U.S. patent application number 15/951457 was filed with the patent office on 2018-08-16 for high density rotomolding resin.
This patent application is currently assigned to NOVA Chemicals (International) S.A.. The applicant listed for this patent is NOVA Chemicals (International) S.A.. Invention is credited to Celine Bellehumeur, Mark Hoidas.
Application Number | 20180230255 15/951457 |
Document ID | / |
Family ID | 57406287 |
Filed Date | 2018-08-16 |
United States Patent
Application |
20180230255 |
Kind Code |
A1 |
Bellehumeur; Celine ; et
al. |
August 16, 2018 |
HIGH DENSITY ROTOMOLDING RESIN
Abstract
The present disclosure provides high density polyethylene resins
having good low temperature impact resistance. The resins are
suitable for use in rotomolding application for large parts. The
resin is a bi- or trimodal resin produced using solution phase
polymerization in the presence of a single site catalyst.
Inventors: |
Bellehumeur; Celine;
(Calgary, CA) ; Hoidas; Mark; (Calgary,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NOVA Chemicals (International) S.A. |
Fribourg |
|
CH |
|
|
Assignee: |
NOVA Chemicals (International)
S.A.
Fribourg
CH
|
Family ID: |
57406287 |
Appl. No.: |
15/951457 |
Filed: |
April 12, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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15368893 |
Dec 5, 2016 |
9982077 |
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15951457 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08F 110/14 20130101;
C08F 2500/07 20130101; C08F 210/16 20130101; C08L 2205/025
20130101; C08F 2420/04 20130101; C08F 110/02 20130101; C08F 2500/01
20130101; C08L 2205/03 20130101; C08L 23/04 20130101; C08F 4/6592
20130101; C08F 110/02 20130101; C08F 2/00 20130101; C08F 110/14
20130101; C08F 2/00 20130101; C08F 210/16 20130101; C08F 2/001
20130101; C08F 210/16 20130101; C08F 210/14 20130101; C08F 2500/07
20130101; C08F 2500/10 20130101; C08F 2500/12 20130101; C08F
2500/13 20130101; C08L 23/04 20130101; C08L 2205/03 20130101; C08L
23/04 20130101; C08L 2205/025 20130101 |
International
Class: |
C08F 210/16 20060101
C08F210/16; C08F 110/02 20060101 C08F110/02; C08F 110/14 20060101
C08F110/14; C08L 23/04 20060101 C08L023/04; C08F 2/00 20060101
C08F002/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 8, 2015 |
CA |
2914166 |
Claims
1-16. (canceled)
17. A polyethylene resin comprising from 0.7 to 1.2 weight % of
1-octene and the balance ethylene, having a density from 0.948 to
0.953 g/cc, a melt index determined according to ASTM1238 under a
load of 2.16 kg at a temperature of 190.degree. C. (I.sub.2) from
1.0 to 1.5 g/10 minutes; a melt index determined according to
ASTM1238 under a load of 21.6 kg at a temperature of 190.degree. C.
(I.sub.21) from 32 to 55 g/10 minutes; a weight average molecular
weight (Mw) determined by gel permeation chromatography from 95,000
to 120,000; a number average molecular weight determined by gel
permeation chromatography (GPC) from 20,000 to 40,000; a z average
molecular weight (Mz) from 240,000 to 360,000; an Mw/Mn from 2.7 to
4.3; an Mz/Mw from 2.5 to 3.5; and having a CBDI (50) from 80 to
95, the molecular weight distribution determined by GPC of said
polymer being deconvoluted into at least two components comprising:
from 20 to 40 weight % of a first component having a calculated
weight average molecular weight (Mw) being from 200,000 to 250,000;
a calculated number average molecular weight from 90,000 to
140,000; a z average molecular weight 390,000 to 520,000 and an
estimated density from 0.921 to 0.930 g/cc; from 60 to 80 weight %
of a second component having a calculated weight average molecular
weight (Mw) being from 20,000 to 57,000; a calculated number
average molecular weight (Mn) from 10,000 to 27,000; a z average
molecular weight from 30,000 to 72,000 and an estimated density
from 0.948 to 0.953 g/cc, provided that the difference in
calculated density between component two and component one is less
than 0.030 g/cc.
18. The polyethylene resin according to claim 17 having a flex
secant modulus 1% from 1200 to 1300 MPa.
19. The polyethylene resin according to claim 18, having a mean
failure energy of not less than 150 ft.lb and a ductility not less
than 80% as measured using low temperature ARM impact performance
testing.
20. The polyethylene resin according to claim 19, having a degree
of residual unsaturation of less than 0.22 per 1000 carbon
atoms.
21. The polyethylene according to claim 20, wherein the first
component is present in an amount from 25 to 40 weight % of the
total polymer composition.
22. A polyethylene resin comprising from 0.7 to 1.2 weight % of
1-octene and the balance ethylene, having a density from 0.948 to
0.953 g/cc, a melt index determined according to ASTM1238 under a
load of 2.16 kg at a temperature of 190.degree. C. (I.sub.2) from
1.0 to 1.5 g/10 minutes; a melt index determined according to
ASTM1238 under a load of 21.6 kg at a temperature of 190.degree. C.
(I.sub.21) from 32 to 55 g/10 minutes; a weight average molecular
weight (Mw) determined by gel permeation chromatography from 95,000
to 120,000; a number average molecular weight (Mn) determined by
gel permeation chromatography (GPC) from 20,000 to 40,000; a z
average molecular weight (Mz) from 240,000 to 360,000; an Mw/Mn
from 2.7 to 4.3; an Mz/Mw from 2.5 to 3.5; and having a CBDI (50)
from 80 to 95, the molecular weight distribution determined by GPC
of said polymer being deconvoluted into at least three components
comprising: from 20 to 40 weight % of a first component having a
calculated weight average molecular weight (Mw) being from 170,000
to 265,000; a calculated number average molecular weight from
90,000 to 140,000; a z average molecular weight 390,000 to 520,000
and an estimated density from 0.921 to 0.930 g/cc; from 40 to 70
weight % of a second component having a calculated weight average
molecular weight (Mw) being from 20,000 to 57,000; a calculated
number average molecular weight (Mn) from 10,000 to 27,000; a z
average molecular weight 30,000 to 72,000 and an estimated density
from 0.948 to 0.953 g/cc, provided that the density difference
between component two and component one is from 0.025 to 0.030
g/cc; and from 3 to 20 weight % of a third component having a
calculated weight average molecular weight (Mw) being from 60,000
to 130,000; a calculated number average molecular weight from
30,000 to 65,000; a z average molecular weight 90,000 to 180,000
and an estimated density from 0.935 to 0.945 g/cc.
23. The polyethylene resin according to claim 22 having a flex
secant modulus 1% from 1200 to 1300 MPa.
24. The polyethylene resin according to claim 23, having a mean
failure energy of not less than 150 ft./lb. and a ductility greater
than 80% as measured using low temperature ARM impact performance
testing.
25. The polyethylene resin according to claim 24, having an
environmental stress crack resistance of not less than 200 hours
when measured at ESCR conditions A100 100% CO-630 and B100 100%
CO-630.
26. The polyethylene resin according to claim 25, having a degree
of residual unsaturation of less than 0.22 per 1000 carbon
atoms.
27. The polyethylene according to claim 26, wherein the first
component is present in an amount from 25 to 40 weight % of the
total polymer composition.
28. The polyethylene according to claim 15 wherein the third
component is present in an amount from 3 to 17 wt. % of the total
polymer composition.
Description
[0001] The present disclosure relates to rotomolding polyethylene
resins having a density of around 0.950 g/cc having good stiffness.
There do not appear to be any commercial rotomolding resins in this
density range. Products made from the resin have competitive
physical properties.
[0002] There are a number of different considerations for
manufacturing a resin suitable for use in rotomolding manufacture.
The resin needs to be: capable of production at commercially
acceptable rates of production; suitable for use in the rotomolding
process (e.g. for example having a suitable sintering temperature
and a suitable cooling rate to be removed from the mold) and
finally must have suitable properties for the end use application.
One important property sought is low temperature impact resistance.
Another important property sought is environmental stress crack
resistance. The resin should not develop cracks due to exposure to
chemicals, sunlight, etc. in applications such as tank sprayers for
agricultural use, cisterns, and smaller rotomolded parts.
[0003] U.S. Pat. No. 7,790,826, issued Sep. 7, 2010 to Davis et
al., assigned to Dow Global Technologies Inc. teaches a resin
useful in compression molding useful to manufacture caps for
bottled water or carbonated drinks. The disclosure does not teach
or suggest resins suitable for use in rotational molding
applications.
[0004] U.S. Pat. No. 6,448,341, issued Sep. 10, 2002 to Kolthammer
et al., assigned to Dow the Dow Chemical Company teaches a blend of
solution polymers which is useful in rotational molding. An
essential feature of the patent is one of the components has a
density of less than 0.908 g/cc. There is no component in the
polyethylene disclosed herein having a density less than 0.908
g/cc. Additionally the polymers of Kolthammer have an MI (I.sub.2)
from about 3 to 100 g/10 min. The polymers disclosed herein have an
MI (I.sub.2) from about 1.0 to 1.5 g/10 min.
[0005] The present disclosure seeks to provide a higher density
resin suitable for rotomolding applications having enhanced
stiffness and low warpage.
[0006] In one embodiment, the present disclosure provides a
polyethylene resin comprising less than 1.5 weight % of 1-octene
and the balance ethylene, having a density from 0.948 to 0.953
g/cc, a melt index determined according to ASTM1238 under a load of
2.16 kg at a temperature of 190.degree. C. (I.sub.2) from 1.0 to
1.5 g/10 minutes; a melt index determined according to ASTM1238
under a load of 21.6 kg at a temperature of 190.degree. C.
(I.sub.21) from 32 to 55 g/10 minutes; a weight average molecular
weight (Mw) determined by gel permeation chromatography (GPC) from
95,000 to 120,000; a number average molecular weight determined by
gel permeation chromatography (GPC) from 20,000 to 40,000; a z
average molecular weight (Mz) from 240,000 to 360,000; an Mw/Mn
from 2.5 to 4.5; an Mz/Mw from 2.5 to 3.5; and having a CBDI (50)
from 80 to 95, a degree of residual unsaturation less than 0.22 per
1000 carbon atoms, for example between 0.06 to 0.22, the molecular
weight distribution determined by GPC of said polymer being
deconvoluted into at least two components comprising:
[0007] from 20 to 40 weight % of a first component having a
calculated weight average molecular weight (Mw) being from 200,000
to 250,000; a calculated number average molecular weight (Mn) from
90,000 to 140,000; a z average molecular weight (Mz) from 390,000
to 520,000 and an estimated density from 0.921 to 0.930 g/cc;
[0008] from 40 to 70 weight % of a second component having a
calculated weight average molecular weight (Mw) being from 20,000
to 57,000; a calculated number average molecular weight (Mn) from
10,000 to 30,000; a z average molecular weight (Mz) from 30,000 to
80,000 and an estimated density from 0.948 to 0.953 g/cc, provided
that the density difference between component two and component one
is less 0.030 g/cc.
[0009] In a further embodiment, the composition comprises a third
component having a calculated weight average molecular weight (Mw)
being from 60,000 to 130,000; a calculated number average molecular
weight (Mn) from 30,000 to 65,000; a z average molecular weight
(Mz) from 90,000 to 180,000, and an estimated density from 0.935 to
0.945 g/cc, for example from 0.938 to 0.943 g/cc.
[0010] In a further embodiment, the polyethylene resin has a flex
secant modulus 1% from 1200 to 1300 MPa.
[0011] In a further embodiment, the polyethylene resin has a mean
failure energy of not less than 150 ft.lb and a ductility of
greater than 80% as measured using low temperature ARM impact
performance testing.
[0012] In a further embodiment, the polyethylene resin has an
environmental stress crack resistance of not less than 330 hours
when measured at ESCR conditions A100 100% CO-630 and B100 100%
CO-630.
[0013] In a further embodiment, the polyethylene resin comprises
not less than 0.6 weight % of 1-octene.
[0014] In a further embodiment, the polyethylene resin has an Mw/Mn
from 2.5 to 4.5.
[0015] In a further embodiment, the polyethylene resin has an Mz/Mw
from 2.5 to 3.5.
[0016] In a further embodiment, the first component is present in
an amount from 20 to 40 weight % of the total polymer
composition.
[0017] In a further embodiment, the second component is present in
an amount from 40 to 70 weight % of the total polymer
composition.
[0018] In a further embodiment, the present disclosure provides a
rotomolded part using the above resin.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a plot of the molecular weight distribution
obtained by GPC of the polymer of invention example 1 and the
computer model predictions of the molecular weight distributions of
the first, second and third ethylene polymers that are comprised in
the polymer of invention example 1.
[0020] FIG. 2 is a plot of the molecular weight distribution
obtained by GPC of the polymer of invention example 2 and the
computer model predictions of the molecular weight distributions of
the first, second and third ethylene polymers that are comprised in
the polymer of invention example 2.
[0021] FIG. 3 is a plot of the molecular weight distribution
obtained by GPC of the polymer of invention example 3 and the
computer model predictions of the molecular weight distributions of
the first and second ethylene polymers that are comprised in the
polymer of invention example 3.
[0022] FIG. 4 is a plot of the molecular weight distribution
obtained by GPC of the polymer of comparative example 3 and the
computer model predictions of the molecular weight distributions of
the first, and second ethylene polymers that are comprised in the
polymer of comparative example 3.
[0023] FIG. 5 is a plot of the calculated w.sub.i.cndot.PSP2.sub.i
values against log M for the inventive example 1 , which can also
be insightful when attempting understand and predict structure
property relationships. The area underneath the resulting
w.sub.i.cndot.PSP2.sub.i vs. log M curve defines PSP2 for the whole
polymer sample.
[0024] FIG. 6 is a plot of the calculated w.sub.i.cndot.PSP2.sub.i
values against log M for the inventive example 2.
[0025] FIG. 7 is a plot of the calculated w.sub.i.cndot.PSP2.sub.i
values against log M for the inventive example 3.
[0026] FIG. 8 is a plot of the calculated w.sub.i.cndot.PSP2.sub.i
values against log M for comparative example 1.
[0027] FIG. 9 is a plot of the calculated w.sub.i.cndot.PSP2.sub.i
values against log M for comparative example 2.
[0028] FIG. 10 is a plot of the calculated w.sub.i.cndot.PSP2.sub.i
values against log M for comparative example 3.
DETAILED DESCRIPTION
[0029] Numbers Ranges
[0030] Other than in the operating examples or where otherwise
indicated, all numbers or expressions referring to quantities of
ingredients, reaction conditions, etc. used in the specification
and claims are to be understood as modified in all instances by the
term "about". Accordingly, unless indicated to the contrary, the
numerical parameters set forth in the following specification and
attached claims are approximations that can vary depending upon the
properties that the present disclosure desires to obtain. At the
very least, and not as an attempt to limit the application of the
doctrine of equivalents to the scope of the claims, each numerical
parameter should at least be construed in light of the number of
reported significant digits and by applying ordinary rounding
techniques.
[0031] Notwithstanding that the numerical ranges and parameters
setting forth the broad scope of the invention are approximations,
the numerical values set forth in the specific examples are
reported as precisely as possible. Any numerical values, however,
inherently contain certain errors necessarily resulting from the
standard deviation found in their respective testing
measurements.
[0032] Also, it should be understood that any numerical range
recited herein is intended to include all sub-ranges subsumed
therein. For example, a range of "1 to 10" is intended to include
all sub-ranges between and including the recited minimum value of 1
and the recited maximum value of 10; that is, having a minimum
value equal to or greater than 1 and a maximum value of equal to or
less than 10. Because the disclosed numerical ranges are
continuous, they include every value between the minimum and
maximum values. Unless expressly indicated otherwise, the various
numerical ranges specified in this application are
approximations.
[0033] All compositional ranges expressed herein are limited in
total to and do not exceed 100 percent (volume percent or weight
percent) in practice. Where multiple components can be present in a
composition, the sum of the maximum amounts of each component can
exceed 100 percent, with the understanding that, and as those
skilled in the art readily understand, that the amounts of the
components actually used will conform to the maximum of 100
percent.
[0034] The polymers disclosed herein are made using a process as
described in U.S. Pat.No. 8,101,693, issued Jan. 24, 2012 in the
name of Van Asseldonk et al., assigned to NOVA Chemicals
(International) S.A. the text of which is herein incorporated by
reference.
[0035] The process uses two CSTR reactors followed by a tubular
reactor. The temperature of the reactor(s) in a high temperature
solution process is from about 80.degree. C. to about 300.degree.
C., for example from about 120.degree. C. to 250.degree. C. The
upper temperature limit will be influenced by considerations that
are well known to those skilled in the art, such as a desire to
maximize operating temperature (so as to reduce solution
viscosity), while still maintaining good polymer properties (as
increased polymerization temperatures generally reduce the
molecular weight of the polymer). In some embodiments, the upper
polymerization temperature will for example be between 200 and
300.degree. C. In some embodiments the reaction process is a
"medium pressure process", meaning that the pressure in the
reactor(s) is for example less than about 6,000 psi (about 42,000
kiloPascals or kPa). Example pressures are from 10,000 to 40,000
kPa (1450-5800 psi), or for example from about 14,000-22,000kPa
(2,000 psi to 3,000 psi). In some reaction schemes, the pressure in
the reactor system should be high enough to maintain the
polymerization solution as a single phase solution and to provide
the necessary upstream pressure to feed the polymer solution from
the reactor system through a heat exchanger system and to a
devolatilization system. Other systems permit the solvent to
separate into a polymer rich and polymer lean stream to facilitate
polymer separation.
[0036] The solution polymerization process may be conducted in a
stirred "reactor system" comprising one or more stirred tank
reactors or in one or more loop reactors or in a mixed loop and
stirred tank reactor system. The reactors may be in tandem or
parallel operation. In some embodiments, in a dual tandem reactor
system, the first polymerization reactor preferably operates at
lower temperature. The residence time in each reactor will depend
on the design and the capacity of the reactor. In some embodiments,
the reactors should be operated under conditions to achieve a
thorough mixing of the reactants.
[0037] In some embodiments, the solution polymerization process
uses at least two polymerization reactors in series. The
polymerization temperature in the first reactor is from about
80.degree. C. to about 180.degree. C. (for example from about
120.degree. C. to 160.degree. C.) and the second reactor is
preferably operated at a higher temperature (up to about
220.degree. C.). In some embodiments the reaction process is a
"medium pressure process", meaning that the pressure in each
reactor is, for example, less than about 6,000 psi (about 42,000
kilopascals or kPa), or for example from about 2,000 psi to 3,000
psi (about 14,000 22,000 kPa).
[0038] The term "tubular reactor" is meant to convey its
conventional meaning--namely a simple tube. The tubular reactor
disclosed herein will have a length/diameter (L/D) ratio of at
least 10/1. The tubular reactor is not agitated. For example, the
tubular reactor is operated adiabatically. Thus, as polymerization
progresses, the remaining comonomer is increasingly consumed and
the temperature of the solution increases (both of which improve
the efficiency of separating the remaining comonomer from the
polymer solution). In some embodiments the temperature increase
along the length of the tubular reactor is greater than 3.degree.
C. (i.e., that the discharge temperature from the tubular reactor
is at least 3.degree. C. greater than the discharge temperature
from the CSTR that feeds the tubular reactor).
[0039] The tubular reactor used herein has a feed port for
additional ethylene and solvent. The feed is "tempered"--i.e., the
temperature of the additional ethylene and/or solvent is heated to
above ambient (for example to about 100.degree. C.) but the
temperature is below the discharge temperature of the tubular
reactor. In some embodiments, the ethylene is tempered to between
100 and 200.degree. C. In some embodiments, the ethylene is added
with solvent.
[0040] The amount of solvent (expressed as a weight ratio, based on
ethylene) is, for example, from 20/1 to 0.1/1, or for example from
10/1 to 1/1.
[0041] Optionally, the tubular reactor may also have feed ports for
additional catalyst, cocatalyst, comonomer and/or telomerization
agent (such as hydrogen). However, in some embodiments, no
additional catalyst is added to the tubular reactor.
[0042] The total volume of the tubular reactor is, for example, at
least 10 volume % of the volume of the at least one CSTR, or for
example from 30% to 200% (for clarity, if the volume of the CSTR is
1000 litres, then the volume of the tubular reactor is at least 100
litres and is, for example, from 300 to 2000 litres).
[0043] The total amount of ethylene added to the tubular reactor
is, for example, from 1 to 50 weight % of the total ethylene added
to the CSTR(s). For example, if one CSTR is being operated with an
ethylene flow rate of 1000 kg/hr, then the ethylene flow to the
tubular reactor would be from 10 to 500 kg/hr. Similarly, if two
CSTR(s) were being operated with an ethylene flow of 1000 kg/hr to
the first and 500 kg/hr to the second, then the flow of ethylene to
the tubular reactor would be from 15 to 750 kg/hr.
[0044] Overall, the resulting polymer or polyethylene resin
comprising less than 1.5, in one embodiment more than 0.6, in a
further embodiment from 0.7 to 1.2 weight % of 1-octene and the
balance ethylene, having a density from 0.948 to 0.953, a melt
index determined according to ASTM1238 under a load of 2.16 kg at a
temperature of 190.degree. C. (12) from 1.0 to 1.5 g/10 minutes, in
some embodiments from 1.1 to 1.3 g/10 minutes ; a melt index
determined according to ASTM1238 under a load of 21.6 kg at a
temperature of 190.degree. C. (121) from 32 to 55 g/10 minutes in
some embodiments from 36 to 50 g/10 minutes; a weight average
molecular weight (Mw) determined by gel permeation chromatography
from 95,000 to 120,000, in some embodiments, from 100,000 to
115,000; a number average molecular weight (Mn) determined by gel
permeation chromatography from 20,000 to 40,000 in some embodiments
from 25,000 to 35,000; a z average molecular weight (Mz) from
240,000 to 360,000 in some embodiments from 260,000 to 325,000; an
Mw/Mn from 2.3 to 4.5, in an alternate embodiment from 2.7 to 4.3;
an Mz/Mw from 2.5 to 3.5; and having a CBDI (50) from 80 to 95; a
degree of residual unsaturation less than 0.22 per 1000 carbon
atoms, for example between 0.06 to 0.22, in some embodiments less
than 20.
[0045] In addition, the resin when molded into parts or plaques has
the following properties:
[0046] an environmental stress crack resistance of not less than
330 hours when measured at ESCR conditions A 100 100% CO-630 and
B100 100% CO-630; a flex secant modulus 1% from greater than 1200,
in some embodiments from 1200 to 1300 MPa; a mean failure energy of
not less than 150 ft.lb; and a ductility greater than 80% as
measured using low temperature ARM impact performance testing; and
a primary structure parameter (PSP2) of less than 8, for example
from about 2 to 7, or for example from 2.5 to 5.
[0047] The PSP2 calculation as outlined by DesLauriers and Rohlfing
in Macromolecular Symposia (2009), 282 (Polyolefin
Characterization-ICPC 2008), pages 136-149 is incorporated by
reference herein. The PSP2 calculation can be generally described
as a multistep process. The first step involves estimating the
homopolymer (or low comonomer polymer) density of a sample from the
sample's molecular weight distribution as described by Equation 1.
The first step takes into account the effects of molecular weight
on sample density.
1/.rho.=.SIGMA.(w.sub.i/.rho..sub.i)=.intg.1/.rho.(dw/dLog M) dLog
M (Eq. 1)
where: .rho.=1.0748-(0.0241)Log M.
[0048] Density values at molecular weights less than 720 g/mol are
equal to 1.006 g/cm.sup.3 according to this method. In the second
step, to further account for the added contributions to density
suppression by the presence of short chain branching for each
molecular weight (MW) slice, the difference between the measured
bulk density of copolymer and the calculated homopolymer density is
divided by the overall short chain branching (SCB) level (as
measured by size exclusion chromatography-Fourier transform
infrared spectroscopy or by C13-NMR) and subsequently applied to
the SCB level in each MW slice. The original observed bulk density
of the copolymer (down to 0.852 g/cm.sup.3) is obtained through
summation of the MW slices as described above. The calculations
have been simplified by assuming that all SCB levels will have the
same effect on density suppression. However, it is to be understood
that the effectiveness of a particular SCB level to suppress
density will vary (i.e., the ability of SCB to disrupt
crystallinity decreases as the level of SCB increases).
Alternately, if the density of the copolymer is not known, then the
effects of SCB on sample density can be estimated in the second
step by using Equation 2 as described by DesLauriers and Rohlfing
in U.S. Patent Application Publication No. 2007/0298508, issued as
U.S. Pat. No. 7,803,629, where the change in density .DELTA.p
refers to the value that is subtracted from the value given in
equation 1 on a molecular slice by slice basis.
.DELTA..rho.=C.sub.1(SCB/PDI.sup.n).sup.C2-C.sub.3(SCB/PDI.sup.n).sup.C4
(Eq. 2)
[0049] In Equation 2, C.sub.1=1.25E-02, C.sub.2=0.5,
C.sub.3=7.51E-05, C.sub.4=0.62 and n=0.32.
[0050] The third step in calculating PSP2 is to calculate the
quantity of 2 I.sub.c+l.sub.a where I.sub.c is the estimated
crystalline lamella thickness (in nm) and la is the estimated
thickness (in nm) of the amorphous material at a particular
molecular weight given by the following equations:
T m ( .degree. C . ) = ( 20587.5149640828 ) .rho. 3 - (
63826.2771547794 ) .rho. 2 + ( 65965.7028912473 ) -
22585.2457979131 ( Eq 3. ) l c ( nm ) = 0.624 nm T m 0 ( K ) T m 0
( K ) - T m ( K ) ( Eq . 4 ) ##EQU00001##
[0051] In equation 3, assigned values of 20.degree. C. and
142.5.degree. C. are given for density values of 0.852 g/cm.sup.3
and 1.01 g/cm.sup.3, respectively. Equation 4 is a form of the well
accepted Gibbs Thompson equation. The thickness of the amorphous
layer (I.sub.a) is calculated using the equations 5a and 5b:
w c = ( .rho. c .rho. ) ( .rho. - .rho. a .rho. c - .rho. a ) ( Eq
. 5 a ) l a = .rho. c l c ( 1 - w c ) / .rho. a w c ( Eq . 5 b )
##EQU00002##
[0052] where: w.sub.c=weight fraction crystallinity
[0053] .rho.=calculated density of MW slice
[0054] .rho..sub.c=density of 100% crystalline sample (assigned
1.006 g/cm.sup.3)
[0055] .rho..sub.a=density of amorphous phase (0.852
g/cm.sup.3)
[0056] The fourth step calculates the tie molecule probability (P)
for each molecular weight and respective
[0057] 2 I.sub.c+I.sub.a value according to equations 6a and
6b:
P = 1 3 .intg. L .infin. r 2 exp ( - b 2 r 2 ) dr .intg. 0 .infin.
r 2 exp ( - b 2 r 2 ) dr ( Eq . 6 a ) where b 2 = 3 2 r _ 2 and r _
2 = ( Dnl 2 ) . ##EQU00003##
[0058] The symbols above have the following meanings:
[0059] P=Probability of tie-chain formation
[0060] L=Critical distance (nm)=2 I.sub.c+I.sub.a
[0061] D=Chain extension factor in melt=6.8 for polyethylene
[0062] n=Number of links=M.sub.w/14 for polyethylene
[0063] I=The link length=0.153 nm for polyethylene
P = 1 3 .pi. 4 b 3 - .intg. 0 L r 2 exp ( - b 2 r 2 ) dr .pi. 4 b 3
= 1 3 ( 1 - 4 b 3 .pi. .intg. 0 L r 2 exp ( - b 2 r 2 ) dr ) ( Eq .
6 b ) ##EQU00004##
[0064] Finally, PSP2 values are calculated from Equations 6a and 6b
by treating this value as a weighing factor (P.sub.i) for each
slice of the MWD, where P.sub.i was arbitrarily
multiplied.times.100 and subsequently defined as PSP2.sub.i. As in
all of the aforementioned calculations, this value at each slice is
multiplied by the respective weight fraction (w.sub.i) of the MWD
profile in order to obtain a value for the bulk polymer.
[0065] Plots of the calculated w.sub.i.cndot.PSP2.sub.i values
against log M for the inventive examples and comparative examples
are shown in FIGS. 4 to 9, respectively, which can also be
insightful when attempting understand and predict structure
property relationships. The area underneath the resulting
w.sub.i.cndot.PSP2.sub.i vs. log M curve defines PSP2 for the whole
polymer sample.
[0066] As noted above the resin is produced in a process using two
CSTR's in series followed by a tubular reactor (after burner). As
such the gel permeation chromatograph (GPC) of the resin may be
mathematically deconvoluted into three components.
[0067] The first component is a high molecular weight lowest
density component. This component is made in the first CSTR at the
lowest temperature. The density of the component is estimated to be
from 0.921 to 0.930 g/cc, in an alternate embodiment from 0.921 to
0.925 g/cc. The component is present in an amount from 20 to 40, in
an alternative embodiment from 25 to 40 weight % of the total
polymer. The component has a calculated weight average molecular
weight (Mw) being from 170,000 to 265,000; a calculated number
average molecular weight (Mn) from 90,000 to 140,000; a z average
molecular weight (Mz) from 390,000 to 520,000.
[0068] This first component has a calculated Mw/Mn from about 1.9
to 2.2, for example from 1.9 to 2.1. This first component has a
calculated Mz/Mw from 1.4 to 1.6, in an alternate embodiment 1.5.
The first component has a calculated short chain (i.e., six carbon
chains) branch frequency of about 1.8 per 1000 carbon atoms.
[0069] The second component is a lower molecular weight highest
density component. This component is made in the second CSTR at the
highest temperature the second CSTR. The density of the component
is estimated to be from 0.948 to 0.953 g/cc, in an alternate
embodiment from 0.949 to 0.952 g/cc, provided that the density
difference between component two and component one is less than
0.030 g/cc. The component is present in an amount from 40 to 70, in
an alternative embodiment from 60 to 80 weight % of the total
polymer. The component has a calculated weight average molecular
weight (Mw) being from 20,000 to 57,000; a calculated number
average molecular weight (Mn) from 10,000 to 27,000; a z average
molecular weight (Mz) from 30,000 to 72,000. This second component
has a calculated Mw/Mn from about 1.7 to 2.2, for example from 1.9
to 2.1. This second component has a calculated Mz/Mw from 1.4 to
1.6, in an alternate embodiment 1.5. The second component has a
calculated short chain (i.e., six carbon chains) branch frequency
less than 0.5 per 1000 carbon atoms. The calculated difference in
density between the first component and second component is 0.025
to 0.030 g/cc.
[0070] The third component is an intermediate molecular weight and
density. This component is made in the tubular reactor at high
temperature. The density of the component is calculated to be from
0.935 to 0.945 g/cc, in an alternate embodiment from 0.938 to 0.942
g/cc. In this embodiment, the third component comprises the balance
of the polymer, for example from about 3 to about 20 weight % of
the composition, in some embodiments from 3 to 17 weight % of the
composition. The component has a calculated weight average
molecular weight (Mw) being from 60,000 to 130,000; a calculated
number average molecular weight (Mn) from 30,000 to 65,000; a z
average molecular weight (Mz) from 90,000 to 180,000. This third
component has a calculated Mw/Mn from about 1.9 to 2.1, or for
example about 2. This third component has a calculated Mz/Mw from
1.4 to 1.6, in an alternate embodiment 1.5.
[0071] The polymer may be made using a solution polymerization
process as described above. In the solution polymerization of
ethylene with one or more comonomers, for example C.sub.3-8, for
example C.sub.4-8 alpha olefins, for example hexene or octene, or
for example octene, the monomers are, for example, dissolved in an
inert hydrocarbon solvent, for example, a C.sub.5-12 hydrocarbon,
which may be unsubstituted or substituted by a C.sub.1-4 alkyl
group, such as pentane, methyl pentane, hexane, heptane, octane,
cyclohexane, methylcyclohexane and hydrogenated naphtha. An example
of a suitable solvent that is commercially available is "Isopar E"
(C.sub.8-12 aliphatic solvent, Exxon Chemical Co.).
[0072] Catalyst and activators are also dissolved in the solvent or
suspended in a diluent miscible with the solvent at reaction
conditions.
[0073] The Catalyst
[0074] The catalyst is a compound of the formula
##STR00001##
wherein M is selected from Ti, Zr and Hf; PI is a phosphinimine
ligand of the formula:
##STR00002##
wherein each R.sup.21 is independently selected from a hydrogen
atom; a halogen atom; hydrocarbyl radicals, for example,
C.sub.1-10, which are unsubstituted by or further substituted by a
halogen atom; C.sub.1-8 alkoxy radicals; C.sub.6-10 aryl or aryloxy
radicals; amido radicals; silyl radicals of the formula:
[0075] --S--(R.sup.22).sub.3
wherein each R.sup.22 is independently selected from hydrogen, a
C.sub.1-8 alkyl or alkoxy radical and C.sub.6-10 aryl or aryloxy
radicals; and a germanyl radical of the formula:
[0076] --Ge--(R.sup.22).sub.3
wherein R.sup.22 is as defined above;
[0077] L is a monoanionic cyclopentadienyl-type ligand
independently selected from cyclopentadienyl-type ligands, Y is
independently selected from activatable ligands; m is 1 or 2; n is
0 or 1; p is an integer and the sum of m+n+p equals the valence
state of M.
[0078] Example phosphinimines are those in which each R.sup.21 is a
hydrocarbyl radical, for example a C.sub.1-6 hydrocarbyl radical,
or for example a C.sub.1-4 hydrocarbyl radical.
[0079] The term "cyclopentadienyl" refers to a 5-member carbon ring
having delocalized bonding within the ring and typically being
bound to the active catalyst site, for example a group 4 metal (M)
through .eta..sup.5-bonds. The cyclopentadienyl ligand may be
unsubstituted or up to fully substituted with one or more
substituents selected from C.sub.1-10 hydrocarbyl radicals which
are unsubstituted or further substituted by one or more
substituents selected from a halogen atom and a C.sub.1-4 alkyl
radical; a halogen atom; a C.sub.1-8 alkoxy radical; a C.sub.6-10
aryl or aryloxy radical; an amido radical which is unsubstituted or
substituted by up to two C.sub.1-8 alkyl radicals; a phosphido
radical which is unsubstituted or substituted by up to two
C.sub.1-8 alkyl radicals; silyl radicals of the formula
--Si--(R).sub.3 wherein each R is independently selected from
hydrogen, a C.sub.1-8 alkyl or alkoxy radical, C.sub.6-10 aryl or
aryloxy radicals; and germanyl radicals of the formula
Ge--(R).sub.3 wherein R is as defined above. In some embodiments,
the cyclopentadienyl-type ligand is selected from a
cyclopentadienyl radical, an indenyl radical and a fluorenyl
radical which radicals are unsubstituted or up to fully substituted
by one or more substituents selected from a fluorine atom, a
chlorine atom; C.sub.1-4 alkyl radicals; and a phenyl or benzyl
radical which is unsubstituted or substituted by one or more
fluorine atoms.
[0080] Activatable ligands Y may be selected from a halogen atom,
C.sub.1-4 alkyl radicals, C.sub.6-20 aryl radicals, C.sub.7-12
arylalkyl radicals, C.sub.6-10 phenoxy radicals, amido radicals
which may be substituted by up to two C.sub.1-4 alkyl radicals and
C.sub.1-4 alkoxy radicals. In some embodiments, Y is selected from
a chlorine atom, a methyl radical, an ethyl radical and a benzyl
radical.
[0081] Suitable phosphinimine catalysts are Group 4 organometallic
complexes which contain one phosphinimine ligand (as described
above) and one cyclopentadienyl-type (L) ligand and two activatable
ligands. The catalysts are not bridged.
[0082] Activators
[0083] The activators for the catalyst are selected, for example,
from aluminoxanes and ionic activators.
[0084] Alumoxanes
[0085] Suitable alumoxane may be of the formula:
(R.sup.4).sub.2AlO(R.sup.4AlO).sub.mAl(R.sub.4).sub.2 wherein each
R.sup.4 is independently selected from C.sub.1-20 hydrocarbyl
radicals and m is from 0 to 50, for example R.sup.4 is a C.sub.1-4
alkyl radical and m is from 5 to 30. Methylalumoxane (or "MAO") in
which each R is methyl is an example alumoxane. Alumoxanes are well
known as cocatalysts, particularly for metallocene-type catalysts.
Alumoxanes are also readily available articles of commerce. The use
of an alumoxane cocatalyst generally uses a molar ratio of aluminum
to the transition metal in the catalyst from 20:1 to 1000:1. In
some embodiments the ratios are from 50:1 to 250:1.
[0086] Commercially available MAO typically contains free aluminum
alkyl (e.g. trimethylaluminum or "TMA") which may reduce catalyst
activity and/or broaden the molecular weight distribution of the
polymer. If a narrow molecular weight distribution polymer is
required, in some embodiments such commercially available MAO is
treated with an additive which is capable of reacting with the TMA.
Alcohols are some examples useful (with hindered phenols being
another example) for this purpose.
[0087] "Ionic Activators" Cocatalysts
[0088] So-called "ionic activators" are also well known for
metallocene catalysts. See, for example, U.S. Pat. No. 5,198,401
(Hlatky and Turner) and U.S. Pat. No. 5,132,380 (Stevens and
Neithamer).
[0089] Whilst not wishing to be bound by any theory, it is thought
by those skilled in the art that "ionic activators" initially cause
the abstraction of one or more of the activatable ligands in a
manner which ionizes the catalyst into a cation, then provides a
bulky, labile, non-coordinating anion which stabilizes the catalyst
in a cationic form. The bulky, non-coordinating anion permits
olefin polymerization to proceed at the cationic catalyst center
presumably because the non-coordinating anion is sufficiently
labile to be displaced by monomer which coordinates to the
catalyst. Example ionic activators are boron-containing ionic
activators described in (i) (iii) below:
[0090] (i) compounds of the formula
[R.sup.5]+[B(R.sup.7).sub.4].sup.- wherein B is a boron atom,
R.sup.5 is an aromatic hydrocarbyl (e.g. triphenyl methyl cation)
and each R.sup.7 is independently selected from phenyl radicals
which are unsubstituted or substituted with from 3 to 5
substituents selected from a fluorine atom, a C.sub.1-4 alkyl or
alkoxy radical which is unsubstituted or substituted by a fluorine
atom; and a silyl radical of the formula --Si--(R.sup.9).sub.3;
wherein each R.sup.9 is independently selected from a hydrogen atom
and a C.sub.1-4 alkyl radical; and
[0091] (ii) compounds of the formula
[(R.sup.8).sub.tZH]+[B(R.sup.7).sub.4].sup.- wherein B is a boron
atom, H is a hydrogen atom, Z is a nitrogen atom or phosphorus
atom, t is 2 or 3 and R.sup.8 is selected from C.sub.1-8 alkyl
radicals, a phenyl radical which is unsubstituted or substituted by
up to three C.sub.1-4 alkyl radicals, or one R.sup.8 taken together
with the nitrogen atom may form an anilinium radical and R.sup.7 is
as defined above; and compounds of the formula B(R.sup.7).sub.3
wherein R.sup.7 is as defined above.
[0092] In the above compounds in some embodiments R.sup.7 is a
pentafluorophenyl radical, and R.sup.5 is a triphenylmethyl cation,
Z is a nitrogen atom and R.sup.8 is a C.sub.1-4 alkyl radical or
R.sup.8 taken together with the nitrogen atom forms an anilinium
radical which is substituted by two C.sub.1-4 alkyl radicals.
[0093] The "ionic activator" may abstract one or more activatable
ligands so as to ionize the catalyst center into a cation but not
to covalently bond with the catalyst and to provide sufficient
distance between the catalyst and the ionizing activator to permit
a polymerizable olefin to enter the resulting active site.
[0094] Examples of ionic activators include: triethylammonium
tetra(phenyl)boron; tripropylammonium tetra(phenyl)boron;
tri(n-butyl)ammonium tetra(phenyl)boron; trimethylammonium
tetra(p-tolyl)boron; trimethylammonium tetra(o-tolyl)boron;
tributylammonium tetra(pentafluorophenyl)boron; tripropylammonium
tetra(o,p-dimethylphenyl)boron; tributylammonium
tetra(m,m-dimethylphenyl)boron; tributylammonium
tetra(p-trifluoromethylphenyl)boron; tributylammonium
tetra(pentafluorophenyl)boron; tri(n-butyl)ammonium
tetra(o-tolyl)boron; N,N-dimethylanilinium tetra(phenyl)boron;
N,N-diethylanilinium tetra(phenyl)boron; N,N-diethylanilinium
tetra(phenyl)n-butylboron, N,N-2,4,6-pentamethylanilinium
tetra(phenyl)boron; di-(isopropyl)ammonium
tetra(pentafluorophenyl)boron; dicyclohexylammonium
tetra(phenyl)boron, triphenylphosphonium tetra(phenyl)boron;
tri(methylphenyl)phosphonium tetra(phenyl)boron;
tri(dimethylphenyl)phosphonium tetra(phenyl)boron; tropillium
tetrakispentafluorophenyl borate; triphenylmethylium
tetrakispentafluorophenyl borate; benzene (diazonium)
tetrakispentafluorophenyl borate; tropillium
phenyltrispentafluorophenyl borate; triphenylmethylium
phenyltrispentafluorophenyl borate; benzene (diazonium)
phenyltrispentafluorophenyl borate; tropillium tetrakis
(2,3,5,6-tetrafluorophenyl) borate; triphenylmethylium tetrakis
(2,3,5,6-tetrafluorophenyl) borate; benzene (diazonium) tetrakis
(3,4,5-trifluorophenyl) borate; tropillium tetrakis
(3,4,5-trifluorophenyl) borate; benzene (diazonium) tetrakis
(3,4,5-trifluorophenyl) borate; tropillium tetrakis
(1,2,2-trifluoroethenyl) borate; triphenylmethylium tetrakis
(1,2,2-trifluoroethenyl) borate; benzene (diazonium) tetrakis
(1,2,2-trifluoroethenyl) borate; tropillium tetrakis
(2,3,4,5-tetrafluorophenyl) borate; triphenylmethylium tetrakis
(2,3,4,5-tetrafluorophenyl) borate; and benzene (diazonium)
tetrakis (2,3,4,5-tetrafluorophenyl) borate.
[0095] Readily commercially available ionic activators include:
N,N-dimethylaniliniumtetrakispentafluorophenyl borate;
triphenylmethylium tetrakispentafluorophenyl borate; and
trispentafluorophenyl borane.
[0096] The ionic activator may be use at about molar equivalents of
boron to group IV metal in the catalyst. Suitable molar ratios of
group IV metal from the catalyst to boron may range from 1:1 to
3:1, for example from 1:1 to 1:2.
[0097] In some instances, the ionic activator may be used in
combination with an alkylating activator (which may also serve as a
scavenger). The alkylating activator may be selected from
(R.sup.3).sub.pMgX.sub.2-p wherein X is a halide and each R.sup.3
is independently selected from C.sub.1-10 alkyl radicals and p is 1
or 2; R.sup.3Li wherein in R.sup.3 is as defined above,
(R.sup.3).sub.qZnX.sub.2-q wherein R.sup.3 is as defined above, X
is halogen and q is 1 or 2; (R.sup.3).sub.sAlX.sub.3-s wherein
R.sup.3 is as defined above, X is halogen and s is an integer from
1 to 3. For example in the above compounds R.sup.3 is a C.sub.1-4
alkyl radical, and X is chlorine. Commercially available compounds
include triethyl aluminum (TEAL), diethyl aluminum chloride (DEAC),
dibutyl magnesium ((Bu).sub.2Mg), and butyl ethyl magnesium (BuEtMg
or BuMgEt).
[0098] If the phosphinimine catalyst is activated with a
combination of ionic activators (e.g., boron compounds) and
alkylating agent the molar ratio of group IV metal from the
catalyst : metalloid (boron) from the ionic activator:metal from
the alkylating agent may range from 1:1:1 to 1:3:10, for example
from 1:1.3 : 5 to 1:1.5:3.
[0099] The resulting polymer solution is stripped of residual
monomers and pelletized. In some embodiments, during the
pelletization process conventional additives such as antioxidants,
heat and light stabilizers and process aids are added to the
polymer.
[0100] The resulting polymer may be compounded with conventional
additives including the following types:
[0101] Diphosphite
[0102] As used herein, the term diphosphite refers to a phosphite
stabilizer which contains at least two phosphorus atoms per
phosphite molecule.
[0103] Non-limiting examples of suitable diphosphites and
diphosphonites follow:
[0104] distearyl pentaerythritol diphosphite, diisodecyl
pentaerythritol diphosphite, bis(2,4 di-tert-butylphenyl)
pentaerythritol diphosphite [sold under the Trademark ULTRANOX.RTM.
626, by Chemtura Corporation]; bis(2,6-di-tert-butyl-4-methylpenyl)
pentaerythritol diphosphite; bisisodecyloxy-pentaerythritol
diphosphite, bis(2,4-di-tert-butyl-6-methylphenyl) pentaerythritol
diphosphite, bis(2,4,6-tri-tert-butylphenyl) pentaerythritol
diphosphite, and bis(2,4-dicumylphenyl)pentaerythritol diphosphite
[sold under the Trademarks DOVERPHOS.RTM. S9228-T and DOVERPHOS
S9228-CT by Dover Chemicals Corporation]. The diphosphite is used
in amounts of from 200 ppm to 2,000 ppm, for example from 300 to
1,500 ppm or for example from 400 to 1,000 ppm.
[0105] Other Additives
[0106] The compositions disclosed herein may optionally include
other additives that are conventionally used with polyethylene. A
non-limiting list follows.
[0107] Acid Neutralizers
[0108] Many commercially available polyolefins contain chloride
residues. These chloride residues may generate hydrochloric acid,
particularly during melt processing operations. Accordingly, an
"acid neutralizer" is conventionally included in a polyolefin
stabilization package and is, for example, included in the process
disclosed herein.
[0109] These acid neutralizers may be divided into
"Inorganic"--such as zinc oxide, synthetic hydrotalcites and Li,
Na, Ca or Al (hydroxy) carbonates; and "Organic"--such as salts of
fatty acids or their derivatives including calcium stearate, zinc
stearate, calcium lactate and calcium stearoyl lactylate. When
employed, these conventional acid neutralizers are used in
conventional amounts. In some embodiments a synthetic hydrotalcite
(in an amount of from 100 to 1,000 ppm), zinc stearate (in an
amount of from 200 to 700 ppm) or calcium stearoyi lactylate (in an
amount of from 200 to 700 ppm) is used. A combination of a
hydrotalcite with an "organic" acid neutralizer is an example.
[0110] HALS
[0111] Phenolic Antioxidants
[0112] Alkylated Mono-Phenols
[0113] For example, 2,6-di-tert-butyl-4-methylphenol;
2-tert-butyl-4,6-dimethylphenol; 2,6-di-tert-butyl-4-ethylphenol;
2,6-di-tert-butyl-4-n-butylphenol;
2,6-di-tert-butyl-4-isobutylphenol;
2,6-dicyclopentyl-4-methylphenol; 2-(.alpha.-methylcyclohexyl)-4,6
dimethylphenol; 2,6-di-octadecyl-4-methylphenol;
2,4,6,-tricyclohexyphenol; and
2,6-di-tert-butyl-4-methoxymethylphenol.
[0114] Alkylated Hydroquinones
[0115] For example, 2,6-di-tert-butyl-4-methoxyphenol;
2,5-di-tert-butylhydroquinone; 2,5-di-tert-amyl-hydroquinone; and
2,6diphenyl-4-octadecyloxyphenol.
[0116] Hydroxylated Thiodiphenyl Ethers
[0117] For example, 2,2'-thio-bis-(6-tert-butyl-4-methylphenol);
2,2'-thio-bis-(4-octylphenol);
4,4'-thio-bis-(6-tertbutyl-3-methylphenol); and
4,4'-thio-bis-(6-tert-butyl-2-methylphenol).
[0118] Alkylidene-Bisphenols
[0119] For example,
2,2'-methylene-bis-(6-tert-butyl-4-methylphenol);
2,2'-methylene-bis-(6-tert-butyl-4-ethylphenol);
2,2'-methylene-bis-(4-methyl-6-(alpha-methylcyclohexyl)phenol);
2,2'-methylene-bis-(4-methyl-6-cyclohexyiphenol);
2,2'-methylene-bis-(6-nonyl-4-methylphenol);
2,2'-methylene-bis-(6-nonyl-4methylphenol);
2,2'-methylene-bis-(6-(alpha-methylbenzyl)-4-nonylphenol);
2,2'-methylene-bis-(6-(alpha,
alpha-dimethylbenzyl)-4-nonyl-phenol); 2,2'-methylene-
bis-(4,6-di-tert-butylphenol);
2,2'-ethylidene-bis-(6-tert-butyl-4-isobutylphenol);
4,4'-methylene-bis-(2,6-di-tert-butylphenol);
4,4'-methylene-bis-(6-tert-butyl-2-methylphenol);
1,1-bis-(5-tert-butyl-4-hydroxy-2-methylphenol)butane
2,6-di-(3-tert-butyl-5-methyl-2-hydroxybenzyl)-4-methylphenol;
1,1,3-tris-(5-tert-butyl-4-hydroxy-2-methylphenyl)butane;
1,1-bis-(5-tert-butyl-4-hydroxy2-methylphenyl)-3-dodecyl-mercaptobutane;
ethyleneglycol-bis-(3,3,-bis-(3'-tert-butyl-4'-hydroxyphenyl)-butyrate)-d-
i-(3-tert-butyl-4-hydroxy-5-methylpenyl)-dicyclopentadiene;
di-(2-(3'-tert-butyl-2'-hydroxy-gmethylbenzyl)-6-tert-butyl-4-methylpheny-
l)terephthalate; and other phenolics such as monoacrylate esters of
bisphenols such as ethylidiene bis-2,4-di-t-butylphenol
monoacrylate ester.
[0120] Hydroxylamines and Amine Oxides
[0121] For example, N,N-dibenzylhydroxylamine;
N,N-diethylhydroxylamine; N,N-dioctylhydroxylamine;
N,N-dilaurylhydroxylamine; N,N-ditetradecylhydroxylamine;
N,N-dihexadecylhydroxylamine; N,N-dioctadecylhydroxylamine;
N-hexadecyl-N-octadecylhyd roxylam nine;
N-heptadecyl-N-octadecylhydroxylamine; and N,
N-dialkylhydroxylamine derived from hydrogenated tallow amine. The
analogous amine oxides (as disclosed in U.S. Pat. No. 5,844,029,
Prachu et al.) may also be employed.
[0122] Care needs to be taken when adding fillers to the
polyethylene as these may cause warpage of the molded part.
[0123] The polyethylene is for example ground into a fine powder
having a size from about 500 to 1000 microns. The powder may be
used as is or additional heat and light stabilizers and pigments
may be added to the polyethylene.
[0124] The powder is loaded into a mold, in some embodiments with a
release aid. The mold is rotated about two axes of rotation to
cause the particles to flow over the entire inner surface of the
mold. The particles are heated to a sintering temperature and fuse
together and form a continuous surface. The mold is then cooled and
opened and the formed part is removed.
[0125] The present disclosure will now be illustrated by the
following examples.
EXAMPLES
[0126] Test Methods
[0127] Mn, Mw and Mz (g/mol) were determined by high temperature
Gel Permeation Chromatography (GPC) with differential refractive
index detection using universal calibration (e.g. ASTM-D646-99).
The molecular weight distribution (MWD) is the ratio of the weight
average molecular weight (Mw) over the number average molecular
weight (Mn).
[0128] GPC-FTIR was used to determine the comonomer content as a
function of molecular weight. After separation of the polymer by
GPC an on-line FTIR measures the concentration of the polymer and
methyl end groups. Methyl end groups are used in the branch
frequency calculations. Conventional calibration allows for the
calculation of a molecular weight distribution.
[0129] Mathematical deconvolutions were performed to determine the
relative amount of polymer, molecular weight, and comonomer content
of the component made in each reactor, by assuming that each
polymer component follows a Flory's molecular weight distribution
function and it has a homogeneous comonomer distribution across the
whole molecular weight range. The uniform comonomer distribution of
each resin component, which is the result from the use of a single
site catalyst, allowed the estimation of the short chain branching
content (SCB), in branches per 1000 carbon atoms for the first and
second ethylene polymers, based on the deconvoluted relative
amounts of first and second ethylene polymer components in the
polyethylene composition, and their estimated resin molecular
weight parameters from the above procedure.
[0130] The short chain branch frequency (SCB per 1000 carbon atoms)
of copolymer samples was determined by Fourier Transform Infrared
Spectroscopy (FTIR) as per ASTM D6645-01. A Thermo-Nicolet 750
Magna-IR Spectrophotometer was used for the measurement. FTIR was
also used to determine internal, side chain and terminal levels of
unsaturation.
[0131] Comonomer content can also be measured using 13C NMR
techniques as discussed in Randall Rev. Macromol. Chem. Phys., C29
(2&3), p.285; U.S. Pat. No. 5,292,845 and WO 2005/121239.
[0132] Polyethylene composition density (g/cm.sup.3) was measured
according to ASTM D792.
[0133] Melt indexes 12 and 121 for the polyethylene composition
were measured according to ASTM D1238.
[0134] The density and melt index of the first and second ethylene
polymers that comprise the polyethylene composition were determined
based on composition models. The following equations were used to
calculate the density and melt index 12 (REFERENCE U.S. Pat. No.
8,022,143 B2, by Wang, assigned to NOVA Chemicals and published
Sep. 20, 2011):
Density = 0.979863 - 5.95808 .times. 10 - 3 ( SCB 1000 C ) 0.65 -
3.8133 .times. 10 - 4 [ log 10 ( M n ) ] 3 - 5.77986 .times. 10 - 6
( M w / M n ) 3 + 5.57395 .times. 10 - 3 ( M z / M w ) 0.25
##EQU00005## log 10 ( Melt Index I 2 ) = 22.326528 + 3.467 .times.
10 - 3 [ log 10 ( M n ) ] 3 - 4.322582 [ log 10 ( M w ) ] - 1.80061
.times. 10 - 1 [ log 10 ( M z ) ] 2 + 2.6478 .times. 10 - 2 [ log
10 ( M z ) ] 3 ##EQU00005.2##
where Mn, Mw, Mz, and SCB/1000C are the deconvoluted values of the
individual ethylene polymer components, as obtained from the
results of the deconvolution described above.
[0135] Plaques molded from the polyethylene compositions were
tested according to the following ASTM methods: Bent Strip
Environmental Stress Crack Resistance (ESCR), ASTM D1693; Flexural
properties, ASTM D 790; Tensile properties, ASTM D 638.
[0136] Rotomolded parts were prepared in a rotational molding
machine sold under the tradename Rotospeed RS3-160 by Ferry
Industries Inc. The machine has two arms which rotate about a
central axis within an enclosed oven. The arms are fitted with
plates which rotate on an axis that is roughly perpendicular to the
axis of rotation of the arm. Each arm is fitted with six cast
aluminum molds that produce plastic cubes having dimensions of 12.5
inches (31.8 cm).times.12.5 inches.times.12.5 inches. The arm
rotation was set to about 8 revolutions per minute (rpm) and the
plate rotation was set to about 2 rpm. These molds produce parts
having a nominal thickness of about 0.25 inches (0.64 cm) when
initially filled with a standard charge of about 3.7 kg of
polyethylene resin in powder form (35 US mesh size). The
temperature within the enclosed oven was maintained at a
temperature of 560.degree. C. The molds and their content were
heated for specified period of time. The molds were subsequently
cooled in a controlled environment prior to removing the parts.
Specimens were collected from the molded parts for density
measurements (density as is) and for determining the color rating
and whiteness index (color as is). The ARM impact test was
performed in accordance with ASTM D5628 at a test temperature of
-40.degree. C.
[0137] The Resin
[0138] Bimodal polyethylene compositions were prepared at a dual
reactor pilot plant. In this dual reactor process the content of
the first reactor flows into the second reactor, both of which are
well mixed. The process operates using continuous feed streams. The
catalyst (cyclopentadienyl Ti tri tert.butly phosphimine di
chloride) with catalyst was fed to both reactors. The overall
production rate was about 90 kg/hr.
[0139] The polymer compositions prepared at the pilot plant were
stabilized by a conventional additive package prior to carrying out
plaque testing and rotomolding trials.
[0140] The polymerization conditions are provided in Table 1. The
resulting polyethylene compositions are described in Table 2. The
properties of the resulting resins are compared to two commercially
available rotomolding resins which are referred to as comparative
example 1 and 2, respectively. Properties for the first ethylene
polymer and the second ethylene polymer were estimated from
deconvolution studies carried out on results obtained from GPC and
GPC-FTIR. Results are set forth in Table 3. The properties of
pressed plaques as well as rotomolded parts made from the
polyethylene compositions are provided in Table 4.
TABLE-US-00001 TABLE 1 Invention Invention Invention Comparative
Example 1 Example 2 Example 3 Example 3 Ethylene split between
first reactor (R1), second 0.31/0.49/ 0.35/0.45/ 0.35/0.65/0
0.35/0.65/0 reactor (R2), and third reactor (R3) 0.20 0.20 Octene
split between first Reactor (R1) and 1/0/0 1/0/0 1/0/0 1/0/0 second
reactor (R2), and third reactor (R3) Octene to ethylene ratio in
fresh feed 0.023 0.025 0.021 0.028 Hydrogen in reactor 1 (ppm) 0.5
0.6 0.8 1.2 Hydrogen in reactor 2 (ppm) 8.0 11.6 4.5 6.0 Hydrogen
in reactor 3 (ppm) 0.5 0.6 -- -- Reactor 1 temperature (.degree.
C.) 143 150 143 144 Reactor 2 temperature (.degree. C.) 170 170 208
211 Reactor 3 temperature (.degree. C.) 184 188 -- -- Catalyst feed
in reactor 1 (ppm) 0.11 0.09 0.10 0.10 Catalyst feed in reactor 2
(ppm) 0.08 0.13 0.22 0.38 Catalyst feed in reactor 3 (ppm) 0.00
0.00 -- --
TABLE-US-00002 TABLE 2 Invention Invention Invention Comparative
Comparative Comparative Example 1 Example 2 Example 3 Example 1
Example 2 Example 3 Density (g/cm.sup.3) 0.9500 0.9507 0.9480
0.9537 0.9449 0.9483 Melt Index I.sub.2 (g/10 min) 1.1 1.1 1.2 1.6
1.7 2.0 Melt Index I.sub.21 (g/10 min) 4.9 5.2 5.3 7 7.5 8.7 9.3
10.1 15.2 40.0 49.1 38.9 79.0 65.8 64.6 Melt Flow Ratio
(I.sub.21/I.sub.2) 36.4 44.6 32.4 49.4 39.9 32.1 Branch Freq/1000 C
1.0 1.3 1.2 1.9 2.7 1.9 Comonomer ID octene octene octene octene
octene octene Comonomer Content 0.8 1.0 0.9 1.5 2.1 1.5 (wt %)
Internal Unsat/1000 C 0.03 0.03 0.11 0.06 0.12 0.14 Total
Unsat/1000 C 0.08 0.07 0.19 0.15 0.20 0.25 M.sub.n 32000 26000
35000 16700 28500 27000 M.sub.w 111000 105000 102000 89000 89500
86000 M.sub.z 323000 303000 264000 257000 250000 221500
Polydispersity Index 3.5 4.0 2.9 5.3 3.1 3.2 (M.sub.w/M.sub.n)
Index (Mz/Mw) 2.9 2.9 2.6 2.9 2.8 2.6 CDBI-50: 91.5 85.1 92.6 60.6
88.2 87.6 PSP2 (based on Branch 4.5 4.6 4.5 5.0 6.2 4.1 Content)
PSP2 (based on Branch 3.6 3.1 2.8 3.2 Content)
TABLE-US-00003 TABLE 3 Invention Invention Invention Comparative
example 1 example 2 example 3 example 3 FIRST ETHYLENE POLYMER
(Deconvolution Studies) M.sub.n 118000 101600 111200 83500 M.sub.w
236000 203200 222400 167000 Weight fraction (%) 28% 37% 29% 33%
M.sub.z 472000 406400 444800 334000 Branch Freq/1000 C (SCB1) 1.7
1.7 2.0 2.3 Density estimate (g/cm.sup.3) (d1) 0.922 0.924 0.922
0.924 SECOND ETHYLENE POLYMER (Deconvolution Studies) M.sub.n 17000
13800 23700 19700 M.sub.w 34000 27600 47400 39400 Weight fraction
(%) 56% 58% 71% 67% M.sub.z 51000 41400 71100 59100 Branch
Freq/1000 C (SCB2) 0 0 0 0 Density estimate (g/cm.sup.3) (d2) 0.951
0.953 0.948 0.950 Estimated d2 - d1 (g/cm.sup.3) 0.029 0.029 0.026
0.025 THIRD ETHYLENE POLYMER (Deconvolution Studies) M.sub.n 54000
41000 M.sub.w 108000 82000 Weight fraction (%) 16% 5% 0 0 M.sub.z
162000 123000 Branch Freq/1000 C (SCB2) 0 0 Density estimate
(g/cm.sup.3) (d3) 0.939 0.942
TABLE-US-00004 TABLE 4 Invention Invention Invention Comp. Comp.
Comp. example example example example example example 1 2 3 1 2 3
FLEXURAL PROPERTIES (Plaques) Flex Secant Mod. 1% (MPa) 1233 1292
1202 1336 1005 1057 Flex Sec Mod 1% (MPa) Dev. 33 39 24 28 20 25
ESCR (Plaques) ESCR Cond. A at 100% (hrs) 331 229 120 -- >1000
80 100% CO-630 ESCR Cond. B at 100 % (hrs) 357 217 112 21 >1000
141 100% CO-630 Low Temperature (-40.degree. C.) ARM Impact
Performance Mean Failure Energy (ft.lb) at 150 170 185 0 188 185
optimal conditions Ductility (%) at optimal 90 100 92 0 100 100
conditions As is density (g/cm.sup.3) at optimal 0.9496 0.9539
0.952 0.955 0.9464 0.9488 conditions Appearance Flat Flat Flat
Warpage Flat Flat surfaces surfaces surfaces surfaces surfaces
* * * * *