U.S. patent application number 12/113265 was filed with the patent office on 2008-11-20 for low density oriented polymer composition with inert inorganic filler.
Invention is credited to Brett M. Birchmeier, Phil Caton-Rose, Philip D. Coates, Kevin L. Nichols, Rajen M. Patel, Glen P. Thompson, Vijay Wani, Ian M. Ward.
Application Number | 20080287576 12/113265 |
Document ID | / |
Family ID | 40028153 |
Filed Date | 2008-11-20 |
United States Patent
Application |
20080287576 |
Kind Code |
A1 |
Nichols; Kevin L. ; et
al. |
November 20, 2008 |
LOW DENSITY ORIENTED POLYMER COMPOSITION WITH INERT INORGANIC
FILLER
Abstract
An oriented polymer composition containing thirty to 95
weight-percent inert inorganic filler and a continuous phase of at
least one orientable polymer contains void spaces due to cavitation
and has a density of less than 0.8 grams per cubic centimeter, a
flexural modulus of 1.4 gigapascals or more, cross section
dimensions all greater than 1.5 millimeters, a delamination force
value of 44.5 Newtons (ten pounds force) or more and little or no
blowing agent.
Inventors: |
Nichols; Kevin L.;
(Freeland, MI) ; Birchmeier; Brett M.; (Midland,
MI) ; Ward; Ian M.; (Leeds, GB) ; Coates;
Philip D.; (Leeds, GB) ; Caton-Rose; Phil;
(Bradford, GB) ; Thompson; Glen P.; (Bradford,
GB) ; Wani; Vijay; (Lake Jackson, TX) ; Patel;
Rajen M.; (Lake Jackson, TX) |
Correspondence
Address: |
The Dow Chemical Company
Intellectual Property Section, P.O. Box 1967
Midland
MI
48641-1967
US
|
Family ID: |
40028153 |
Appl. No.: |
12/113265 |
Filed: |
May 1, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60930145 |
May 14, 2007 |
|
|
|
Current U.S.
Class: |
524/65 ; 524/427;
524/442; 524/451 |
Current CPC
Class: |
C08K 3/26 20130101; C08K
2003/265 20130101; C08K 3/22 20130101; B29C 70/58 20130101; B29K
2105/16 20130101; C08K 3/34 20130101; B29C 55/005 20130101; B29K
2105/04 20130101; C08K 3/346 20130101 |
Class at
Publication: |
524/65 ; 524/451;
524/427; 524/442 |
International
Class: |
C08K 3/34 20060101
C08K003/34; C08K 3/26 20060101 C08K003/26 |
Claims
1. An oriented polymer composition comprising thirty weight-percent
or more and 95 weight-percent or less inert inorganic filler based
on oriented polymer composition weight and a continuous phase of at
least one orientable polymer, wherein the oriented polymer
composition has: (a) a density of less than 0.8 grams per cubic
centimeter according to ASTM method 792-00; (b) a flexural modulus
of 1.4 gigapascals (200,000 pounds per square inch) or more
according to ASTM method D-790-03; (c) cross section dimensions all
greater than 1.5 millimeters; (d) a delamination force value
greater than 44.5 Newtons (ten pounds force); and wherein the
oriented polymer composition contains less than three
weight-percent blowing agent based on oriented polymer composition
weight.
2. The oriented polymer composition of claim 1, wherein the filler
is selected from a group consisting of talc, calcium carbonate,
clay and fly ash.
3. The oriented polymer composition of claim 1, wherein the
orientable polymer is one or more than one semi-crystalline
polymer.
4. The oriented polymer composition of claim 1, wherein the
orientable polymer is selected from polypropylene-based polymers,
polyethylene-based polymers, polyvinyl chloride, polyesters and
polyester-based polymers.
5. The oriented polymer composition of claim 1, wherein the
oriented polymer composition is free of blowing agent.
6. A process for solid state drawing a polymer composition
comprising the steps: (a) providing a polymer composition
comprising thirty weight-percent or more and 95 weight-percent or
less of an inert inorganic filler based on polymer composition
weight and a continuous phase of at least one orientable polymer,
the polymer composition having a melt temperature; (b) conditioning
the temperature of the polymer composition to a drawing temperature
that is ten degrees Celsius or more below the polymer composition's
softening temperature; (c) drawing the polymer composition though a
drawing die at a drawing rate of at least 0.25 meters per minute;
and (d) optionally, cooling the polymer composition after it exits
the drawing die; wherein the polymer composition comprises less
than three weight-percent blowing agent based on polymer
composition weight.
7. The process of claim 6, wherein drawing in step (c) achieves a
linear draw ratio of 10 or less.
8. The process of claim 6, wherein the orientable polymer is one or
more than one semi-crystalline polymer.
9. The process of claim 6, wherein the orientable polymer is
selected from polypropylene-based polymers, polyethylene-based
polymers, polyvinyl chloride and polyester-based polymers.
10. The process of claim 6, wherein the draw rate is 0.5 meters per
minute or faster.
11. The process of claim 6, wherein the draw rate is one meter per
minute or faster.
12. The process of claim 6, wherein the drawing temperature is at
least fifteen degrees Celsius below the polymer composition's
softening temperature.
13. The process of claim 6, wherein the drawing temperature is at
least twenty degrees Celsius below the polymer composition's
softening temperature.
14. The process of claim 6, wherein the draw temperature is forty
degrees Celsius or less below the polymer composition's softening
temperature.
15. The process of claim 6, wherein the filler is selected from
talc, clay, calcium carbonate and fly ash.
16. The process of claim 6, wherein the filler is present at a
concentration of 40 percent by weight or more relative to polymer
composition weight before drawing.
17. The process of claim 6, wherein the polymer composition
experiences a nominal draw ratio of 1.25 or more and less than
five.
18. The process of claim 6, wherein drawing is done through a
drawing die that induces proportional drawing of the polymer
composition.
19. The process of claim 6, wherein the polymer composition is free
of blowing agent.
Description
[0001] This application claims benefit of U.S. Provisional
Application No. 60/930,145, filed on May 14, 2007.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to solid state drawing
processes and oriented polymer compositions produced by solid state
drawing processes.
[0004] 2. Description of Related Art
[0005] Oriented polymer compositions are desirable for having
higher strength and stiffness over non-oriented polymer
compositions. Historically, polymeric films and fibers have enjoyed
the benefits of orientation through drawing processes. However,
when a polymer cross section becomes larger than that of a film or
fiber, drawing to a controlled and consistent shape becomes more
complex and new drawing processes are necessary.
[0006] Great Britain (GB) patent 1311885 discloses a solid state
die drawing process to address the challenges of orienting larger
cross section polymer compositions, which the patent identifies as
compositions having a cross-sectional area of 0.01 square inches
(6.45 square millimeters) or more or with all cross sectional
dimensions greater than 0.05 inches (1.27 millimeters). The solid
state die drawing process requires drawing a polymer composition
billet through a lubricated drawing die in the polymer
composition's solid phase at a temperature below the polymer
composition's melting temperature (T.sub.m). The drawing die forces
the polymer composition to converge towards a specific shape,
causing alignment of polymer chains. According to GB1311885, one of
the challenges with large cross section billets is bringing the
entire cross section to a uniform temperature prior to drawing in
order to allow control of the extrusion velocity of the billet into
the drawing die. Small cross section articles such as films and
fibers do not present such a challenge.
[0007] Orientation of filled polymer compositions is of particular
interest. Filler offers numerous benefits, perhaps the most
recognized is reduction in raw material cost for the polymer
composition. Use of wood fiber fillers in oriented polymer
compositions has been of particular interest for fabricating
oriented polymer compositions that serve as an alternative to wood
decking materials (that is, composite decking). Organic fillers,
however, are subject to handicaps including color bleaching when
exposed to the sun, and to decomposition, mold and mildew when
exposed to humidity even within a polymer composition. Inorganic
fillers are attractive because they are not subject to these
handicaps. However, inorganic fillers tend to have a higher density
than organic fillers. Additionally, reactive inorganic fillers such
as Portland cement and gypsum are reactive with water (see, for
example, PCT publication WO 2004/009334), which can result in an
unstable polymer composition density in humid environments.
[0008] Incorporating void volume in a filled oriented polymer
composition reduces the composition's density. U.S. Pat. No.
5,474,722 ('722) discloses use of blowing agents with organic and
mica fillers (see Examples 3 and 9 in '722) in order to reduce the
density of an oriented polymer composition. Blowing agents expand
to foam the polymer composition in order to establish void volume.
Foamed compositions contain blowing agent. Foaming requires a
foaming step and control of foaming agent in the process.
[0009] Cavitation is a desirable alternative for reducing an
oriented polymer composition density without the use of a blowing
agent. Cavitation induces void volume proximate to filler particles
while drawing a polymer composition containing the filler
particles. For example, European Patent 1242220B1 provides an
example a polypropylene composition filled with wood filler
(composition density of about one gram per cubic centimeter
(g/cm.sup.3)) that is drawn at a drawing rate of 48 inches (122
centimeters) per minute to obtain an oriented polymer composition
having a density of 0.59 g/cm.sup.3 centimeter. Drawing
compositions containing up to 22 weight-percent of mica filler in
polypropylene also reveal void volumes from cavitation of up to
28.5% and densities down to 0.76 g/cm.sup.3. (W. R. Newson and F.
R. Maine, ORIENTED POLYPROPYLENE COMPOSITIONS MADE WITH MICA,
handout from 8.sup.th International Conference on Woodfiber-Plastic
Composites, Madison, Wis., May 23-25, 2005).
[0010] PCT publication WO 2004/009334 ('334) discloses cavitation
during orientation of polymer filled with reactive inorganic
fillers such as Portland cement. '334 discloses both die drawn and
free draw processes. The lowest density '334 reveals for a die
drawn oriented polymer composition is 0.82 g/cm.sup.3. Lower
densities are reported for free drawn compositions by using a
linear draw ratio of greater than eleven. However, free drawn
oriented compositions having such a large linear draw ratio
(greater than eleven) tend to suffer from a low delamination force.
That is, they delaminate or fibrillate more easily along the
drawing direction than free drawn compositions having a lower
linear draw ratio, as well as die drawn compositions. Moreover, a
free draw process offers little control over the dimension of a
final drawn article as compared to die drawn processes.
[0011] Using filler in an oriented polymer composition is desirable
both to reduce the cost of a polymer composition and also to
promote cavitation. Both of these features are attractive for
preparing oriented polymer compositions that can serve as
alternatives to wood in structural applications such as composite
decking where cost and weight are both important. Desirably,
oriented polymer compositions in such structural applications are
free of handicaps associated with organic fillers, density and
composition instability in the presence of humidity that reactive
inorganic fillers are subject to, high densities associated with
inorganic filler and a low delamination force with high linear draw
ratios.
[0012] An oriented polymer composition containing a large amount
(thirty weight-percent or more based on polymer composition weight)
of inert inorganic filler that has a density comparable to or less
than wood (that is, less than 0.8 g/cm.sup.3) and strength and
stiffness sufficient to meet building codes for use in structural
applications is desirable. It is further of interest to have such
an oriented polymer composition that is essentially free or
completely free of blowing agent. It is still further desirable for
such an oriented polymer composition to have a delamination force
of at least 44.5 Newtons (ten pounds force) to resist delamination
and fibrillation during use.
[0013] Measure the density of a polymer composition according to
American Society for Testing and Materials (ASTM) method
D-792-00.
BRIEF SUMMARY OF THE INVENTION
[0014] Experimentation leading to the present invention
surprisingly revealed that solid state drawing a polymer
composition containing thirty weight-percent or more (based on
polymer composition weight) of inert inorganic filler can result in
cavitation within the polymer composition sufficient to achieve an
oriented polymer composition having a density comparable to or less
than wood (that is, less than 0.8 grams per cubic centimeter) and a
modulus sufficient to meet building codes without requiring a
blowing agent or a linear draw ratio of eleven. As a result,
articles of the present invention surprisingly enjoy combined
benefits of high concentrations of filler (30 wt % or more by
weight of polymer), low density (less than 0.8 g/cm.sup.3), high
flexural modulus (1.4 gigapascals or more) and high delamination
force values (44.5 Newtons (N) or more; 10 pounds force or more)
typically absent from compositions having a linear draw ratio
greater than eleven while also being virtually, even completely
free of blowing agent.
[0015] In a first aspect, the present invention is an oriented
polymer composition comprising thirty weight-percent or more and 95
weight-percent or less inert inorganic filler based on oriented
polymer composition weight and a continuous phase of at least one
orientable polymer, wherein the oriented polymer composition has:
(a) a density of less than 0.8 grams per cubic centimeter according
to American Society for Testing and Materials (ASTM) method 792-00;
(b) a flexural modulus of 1.4 gigapascals (200,000 pounds per
square inch) or more according to ASTM method D-790-03; (c) cross
section dimensions all greater than 1.5 millimeters; (d) a
delamination force value greater than 44.5 Newtons (ten pounds
force); and wherein the oriented polymer composition contains less
than three weight-percent blowing agent based on oriented polymer
composition weight.
[0016] Preferred embodiments of the first aspect include any one or
combination of more than one of the following characteristics: the
filler is selected from a group consisting of talc (including any
individual or combination of materials and grades of materials
commonly known as or available as "talc"), calcium carbonate, clay
and fly ash; the orientable polymer is a polyolefin; and the
orientable polymer is selected from polypropylene-based polymers,
polyethylene-based polymers and polyvinyl chloride; the oriented
polymer composition is free of blowing agent.
[0017] In a second aspect, the present invention is a process for
solid state drawing a polymer composition comprising: (a) providing
a polymer composition comprising thirty weight-percent or more and
95 weight-percent or less of an inert inorganic filler based on
polymer composition weight and a continuous phase of at least one
orientable polymer, the polymer composition having a softening
temperature; (b) conditioning the temperature of the polymer
composition to a drawing temperature that is ten degrees Celsius or
more below the polymer composition's softening temperature; (c)
drawing the polymer composition though a drawing die at a drawing
rate of at least 0.25 meters per minute to achieve a linear draw
ratio of ten or less; and (d) optionally cooling the polymer
composition after exiting the drawing die; wherein the polymer
composition comprises less than three weight-percent blowing agent
based on polymer composition weight.
[0018] Preferred embodiments of the second aspect include any one
or combination of more than one of the following characteristics:
the orientable polymer is a polyolefin; the orientable polymer is
selected from polypropylene-based polymers, polyethylene-based
polymers and polyvinyl chloride; the draw rate is 0.5 meters per
minute or faster; the draw rate is one meter per minute or faster;
the drawing temperature is at least fifteen degrees Celsius below
the polymer composition's softening temperature; the drawing
temperature is at least twenty degrees Celsius below the polymer
composition's softening temperature; the draw temperature is forty
degrees Celsius or less below the polymer composition's softening
temperature; the filler is selected from talc, calcium carbonate
and fly ash; the filler is present at a concentration of 40 percent
by weight or more relative to polymer composition weight before
drawing; the polymer composition experiences a nominal draw ratio
of 1.25 or more and less than five; drawing is done through a
drawing die that induces proportional drawing of the polymer
composition; and the polymer composition is free of blowing
agent.
DETAILED DESCRIPTION OF THE INVENTION
Terms
[0019] "Solid state" refers to a polymer (or polymer composition)
that is below the softening temperature of the polymer (or polymer
composition). Hence, "solid state drawing" refers to drawing a
polymer or polymer composition that is below the softening
temperature of the polymer (or polymer composition).
[0020] "Polymer composition" comprises at least one polymer
component and can contain non-polymeric components.
[0021] "Softening temperature" (T.sub.s) for a polymer or polymer
composition having as polymer components only one or more than one
semi-crystalline polymer is the melting temperature for the polymer
composition.
[0022] "Melting temperature" (T.sub.m) for a semi-crystalline
polymer is the temperature half-way through a crystalline-to-melt
phase change as determined by differential scanning calorimetry
(DSC) upon heating a crystallized polymer at a specific heating
rate. Determine T.sub.m for a semi-crystalline polymer according to
the DSC procedure in ASTM method E794-06. Determine T.sub.m for a
combination of polymers and for a filled polymer composition also
by DSC under the same test conditions in ASTM method E794-06. If
the combination of polymers or filled polymer composition only
contains miscible polymers and only one crystalline-to-melt phase
change is evident in the a DSC curve, then T.sub.m for the polymer
combination or filled polymer composition is the temperature
half-way through the phase change. If multiple crystalline-to-melt
phase changes are evident in a DSC curve due to the presence of
immiscible polymers, then T.sub.m for the polymer combination or
filled polymer composition is the T.sub.m of the continuous phase
polymer. If more than one polymer is continuous and they are not
miscible, then the T.sub.m for the polymer combination or filled
polymer composition is the highest T.sub.m of the continuous phase
polymers.
[0023] "Softening temperature" (T.sub.s) for a polymer or polymer
composition having as polymer components only one or more than one
amorphous polymer is the glass transition temperature for the
polymer composition.
[0024] "Glass transition temperature" (T.sub.g) for a polymer or
polymer composition is the temperature half-way through a glass
transition phase change as determined by DSC according to the
procedure in ASTM method D3418-03. Determine T.sub.g for a
combination of polymers and for a filled polymer composition also
by DSC under the same test conditions in D3418-03. If the
combination of polymer or filled polymer composition only contains
miscible polymers and only one glass transition phase change is
evident in the DSC curve, then T.sub.g of the polymer combination
or filled polymer composition is the temperature half-way through
the phase change. If multiple glass transition phase changes are
evident in a DSC curve due to the presence of immiscible amorphous
polymers, then T.sub.g for the polymer combination or filled
polymer composition is the T.sub.g of the continuous phase polymer.
If more than one amorphous polymer is continuous and they are not
miscible, then the T.sub.g for the polymer composition or filled
polymer composition is the highest T.sub.g of the continuous phase
polymers.
[0025] If the polymer composition contains a combination of
semi-crystalline and amorphous polymers, the softening temperature
of the polymer composition is the softening temperature of the
continuous phase polymer or polymer composition.
[0026] "Drawing axis" for a die is a straight line extending in the
direction that the center of mass (centroid) of a polymer
composition is moving as the polymer composition is drawn.
[0027] "Cross sections" herein are perpendicular to the drawing
axis unless the reference to the cross section indicates otherwise.
A cross section has a centroid and has a perimeter that defines a
shape for the cross section.
[0028] A "cross section dimension" is the length of a straight line
connecting two points on a cross section's perimeter and extending
through the centroid of the cross section. For example, a cross
section dimension of a rectilinear four-sided polymer composition
could be the height or width of the polymer composition.
[0029] An artisan understands that a polymer composition typically
has a variation in temperature through its cross section (that is,
along a cross sectional dimension of the composition) during
processing. Therefore, reference to temperature of a polymer
composition refers to an average of the highest and lowest
temperature along a cross sectional dimension of the polymer
composition. The temperature at two different points along the
polymer cross sectional dimension desirably differs by 10% or less,
preferably 5% or less, more preferably 1% or less, most preferably
by 0% from the average temperature of the highest and lowest
temperature along the cross sectional dimension. Measure the
temperature in degrees Celsius (.degree. C.) along a cross
sectional dimension by inserting thermocouples to different points
along the cross sectional dimension.
[0030] "Drawing temperature" refers to the temperature of the
polymer composition as it begins to undergo drawing in a solid
state drawing die.
[0031] "Linear Draw Ratio" is a measure of how much a polymer
composition elongates in a drawing direction (direction the
composition is drawn) during a drawing process. Determine linear
draw ratio while processing by marking two points on a polymer
composition spaced apart by a pre-orientated composition spacing.
Measure how far apart those two points are after drawing to get an
oriented composition spacing. The ratio of final spacing to initial
spacing identifies the linear draw ratio.
[0032] "Nominal draw ratio" is the cross sectional surface area of
a polymer composition prior as it enters a drawing die divided by
the polymer cross sectional area as it exits the drawing die.
[0033] "Delamination Force" is a measure of the force needed to
delaminate a portion of a polymer composition along the
composition's extrusion direction. Measure delamination force for a
polymer composition by means of a delamination test as applied to a
"test sample" taken from the polymer composition.
[0034] A "test sample" is a portion of polymer composition taken
from the center of a polymer composition (that is, the centroid of
any cross section of the test sample corresponds to a centroid of a
cross section of the polymer composition containing the cross
section of the test sample). The test sample has a length (drawing
dimension orientation) of 2 centimeters (cm) to 10 cm, width
(dimension perpendicular to length) in a range of 8 mm to 12 mm,
and uniform thickness (dimension mutually perpendicular to length
and width) in a range of 1.25 mm to 4 mm. Use a sharp razor to
slice as narrow of a notch as possible in a plane containing the
length and thickness dimensions, centered in the width dimension
and extending to a notch length that is 5 to 12 mm in the length
dimension of the sample. The two tabs on either side of the notch
that extend in the length dimension and that have equal widths of
oriented polymer composition on either side of the notch.
[0035] Conduct the delamination test after conditioning the test
sample to 23.degree. C. and 50% relative humidity by pulling the
tabs apart at a rate of 0.2 inches per minute in the width
dimension of the test sample (perpendicular to the plane of the
notch). Grip each tab proximate to an end of the test sample such
that the distance from the center of the grip to the end of the
notch interior to the test sample defines a notch length. Measure
the force applied to the tabs until the tabs disconnect from one
another into distinct pieces. The maximum force measured prior to
disconnecting the tabs is the "peak force". Determine the
Delamination Force (DF) for the test sample according to the
following equation:
DF=(Peak Force)(notch length)/(Test Sample Thickness)
[0036] The more force that is required to completely delaminate the
tabs, the greater the delamination force value and structural
integrity for the polymer composition.
[0037] Measure the density of a polymer composition according to
American Society for Testing and Materials (ASTM) method
D-792-00.
Oriented Polymer Composition
[0038] The present invention, in one aspect, is an oriented polymer
composition. An oriented polymer composition comprises polymer
molecules that have a higher degree of molecular orientation than
that of a polymer composition extruded from a mixer. Typically, an
oriented polymer composition requires a specific processing step
designed for the purpose of orienting the polymer composition (for
example, solid state drawing or ram extruding through a converging
die) in order to convert a polymer composition to an oriented
polymer composition.
[0039] The oriented polymer composition of the present invention
comprises a continuous phase of one or more orientable polymers.
Typically, 90 weight-percent (wt %) or more, more typically, 95 wt
% or more of the polymers in the polymer composition are orientable
polymers. All of the polymer in the polymer composition can be
orientable. Measure wt % based on total polymer weight in the
oriented polymer composition. All of the polymers in the oriented
polymer composition can be orientable polymers.
[0040] An orientable polymer is a polymer that can undergo polymer
alignment. Orientable polymers can be amorphous or
semi-crystalline. Herein, "semi-crystalline" and "crystalline"
polymers interchangeably refer to polymers having a melt
temperature (T.sub.m). Desirable orientable polymers are one or
more than one semi-crystalline polymer, particularly polyolefin
polymers (polyolefins). Polyolefins tend to readily undergo
cavitation in combination with filler particles presumably because
polyolefins are relatively non-polar and as such adhere less
readily to filler particles. Linear polymers (that is, polymers in
which chain branching occurs in less than 1 of 1,000 monomer units
such as linear low density polyethylene) are even more
desirable.
[0041] Suitable orientable polymers include polymers and copolymers
based on polystyrene, polycarbonate, polypropylene, polyethylene
(for example, high density, very high density and ultra high
density polyethylene), polyvinyl chloride, polymethylpentane,
polytetrafluoroethylene, polyamides, polyesters (for example,
polyethylene terephthalate) and polyester-based polymers,
polycarbonates, polyethylene oxide, polyoxymethylene,
polyvinylidine fluoride and liquid crystal polymers and
combinations thereof. A first polymer is "based on" a second
polymer if the first polymer comprises the second polymer. For
example, a block copolymer is based on the polymers comprising the
blocks. Particularly desirably orientable polymers include polymers
based on polyethylene, polypropylene, and polyesters. More
particularly desirable orientable polymers include linear
polyethylene having a Mw from 50,000 to 3,000,000 g/mol; especially
from 100,000 to 1,500,000 g/mol, even from 750,000 to 1,500,000
g/mol.
[0042] A preferred class of polyesters (and polyester-based
polymers) is those which are derivable from the reaction of at
least one polyhydric alcohol, suitably a linear polyhydric alcohol,
preferably a diol such as linear C.sub.2 to C.sub.6 diol with at
least one polybasic acid, suitably a polycarboxylic acid. Examples
of suitable polyesters include polyethylene 2,6-naphthalate,
polyethylene 1,5-naphthalate, polytetramethylene
1,2-dihydroxybenzoate, polyethylene terephthalate, polybutylene
terephthalate and copolyesters, especially of ethylene
terphthalate.
[0043] Polypropylene (PP)-based polymers (that is, polymers based
on PP) are one example of desirable orientable polymers for use in
the present invention. PP-based polymers generally have a lower
density than other orientable polyolefin polymers. Therefore,
PP-based polymers facilitate lighter articles than other orientable
polyolefin polymers. PP-based polymers also offer greater thermal
stability than other orientable polyolefin polymers. Therefore,
PP-based polymers may also form oriented articles having higher
thermal stability than oriented articles of other polyolefin
polymers.
[0044] Suitable PP-based polymers include Zeigler Natta,
metallocene and post-metallocene prolypropylenes. Suitable PP-based
polymers include PP homopolymer; PP random copolymer (with ethylene
or other alpha-olefin present from 0.1 to 15 percent by weight of
monomers); PP impact copolymers with either PP homopolymer or PP
random copolymer matrix of 50 to 97 percent by weight (wt %) based
on impact copolymer weight and with ethylene propylene copolymer
rubber present at 3 to 50 wt % based on impact copolymer weight
prepared in-reactor or an impact modifier or random copolymer
rubber prepared by copolymerization of two or more alpha olefins
prepared in-reactor; PP impact copolymer with either a PP
homopolymer or PP random copolymer matrix for 50 to 97 wt % of the
impact copolymer weight and with ethylene-propylene copolymer
rubber present at 3 to 50 wt % of the impact copolymer weight added
via compounding, or other rubber (impact modifier) prepared by
copolymerization of two or more alpha olefins (such as
ethylene-octene) by Zeigler-Natta, metallocene, or single-site
catalysis, added via compounding such as but not limited to a twin
screw extrusion process. It is desirable to use a PP-based polymer
that has a melt flow rate of 0.8 to 8, preferably 2 to 4, more
preferably 2 to 3. It is also desirable use a PP-based polymer that
has 55 to 70%, preferably 55 to 65% crystallinity.
[0045] PP can be ultra-violet (UV) stabilized, and desirably can
also be impact modified. Particularly desirable PP is stabilized
with organic stabilizers. The PP can be free of titanium dioxide
pigment to achieve UV stabilization thereby allowing use of less
pigments to achieve any of a full spectrum of colors. A combination
of low molecular weight and high molecular weight hindered
amine-type light stabilizers (HALS) are desirable additives to
impart UV stabilization to PP. Suitable examples of commercially
available stabilizers include IRGASTAB.TM. FS 811, IRGASTAB.TM. FS
812 (IRGASTAB is a trademark of Ciba Specialty Chemicals
Corporation). A particularly desirable stabilizer system contains a
combination of IRGASTAB.TM. FS 301, TINUVIN.TM. 123 and
CHIMASSORB.TM. 119. (TINUVIN and CHIMASSORB are trademarks of Ciba
Specialty Chemicals Corporation).
[0046] The oriented polymer composition further comprises an inert
inorganic filler. Inorganic materials do not suffer from all of the
handicaps of organic fillers. Organic fillers include cellulosic
materials such as wood fiber, wood powder and wood flour and are
susceptible even within a polymer composition to color bleaching
when exposed to the sun, and to decomposition, mold and mildew when
exposed to humidity. However, inorganic fillers are generally
denser than organic fillers. For example, inert inorganic fillers
for use in the present invention typically have a density of at
least two grams per cubic centimeter. Therefore, polymer
compositions comprising inorganic fillers must contain more void
volume than a polymer composition comprising the same volume of
organic fillers in order to reach the same polymer composition
density. Surprisingly, sufficient cavitation can occur during die
drawing to achieve an oriented polymer composition having a density
of less than 0.8 grams per cubic centimeter even when the polymer
composition contains 30 wt % or more inorganic filler.
[0047] Inorganic fillers are either reactive or inert. Reactive
fillers, such as Portland cement and gypsum, undergo a chemical
reaction in the presence of water. Inert fillers do not undergo
such a chemical reaction in the presence of water. Inert fillers
are more desirable than reactive fillers in order to achieve a
stable polymer composition density because the reactive fillers
attract and react with water, causing changes in polymer
composition density. Suitable inert inorganic fillers include talc,
clay (for example, kaolin), magnesium hydroxides, aluminum
hydroxides, dolomite, glass beads, silica, mica, metal fillers,
feldspar, Wollastonite, glass fibers, metal fibers, boron fibers,
carbon black, nano-fillers, calcium carbonate, and fly ash.
Particularly desirable inert inorganic fillers include talc,
calcium carbonate, clay and fly ash. The inorganic filler can be
one or a combination of more than one inorganic filler. More
particularly, an inert inorganic filler can be any one inert
inorganic filler or any combination of more than one inert
inorganic filler.
[0048] An objective of the present invention is to achieve void
volume in a polymer composition containing inert inorganic filler
primarily if not exclusively through cavitation rather than by
means of a foaming agent. Cavitation is a process by which void
volume forms proximate to filler particles during a drawing process
as polymer is drawn away from the filler particle. Cavitation is a
means of introducing void volume into an oriented polymer
composition without having to use a blowing agent. The oriented
polymer composition of the present invention contains less than
three wt %, preferably less than two wt %, more preferably less
than one wt %, still more preferably less than 0.5 wt % blowing
agent and can be free of blowing agent. Herein, "blowing agent"
includes chemical blowing agents and decomposition products
therefrom. Measure wt % blowing agent relative to total oriented
polymer composition weight.
[0049] Generally, the extent of cavitation (that is, amount of void
volume introduced due to cavitation) is directly proportional to
filler concentration. Increasing the concentration of inorganic
filler increases the density of a polymer composition, but also
tends to increase the amount of void volume resulting from
cavitation. Particularly desirable embodiments of the present
oriented polymer composition has 30 volume-percent (vol %) or more,
preferably 40 vol % or more, more preferably 50 vol % or more void
volume based on total polymer composition volume. Most desirably,
the void volume is due primarily if not exclusively due to
cavitation. An absence of blowing agent indicates void volume is
due to cavitation.
[0050] Typically, oriented polymer composition of the present
invention contains 30 wt % or more, preferably 40 wt % or more, and
more preferably 45 wt % or more filler. Filler can be present in an
amount of 60 wt % or more, even 70 wt % or more. Generally, the
amount of filler is 95 wt % or less in order to achieve structural
integrity. Determine wt % of filler based on total oriented polymer
composition weight.
[0051] The oriented polymer composition of the present invention
has a density of less than 0.8 g/cm.sup.3, preferably 0.75
g/cm.sup.3 or less, more preferably 0.7 g/cm.sup.3 or less. Measure
oriented polymer composition density according to American Society
for Testing and Materials (ASTM) method 792-00. A density of less
than 0.8 g/cm.sup.3 is desirable to achieve a density similar to or
less than that of wood materials, which are commonly used in
markets for which the oriented polymer composition of the present
invention is useful. Having a density similar to or less than that
of wood is desirable to achieve ease of handling during shipping
and use. In that regard, a lower density composition is more
desirable than a higher density composition provided that the lower
density composition has sufficient stiffness.
[0052] One of the surprising discoveries of the present invention
is that sufficient cavitation can occur using inert inorganic
filler to achieve an oriented polymer composition having a density
of less than 0.8 g/cm.sup.3 despite having a relatively high
concentration of the high density inert inorganic filler while also
having a linear draw ratio of ten or less, even eight or less, even
five or less when using a die drawing process. Increasing linear
draw ratio results in more highly oriented polymer compositions in
the drawing dimension and greater cavitation (hence, increased void
volume). However, increasing linear draw ratio also decreases
structural integrity in an oriented article, manifest by a decrease
in delamination force in the drawing dimension. Fibrillation of the
oriented composition into strands extending in the draw direction
(drawing dimension) can occur when orientation becomes extreme and
delamination force too low. The present invention provides oriented
polymer compositions that enjoy a benefit from high cavitation void
volumes without suffering from the handicap of low delamination
strength due to linear draw ratios of eleven or more. Filled
oriented polymer compositions of the present invention have
delamination force values of greater than 44.5 Newtons (N) (ten
pounds force). The delamination for is desirably 50 N (11.2 pounds
force) or greater, preferably 75 N (16.8 pounds force) or greater,
more preferably 100 N (22.5 pounds force) or greater and still more
preferably 150 N (33.7 pounds force) or greater.
[0053] Stiffness of a polymer composition is also important for
meeting building codes for certain end uses for oriented polymer
compositions of the present invention. Measure stiffness as
flexural modulus (modulus of elasticity) in accordance to ASTM
method D-790-03. The oriented polymer compositions of the present
invention, in combination with having a density of less than 0.8
g/cm.sup.3, have a flexural modulus of 1.4 gigapascals (GPa)
(200,000 pounds per square inch (psi)) or greater, preferably 2.1
GPa (300,000 psi) or greater, more preferably 2.8 GPa (400,000 psi)
or greater. A flexural modulus of 1.4 GPa or more is desirable to
meet deck board code requirements requiring a board stiffness
sufficient that the board demonstrates less than 0.09 inches
deflection with 100 pounds per square foot weight evenly
distributed over a 16 inch span. (see, for example, International
Code Council-Evaluation Services (ICC-ES) requirement AC174
entitled: Acceptance Criteria for Deck Board Ratings and Guardrail
Systems). Increasing flexural modulus is desirable to achieve even
greater board stiffness in order to safely support further weight
than the code requires.
[0054] All cross section dimensions of the oriented polymer
compositions of the present invention are greater than 1.5
millimeters (mm), and are typically 3 mm or greater, more typically
5 mm or greater. Such polymer compositions have relatively large
cross sectional areas which distinguish them from films and fibers.
Drawing a polymer composition with relatively large cross section
dimension (that is, large cross section area) has challenges that
film drawing process do not have due to processing window
differences. For instance, film drawing can occur at much lower
temperatures than large cross section articles. Draw stresses
necessary for drawing films are much lower than for large cross
section articles. As a result, a drawing process is more likely to
exceed the break stress for larger cross section articles than for
films.
[0055] Moreover, achieving sufficient draw stress to induce enough
cavitation to achieve a density of less than 0.8 g/cm.sup.3 is more
challenging as the cross section dimensions of the polymer
composition increase. Nonetheless, the process of the present
invention (described below) overcomes each of these challenges with
polymer compositions that exceed the dimensions of a film in order
to produce the oriented polymer composition of the present
invention.
[0056] Oriented polymer compositions of the present invention
desirably have a low degree of connectivity between void spaces
that result from cavitation. Connectivity provides fluid
communication between void spaces and can facilitate fluid (for
example, moisture) build up within the composition. That, in turn,
can cause an undesirable increase in oriented polymer composition
density, or fluctuations in density depending on the humidity.
Desirably, less than 75%, preferably less than 50%, more preferably
less than 25%, even more preferably less than 10% of the void
volume due to cavitation is accessible by water. Most desirably,
less than 5%, even less than 1% of the void volume is accessible by
water. Measure water accessibility by immersing a polymer
composition in water and recording its change in density with time.
Water uptake into the void spaces (indicating interconnectivity) is
evident by an increase in density after immersion in water. In a
particularly desirable embodiment, the same accessibility values
apply after placing the oriented polymer composition in a pressure
cooker.
[0057] Oriented polymer composition of the present invention can
have any conceivable cross sectional shape including circular or
non-circular ellipse, oval, triangle, square, rectangle, pentagon,
hexagon, keyhole, arched doorway, or any other profile useful as
wood trim or as decking components (for example, railings, boards,
spindles).
Solid State Drawing Process
[0058] A second aspect of the present invention is a solid state
drawing process for producing the oriented polymer composition of
the first aspect. A solid state drawing process involves pulling
(that is, drawing) a polymer composition comprising an orientable
polymer with sufficient force so as to induce alignment of polymer
molecules in the polymer composition. Aligning polymer molecules
(that is, polymer orientation or "orientation") is desirable to
enhance the strength and modulus (stiffness) of a polymer
composition. The drawing process can also induce cavitation in a
filled polymer composition, thereby reducing the polymer
composition's density.
[0059] The solid state drawing process of the present invention
involves drawing a polymer composition containing an inert
inorganic filler and a continuous phase of one or more orientable
polymer. The polymer composition is the same as that described
above for the oriented polymer composition. Orientation and
cavitation of the polymer compound occurs while drawing the polymer
composition in the present process.
[0060] Condition the polymer composition comprising the inert
inorganic filler and orientable polymer to a drawing temperature
(T.sub.d) prior to drawing.
[0061] The drawing temperature is more than ten degrees Celsius
(.degree. C.) below the T.sub.s of the polymer composition. The
drawing temperature can be fifteen .degree. C. or more, twenty
.degree. C. or more, thirty .degree. C. or more, even forty
.degree. C. or more below the polymer composition T.sub.s.
Cavitation will not occur to any significant extent if the drawing
temperature is above the orientable polymer composition's T.sub.s.
The present process requires drawing at a temperature of more than
ten .degree. C. below T.sub.s in order to achieve sufficient
cavitation to reach a final density of 0.8 gram per cubic
centimeter (g/cm.sup.3) for the oriented polymer composition.
[0062] Generally, the drawing temperature is forty .degree. C. or
less below the polymer composition's T.sub.s. Drawing a polymer
composition at a draw temperature more than forty .degree. C. below
its T.sub.s requires slower draw rates than is economically
desirable in order to avoid fracturing.
[0063] Desirably, 50 weight-percent (wt %) or more, more desirably
90 wt % or more of the polymers in a polymer composition have a
T.sub.m. More desirably, all of the polymers in the polymer
composition have a T.sub.m.
[0064] The present process is a die drawing process. That means
drawing occurs through a solid state drawing die at the drawing
temperature. A die drawing process is in contrast to a free draw
process. In a free draw process a polymer composition necks apart
from any physical constraint. Free drawing offers little control
over the final polymer composition size and shape after drawing
other than by controlling the polymer composition shape prior to
drawing. Typically, a free drawn polymer composition has a cross
sectional shape proportional to its cross sectional shape prior to
drawing. The present process utilizes a drawing die in order to
achieve better control and to enable drawing to a different cross
sectional shape in the polymer composition after drawing as
compared to prior to drawing. The die drawing process may be either
batch (for example, drawing discrete polymer billets) or continuous
(for example, drawing a continuous feed of polymer composition from
an extruder).
[0065] A drawing die provides a physical constraint that helps to
define a polymer composition's size and shape by directing polymer
movement during the drawing process. Die drawing occurs by
conditioning a polymer composition to a drawing temperature and
then pulling a polymer composition through a shaping channel in a
drawing die. The shaping channel constricts the polymer composition
in at least one dimension causing the polymer composition to draw
to a general cross sectional shape. Die drawing processes
advantageously provide greater control in shaping a polymer
composition during a drawing process than is available in a free
draw process.
[0066] The present process is not limited to a specific drawing
die. However, the present invention advantageously employs a
substantially proportional drawing die. A substantially
proportional drawing die directs drawing of a polymer composition
in such a manner so as to achieve an oriented polymer composition
having a cross sectional shape proportional to that of the polymer
composition entering the proportional drawing die. Such a die
balances polymer forces directed towards a polymer cross section
centroid such that variations in polymer composition or processing
conditions do not affect the shape of the final oriented polymer
composition. Therefore, such a drawing die advantageously provides
predictable control over the final polymer composition shape
despite changes in polymer composition or drawing process
conditions.
[0067] Draw the polymer composition through a drawing die at a
specific draw rate. The draw rate is instrumental in determining
the density and modulus of a resulting oriented polymer
composition. Faster draw rates can advantageously induce more
cavitation (therefore, produce a lower density product) generate a
greater extent of orientation (higher modulus) and generally
provide a more economically efficient process. Draw rate is a
linear rate that polymer composition exits a drawing die in a
drawing direction.
[0068] Part of the present surprising discovery is that to achieve
a density of less than 0.8 g/cm by means of cavitation and a
modulus of 1.4 GPa (200,000 psi) the process must use a draw rate
of 0.25 meter per minute (m/min) or faster, Desirably, the draw
rate is 0.5 m/min or faster, preferably one m/min or faster, and
more preferably two m/min or faster. An upper limit for the draw
rate is limited primarily by the drawing force necessary to achieve
a specific draw rate. The drawing force should be less than the
tensile strength of the polymer composition at the drawing
temperature in order to avoid fracturing the polymer composition.
Typically, the draw rate is 30.5 meters per minute or slower, more
typically nine meters per minute or slower.
[0069] Another part of the present discovery is that sufficient
cavitation to provide a polymer composition with a density of less
than 0.8 g/cm.sup.3 and a flexural modulus of 1.4 GPa or greater is
possible using a linear draw ratio of ten or less, even eight or
less, even five or less. WO2004/009334 discloses oriented polymer
compositions containing reactive inorganic fillers and their
examples illustrate oriented polymer composition having a density
less than 0.8 g/cm.sup.3 only when using a free draw process
implementing a linear draw ratio of greater than 11. A sample with
such a high linear draw ratio will have an undesirably low
delamination force (see, for example, Comparative Examples M-P
bellow).
[0070] The present invention ideally utilizes a nominal draw ratio
of 1.25 or more and can employ a nominal draw ratio of 1.5 or more,
two or more, three or more, four or more, five or more, even six or
more. Higher nominal draw ratios are desirable to achieve higher
polymer orientation. Increasing polymer orientation increases
polymer composition strength and stiffness. However, increasing
nominal draw ratio also increases linear draw ratio. Therefore, it
is desirable to use a nominal draw ratio that is 8 or less,
preferably 6 or less, more preferably 5 or less, even more
preferably 4 or less in order to maximize the structural integrity
of the oriented polymer composition. The nominal draw ratio can be
3 or less, even 2 or less.
EXAMPLES
[0071] The following examples serve to further illustrate
embodiments of the present invention.
Preparation of Polymer Compositions
TABLE-US-00001 [0072] TABLE 1 Initial Polymer Compositions Polymer
Composition Composition T.sub.s (.degree. C.) Polymer Filler (a)
163 Nucleated polypropylene- 46 wt % Talc composition ethylene
random copolymer based on total having 0.5 wt % ethylene
composition weight. Talc component and a melt flow composition is
50-60 wt % rate of 3 (for example., talc and 40-50 wt % INSPIRE
.TM. D404.01, INSPIRE is magnesium carbonates a trademark of The
Dow having a median diameter Chemical Company) of 16.4 microns.
(for example, TC-100 from Luzenac) (b) 163 [same as (a)] 46 wt %
Calcium carbonate having a mean particle size of 1.1 microns, with
wt % based on total composition weight (for example, Supercoat from
Imersys) (c) 148 Polypropylene-ethylene 46 wt % fly ash as random
copolymer having 3.2 wt received from Headwaters % ethylene and a
melt flow Resources (for example, rate of 1.9 (for example, Class F
from Headwaters 6D83K from The Dow Chemical Resources) Company).
(d) 148 [same as (c)] [same as (a)] (e) 160 Polypropylene
homopolymer [same as (a)] with a melt flow rate of 2.8 (for
example, 5D37 from The Dow Chemical Company). (f) 163 [same as (a)]
50 wt % Portland Cement (g) 163 [same as (a)] 40 wt % Portland
Cement
[0073] Prepare polymer compositions "a" through "g" (described in
Table 1) by the following procedure: compound the polymer and
filler using a suitable mixing extruder, for example a Farrell
Continuous Mixer (FCM) or co-rotating twin screw extruder. Feed
polymer and filler at the specified weight ratio through standard
loss in weight feeders. Melt the polymer in the mixing extruder and
mix the filler into the polymer matrix to form a polymer/filler
mix. Feed the polymer/filler mix from the mixing extruder into a
suitable pumping device (for example, a single screw extruder or
gear pump) and then through a multi-hole strand die to produce
multiple strands of the polymer/filler mix. Cool the strands under
water and cut them into pellets.
[0074] For Compositions (a)-(e), re-extrude the pellets into a
polymer composition billet. Alternatively the polymer/filler mix
may be pumped directly from the pumping device through a profile
die and then cooled to produce a polymer composition billet without
forming pellets and re-extruding. As yet another alternative, the
polymer/filler mix may be pumped directly from the pumping device,
through a profile die, cooled to a drawing temperature and then
drawn to an oriented polymer composition.
[0075] For Compositions (f) and (g), injection mold the composition
into a ASTM D-790 type 1 tensile bar for use in Comparative
Examples (Comp Exs) M-P.
Drawing Procedure
Examples (Exs)
Smaller Scale Compositions
[0076] Mill a billet of polymer composition corresponding to the
desired example to have cross section dimensions to match the
nominal draw ratio for a specific example. Table 2 provides the
dimensions of the billets for the corresponding nominal draw
ratios. Mill an initial tab on an end of each billet that is
smaller in dimension than any point in the shaping channel and
longer than the length of the die. The tab extends through the die
for attaching an actuator to pull the rest of the billet through
the die.
TABLE-US-00002 TABLE 2 Milled Billet Dimensions Milled Billet
Milled Billet Nominal Draw Width Height Ratio cm (in) cm (in) 2
1.80 (0.707) 0.450 (0.177) 4 2.54 (1.0) 0.635 (0.25)
[0077] Draw Exs 1(a)-1(f) using a proportional die with a die exit
opening of 1.27 cm (0.5'').times.0.3175 cm (0.125'') and a
rectangular shaping channel having cross section dimensions
substantially proportional to one another. The walls spanning the
height of the channel converge at 15.degree. angle to reduce the
width while the walls spanning the width dimension converge at a
3.83.degree. angle to reduce the height. This die is described and
illustrated further in a U.S. patent application having Ser. No.
60/858,122 and entitled SUBSTANTIALLY PROPORTIONAL DRAWING DIE FOR
POLYMER COMPOSITIONS (see, Proportional Die description in the
Examples, incorporated herein by reference). The die channel
opening has a cross section that is larger and proportional to the
cross section of the billet entering the die channel, as well as
the die exit opening.
[0078] Condition each billet to a drawing temperature prior to
drawing through the drawing die. Draw a billet through the drawing
die by extending the initial tab through the drawing die, gripping
the tab with an actuator and then pulling the billet through the
drawing die using an MTS hydraulic tester, model number 205. Center
the billet in the shaping channel of the die. Draw the billet
slowly at first to orient the leading edge and then bring to a
specific draw rate while maintaining the die at the drawing
temperature. The drawn polymer composition represents the Example
or Comparative Example.
[0079] Each of Comparative Examples A-I and Examples 1(a)-1(f) has
a rectangular cross section with a width of 9-10 mm and a height of
2.1-2.6 mm and has less than 5% of the void volume in each
accessible by water in a water immersion test.
TABLE-US-00003 TABLE 3 Draw Temp. .degree. C. below polymer Draw
Oriented Flex Delamination Polymer composition Rate Density Modulus
Force Ex Comp. T.sub.s NDR.sup.1 cm/min LDR.sup.2 g/cm.sup.3 GPa N
(lb force) Comp a 10 4 2.54 5.7 1.09 4.6 NM* Ex A Comp a 10 4 25.4
7.3 0.95 4.2 NM* Ex B Comp a 10 4 127 9.9 0.82 3.9 NM* Ex C Comp a
10 4 254 10.1 0.84 3.7 NM* Ex D Comp a 10 4 508 9.7 0.85 3.6 NM* Ex
E Comp a 20 4 2.54 7.2 0.89 4.2 49.4 (11.1) Ex F Comp a 20 4 25.4
9.7 0.82 4.9 54.3 (12.2) Ex G 1(a) a 20 4 50.8 10.3 0.79 5.0 51.6
(11.6) 1(b) a 20 4 101 11.6 0.75 5.5 99.6 (22.4) 1(c) a 20 4 127
12.8 0.73 5.3 70.3 (15.8) Comp a 30 4 2.54 6.7 0.93 4.0 187 (42) Ex
H 1(d) a 30 4 25.4 9.7 0.75 4.5 84.5 (19) Comp a 30 4 127 13.6 0.65
6.6 28 (6.3).sup.3 Ex I 1(e) a 30 4 254 14.4 0.68 NM* 82.7 (18.6)
1(f) a 30 4 508 13.7 0.69 NM* 73.4 (16.5) *"NM" means "not
measured" .sup.1NDR is "nominal draw ratio" .sup.2LDR is "linear
draw ratio" .sup.3It is expected that this low delamination value
is an outlier, perhaps due to unobserved void(s) in the center of
the sample. The trend in samples 1(d)-1(e) suggests this value
should be between 84.5 and 82.7 Newtons. As measured, however, this
delamination value is outside our claimed range and so the example
is listed as a Comparative Example.
[0080] Comparative Examples A-H and Examples 1(a)-1(f) illustrate
the effect of drawing temperature on oriented polymer composition
density for a polymer composition similar to composition "a".
Examples 1(a)-(f) are free of blowing agent.
Examples (Exs) 2-7
Larger Scale Compositions
[0081] Mill a billet of polymer composition corresponding to the
desired example to have cross section dimensions to match a nominal
draw ratio for a specific example. Table 4 provides the dimensions
of the billets for the corresponding nominal draw ratios. Mill an
initial tab on an end of each billet that is smaller in dimension
than any point in the shaping channel and longer than the length of
the die. The tab extends through the die for attaching an actuator
to pull the rest of the billet through the die.
TABLE-US-00004 TABLE 4 Milled Billet Dimensions Milled Billet
Milled Billet Width Height Nominal Draw Ratio cm (in) cm (in) 1.8
6.81 (2.68) 3.40 (1.34) 4 10.16 (4.0) 5.08 (2.0)
[0082] Condition each billet to the desired temperature prior to
drawing through the drawing die. Draw a billet through a drawing
die by extending the initial tab through the drawing die; gripping
the tab with an actuator and then pulling the billet through the
drawing die. Center the billet in the shaping channel of each die.
Draw the billet slowly at first to orient the leading edge and then
bring to a specific draw rate. Draw the billet through a
proportional die.
[0083] The drawing die used is a proportional die proportional
similar to that used in Example 1. The proportional die for
Examples 2-7 has a die exit opening of 5.08 cm (2'').times.2.54 cm
(1'') and a rectangular shaping channel having cross section
dimensions substantially proportional to one another. The walls
spanning the height of the channel converge at 15.degree. angle
towards a plane centrally located between them in order to reduce
the width of the die channel while progressing towards the
channel's exit opening. The walls spanning the width dimension
converge at a 3.83.degree. angle towards a plane centrally located
between them in order to reduce the height of the die channel while
progressing towards the channel's exit opening. The die channel
entrance opening has a cross section that is larger and
proportional to both the cross section of the billet entering the
die channel and the die exit opening. At the die exit was a land
with length of 1.27 cm (0.5'').
TABLE-US-00005 TABLE 5 Conditions and Results for Exs 2-7 Draw
Temp. (.degree. C. below polymer Draw Oriented Flex Delamination
Polymer composition Rate Density Modulus Force Ex Comp. T.sub.s)
NDR (m/min) LDR (g/cm.sup.3) (GPa) N (lb force) 2 a 20 2 2.4 9.5
0.65 2.8 75.2 (16.9) 3 a 15 2 2.4 8.5 0.80 3.0 127 (28.5) 4 a 18 4
2.4 10.5 0.78 3.3 158 (35.5) 5 a 18 2 2.4 9 0.80 2.8 122 (27.4) 6 e
23 2 2.4 10 0.73 2.4 89 (20) 7 e 18 2 2.4 8.5 0.80 3.0 110
(24.7)
[0084] Each of Exs 2-7 had a width between 29 and 36 mm and a
height between 14 and 18 mm. Each of Exs 2-7 has less than 5% of
the void volume accessible by water.
[0085] Exs 2-7 illustrate large scale oriented polymer compositions
of the present invention prepared with various polymer
compositions, drawing temperatures and linear draw ratios. Exs 2-7
are free of blowing agent and have less than 5% of their void
volume accessible by water in an immersion test.
Comp. Ex. M-P
Free Drawn Sample with Portland Cement
[0086] Free draw the tensile bars of compositions (f) and (g)
according to the parameters in Table 6. Mark three lines on the
gauge area of the tensile bars. Space each line 2.54 centimeters
(one inch) apart from its neighboring line(s) perpendicular to the
drawing direction. Draw the tensile bars in an oven after allowing
the tensile bars to equilibrate to the specified drawing
temperature. Grip one end of the tensile bar with a stationary
(anchoring) self tightening grip. Grip an opposing end of the
tensile bar with a mobile self-tightening grip. Using a caterpillar
type puller draw the tensile bar by pulling the mobile
self-tightening grip affixed to the tensile bar at a rate of 2.4
meters (eight feet) per minute to draw the tensile bar 0.6-0.9
meters (two-three feet).
[0087] Determine linear draw ratio by measuring the distance
between marked lines on the tensile bars after drawing and dividing
that by the 2.54 centimeter (one inch) spacing from prior to
drawing. The linear draw ratio is the average ratio determined for
the two line spacings.
[0088] Measure density, flexural modulus and delamination force in
the same manner as the other examples. Note, because these
comparative examples are free drawn, there is no drawing die so the
drawing process effectively has a nominal draw ratio of one.
TABLE-US-00006 TABLE 6 Draw Temp. Delami- (.degree. C. below nation
polymer Flex Force Comp. Polymer composition Density Modulus N Ex
Comp. T.sub.s) LDR (g/cm.sup.3) (GPa) (lb force) M f 5 9 0.68 21.4
(4.8) N f 5 9 0.74 20.9 (4.7) O f 10 8.5 0.66 36.9 (8.3) P g 10
7.25 0.78 24.0 (5.4)
[0089] Comparative Examples M-P illustrate that free drawn samples
containing 40-50 wt % Portland cement suffer from a Delamination
Force that is less than 44.5 Newtons (10 pounds force). Attempts at
free drawing comparative examples of these polymer compositions at
LDR values greater than 9 were unsuccessful because the tensile
bars would break.
[0090] Based on data presently being collected and compiled, it is
expected that increasing the linear draw ratio on a filled polymer
composition will reduce the Delamination Force of the resulting
oriented polymer composition. Furthermore, it is expected that
increasing the amount of Portland cement to levels above 50 wt %
(for example, 60 wt %) of the polymer composition will retain or
reduce the Delamination Force relative to compositions with 40-50
wt % Portland cement that are free drawn at the same drawing
temperature and LDR.
* * * * *