One-extrusion method of making a shaped crosslinkable extruded polymeric product

Method of and apparatus for making a shaped crosslinked extruded polymeric product by extruding compacted, melted polymer, e.g., polyethylene, into a mixer formed on or fitted to the discharge end of an extruder, injecting proportionate amounts of a mixture of compounding ingredients including olefinically unsaturated hydrolyzable silane, free-radical generator and, preferably, a silanol condensation catalyst into the compacted, melted polymer. The polymer and compounding ingredients are blended in the mixer until the silane is grafted to said polymer, and the resulting grafted polymer mixed with the silanol condensation catalyst is extruded thruugh a die to form the product of the required final shape. The resulting product is subjected to the action of H.sub.2 O until the grafted polymer is crosslinked.

BACKGROUND OF THE INVENTION 
1. Field Of The Invention 
The present invention relates to methods and apparatus for producing 
shaped, crosslinked, extruded polymeric products and more specifically 
relates to the production of shaped, crosslinked, extruded polyethylene 
products. 
2. Prior Art 
The preparation of graft copolymers of polyolefins such as polyethylene and 
hydrolyzable olefinically unsaturated silanes in the presence of a 
solvent, e.g., xylene, and using a peroxide or hydroperoxide catalyst is 
disclosed in U.S. Pat. No. 3,075,948. 
The production of shaped crosslinked polyethylene is disclosed in U.S. Pat. 
No. 3,646,155 in which polyethylene and a hydrolyzable, olefinically 
unsaturated silane are first reacted in an extruder in the presence of a 
peroxide catalyst to form a graft copolymer which is extruded and 
granulated and mixed by tumbling with a blend of polyethylene and a 
silanol condensation catalyst made in a second extrusion. The resulting 
composition is extruded in a third extrusion to provide a crosslinkable 
composition. While it is possible to carry out the process of this patent 
with only two extrusions, it still involves a large amount of handling and 
an excessive usage of extruder time, higher operating costs and the risk 
of deterioration of the graft copolymer during storage. Other patents 
disclosing the need for similar multi-extrusions, i.e., two or more 
extrusions, in order to provide a crosslinkable product include: U.S. Pat. 
Nos. 3,802,913; 4,117,063; 4,136,132; and 4,228,255. 
It is difficult, if not impossible, or impractical, to adequately mix the 
silane, peroxide and silanol condensation catalyst into polyethylene by 
injecting them into a conventional extruder and there results the 
formation of small gels throughout the polyethylene mass, apparently 
because of localized premature crosslinking in areas of high additive 
concentration resulting from inadequate mixing. A one-extrusion process 
for making a crosslinkable polyethylene is disclosed in U.S. Pat. Nos. 
4,117,195 and 4,351,790, herein called the "one-step" patents. In the 
processes of these patents, polyethylene, hydrolyzable unsaturated silane, 
free-radical generator and a silanol condensation catalyst are fed into 
the hopper of barrel of a specially designed, complex and expensive 
extruder. Extruders usable in the one-step process are substantially 
longer at 30:1 length to diameter ratio which is substantially longer than 
the 20:1 or 24:1 length to diameter of the majority of conventional 
extruders now in use. Additionally, a special extruder screw design as 
disclosed in British Pat. No. 964,428 is needed in the one-step process. 
In this special screw design, the material to be extruded is forced over 
the flight of the screw from a rapidly-converging blind passage into a 
very slowly converging passage, followed by a slightly converging zone and 
thence through a metering zone of uniform cross-section. 
Furthermore, suitable control of temperature in the extruder of the 
one-step process is necessary to prevent the high temperature in the 
metering zone (where grafting is caused to occur at relatively high 
temperatures of about 230.degree. C. more or less) from creeping into the 
other zones to produce higher temperatures in the other zones which 
normally operate at about 130.degree. C. The temperature (230.degree. C.) 
used in the metering (grafting) zone of the one-step process is 
considerably higher than the temperature used in the grafting process of 
the earlier patentees, e.g., 135.degree. C. to 140.degree. C. in U.S. Pat. 
No. 3,075,948 and 180.degree. C. to 200.degree. C. in U.S. Pat. No. 
3,646,155. The one-step process, moreover, is not readily adaptable to 
conventional extruders currently operated on production lines and new 
extruders and associated equipment must be purchased and installed in 
order to carry out the one-step process or difficult and expensive changes 
must be made if conventional extruders are converted. 
Mixers are often employed at the discharge ends of extruders for the 
purpose of insuring the uniformity of the material being extruded. U.S. 
Pat. Nos. 4,169,679 and 4,302,409 disclose mixer heads adapted to be 
attached to the discharge end of an existing extruder forwarding screw by 
means of screw threads or any other means. The mixer head is disposed in 
the extruder barrel between the screw and the die and turns with the screw 
to mix the compacted, molten polymer delivered to it by the forwarding 
screw. A fluid additive, such as a blowing agent, can be introduced 
through the barrel wall to the molten polymer at the upstream end of the 
mixer head. Neither of these patents disclose the addition of a 
hydrolyzable, olefinically unsaturated silane or a peroxide activator or a 
silanol condensation catalyst to the polymer nor do they disclose 
conducting a grafting reaction in the extruder as a means for producing a 
crosslinkable polymer composition. 
U.S. Pat. Nos. 2,540,146 and 3,035,303 illustrate the use of mixing heads 
constructed on the downstream end of an extruder screw upstream from the 
extrusion die but fail to disclose or suggest the provision of a mixer 
head adapted to be attached at the downstream end of an existing extruder 
of conducting a grafting reaction to produce a crosslinkable polymer 
composition. 
Mixer heads which can be adapted to be fitted onto existing extruders are 
disclosed in U.S. Pat. No. 4,419,014 and British Pat. No. 930,339 in which 
the mixing elements on the facing surfaces of the rotor and stator are 
cavities. The molten polymer is forced by the forwarding screw through the 
cavities which apply a shearing, mixing action on the polymer as the rotor 
turns. British Pat. No. 1,475,216 discloses a mixer head that can be 
adapted to be fitted onto existing extruders in which the mixer head 
utilizes grooves and lands on the facing surfaces of the rotor and stator. 
None of these patents disclose or suggest the possibility of carrying out 
the grafting reaction in the mixer head to produce a crosslinkable polymer 
composition. 
SUMMARY OF THE INVENTION 
This invention is based on the unexpected discovery that the grafting 
reaction of a hydrolyzable, olefinically unsaturated silane onto a polymer 
such as polyethylene can be carried out in a mixing head mounted on and 
powered by an extruder and to which the polymer, in compacted, melted 
form, is fed by the extruder. While the compacted, melted polymer is fed 
to the mixer, compounding ingredients including the silane, a free-radical 
generator to initiate the grafting reaction in the mixer and, preferably, 
a silanol condensation catalyst to catalyze the subsequent crosslinking 
reaction are injected into the compacted, molten polymer just before or 
just after it is fed into the mixing head. The silanol condensation 
catalyst can be added with the compound ingredients, or further downstream 
in the mixer or can be added to the polymeric material after extrusion. 
The invention is also based on the discovery that it is not necessary to 
pass the silane, free-radical activator and polymer through the entire 
length of an extruder in order to carry out the grafting reaction to the 
extent required to form a crosslinkable composition. It was also 
discovered that, in the method of the present invention, it is not 
necessary to use more than one extrusion, i.e., it is not necessary to 
extrude the polymer, silane and free-radical catalyst to form the grafted 
copolymer and then extrude the resulting grafted copolymer with a silanol 
condensation catalyst to form the crosslinkable composition. It was 
furthermore discovered that, pursuant to this invention, it is not 
necessary to use the special types of extruders heretofore required by the 
one-step process nor are special temperature controls necessary as 
previously required in the one-step process. The present invention is 
highly advantageous in permitting the conversion of existing extruders of 
the conventional type to the production of shaped crosslinkable polymer 
products and avoids the excessive expenses of purchasing, and installing 
specialized extruders and complex extruder controls as is the case with 
the one-step process. 
The method of this invention produces a shaped, crosslinked, extruded, 
polymeric product by the steps comprising: 
(a) feeding a thermoplastic polymer capable of being cross-linked by a 
hydrolyzable olefinically unsaturated silane into the feed zone of an 
extruder having a forwarding screw and a barrel in which the screw is 
positioned and rotated to advance the polymer through the barrel; 
(b) compacting and melting the polymer in the barrel; 
(c) passing the resulting compacted, melted polymer through an extruder 
mixer positioned at the discharge end of the extruder, the mixer having a 
hollow stator in axial alignment with the discharge end of the barrel to 
receive compacted, melted polymer therefrom and a rotor positioned within 
the stator in axial alignment with the screw and rotatable thereby within 
the stator, the surface of the rotor facing the stator being formed with 
mixing elements subjecting the compacted, melted polymer passing through 
the mixer to high shear mixing action; 
(d) injecting proportionate amounts of compounding ingredients comprising a 
hydrolyzable olefinically unsaturated silane, a free-radical generator 
and, preferably, a silanol condensation catalyst into the compacted, 
melted polymer after compacting and melting the polymer in the extruder 
barrel; 
(e) blending the compounding ingredients and the compacted, melted polymer 
in the mixer until the hydrolyzable silane is grafted to the polymer; 
(f) extruding the resulting mixture out of the mixer through an extruder 
die to form a product of the required final shape; and 
(g) subjecting the product to the action of H.sub.2 O in the presence of a 
silanol condensation catalyst until the polymer therein is crosslinked. 
The apparatus used to carry out the method of this invention comprises an 
extruder having: 
(a) a hollow barrel; 
(b) a forwarding screw rotatably mounted in the barrel to advance a 
thermoplastic polymer therethrough and to compact and melt the polymer 
therein; 
(c) an extruder mixer positioned at the discharge end of the extruder, the 
mixer having a hollow stator in axial alignment with the discharge end of 
the barrel to receive compacted, melted polymer therefrom, and a rotor 
positioned within the strator in axial alignment with the screw and 
rotatable thereby within the stator, the surface of the rotor facing the 
stator being formed with mixing elements for subjecting the compacted, 
melted polymer passing through the mixer to rapid distributive mixing 
action; 
(d) injection means positioned in the upstream end portion of the stator 
for injecting fluid compounding ingredients into the compacted, melted 
polymer passing through the stator, the injection means having a discharge 
tip disposed below the surface of the compacted, melted polymer flowing 
through the stator; and 
(e) one-way valve means connected to the injection means to allow the flow 
of compounding ingredients into the compacted, melted polymer but prevent 
flow out of the stator into the injection means. 
The invention is concerned with the crosslinking of polyethylene extrusions 
by the injection of a special silane formulation into molten polyethylene 
and by incorporating it into the molten polyethylene by using a mixing 
device retro-fitted to a conventional plastics extruder. A preferred 
mixing device is known as a cavity transfer mixer which very rapidly 
incorporates the silane formulation so that uniform grafting of the silane 
onto the polyethylene takes place within the mixer. The mixing device is 
easily fitted onto conventional extruders enabling extrusion companies to 
adapt existing extrusion lines to produce crosslinked polyethylene 
products, the grafted extrusions being crosslinked by exposure to water. 
The products are principally pipes and cables but other products which 
benefit from higher service temperature capabilities; for example foam, 
film, profiles, sheets, beams, rods and the like, may also be made by this 
method of this invention. 
The method of this invention is not confined to extrusions, e.g., cable 
insulation and pipe, but may be used also for blow moldings and injection 
moldings. 
Polyethylene is well suited to the manufacture of cold water pipes. The low 
heat distortion temperature of uncrosslinked polyethylene, however, 
restricts its applications to low temperature uses. Crosslinked 
polyethylene pipes can be used for hot water services; such applications 
being covered by DIN 16892 standard and Avis 14+15/81-100. Crosslinked 
polyethylene pipes made by existing crosslinking processes are costly 
because: 
(1) Straight peroxide crosslinking (i.e. no grafted silane crosslinker) has 
a low output rate and uses large amounts of peroxide. 
(2) The two stage silane process (e.g. U.S. Pat. No. 3,646,155) is 
expensive to operate. 
(3) The one stage silane process (e.g. U.S. Pat. No. 4,117,195) requires 
very high capital cost equipment. 
The availability of low cost machinery for the one stage silane process 
would overcome these problems and generally increase the application of 
crosslinked polyethylene pipes for hot water uses. Furthermore, if an 
under-utilised polyethylene cold water pipe extrusion plant could be 
easily adapted to produce crosslinked polyethylene hot water pipes, then 
manufacturing costs for hot water pipe would be comparable with that of 
pipe for cold water service. 
This problem has been solved by the present invention by the injection of a 
silane formulation into a mixing device fitted between the extruder and 
die of a conventional polyethylene pipe extruder such that the silane 
formulation is very rapidly incorporated into the polymer melt and 
grafting of the silane to the polymer is achieved within the mixer. The 
rapid incorporation and grafting can be satisfactorily achieved by using a 
cavity transfer mixer as described in U.S. Pat. No. 4,419,014 fitted with 
an injector having a non-return valve for injecting the silane 
formulation. The present invention enables the production of crosslinked 
polyethylene (XLPE) extrusions such as pipes for hot water applications on 
extrusion lines originally used or intended for the extrusion of 
non-crosslinked polyethylene. This had not been previously technically and 
economically feasible. 
The present invention can be applied also to the extrusion of 
cable-insulation and sheathing, film, foam, profiles, rods, beams and 
sheets to increase temperature resistance as well as mechanical 
properties, physical properties, stress cracking resistance, and 
resistance to gas and moisture permeability in polymers such as 
polyethylene.

FIG. 1 illustrates an extruder having a feed-transport zone 2, a 
compression-melting zone 4, and a metering-pumping zone 6. The extruder 
comprises a hopper 8, a barrel 10 and a forwarding screw 12. The extruder 
is also provided with cooling means 14 at the upstream portion of the 
feed-transport zone 2, and separate heating and cooling units 16 around 
the downstream portion of the feed-transport zone 2, the compression 
melting zone 4 and the metering-pumping zone 6 for the purpose of 
controlling the temperatures in the various zones. 
A mixer 18 is mounted on the downstream end of the extruder and comprises a 
stator 20 bolted to the barrel 10 and a rotor 22 fixed to the forwarding 
screw 12, as by screw threads (not shown), to rotate with the screw 12. A 
die 24 is fixed to the downstream end of the mixer 18 by means of a clamp 
26 or other suitable means and heating units 28 are provided around the 
stator 20 and die 24. The mixer 18 can be of any conventional type and is 
here shown as a cavity transfer mixer of the type described in detail in 
U.S. Pat. No. 4,419,014. 
An injector 30 passes through the upstream wall of the mixer 18. The outer 
end of the injector 30 is connected to a one-way valve 32 which is 
connected to a delivery system 34 for the compounding ingredients 
including the hydrolyzable, olefinically unsaturated silane, free radical 
generator and silanol condensation catalyst. The delivery system as shown 
in FIG. 1 comprises a reservoir 36 containing the compounding ingredients, 
a pump 38 and tubing 40 connecting the outlet of the reservoir 36 to the 
inlet of the pump 38. The reservoir 36 is provided with a suitable 
volumetric and gravimetric control (not shown). For laboratory trials a 
burette is a convenient reservoir. The outlet of the pump 38 is connected 
by tubing 42 through a T-connector 44 to the inlet of one-way valve 32. 
The T-connector is also connected to a pressure transducer 46 which is 
connected to a recording instrument (not shown). The space above the 
compounding ingredients in the reservoir 36 is vented through a 
dessicant-filled container 48 to the atmosphere. 
Referring to FIG. 2, there is shown in enlarged section in injector 30 
connected to the one-way valve 32. The injector 30 comprises a long tube 
50 of sufficient length to pass completely through the wall of stator 20 
and terminate very close to the rotor 22 such that the inner tip 52 of the 
injector is well below the surface of polymeric material flowing in the 
space between the rotor 22 and stator 20. The inner surface of the tip 52 
is formed on its inner end with a valve seat that mates with a valve head 
54 disposed on the inner end of a long stem 56 that extends coaxially 
through said tube. The outer end of the stem 56 is fixed to a slide 58, as 
by screw threads (not shown) and a lock nut 60. The slide 56 is slidably 
mounted in a chamber 62 and is adapted to slide between the forward wall 
64 of the chamber 62 and its rearward wall 66. A coil spring 68 is 
positioned coaxially with stem 56 and bears upon the slide 58 and forward 
wall 64 to bias the slide 58 and stem 56 outwardly and cause the valve 
head 54 to seat against the valve seat on tip 52. When the force of 
pressure within tube 50 acting on the inner surface of valve head 54 
exceeds the force of pressure bearing on the outer surface of said valve 
head and the bias force of the coil spring 68, the valve head 54, valve 
stem 56 and slide 58 move to unseat the valve head from the seat on tip 52 
and thereby open the valve and permit flow of fluid out of the tube 50 
into the polymeric material occupying the space between the rotor 22 and 
stator 20. The outer end of chamber 62 is connected to tubing 42 which is 
connected to pump 38 which delivers fluid compounding ingredients to the 
chamber 62. Bores 70 are provided through slide 58 to permit passage of 
fluid past the slide 58. 
The mixer 18 can be of any conventional type and is shown in the drawings 
as a cavity transfer mixer described in detail in U.S. Pat. No. 4,419,014, 
the disclosure of which is incorporated herein by reference. FIG. 3 
illustrates the arrangement of cavities 72 around the inner circumference 
of the stator 20 and the cavities 74 around the outer circumference of 
rotor 22. The facing surfaces on the stator 20 and rotor 22 are formed 
with respective pluralities of semispherical cavities 72 and 74 
respectively. The cavities 74 on rotor 22 are disposed in a plurality of 
circumferentially extending rows. The adjacent rows of cavities on the 
rotor are circumferentially displaced such that the center of each cavity 
74 in a given row lies midway between the centers of the two nearest 
cavities 74' in each adjacent row. This can best be seen in the developed 
view of FIG. 4, wherein circles 74a, 74b and 74c represent cavities in one 
row in the rotor, circles 74a', 74b' and 74c' represent cavities in the 
adjacent row on one side and 74a", 74b" and 74c" represent cavities in the 
adjacent row on the other side. In a similar manner, the cavities 72 on 
the stator 20 are disposed in a plurality of circumferentially extending 
rows, adjacent rows on the stator being displaced such that cavities 72 in 
a given row are offset by half the distance between the centers of the two 
nearest cavities 72' in each adjacent row. 
In addition, FIG. 4 also illustrates the axial offset of the 
circumferential rows of cavities 72 on the stator 20 in relation to 
adjacent circumferential rows of cavities 74 on the rotor 22. More 
specifically, the circumferential line joining the centers of any given 
row of cavities 72 on the stator 20 lies midway between the two 
circumferential lines on either side of it joining the centers of cavities 
74 on the rotor 22. The cavities 72 and 74 overlap such that molten 
polymer passing from the extruder barrel 10 to the die 24 is subjected to 
laminar shear within the cavities and cut and turned as it passes 
backwards and forwards between cavities on the rotor 22 and stator 20. Any 
overlapping cavity configuration can be used, but hemispherical cavities 
provide good streamlining and minimal restriction to flow of polymer melt. 
Preferably, the injector 30 is so positioned that the tip 52 is located 
just upstream from the most upstream cavity or at the most upstream 
circumferential row of cavities 74 on the rotor 22. 
In operation, the extruder is operated in a normal fashion by loading 
polymeric material, e.g., polyethylene pellets, into the hopper 8 where it 
is fed to the feed-transport zone 2 which delivers it to the compression 
and melting zone 4 where it is converted to a compacted melted polymeric 
material. The compacted, melted polymeric material is delivered to the 
metering-pumping zone 6 and thence into the mixer 18. Compounding 
ingredients are pumped, in appropriate amounts, from the reservoir 36 
through the injector 30 into the compacted, melted polymeric material as 
it enters the mixer 18. The compounding ingredients and compacted, melted 
polymeric material are rapidly and well mixed in the mixer 18. It was 
unexpectedly found that residence time and temperature in the mixer 18 can 
be provided to generate free radical sites in the polymeric material and 
complete grafting of the silane onto the polymeric material to a 
sufficient extent to allow an adequate extent of crosslinking upon 
subsequent exposure to water. It was also surprising to find that mixing 
of the molten polyethylene and the compounding ingredients can be achieved 
adequately in the relatively short mixer to provide relatively uniform 
mixing and no troublesome formation of small gels. The grafted 
polyethylene then travels through the die 24 and through cooling and 
haul-off systems as normally used for polyethylene extrusion. The 
extrusion is then exposed to hot water or moist conditions in known ways 
until the grafted polymer is adequately crosslinked. 
It has been found that the rotational speed of the forwarding screw 12 can 
be varied over a wide range, e.g., from 30 to 105 rpm for a 38 mm diameter 
forwarding screw. Also, the temperature in each of the three zones can be 
varied over wide ranges and basically depends upon the melting 
characteristics of the polymeric material being extruded. For example, in 
the case of polyethylene the temperature of polyethylene in the 
feed-transport zone 2 can range from 100.degree. C. to 145.degree. C., and 
the temperature of the material in the compression-melt zone 4 should be 
higher than the temperature of the material entering said zone and of 
course above the melting point of the polyethylene, and can range from 
135.degree. C. to 155.degree. C. The temperature of the polyethylene in 
the metering-pumping zone 6 is higher than the temperature of the material 
entering said zone and can range from 145.degree. C. to 180.degree. C. 
Representative temperatures of the polyethylene in the mixer 18 can be 
varied over a wide range of 145.degree. C. to over 210.degree. C., 
typically being, of course, higher than the temperature of the material 
entering the mixer. These temperatures are based on readings taken from 
controller thermocouples (not shown) fitted into the metal of the extruder 
barrel 10 but the polymer melt temperature could be higher as a result of 
mechanically produced heat. The temperature of the polyethylene leaving 
the die 24 need not exceed the temperature of polyethylene entering the 
die, and representatively range from 155.degree. C. to 250.degree. C. The 
output rate depends largely on the type and size of extruder used and, for 
a 38 mm diameter extruder operating at a screw speed in the 
above-mentioned range, can range from 25 grams per minute or less to 350 
grams per minute or more. 
The proportion of hydrolyzable, olefinically unsaturated silane based on 
the weight of polymeric material, e.g., polyethylene, also is not narrowly 
critical and can range from 0.1 to 10 wt. %, preferably 0.7 to 3 wt. %, of 
silane based on the total weight of polymeric material. The amounts of 
free radical generator also is not narrowly critical and can be varied 
over wide ranges, for example, from 0.01 wt. % to 0.3 wt. %, preferably 
0.05 to 0.2 wt. %, based on the total weight of polymeric material. 
Furthermore, the proportion of silanol condensation catalyst is not 
narrowly critical, illustratively ranging from 0.01 to 0.2 wt. %, 
preferably 0.02 to 0.08 wt. %, based on the total weight of polymeric 
material. 
Polymers that are suitable for grafting and crosslinking by the present 
invention include the polymers of alpha-olefins having 2 to 6 carbon atoms 
such as ethylene, propylene, 1-butene; 1-pentene; 1-hexene; isobutylene; 
2-methyl-1-butene; 3-methyl-1-butene; 2,2-dimethylpropene; 
2-methyl-1-pentene; 3-methyl-1-pentene; 4-methyl-1-pentene; 
2,2-dimethyl-1-butene; 2,3-dimethyl-1-butene; 3,3-dimethyl-1-butene; and 
2-ethyl-1-butene. The olefin polymer reactant employed in the invention is 
either a homopolymer of an alpha-olefin having 2 to 6 carbon atoms or a 
copolymer of two alpha-olefins, e.g., copolymers of ethylene and 
propylene. Modified poly-alpha-olefins such as chlorinated polyethylene 
can be used in this invention. Any polymer that is capable of being 
extruded and is capable of being crosslinked by a hydrolyzable 
olefinically unsaturated silane is suitable for use in this invention. In 
addition to polyethylene, any polymer or copolymer chemically suitable for 
silane crosslinking can be used, or blends of such polymers. Further, 
examples are ethylene-vinyl acetate copolymers, polyamides and 
ethylene-propylene rubbers. 
Hydrolyzable olefinically unsaturated silanes suitable for grafting onto 
and crosslinking the polymers according to this invention include 
organofunctional silanes of the general formula: 
EQU R(CH.sub.2 CH.sub.2 CH.sub.2).sub.m Si(R.sub.1).sub.3-n X.sub.n 
wherein R represents a monovalent olefinically unsaturated hydrocarbon or 
olefinically unsaturated hydrocarbonoxy group which is reactive with the 
free radical sites generated in the polymer by the free radical generator, 
R.sub.1 represents an hydrolysable organic group such as an alkoxy group 
having 1 to 12 carbon atoms (e.g. methoxy, ethoxy, butoxy), aralkoxy 
groups (e.g. phenoxy), aliphatic acyloxy groups having 1 to 12 carbon 
atoms (e.g. formyloxy, acetoxy, propionoxy), oxymo or substituted amino 
groups (alkylamino and arylamino), X represents a monovalent alkyl, aryl 
or aralkyl group (e.g. ethyl, methyl, propyl, phenyl, benzyl), m is 0 or 1 
and n is 0, 1 or 2. 
Some representative examples of the unsaturated silanes applicable in the 
present process are vinylmethyldimethoxysilane, vinyltriethoxysilane, 
vinyltrimethoxysilane, allyltriethoxysilane, allylmethyldiethoxysilane, 
allyltriethoxysilane, diallyldimethoxysilane, allylphenyldiethoxysilane, 
methoxyvinyldiphenylsilane, dodecenylvinyldipropoxysilane, 
didecenyldimethoxysilane, didodecenyldimethoxysilane, 
cyclohexenyltrimethoxysilane, hexenylhexoxydimethoxysilane, 
vinyl-tri-n-butoxysilane, hexenyltri-n-butoxysilane, allyldipentoxysilane, 
butenyldodecoxysilane, decenyldidecoxysilane, dodecenyltrioctoxysilane, 
heptenyltriheptoxysilane, allyltripropoxysilane, divinyldiethoxysilane, 
diallyldi-n-butoxysilane, pentenyltripropoxysilane, 
allyldi-n-butoxysilane, vinylethoxysilane, sec.-butenyltriethoxysilane, 
5-benzyl-6-(dinonoxysilyl)-1-hexene, 
4-phenyl-tri-(5-propoxysilyl)-1-pentene, 2-cyclopentyl-3-silyl-1-propene, 
0-(trimethoxysilyl) styrene, 0-diphenoxysilyl)-p-octylstyrene, 
0-(benzyloxydichlorosilyl)-0'-methylstyrene, 
3-(tripropoxysilyl)-5-methylvinylcyclohexane, 
5-cyclohexyl-6-(triethoxysilyl-1-hexene, (methylcyclopentenyl) 
dibutoxysilane. 
Preferably the silanes will contain two or three hydrolysable organic 
groups and a vinyl or allyl group as the group reacting with the free 
radical sites formed in the polymer by the free radical generator. 
As the free radical generating compound there may be used any compound 
which is capable of producing free radical sites in the polymer, the 
reaction conditions depending on temperature and retention time in the CTM 
needed for achieving a suitable half life time. The preferred free-radical 
initiators are organic peroxides and peresters such as 
tert.-butylperoxyneodecanoate, tert.-butylperoxyneohexanoate, 
tert.-amylperoxypivalate, tert.-butylperoxypivalate, bis 
(3,5,5-trimethylhexanoyl) peroxide, bis (2-methylbenzoyl) peroxide, 
di-decanylperoxide, di-octanoylperoxide, di-lauroylperoxide, 
tert.-butylperoxy-2-ethylhexanoate, tert.-butylperoxy diathylyacetate, 
tert.-butylperoxybutyrate, 
1,1-di.tert.-butylperoxy-3,5,5-trimethylcyclohexane, 
1,1-di.tert.-butylperoxy cyclohexane, 
tert.-butylperoxy-3,5,5-trimethylhexanoate, tert. butylperoxy 
isopropylcarbonate, 2,2-di.tert.-butylperoxy butane, tert.-butylperoxy 
stearylcarbonate, tert.-butylperoxy acetate, tert.-butylperoxy benzoate, 
4,4-di.tert. butylperoxy-n-butylvalerate, dicumylperoxide, bis (tert. 
butylperoxyisopropyl) benzene, di.tert. butylperoxide, 2,2-azo bis 
(2,4-dimethylvaleronitrile), azo-bisisobutyronitrile, di-benzoylperoxide, 
2,5-dimethyl-2,5-bis (tert.-butylperoxy) hexane, tert. butyl peroctoate, 
tert. butyl perbenzoate and tert. butylcumylperoxide as well as 
combinations thereof. 
Silanol condensation catalyst used for the crosslinking of the polymer 
under the influence of water molecules are metal carboxylates, such as for 
example: dibutyltin dilaurate, dioctyltin dilaurate, stannous acetate, 
stannous octoate, dibutyltin dioctoate, di-octyl tin-bis 
(isooctylmaleate), di-octyl-tin-bis (isooctylthioglycolate), as well as 
organometal compounds such as the titanium esters and chelates, for 
example, tetrabutyl titanate, tetranonyl titanate, and bis 
(acetylacetonyl) di-isopropyl titanate, organic bases, such as, 
ethylamine, hexylamine, dibutylamine, and piperidine, and acids, such as, 
fatty acids and meneral acids. 
Further additives which can be incorporated into the hot polymer melt 
through the injector into the mixing head (e.g., the cavity transfer 
mixer, CTM) are any of the antioxidants and heat stabilizers commonly used 
in the processing of polyolefines and combinations thereof. In addition, 
minerals for improving flame retardancy or as an internal source of water 
for the crosslinking, e.g. aluminum trihydrate, zeolite or minerals like 
carbon black, chalk, talc, mica, silica, silicates and others, can be 
injected into the polymer as it enters the mixing head or CTM. The silanes 
and other additives can be metered into the mixing head or CTM separately 
of preferably, as a more efficient way, as pre-manufactured binary, 
ternary, or quaternary formulations. Such formulations contain the silane 
and condensation catalyst or free radical initiators or inhibitors or 
stabilizers or combinations thereof. The silanes alone or as binary, 
ternary, quaternary formulations with the free radical initiators, 
condensation catalysts, antioxidants, etc. can be used for the 
pre-treatment of the above-mentioned minerals (aluminum trihydrate, 
zeolite, silica, etc.). These pre-treated fillers can be then more easily 
incorporated into the hot-melt through the CTM mixing head. The system of 
this invention can be modified to allow the incorporation of other 
additives, both liquids and solids, injected either with the silane 
mixture, by a separate pump or through a separate open port. If the 
addition is made separately after the silane, the mixer can be extended 
with a CTM configuration, or alternative mixing device, for example, a 
pinned mixer, a screw, or a static mixer. Furthermore, the products can be 
manufactured pursuant to this invention using a molten polymer pumping 
process and the mixer can be driven by the polymer pumping screw or it can 
be driven separately. Twin screw extruders can also be used with these 
various configurations. 
EXAMPLES 
The following examples are presented. The extruder used in each example is 
illustrated in FIG. 1 and is a Bone Bros. single screw extruder having a 
barrel diameter of 1.5" (38 mm), a screw length of 36" (915 mm), a screw 
L/D of 24:1, a feed-transport zone length of 8D (12", 305 mm), 
compression-metering zone length of 8D (12", 305 mm), a metering-pumping 
zone length of 8D (12", 305 mm), a channel depth in the feed-transport 
zone of 0.248" (6.3 mm), a channel depth in the metering-pumping zone of 
0.083" (2.1 mm), a nominal compression ratio (depth ratio) of 3:1, a pitch 
of 1D and a 7.5 horsepower, variable speed AC commutator motor. The 
extruder barrel is provided in the three zones with 3 term temperature 
controllers operating electrical resistance heating and proportional 
cooling for each of the three zones. 
The mixer employed in the example is diagrammatically shown in the drawings 
and described in U.S. Pat. No. 4,419,014. Each of the stator and rotor 
used has seven circumferential rows with five cavities in each row. The 
mixer used has a nominal diameter of about 1.5 inch (38 mm) and a nominal 
L/D ratio of 4:1. In each example, an 8 mm diameter strand die having a 
streamlined entry was used. In each example, the compounding ingredients 
were injected through the non-return valve 32 and injector 30 shown in 
FIGS. 1 and 2 and the tip 52 of the injector was positioned below the 
surface of the melt flowing into the mixer. A Bran and Lubbe pump was used 
to pump the compounding ingredients through the one-way valve and 
injector. The compounding ingredients used in the examples is called 
crosslinking formulation, referred to as "XL Form." in the examples, and 
contained 89 wt. % vinyltrimethoxysilane, 8 wt. % dicumylperoxide and 3 
wt. % dibutyltin dilaurate. 
In addition, the general extrusion conditions described in the examples 
refer to metal temperatures of the barrel at B1, B2 and B3. These 
temperatures were measured at the midpoint of each of the feed-transport 
zone 2, compression-melting zone 4 and metering-pumping zone 6, 
respectively. Also, the temperature given for the CTM, i.e., the cavity 
transfer mixer, is a metal temperature measured at the midpoint of the 
CTM. Similarly, the die temperature is a metal temperature measured at the 
midpoint of the die. The pump pressure given is the pressure generated by 
pump 38 in the crosslinking formulation being pumped through tubing 42, 
one-way valve 32 and injector 30. 
In the examples, samples of the extrudate from the die and samples of 
extrudate taken from three bleed ports 1, 2 and 3 located at, 
respectively, the second, fourth and sixth circumferential rows of 
cavities, were tested for crosslink density by xylene extraction. In this 
test, shavings of the extrudate were taken, weighed and placed into 100 ml 
of xylene which was boiled for seven hours after which the resulting 
material was vacuum filtered on the preweighed filter paper to recover all 
of the residue remaining undissolved in the xylene. The residue represents 
the crosslinked portion of the extrudate and the dissolved portion 
represents the uncrosslinked portion. The weight percent of insoluble 
material, i.e., crosslinked polymer, in the extrudate is calculated by 
dividing the weight amount of residue by the weight amount of initial 
sample placed into the xylene and multiplying by 100. 
The test results given in the tables of the examples designated "Residue 
(dry) G (%)"" provides the hot xylene extraction test results on samples 
of extrudate that were measured and immediately stored in a desiccator to 
avoid any contact with moisture; the G standing for grafted composition 
and implying little or no crosslinking because of the avoidance of any 
contact with moisture. The designation "Residue (wet) XL (%)" refers to 
the hot xylene test results performed on samples of the extrudate that 
were simply stored in a polyethylene bag until testing and which, prior to 
testing, were boiled in water for four hours to crosslink the grafted 
polymeric material prior to subjecting it to hot xylene extraction. 
Additional samples of extrudate in the examples were immediately 
compression molded into 150.times.150.times.1 mm sheets using contact 
pressure at 170.degree. C. for 5 minutes followed by the application of 
ten tons pressure with water cooling. Strips were cut from the resulting 
molded sheets and were stored for 24 hours in vacuum flasks which were 
filled with boiling water to crosslink the grafted polymeric material in 
the strips. Thereafter, dumb-bell shaped test pieces were cut from the 
crosslinked strips of molded sheets in accordance with BS 903, Part A2, 
Type 2, i.e., the dumb-bell test pieces had an overall length of 75 mm, a 
width of ends of 12.5.sup..+-. 1 mm, a length of narrow parallel portion 
of 25.sup..+-. 1 mm, a width of narrow parallel portion of 4.0.sup..+-. 
0.1 mm, a small radius of 8.sup..+-. 0.5 mm, and a large radius of 
12.5.sup..+-. 1 mm. The dumb-bell specimens are then subjected to a hot 
deformation test pursuant to IEC 502, 1983 to determine the maximum 
extension under load and permanent extension of the sample. In the hot 
deformation test, each test piece is suspended at one end by a grip in an 
oven and a lower grip is attached to the lower end of each test piece for 
the purpose of suspending weights therefrom. In operating the test, a load 
of 20N/cm.sup.2 (N being a Newton) was applied to the test piece for 15 
minutes while suspended in the oven at a temperature of 200.degree. C. The 
load of 20N/cm.sup.2 is based on the cross-sectional area of the neck of 
the dumb-bell shaped test pieces. The test pieces are initially formed 
with spaced marker lines extending in parallel, transversely across the 
narrow parallel portion or neck. The initial, pretest distance separating 
the marker lines is 20 mm before exposure to load and elevated 
temperature. After 15 minutes under the load of 20N/cm.sup.2 at 
200.degree. C., the distance between the marker lines is measured and the 
increase in distance over the initial pretest distance is divided by the 
initial pretest distance and multiplied by 100 to give the percent 
extension at 200.degree. C. which is reported as "Extn. at 200.degree. C. 
(%)" in the tables of the examples. A lower percent extension at 
200.degree. C. indicates a higher degree of crosslinking and a greater 
percent extension indicates a lower degree of crosslinking. 
After measuring the distance between the marker lines while the specimen is 
under the load of 20N/cm.sup.2 at 200.degree. C., the load is then removed 
and the test pieces are allowed to recover for 5 minutes at 200.degree. C. 
They then are removed from the oven and allowed to cool slowly to ambient 
temperature after which the distance between the marker lines is measured, 
from which distance the initial (pretest) distance between the marker 
lines is subtracted to give the mm of permanent extension imparted to the 
test piece. The mm of permanent extension is then divided by the initial 
distance between the marker lines and multiplied by 100 to give the 
percent permanent extension, and is reported as such in the tables. The 
lower the percentage of permanent extension generally indicates a higher 
level of crosslinking. For XLPE insulation and sheathing applications, the 
maximum elongation tolerable is 175% and the maximum permanent elongation 
tolerable is 15% according to present practices. 
EXAMPLE 1 
The extruder was started and medium density polyethylene (Vestolen-A4516) 
having a melt flow index (ISO/R1133 190/2 procedure 4) of 7 g/10 min. and 
(ISO/R1133 190/5 procedure 5) of 20 g/10 min. was fed to the hopper of the 
extruder. The density (ISO/R1183) of the polyethylene was 0.945 
g/cm.sup.3. The screw speed as given in Table 1 below was set and the B1, 
B2, B3, CTM and die temperatures were measured and are listed in Table 1 
which also provides the motor current and pump pressure for each of the 
screw speeds specified. The extruder output rate at each screw speed also 
was measured by cutting and weighing samples at 1 min. intervals and the 
output rate determined by this method for each screw speed is listed. 
Injection of the XL Formulation was then started with the pump 38 adjusted 
to provide the desired concentration of XL Formulation in the polymeric 
material given in Tables 2, 3 and 4 below. The output rate was measured 
again and the injection pump 38 was adjusted as necessary in order to 
correlate the concentration of XL Formulation injected to any changes in 
the output rate of polyethylene being fed to the mixer 18 by the extruder. 
Following establishment of steady state processing conditions, three 
samples of extrudate were taken in each instance, one being stored in the 
desiccator for subsequent xylene extraction testing for determining 
"Residue (dry) G (%)", a second sample being stored in a polyethylene bag 
for subsequent boiling for four hours in water and subsequent xylene 
extraction testing to provide "Residue (wet) XL (%)" given in each 
instance in Tables 2, 3 and 4, and the third sample being immediately 
compression molded for the purpose of providing the "Extn. at 200.degree. 
C. (%)" and "Permanent extension" measurements. The results of the testing 
and measuring of the samples at various XL Formulation concentrations and 
screw speeds are given in Tables 2, 3 and 4 below. Table 4 provides the 
test results for extrudates removed from bleed ports 1, 2 and 3 at the 
designated screw speeds and concentrations of XL Formulation. 
The results provided in Tables 2 and 3 show that more than 50% and as high 
as 80% of each of the polymeric extrudate was crosslinkable and that the 
resulting crosslinked extrudates are acceptable for insulation and 
sheathing applications. The results of Table 4 show a steady increase in 
grafting as the polymeric material progressed through the mixer and the 
degree of grafting just before the polymeric material left the mixer was 
sufficiently high to provide 65% or more crosslinked polymer. 
TABLE 1 
__________________________________________________________________________ 
General Extrusion Conditions 
Screw 
Temperatures (.degree. C.) 
Motor 
Output 
Pump 
Speed 
Barrel Current 
Rate Pressure 
(rpm) 
B1 B2 B3 CTM Die (amps) 
(g/min) 
(Bar) 
__________________________________________________________________________ 
30 130 158 
168 181 180 5 63 22 
45 130 159 
168 176 180 5 115 25 
60 130 159 
169 177 181 5 150 23 
75 130 158 
179 180 181 4.5 208 26 
90 130 158 
178 176 181 5 250 33 
105 130 158 
170 177 181 6 281 34 
__________________________________________________________________________ 
TABLE 2 
__________________________________________________________________________ 
Influence of XL Formulation 
Screw Speed 
60 rpm 105 rpm 
__________________________________________________________________________ 
XL Form. concn. (%) 
1.6 1.8 
2.0 
2.2 1.6 
1.8 2.0 
2.2 
Residue (dry) G (%) 
5 5 13 15 8 15 10 16 
Residue (wet) XL (%) 
67 56 67 71 67 77 71 72 
Extn. at 200.degree. C. (%) 
150 67 45 -- 75 69 62 -- 
Perm. Extension (%) 
17.5 
10 2.5 
-- 5 2.5 2.5 
-- 
__________________________________________________________________________ 
TABLE 3 
______________________________________ 
Influence of Screw Speed At 2% XL Formulation Concentration 
Screw Speed (rpm) 
Test 30 45 60 75 90 105 
______________________________________ 
Residue (dry) G (%) 
24 16 13 12 7 10 
Residue (wet) XL (%) 
80 66 67 75 67 71 
Extn. at 200.degree. C. (%) 
26 39 45 41 47 62 
Perm. extension (%) 
-- -- 2.5 2 2.5 2.5 
______________________________________ 
TABLE 4 
______________________________________ 
Grafting During Progress Through The Mixer 
Screw Speed 60 rpm 105 rpm 
Bleed Port 1 2 3 1 2 3 
______________________________________ 
1.6% XL Form. 
Residue (dry) G (%) 
2 5 5 1 1 4 
Residue (wet) XL (%) 
35 64 76 10 67 74 
200.degree. C. Extn. % 
F F 45 F 32 35 
1.8% XL. Form. 
Residue (dry) G (%) 
4 9 12 1 7 22 
Residue (wet) XL (%) 
20 47 65 29 78 81 
200.degree. C. Extn. % 
F 40 55 F 61 -- 
______________________________________ 
Note: F designates tensile failure 
EXAMPLE 2 
The procedure of Example 1 was carried out except that instead of the 
polyethylene identified therein as Vestolen A4516, a different 
polyethylene, namely, Unifos DFDS4444, having a melt flow index (ASTM 
D1238) of 2.2 g/10 min. and a density (ASTM D1928C) of 922 kg/m.sup.3 was 
used. The general extrusion conditions are given in Table 5 and the test 
results are given in Tables 6, 7 and 8. 
TABLE 5 
__________________________________________________________________________ 
General Extrusion Conditions 
Screw 
Temperature (.degree. C.) 
Motor 
Output 
Pump 
Speed 
Barrel Current 
Rate Pressure 
(rpm) 
B1 B2 B3 CTM Die (amps) 
(g/mins) 
(bar) 
__________________________________________________________________________ 
30 125 148 
155 155 166 6.0 87 33 
45 125 148 
155 155 166 6.0 133 33 
60 125 148 
155 155 166 6.0 187 55 
75 125 148 
155 155 166 6.0 236 55 
90 125 148 
155 155 166 7.0 280 76 
105 125 148 
155 155 166 8.0 341 76 
__________________________________________________________________________ 
TABLE 6 
______________________________________ 
Effect of Screw Speed at 2.0% XL Formulation Concentration 
Screw Speed (rpm) 
Test 30 45 60 75 90 105 
______________________________________ 
Residue (dry) G (%) 
24 15 25 21 19 20 
Residue (wet) XL (%) 
75 77 82 77 78 67 
Ext. at 200.degree. C. (%) 
62 75 64 50 50 75 
Permanent extension (%) 
0 2.5 1.0 0 0 2.5 
______________________________________ 
TABLE 7 
______________________________________ 
Effect of XL Formulation Concentration 
Screw XL Formulation 
Speed Concentration % 
(rpm) 1.6 1.8 2.0 2.2 
______________________________________ 
Residue (wet) XL (%) 
60 60 72 64 77 
Residue (wet) XL (%) 
105 63 75 75 78 
______________________________________ 
TABLE 8 
______________________________________ 
Grafting During Progress Through The Mixer 
Screw Speed 
60 rpm 105 rpm 
Bleed Port 1 2 3 1 2 3 
______________________________________ 
2.0% XL Form. Residue 
(wet) XL (%) 3 49 75 34 71 82 
______________________________________ 
The results given in Tables 6 and 7 show that 60% or more, as high as 82%, 
of the polymeric material is crosslinkable and that the resulting 
crosslinked extrudates are acceptable for insulation and sheathing 
applications. The results of Table 8 illustrate a steady increase in the 
crosslinkability, i.e., in the degree of grafting, as the polymeric 
material passes through the mixer. 
EXAMPLE 3 
The procedure given in Example 1 was used except that in place of Vestolen 
A4516 polyethylene, there was used a polyethylene identified as Unifos 
NEWS8019, and LLDPE which has more potentially reactive sites than other 
polyethylenes, having a melt flow index (ASTM D1238) of 4 g/10 min. and a 
density (ASTM D1928C) of 934 kg/m.sup.3. The generaly extrusion conditions 
are given in Table 9 and Tables 10-13 provide the results at the indicated 
screw speeds and XL Formulation concentrations. 
TABLE 9 
__________________________________________________________________________ 
General Extrusion Conditions 
Screw 
Temperature (.degree.C.) 
Motor 
Output 
Pump 
Speed 
Barrel Current 
Rate Pressure 
(rpm) 
B1 B2 B3 CTM Die (amps) 
(g/mins) 
(bar) 
__________________________________________________________________________ 
60 126 151 
155 156 160 7 178 62 
75 126 151 
155 156 160 7.75 222 83 
90 126 151 
155 156 160 8.5 267-271 
90 
105 126 151 
155 156 160 10 314 93 
__________________________________________________________________________ 
TABLE 10 
__________________________________________________________________________ 
Smooth Extrusions At 90 rpm Screw Speed 
XL Form 
Concentration 
0 0.4 0.6 0.8 1.0 
1.2 1.4 
1.6 
__________________________________________________________________________ 
Residue (wet) 
2.1 18.3 
39.2 60.3 
75 89 61 
XL (%) 
Extension at 
&gt;200 
&gt;200 
&gt;200 
185 45 40 22.5 
20 
200.degree. C. (%) 
Permanent 
-- -- -- 18 5 5 0 0 
Extn. (%) 
__________________________________________________________________________ 
TABLE 11 
______________________________________ 
Residue (wet) XL (%) 
Screw Speed (rpm) 
60 75 90 105 
______________________________________ 
XL Form. concentration 
1.2% 74 69 75 65 
1.4% 89 79 89 83 
1.6% 66 78 61 66 
______________________________________ 
TABLE 12 
______________________________________ 
Extension at 200.degree. C. (%) 
Screw Speed (rpm) 
60 75 90 105 
______________________________________ 
XL Form concentration 
1.2% -- 37.5 40 32.5 
1.4% 32 26 22.5 19 
1.6% 59 24 20 -- 
______________________________________ 
TABLE 13 
______________________________________ 
Permanent Extension (%) After 5 Minutes Recovery Time 
Screw Speed (rpm) 
60 75 90 105 
______________________________________ 
XL Form. concentration 
1.2% -- 5 5 2.5 
1.4% 7.5 1.25 0 0 
1.6% 10 0 0 0 
______________________________________ 
The results given in Table 10 illustrates the increase in crosslinkability 
of polymeric extrudate as the proportion of crosslinking formulation 
(i.e., silane, free radical generator and silanol condensation catalyst) 
are increased and a crosslinkability of as much as 89 wt. % of the 
polymeric material is attainable and that crosslinked extrudates which 
have excellent hot extension properties can be made. Table 11 illustrates 
polymeric extrudates which are at least 61% crosslinkable and as much as 
89% crosslinkable. Tables 12 and 13 illustrate the excellent hot extension 
properties of the polymeric extrudates identified therein. 
EXAMPLE 4 
The procedure of Example 1 was carried out except that instead of the 
polyethylene described therein there was instead used a polyethylene 
identified as Hoechst GF 7740F2 having a melt flow index (ASTM D 1238) of 
0.5 g/min. and a density (ASTM D1928C) of 942 kg/m.sup.3. 
TABLE 14 
__________________________________________________________________________ 
Motor 
Pump Residue 
XL Screw 
Output Cur- Pres- 
Melt Temps, 
Dry, 
Wet, 
Form 
Speed 
Rate 
Temperatures, .degree.C. (1) 
rent sure 
.degree.C., 
CTM(2) 
G XL 
(%) (rpm) 
(g/min) 
B1 B2 B3 CTM Die 
(amps) 
(bars) 
IN OUT (%) (%) 
Comments 
__________________________________________________________________________ 
2.0 30 75 132 
173 
187 
209 191 
5.6 62 187 229 -- -- Surged badly. 
Surface very 
uneven but 
better during 
surges. 
2.0 45 114 130 
168 
184 
207 191 
6 7 188 228 -- -- Surged ceased 
and surface 
improved but 
still has knobbly 
appearance. 
2.0 60 161 130 
172 
184 
205 191 
5.75 10 189 221 4.2 52.1 
Surging returned 
Surface improve 
but has greasy 
film. 
2.0 75 210 130 
172 
188 
207 191 
5 10 189 225 -- -- Knobbly 
appearance 
__________________________________________________________________________ 
NOTE: 
(1) Metal temperatures taken on the extruder barrel, CTM and die. 
(2) Temperature of the molten polymeric material at, respectively, 
upstream and downstream ends of CTM.