U.S. patent application number 13/515826 was filed with the patent office on 2013-02-07 for method for preparing polyethylene with high melt strength.
This patent application is currently assigned to DOW BRASIL S.A.. The applicant listed for this patent is Jorge Caminero Gomes, Nicolas Cardoso Mazzola, Maria Pollard, Michael D. Turner. Invention is credited to Jorge Caminero Gomes, Nicolas Cardoso Mazzola, Maria Pollard, Michael D. Turner.
Application Number | 20130035438 13/515826 |
Document ID | / |
Family ID | 43734837 |
Filed Date | 2013-02-07 |
United States Patent
Application |
20130035438 |
Kind Code |
A1 |
Pollard; Maria ; et
al. |
February 7, 2013 |
METHOD FOR PREPARING POLYETHYLENE WITH HIGH MELT STRENGTH
Abstract
The present invention is an ethylene-based polymer comprising
reacting a polyethylene resin with an alkoxy amine derivative
corresponding to the formula: (R.sub.1)(R.sub.2)N--O--R.sub.3 where
R.sub.1 and R.sub.2 are each independently of one another,
hydrogen, C.sub.4-C.sub.42 alkyl or C.sub.4-C.sub.42 aryl or
substituted hydrocarbon groups comprising O and/or N, and where
R.sub.1 and R.sub.2 may form a ring structure together; and where
R.sub.3 is hydrogen, a hydrocarbon or a substituted hydrocarbon
group comprising O and/or N. Preferred groups for R.sub.3 include
--C.sub.1-C.sub.19alkyl; --C.sub.6-C.sub.10aryl;
--C.sub.2-C.sub.19akenyl; --O--C.sub.1-C.sub.19alkyl;
--O--C.sub.6-C.sub.10aryl; --NH--C.sub.1-C.sub.19alkyl;
--NH--C.sub.6-C.sub.10aryl; --N--(C.sub.1-C.sub.19alkyl).sub.2.
R.sub.3 most preferably contains an acyl group. The resulting resin
has increased melt strength with higher ratio of elongational
viscosities at 0.1 to 100 rad/s when compared to substantially
similar polyethylene resins which have not been reacted with an
alkoxy amine derivative.
Inventors: |
Pollard; Maria; (Pearland,
TX) ; Turner; Michael D.; (Sugar Land, TX) ;
Mazzola; Nicolas Cardoso; (Jundiai, BR) ; Gomes;
Jorge Caminero; (Sao Paulo, BR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Pollard; Maria
Turner; Michael D.
Mazzola; Nicolas Cardoso
Gomes; Jorge Caminero |
Pearland
Sugar Land
Jundiai
Sao Paulo |
TX
TX |
US
US
BR
BR |
|
|
Assignee: |
DOW BRASIL S.A.
Sao Paulo - Sp
MI
DOW GLOBAL TECHNOLOGIES LLC
Midland
|
Family ID: |
43734837 |
Appl. No.: |
13/515826 |
Filed: |
January 11, 2011 |
PCT Filed: |
January 11, 2011 |
PCT NO: |
PCT/US11/20839 |
371 Date: |
June 14, 2012 |
Current U.S.
Class: |
524/585 ;
525/194; 525/375 |
Current CPC
Class: |
C08F 110/02 20130101;
C08L 2205/025 20130101; C08F 110/02 20130101; C08J 2323/36
20130101; C08F 8/30 20130101; C08J 5/18 20130101; C08L 23/36
20130101; C08L 2666/04 20130101; C08F 2500/17 20130101; C08L
23/0815 20130101; C08F 110/02 20130101; C08F 2500/11 20130101; C08L
2023/44 20130101; C08F 2500/03 20130101; C08F 2500/12 20130101;
C08K 5/3435 20130101; C08F 8/30 20130101; C08L 23/0815 20130101;
Y10T 428/139 20150115 |
Class at
Publication: |
524/585 ;
525/375; 525/194 |
International
Class: |
C08F 8/32 20060101
C08F008/32; C08L 23/06 20060101 C08L023/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 11, 2010 |
US |
12685148 |
Claims
1. A method for increasing the melt strength of a target
polyethylene resin comprising the steps of: a) selecting a target
polyethylene resin having a density, as determined according to
ASTM D792, in the range of from 0.865 g/cm.sup.3 to 0.970
g/cm.sup.3, and a melt index, as determined according to ASTM D1238
(2.16 kg, 190.degree. C.), in the range of from 0.01 g/10 min to
100 g/10 min; b) reacting an alkoxy amine derivative in an amount
less than 900 parts derivative per million parts of total
polyethylene resin with the polyethylene resin under conditions
sufficient to increase the melt strength of the polyethylene
resin
2. method of claim 1 wherein the alkoxy amine derivative
corresponds to the formula: (R.sub.1)(R.sub.2)N--O--R.sub.3 where
R.sub.1 and R.sub.2 are each independently of one another,
hydrogen, C.sub.4-C.sub.42 alkyl or C.sub.4-C.sub.42 aryl or
substituted hydrocarbon groups comprising O and/or N, and where
R.sub.1 and R.sub.2 may form a ring structure together; and R.sub.3
is hydrogen, a hydrocarbon or a substituted hydrocarbon group
comprising O and/or N.
3. The method of claim 1 wherein the alkoxy amine derivative is a
hydroxylamine ester.
4. The method of claim 3 wherein the hydroxylamine ester is
hydroxylamine ester being
9-(acetyloxy)-3,8,10-triethyl-7,8,10-trimethyl-1,5-dioxa-9-azaspiro[5.5]u-
ndec-3-yl]methyl octadecanoate
5. The method of claim 1 wherein the alkoxy amine derivative is
added to the target polyethylene resin as a masterbatch comprising
the alkoxy amine derivative along with a carrier resin.
6. The method of claim 5 wherein the carrier resin is selected from
the group consisting of HDPE, LLDPE, and LDPE.
7. The method of claim 6 wherein the carrier resin is LDPE and the
LDPE resin has a trisubstituted unsaturation unit per-1,000,000
carbon atoms in the range of from 0 to 500.
8. The method of claim 7 wherein the carrier resin has a
trisubstituted unsaturation unit per 1,000,000 carbon atoms of less
than 100.
9. The method of claim 6 wherein the carrier resin is HDPE and the
HDPE resin has a trisubstituted unsaturation unit per 1,000,000
carbon atoms in the range of from 0 to 500.
10. The method of claim 9 wherein the carrier resin has a
trisubstituted unsaturation unit per 1,000,000 carbon atoms less
than 50.
11. The method of claim 6 wherein the carrier resin is
substantially free of antioxidant compounds, in the range of 0 to
1,000 ppm.
12. The method of claim 11 wherein the carrier resin is free of
primary antioxidant compounds.
13. The method of claim 1 wherein the alkoxy amine derivative is
reacted with the polyethylene resin in a reactive extrusion
process.
14. The method of claim 1 wherein the target resin comprises LLDPE
resin derived from ethylene monomer and alpha-olefin comonomers
having three to twelve carbons.
15. The method of claim 1 wherein the target polyethylene resin
comprises LLDPE resin with trisubstituted unsaturation unit per
1,000,000 carbon atoms in the range of from 0 to 500.
16. The method of claim 1 wherein the target resin comprises a two
or more resins selected from the group consisting of LDPE, LLDPE,
and HDPE resins.
17. The method of claim 1 wherein the target polyethylene resin is
substantially free of primary antioxidants, preferably in the range
of 0 to 1,000 ppm.
18. The method of claim 1 wherein the alkoxy amine derivative is
added in an amount of from 0.003% to less than 0.09% of the total
amount of polyethylene polymer by weight.
19. The method of claim 5 wherein the masterbatch is produced by
melt extruding a mixture of the carrier resin and the derivative at
extruder temperatures below 250.degree. C.
20. The method of claim 1 further comprising the step of adding one
or more antioxidants to the target resin after the target resin has
been reacted with the derivative.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority from U.S. patent
application Ser. No. 12/685,148, filed Jan. 11, 2010, the
disclosure of which is incorporated herein by reference for
purposes of U.S. practice.
BACKGROUND AND SUMMARY OF THE INVENTION
[0002] Polyethylene has desirable properties that have helped to
make it the highest volume polymer manufactured. Polyethylene can
be made in different processes in order to give different
properties. Known families of polyethylene include high density
polyethylene (HDPE), linear low density polyethylene (LLDPE), and
low density polyethylene made using high pressure reactors (LDPE).
Within these broad classes many variations exist resulting from
different types of polyolefin process technologies (for example,
solution, slurry or gas phase) or from the use of different
catalysts (for example, Ziegler-Natta or constrained geometry
catalysts). The desired application requires a careful balance of
rheological properties which will lead a person of skill in the art
to select one type of polyethylene over another. In many
applications, such as blow-molding and blown film applications,
melt strength of the polyethylene is a key parameter, frequently
measured as elongational viscosity of the polymer.
[0003] The melt strength is a practical measurement that can
predict material performance when submitted at elongational
deformations. In melt processing good elongational viscosity is
important to maintain stability during processes such as coating,
blow film production, fiber spinning and foamed parts. The melt
strength is related with a number of molecular entanglements on
molten polymers and relaxation times of each molecular structure,
which is basically dependant on overall molecular weight and number
of branches over critical molecular weight.
[0004] Melt strength directly effects several processing parameters
such as bubble stability and therefore thickness variation during
blow film production; parison formation during blow molding
process; sagging during profile extrusion; cells formation during
foaming process; more stable thickness distribution during
sheet/film thermoforming.
[0005] This property can be enhanced by using resins with higher
molecular weight, but such resins will generally require more
robust equipment and more energy use because they tend to generate
higher extrusion pressure during the extrusion process. Therefore,
properties must be balanced to provide an acceptable combination of
physical properties and processability.
[0006] In thick film applications blends of LDPE and LLDPE are used
in order to obtain a balance of processability (extruder amps and
pressure) and film mechanical properties. In this blend the LDPE
component is the processability component whereas the LLDPE is the
mechanical end component. Therefore, the ability to decrease the
LDPE portion of the blend should increase the mechanical properties
of the blend. Through this invention, the ability to increase the
melt strength of the LLDPE component allows the use of a higher
percentage of LLDPE blend, thus increasing the mechanical
properties without sacrificing processability or the creation of
unacceptable levels of insoluble material.
[0007] The present invention is a new process for increasing the
melt strength of polyethylene involving reacting molten
polyethylene with an alkoxyamine derivative through regular
extrusion processing. Accordingly, one aspect of the invention is a
method for increasing the melt strength of a polyethylene resin
comprising first selecting a polyethylene resin having a density,
as determined according to ASTM D792, in the range of from 0.865
g/cm.sup.3 to 0.962 g/cm.sup.3, and a melt index, as determined
according to ASTM D1238 (2.16 kg, 190.degree. C.), in the range of
from 0.01 g/10 min to 100 g/10 min and then reacting an alkoxy
amine derivative with the polyethylene resin in an amount and under
conditions sufficient to increase the melt strength of the
polyethylene resin.
[0008] The present invention is a new process for increasing the
elongational viscosity of polyethylene involving reacting molten
polyethylene with an alkoxyamine derivative through regular
extrusion processing. Accordingly, one aspect of the invention is a
method for increasing the melt strength of a polyethylene resin
comprising first selecting a polyethylene resin having a density,
as determined according to ASTM D792, in the range of from 0.865
g/cm.sup.3 to 0.962 g/cm.sup.3, and a melt index, as determined
according to ASTM D1238 (2.16 kg, 190.degree. C.), in the range of
from 0.01 g/10 min to 100 g/10 min and then reacting an alkoxy
amine derivative with the polyethylene resin in an amount and under
conditions sufficient to increase the elongational viscosity of the
polyethylene resin.
[0009] The present invention is a new process that increases the
elongational viscosity at low (0.1 s.sup.-1) shear rates while
maintaining the viscosity at higher shear rates (>100 s.sup.-1)
such that the ease of processing of the material is maintained at
typical extrusion conditions. One aspect of the invention is that
the extruder pressure does not increase more than 10% of the
comparative resin upon processing the inventive resin at the same
operating conditions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a plot of melt strength versus stretching velocity
with increasing additive concentration.
[0011] FIG. 2 is a plot of viscosity versus shear rate with
increasing additive concentration.
[0012] FIG. 3 is a plot of melt strength at the plateau region
versus melt index (I.sub.2, g/10 min).
[0013] FIG. 4 is a plot of phase angle (.degree.) versus the
complex modulus (G*) measured using a constant temperature of
190.degree. C. at a frequency sweep in a TA Instruments "Advanced
Rheometric Expansion System (ARES)"
[0014] FIG. 5 is a plot of phase angle (.degree.) versus the
complex modulus (G*) measured using a constant temperature of
190.degree. C. at a frequency sweep in a TA Instruments "Advanced
Rheometric Expansion System (ARES)"
DETAILED DESCRIPTION OF THE INVENTION
[0015] In its broadest sense, the present invention is a method for
increasing the melt strength of a polyethylene resin. Polyethylene
resin includes all polymers or polymer blends which are derived at
least 50% by weight from ethylene monomer units. This includes
materials known in the art as high density polyethylene (HDPE),
linear low density polyethylene (LLDPE), and low density
polyethylene made using high pressure reactors (LDPE).
[0016] The target polyethylene resin selected should have a
density, as determined according to ASTM D792, in the range of from
0.865 g/cm.sup.3 to 0.970 g/cm.sup.3, more preferably from 0.905
g/cm.sup.3 to 0.957 g/cm.sup.3 and a melt index, as determined
according to ASTM D1238 (2.16 kg, 190.degree. C.), in the range of
from 0.01 g/10 min to 100 g/10 min, more preferably 0.1 g/10 min to
15 g/10 min. Suitable target polyethylene resins can be produced
with conventional Ziegler Natta or Chromium catalysts but also with
metallocene or single site catalysts. Such resins may have
monomodal or multimodal molecular weight distributions.
[0017] Once the target polyethylene resin is selected, it is
reacted with an alkoxy amine derivative. For purposes of the
present invention "alkoxy amine derivatives" includes nitroxide
derivatives. The alkoxy amine derivative is added in an amount and
under conditions sufficient to increase the melt strength of the
polyethylene resin. The alkoxy amine derivatives correspond to the
formula:
(R.sub.1)(R.sub.2)N--O--R.sub.3
[0018] where R.sub.1 and R.sub.2 are each independently of one
another, hydrogen, C.sub.4-C.sub.42 alkyl or C.sub.4-C.sub.42 aryl
or substituted hydrocarbon groups comprising O and/or N, and where
R.sub.1 and R.sub.2 may form a ring structure together; and where
R.sub.3 is hydrogen, a hydrocarbon or a substituted hydrocarbon
group comprising O and/or N. Preferred groups for R.sub.3 include
--C.sub.1-C.sub.19alkyl; --C.sub.6-C.sub.10aryl;
--C.sub.2-C.sub.19akenyl; --O--C.sub.1-C.sub.19alkyl;
--O--C.sub.6-C.sub.10aryl; --NH--C.sub.1-C.sub.19alkyl;
--NH--C.sub.6-C.sub.10aryl; --N--(C.sub.1-C.sub.19alkyl).sub.2.
R.sub.3 most preferably contains an acyl group.
[0019] The preferred compound may form nitroxylradical
(R.sub.1)(R.sub.2)N--O* or amynilradical (R1)(R2)N* after
decomposition or thermolysis.
[0020] A particularly preferred species of alkoxy amine derivative
is
9-(acetyloxy)-3,8,10-triethyl-7,8,10-trimethyl-1,5-dioxa-9-azaspiro[5.5]u-
ndec-3-yl]methyl octadecanoate which has the following chemical
structure:
##STR00001##
[0021] Examples of some preferred species for use in the present
invention include the following:
##STR00002##
[0022] In general hydroxylamine esters are more preferred with one
particularly favored hydroxylamine ester being
9-(acetyloxy)-3,8,10-triethyl-7,8,10-trimethyl-1,5-dioxa-9-azaspiro[5.5]u-
ndec-3-yl]methyl octadecanoate.
[0023] The alkoxy amine derivatives are added in an amount
sufficient to increase the melt strength and/or increase the
elongational viscosity to the desired level. Preferably, the melt
strength is increased by at least 10%, 20%, 25%, 35% or even 50%
compared to a similar resin which has not been reacted with an
alkoxy amine derivative. In general the alkoxy amine derivatives
are added in an amount of from 1 to 900 ppm of the total amount of
polyethylene polymer by weight (that is from 1 to 900 parts alkoxy
amine derivative per million parts of target resin plus carrier
resin, if any), preferably from 15 to 600 ppm, more preferably from
25 to 400 ppm and still more preferably from 30 to 200 ppm.
[0024] The addition to the polyethylene polymer can be carried out
in all customary mixing machines in which the polymer is melted and
mixed with the additives. Suitable machines are known to those
skilled in the art. They are predominantly mixers, kneaders and
extruders.
[0025] The process is preferably carried out in an extruder by
introducing the additive during processing. Particularly preferred
processing machines are single-screw extruders, contra rotating and
co rotating twin-screw extruders, planetary-gear extruders, ring
extruders or cokneaders. It is also possible to use processing
machines provided with at least one gas removal compartment to
which a vacuum can be applied. Suitable extruders and kneaders are
described, for example, in Handbuch der Kunststoftextrusion, Vol. 1
Grundlagen, Editors F. Hensen, W. Knappe, H. Potente, 1989, pp.
3-7, ISBN.3-446-14339-4 (VoL 2 Extrusionsanlagen 1986, ISBN
3-446-14329-7). For example, the screw length can be 1-60 times the
screw diameter, preferably 35-48 times the screw diameters. The
rotational speed of the screw is preferably 10-600 rotations per
minute (rpm), more preferably 25-300 rpm. It is also possible to
first prepare a concentrated mixture of the additive in a carrier
polyethylene resin, preferably at 1000 to 10000 ppm, and then
introduce this concentrate, or "masterbatch", via an extruder into
a melted polyethylene using a static mixer to blend the two
materials, preferably at 1 to 20 wt % of the concentrate in the
melted resin. The concentrate could be processed in an extruder,
preferably at temperatures from 180 to 220.degree. C. The
temperatures in the static mixer could range from 200 to
250.degree. C., with a residence time in the mixer ranging from 1
to 10 minutes.
[0026] The maximum throughput is dependent on the screw diameter,
the rotational speed and the driving force. The process of the
present invention can also be carried out at a level lower than
maximum throughput by varying the parameters mentioned or employing
weighing machines delivering dosage amounts.
[0027] If a plurality of components is added, these can be premixed
or added individually.
[0028] The polymers need to be subjected to an elevated temperature
for a sufficient period of time, so that the desired changes occur.
The temperature is generally above the softening point of the
polymers. In a preferred embodiment of the process of the present
invention, a temperature range lower than 280.degree. C.,
particularly from about 160.degree. C. to 280.degree. C. is
employed. In a particularly preferred process variant, the
temperature range from about 200.degree. C. to 270.degree. C. is
employed.
[0029] The period of time necessary for reaction can vary as a
function of the temperature, the amount of material to be reacted
and the type of, for example, extruder used. It is usually from
about 10 seconds to 30 minutes, in particular from 20 seconds to 20
minutes.
[0030] The alkoxy amine derivative can advantageously be added to
the mixing device by use of a masterbatch. As will be appreciated
by those of ordinary skill in the art, the carrier resin for the
masterbatch should be chosen to be compatible with the resin to be
modified. LDPE high pressure low density polyethylene polymers
(referred to in the industry as "LDPE") were unexpectedly found to
be the preferred carrier due to the lower reactivity as evidenced
by little variation of the extrusion pressure during masterbatch
production. HDPE may be a better carrier as it will react even less
because it does not have tertiary carbons and very low
trisubstituted unsaturation units per 1,000,000 carbons. Another
advantage of this invention is the discovery that polypropylene is
not a good carrier for this additive, as it tends to degrade at
typical processing temperatures. Another discovery is that the
carrier resin should be substantially free of any antioxidant
additives, preferably having less than 1,000 ppm of antioxidant
additives, as they tend to suppress the activity of the
additive.
[0031] The preferred carrier resin should be compatible with the
application at hand; it should have similar viscosity with the
target polyethylene resin with which it is going to be blended. It
should be preferably an LDPE or HDPE resin with minimal
trisubstituted unsaturation units, preferably fewer than 70 per
1,000,000 carbons. The preferred carrier resin should have a
molecular weight (Mn) that is less than 50,000 so that it is easy
to process, as demonstrated by the pressure drop through the
extruder. The carrier resin could incorporate other additives for
processing aids but it should preferably be substantially free of
antioxidant compounds, preferably containing less than 1,000 ppm of
any antioxidant compound, preferably less than 500 ppm, more
preferably less than 100 ppm by weight.
[0032] The target polyethylene resin could be a copolymer of
ethylene with any alkene monomer containing 3 to 12 carbons.
Preferably, the target polyethylene resin should have a level of
trisubstituted unsaturation units per 1,000,000 carbons ranging
from 200 to 450. It should have a molecular slightly slower than
the carrier resin, as indicated by the melt index (g/10 min).
Preferably, the melt index of the target polyethylene resin should
be higher by 0.2-0.5 units (g/10 min) than the final desired resin.
Preferably, the polyethylene resin should contain minimal or no
antioxidant additives, and any additives should be well-dispersed
in the resin prior to being blended with the carrier resin.
[0033] The amount of the alkoxy amine derivative material in the
carrier resin should be in the range of 0.1 to 30% by weight,
preferably from 0.1 to 5%, and more preferably in the range of 0.2
to 1%. The amount of the masterbatch is added so that the alkoxy
amine derivative is added to the target product in the range of 1
to 900 ppm, preferably from 15 to 600 ppm, more preferably from 25
to 400 ppm and still more preferably from 30 to 200 ppm. It will
readily be understood by one of skill in the art that the amount of
alkoxy amine derivative in the final product will be reduced from
the added amounts as the compound reacts with the target and
carrier polyethylene.
[0034] Preferably, the amount of the alkoxy amine derivative
ingredient should be kept below 1000 ppm to minimize reaction in
the carrier resin, reduce the potential for gels in the final
product, and be substantially reacted out in the final product so
that the final product remains stable with further processing. It
should be understood that after the alkoxy amine derivative has
been allowed to react with the target resin, it may be desirable to
add one or more antioxidant additives, to protect the properties of
the modified target resin. One way to accomplish this is to blend
the resin after reaction with the alkoxy amine derivative with
another resin that is rich in antioxidants.
Testing Methods
Melt Strength
[0035] Melt strength measurements were conducted on a Gottfert
Rheotens 71.97 (Goettfert Inc.; Rock Hill, S.C.), attached to a
Gottfert Rheotester 2000 capillary rheometer. The melted sample
(about 25 to 30 grams) was fed with a Goettfert Rheotester 2000
capillary rheometer, equipped with a flat entrance angle (180
degrees) of length of 30 mm, diameter of 2.0 mm, and an aspect
ratio (length/diameter) of 15. After equilibrating the samples at
190.degree. C. for 10 minutes, the piston was run at a constant
piston speed of 0.265 mm/second. The standard test temperature was
190.degree. C. The sample was drawn uniaxially to a set of
accelerating nips located 100 mm below the die, with an
acceleration of 2.4 mm/s.sup.2. The tensile force was recorded as a
function of the take-up speed of the nip rolls. Melt strength was
reported as the plateau force (cN) before the strand broke. The
following conditions were used in the melt strength measurements:
plunger speed=0.265 mm/second; wheel acceleration=2.4 mm/s.sup.2;
capillary diameter=2.0 mm; capillary length=30 mm; and barrel
diameter=12 mm.
Melt Index
[0036] The melt index is used as an indication of molecular weight.
Melt index was determined using ASTM method D-1238 at 190.degree.
C. using a Tinius-Olsen Extrusion Plastometer Model MP987, with
orifices with capillary dimensions of 0.0825'' diameter and 0.315''
length; a piston of stainless steel with three scribe marks
(4.17'', 4.33'', and 5.25'') above the foot of the piston; weights
of such size that the combined masses of a weight and piston equal
2.16 and 10.00 kg; and a plug gauge for measuring the orifice
capillary. The melt index identified as 12 refers to the
measurement with 2.16 kg weight and the melt index identified as
I10 refers to the measurement using a 10 kg weight.
Density
[0037] Samples for density measurements were prepared according to
ASTM D 4703-10.
Dynamic Mechanical Spectroscopy
[0038] Resins were compression-molded into "3 mm thick.times.1
inch" circular plaques at 350.degree. F. for five minutes, under
1500 psi pressure in air. The sample was then taken out of the
press, and placed on the counter to cool.
[0039] A constant temperature frequency sweep was performed using a
TA Instruments "Advanced Rheometric Expansion System (ARES),"
equipped with 25 mm (diameter) parallel plates, under a nitrogen
purge. The sample was placed on the plate, and allowed to melt for
five minutes at 190.degree. C. The plates were then closed to a gap
of 2 mm, the sample trimmed (extra sample that extends beyond the
circumference of the "25 mm diameter" plate is removed), and then
the test was started. The method had an additional five minute
delay built in, to allow for temperature equilibrium. The
experiments were performed at 190.degree. C. over a frequency range
of 0.1 to 100 rad/s. The strain amplitude was constant at 10%. The
stress response was analyzed in terms of amplitude and phase, from
which the storage modulus (G'), loss modulus (G''), complex modulus
(G*), complex viscosity .eta.*, tan (.delta.) or tan delta,
viscosity at 0.1 rad/s (V0.1), the viscosity at 100 rad/s (V100),
and the Viscosity Ratio (V0.1/V100) were calculated.
Gel Permeation Chromatography
[0040] The Triple Detector Gel Permeation Chromatography (3D-GPC or
TD-GPC) system consists of a Waters (Milford, Mass.) 150.degree. C.
high temperature chromatograph (other suitable high temperatures
GPC instruments include Polymer Laboratories (Shropshire, UK) Model
210 and Model 220 equipped with an on-board differential
refractometer (RI). Additional detectors can include an IR4
infra-red detector from Polymer ChAR (Valencia, Spain), Precision
Detectors (Amherst, Mass.) 2-angle laser light scattering (LS)
detector Model 2040, and a Viscotek (Houston, Tex.) 150R
4-capillary solution viscometer. A GPC with these latter two
independent detectors and at least one of the former detectors is
sometimes referred to as "3D-GPC or TD-GPC" while the term "GPC"
alone generally refers to conventional GPC. Depending on the
sample, either the 15.degree. angle or the 90.degree. angle of the
light scattering detector is used for calculation purposes. Data
collection is performed using Viscotek TriSEC software, Version 3,
and a 4-channel Viscotek Data Manager DM400. The system is also
equipped with an on-line solvent degassing device from Polymer
Laboratories (Shropshire, United Kingdom).
[0041] Suitable high temperature GPC columns can be used such as
four 30 cm long Shodex HT803 13 micron columns or four 30 cm
Polymer Labs columns of 20-micron mixed-pore-size packing (MixA LS,
Polymer Labs). The sample carousel compartment is operated at
140.degree. C. and the column compartment is operated at
150.degree. C. The samples are prepared at a concentration of 0.1
grams of polymer in 50 milliliters of solvent. The chromatographic
solvent and the sample preparation solvent contain 200 ppm of
butylated hydroxytoluene (BHT) in trichloro benzene (TCB). Both
solvents are sparged with nitrogen. The polyethylene samples are
gently stirred at 160.degree. C. for four hours. The injection
volume is 200 microliters. The flow rate through the GPC is set at
1 ml/minute.
[0042] The GPC column set is calibrated by running 21 narrow
molecular weight distribution polystyrene standards. The molecular
weight (MW) of the standards ranges from 580 to 8,400,000, and the
standards are contained in 6 "cocktail" mixtures. Each standard
mixture has at least a decade of separation between individual
molecular weights. The standard mixtures are purchased from Polymer
Laboratories. The polystyrene standards are prepared at 0.025 g in
50 mL of solvent for molecular weights equal to or greater than
1,000,000 and 0.05 g in 50 mL of solvent for molecular weights less
than 1,000,000. The polystyrene standards were dissolved at
80.degree. C. with gentle agitation for 30 minutes. The narrow
standard mixtures are run first and in order of decreasing amount
of the highest molecular weight component to minimize
degradation.
[0043] The polystyrene standard peak molecular weights were
converted to polyethylene molecular weights using the following
equation (as described in Williams and Ward, J. Polym. Sci., Polym.
Let., 6, 621 (1968)):
Mpolyethylene=A(Mpolystyrene)B (1)
[0044] Here B has a value of 1.0, and the experimentally determined
value of A is 0.38.
[0045] A first order polynomial was used to fit the respective
polyethylene-equivalent calibration points obtained from equation
(1) to their observed elution volumes. The actual polynomial fit
was obtained so as to relate the logarithm of polyethylene
equivalent molecular weights to the observed elution volumes (and
associated powers) for each polystyrene standard.
[0046] Number, weight, and z-average molecular weights were
calculated according to the following equations:
Mn _ = i Wf i i ( Wf i M i ) ( 2 ) Mw _ = i ( Wf i * M i ) i Wf i (
3 ) Mz _ = i ( Wf i * M i 2 ) i ( Wf i * M i ) ( 4 )
##EQU00001##
[0047] Where, Wfi is the weight fraction of the i-th component and
Mi is the molecular weight of the i-th component.
[0048] The MWD was expressed as the ratio of the weight average
molecular weight (Mw) to the number average molecular weight
(Mn).
[0049] The A value was determined by adjusting A value in equation
(1) until Mw, the weight average molecular weight calculated using
equation (3) and the corresponding retention volume polynomial,
agreed with the independently determined value of Mw obtained in
accordance with the linear homopolymer reference with known weight
average molecular weight of 115,000 g/mol.
Trisubstituted Unsaturation Group Determination Method (FTIR)
[0050] Pellets are pressed first to make a thick film of 0.25 mm
and then pressed again to make a thin film of 0.125 mm. The film is
then secured on a scan card and then sanded on both sides before
being loaded on a Nicolet 6700 FTIR instrument. The area under the
peak at 909 cm.sup.-1 is integrated to obtain the value of number
of trisubstituted unsaturation units per 1,000,000 carbons using 64
scans with resolution of 2 cm.sup.-1. This technique has been
calibrated using a known absorbance and concentration and corrects
for film thickness in order to determine the concentration of the
sample.
[0051] Using the above measurements, the ratio of the elongational
viscosities at 0.1 to 100 shear rates (s.sup.-1) provides an
indication of branching in the polymer and an indication of the
effect of the additive. In this invention, resins with the additive
showed a 10 to 60% increase in the viscosity ratio, preferably an
increase of 20 to 40% when compared with the same resin with no
additive.
[0052] Resins modified with the additive show a decrease in I.sub.2
of 5% to 25% and a decrease in I.sub.10 of 4 to 20%. Therefore, the
ratio of I.sub.10 to I.sub.2 for the resins increases with
increasing amount of additive, indicating extent of change in the
polymer.
[0053] Resins modified according to the methods of the present
invention will exhibit an increase in melt strength of at least
10%, preferably in the range of from 20 to 50% as compared to the
same resin which has not been reacted with the alkoxy amine
derivative. Similar performance improvement will also be seen with
respect to elongational viscosity. For the inventive resins,
improvement in melt strength and viscosity performance is better
than anticipated with the changes observed in the melt index
measurements.
[0054] With the increase in melt strength and/or elongational
viscosity, resins made according to the present invention are
particularly well suited for fabricated articles such as films,
sheets, pipes or blow molded articles.
[0055] Films made using the additive and processing conditions in
this invention retain the mechanical properties of the polyethylene
resins that were the base resins without the addition of the alkoxy
amine derivative.
EXAMPLES
[0056] The four examples (two resins with two different amounts of
additive each) described below have a similar molecular weight,
with different concentrations of an alkoxy amine derivative
additive. The specific additive used is
9-(acetyloxy)-3,8,10-triethyl-7,8,10-trimethyl-1,5-dioxa-9-azaspiro[5.5]u-
ndec-3-yl]methyl octadecanoate, which is added as an LDPE
masterbatch having less than 1% of the additive (Note that the ppm
levels reported below refer to the amount of alkoxy amine
derivative added and not the amount of the entire masterbatch
added).
[0057] The masterbatch is prepared as follows: The alkoxy amine
derivative additive is compounded with a homopolymer ethylene resin
made in a high-pressure tubular reactor (that is, an LDPE resin)
having a melt index of 0.7 g/10 min (at 190.degree. C., 2.16 kg
ASTM D-1238) and a density of 0.925 g/cm.sup.3 (ASTM D792). This
LDPE resin is the same as Resin D described below and the additive
concentration in the LDPE resin is at 5,600 parts per million
weight to create a masterbatch.
[0058] The LDPE and derivative are compounded in a 30 mm
co-rotating, intermeshing Coperion Werner-Pfleiderer ZSK-30
(ZSK-30) twin screw extruder to form a masterbatch. The ZSK-30 has
ten barrel sections with an overall length of 960 mm and a 32
length to diameter ratio (L/D). A two hole strand die is used
without a breaker plate or screen pack. The extruder consist of a
DC motor, connected to a gear box by V-belts. The 15 HP motor is
powered by a GE adjustable speed drive located in a control
cabinet. The control range of the screw shaft speed is 1:10. The
maximum screw shaft speed is 500 RPM. A pressure transducer is
positioned in front of the die to measure die pressure.
[0059] The extruder has 8 heated/cooled barrel sections along with
a 30 mm spacer, which makes up five temperature controlled zones.
It has a cooled only feed section and a heated only die section,
which is held together by tie-rods and supported on the machine
frame. Each section can be heated electrically with angular
half-shell heaters and cooled by a special system of cooling
channels.
[0060] The screws consist of continuous shafts on which
screw-flighted components and special kneading elements are
installed in any required order. The elements are held together
radially by keys and keyways and axially by a screwed-in screw tip.
The screw shafts are connected to the gear-shafts by couplings and
can easily be pulled out of the screw barrel for dismantling.
[0061] A Conair pelletizer is used to pelletize the blends. It is a
220 volt variable speed, solid cutter unit. The variable speed
motor drives a solid machined cutting wheel, which in turn drives a
fixed metal roller. A movable rubber roller presses against the
fixed roller and helps pull the strands by friction into the
cutting wheel. The tension on the movable roller may be adjusted as
necessary.
[0062] The temperatures are set in the feed zone, 4 zones in the
extruder, and the die as: [0063] Feed: 80.degree. C. [0064] Zone 1:
160.degree. C. [0065] Zone 2: 180.degree. C. [0066] Zone 3:
185.degree. C. [0067] Zone 4: 190.degree. C. [0068] Die:
210.degree. C. The screw shaft speed is set at 276 revolutions per
minute (RPM), resulting in an output rate of approximately 52
lb/hr.
[0069] The masterbatch defined above is dry-blended with additional
amounts of the LDPE resin D in order to bring the concentration of
the alkoxyamine derivative to a desired level such that when added
in an amount of 3% by weight compared to the target polyethylene,
the additive will be added in the amounts shown in the Table. The
masterbatch or the dry-blended material thereof is blended with
LLDPE resins B or C using the following setup: the masterbatch or
the dry-blended material is fed through a hopper into a Sterling
21/2 inch single screw extruder which is used as the side arm
conveyer with a rupture disc of 3200 psig. The four heating zones
in the single screw extruder are set at 220.degree. C.
[0070] The LLDPE resins B or C are fed through another hopper into
a Century-ZSK-40 extruder (37.13 length-to-diameter ratio extruder,
a co-rotating, intermeshing, 40 mm twin screw extruder with 150 Hp
drive, 244 Armature amps (maximum), and 1200 screw rpm (maximum)).
The nine heating zones in the extruder are set as follows: the
first at 25.degree. C., the second at 100.degree. C., and the rest
at 200.degree. C.
[0071] The polymer melt pump is a Maag 100 cc/revolution pump that
helps convey the molten polymer from the extruder, and through the
downstream equipment. It is powered by a 15 hp motor with a 20.55/1
reduction gear. The pump is equipped with a pressure transmitter
and a 5200 psi rupture disc on the inlet and outlet transition
piece. There are heater zones on the melt pump and the inlet and
outlet transition pieces which are set at 220.degree. C.
[0072] The melt pump is attached to the extruder and the single
screw extruder's flow enters the polymer stream through an injector
from the single screw side arm extruder. The injector is a 3/4 of
an inch tubing protruding into the centerline of a pipe with 3.1
inch internal diameter.
[0073] The polymer coming from the extruder is blended with the
single screw extruder resin as it flows through a static mixer with
18 Kenics mixing element mixer of 3.1 inch internal diameter. The
mixing elements have 1.3 length-to-diameter ratio. There are seven
heating zones in the static mixer and are all set to 220.degree.
C.
[0074] The combined flow then flows through a Gala pelletizer
system. The Gala is equipped with a 12 hole (2.36 mm hole diameter)
Gala die with 4 of the holes plugged. The cutter has a 4 blade hub
and operates at approximately 800 ppm. The water temperature in the
pelletizer is kept at 30.degree. C.
[0075] The amount of the masterbatch or dry-blended masterbatch and
resin D is approximately 3 wt % of the total resin amount. The
residence time of the masterbatch in the side arm extruder is
approximately 20 minutes and the residence time of the polymer in
the static mixer is approximately 3 minutes.
[0076] The melt strength of each of these examples is measured
using Gottfert Rheotester 2000 at 190.degree. C. The viscosity is
measured using a constant temperature of 190.degree. C. at a
frequency sweep in a TA Instruments "Advanced Rheometric Expansion
System (ARES)". The melt indices are measured using ASTM method
D-1238 at 190.degree. C. using a Tinius-Olsen Extrusion Plastometer
Model MP987. The molecular weights are determined using the method
described under Testing Methods above.
[0077] FIG. 1 shows the melt strength curve versus stretching
velocity with increasing additive concentration. The incorporation
of the additive changes the behavior of resins B and C, increasing
the force needed to stretch the molten polymer. The melt strength
of resin B with 60 ppm additive is approximately the same as
comparative resin E with the same amount of resin D but no
additive, even though resin E has much lower melt index than resin
B. All resins in this figure contain 3 wt % of resin D.
[0078] FIG. 2 shows the elongational viscosity versus the shear
rate frequency measured using a constant temperature of 190.degree.
C. at a frequency sweep in a TA Instruments "Advanced Rheometric
Expansion System (ARES)". The incorporation of the additive changes
the behavior of Resins B and C at low shear rates as compared to
resins A and E. All resins in this figure contain 3 wt % of resin
D.
[0079] FIG. 3 shows the melt strength at the plateau versus the
melt index (ASTM method D-1238 at 190.degree. C. with 2.16 kg, in
g/10 minutes) for four Ziegler-Natta catalyzed polyethylene resins
with no additive (resins A, B, C, and E) and inventive resins B and
C with different amounts of the additive and resin E with 60 ppm
additive. Inventive resins B, C and E have higher melt strength at
the plateau when compared with resins that have similar melt index
and no additive. All resins contain 3 wt % of resin D.
[0080] FIG. 4 shows the phase angle (.degree.) versus the complex
modulus (G*) measured using a constant temperature of 190.degree.
C. at a frequency sweep in a TA Instruments "Advanced Rheometric
Expansion System (ARES)". Inventive resin B with different amounts
of the additive is compared with comparative resin A, a resin that
does not contain long chain branches. All resins contain 3 wt % of
resin D.
[0081] FIG. 5 shows the phase angle (.degree.) versus the complex
modulus (G*) measured using a constant temperature of 190.degree.
C. at a frequency sweep in a TA Instruments "Advanced Rheometric
Expansion System (ARES)". Inventive resin C with different amounts
of the additive is compared with comparative resin E, a resin that
does not contain long chain branches. All resins contain 3 wt % of
resin D.
Resin Description:
[0082] Resin A (Dowlex 61528.20) is a Ziegler-Natta catalyzed
polyethylene resin made in a solution process having melt index of
0.5 g/10 min (at 190.degree. C., 2.16 kg ASTM D-1238) and a density
0.921 g/cm.sup.3 (ASTM D792).
[0083] Resin B (Dowlex TG 2085B) is a Ziegler-Natta catalyzed
polyethylene resin made in a solution process having a melt index
of 0.95 g/10 min (at 190.degree. C., 2.16 kg ASTM D-1238) and a
density 0.919 g/cm.sup.3 (ASTM D792).
[0084] Resin C (Dowlex NG 5085B) is a Ziegler-Natta catalyzed
polyethylene made in a slurry process having a melt index of 1.3
g/10 min (at 190.degree. C., 2.16 kg ASTM D-1238) and a density of
0.918 g/cm.sup.3 (ASTM D792).
[0085] Resin D (LDPE 208C/206M) is a homopolymer ethylene resin
made in a high-pressure tubular reactor having a melt index of 0.7
g/10 min (at 190.degree. C., 2.16 kg ASTM D-1238) and a density of
0.925 g/cm.sup.3 (ASTM D792).
[0086] Resin E (Dowlex 2045) is a Ziegler-Natta catalyzed
polyethylene resin made in a solution process having melt index of
1.0 g/10 min (at 190.degree. C., 2.16 kg ASTM D-1238) and a density
0.920 g/cm.sup.3 (ASTM D792).
[0087] Resins A, B, C, and E in the table below all additionally
contain 3 wt % of resin D.
TABLE-US-00001 Density Ratio g/cm.sup.3 Melt Viscosity at viscosity
at (ASTM Conventional GPC I.sub.2 I.sub.10 I.sub.10/I.sub.2
Strength 0.1 rad/s 0.1 to 100 Samples D792) Mn Mw Mz Mw/Mn (g/10
min) (g/10 min) (g/10 min) (cN) (Pa-s) shear rates Resin A 0.921
31,322 150,495 582,495 4.80 0.50 3.96 7.92 6.8 16,356 7.6 Resin B
0.919 25,380 110,400 321,500 4.35 0.90 7.23 8.03 4.8 9,700 5.8 (no
additive) Resin B + 0.919 26,870 111,330 320,400 4.14 0.77 6.91
8.97 5.6 12,015 6.9 30 ppm additive Resin B + 0.918 26,100 111,920
331,200 4.29 0.69 6.4 9.28 6.4 14,480 8.2 60 ppm additive Resin C
0.918 23,830 100,000 291,800 4.20 1.25 10.46 8.37 3.5 6,760 4.8 (no
additive) Resin C + 0.918 23,780 100,670 301,400 4.23 1.01 9.36
9.27 4.8 9,810 6.6 60 ppm additive Resin C + 0.918 25,470 117,120
359,600 4.60 0.92 8.58 9.29 5.8 12,040 7.7 80 ppm additive Resin D
0.925 13,670 101,325 296,650 7.41 0.70 NS NA 16 17,650 22.7 Resin E
0.920 26,031 115,576 360,140 4.44 1.00 7.96 7.96 4.6 8,395 5.5
[0088] From the above examples, it is demonstrated that addition of
the additive results in changes to the molecular weight
distribution and significantly increases melt strength, at levels
compared to comparative resins A and E, without significantly
increasing the molecular weight. For example, the molecular weight
distribution is broadened as shown by a minimum of 10% increase in
I.sub.10I.sub.2 over the comparative resin. The melt strength
increases from 16 to 65% over the comparative resin. It can also be
seen that the addition of the additive results in resins having
higher melt strength than resins with higher molecular weight that
were made using same polymerization technology (Resins A and E).
From the above examples it is demonstrated that the addition of the
additive results in resins with higher ratio of elongational
viscosities at 0.1 to 100 s.sup.-1 shear rates, and this manifests
in lower pressure drop requirements in an extruder when these
resins are processed further. The change over the comparative
resins in the elongational viscosity ratio ranges from 19 to 60%,
depending on the set of resins and amount of additive used.
[0089] The following embodiments are expressly considered to be
part of the present invention although each embodiment may not be
separately claimed. [0090] 1) A method for increasing the melt
strength of a target polyethylene resin comprising the steps of:
[0091] a) selecting a target polyethylene resin having a density,
as determined according to ASTM D792, in the range of from 0.865
g/cm.sup.3 to 0.962 g/cm.sup.3, and a melt index, as determined
according to ASTM D1238 (2.16 kg, 190.degree. C.), in the range of
from 0.01 g/10 min to 100 g/10 min; [0092] b) reacting an alkoxy
amine derivative in an amount less than 900 parts derivative per
million parts of total polyethylene resin with the polyethylene
resin under conditions sufficient to increase the melt strength of
the polyethylene resin [0093] 2) The method of embodiment 1 wherein
the alkoxy amine derivative corresponds to the formula:
[0093] (R.sub.1)(R.sub.2)N--O--R.sub.3
where R.sub.1 and R.sub.2 are each independently of one another,
hydrogen, C.sub.4-C.sub.42 alkyl or C.sub.4-C.sub.42 aryl or
substituted hydrocarbon groups comprising O and/or N, and where
R.sub.1 and R.sub.2 may form a ring structure together; and R.sub.3
is hydrogen, a hydrocarbon or a substituted hydrocarbon group
comprising O and/or N. [0094] 3) The method of embodiment 1 wherein
the alkoxy amine derivative is a hydroxylamine ester. [0095] 4) The
method of embodiment 3 wherein the hydroxylamine ester is
hydroxylamine ester being
9-(acetyloxy)-3,8,10-triethyl-7,8,10-trimethyl-1,5-dioxa-9-azaspiro[5.5]u-
ndec-3-yl]methyl octadecanoate [0096] 5) The method of embodiment 1
wherein the alkoxy amine derivative is added to the target
polyethylene resin as a masterbatch comprising the alkoxy amine
derivative along with a carrier resin. [0097] 6) The method of
embodiment 5 wherein the carrier resin is selected from the group
consisting of HDPE, LLDPE, and LDPE. [0098] 7) The method of
embodiment 6 wherein the carrier resin is LDPE and the LDPE resin
has a vinyl concentration in the range of from 0 to 0.5 vinyls per
1,000 carbons. [0099] 8) The method of embodiment 7 wherein the
carrier resin has a vinyl concentration less than 0.1 vinyls per
1,000 carbons. [0100] 9) The method of embodiment 6 wherein the
carrier resin is HDPE and the HDPE resin has a vinyl concentration
in the range of from 0 to 0.5 vinyls per 1,000 carbons. [0101] 10)
The method of embodiment 9 wherein the carrier resin has a vinyl
concentration less than 0.05 vinyls per 1000 carbons. [0102] 11)
The method of embodiment 6 wherein the carrier resin is
substantially free of antioxidant compounds, in the range of 0 to
1,000 ppm. [0103] 12) The method of embodiment 11 wherein the
carrier resin is free of primary antioxidant compounds. [0104] 13)
The method of embodiment 1 wherein the alkoxy amine derivative is
reacted with the polyethylene resin in a reactive extrusion
process. [0105] 14) The method of embodiment 1 wherein the target
resin comprises LLDPE resin derived from ethylene monomer and
alpha-olefin comonomers having three to twelve carbons. [0106] 15)
The method of embodiment 1 wherein the target polyethylene resin
comprises LLDPE resin with vinyl content in the range of from 0 to
0.5 vinyls per 1,000 carbons. [0107] 16) The method of embodiment 1
wherein the target resin comprises blends of LDPE and LLDPE resins.
[0108] 17) The method of embodiment 1 wherein the target resin
comprises blends of HDPE and LLDPE resins. [0109] 18) The method of
embodiment 1 wherein the target resin comprises blends of HDPE and
LDPE resins. [0110] 19) The method of embodiment 1 wherein the
target polyethylene resin is substantially free of primary
antioxidants, preferably in the range of 0 to 1,000 ppm. [0111] 20)
The method of embodiment 1 wherein the alkoxy amine derivative is
added in an amount of from 0.003% to less than 0.09% of the total
amount of polyethylene polymer by weight. [0112] 21) The method of
embodiment 5 wherein the masterbatch is produced by melt extruding
a mixture of the carrier resin and the derivative at extruder
temperatures below 250.degree. C. [0113] 22) The method of
embodiment 1 wherein the melt strength is increased by at least 25%
compared to a substantially similar polyethylene resin which has
not been reacted with an alkoxy amine derivative. [0114] 23) The
method of embodiment 1 further comprising the step of adding one or
more antioxidants to the target resin after the target resin has
been reacted with the derivative. [0115] 24) A method for
increasing the elongational viscosity of a target polyethylene
resin at shear rates below 1 rad/s comprising the steps of: [0116]
a) selecting a target polyethylene resin having a density, as
determined according to ASTM D792, in the range of from 0.865
g/cm.sup.3 to 0.962 g/cm.sup.3, and a melt index, as determined
according to ASTM D1238 (2.16 kg, 190.degree. C.), in the range of
from 0.01 g/10 min to 100 g/10 min; [0117] b) reacting an alkoxy
amine derivative with the target polyethylene resin in an amount
and under conditions sufficient to increase the elongational
viscosity of the target polyethylene resin. [0118] 25) The method
of embodiment 23 wherein the elongational viscosity of the target
polyethylene resin is increased by at least 25% compared to a
substantially similar polyethylene resin which has not been reacted
with an alkoxy amine derivative. The method of embodiment 23
wherein the elongational viscosity ratio of the target polyethylene
resin at 0.1 to 100 rads is increased by at least 25% compared to a
substantially similar polyethylene resin which has not been reacted
with an alkoxy amine derivative. The use of an alkoxy amine
derivative to improve the melt strength and/or elongational
viscosity of a target polyethylene resin wherein the alkoxy amine
derivative is added to the target polyethylene resin in a reactive
extrusion process. [0119] 28) A fabricated article made from a
target polyethylene resin made according to the method of
embodiment 1. [0120] 29) A fabricated article according to
embodiment 27 wherein the article is selected from the group
consisting of films, sheets, pipes or blow molded articles. [0121]
30) A fabricated article according to embodiment 28 which is a film
that retains the mechanical properties as the original resin with
increased melt strength and good processability when compared to
films made of resins which have not been reacted with an alkoxy
amine derivative. A fabricated article according to embodiment 27
that has sufficient antioxidants added in the final processing step
to completely stabilize the resin. [0122] 32) An ethylene-based
polymer composition formed by reacting [0123] a) a target
polyethylene resin having characterized by a resin having a
density, as determined according to ASTM D792, in the range of from
0.865 g/cm.sup.3 to 0.962 g/cm.sup.3, and a melt index, as
determined according to ASTM D1238 (2.16 kg, 190.degree. C.), in
the range of from 0.01 g/10 min to 100 g/10 min; with [0124] b) b)
an alkoxy amine derivative in an amount less than 900 parts alkoxy
amine derivative per million parts of total polyethylene resin in
the composition, under conditions sufficient to increase the melt
strength of the target polyethylene resin. [0125] 33) The
ethylene-based polymer composition of embodiment 32 wherein the
target polyethylene resin is further characterized by having more
than 10 trisubstituted unsaturation units/1,000,000 C. [0126] 34)
The ethylene-based polymer composition of embodiment 32 wherein the
alkoxy amine derivative corresponds to the formula:
[0126] (R.sub.1)(R.sub.2)N--O--R.sub.3 [0127] where R.sub.1 and
R.sub.2 are each independently of one another, hydrogen,
C.sub.4-C.sub.42 alkyl or C.sub.4-C.sub.42 aryl or substituted
hydrocarbon groups comprising O and/or N, and where R.sub.1 and
R.sub.2 may form a ring structure together; and R.sub.3 is
hydrogen, a hydrocarbon or a substituted hydrocarbon group
comprising O and/or N. [0128] 35) The ethylene-based polymer
composition of embodiment 32 wherein the alkoxy amine derivative is
a hydroxylamine ester. [0129] 36) The ethylene-based polymer
composition of embodiment 35 wherein the hydroxylamine ester is
hydroxylamine ester being
9-(acetyloxy)-3,8,10-triethyl-7,8,10-trimethyl-1,5-dioxa-9-azaspiro[5.5]u-
ndec-3-yl]methyl octadecanoate. [0130] 37) The ethylene-based
polymer composition of embodiment 32 wherein the alkoxy amine
derivative is added to the polyethylene resin as a masterbatch
comprising the alkoxy amine derivative along with a carrier resin.
[0131] 38) The ethylene-based polymer composition of embodiment 37
wherein the carrier resin is selected from the group consisting of
HDPE, LLDPE, and LDPE. [0132] 39) The ethylene-based polymer
composition of embodiment 38 wherein the carrier resin is LDPE and
the carrier LDPE resin has a trisubstituted unsaturation
unit/1,000,000 C in the range of from 0 to 500. [0133] 40) The
ethylene-based polymer composition of embodiment 39 wherein the
trisubstituted unsaturation unit/1,000,000 C concentration is less
than 100. [0134] 41) The ethylene-based polymer composition of
embodiment 38 wherein the carrier resin is HDPE and the carrier
HDPE resin has a trisubstituted unsaturation unit/1,000,000 C in
the range of from 0 to 500. [0135] 42) The ethylene-based polymer
composition of embodiment 41 wherein the trisubstituted
unsaturation unit/1,000,000 C concentration is less than 50. [0136]
43) The ethylene-based polymer composition of embodiment 38 wherein
the carrier resin is characterized by being substantially free of
antioxidant compounds, in the range of from 0 to 1,000 parts
antioxidant per million parts carrier resin. [0137] 44) The
ethylene-based polymer composition of embodiment 43 wherein the
carrier resin is free of primary antioxidant compounds. [0138] 45)
The ethylene-based polymer composition of embodiment 32 wherein the
alkoxy amine derivative is reacted with the polyethylene resin in a
reactive extrusion process. [0139] 46) The ethylene-based polymer
composition of embodiment 32 wherein the target polyethylene resin
comprises LLDPE resin with trisubstituted unsaturation
unit/1,000,000 C in the range of from 0 to 500 ppm. [0140] 47) The
ethylene-based polymer composition of embodiment 32 wherein the
target polyethylene resin is substantially free of primary
antioxidants, preferably in the range of from 0 to 1,000 ppm.
[0141] 48) The ethylene-based polymer composition of embodiment 32
wherein the alkoxy amine derivative is added in an amount of from
0.003% to less than 0.09% of the total amount of polyethylene
polymer by weight. [0142] 49) The ethylene-based polymer
composition of embodiment 32 wherein the melt strength of the
target polyethylene resin is increased by at least 15% compared to
a substantially similar polyethylene resin which has not been
reacted with an alkoxy amine derivative. [0143] 50) An
ethylene-based polymer of increased elongational viscosity at shear
rates below 1 rad/s comprising: a polyethylene resin having a
density, as determined according to ASTM D792, in the range of from
0.865 g/cm.sup.3 to 0.962 g/cm.sup.3, and a melt index, as
determined according to ASTM D1238 (2.16 kg, 190.degree. C.), in
the range of from 0.01 g/10 min to 100 g/10 min; an alkoxy amine
derivative with the polyethylene resin in an amount and under
conditions sufficient to increase the elongational viscosity of the
polyethylene resin at shear rates below 1 rad/s. The polymer of
embodiment 50 wherein the elongational viscosity is increased by at
least 20% compared to a substantially similar polyethylene resin
which has not been reacted with an alkoxy amine derivative. [0144]
52) The polymer of embodiment 50 wherein the elongational viscosity
ratio at 0.1 to 100 rad/s is increased by at least 20% compared to
a substantially similar polyethylene resin which has not been
reacted with an alkoxy amine derivative. [0145] 53) The use of an
alkoxy amine derivative to improve the melt strength and/or
elongational viscosity of a polyethylene resin wherein the alkoxy
amine derivative is added to the polyethylene resin in a reactive
extrusion process. [0146] 54) A fabricated article made from a
polyethylene resin made according to embodiment 32. [0147] 55) A
fabricated article according to embodiment 54 wherein the article
is selected from the group consisting of films, sheets, pipes or
blow molded articles. [0148] 56) A fabricated article according to
embodiment 55 which is a film that retains the mechanical
properties as the original resin with increased melt strength and
good processability when compared to films made of resins which
have not been reacted with an alkoxy amine derivative. [0149] 57) A
film according to 56 which is a blend of LDPE and LLDPE resins.
[0150] 58) A film according to 57 which is used in monolayer or
multilayer films. [0151] 59) A film according to 58 which is used
in thick film applications. [0152] 60) A fabricated article
according to embodiment 54 that has sufficient antioxidants added
in the final processing step to completely stabilize the resin.
[0153] Although the invention has been described in considerable
detail through the preceding description and examples, this detail
is for the purpose of illustration and is not to be construed as a
limitation on the scope of the invention as it is described in the
appended claims. All United States patents, published patent
applications and allowed patent applications identified above are
incorporated herein by reference.
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