U.S. patent application number 16/442024 was filed with the patent office on 2019-12-19 for foamable polyolefin compositions and methods thereof.
This patent application is currently assigned to A. SCHULMAN, INC.. The applicant listed for this patent is A. SCHULMAN, INC.. Invention is credited to FABIO CECCARANI, VASSILIOS GALIATSATOS, RYAN KRAMB, CHICHANG SHU, IGNAZIO TRIASSI.
Application Number | 20190382549 16/442024 |
Document ID | / |
Family ID | 67253986 |
Filed Date | 2019-12-19 |
United States Patent
Application |
20190382549 |
Kind Code |
A1 |
GALIATSATOS; VASSILIOS ; et
al. |
December 19, 2019 |
FOAMABLE POLYOLEFIN COMPOSITIONS AND METHODS THEREOF
Abstract
Foamed propylene-based reactor made polyolefins, and articles
made therefrom, are described. The compositions have a resin that
is a reactor made propylene based random copolymer or terpolymer
with high comonomer content, combined with a foaming agent. The
foaming agent can be at least one physical blowing agent or at
least one chemical foaming agent, and may include optional
nucleating agents. Reactor made copolymers and terpolymers have a
large range of high comonomer content and therefore have physical
properties such as increased flexibility, high gloss, lower sealing
temperature, and improved compatibility with other polyolefins.
These properties translate into a broad scope of potential
applications and foamed architecture. This allows the combination
of the copolymer or terpolymer, and foaming agents to be fine-tuned
for selected foaming application.
Inventors: |
GALIATSATOS; VASSILIOS;
(LEBANON, OH) ; CECCARANI; FABIO; (YOUNGSTOWN,
OH) ; SHU; CHICHANG; (MASON, OH) ; KRAMB;
RYAN; (MONROE, OH) ; TRIASSI; IGNAZIO;
(WILMINGTON, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
A. SCHULMAN, INC. |
HOUSTON |
TX |
US |
|
|
Assignee: |
A. SCHULMAN, INC.
HOUSTON
TX
|
Family ID: |
67253986 |
Appl. No.: |
16/442024 |
Filed: |
June 14, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62685133 |
Jun 14, 2018 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08J 2323/06 20130101;
C08K 5/0083 20130101; C08J 2323/08 20130101; C08J 2323/16 20130101;
C08L 2310/00 20130101; C08F 210/06 20130101; C08J 9/12 20130101;
C08J 2323/14 20130101; C08J 2203/14 20130101; C08L 23/142 20130101;
C08F 210/02 20130101; C08L 2205/025 20130101; C08J 9/0061 20130101;
C08J 2201/024 20130101; C08J 9/06 20130101; C08J 9/141 20130101;
C08J 2423/08 20130101; C08L 23/142 20130101; C08J 2423/14 20130101;
C08J 3/22 20130101; C08J 9/122 20130101; C08J 2203/06 20130101;
C08J 9/143 20130101; C08J 2323/12 20130101; C08L 23/142 20130101;
C08L 2203/14 20130101; C08J 2423/12 20130101; C08J 2423/16
20130101; C08L 23/142 20130101; C08L 23/14 20130101; C08K 13/02
20130101; C08K 5/0083 20130101; C08L 23/14 20130101; C08L 23/14
20130101; C08K 13/02 20130101 |
International
Class: |
C08J 9/14 20060101
C08J009/14; C08J 9/12 20060101 C08J009/12; C08J 3/22 20060101
C08J003/22; C08K 5/00 20060101 C08K005/00; C08F 210/06 20060101
C08F210/06; C08F 210/02 20060101 C08F210/02 |
Claims
1. A foam composition comprising: a reactor made polyolefin
composition comprising a crystalline random copolymer having: a) a
first propylene-based copolymer or terpolymer selected from the
group comprising: i) a copolymer of propylene and ethylene, wherein
the content of the ethylene is between 1-7 wt %; ii) a copolymer of
propylene and at least one C.sub.4-C.sub.8 alpha-olefin, wherein
the content of the alpha-olefin is between 2-14 wt %; iii) a
terpolymer of propylene, ethylene, and at least one C.sub.4-C.sub.8
alpha-olefin, wherein the content of ethylene is between 0.5-4.5 wt
% and the content of the alpha-olefin is between 2-6 wt %, wherein
the total content of said ethylene and said at least one
alpha-olefins in equal to or lower than 6.5 wt %; and/or b) a
second propylene-based copolymer or terpolymer selected from the
group comprising: i) a copolymer of propylene and at least one
C.sub.4-C.sub.8 alpha-olefin, wherein the content of the
alpha-olefin is between 8-30 wt %; ii) a terpolymer of propylene,
ethylene, and at least one C.sub.4-C.sub.8 alpha-olefin, wherein
the content of ethylene is between 1-7 wt % and the content of the
alpha-olefin is between 6-8 wt %, wherein the total content of said
ethylene and said at least one alpha-olefins in equal to or lower
than 6.5 wt %; wherein said first propylene-based copolymer is
present in a 0 to 80 wt % and said second propylene-based is
present at a 20 to 100 wt %.
2. The foam composition of claim Error! Reference source not
found., wherein said crystalline random copolymer has a melt flow
rate between 2 to 15 g/10 min (ASTM D 1238).
3. The foam composition of claim Error! Reference source not
found., wherein said reactor made polyolefin composition is foamed
using at least one physical blowing agent (PBA) or at least one
chemical foaming agent (CFA).
4. The foam composition of claim 3, wherein said reactor made
polyolefin composition is combined with a masterbatch comprising at
least one nucleating agent.
5. The foam composition of claim 4, wherein said physical blowing
agent is selected from a group comprising highly pressurized
CO.sub.2, N.sub.2, air, propane, isobutane, butane,
CFC-derivatives, argon, or combinations thereof.
6. The foam composition of claim 4, wherein said chemical foaming
agent is in the same masterbatch as at least one nucleating agent
or in a different masterbatch as at least one nucleating agent.
7. The foam composition of claim 6, wherein the total amount of
masterbatch in the foam composition is 5 wt % by weight or less of
said reactor made polyolefin composition.
8. The foam composition of claim 3, wherein said chemical foaming
agent is endothermic or exothermic.
9. The foam composition of claim 3, wherein said chemical foaming
agent acts as a nucleating agent.
10. An article comprising a foamed reactor made polyolefin
composition according to claim 1.
11. The article of claim 10, said article being a sheet, a strand,
a tube, or a container.
12. A foam composition comprising: a reactor made polyolefin
composition comprising a crystalline propylene/ethylene random
copolymer having: a) from about 4.5 wt % to about 8 wt % of
ethylene, and; b) from about 92 wt % to about 95.5 wt % of
propylene wherein said crystalline propylene/ethylene random
copolymer has a melt flow rate between 0.3 and 15 g/10 min (ASTM D
1238).
13. The foam composition of claim 12, wherein said reactor made
polyolefin composition is foamed using at least one physical
blowing agent (PBA) or at least one chemical foaming agent
(CFA).
14. The foam composition of claim 13, wherein said reactor made
polyolefin composition is combined with a masterbatch comprising at
least one nucleating agent.
15. The foam composition of claim 14, wherein said physical blowing
agent is selected from a group comprising highly pressurized
CO.sub.2, N.sub.2, air, propane, isobutane, butane,
CFC-derivatives, argon, or combinations thereof.
16. The foam composition of claim 14, wherein said chemical foaming
agent is in the same masterbatch as at least one nucleating agent
or in a different masterbatch as at least one nucleating agent.
17. The foam composition of claim 16, wherein the total amount of
masterbatch in the foam composition is 5 wt % by weight or less of
said reactor made polyolefin composition.
18. The foam composition of claim 13, wherein said chemical foaming
agent is endothermic or exothermic.
19. The foam composition of claim 13, wherein said chemical foaming
agent acts as a nucleating agent.
20. An article comprising a foamed reactor made polyolefin
composition according to claim 12.
Description
[0001] This application claims the benefit of U.S. Provisional
Application No. 62/685,133, filed on Jun. 14, 2018, and
incorporated herein by reference in its entirety for all
purposes.
FIELD OF THE DISCLOSURE
[0002] The disclosure relates to polyolefin compositions,
particularly to reactor made polyolefin compositions to be foamed
or expanded.
BACKGROUND OF THE DISCLOSURE
[0003] Polyolefins have been frequently used in commercial plastics
applications because of their outstanding performance and cost
characteristics. These polymers can be either amorphous or highly
crystalline, and they are able to behave as thermoplastics,
thermoplastic elastomers, or thermosets. As such, polyolefins are
easily designed and modified for select applications by properly
selecting their molecular structure and molecular weight
distribution(s) to obtain a suitable balance of stiffness, impact
resistance, and processability in the extrusion processes.
[0004] One area of increased interest in polyolefins is the
formation of foams. Polyolefin foams have become a very important
part of the polymer industry due to their beneficial
characteristics, including light weight, superior cushioning, heat
insulation, and resistance to water and chemicals.
[0005] Although polyolefin foams are relatively recent additions to
the range of polymeric foam materials, having been first marketed
in the early sixties, they have found a use in almost every
industry. Areas of application include packaging, sports and
leisure, toys, insulation, automotive, military, aircraft,
buoyancy, cushioning and others. This broad scope of applications
results from the wide range of physical properties of the olefins,
from hard and tough to soft and resilient. Hard (though not
brittle) foams are obtained using e.g. high density polyethylene as
the base polymer, while softer materials are obtained using
ethylene copolymers such as ethylene vinyl acetate (EVA). This
ability to vary foam properties by changes in the polymer is
similar to that seen in polyurethane foams, although the
technologies are very different since almost all polyurethane foams
result from liquid technology with in situ polymerization and
blowing while polyolefin foams are produced starting with the basic
thermoplastic polymer.
[0006] With the advanced developments of polymerization techniques,
polyolefins have been rapidly expanding in foam applications
through various chemical and physical forms, including cross-linked
polyolefins, copolymers, high melt strength (branched) polyolefins,
and polyolefin blends. However, despite the advances made in
foaming polyolefins, there is a continued need for the development
of improved foamable compositions having increased strength,
foamability, cell consistency, dimensional stability, and
temperature resistance, without added costs to the manufacturing
process. Ideally, the new foamable compositions would also reduce
carbon footprint by being compatible with polyolefin recycle
streams.
SUMMARY OF THE DISCLOSURE
[0007] The present disclosure provides novel foamed polyolefin
compositions with improved physical properties. Specifically, the
foamable compositions comprise reactor made propylene-based random
copolymer (RACO) or terpolymer polyolefins with high comonomer
content (greater than about 5% comonomer by weight) that are foamed
by a chemical or physical foaming agent. Various articles can be
made with the foamed reactor made propylene-based random copolymer
(RACO) or terpolymer polyolefins.
[0008] Propylene-based RACOs and terpolymers with high comonomer
content have improved properties for sealing applications because
of their low sealing initiation temperature, optical properties,
good processability, and lack of stickiness. Reactor made RACOs and
terpolymers with high comonomer content were selected as the
propylene-based polyolefin to be foamed because of their improved
properties over conventional propylene-based RACO polyolefins. The
gas phase reactor polymerization process allows for incorporation
of higher comonomer content (e.g. ethylene and/or butene) which
provides improved physical properties such as increased
flexibility, high gloss, lower sealing temperature, and improved
compatibility with other polyolefins when compared to the
conventional propylene-based RACOs and terpolymers.
[0009] The reactor made propylene-based RACO or terpolymer base
resins for the foamed compositions described herein are comprised
of A) a propylene-based RACO or terpolymer with high comonomer
content, B) a foaming agent, and C) optionally one or more
nucleating agents. Any reactor made propylene-based random
copolymer or terpolymer polyolefin with a high comonomer content
that is greater than about 5% by weight can be used as Component A.
Alternatively, the selected reactor made propylene-based random
copolymer or terpolymer polyolefins can have a high comonomer
content of greater than about 8% by weight or greater than about
13% by weight. These higher comonomer polyolefins (about 8 wt % or
above) may be chosen because they have improved physical properties
over comonomer polyolefins less than 5 wt % of the comonomer, such
as increased flexibility, high gloss, lower sealing temperature,
and improved compatibility with other polyolefins. Exemplary
comonomers include ethylene and C.sub.4-C.sub.8 alpha-olefins.
[0010] In some embodiments, the reactor made polyolefin in the
foamed composition is a random propylene and ethylene copolymer
with a high ethylene content. In other embodiments, the reactor
made polyolefin is a terpolymer with ethylene, propylene and butene
comonomers. In some embodiments, the reactor made polyolefin is a
blend of a random copolymer and a terpolymer. In yet more
embodiments, the reactor made propylene-based RACO or terpolymer is
prepared using a multi-stage gas phase polymerization process.
[0011] To obtain the foamed polyolefin composition and articles
made from the foamed polyolefin composition of the present
disclosure, the chosen reactor made propylene-based RACO or
terpolymer is foamed using processes and foaming agents known in
the art, including both physical and chemical types.
[0012] Any physical blowing agents (PBA), also known as physical
foaming agents, can be used to foam the reactor made
propylene-based RACO or terpolymer base resin, including, but are
not limited to, highly pressurized CO2, N2, air, propane,
isobutane, butane, CFC-derivatives, and/or argon.
[0013] The PBAs can be metered into the base resin's melt during
foam extrusion or foam injection molding. The PBAs may be injected
or introduced in the molten polymer mass in the extruder at a
distance from the point where the solid polymer is fed, where the
polymer is found melted and homogeneous. When the pressurized PBAs
are injected directly into the melt, they expand when returning to
atmospheric pressure, forming minute cells within the polymer.
[0014] To promote cell formation when using PBAs as foaming agents,
the reactor made propylene-based RACO or terpolymer can be combined
with a masterbatch containing at least one nucleating agent. A
nucleating agent is useful for resins with a polypropylene base as
the nucleating agent can impart property enhancement, improved
molding or extrusion productivity, and increased transparency to
the reactor made propylene-based RACO or terpolymer. To ensure
proper dispersion of the nucleating agents, the masterbatch uses a
carrier resin that is compatible with at least one polymer or
monomer in the polyolefin, such as polyethylene or polypropylene.
For instance, a polyethylene carrier resin would be compatible with
the comonomer of the RACO or terpolymer. This allows for consistent
cell morphologies with controlled size distributions throughout the
extruded and foamed reactor made propylene-based RACO or
terpolymer.
[0015] In other embodiments, the reactor made propylene-based RACO
or terpolymer base resin is foamed using at least one chemical
foaming agent (CFA). CFAs produce/release gas when decomposed,
imparting a cellular structure to the material. The CFA gas remains
dissolved in the polymeric melt while the melt is under pressure.
When the melt is injected into the mold or extruded, the pressure
is reduced allowing the gas to expand the polymer.
[0016] As with the nucleating agent, a masterbatch may be used to
ensure proper dispersion of the CFA(s), and the carrier resin in
the masterbatch is compatible with at least one monomer in the
reactor made propylene-based RACO or terpolymer base resin.
[0017] The CFA(s) can be endothermic or exothermic. Endothermic is
desired, as the CFA tends to be more stable in the blend and does
not decompose and produce gas until exposed to heat in the
extrusion process. Further, the CFA(s) may also act as a nucleating
agent to promote cell formation in the reactor made propylene-based
RACO or terpolymer base resin. A nucleating chemical foaming agent
is useful for resins with a polypropylene component as the
nucleating agent can impart property enhancement, improved molding
or extrusion productivity, and increased transparency to the
reactor made propylene-based RACO or terpolymer. However,
nucleating abilities are not a requirement for the CFA.
[0018] The masterbatches used for distributing CFAs contain at
least one chemical foaming agent but can also have a mix of
chemical foaming agents in a variety of concentrations. In some
embodiments, the masterbatch can have CFA(s) and optional
nucleating agents separate from the CFA(s). Alternatively, a
mixture of chemical foaming agents, both nucleating and
non-nucleating, can be used in the masterbatch to fine-tune the
characteristics of the resulting foam, such as cell size, cell
distribution, and cell stability for selected applications. In yet
another alternative, multiple masterbatches can be combined to
provide the desired CFA(s) and optional nucleating agents.
[0019] The articles formed using the foamed compositions described
herein are not limited to any specific architecture. The foams can
be extruded in-line during processing in many shapes, including
sheets, strands, tubes, containers, or custom profiles specific to
certain applications, which eliminates the need and additional
costs for secondary processing steps. Alternatively, the foams can
be injection molded. In yet another alternative, the foams can also
be layered, or combined with other polyolefin resins as needed for
specific applications. For instance, the foamed articles made from
the reactor made RACOs or terpolymers can be used as a core layer
with one or more outside layers made of a solid polyolefin. As
such, the physical properties of the polyolefins, the tunability of
the foam's cellular structure using mixes of CFAs, PBAs, and
optional nucleating agents, and the extensive architectures
available, combine synergistically to allow for a broad scope of
applications. In either case, the gas should be completely
dissolved in the polymer melt and kept under appropriate pressure
until released from the die.
[0020] The present disclosure includes any of the following
embodiments in any combination(s):
[0021] A foamable composition comprising a propylene-based
polyolefin having a melt flow rate between 2 to 15 g/10 min, and a
masterbatch having at least one chemical foaming agent, wherein the
MFR values are measured according to ASTM D 1238L. The
propylene-based polyolefin can have a semi-crystalline propylene
copolymer composition having: (A) 20-80 wt % by weight of one or
more propylene-based components selected from the group consisting
of propylene/ethylene copolymers containing 1-7 wt % of ethylene;
copolymers of propylene with one or more C.sub.4-C.sub.8
alpha-olefins, containing 2-10 wt % of the C.sub.4-C.sub.8
alpha-olefins; or terpolymers of propylene with ethylene and one or
more C.sub.4-C.sub.8 alpha-olefins, containing 0.5-4.5 wt % of
ethylene and 2-6 wt % of C.sub.4-C.sub.8 alpha-olefins, provided
that the total content of ethylene and C.sub.4-C.sub.8
alpha-olefins in the terpolymer is equal to or lower than 6.5 wt %;
and (B) 20-80 wt % of one or more propylene-based components
selected from the group consisting of copolymers of propylene with
one or more C.sub.4-C.sub.8 alpha-olefins, containing from more
than 10 wt % to 30 wt % of C.sub.4-C.sub.8 alpha-olefins, or
terpolymers of propylene with ethylene and one or more
C.sub.4-C.sub.8 alpha-olefins, containing 1-7 wt % of ethylene and
6-15 wt % of C.sub.4-C.sub.8 alpha-olefins. The MFR values of the
precursor composition comprising the same components (A) and (B) in
the above proportions (MFR (1)) is from 0.3 to 5 g/10 min, and the
MFR values (MFR (2)) obtained by subjecting the precursor
composition to degradation a precursor composition is from 2 to 15
g/10 min, with a ratio of MFR (2) to MFR (1) is from 2 to 20.
[0022] A foamed polyolefin composition comprising a reactor made
propylene-based RACO having a melt flow rate between 2 to 15 g/10
min, wherein the MFR values are measured according to ASTM D 1238L.
The propylene-based polyolefin crystalline propylene copolymer
composition having: (A) 0-80 wt % by weight of one or more
propylene-based components selected from the group consisting of
propylene/ethylene copolymers containing 1-7 wt % of ethylene;
copolymers of propylene with one or more C.sub.4-C.sub.8
alpha-olefins, containing 2-15 wt % of the C.sub.4-C.sub.8
alpha-olefins; or terpolymers of propylene with ethylene and one or
more C.sub.4-C.sub.8 alpha-olefins, containing 0.5-4.5 wt % of
ethylene and 2-6 wt % of C.sub.4-C.sub.8 alpha-olefins, provided
that the total content of ethylene and C.sub.4-C.sub.8
alpha-olefins in the terpolymer is equal to or lower than 6.5 wt %;
and (B) 20-100 wt % of one or more propylene-based components
selected from the group consisting of copolymers of propylene with
one or more C.sub.4-C.sub.8 alpha-olefins, containing from more
than 8 wt % to 30 wt % of C.sub.4-C.sub.8 alpha-olefins; and
terpolymers of propylene with ethylene and one or more
C.sub.4-C.sub.8 alpha-olefins, containing 1-7 wt % of ethylene and
6-18 wt % of C.sub.4-C.sub.8 alpha-olefins.
[0023] A foamed polyolefin composition comprising a reactor made
propylene-based RACO having a melt flow rate between 0.3 to 15 g/10
min, wherein the melt flow rate values are measured according to
ASTM D 1238. This RACO can be a crystalline propylene/ethylene
random copolymer having from about 4.5 wt % to about 8 wt % of
ethylene, and from about 92 wt % to about 95.5 wt % of
propylene.
[0024] A foamed polyolefin composition comprising a reactor made
propylene-based RACO having a melt flow rate between 0.3 to 15 g/10
min, wherein the melt flow rate values are measured according to
ASTM D 1238. This RACO can be a crystalline RACO having: (A) 20-60
wt % of a copolymer of propylene with ethylene, wherein the content
of ethylene is about 1 wt % to about 5 wt % of ethylene; and, (B)
40-80 wt % of a terpolymer of propylene with ethylene and a
C.sub.4-C.sub.8 .alpha.-olefin, wherein the content of ethylene is
about 1 wt % to about 5 wt % and the content of the C.sub.4-C.sub.8
.alpha.-olefin is about 7 wt % to 12 wt %. The total content of
ethylene in the RACO is between about 1 wt % to about 5 wt % and
the total content of the C.sub.4-C.sub.8 .alpha.-olefin in the RACO
is between about 2.8 wt % to about 9.6 wt %.
[0025] Any of the above foamed compositions were foamed using a
chemical foaming agent (CFA) or a physical blowing agent (PBA).
[0026] In any of the above foamed compositions, at least one
masterbatch having at least one chemical foaming agent is added to
the reactor made propylene-based RACO or terpolymer resin with high
comonomer content before melting, wherein the carrier resin for the
masterbatch is compatible with at least one polymer or monomer in
the RACO or terpolymer resin.
[0027] In any of the above foamed compositions, the chemical
foaming agent can be an endothermic or exothermic foaming agent,
and/or can act as a nucleating agent,
[0028] In any of the above foamed compositions, at least one
masterbatch having at least one chemical foaming agent and
optionally, at least one nucleating agent is added to the RACO or
terpolymer base resin before melting.
[0029] In any of the above foamed compositions, a physical blowing
agent and a masterbatch containing a nucleating agent are used to
produce the foamed composition.
[0030] In any of the above foamed compositions, the total amount of
combined masterbatches in the foamed composition is 5 wt % or less
of the final composition, or alternatively, between 0.25 and 3 wt %
of the final composition.
[0031] In any of the above reactor made propylene-based RACO or
terpolymer resins, the C.sub.4-C.sub.8 .alpha.-olefin can be
1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene or 1-octene.
[0032] A method of producing any of the above foamable polyolefin
compositions with a chemical foaming agent, the method involving
dry-blending the reactor made propylene-based RACO or terpolymer
resin and masterbatch(s), melting the composition, extruding the
composition through a die, wherein the chemical foaming agent
degrades to release gas, and forming one or more closed cells in
the melted RACO or terpolymer with the released gas. Multiple
chemical foaming agents can be used in this method to release gas
during the extruding step, including the use of a nucleating agent
that also acts as a chemical foaming agent. The extrusion step can
result in a foamed sheet, strand, tube, container, or other
extruded article.
[0033] A method of producing any of the above foamable polyolefin
compositions, using a dry-blending reactor made propylene-based
RACO or terpolymer resin and masterbatch(s), melting the
composition, extruding composition through a die, wherein the
chemical foaming agent degrades to release gas, forming one or more
closed cells in the melted reactor made propylene-based RACO or
terpolymer with the released gas. The density of the foamed reactor
made propylene-based RACO or terpolymer can be up to 70% lower than
an unfoamed reactor made propylene-based RACO or terpolymer with
the same composition, and a range of average cell sizes in the
foamed reactor made propylene-based RACO or terpolymer is between
25 to 40 microns.
[0034] A method of producing any of the above foamable compositions
comprising melting the foamable composition, injecting one or more
physical blow agents into the polymer melt at the extruder, and
extruding composition through a die. The extrusion step can result
in a foamed sheet, strand, tube, container, or other extruded
article. The density of the foamed reactor made propylene-based
RACO or terpolymer can be up to 50% lower than an unfoamed reactor
made propylene-based RACO or terpolymer with the same composition,
and a range of average cell sizes in the foamed reactor made
propylene-based RACO or terpolymer is between 20 to 40 microns.
[0035] A method of producing any of the above foamable compositions
comprising dry-blending a reactor made propylene-based RACO or
terpolymer resin and a masterbatch containing at least one
nucleating agent, melting the foamable composition, injecting one
or more physical blow agents into the polymer melt at the extruder,
and extruding composition through a die. The extrusion step can
produce a foamed sheet, strand, tube, container, or other extruded
article. The density of the foamed reactor made propylene-based
RACO or terpolymer can be up to 50% lower than an unfoamed reactor
made propylene-based RACO or terpolymer with the same composition,
and a range of average cell sizes in the foamed reactor made
propylene-based RACO or terpolymer is between 20 to 40 microns.
[0036] Any of the above methods, wherein the density of the foamed
reactor made propylene-based RACO or terpolymer is about 10 to
about 50% lower than an unfoamed reactor made propylene-based RACO
or terpolymer with the same composition. Alternatively, the density
of the foamed reactor made propylene-based RACO or terpolymer is
about 10 to about 25% lower than an unfoamed reactor made
propylene-based RACO or terpolymer with the same composition.
[0037] Any of the above methods, wherein the range of average cell
sizes in the foamed reactor made propylene-based RACO or terpolymer
is about 10 to about 60 microns, about 10 to about 25 microns, or
about 25 to about 55 microns or about 45 to about 60 microns.
[0038] Any of the above methods, wherein the physical blowing agent
added during the extruding step is injected at about 100-3,000
mL/min, or about 400-1,500 mL/min, or about 500-800 mL/min, or
about 600 mL/min, or about 1,300 mL/min.
[0039] An article comprising any of the above foamed compositions.
Alternatively, an article produced from any of the above
methods.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] FIG. 1 displays a schematic of the Catalloy process. Image
courtesy of LyondellBasell (Houston, Tex.).
[0041] FIG. 2 displays exemplary extrusion process conditions for a
monolayer foamed sheet formed from presently disclosed novel
composition of a RACO or terpolymer and a masterbatch having an
endothermic chemical nucleating and foaming agent.
[0042] FIG. 3A displays the cell size distribution for Adsyl 5C30F
foam strands and FIG. 3B is a histogram of cell size distributions
for Adsyl 5C30F foam strands. Adsyl 5C30F is a commercially
available product from LyondellBasell (Houston, Tex.).
[0043] FIG. 4 displays trends for number of cells and range of cell
sizes for foam sheet samples K17218 and K17219, prepared using
Adsyl 7416XCP. Adsyl 7416XCP is a commercially available product
from LyondellBasell (Houston, Tex.).
[0044] FIG. 5 displays the cell size distribution for multiple RACO
and terpolymer foam monolayer sheets.
DEFINITIONS
[0045] As used herein, the term "copolymer" refers to a polyolefin
that contains two types of alpha-olefin monomer units. It does not
refer to an alloy of two homopolymers.
[0046] As used herein, the terms "comonomer" or "comonomers" refers
to the type or types of monomers that are the minor components in
the polymer chain. As an illustration, the ethylene is the
comonomer in a random copolymer of propylene with ethylene, and
ethylene and butene are the comonomers in a terpolymer of propylene
with ethylene and butene.
[0047] As used herein, the terms "random copolymer" or "RACO"
refers to a polymer that contains two types of monomer units such
that the comonomer units are randomly distributed throughout the
polymer chain.
[0048] As used herein, the term "terpolymer" refers to a polymer
that contains three types of monomer units such that the two types
of comonomer units are randomly distributed throughout the polymer
chain.
[0049] As used herein, the term ".alpha.-olefin" or "alpha-olefin"
means an olefin of the general formula CH2=CH--R, wherein R is a
linear or branched alkyl containing from 1 to 10 carbon atoms. The
.alpha.-olefin can be selected, for example, from 1-butene,
1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, and the
like.
[0050] The term "reactor made" is used to refer to polyolefins that
are made in a reactor system.
[0051] As used herein, the term "base resin" refers to the reactor
made propylene-based RACO or terpolymer resin with high comonomer
content that is being foamed by at least one chemical foaming agent
or at least one physical blowing agent. The phrase "high comonomer
content" means that a monomer other than propylene is present in an
amount of greater than about 5 wt %.
[0052] A "foam" is a continuous three-dimensional network or
cellular structure of a solid or liquid phase, which surrounds a
gaseous phase dispersed therein. In a polymeric foam, such as those
presently disclosed, the solid phase is a polymeric resin, which
forms the cell walls in the continuous "cellular phase". The
"cellular fraction" of the foam is the amount of foam that is in
the cells or the gaseous phase.
[0053] The terms "chemical foaming agent" and "chemical blowing
agent" are used interchangeably to denote chemical compounds that
undergo a decomposition reaction during polymer processing that
results in the production and release of gas. These compounds can
be inorganic or organic, and the decomposition can be endothermic
(need energy to initiate decomposition) or exothermic (release
energy during decomposition). The energy needed to initiate
decomposition can be supplied during processing of the polymer.
[0054] In some embodiments, the at least one chemical foaming agent
can also act as a nucleating agent, and may be referred to as a
"nucleating chemical foaming agent".
[0055] "Physical blowing agents" are distinguishable from chemical
foaming agents because they undergo a change of state during
processing to generate gas. Compressed, liquified gases can be
utilized as physical blowing agent, wherein they are injected into
a polymer melt under high pressure. As pressure is relieved, the
gas becomes less soluble in the melt, resulting in the formation of
cells.
[0056] As used herein, the term "masterbatch" refers to premixed
compositions having one or more solid or liquid additives used to
impart other properties to the base resin. The masterbatches used
in the present foamed compositions can include at least one
chemical foaming agent or at least one nucleating agent or both, as
well as include additives that do not interfere with the base
resin's ability to foam. As masterbatches are already premixed
compositions, their use alleviates issue of insufficient dispersion
of the chemical foaming agent(s) and/or nucleating agent(s).
[0057] The terms "melt flow rate" and "MFR" are used
interchangeably to refer to the measure of the ability of the melt
of the base resin to flow under pressure. The melt flow rate is
determined by ASTM D 1238L ("Standard Test Method for Melt Flow
Rates of Thermoplastics by Extrusion Plastometer") unless otherwise
noted. ASTM D 1238L measures the melt flow rate at 230.degree. C.
and 2.16 Kg of weight. The "melt flow range" is a range of melt
flow rates.
[0058] All concentrations herein are by weight percent ("wt %")
unless otherwise specified.
[0059] The use of the word "a" or "an" when used in conjunction
with the term "comprising" in the claims or the specification means
one or more than one, unless the context dictates otherwise.
[0060] The term "about" means the stated value plus or minus the
margin of error of measurement or plus or minus 10% if no method of
measurement is indicated.
[0061] The use of the term "or" in the claims is used to mean
"and/or" unless explicitly indicated to refer to alternatives only
or if the alternatives are mutually exclusive.
[0062] The terms "comprise", "have", "include" and "contain" (and
their variants) are open-ended linking verbs and allow the addition
of other elements when used in a claim.
[0063] The phrase "consisting of" is closed, and excludes all
additional elements.
[0064] The phrase "consisting essentially of" excludes additional
material elements, but allows the inclusions of non-material
elements that do not substantially change the nature of the
presently disclosed compositions and methods.
[0065] The following abbreviations are used herein:
TABLE-US-00001 ABBREVIATION TERM CBA chemical blowing agent CFA
chemical foaming agent MFR Melt flow rate MB-A Masterbatch A MB-B
Masterbatch B MB-C Masterbatch C MB-D Masterbatch D MB-E
Masterbatch E PBA physical blowing agent PE polyethylene PP
polypropylene RACO Random copolymer SEM scanning electron
microscopy wt % Weight percent
DESCRIPTION OF EMBODIMENTS OF THE DISCLOSURE
[0066] The disclosure provides novel foamable compositions of
reactor made random polypropylene copolymer (RACO) or terpolymer
polyolefins with improved physical properties over currently
available foamed polyolefins. The RACOs and terpolymers used herein
have a high comonomer content of greater than about 5 wt %,
allowing these polyolefins to have a wide range of rigidity, melt
temperatures, and other physical properties, allowing the resulting
foams to be available for a broad variety of applications. For
instance, certain foamed compositions with more rigid copolymers or
terpolymers can be used in the automotive industry for spare tire
packaging, whereas softer, less rigid copolymers or terpolymers can
be foamed for use as shipping materials or food packaging.
Additionally, the foaming agents needed to create the voids in the
foams can be selected to elicit certain cell characteristics in the
copolymers or terpolymers, further increasing the breadth of
applications. Articles produced from the foamable compositions are
also described.
[0067] Any reactor made random copolymer or terpolymer polyolefin
having a propylene monomer as the base and having a high comonomer
content (greater than about 5 wt %) with a final melt flow rate
(MFR) between 0.1 and about 15 g/10 min (per ASTM D 1238L) can be
used per the presently described methods.
[0068] In one aspect, the reactor made propylene-based polyolefin
can be a crystalline copolymer having: (A) 20-80% by weight of one
or more propylene-based components selected from the group
consisting of propylene/ethylene copolymers containing 1-7% of
ethylene; copolymers of propylene with one or more C.sub.4-C.sub.8
alpha-olefins, containing 2-10% of the C.sub.4-C.sub.8
alpha-olefins; terpolymers of propylene with ethylene and one or
more C.sub.4-C.sub.8 alpha-olefins, containing 0.5-4.5% of ethylene
and 2-6% of C.sub.4-C.sub.8 alpha-olefins, provided that the total
content of ethylene and C.sub.4-C.sub.8 alpha-olefins in the
terpolymer is equal to or lower than 6.5%; and (B) 20-80% of one or
more propylene-based components selected from the group consisting
of copolymers of propylene with one or more C.sub.4-C.sub.8
alpha-olefins, containing from more than 10% to 30% of
C.sub.4-C.sub.8 alpha-olefins; terpolymers of propylene with
ethylene and one or more C.sub.4-C.sub.8 alpha-olefins, containing
1-7% of ethylene and 6-15% of C.sub.4-C.sub.8 alpha-olefins. The
MFR values of the precursor composition comprising the same
components (A) and (B) in the above proportions (MFR (1)) is from
0.3 to 5 g/10 min, and the MFR values (MFR (2)) obtained by
subjecting the precursor composition to degradation a precursor
composition is from 2 to 15 g/10 min, with a ratio of MFR (2) to
MFR (1) is from 2 to 20.
[0069] Alternatively, the reactor made propylene-based polyolefin
can be a crystalline copolymer having: (A) 0-80% by weight of one
or more propylene-based components selected from the group
consisting of propylene/ethylene copolymers containing 1-7% of
ethylene; copolymers of propylene with one or more C.sub.4-C.sub.8
alpha-olefins, containing 2-14% of the C.sub.4-C.sub.8
alpha-olefins; or terpolymers of propylene with ethylene and one or
more C.sub.4-C.sub.8 alpha-olefins, containing 0.5-4.5% of ethylene
and 2-6% of C.sub.4-C.sub.8 alpha-olefins, provided that the total
content of ethylene and C.sub.4-C.sub.8 alpha-olefins in the
terpolymer is equal to or lower than 6.5%; and (B) 20-100% of one
or more propylene-based components selected from the group
consisting of copolymers of propylene with one or more
C.sub.4-C.sub.8 alpha-olefins, containing from more than 8% to 30%
of C.sub.4-C.sub.8 alpha-olefins; or terpolymers of propylene with
ethylene and one or more C.sub.4-C.sub.8 alpha-olefins, containing
1-7% of ethylene and 6-18% of C.sub.4-C.sub.8 alpha-olefins. The
melt flow rate of this copolymer can be between 2.0 and 15.0 g/10
min.
[0070] Alternatively, the reactor made propylene-based polyolefin
can be a RACO having a crystalline propylene/ethylene random
copolymer having from about 4.5 wt % to about 8 wt % of ethylene,
and from about 92 wt % to about 95.5 wt % of propylene. The melt
flow rate of this copolymer can be between 0.3 and 15.0 g/10
min.
[0071] In yet another alternative, the reactor made propylene-based
polyolefin can be a reactor made propylene-based RACO having: (A)
20-60% of a copolymer of propylene with ethylene, wherein the
content of ethylene is about 1 wt % to about 5 wt % of ethylene;
and, (B) 40-80% of a terpolymer of propylene with ethylene and a
C.sub.4-C.sub.8 .alpha.-olefin, wherein the content of ethylene is
about 1 wt % to about 5 wt % and the content of the C.sub.4-C.sub.8
.alpha.-olefin is about 7 wt % to 12 wt %. The total content of
ethylene in the RACO is between about 1 wt % to about 5 wt %, and
the total content of the C.sub.4-C.sub.8 .alpha.-olefin in the RACO
is between about 2.8 wt % to about 9.6 wt %. The melt flow rate of
this copolymer can be between 0.3 and 15.0 g/10 min.
[0072] All of the random copolymers and terpolymers described above
are exemplary and show the wide variation in the formulations that
allows for the broad use of the reactor made RACO and terpolymer
polyolefin resins, and the foamed extrudates in the present
disclosure. In addition to the random copolymers and terpolymer
formulas above, the polyolefins for the current compositions can
also include any of the formulas described in EP0674991, EP1025162,
and U.S. Pat. No. 6,395,831, each of which is incorporated herein
in its entirety for all purposes. The polyolefins can also be
prepared by any of the reactor processes described in EP0674991,
EP1025162, and U.S. Pat. No. 6,395,831 as well.
[0073] In yet more embodiments, the random copolymers or terpolymer
is prepared using a multi-stage gas phase polymerization process.
In some embodiments, the multi-stage gas phase polymerization
process is the Catalloy process from LyondellBasell (Houston,
Tex.). The Catalloy process, shown in FIG. 1, utilizes a unique
combination of catalysts, two or three independent fluidized bed
reactors, and multiple monomer capability to expand the performance
of the resulting polyolefins by delivering new functionalities. The
Catalloy process can make a random copolymer or terpolymer in each
gas phase reactor, creating an alloy of copolymers and/or
terpolymers while in the reactors. This process allows for the
incorporation of higher amounts of comonomer into the polyolefin,
including two different comonomers in the same reactor, compared to
conventional polypropylene production processes. The high comonomer
content, as well as the presence of multiple comonomers, translates
to a new combination of thermal, physical and optical properties
for the resulting RACOs or terpolymers. The benefits of using the
Catalloy-produced copolymers and terpolymer include the ease of
processing, ability to make resins with a wide range of polymer
compositions, and unique thermal properties including, but not
limited to, low seal initiation temperature. As such, commercially
available Catalloy polymers from LyondellBasell (Houston, Tex.) can
be used in the present compositions as the base resin for the
foams, including Adsyl products.
[0074] To create a foamed cellular structure using any of the
above-described reactor made propylene-based RACOs or terpolymers,
each base resin can be mixed with a chemical foaming agent or a
physical blowing agent, and an optional nucleating agent.
[0075] The reactor made RACO or terpolymer base resins can be
combined with at least one chemical foaming agent (CFA). The
chemical foaming agents that are acceptable for use with the
present disclosure develop gas in the resin by way of thermal
decomposition or chemical reactions. In some embodiments, the CFA
decomposes during the extrusion process to produce and release a
gas into the extruding polymer to foam the resin. To ensure proper
dispersion of the CFAs, the CFAs are in a masterbatch that uses a
carrier resin that is compatible with at least one polymer or
monomer in the polyolefin base resin, such as ethylene or
propylene. This allows for the CFAs to create consistent cells
morphologies with controlled size distributions throughout the
extruded and foamed reactor made propylene-based RACO or terpolymer
resins.
[0076] Many CFAs are known in the art and/or are commercially
available. Exemplary organic CFAs include azo and diazo compounds
(e.g. azodiacarbonamides), hexahydrophthalic acid and hydrazines,
including their salts and anhydrides (e.g. sulfonylhydrazides or
triazines), N-nitroso compounds, azides, sulfonyl semicarbazides,
triazoles and tetrazoles, urea derivatives, guanidine derivatives,
and esters. Exemplary inorganic CFAs include ammonium carbonate,
and carbonates of alkali metals, including sodium bicarbonate and
citric acid. The CFAs can also include mixtures of acids and
metals, mixtures of organic acids with inorganic carbonates,
mixtures of nitrites and ammonium salts.
[0077] At least one optional nucleating agent may also be combined
with the CFA(s). In some embodiments, at least one CFA is present
in the same masterbatch comprising the optional nucleating agent,
or at least one CFA is present in a separate masterbatch, or the at
least one CFA acts as the nucleating agent. Nucleating CFAs help
with property enhancement, improved molding or extrusion
productivity, and increased transparency for many polyolefins. In
masterbatches with nucleating agents and multiple CFAs, at least
one CFA can be the nucleating agent. Alternatively, any or all of
the CFAs used in the present composition can be nucleating.
Further, one or more of the CFAs in the masterbatch can be
endothermic such that it does not decompose in the reactor made
propylene-based RACO or terpolymer resin until the extrusion
process. This is because endothermic CFAs need heat to activate
that is provided by the extrusion process.
[0078] In other aspects of the present disclosure, multiple
masterbatches can be mixed with the reactor made propylene-based
RACO or terpolymer resin to achieve the desired cell morphology of
the resulting foam. The final concentration of the masterbatch in
the foamed resin may be limited to 5% of the weight of the foamed
resin. Alternatively, the final concentration of the masterbatch in
the foamed resin may be between 0.25 and 3 wt %.
[0079] Reactor made propylene-based RACO or terpolymer resins have
a wide range of physical properties, which lead to flexible
formulations when mixed with select CFAs to achieve specific cell
size, cell distributions and cell stabilities. This combination
allows for the composition to be fine-tuned to form a foam
structure with enhanced stability and performance characteristics.
Thus, the resulting foams can then have a wide range of physical
properties, density reduction, cell size, cell pattern, and/or cell
stability. This allows the foams to be available for a variety of
applications in the e.g. automobile, shipping, food packaging
industries, and the like.
[0080] The CFAs can be chosen to produce large (above 150 microns
in diameter) or small cell sizes (below 120-150 microns in
diameter), and a wide or narrow distribution of cell sizes. In some
applications, narrow distributions of cell sizes are desirable. In
some embodiments, the desired cell sizes are in a range of 25-55
microns, as these foams can be classified as fine-celled foams.
However, the desired cell density will depend on the application
for the foam. For instance, low cell density foams are more
flexible and are better for many applications such as thermal
insulation and comfort (e.g. furniture and car seating) but high
cell density can be used for more rigid foams, such as
energy-absorbing application, pipes, appliances, food and drink
containers. Since the mechanical strength of a polymer foam can be
proportional to the foam density, the application of the foam
dictates the range of foam density to be produced.
[0081] In addition to cell size and density, the CFAs can be chosen
to achieve certain flexibility in the resulting foamed
extrudate.
[0082] Alternatively, the reactor made RACO or terpolymer base
resin, in melt form, can be combined with a physical blowing agent
such as CO.sub.2, N.sub.2, isobutane, or CFC-derivatives, and
foamed. The process conditions for the blowing agents are
controlled to tune the cellular phase, cell size, and other cell
features of the resulting foam.
[0083] When using PBAs, the reactor made RACO or terpolymer base
resin can also optionally be combined with a masterbatch having at
least one nucleating agent. The PBA and the nucleating agent work
synergistically to achieve desired cell morphology, including both
large (above 150 microns in diameter) or small cell sizes (below
120-150 microns in diameter), and a wide or narrow distribution of
cell sizes. As above, the final concentration of the masterbatch's
in the foamed resin may be limited to 5% of the weight of the
foamed resin. Alternatively, the final concentration of the
masterbatch in the foamed resin may be between 0.25 and 3 wt %.
[0084] Articles of various shapes and sizes can be formed using
foamed compositions comprising any of the reactor made RACO or
terpolymer base resin presently disclosed.
[0085] The presently disclosed base resin compositions are
exemplified with respect to the disclosure below. However, these
are exemplary and the methods can be broadly applied to any reactor
made propylene-based RACOs and terpolymers base resin with a high
comonomer content, and chemical foaming agent or physical blowing
agents.
[0086] The following description demonstrates various embodiments,
and is intended to be illustrative, and not unduly limit the scope
of the appended claims. Those of skill in the art should appreciate
that many changes can be made in the specific embodiments which are
disclosed and still obtain a like or similar result without
departing from the spirit and scope of the disclosure herein. In no
way should the following be read to limit, or to define, the scope
of the appended claims.
[0087] Base polymer: A series of commercially available Catalloy
random copolymer and terpolymer resins with high comonomer content
from LyondellBasell, (Houston, Tex.) were extruded with a foaming
agent, foamed, and analyzed per the methods described below. The
examples utilized resins from the Adsyl product line. These base
polymer resins were chosen as they have a wide range of comonomer
type and content which translates into large number of potential
applications. Further, these resins have moderate melt elasticity
and melt strength, which is desirable for foam production.
[0088] The Adsyl product line includes propylene-based terpolymers
formed by polymerizing propylene with a high ethylene and butene
comonomer content. These polymers have superb sealing properties,
good opticals, a broad operating window, and are suitable for
metallization. They are also compatible with PE and PP.
Additionally, the Adsyl product line also has RACO copolymers with
either high ethylene or high butene content.
[0089] Together, this selection of commercially available resins
provides a broad scope of thermal, physical and optical properties
for investigating the applicability of the proposed methods.
[0090] Chemical foaming agents: A series of commercially available
masterbatches containing at least one chemical foaming agent were
obtained for combination with a propylene-base polymer. Masterbatch
A (MB-A) contains an endothermic chemical nucleating and foaming
agent used in a concentration of 1.5-2.25 wt %. The CFA in MB-A is
also used for the creation of cells to reduce density and improve
throughput in medium density extrudate. Masterbatch B (MB-B)
contains an olefinic nucleating agent that was used in a
concentration of 0.75-1.0 wt %. The CFA in MB-B is used to improve
cell dispersion, size and uniformity in extrusion processes
producing chemical foam. Masterbatch C (MB-C) contains an
endothermic/exothermic blended chemical foaming agent in a
concentration of 1 wt %. The CFA in MB-C is used for both injection
molding and extrusion applications to create cells in medium
density extrudate. Masterbatch D (MB-D) contains a chemical foaming
agent at a concentration of 2.5 wt %. Masterbatch E (MB-E) contains
a nucleating agent used at a concentration of 1 wt % and was
combined with one of the other masterbatches described above having
a CFA.
[0091] A masterbatch with at least one CFA was mixed with the
resins before being extruded and foamed. The use of one nucleating
chemical foaming agent is sufficient to foam the chosen base
polymer, but mixes of chemical foaming agents may be desired to
fine-tune the characteristics of the foamed extrudate.
[0092] Unless otherwise noted, the selected masterbatches were dry
blended with the base resin before the melt stage.
[0093] CFA Foam Extrusion: A variety of sample compositions with
CFAs were prepared and extruded as foamed strands for an initial
analysis. The base polymer and masterbatches were dry blended and
extruded without modifications to the extrusion equipment or the
resin grade. The foam strand samples were then analyzed for
cellular phase, cell size, and other cell features.
[0094] From the characterization results of the foam strands,
certain sample compositions with CFAs were extruded as sheets. For
the sheets, the base polymer and masterbatches were dry blended and
extruded as multi-layer sheets (Mode 2) to produce foamed sheets
that were about 40 mm thick. Certain foam sheet samples underwent
further analysis for density, density reduction compared to the
base polymer alone, cell size, and other cell features.
[0095] No modifications to the extrusion equipment or the resin
grade were needed to produce the sample foamed sheets. FIG. 2
displays exemplary process conditions for the extrusion of a foamed
sheet in this case a monolayer foamed sheet sample using the
Masterbatch A. These conditions did not significantly vary for the
different foamed sheets. The dashed box in FIG. 2 highlights Barrel
Zone 2, which uses a higher temperature than Barrel Zones 1 and 3,
to activate the chemical foaming agent.
[0096] Foam Characterization: Morphological characterization of the
cellular structure of the foamed Catalloy extrudates were
determined by optical microscopy and scanning electron microscopy
(SEM). Foam samples were cryo-microtomed in the direction
perpendicular to extrusion using a Leica MZ6 Ultramicrotome with a
diamond knife at -40.degree. C. The thin cross-sections were
examined by optical microscopy (Olympus BX51 Compound Microscope)
with both transmitted light and cross-polarized light. The bulk
cross-sections were examined using an SEM (Hitachi S-3500N or
SU8230) in high vacuum mode at accelerating voltage of 5 kV. SEM
images were captured at the same low magnification (25.times.) to
allow for the whole extrudate cross-section of each sample to be
included in a single image. Prior to SEM imaging, the bulk
cross-section specimens were coated with Pt using a sputter coater
(Emitech K550X) to eliminate charging from SEM electron beam.
[0097] Olympus Stream Essentials image software was employed to
perform image analysis on SEM images where the cells displayed as
dark holes are dispersed in the lighter polymer matrix. For this
type of cellular morphology, the particle analysis function of the
software is the most suitable means to measure the size and number
of cells in each foam cross-section. To ensure accurate results,
prior to image analysis, each SEM image was examined and manually
corrected using Adobe Photoshop software to enhance the contrast
between the cells and the solid phase. The gray value thresholds
that distinguish cells from the solid phase in image analysis were
adjusted based on each individual image so that the greatest number
of cells were counted. To ensure consistency, no further manual
editing of image detection was conducted after automatic image
analysis by Stream Essentials software. The average cell size or
radius, cumulative cell area distribution, and morphology of the
cells (open or closed) were determined from the images.
[0098] Density measurements were made according to the standard
test methods established in ASTM D792-13 using displacement by
water or alcohol. The reduction in density was calculated based on
the density of the base polymer for each example without any
foaming agents added.
CFA Foamed Strands
[0099] Foamed strands of Adsyl 5C30F were prepared using CFAs, and
analyzed for the largest reduction in density compared to the
unfoamed resin and the smallest cell size. The compositions and
results for the preliminary samples are shown in Table 1.
TABLE-US-00002 TABLE 1 Preliminary compositions for foamed strands
NOMINAL DENSITY of CELL SOLID DENSITY DENSITY OF DIAMETER
POLYOLEFIN REDUCTION EXAMPLE FOAM (g/cm.sup.3) (microns)
(g/cm.sup.3) PERCENT Terpolymer Adsyl 5C30F, 2% Masterbatch A 0.50
240 0.90 44% Adsyl 5C30F, 1.5% Masterbatch A 0.55 275 0.90 39%
Adsyl 5C30F, 1.5% Masterbatch 0.51 130 0.90 43% A, 1% Masterbatch B
Adsyl 5C30F, 1.5% Masterbatch 0.54 165 0.90 40% A, 1% Masterbatch E
Adsyl 5C30F, 1% Masterbatch C 0.40 400 0.90 56% Adsyl 5C30F, 1%
Masterbatch 0.36 335 0.90 60% C, 1% Masterbatch B Adsyl 5C30F, 1%
Masterbatch 0.43 305 0.90 52% C, 1% Masterbatch E
[0100] The Adsyl 5C30F samples with 1.5% MB-A combined with 1% of
MB-B or MB-E in Table 1 were chosen for additional
characterization, including image analysis. The results for the
addition analysis are shown in Table 2.
TABLE-US-00003 TABLE 2 Characterization of select foamed strands
Average Relative Cellular Fraction of Cell Average Standard Strand
Foam Strand MB-A MB-B MB-E Phase Cellular Cell Diameter Cell area
Deviation Diameter Sample No. Polyolefin (wt %) (wt %) (wt %)
(.mu.m.sup.2) Phase (%) Count (.mu.m) (.mu.m.sup.2) (%) (.mu.m)
S-2017- Adsyl 1.5 1 2463464.07 41.60 333 97.05 7397.79 157.69
2745.99 005158 5C30F S-2017- Adsyl 1.5 1 2174788.98 36.61 273
100.71 7966.26 137.87 2750.24 005159 5C30F
[0101] From the image analysis, the selected extruded strands in
Table 2 were found to have circular cross-sections, with diameter
measurements in the 2.75 mm range. These foamed compositions show
slight variations in rigidity and size, reflecting different
foaming agent compositions and levels of foam expansion.
[0102] All of the optical images were taken with the lowest
possible magnifications from the microscope so the largest areas of
the foam cross-sections can be included. The cellular morphology
varied from strand sample to strand sample. In general, the cell
sizes were smaller near the strand surface where the polymer melts
experience the higher shear forces during processing. The sizes of
the cells gradually increase with the distance from the surface.
Near the core, many small cells appeared to aggregate to form a
large cell of an irregular shape due to the low shear force of the
polymer melt, making it incapable of dispersing individual cells
during either the initial bubble formation, or due to the high
extensional force of the melt causing the cell rupture during cell
growth. In some samples, the observed larger cells may be a result
of the disappearance of cell walls that separate individual cells.
However, cell walls tend to collapse because they are too thin to
withstand low temperature microtoming that is used to prepare the
samples for analysis.
[0103] SEM was used to confirm the variations of cell sizes with
the distance from the strand surface and to observe the cell
aggregations. Some of the aggregates formed clusters of cells with
the existence of solid walls between neighboring cells. Others
formed larger cell aggregates of irregular shapes. Many of the
cells in the foam strand samples were non-spherical. A foaming
polymer melt tends to be stable when the gas bubbles were strictly
spherical in shape to minimize the interfacial area and the
capillary pressure; however, the bubbles become elongated in the
extrusion direction, resulting in the non-uniform distribution of
the mechanical stresses during foaming. The gas bubbles would tend
to expand along the directions of minimum local stress to produce
the anisotropic shapes of cells. In addition, the degree of freedom
is higher in the extrusion direction during foaming because it has
less geometric constraints.
[0104] The SEM images did not show the enclosure of these
hemispherical cells. Although SEM images can show individual cells
within the large cell aggregates that are connected to each other,
there is no morphological evidence to characterize any of these
foam samples as open-cell foam in overall view.
[0105] Cells were not uniformly dispersed in the solid polymer. For
this type of foam, cell size analysis provides comprehensive and
valuable characteristics of foam structures to differentiate
various foam samples. Some morphological parameters, such as wall
thickness and cell packing geometry, were not measurable or
meaningful.
[0106] Table 2 lists results of cell counts, average cell sizes,
and relative standard deviations obtained by Stream Essentials
image software through particle analysis. The sizes of cellular
phase and area fractions of cellular phase were calculated based on
these results and measured strand diameters. The cell phase area
fractions for these samples are below 42%.
[0107] The use of Masterbatch C appeared to achieve the largest
reduction in the resin's density, with a reduction of 52% or
higher, whereas Masterbatch A had a range between 39 and 44%.
[0108] The cell size, however, was smallest when combining
Masterbatch A with a second Masterbatch, showing cell size as low
as 130 microns in diameter. These results illustrate the
fine-tuning of the foaming agents in the masterbatches to elicit
desired properties from each base polymer. As shown in Table 2, the
average cell sizes fall within the range of about 97 to 100 .mu.m
of the equivalent diameter, thus they are classified as
small-celled foams.
[0109] The results of cell size measurements were further analyzed
for size distribution. As displayed in FIG. 3A (cumulative number
of cells vs. cell radius) and FIG. 3B (cell size histograms), and
also shown in Table 2, these foam strand samples are not symmetric.
The curves in FIG. 3A indicate that the foaming agent composition
is the source of major differences in cell formation. The range of
variations within each pair of foams produced from the same resin
was relatively broad. The cell dimension detected most frequently
in each foam sample is in the smallest particle size range. This
type of particle size distribution results in a relatively high
standard deviation in cell size measurements.
[0110] In conclusion, the base resins used in the strand examples
were able to form foam. This foamability was unexpected for two
reasons. First, reactor made propylene-based RACO and terpolymers
such as Adsyl base resins are not heterophasic copolymers with a
semi-crystalline matrix component and a partially amorphous
bipolymer component. These two components were considered to be
necessary to form a foam. However, the present examples show that
both components are not needed. Second, the reactor made
propylene-based RACO and terpolymer base resin used in the present
compositions have a lower melt strength when compared to
polyolefins with a high molecular weight bipolymer component. A
high melt strength is needed to foam polyolefins, thus making these
polymers poor foaming candidates. However, the present compositions
were capable of producing foamed strands. Further, the selected
foamed strands compositions were small-celled foams that had
smaller cells seen near the surface while larger cells of irregular
shapes are located near the core. It is generally known in the art
that small cell structures tend to have a smaller negative impact
on mechanical properties than large cell structures. The density
reductions were up to 70% when compared to the base resin.
[0111] These results show that not only are the Catalloy reactor
made RACO and terpolymers polyolefins with high comonomer content
capable of being foamed but that the character of the foams (e.g.
cell size, density reduction, etc) can be tuned by the choice of
chemical foaming agent(s) and/or the addition of one or more
nucleating agents. Further, due to the breadth of possible
applications for foamed polyolefins, perceived "imperfections" for
certain applications, such as the foamed strands with inconsistent
cells sizes, can still find many uses.
CFA Foamed Sheets
[0112] Based on the results from the foamed strand tests,
additional Adsyl grades were used to prepare CFA foamed sheets. The
compositions were foamed as either single layer sheets (mode 1) or
as multi-layered sheets (mode 2). Like the foamed strands,
Masterbatch A and Masterbatch B were utilized for the CFA foamed
sheets. The foam sheets were produced by dry-blending a combination
of Masterbatch A and Masterbatch B with the selected base Adsyl
resin, and extruding with an 8-inch flat die to prepared foam
sheets with a target thickness of 40 mil (about 1 mm).
[0113] The compositions of each CFA foamed sheet of different Adsyl
grades, and the results of the density testing according to ASTM
D792, are shown in Tables 3 and 4. Table 3 displays the results for
the multilayer samples (Mode 2), with FIG. 4 showing the cumulative
cell area distribution for the each composition, with the density
labeled. The results for the monolayer samples (Mode 1), are given
in Table 4 and FIG. 5.
TABLE-US-00004 TABLE 3 Exemplary Adsyl foamed sheets Density
Average Sample MB-A MB-B Density reduction Density Cell radius No.
(wt %) (wt %) Mode (g/cm.sup.3) (%) (lb/ft.sup.3) (microns) Adsyl
7416XCP Unfoamed 0 0 -- 0.900 -- 57 -- Control K17218 1.75 0 2
0.7154 21 44.7 15 K17219 1.75 0.75 2 0.7086 21 44.2 18
[0114] The chemical foaming agents were able to reduce the density
for each of the tested base polymers resins. A good range of
reduction, up to about 25%, was experienced with these foamed sheet
samples.
[0115] Table 3 displays the results using Adsyl 7416XCP that was
extruded as a multilayer sheet. Sample No. K17218 produced foam
with a density of 44.7 lb/ft3, a 21% reduction. Sample No. K17219
used the same concentration of Masterbatch A but added 0.75 wt % of
Masterbatch B. This composition resulted in a comparable density
reduction of 21%, too. Average cell radius for Example No. K17218
was 15 microns while Example No. K17219 attained a cell radius of
18 microns.
[0116] Additional examples using Adsyl 7416XCP were foamed as
single layer sheets. The results in Table 4 show how changes in the
Masterbatch compositions and/or concentrations can affect the
features of the foam. Example No. K19011 had the same masterbatch
composition as No. K17219, and similar results were seen between
Mode 1 and 2. However, increasing the content of Masterbatch A for
Example No. K19012 increased the density reduction by about 6%.
Thus, the concentration of Masterbatch A appears to have a greater
influence on the density reduction for Adsyl 7416XCP foams. Similar
results were seen with the Adsyl 5C30F foams, wherein the addition
of Masterbatch B did not increase the density reduction.
TABLE-US-00005 TABLE 4 Exemplary Adsyl foamed sheets Foam Solid
Density Average Cell Sample MB-A MB-B Density Density reduction
Density Diameter No. (wt %) (wt %) Mode (g/cm.sup.3) (g/cc) (%)
(lb/ft.sup.3) (microns) Adsyl 5C30F K19013 1.5 0 1 0.8007 0.9 11 50
28 K19014 1.5 0.75 1 0.8063 0.9 10 50 29 K19015 2.25 0.75 1 0.7019
0.9 22 44 28 Adsyl 6C30F K19007 1.5 0 1 0.8084 0.9 10 50 25 K19008
1.5 0.75 1 0.7438 0.9 17 46 27 K19009 2.25 0.75 1 0.668 0.9 26 42
28 Adsyl 3C30F-HP K19016 1.5 0 1 0.7988 0.9 11 50 36 K19017 1.5
0.75 1 0.784 0.9 13 49 33 K19018 2.25 0.75 1 0.7589 0.9 16 47 24
Adsyl 7416XCP K19011 1.75 0.75 1 0.7286 0.9 19 45 26 K19012 2.25
0.75 1 0.6726 0.9 25 42 28
[0117] As explained above, the Adsyl resins are not heterophasic
copolymers with a semi-crystalline matrix component and a partially
amorphous bipolymer component. Second, the reactor made RACO and
terpolymers do not have long chains or high molecular weight
component. As such, these polyolefins have a lower melt strength
when compared to polyolefins with these features. Thus, these
resins were considered a poor choice for foaming. However, based on
the foaming results obtained from the initial examples, different
grades of this reactor made random copolymers and terpolymers were
mixed with varying combinations of masterbatches and foamed as
monolayer sheets. The results in Table 4 illustrate how the
different grades of these reactor made random copolymers and
terpolymers unexpectedly foamed with changes to the
masterbatches.
[0118] The foamed compositions produced using Adsyl 6C30F as a base
resin displayed an increase in cell size radius as the amount of
Masterbatch A increased, as did Adsyl 7416XCP. In contrast, Adsyl
3C30F-HP displayed a decrease in cell radius with increasing
Masterbatch A. The Adsyl grades showed density reduction as the
amount of Masterbatch A increased and as Masterbatch B was
added.
[0119] As before, SEM was used to confirm the variations of cell
sizes with the distance from the monolayer surface of the exemplary
sheets in Table 4, and to observe the cell aggregations. Some of
the aggregates formed clusters of cells with the existence of solid
walls between neighboring cells. Others formed larger cell
aggregates of irregular shapes. Many of the cells in the foam
monolayer samples were non-spherical due to becoming elongated
during the extrusion process.
[0120] The cell diameters were also reduced down to about 25-55
microns, thus these foams can be classified as small-celled foams.
Further, each sample was predominantly closed-cell foams as the
foam cells are isolated from each other and cells are surrounded by
complete cell walls. This desirable feature is helpful in selecting
applications for the foamed compositions. The foam samples also
showed variations of cell size and shape with the distance from the
foam surface. Smaller cells were seen near the surface while larger
cells of irregular shapes were located near the core, suggesting
that the foam structure depends strongly on the rheological
behavior of the base resin and the equipment used for foaming.
[0121] The results from each of the foam samples demonstrate that
multiple Adsyl grades can be successfully foamed as sheets or
strands using chemical foaming agents. Similarly, foaming abilities
with PBAs, with and without nucleating agents, are expected to be
equally successful. The foamed extrudates displayed a large range
of properties, allowing for a broad amount of applications.
Further, the selection of chemical foaming agents or combinations
thereof, and nucleating agents, can be utilized to tune the
features of the foam extrudate for select applications.
Additionally, it was noted that the foaming of the different
reactor made random copolymers and terpolymers did not need
modification to the hardware of the system, which could reduce down
time and capital costs.
[0122] The following references are incorporated by reference in
their entirety.
[0123] ASTM D792-13, Standard Test Methods for Density and Specific
Gravity (Relative Density) of Plastics by Displacement
[0124] ASTM D 1238L, Standard Test Method for Melt Flow Rates of
Thermoplastics by Extrusion Plastometer
[0125] EP0674991
[0126] EP1025162
[0127] U.S. Pat. No. 6,395,831
* * * * *