,334,157, discloses polyethylene which has been 
modified to improve its optical properties by incorporating therein 0.015 
to greater than 1.7 % by wt., based on the mixture, of finely divided 
polytetrafluoroethylene. 
It is an object of this invention to provide resin compositions with 
substantially improved extrusion characteristics. It is another object to 
provide polymers which can be extruded at high rates to give extrudates of 
high surface quality. It is yet another object to provide polymers that 
can be extruded at low die pressures and at low melt temperatures. Another 
object is to provide a processing aid by means of which all the above can 
be achieved. A further object is to provide masterbatches of the 
processing aid. A still further object is to provide all the above with 
particular emphasis on high molecular weight hydrocarbon polymers which 
are susceptible to melt processing difficulties of the type discussed 
above. Other objects will become apparent hereinafter. 
SUMMARY OF THE INVENTION The present invention provides a processing aid 
composition for difficultly melt-processible polymers. The processing aid 
consists essentially of, with the parts totaling 100%: 
(a) 2-95 parts by weight of a fluorocarbon copolymer which at the 
melt-processing temperature of the difficultly melt-processible polymer is 
either in a melted form if crystalline or is above its glass transition 
temperature if amorphous; and 
(b) 98-5 parts by weight of a tetrafluoroethylene homopolymer or copolymer 
of tetrafluoroethylene and a monomer which is copolymerizable therewith, 
wherein the mole ratio of fluorine to hydrogen is at least 1:1, and which 
is solid at the melt-processing temperature of the difficultly 
melt-processible polymer. 
The processing aid composition consists essentially of a minor portion of 
the processing aid and a major portion of a polymer, either a 
melt-processible or difficultly melt-processible polymer, or both, for 
example, a hydrocarbon polymer. 
The present invention also provides a polymer blend composition having 
improved processibility and which comprises: 
(a) a major portion of a difficultly melt-processible polymer, the host 
polymer, for example, a high molecular weight hydrocarbon homopolymer or 
copolymer of one or more hydrocarbon monomers, and 
(b) a minor portion of: 
(1) at least an effective amount to improve processibility, preferably to 
about 0.5 wt. %, based on the weight of (a), more preferably 0.002-0.08 
wt. %, of a fluorocarbon copolymer wherein, preferably, the mole ratio of 
fluorine to hydrogen is at least 1:1.5, which at the melt-processing 
temperature of (a) is either in a melted form if crystalline, or is above 
its glass transition temperature if amorphous, and 
(2) at least an effective amount to improve processibility, preferably 
0.002-0.08 wt. %, based on the weight of (a), of at least one 
tetrafluoroethylene homopolymer or copolymer of tetrafluoroethylene and at 
least one monomer copolymerizable therewith, wherein the mole ratio of 
fluorine to hydrogen is at least 1:1, and which is solid at the 
melt-processing temperature of (a). 
For example, when the host polymer (a) is a hydrocarbon polymer, its 
melt-processing temperature generally will be in the range 
100.degree.-250.degree. C. 
Finally, the invention provides masterbatches containing the aforesaid 
processing aid; it provides processes for facilitating the processing of 
difficultly melt-processible polymers; and it provides difficultly 
melt-processible polymers containing the processing aid.

DETAILED DESCRIPTION OF THE INVENTION 
In accordance with the present invention it has been discovered, 
surprisingly, that for the improvement of extrusion behavior, difficultly 
melt-processible polymers which contain combinations of fluorocarbon 
polymers (hereinafter called type (1) fluorocarbon polymers) that are 
above their melting points if crystalline, or above their glass transition 
temperatures if amorphous, and are thus molten and fluid at the 
polymer-processing temperatures, and crystalline or amorphous fluorocarbon 
polymers (herinafter called type (2) fluorocarbon polymers) that are solid 
at the polymer melt-processing temperatures, have significant advantage 
over such difficultly melt-processible polymers which contain equivalent, 
or even greater, amounts of extrusion-modifying additives of the art, as 
in U.S. Pat. No. 3,125,547 (supra). The term "extrusion behavior" is 
intended to include such parameters as the die pressure reached during 
extrusion, the operating melt temperatures and the maximum extrusion rates 
that can be achieved while maintaining melt stability and good extrudate 
surface quality. Thus, the compositions of this invention have much 
improved extrusion behavior, that is, reduced die pressure, higher 
allowable extrusion rates, and enhanced surface smoothness of extruded 
articles, and also, in the case of blown films, improved clarity, compared 
to polymers not containing types (1) and (2) fluorocarbon polymers. 
The fluorocarbon polymers of type (1) are those that are fluid at the 
melt-processing temperature of the difficultly melt-processible polymer. 
Thus, at processing temperature they must be above their melting point if 
crystalline, or above their glass transition temperature if amorphous. 
Hence, the melting or softening point of these polymers preferably should 
be in the range 120.degree. to 300.degree. C. or below, more preferably, 
in the range 120.degree. to 200.degree. C. or below. The polymers should 
have sufficiently high molecular weight, with number average molecular 
weights greater than about 10,000, such that they do not exude from the 
difficultly melt-processible polymer extrudate at melt-processing 
temperatures. With respect to their chemical composition, it is preferred, 
but not essential, to employ fluorocarbon polymers having a fluorine to 
hydrogen ratio of at least 1:1.5. Fluorinated monomers which give rise to 
suitable polymers include vinylidene fluoride, hexafluoropropylene, 
chlorotrifluoroethylene, tetrafluoroethylene and perfluoroalkyl 
perfluorovinyl ethers. Specific examples of the fluorocarbon polymers of 
type (1) that may be employed in this invention include copolymers of 
vinylidene fluoride and a monomer selected from hexafluoropropylene, 
chlorotrifluoroethylene, 1 -hydropentafluoropropylene and 
2-hydropentafluoropropylene; copolymers of vinylidene fluoride, 
tetrafluoroethylene and hexafluoropropylene or 1- or 
2-hydropentafluoropropylene; copolymers of tetrafluoroethylene and 
propylene and, optionally, vinylidene fluoride, all of which are known in 
the art. In some cases these copolymers may also include a 
bromo-containing monomer as taught in Apotheker and Krusic, U.S. Pat. No. 
4,035,565, or terminal iodo-groups, as taught in U.S. Pat. No. 4,243,770. 
The latter patent also discloses the use of iodo group-containing 
fluoroolefin comonomers. When certain molar ratios of monomers are used in 
these copolymers, then the glass transition temperature is near or below 
0.degree. C., and these polymers are useful elastomers that are readily 
available articles of commerce. 
The fluorocarbon polymers of type (2) that are solid at the melt processing 
temperature of the difficultly melt-processible polymer include 
homopolymers of tetrafluoroethylene and copolymers of tetrafluoroethylene 
with certain copolymerizable monomers. The selection of the fluorocarbon 
polymer of type (2) is not limited to high molecular weight polymers, 
whether the polymer is melt-processible or not melt-processible, whether 
the polymer is made by dispersion polymerization or suspension 
polymerization, or how much comonomer is present, except as stated above. 
For example, if excessive amounts of comonomer are used, the polymer will 
not be a solid at the temperature used for melt processing the difficultly 
melt-processible polymer; or, if a copolymer has too low a molecular 
weight, the copolymer may not be a solid at the temperature used for melt 
processing the difficultly melt-processible polymer. Suitable 
tetrafluoroethylene homopolymers include those that are high molecular 
weight and fibrillate, or do not fibrillate to a substantial extent, under 
shearing conditions, as well as those which are low molecular weight and 
non-fibrillating, such as those which have been subjected to ionizing 
radiation. Suitable monomers copolymerizable with tetrafluoroethylene to 
give melt-processible copolymers are ethylene, perfluoroolefins such as 
hexafluoropropylene, and perfluoro(alkyl vinyl ethers) such as 
perfluoro(propyl vinyl ether) and perfluoro(alkyl ethers) which contain 
functional groups such as --SO.sub.2 F or --COOCH.sub.3. More than one 
comonomer may be used, provided all the aforesaid requirements are met. 
The effect of the combined addition of fluorocarbon polymers types (1) and 
(2) in eliminating roughness of the extrudate, allowing increases in 
extrusion speed and reducing die pressures is significantly greater than 
when either type (1) or type (2) is used alone at concentrations equal to 
the sum of the concentrations of (1) and (2). It has been found that even 
when (1) and (2) are added at total concentrations as low as 0.0025 wt. %, 
all extrudate roughness is eliminated at extrusion shear rates well beyond 
1000 sec.sup.-1 (Example 2). Quantities in excess of 1 wt. % are not 
necessary. In general, if the fluorocarbon polymers are not compatible 
with the difficultly melt-processible polymer, that is to say, are not 
soluble in such polymer, the addition of higher levels serves no useful 
purpose, and when the incompatible fraction becomes too large, it may 
adversely affect the optical properties of the extrudate. Such is the 
case, for example, when the difficultly melt-processible polymer is a 
hydrocarbon polymer. The beneficial effects of even very low ratios of 
types (1) to (2) or types (2) to (1) are readily evident but, in general, 
there will be an optimum ratio of types (1) to (2) which may be determined 
experimentally for any particular combination of types (1) and (2). The 
weight ratio of fluorocarbon polymer type (1) to fluorocarbon polymer type 
(2) may vary from 2/98 to 95/5, preferably from 10/90 to 90/10. 
When the difficultly melt-processible polymer is a hydrocarbon polymer, for 
example, a hydrocarbon polymer having a melt index (ASTM D-1238) at 
190.degree. C. of 5.0 or less, preferably 2.0 or less, the hydrocarbon 
polymer component of the composition of this invention may comprise an 
elastomeric copolymer of ethylene and propylene and, optionally, a 
non-conjugated diene monomer, for example, 1,4-hexadiene, or, in general, 
any thermoplastic hydrocarbon polymer obtained by the homopolymerization 
or copolymerization of a monoolefin(s) of the formula CH.sub.2 .dbd.CHR, 
where R is H or an alkyl radical, usually of not more than eight carbon 
atoms. In particular, this invention is applicable to polyethylene, both 
of the high density type and the low density type, for example, densities 
within the range 0.89 to 0.97; polypropylene; polybutene-1; 
poly(3-methylbutene); poly(methylpentene); and linear low density 
copolymers of ethylene and an alpha-olefin such as propylene, butene-1, 
octene-1, decene-1, octadecene, etc. Similarly, the invention is also 
applicable to blends of difficultly melt-processible polymers, and 
difficultly melt-processible polymers containing additives, such as 
antioxidants, light stabilizers, antiblocking agents, pigments, etc. 
Because of the different melt characteristics of the different hydrocarbon 
polymers mentioned, the addition of the types (1) and (2) fluorocarbon 
polymers may be of greater value in some hydrocarbon polymers than in 
others. Thus, hydrocarbon polymers such as polypropylene and branched 
polyethylene, that are not of high molecular weight have good melt flow 
characteristics even at low temperatures, so that surface roughness and 
other surface defects can be avoided by adjustment of extrusion 
conditions. Such hydrocarbon polymers may not require the use of the 
fluorocarbon polymer additives of this invention, or be noticeably 
improved by them, except under unusual, adverse extrusion conditions. Such 
hydrocarbon polymers, therefore, are considered herein as not difficultly 
melt-processible polymers. However, other polymers such a high molecular 
weight, high density polyethylene or linear low density polyethylene 
copolymers, particularly those with narrow molecular weight distributions, 
do not have this degree of freedom in the variation of extrusion 
conditions and it is particularly with these resins that remarkable 
improvements in the surface quality of the extruded product are obtained 
with compositions containing the described type (1) and type (2) 
fluorocarbon polymers. 
It will also be recognized by one skilled in the art that it may not be 
possible to achieve, simultaneously, reduced die pressure, increased 
throughput and improved surface quality to the maximum extent at given 
concentration of types (1) and (2). Thus, one might elect to attain 
maximum improvement in one parameter, in particular, at the expense of 
corresponding improvements in other parameters. For example, increased 
output of extrudate with high quality surface characteristics may not 
necessarily be accompanied by reduced die pressure. The best set of 
conditions will be determined by the specific requirements of the 
extrusion. 
The addition of the fluorocarbon polymer modifiers to the difficultly 
melt-processible polymer can be accomplished by any of the means 
heretofore developed for the addition of modifiers to such polymers. For 
example, the fluorocarbon polymers (1) and (2) may be added independently 
to, for example, a hydrocarbon polymer on a rubber compounding mill or in 
a Banbury or other internal mixer or in a mixing extruder, in all of which 
the fluorocarbon polymers are uniformly distributed throughout the host 
polymer. It is also feasible to dry-blend the two fluoropolymers with the 
host polymer in the solid state, and then effect uniform distribution of 
the fluoropolymers in the melt extruder employed in the fabrication by 
using an extruder screw with good mixing capability. 
Alternatively, masterbatch dispersions (mixtures) of types (1) and (2) in a 
diluent polymer, either together or separately, can be metered to the feed 
section of the extruder by appropriate devices. The diluent polymer can be 
a difficultly melt-processible polymer, or it can be a melt-processible 
polymer that does not substantially deleteriously affect the interaction 
of the aforesaid components (a), (b)(1) and (b)(2) in achieving the 
beneficial effects of the invention. For example, the diluent polymer can 
be a melt-processible hydrocarbon polymer, such as a homopolymer or 
copolymer of a monoolefin(s) of the formula RCH.dbd.CH.sub.2 wherein R is 
H or an alkyl radical, usually of not more than eight carbon atoms. In 
most cases such a hydrocarbon polymer will have a melt index (ASTM D-1238) 
at 190.degree. C. of 20.0 or less, preferably 5.0 or less. In preparing 
such masterbatches the amounts of fluorocarbon o polymers types (1) and 
(2) will usually be such that they provide 1-25 wt. %, preferably 1-10 wt. 
%, of the masterbatch. Further to the above regarding the need to avoid 
adversely affecting the beneficial effects of the invention, in preparing 
the masterbatch, the concentrations of types (1) and (2), as well as the 
diluent polymer, will be selected so as to achieve good mixing of all the 
ingredients. Particularly, fibrillation of the fluorocarbon polymer type 
(2) is to be avoided. In any of the above procedures, it is also possible 
to employ previously prepared mixtures of fluorocarbon polymer type (1) 
with fluorocarbon polymer type (2). 
In the practice of this invention, it will be found that the beneficial 
effects are not necessarily observed immediately on the onset of 
extrusion, and depending on the overall concentrations of modifier, it may 
take from 10 minutes to 8 hours to reach stable extrusion rate and die 
pressure. Longer times are required at low concentrations of types (1) and 
(2). When it is desirable to operate at very low levels of modifiers and 
hasten the achievement of equilibrium, it may be expedient to first 
"condition" the extruder rapidly using a composition containing 0.1 to 
1wt. % of the fluorocarbon polymers types (1) and (2), and then to switch 
to the desired concentrations of types (1) and (2). 
Just as it has been observed that the beneficial effects may not be 
observed immediately, it has also been observed that the beneficial 
effects may continue to be observed after addition of the fluorocarbon 
polymers of types (1) and (2) is discontinued. Consistent with this 
observation, after stable extrusion rate and die pressure are achieved, 
the beneficial effects of the invention may be realized by alternating a 
feed of difficultly melt-processible polymer and one containing the 
processing aid of the invention. 
The evaluations reported below employ a C. W. Brabender Computerized 
Plasti-Corder equipped with a 19.1 mm (3/4 in.) diameter extruder with a 
25/1 length/diameter ratio. The screw has ten feed flights, 10 
compression flights with a compression ratio of 3:1, and 5 metering 
flights. Operating parameters are controlled by five independent heating 
zones (No. 5 closest to the die), four pressure transducers and a 
torque-measuring drive unit with 1-120 rpm capability. The instrument is 
equipped with software for rheometric capillary extrusion testing. The 
capillary die, made from #416 nitrided stainless steel, has a diameter of 
2 mm and a length of 40 mm, unless otherwise noted. In operation, the 
required machine conditions are set and the polymer is then extruded, 
usually at 40 rpm, until equilibrium (constant throughput and constant die 
pressure) is reached. For a linear low density polyethylene with a melt 
index at 190.degree. C. of 1, extrusion at 40 rpm at 204.degree. C. gives 
a throughput of about 19-20 g/min. and a die pressure of 28 MPa 
(Comparative Example 1). For experiments that are run in sequence, by 
changing the feed composition, the initial output parameters correspond to 
the previous equilibrium, and then gradually change to a new equilibrium. 
When equilibrium is achieved a range of screw speeds is then run to 
produce new equilibrium values of throughput and die pressure. The 
relation between throughput and die pressure is determined from a plot of 
the data, and die pressure data at certain fixed production rates can be 
estimated for comparison of data between experiments. Surface quality of 
the extrudate is judged by visual examination. 
After each run the extruder is thoroughly cleaned. The equipment is first 
purged with a highly filled abrasive composition, for example, the 
commercially available UCC-DFD-0964. The capillary die is removed and 
heated with a propane torch until it is free of polymer and has reached a 
red glow. The extruder is disassembled and each section--screw, barrel, 
die assembly, and transducers--is cleaned, first with a wire brush, and 
then with methyl ethyl ketone solvent. After reassembly and calibration of 
the transducers, the unmodified hydrocarbon polymer is run first to 
establish equilibrium conditions, and to assure that reliable output is 
being obtained. For this purpose, the equilibrium value at 40 rpm, only, 
was sometimes used. If previously established equilibrium values for 
unmodified polymer are not achieved, the cleanout procedure is repeated. 
In Table 1 the various materials used in the examples which follow are 
identified. 
EXAMPLES 
Comparative Example 1 
Hydrocarbon Polymer A was introduced to the extruder with the screw 
operating at 40 rpm and heating zones Nos. 1, 2, 3, 4 and 5 controlling at 
nominal temperature settings of 150.degree., 180.degree., 200.degree., 
204.degree., and 204.degree. C., respectively (No. 5 is closest to the 
die). Equilibrium extrusion conditions, when throughput and die pressure 
were constant, were reached after a period of 15 min. The screw rpm was 
then systematically varied from 12 rpm to 60 rpm. After determining the 
extrusion rate at various screw speeds, the data were input to a computer 
program which generated a curve of die pressure vs. throughput (shown in 
Curve 1 of the Figure which is a part of this specification). Selected 
values taken from Curve 1are shown in Table 2. The extrudates of 
Hydrocarbon Polymer A had surface roughness at all extrusion rates above 
about 4 g/min. 
Comparative Example 2 
Hydrocarbon Polymer A which, as a dry blend, had intimately dispersed 
therein 0.1% of Fluorocarbon Polymer 2A, was added to the extruder just at 
the end of Comparative Example 1, at the same nominal temperature settings 
and at a screw speed of 40 rpm. Steady state was achieved after 10 min. 
and did not change after a further 240 min. The die pressure/throughput 
relationship was then obtained as in Comparative Example 1 and is shown in 
Curve 2 of the Figure. Data are shown in Table 2. There was no significant 
effect of Fluorocarbon Polymer 2A, alone, on the flow characteristics of 
Hydrocarbon Polymer A, and surface roughness appeared at all extrusion 
rates above about 4 g/min. 
Comparative Example 3 
An extruder warm-up was carried out as in Comparative Example 1 with 
unmodified Hydrocarbon Polymer A, giving the same results. Hydrocarbon 
Polymer A which, as a dry blend, had intimately dispersed therein 0.02 wt. 
% of Fluorocarbon Polymer 1A, was then added to the extruder at the same 
temperature settings and at a screw speed of 40 rpm. Steady state was 
achieved after 60 min. and did not change after a further 60 min. The die 
pressure/throughput relationship was then obtained as in Comparative 
Example 1 and is shown as Curve 3 in the Figure. Representative data are 
shown in Table 2. In this case there was an approximate 10% reduction in 
die pressure at a given throughput, compared to Comparative Example 1, and 
extrudates were smooth and glossy at extrusion rates below about 30 g/min. 
Example 1 
An extruder warm-up was carried out as in Comparative Example 1, giving the 
same results. Hydrocarbon Polymer A which, as a dry blend, had intimately 
dispersed therein 0.01 wt. % of Fluorocarbon Polymer lA and 0.01 wt. % of 
Fluorocarbon Polymer 2A was then added at the same temperature settings 
and a screw speed of 40 rpm. A new equilibrium was established, after 180 
min., at much lower pressures than for the hydrocarbon resin alone or for 
the composition of Comparative Example 3. The die pressure/throughput 
curve was then obtained as in Comparative Example 1, and is shown as Curve 
4 in the Figure. Representative data are shown in Table 2. There was an 
approximately 30% drop in die pressure over the entire range, compared to 
Hydrocarbon Polymer A, even though the combined concentrations of 
Fluorocarbon Polymers 1A and 2A in this example is no greater than the 
concentration of Fluorocarbon Polymer lA in Comparative Example 3. 
Extrudate surfaces were smooth and glossy throughout the range of 
extrusion rates attainable under the conditions of the example (up to 55 
g/min., which is equivalent to a shear rate of about 1500 sec.sup.-1). 
When a 1.5 mm diameter die was used in order to obtain shear rates up to 
about 3000 sec.sup.-1, the extrudate was smooth and glossy over the entire 
range of extrusion rates. 
Example 2 
An extruder warm-up was carried out as in Example 1, with similar results. 
A dry blend of Hydrocarbon Polymer A having intimately dispersed therein 
0.0005 wt. % of Fluorocarbon Polymer 1A and 0.0020 wt. % of Fluorocarbon 
Polymer 2A was then added at the same temperature settings and a screw 
speed of 40 rpm. The new equilibrium was established after 180 minutes, 
at a lower die pressure than for the hydrocarbon resin alone or for the 
composition of Comparative Example 3. The die pressure/extrusion rate 
curve was obtained as in Example 1 and representative data are shown in 
Table 2. There was an approximately 28% reduction in die pressure over the 
entire extrusion rate range compared to Hydrocarbon Polymer A, even though 
the combined concentrations of Fluorocarbon Polymers 1A and 2A is only 
12.5% of the concentration of Fluorocarbon Polymer 1A in Comparative 
Example 3. Extrudate surfaces were smooth and glossy at extrusion rates 
below 55 g/min. 
Example 3 
In this example a series of compositions was evaluated to demonstrate the 
effect of the relative weight ratios of Fluorocarbon Polymer 1A to 
Fluorocarbon Polymer 2A, as shown in Table 3. Each composition was a dry 
blend of Fluorocarbon Polymers 1A and 2A in Hydrocarbon Polymer A, and 
after extruder warm-up as described in Example 1, each was added at the 
same temperature settings and a screw speed of 40 rpm. New equilibria were 
then established after 180 minutes, at lower die pressures than for the 
hydrocarbon resin alone or for the composition of Comparative Example 3. 
Die pressure/extrusion rate data were obtained as in Example 1 and are 
shown in Table 3. There is a significant reduction in die pressure over 
the entire range compared to Hydrocarbon Polymer A, even though the 
combined concentrations of Fluorocarbon Polymers 1A and 2A is no greater 
than the concentration in Comparative Example 3. Extrudate surfaces were 
smooth and glossy at extrusion rates up to 55 g/min. 
Example 4 
A composition of Hydrocarbon Polymer A containing an intimate dry powder 
mix of Fluorocarbon Polymers 1B and 2A, 0.01 wt. % of each, based on 
difficultly melt-processible polymer, was extruded and evaluated as in 
Example 1. A control experiment in which the difficultly melt-processible 
polymer contained 0.04 wt. % of Fluorocarbon Polymer 1B, alone, was also 
carried out. Data in Table 4 show that the composition of this invention 
extrudes at very much lower die pressures than the control and the 
extrudate is free of surface imperfections at much higher extrusion rates, 
even though it contains only half as much total modifier. 
Example 5 
A composition of Hydrocarbon Polymer A containing an intimate dry powder 
mix of Fluorocarbon Polymers 1C and 2A, 0.01 wt. % of each, based on 
hydrocarbon polymer, was extruded and evaluated as in Example 1. A control 
experiment in which the hydrocarbon polymer contained 0.04 part by wt. of 
Fluorocarbon Polymer 1C, alone, was also carried out. Data in Table 4 show 
that the composition of this example extrudes at very much lower die 
pressures than the control and the extrudate is free of surface 
imperfections at much higher extrusion rates, even though it contains only 
half as much total modifier. 
Examples 6-10 
For each example, Hydrocarbon Polymer A, which as a dry blend had 
intimately dispersed therein 0.01 wt. % of Fluorocarbon Polymer 1A and 
0.01 wt. % of Fluorocarbon Polymers 2B, 2C., 2D, 2E, or 2F (Examples 6-10, 
respectively), was added to the extruder and treated in the manner 
described in Example 1. As shown by the data in Table 5, the new 
equilibria were then established after 180 minutes, at lower pressures 
than for the controls represented by Comparative Examples 1 and 3, Table 
2. All extrudate surfaces were smooth and glossy throughout the range of 
extrusion rates up to 38 g/min. Compositions of Hydrocarbon Polymer A and 
0.10 wt. % of any of the Fluorocarbon Polymers 2B, 2C., 2D, 2E and 2F, or 
2F alone, showed no improvement in extrusion behavior (data not shown). 
Examples 11 and 12 
In these examples Hydrocarbon Polymers B and C were compared in 
formulations containing dry blends of Fluorocarbon Polymers 1A and 2A in 
the amounts shown in Table 6. Die pressure/extrusion rate data were 
evaluated as outlined in Example 1. For each example there is a control 
sample containing no additives and another showing the effect of 
Fluorocarbon Polymer 1A alone. Data were analyzed as in Example 1 and are 
shown in Table 6. 
Example 13 
In this experiment a chrome-plated, 2.54 cm (1 in.) wide slit die having a 
gap of 0.76 mm (0.03 in.) and a land length of 1.27 cm (0.5 in.) was used. 
A dry blend composition of Hydrocarbon Polymer A and 0.01 wt. % of each of 
Fluorocarbon Polymers 1A and 2A was fed at 60 rpm, giving the initial 
throughput and die pressure ratings indicated in Table 7. The initial 
extrudate had a rough dull surface. After 3 h the extrudate was smooth and 
glossy and there was a 17.5% reduction in die pressure as well as a 3.5% 
increase in throughput. The extrudate surface remained excellent up to the 
maximum throughput achievable with the extruder (55 g/min. at 120 rpm). In 
a similarly-run control experiment with Hydrocarbon Polymer A alone, the 
starting and final parameters were as shown in Table 7, and the extrudate 
had a dull rough surface at all extrusion rates above about 8 g/min. In 
another control experiment with 0.02 wt.% of Fluorocarbon Polymer 1A, 
there was only a 3% pressure drop after 3 h and nil increase in 
throughput. The extrudate surface was smooth and glossy at 60 rpm, but 
dull and rough in appearance at all higher screw speeds. 
TABLE 1 
______________________________________ 
All are amorphous at room temperature and above. 
______________________________________ 
Type (1) Fluorocarbon Polymers: 
1A: A commercially available fluoroelastomer 
containing polymer repeat units of 60 wt. % 
vinylidene fluoride and 40 wt. % 
hexafluoropropylene and having a Mooney 
viscosity of 60 at 121.degree. C. It was in the 
form of a fine powder which had been 
obtained by cryogenic grinding and had a 
light dusting of calcium carbonate as an 
antiblocking agent. 
1B: A commercially available fluoroelastomer 
containing polymer repeat units of 45 wt. % 
vinylidene fluoride, 30 wt. % 
hexafluoropropylene and 25 wt. % 
tetrafluoroethylene and having a Mooney 
viscosity of 80 at 121.degree. C. It was ground and 
dusted as in 1A. 
1C: A commercially available copolymer composed 
of polymer repeat units of 
tetrafluoroethylene, propylene and 
vinylidene fluoride. 
Type (2) Fluorocarbon Polymers: 
2A: A commercially available PTFE resin which 
has been irradiated, melts at 280.degree. C., and has 
an average particle size of about 1 mm. 
2B: A commercially available, high molecular 
weight, non-melt-processible PTFE, prepared 
by suspension polymerization, having a 
standard specific gravity of 2.16 and an 
average particle size of 35 micrometers. 
2C: A commercially available powdered copolymer 
of tetrafluoroethylene and 12 wt. % of 
hexafluoropropylene and having a melt 
viscosity of 9,500 Ns/m.sup.2 at 372.degree. C. 
2D: A commercially available powdered copolymer 
of tetrafluoroethylene and 3-4 wt. % of 
perfluoro(propyl vinyl ether) and having a 
melt viscosity of 4,700 Ns/m.sup.2 at 372.degree. C. 
2E: A commercially available powdered copolymer 
of tetrafluoroethylene and 3-4 wt. % of 
perfluoro(propyl vinyl ether) and having a 
melt viscosity of 34,000 Ns/m.sup.2 at 372.degree. C. 
2F: A commercially available powdered, 
essentially alternating copolymer of 
tetrafluoroethylene, ethylene and a small 
amount of a proprietary comonomer, and 
having a melt flow of 20 at 297.degree. C. 
(ASTM-D3159). 
Hydrocarbon Polymers 
A: A high molecular weight, linear low density 
(d = 0.918) copolymer of ethylene and butene-1 
having a melt index (ASTM D-1238, cond. E) 
of 1.0. 
B: A high density polyethylene (d = 0.945) having 
a melt index of 0.05. 
C: A low density (d = 0.925) polyethylene 
containing 5 wt. % of high density 
polyethylene and a small quantity of 
poly(vinyl acetate), and having a melt index 
of 0.50. 
______________________________________ 
TABLE 2 
__________________________________________________________________________ 
Comparative Examples 
Example 
Example 
EXAMPLES 1 2 3 1 2 
__________________________________________________________________________ 
COMPOSITION (% by wt.) 
Hydrocarbon Polymer A 
100 99.9 99.95 99.98 
99.975 
Fluorocarbon Polymer 2A 
-- 0.1 -- 0.01 0.002 
Fluorocarbon Polymer 1A 
-- -- 0.02 0.01 0.0005 
Throughput (g/min.) 
Die Pressure (MPa) 
2.1 9.9 
5.0 16.4 11.7 
7.9 20.4 20.2 18.6 14.3 
10.0 22.1 22.1 19.6 15.6 14.9 
15.0 26.3 26.3 24.1 18.9 18.0 
20.0 29.1 29.1 27.0 21.1 20.2 
25.0 31.3 31.3 29.5 23.4 22.4 
30.0 33.5 33.4 31.7 25.4 24.5 
35.0 34.3 33.7 26.9 
40.0 35.4 28.3 
45.0 35.8 29.4 
50.0 30.4 
55.0 30.9 
Surface R, D above 
R,D above 
S,G at 
S,G to 
S, G to 
4 g/min. 
4 g/min. 
29 g/min. 
55 g/min. 
55 g/min. 
and below 
__________________________________________________________________________ 
S -- smooth 
G -- glossy 
R -- rough 
D -- dull 
TABLE 3 
__________________________________________________________________________ 
EXAMPLE 3 
A B C D E F 
__________________________________________________________________________ 
COMPOSITION (% by wt.) 
Hydrocarbon Polymer A 
99.980 
99.980 
99.980 
99.980 
99.980 
99.980 
Fluorocarbon Polymer 2A 
0.0196 
0.019 
0.018 
0.016 
0.002 
0.001 
Fluorocarbon Polymer 1A 
0.0004 
0.001 
0.002 
0.004 
0.018 
0.019 
Wt. ratio 1A/2A 
2/98 5/95 
10/90 
20/80 
90/10 
95/5 
Throughput (g/min.) 
Die Pressure (MPa) 
10 15.1 7.7 8.4 11.5 
18.3 
17.3 
15 18.5 9.9 10.7 
14.2 
21.8 
21.1 
20 21.0 11.8 
13.1 
16.3 
24.6 
24.1 
25 23.3 13.9 
15.8 
18.2 
26.9 
26.8 
30 25.4 16.0 
18.6 
20.2 
28.8 
29.2 
Surface all extrudates were smooth and glossy up to 55 
__________________________________________________________________________ 
g/min. 
TABLE 4 
__________________________________________________________________________ 
Control 
Example 4 
Control 
Example 5 
__________________________________________________________________________ 
COMPOSITION (% by wt.) 
Hydrocarbon Polymer A 
99.96 99.98 99.96 99.98 
Fluorocarbon Polymer 2A 
-- 0.01 -- 0.01 
Fluorocarbon Polymer 1B 
0.04 0.01 -- -- 
Fluorocarbon Polymer 1C 
-- -- 0.04 0.01 
Throughput (g/min.) 
Die Pressure (MPa) 
10 17.4 8.7 22.3 19.7 
15 21.5 10.9 26.8 23.6 
20 24.5 12.7 29.6 26.0 
25 27.1 14.8 31.7 28.3 
30 29.4 17.0 33.3 30.4 
Surface S, G below 
S, G below 
S, G below 
S, G to 
38 g/min. 
55 g/min. 
28 g/min. 
55 g/min. 
__________________________________________________________________________ 
S -- smooth 
G -- glossy 
R -- rough 
D -- dull 
TABLE 5 
______________________________________ 
Examples 6 7 8 9 10 
______________________________________ 
COMPOSITION (% by wt.) 
Hydrocarbon Polymer A 
99.98 99.98 99.98 
99.98 99.98 
Fluorocarbon Polymer 1A 
0.01 0.01 0.01 0.01 0.01 
Fluorocarbon Polymer 2B 
0.01 -- -- -- -- 
Fluorocarbon Polymer 2C 
-- 0.01 -- -- -- 
Fluorocarbon Polymer 2D 
-- -- 0.01 -- -- 
Fluorocarbon Polymer 2E 
-- -- -- 0.01 -- 
Fluorocarbon Polymer 2F 
-- -- -- -- 0.01 
Throughput (g/min.) 
Die Pressure (MPa) 
10 19.3 20.0 19.8 19.3 18.4 
15 23.2 22.7 23.8 23.7 22.6 
20 25.9 25.2 27.0 26.7 25.6 
25 28.4 27.6 29.6 29.4 23.3 
30 30.6 29.7 -- 31.7 30.7 
Surface all surfaces smooth and glossy 
below 38 g/min. 
______________________________________ 
TABLE 6 
__________________________________________________________________________ 
Control 
Control 
Example 11 
Control 
Control 
Example 12 
__________________________________________________________________________ 
COMPOSITION (% by wt.) 
Hydrocarbon Polymer B 
100 99.96 
99.98 -- -- -- 
Hydrocarbon Polymer C 
-- -- -- 100 99.92 
99.96 
Fluorocarbon Polymer 1A 
-- 0.04 0.01 -- 0.08 0.02 
Fluorocarbon Polymer 2A 
-- -- 0.01 -- -- 0.02 
Throughput (g/min.) 
Die Pressure (MPa) 
10 25.4 19.0 -- -- -- -- 
15 unstable 
19.6 17.9 12.4 11.9 11.5 
20 unstable 
21.5 19.3 13.6 13.1 12.9 
25 unstable 
-- -- 14.7 14.2 14.0 
30 unstable 
-- -- 15.7 15.0 14.9 
Surface R, D above 
S, G to 
S, G to 
S, G to 
S, G to 
S, G to* 
10 g/min. 
23 g/min. 
23 g/min. 
38 g/min. 
38 g/min. 
38 g/min. 
__________________________________________________________________________ 
S -- smooth 
G -- glossy 
R -- rough 
D -- dull 
*These extrudates did not have the occasional cloudy streaks that appeare 
in the controls. 
TABLE 7 
______________________________________ 
Control 
Control Example 13 
______________________________________ 
COMPOSITION (% by wt.) 
Fluorocarbon Polymer 1A 
-- 0.02 0.02 
Fluorocarbon Polymer 2A 
-- -- 0.02 
Starting pressure, MPa 
25.4 25.6 25.1 
Starting throughput, g/min. 
25.7 24.7 24.7 
Ending pressure, MPa 
25.4 24.8 19.7 
Ending throughput, g/min. 
25.7 24.9 25.8 
Surface rough smooth smooth 
glossy glossy 
______________________________________