Note: Descriptions are shown in the official language in which they were submitted.
7~%
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1 BACKGROUND OF THE INVENTION
1. Field of the Invention
3 This invention relates to an extrudable composition
4 capable of forming tubing, the composition comprised of a low
pressure, low density (LP-~D) hydrocarbon interpolymer, a
6 copolymer of ethylene with a vinyl ester of Cl-C30 monocarboxylic
7 acid and other alpha olefins in minor concentrations, an ultra-
8 violet (W) stabilizer and an anti-oxidant stabilizer.
9 2. Description of the Prior Art
Drip irrigation tubing is well known. Such tubing is
11 useful for drip i-rigation, e.g., to dispense water to orchards
12 and row crops. The popularity of drip irrigation has grown since
13 it was first discovered some 30 years ago. Crops grown through
14 drip irrigation yield more frui~ and better quality fruit than
other irrigation systems~
16 ~ Typically, drip irrigation tubing has a thic~ness from
17 about 0.1 mm to about 3.81 mm and an outside diameter from about
18 5 mm to about 51 mm. The tubing îs generally extruded from a
19 resin composition to form single and/or multiple chambered
tubing. Generally, it is desirable for the resin composition
21 to have ease of both extrudability and vacuum sizing. It is
22 desirable for the tubing to exhibit good flexibility, pressure
23 capability and smooth and glossy surfaces. The tubing also mus~
24 have superior environmental stress crack resistance. Very
important parameters are the pressure capabilities and resistance
26 to stress cracking.
27 Prior ar~ drip irrigation tubing has included off grade
28 blends of high pressure-low density polyethylene (HPLDPE)-
29 ethylene vinyl acetate ~EVA) copolymer resins, specifically
blends of EVA-HPLDPE copolymer having an EVA content of about 5%
. ~
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1 EVA-high density polyethylene (HDPE)-HPLDPE interpolymer
2 having an EVA content of 8% and an HDPE content of 10%, the
3 balance being HPLDPE; and LP-LD polyethylene. However, all of
4 the aforementioned tubing materials suffered from one or more
disad~antages, such as insufficient stress crack resistance or
6 press~re capabilities at elevated temperatures. LP-LD poly-
7 ethylene provides an excellent drip irrigation tubing, but it
8 is harder to extrude than the other materials~ Other prior art
9 materials used for drip irrigation tubing include off grade
film products such as HPLD polyethylene modified with rubbers, and
11 an ethylene-octene-l copolymer. mhe latter is difficult to
12 extrude, having a narrow molecular weight distribution which
13 leads to melt fracture during extrusion~
14 It is known to subject drip irrigation tubing to
irradiation to cross-link unsaturated bonds within the product
16 in order to eliminate stress crack problems by creating an
17 infinite molecular weight polymer. For example, tubing has been
18 subjected to electron beam irradiation to receive a total dose
19 between 10 and ll M.rads. Other components`present in extrudabl~
compositions typically used for drip irriga~ion t~-bing include
21 a W stabilizer and an anti-oxidant stabilizer. In view of the
22 fact that the tubing is used outdoors and is exposed to sunlight,
23 a UV stabilizer is necessary. Carbon black is a popular W
24 stabilizer. Also, during extrusion, it is necessary to have an
anti-oxidant to arrest polymer degradation via free radical
26 propagation.
27 3. Brief ~escription of the Invention
28 It now has been found that the following extr~dable
29 composition forms a drip irrigation tubing which, after being
cross-linked by irradiation, has excellent burst strength at
31 80C: (1) more than about 80% and less than about 97~ by weight
l ~ 57~
12~37
1 of a low pressure, low density hvdrocarbon interpolymer; (2) more
2 than about 2% and less than about 10% by weight of a copoly~er of
3 ethylene with a vlnyl ester of Cl-C30 monocarboxylic acid and
4 other alpha olefins in minor concentrations providing a
copolymer having a density between 0.91 and 0.94 gm/cm3i
6 (3~ more than about 0.01% and less than about 3% by wei~ht of an
7 ultraviolet stabilizer; and (4) less than about 0.5~/0 by weight
8 of an anti-oxidant stabilizer which permits cross-linking by
9 irradiation.
4. Detailed Description of the Invention
11 LP-LD Hydrocarbon Interpolymer
12 Suitable LP-LD hydrocarbon interpolymers for the tube
13 forming compositions of the present invention include copolymers
14 of ethyLene or butene-l and one or more C3 to C10 alpha olefins.
These copolymers have a density of ~ 0.910 to ~ 0.940 grams/cm3
16 and preferably of about, ~ 0.915 to ~ 0.928 grams/cm3. These
17 copolymers can be made in a solution, slurry or gas phase process
18 well known to those skilled in the art.
19 The LP-LD hydrocarbon interpolymers used for the
compositions of this invention should have a standard melt index
21 from about 0.1 t~ about 10 decigrams per minute and preferably
22 from abo~t 0.3 to about 1.2 decigrams per minute. `
23 The extrudable LP-LD hydrocarbon interpolymers employed
24 in the extrudable composltions of the present invention are
normally solid materials, that is, solid at room temperature.
26 Any extrusion grade LP-LD hydrocarbon interpolymer can be used
27 in the compositions of the present invention. T~e term LF-LD
28 hydrocarbon interpolymer thus includes interpolymers of one or
29 more olefin(s) with each other, and/or up to about 30 weight
pe ent of one or more monomer(s) which ~a copolymerizable wlth
3L~ 3~ 12637-C
such olefin(s). The olefins include those such as ethylene, pro-
pylene, butene-l, isobutylene, pentene-l, 4-methyl-pentene-1, hexene-l,
octene-l, nonene-l, decene-l, undecene-l, dodecene-l, tridecene-l,
tetradecene-l, pentadecene-l, hexadecene-l, heptadecene-l, octa-
decene-l, nonadecene-l, and eicosene. Interpolymers include one or
more of such olefins and one or more other monomers which are inter-
polymerizable with such olefins, such as other vinyl and diene
ccmpounds, i.e., those having the group -C=C-.
Preferred copolymers are the ethylene copolymers such as
ethylene/propylene copolymers, ethylene/butene-l copolymers, ethylene/
isobutylene copolymers, ethylene/pentene-l copolymers, ethylene/
4-methyl-pentene-1 copolymers, ethylene/hexene-l copolymers,
ethylene/octene-l copolymers, and the like. Preferred ethylene
interpolymers would include two or more of the followin~: propylene,
butene-l, isobutylene, pentene-l, hexene-l, 4-methyl-pentene-1 and
octene-l. Preferred butene-l interpolymers would include ethylene,
propylene, hexene-l, 4-methyl-pentene-1 and octene-l as comonomers.
Preferred low pressure, low density ethylene copolymers
for use in the present invention include those which may be produced
in accordance with the procedures set forth in U.S. Patent 4,302,566
in the names of F.J. Karol et al and entitled "Preparation of
Ethylene Copolymers in Fluid Bed Reactor", and the procedures set
forth in U.S. Patent 4,302,565 in the names of G.L. Goeke et al
and entitled "Impregnated Polymerization Catalyst, Process for
Preparing, and Use for Ethylene Copolymerization" as well as
57~;~
12637-C
procedures which will produce ethylene hydrocarbon copolymers with
properties as heretofore described. U.S. Patent 4,302,566 corres-
ponds to European Patent Application No. 79100953.3 which was
opened to the public on October 17, 1979 as Publication No. 4645
and U.S. Patent 4,302,565 corresponds to European Patent Application
No. 79100958.2 ~hich was opened to the public on October 17, 1979
as Publication No. 4647.
Other low pressure, low density ethylene hydrocarbon polymers
preferred for use in the present invention are those which may be
pr~pared as described in U.S. Patent 4,011,382, entitled "Pre-
paration of Low and Medium Density Ethylene Polymer in Fluid Bed
Reactor" by I.J. Levine et al.
Ethylene Vinyl Ester Copol~er
Suitable for this invention are > 2% and ~ 10% by weight
of copolymers of ethylene with a vinyl ester of a Cl - C30 mono-
carboxylic acid. Other alpha olefins also may be present in such
copolymers in minor concentrations. The ethylene vinyl ester
copolymers have a density between about 0.91 to about 0.94 gr~ms/cm3.
The carboxylic acid is preferably aliphatic, saturated and mono-
carboxylic, e.g., vinyl propionate, vinyl hexoate, vinyl octoate,
vinyl dodecanate, vinyl behenate or isopropyl acetate. The prefer-
red ester is vinyl acetate in a concentration from about 2% to about
35%, preferably between about 23~/o and 35%.
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. I
I'
1 Ultraviolet Stabilizer
2 The tube forming compositions of the present invention ¦
3 contain at least one UV stabilizer. ~hese W stabilizers
4 are present in a wei~ht concentration of from about .01% to
about~ 3~/0. The UV stabilizers are able to absorb ultraviolet
6 light more readlly than the olefin polymer in th-e composition
7 or are able to interact with and deactivate free radicals
8 immediately as they are formed in the composition.
g Suitable W stabilizers according to this invention
include carbon black, derivatives of 2-hydroxy benzophenone, and
11 hydroxyphenylbenzotriazoles. Other W stabilizers which are
12 believed to be suitable for this invention include the ollowing:
13 2-hydroxybenzophenones such as 2,4-dihydrobenzophenone,
14 2-hydroxy-4-methoxybenæophenone, 4-(heptyloxy)-2-hydroxybenzo-
phenone, 2-hydroxy-4-toctyloxy)benzophenone, 2-hydroxy-4-(2-
16 hydroxyethoxy)benzophenone, 4-alkoxy~2-hydroxybenzophenone,
17 2-hydroxy-4-methoxy-5-methylbenzophenone, 5-benzoyl-4-hydroxy-2-
18 methoxybenzene-sulfonic acid, 2-(2-hydroxy~4-methoxybenzoyl)
19 benzoic acid~2~21-dihydroxy-4-methoxybenzophenone~ 4-butoxy-2,2'-
dihydroxybenzophenone, and 2~2'-dihydroxy-4-(octyloxy)benzophenone
21 2-(2H-benzotriazol-2-yl)phenols such as 2-(2H-benzotriazol-2-yl)~
22 p-cresol, 2-tert-butyl-6-(5-chloro-2H-benzotriazol-2-yl)p-cresol,
23 2,4-di-tert-butyl-6-(5-chloro-2H-benzotriazol-2-yl)phenol, and
24 2-(2H-benzotriazol-2-yl)4,6-di-tert-pentylphenol; phenyl esters
such as phenyl salicylate, p-(1,1,3,3-tetramethylbutyl)phenyl
26 salicylate, resorcinol monobenzoate, bis(p-nonyl~henyl)terephtha-
27 late, and bis(p-1,1,3,3-tetramethylbutyl)phenyl ~sophthalate;
28 nickel compounds such as bis[2,2'-thiobis-4-(1,1,3,3-tetramethyl-
29 butyl)phenolato]nickel, and [2,2'-th-iobis[4-(1,1,3,3-tetrame~hyl-
butyl)phenol]ato(2-)~butylamine)nickel.
I ` 12637
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.,
1 Anti-Oxidant Stabilizer
2 The tube forming compositions of the present inveneion
3 also contain at least one anti-oxidant for the olefin polymer.
4 These anti-oxidants are present in stabilizingly effecci~e
quantities. Such amounts are about 0.002 to 0.5, and preerably
6 about 0.05 to 0.12, percent by weight, based on~the weight of
7 the olefin polymer. The anti-oxidant stabilizers which may be
8 employed in the compositions of the present invention include
9 all those polyolefin anti-oxidants commonlv employed in olefin
polymer based tube extrusion compositions. These materials
11 are such as are capable of providing anti-oxidant protection at
12 processing temperatures of the order of about 135C to 343C,
13 or higher.
14 Such anti-oxidant stabilizers include hindered phenols,
such as p-hydroxyphenylcyclohexane; di-p-hydroxyphenylcyclohexane
16 dicresylolpropane; tertiary butyl para cresol; 2,6-di-tert- .
17 butyl-p-cresol; 2,4,6-tri-tert-butylphenol; octadecyl-3-(3,5-
18 di-tert^butyl-4-hydroxyphenyl3propionate; tetra bistmethylene 3-
19 (3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate]methane;
1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)
21 benzene; tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanate;
22 1,3,5-tris(4-tert-butyl-3-hydroxy-2,6 dimethyl benzyl)^l,3,5-
23 triazine-2,4,6-(lH,3H,SHO-trione; and bis-[3,3-bis-4'-hydroxy-3'-
24 tert-butyl-phenyl)butanoic acid]-glycol ester, condensation pro-
ducts of dialkylphenols with formaldehyde, reaction products of
26 phenol with styrene, 1,1'-methylene-bis(4-hydroxy-3,5-tert-butyl-
~7 phenol), 2,2'-methylene-bis-(4-methyl-6-tert-but~lphenol), 2,6-
28 (2-tert-butyl-4-methyl-6-methylphenol)-p-cresol, Phenylethyl-
29 pyrocatechol, phenolisopropylpyrocatechol, 1,1,3-tris(2'-methyl-
5'-t'-butyl-4-hydroxy phenol)butane, 2,2-methylene-bis[6-(~-
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1 methylcyclohexyl)-4-methylphenol], 1,3,5-trimethyl-2,4,6-tris-
2 (3',5'-di-t-butyl-4-hydroxybenzyl]benzene and ~-naphthol; and
3 sulfur containing compounds such as 2,2'-thio-bis(4-methvl-6-
4 tert-butylphenol), 4-4'-thio-bis(3-methyl-6-tert-butylphenyl),
distearyl thiodipropionate and dilauryl thiodipropionate; and
6 quinoline based compounds such as polymerized 1,2-dihydro-2,2,4-
7 trimethylquinoline; 6-ethoxy-1,2-dihydro-2,2,4-trimethylquinoline;
8 and 6-dodecyl-1,2-dihydro-2,2,4-trimethylquinoline.
9 The preferred primary anti-oxidant stabilizers which
are employed in the compositions of the present invention are
11 the three aforeme~ioned quinoline based compounds. They permit
12 cross-linking by irradiation and still operate as thermal
13 stabilizers.
14 The primary quinoline based anti-oxidants may be used
individually or in various combinations with one another.
16 Other Additives
17 In addition to the LP-LD hydrocarbon interpolymer,
18 copolymer of ethylene with a vinyl ester of Cl-C30 monocarboxylic
19 acid, W stabilizer, and primary anti-oxidant(s), the`compositions
of the present invention may contain other adjuvant materials
21 which are commonly employed in olefin polymer-based extrudable
22 tubing compositions. Such other adjuvants would include
23 fillers, pigments, lubricants, modifiers and similar materials.
24 The fillers which may be used in the olefin polymer-
based extrudable compositions of the present invention are the
26 fillers which are commonly used with such polymers. The fillers
27 are used in amounts which correspond to about 1 t~ 20 percent
28 by weight, based on the weight of the olefin polymer. Such
29 fillers would include materials such as titanium dioxide, clays,
diatomaceous earth, calcium silicates and others kno~m in the art.
I ~ 79~ 12637
1 The lubricants which ~re c~mo~ly employed in the
2 olefin polymer based extrudable compositions are the lubricants
3 which are cor~nonly used with such polymers. The lubricants are
4 used in amounts which correspond to about 0.02 to 0.3% by
S weight of lubricant a8ent based on the weight o~ the olefin
polymer. Example of such lubricants: fatty acid amides such
7 as stearamide, oleamide, behenamide and luramide. Other
8 lubricants include calcium, zinc, titanium, and other Grou~ I
9 or II metal stearates.
Preparation of Extrudable Compositions
11 The extrudable compositions can be prepared by several
12 methods which are well known to those skilled in the art. In
13 on~ method, the components are dry blended together in a roll
14 drum for 20 rninutes at room temperature. In another method, the
lS components are compounded u~ilizing a Banbury batch mixer coupled
16 eo a Farrel Birmingham single screw extruder melt pump. The
17 components are mixed in the Banbury mixer for about 4 to 5
18 minutes, dropped at a temperature from about 125C to-about
19 185C and extruded through an extruder melt pump using a throat
temperature of about 140C, a barrel temperature of about 150C
21 and a die temperature of about 175C.
22 - In still another method, the components are compounded
23 using a Banbury batch mixer and melt fed into a single screw
24 extruder and under water pelletized. The componen~s are mixed in
2~ the Banbury mixer for about 1.5 to 5 minutes, usually using three
26 cycles, two working cycles separated by a short non-working cycle
27 in ~hich the resin is turned over. It is then dropped at a
28 temperature from about 150C to about 190C and extruded ~hrough
29 the extruder using a barrel temperature of about 180C. The end
of the extruder has a Tnany holed die plate where a rapidly
!l i,
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1 rotating blade cuts off the extrudate going through the die
2 plate to form pellets. These pellets are then used in the
3 extrusion of the tubing,
4 The process used for forming drip irrigation tubing fro
S the above composition consists basically of a standard extruder
6 whose length may be from a 16 to 1 length diameter (L/D) ratio
7 to a 32 to 1 L/D ratio and any diameter required (i.e., 1",
8 2 1/2", 3 1/2", etc.) depending on output rate desired as is well
9 known in the industry. The extruder must be equipped with some
form of an Archemeadian screw whe~her a standard conventional type
11 or a barrier type such as the ~addock mixing screw. The
12 Maddock mixing screw is the ~referred screw, however. The
13 extruder should be capable of infinite temperature settings'
14 from 125C to 280C and equipped with barrel coolin~ capabilities.
The polymer is fed into the extruder in pellet form and
16 is melted by the hot barrel and shear (i.e,, mechanical
17 dissipation from the screw in the form of heat) in order to
18 melt the polymer and deliver it in its molten stage to the die.
19 Profile Extrusion of Tubing
In a process for forming drip irrigation tubing, a
21 polymer tubing forming composition is melted and then extruded
22 through an annular die. The die has a die gap greater than about
23 0.25 mm and less than about 5.0 mm, and preferably greater than
24 about 0,30 mm and less than 1.90 mm. The polymer tubing forming
composition is extruded at a melt temperature between about
26 150C and about 240C. Extrusion takes place in a horizontal
27 or downward direction in an annular form. The annular extrudate
28 is usually drawn down to desired dimensions, then cooled in a
29 vacuum sizing tank which has water inside of it. The annular
extrudate typically is drawn do~ to desired dimensions
119579Z 12637
l ¦ via a vacuum sizing method which is a conventional technique,
2 ¦ well known in the art. This technique uses a vacuum sizin~
3 ¦ sleeve to size the tubing. This sleeve is in a water bath which
4 ¦ serves to quench and solidify the tubing in its proper shape.
5 ¦ The ubing is then pulled at a constant rate through a multi-
6 contact puller and then wound up on a roll for irradiation.
7 The multi-contact puller provides the necessary tension to give
8 the wall thickness desired. This is also well known in the
9 ~rt.
The inside of the tubing is usually left exposed to
ll atmospheric air pressure while ~he outside of the wall of the
12 tubing has a negative pressure from the vacuum sizing method
13 such that the tubing is pulled up against the vacuum sizing
14 sleeve from which it is given its final size. Dra~down ratios
on the outside diameter, a ratio defined as the inside diameter
16 of the bushing divided by the outside diameter of the final
17 ~ubing, should be less than 2 to l. The wall thickness drawdown
18 ratio, as defined by the gap in the die divided by tXe ~hinnest
l9 uall of the final tubing, should be less than 2.5 to l for
quality tubing. In certain cases, the tubing may be perforated,
21 e.g., via exposure ~o laser beam, and then irradiated to cross-
22 link the polymer tubing.
23 Physical Properties of the Drip Irrigation Tubin~ ¦
24 As hereinbefore noted, the physical properties ~hich
are particularly significant for the successful use of thermoset
26 drip irrigation tubing include its stress crack resis~ance and
27 burst properties, especially at eleva~ed temperatures. With
28 respect to the latter, the burst properties at 80C are
29 particularly important. A tubing which possesses excellent
environmental stress crack resistance (ESCR) and burs~ properties
~195~9~ 12637
l at ambient and 80C in general will be very satisfactory for
2 drip irrigation tubing applications worldwide.
3 The drip irrigation tubing of this invention have been
4 found to possess excellent ESCR and improved burst properties
at 80~. The ESCR ensures that the tubing does not fail in the
6 field due to insert fittings or when subjec~ed to other mechanical
7 stresses such as a V-pinch in the tubing. A mathod commonly
8 practiced in the art to fasten tubing together is to insert the
9 tubing over a barbed fitting.
Drip irrigation is laid on top of the ground, usually
ll in arid or semi-arid areas, where, in the summertime, the
12 temperature of the tubing will get to rather high temperatures,
13 up to about 80C. Since the inside of the tubing is still under
l4 pressure, the tubing must possess pressure capabilities at
80C. Internal pressures are caused by water in the tube being
16 metered out at an individual plant. Usually, drip irrigation
17 tubing comes in a dual chambered tube having a main chamber and
18 a small chamber. The main chamber portion of the tubing will
19 hold the pressure. Only a few holes are drilled into the main
chamber portion of the tubing so that the pressure therein is not
21 substantially reduced. Pressure in the small chamber is used
22 to meter water to the plant.
23 The drip irrigation tubing should have a very good
24 burst strength or burst stress. This is measured as a hoop
2~ stress, which is the actual stress in the tubing wall, defined
26 as the pressure times the quantity of the outside diameter of
27 the tubing minus the wall thickness which is then divided by two
28 times the wall thickness. Drip irrigation tubing formulations
29 which exhibit longer failure times at certain hoop stresses are
generally recognized as better materials for this particular
I ~ 2
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l application at a particular temperature. Since drip irrigation
2 tublng is exposed to elevated temperatures only during the
3 extremely hot portion of a day (which is a fraction of the day or
4 a fraction of the number of hours that it is in ~ervice), improved
burst properties of tubing at 80C for even a few hours translates
6 into a few days' more use. For drip irrigation tubing of this
7 invention, burst strength properties have been obtained when the
8 tubing did not fail after about 500 hours at 400 psi hoop stress
9 at 80C. Tubing that has failure times at 400 psi hoop stress
at 80C of more than 500 hours is generally regarded as superior
ll tubing. The drip irrigation ~ubing of this invention not only
12 achieves the aforementioned minimum requirements of burst strength
13 properties, but in fact far exceeds those minimum requirements.
14 Cross-Linking of the Extruded Tubin~
Cross-linkin~ of the extruded tubing can be effected
16 by a wide variety of methods and includes, but is not limited
17 to, ionizing and nonionizing radiation, rind chemical cross-
18 linking through covalent, ionic and other types of bonds.
l9 One method of chemical cross-linking involves
contacting the extruded tubing with a cross-linking agent
21 ¦1 in the presence of a free radical catalyst. Illustrative
22 !I cross-linking agents disclosed include compounds such as 1,4-
23 butylene glycol diacrylate, tetraethylene glycol diacryla~e,
2~ polyethylene glycol diacrylate, me~hylene bisacrylamide and the
like. Typical free radical catalysts disclosed are azobisiso-
26 butyronitrile, benzoyl peroxide, 2,4-dichloroben~oyl peroxide, and
27 the like. ln addition to chemlcal cross-linking by means of a
28 free-radical catalyst, other methods can be employed. These
29 ¦ ~ethods are well known to those skilled in the art and include
3~ ' the use of peroxide catalysts.
~ -14-
11~5~9Z 12637
l In addition to the aforementioned methods of effecting
2 cross-linking of the tubing, another method is to subject the
3 polymer tubing to sufficien~ ionizing radiation to cross-link
4 it. As used herein, the term "ioni~ing radiation" includes that
radiation which has sufficient energy to cause electronic excita-
6 tion ant/or ionization in the polymer molecules but which does
7 not have sufficient energy to affect the nuclei of the constituent
8 atoms. Convenient sources of suitable ionizing radiation are
9 gamma-ray producing radioactive isotopes such as Co60 and csl37
spent nuclear uel elements, X-rays such as those produced by
ll conventional X-ray machines, and electrons produced by such means
12 as Van de Graaff accelerators, linear electron accelerators,
13 resonant transformers, and the like. Suitable ionizing radiation
14 for use in the present invention will generally have an energy
level in the range of from about 0.05 ~1eV to about 20 MeV.
16 The irradiation.of.the non-cross-linked polymers can be
17 carried out in the air, in a vacuum, or under various gaseous
l8 atmospheres. Any conventional method can be used to bring the
19 polymer into contact with the ionizing radiation. Suitable
methods are well known and understood by those skilled in the art.
21 The following examples are illustrative of the present
22 invention and are not intended as`a limitation of the scope
23 thereof.
24 Example l
Preparation of Polymer Resin
26 A low pressure, low density ethylene-butene-l copolymer
27 was prepared according to the procedure disclosed in South
28 African Patent Publication No. 79-01365, published September 22,
29 1980, entitled "Process for Makin~ :Film from Low Density Ethylene
Hydrocarbon Copolymer" by W.A. Fraser et al. The properties of
i¦ !
Si75aZ -
12637
1 the ethylene-butene-l copolymer were determined by the following
2 methods:
3 Density was determined according to ASTM D-1505. A
4 slo~ cooled (at 15C/min) plaque was prepared by using ASTM
D-192~, Condition C. Density is reported as gmsl cm3 .
6 Melt Index (MI) was determined according to ASTM
7 D-1238, Condition E. It was measured at 190C and 303kPa and
8 reported as grams/10 minutes.
9 Flow Index (HLMI) was measured according to ASTM
D-1238, Condition F. It was measured at 3030kPa and reported as
11 grams per 10 minutes.
12 Melt Flow Ratio (MFR) was calculated as Flow Index/
13 Melt Index.
14 Secant Modulus was determined according to ASTM D-882.
Stress crack resistance was measured according to the
16 following procedure: Tubîng samples were aged four weeks at
1? 70C and then inserted on barb fittings at 15% strain and put in
18 a 10% by volume nonylphenoxy poly(ethyleneoxy)ethanol aqueous
19 solution at 50C.
Yield strength percent elongation and ~ensile strength
21 I at break was measured on compression molded plaques made in
22 accordance with ASTM D-1928, Condition C. The properties were
23 tested according to ASTM D-638.
24 Long term burst properties were tested according to
ASTM D-1598.
26 Short term burst properties (instant burst) were
2t ~easured according to ASTM D-1599.
28 Test for % crosslinking after irradiation consists of
29 immersing the cross-linked polymer in boiling decalin for six hou~s
and then measuring the amount extracted. The amoun~ left is
-16-
~ 5~2
12637
1 deemed to be the cross-linked fraction.
2 1 The ethylene-butene-l copolymer had the followin
3 properties: a melt index of 0.55, a MFR of 65 and a compound
4 density of 0.920.
S An ethylene vinyl ace~ate copolymer was used. The
6 .copolymer had a vinyl acetate content of 28% and a melt index
7 of 375. Also used was carbon black and an anti-oxidant,
8 polymerized 1,2-dihydro-2,2,4-trimethylquinoline.
9 Pre~aration of Extrudable Compositions
The following compositions were compounded utilizing a
11 Banbury mixer which dropped as a molten mass into an extrusion
12 hopper for feedi.ng in~o an extruder as previously described.
13 Three extrudable compositions were prepared, and physical
14 properties of such compositions are set forth in Table I below:
TABI.E I
...
16 Composition
17 A B C
18 LPLDPE (wt%) 87.4 82.4 ~92.4
19 EVA (wt%) 5.0 10.0
Carbon Black Masterbatch* (wt%) 7.5 7.5 7.5
21 ¦ Polymerized 1,2-dihydro-2,2,4-
22 ¦ trimethyl~uinoline 0.1 0.1 0.1
23 Melt Index (decigrams per 10
24 ¦ minutes) 0.52 0.62 0.4
25 1 _
26 1 ;':Masterbatch consisted of the following compositi~n: 65% tubular
l reactor HPLDPE having a 0.2 melt index and a density of 0.921,
28 and 35% of carbon blac~ having a maximum particle size of 45 ~m.
29
119S792
12637
1 TABLE_I (con~'d)
2 I Com~osition
3 , A B C
4 ¦1 ~ensity (gm/cm3) 0.9388 0.9378 0.938~ ;
5 '~ ~ensilè Strength (psi x 10 3) 2.96 2 73 2.76
6 I Yield Strength (psi x 10 3) 1.59 1.42 1.69
7 Elongation at Break (%) 858 808 726
8 Secent Modulus (psi x 10 4) 3.28 2.9 4.35
g The extrudable compositions A-C were extruded uslng a
@r~file extrusion process described herein as follows:
11 The pellet product made was fed into the hopper of a
12 (NRM) 2 1/2" 16 to 1 L/D ex~ruder equipped with a l~addock mixing
13 screw, barrel cool;ng and infinite ~emperature control settings
14 from 125C to > 300C. This extruder had three barrel zones whose
lS temperatures were 193, 199 and 204~C respectively, one zone for thl ,
~6' extruder head at 204C and one zone for the die at 204C. The ex-
17 truder screw was rotated at 45 RPM resulting in output rates of
18 about 32 kg/hr. The molten polymer was then directly fed to a
19 straight through spider tape die in order to form the annular ex-
trudate. The inside diameter of the die was about 31 mm while the
21 pin outside diameter was about 25 mm in diameter. The resulting
22 extrudate was then drawn down to about 17 mm outside diameter and
23 about 1.5 mm in wall thickness using a vacuum sizing method. The
24 vacuum sizing tank was equipped with a brass sizing sleeve about 5
tubing diameters long. It was slotted in order to allow the nega-
26 tive pressure caused by the vacuum to pull the extrudate against
27 the sleeve. The cold water freezes the extrudate to this diameter
28 The vacuum sizing tank used between 2 and 6" of Hg as the vacuum.
29 The tank was 6' long. A multi-contact puller was used to pull
the extrudate at a constant rate and thus yielding a constant wall
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d 1l95792 12637
1 ¦¦ thickness. The tubing was tested after at least two days delay.
2 ~ The three compositions shown in Table I were extruded
3 11 as described above into tubing, pressure tested both before and
4 11 after irradiation at 10 M.rads. and tested for stress crack
5 1I resistance and short and long term burst strength. The results
6 ¦¦ are summarized in Ta~le II below:
8 ~! T_BLE II
9 ¦¦ ~ Fro ComDosition
10 ¦~ Instant Burse Before Irradiation 1575 1550 1795
12 D InsCant 8urst Aiter Irradiati~n 1800 1715 1830
14 ¦¦ Long-Term Pressure Test at 80C
15 ¦¦ (hrs)
16 ~at 400 psi before Irr. 216 124 125
17 ¦¦at 400 psi after Irr. ~3612 ~ 128 2826
1~ ¦at 320 psi before Irr. > 3208 ~1840 4760
L9 ¦at 320 psi after Irr. > 8008 > 5483 6696
'0 ¦ Crosslinking After Irradiation57 56 48
11 . I
2 Tubing ESCR (hours) (no 1000 lOoo 1000
I observable failures) at
3 1 15% strain in 10% by volume
nonylphenoxy poly(ethyleneoxy)
ethanol aqueoug solution at ~ r
-19-
li
7~2
1 TABI.E III
2 Equipment: NRM 2 1/2" 16 to 1 L/D Extruder Tube
3 Formin~ Composition
4 A B C
Zone 1 ~C) 193 193 193
6 2 (C) lg9 199 199
7 3 ~C) ~04 ~04 204
8 Hea~ (C) 204 204 204
9 Die (C) 204 204 204
Stock temperature (C~ 200 195 200
11 Amperes 11.0 10.6 10.6
12 RPM 45 45 45
13 Head Pressure (psi) 1000 975 1100
Ra~ kgs/hr) 32.6 32.3 32.6
28
29
