U.S. patent application number 09/728128 was filed with the patent office on 2001-05-03 for laminated foam structures with enhanced properties.
Invention is credited to Bambara, John D., Bambara, Richard, Smith, Scott C., Smith, Thomas W..
Application Number | 20010000568 09/728128 |
Document ID | / |
Family ID | 27102037 |
Filed Date | 2001-05-03 |
United States Patent
Application |
20010000568 |
Kind Code |
A1 |
Bambara, John D. ; et
al. |
May 3, 2001 |
Laminated foam structures with enhanced properties
Abstract
The invention relates to foam structures with enhanced physical
properties which can be used in the areas of packaging, athletics,
water sports, and construction. In general, the structures are
laminated polymer foams that include a core of a low density foam
and one or more skins of relatively high density foam covering the
core. The skins provide improved physical properties to the foam
structures by improving the flexural strength, resistance to
bending, and resulting damage from bending in the laminated foam
structure while modestly increasing the weight of the laminated
structure, for example. Uses of the foam structures include, but
are not limited to, packaging materials, gym mats, body boards, or
eaves fillers. The skin can act as a hinge to fold a die cut piece
into a collapsible packaging system.
Inventors: |
Bambara, John D.;
(Osterville, MA) ; Bambara, Richard; (Cooperstown,
NY) ; Smith, Scott C.; (Osterville, MA) ;
Smith, Thomas W.; (Austin, TX) |
Correspondence
Address: |
Richard P. Crowley
901 Main Street
P.O. Box 901
Osterville
MA
02655
US
|
Family ID: |
27102037 |
Appl. No.: |
09/728128 |
Filed: |
November 30, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09728128 |
Nov 30, 2000 |
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09167200 |
Oct 6, 1998 |
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6167790 |
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09167200 |
Oct 6, 1998 |
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08706722 |
Sep 6, 1996 |
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5876813 |
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08706722 |
Sep 6, 1996 |
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08678513 |
Jul 9, 1996 |
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5882776 |
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Current U.S.
Class: |
83/701 ; 156/77;
428/218; 428/316.6 |
Current CPC
Class: |
B32B 5/32 20130101; Y10T
428/233 20150115; B32B 5/18 20130101; B65D 5/509 20130101; B32B
2307/72 20130101; Y10T 83/04 20150401; B32B 2266/025 20130101; Y10T
428/1376 20150115; Y10T 83/0333 20150401; Y10T 83/97 20150401; Y10T
83/02 20150401; Y10T 428/249981 20150401; Y10T 428/2419 20150115;
Y10T 428/24992 20150115; Y10T 428/249953 20150401; B32B 2307/546
20130101; B32B 7/02 20130101; B32B 2305/022 20130101; Y10T 83/0524
20150401 |
Class at
Publication: |
83/701 ;
428/316.6; 428/218; 156/77 |
International
Class: |
B32B 003/00; B32B
003/26; B32B 005/18 |
Claims
What is claimed is:
1. A laminated foam structure comprising a first article laminated
to a first surface of a second foam article, wherein the first
article is a first foam article having an average foam density that
is at least 1.5 times greater than the average foam density of the
second foam article and a volume that is at least 1.5 times smaller
than the volume of the second foam article.
2. The laminated foam structure of claim 1, wherein the first foam
article is a skin having an average foam density of between about 2
and 18 pounds per cubic foot and a thickness less than {fraction
(5/16)}inch, and the second foam article is a core having an
average density of between about 1 and 6 pounds per cubic foot and
a thickness of between 1 and 14 inches.
3. The laminated foam structure of claim 2, wherein the first foam
article includes at least two laminated foam articles.
4. The laminated foam structure of claim 3, wherein each of the
foam articles has an average foam density of less than 3 pounds per
cubic foot and the core thickness is between 1 and 5 inches.
5. The laminated foam structure of claim 4, wherein the second foam
has an average foam density greater between 10 and 12 pounds per
cubic inch and a thickness of between {fraction (1/16)}and
1/8inch.
6. The laminated foam structure of claim 5, wherein the foam
comprises a polyolefin.
7. The laminated foam structure of claim 6, wherein the polyolefin
includes a polyethylene or polypropylene.
8. The laminated foam structure of claim 7, wherein the foam
further comprises a single-site initiated polyolefin resin.
9. The laminated foam structure of claim 8, wherein at least a
portion of the foam is cross-linked.
10. The laminated foam structure of claim 9, wherein the laminated
foam structure is heat laminated.
11. The laminated foam structure of claim 1, further comprising a
third foam article laminated to a second surface of the second foam
article, the third foam article having an average foam density that
is at least 1.5 times greater than the average foam density of the
second foam article and a volume that is at least 1.5 times smaller
than the volume of the second foam article, wherein the laminated
foam structure has a flexural stiffness that is between 2 and 20
times greater than said second foam article alone.
12. The laminated foam structure of claim 11, wherein the second
foam article is a laminated foam article including at least two
foams each having an average foam density of less than 4 pounds per
cubic foot.
13. The laminated foam structure of claim 12, wherein the first
foam article and the third foam article each have an average foam
density of between about 4 and 15 pounds per cubic foot.
14. The laminated foam structure of claim 13, wherein the second
foam article has an average foam density of between 1 and 3 pounds
per cubic foot, the first foam article has an average foam density
of between about 4 and 12 pounds per cubic foot, and the third foam
article has an average foam density of between about 4 and 12
pounds per cubic foot.
15. The laminated foam structure of claim 13, wherein the second
foam article further includes a foam layer having an average foam
density greater than about 4 pounds per cubic foot.
16. The laminated foam structure of claim 13, wherein the first
foam article and the third foam article each are laminated foam
articles including two foams each having an average foam density of
greater than 4 pounds per cubic foot.
17. The laminated foam structure of claim 11, wherein the foam
comprises a polyolefin.
18. The laminated foam structure of claim 17, wherein the
polyolefin is a polyethylene or polypropylene.
19. The laminated foam structure of claim 18, wherein the foam
further comprises a single-site initiated polyolefin resin.
20. The laminated foam structure of claim 11, wherein at least a
portion of the foam is cross-linked.
21. The laminated foam structure of claim 11, wherein the structure
has a total thickness between about 3/4and 12 inches.
22. The laminated foam structure of claim 11, wherein the first
foam article and the third foam article each have a thickness
between about {fraction (1/16)}and {fraction (5/16)}inches.
23. The laminated foam structure of claim 11, wherein the two foams
each have a thickness between about 1/4and 1 inches.
24. The laminated foam structure of claim 15, wherein the foam
layer has an average foam density between 4 and 15 pounds per cubic
foot and a thickness between about {fraction (1/16)}and
1/2inches.
25. A laminated foam structure comprising a first skin laminated to
a first surface of a core, wherein the core includes a first foam
having an average foam density of between about 1 and 6 pounds per
cubic foot, the first skin includes a second foam having an average
foam density of between about 3 and 18 pounds per cubic foot and a
thickness less than 1/2inches, and the laminated foam structure has
a total thickness of less than about 12 inches.
26. The laminated foam structure of claim 25, further comprising a
second skin laminated to a second surface of the core, wherein the
second skin includes a third foam having an average foam density of
between about 3 and 18 pounds per cubic foot and a thickness less
than 1/2inches, and said laminated foam structure has a flexural
stiffness that is between 2 and 20 times greater than said core
alone.
27. The laminated foam structure of claim 26, wherein the first
foam includes at least two laminated foam articles.
28. The laminated foam structure of claim 26, wherein the second
foam includes at least two laminated foam articles.
29. The laminated foam structure of claim 26, wherein the third
foam includes at least two laminated foam articles.
30. The laminated foam structure of claim 27, wherein each of the
foam articles has an average foam density of between 1 and 4 pounds
per cubic foot and a thickness of between 1/4and 1 inches.
31. The laminated foam structure of claim 27, wherein the first
foam further includes a foam layer having an average foam density
greater than about 4 pounds per cubic foot and a thickness less
than 1/2inch.
32. The laminated foam structure of claim 26, wherein the foam
comprises a polyolefin.
33. The laminated foam structure of claim 32, wherein the
polyolefin is a polyethylene or polypropylene.
34. The laminated foam structure of claim 33, wherein the foam
further comprises a single-site initiated polyolefin resin.
35. The laminated foam structure of claim 26, wherein at least a
portion of the foam is cross-linked.
36. A method of increasing the flexural stiffness of a core foam
structure comprising the steps of: laminating a first skin to a
first surface of the structure, the first skin including a first
foam having an average density that is at least 1.5 times greater
than the average density of the core foam structure and a thickness
that is at least 1.5 times smaller than the thickness of the core
foam structure; and laminating a second skin to a second surface of
the core foam structure, the second skin including a second foam
having an average density that is at least 1.5 times greater than
the average density of the core foam structure and a thickness that
is at least 1.5 times smaller than the thickness of the core foam
structure, wherein the flexural stiffness is increased by between 2
and 20 times.
37. The method of claim 36, wherein the core foam structure is a
laminated foam article including at least two foams each having an
average foam density of less than 4 pounds per cubic foot.
38. The method of claim 36, wherein the first skin and the second
skin each have an average foam density of between about 4 and 15
pounds per cubic foot.
39. The method of claim 36, wherein the core foam structure has an
average foam density of between 1 and 3 pounds per cubic foot, the
first skin has an average foam density of between about 4 and 12
pounds per cubic foot, and the second skin has an average foam
density of between about 4 and 12 pounds per cubic foot.
40. The method of claim 36, further comprising the step of
including a foam layer having an average foam density greater than
about 4 pounds per cubic foot in the core foam structure.
41. The method of claim 36, wherein the first skin and the second
skin each are laminated foam articles including two foams each
having an average foam density of greater than 4 pounds per cubic
foot.
42. The method of claim 36, wherein the foam comprises a
polyolefin.
43. The method of claim 42, wherein the polyolefin includes a
polyethylene or polypropylene.
44. The method of claim 43, wherein the foam further comprises a
single-site initiated polyolefin resin.
45. The method of claim 36, wherein at least a portion of the foam
is cross-linked.
46. A body board comprising a laminated foam board including: a
first skin laminated to a first surface of a core; and a second
skin laminated to a second surface of the core, wherein the core
includes a first foam having an average foam density of between
about 1 and 4 pounds per cubic foot, the first skin includes a
second foam and the second skin includes a third foam each having
an average foam density of between about 4 and 15 pounds per cubic
foot and a thickness less than 1/2inches, and the laminated foam
structure has a total thickness of less than about 3 inches and the
body board has a flexural stiffness that is between 2 and 20 times
greater than said core alone.
47. The body board of claim 46, wherein the first foam includes at
least two laminated foam articles.
48. The body board of claim 47, wherein each of the foam articles
has an average foam density of between 1 and 4 pounds per cubic
foot and a thickness of between 1/4and 1 inches.
49. The body board of claim 48, wherein the first foam further
includes a foam layer having an average foam density greater than
about 4 pounds per cubic foot and a thickness less than
1/2inch.
50. The body board of claim 49, wherein the second foam includes at
least two laminated foam articles.
51. The body board of claim 50, wherein the third foam includes at
least two laminated foam articles.
52. The body board of claim 46, wherein the foam comprises a
polyolefin.
53. The body board of claim 52, wherein the polyolefin is a
polyethylene or polypropylene.
54. The body board of claim 53, wherein the foam further comprises
a single-site initiated polyolefin resin.
55. The body board of claim 46, wherein at least a portion of the
foam is cross-linked.
56. The laminated foam structure of claim 1, wherein the first foam
structure, which is a skin, is laminated to a surface of the second
foam structure, which is a core, the core comprising at least two
core elements separated by a bending region that is a gap or crease
in the core, whereby the laminated foam structure can be folded
along the bending region.
57. The laminated foam structure of claim 56, wherein the skin has
an average foam density of between about 3 and 18 pounds per cubic
foot and a thickness less than {fraction (5/16)}inch, and the core
has an average density of between about 1 and 6 pounds per cubic
foot and a thickness of between 1 and 14 inches.
58. The laminated foam structure of claim 57, wherein the first
foam includes at least two laminated foam articles.
59. The laminated foam structure of claim 57, wherein each of the
foam articles has an average foam density less than 3 pounds per
cubic foot and the core thickness is between 1 and 5 inches.
60. The laminated foam structure of claim 59, wherein the second
foam has an average foam density greater between 10 and 12 pounds
per cubic inch and a thickness of between {fraction (1/16)}and
1/8inch.
61. The laminated foam structure of claim 57, wherein the foam
comprises a polyolefin.
62. The laminated foam structure of claim 61, wherein the
polyolefin includes a polyethylene or polypropylene.
63. The laminated foam structure of claim 62, wherein the foam
further comprises a single-site initiated polyolefin resin.
64. The laminated foam structure of claim 63, wherein at least a
portion of the foam is cross-linked.
65. The laminated foam structure of claim 57, wherein the laminated
foam structure is heat laminated.
66. A collapsible packaging system comprising: a sheet including a
skin laminated to a surface of a core, the sheet comprising a first
packing member connected by a hinge region of the sheet to a second
packing member, the core being scored or cut entirely through in
the hinged region to form the first and second packing members.
67. The collapsible packaging system of claim 66, wherein the first
packing member is partially defined by a slit extending entirely
through the sheet, and by a gap or a thinned region of the sheet
permitting clearance between the first and the second packing
members as they move relative to one another about the hinged
region, whereby the first packing member can be pivoted about the
hinge from a storage position in which the first packing member is
parallel to and contained within a gap in the second packing
member, to a packing position in which the first packing member is
oriented transverse to the second packing member.
68. The collapsible packaging system of claim 67, wherein the first
packing member is tapered, having a wide end nearest to the first
hinged region.
69. The collapsible packaging system of claim 67, wherein the sheet
further comprises a third packing member attached to the second
packing member by a second hinged region, the third packing member
being partially defined by a slit extending entirely through the
sheet, and by a gap or a thinned region of the sheet permitting
clearance between the second and the third packing members as they
move relative to one another about the second hinged region,
whereby, in the storage position, both the first and the third
packing member are parallel to and positioned within the second
packing member, and, in the packing position, the first and the
third packing members are generally parallel, forming a well for
containing a packed item.
70. The collapsible packaging system of claim 69, wherein the core
includes a first foam having an average foam density of between
about 1 and 6 pounds per cubic foot and a thickness of between 1
and 14 inches, and the skin includes a second foam having an
average foam density of between about 3 and 18 pounds per cubic
foot and a thickness less than {fraction (5/16)}inch.
71. The collapsible packaging system of claim 70, wherein the first
packing member is tapered, having a wide end nearest to the first
hinged region and the third packing member is tapered, having a
wide end nearest to the second hinged region.
72. The collapsible packaging system of claim 71, wherein the first
packing member and the third packing member are oriented so that
the first hinged region and the second hinged region are located
opposite to each other on the sheet.
73. The collapsible packaging system of claim 72, wherein the first
foam has an average foam density less than 3 pounds per cubic foot
and the core thickness is between 1 and 5 inches.
74. The collapsible packaging system of claim 73, wherein the
second foam has an average foam density greater between 10 and 12
pounds per cubic inch and a thickness of between {fraction
(1/16)}and 1/8inch.
75. The collapsible packaging system of claim 74, wherein each of
the foams comprises a polyolefin.
76. The collapsible packaging system of claim 75, wherein the
polyolefin includes a polyethylene or polypropylene.
77. The collapsible packaging system of claim 76, wherein each of
the foams further comprises a single-site initiated polyolefin
resin.
78. The collapsible packaging system of claim 77, wherein at least
one of the foams is cross-linked.
79. The collapsible packaging system of claim 78, wherein the
laminated foam structure is heat laminated.
80. A method of making a hinge comprising the steps of: providing a
sheet including a skin laminated to a surface of a core; cutting
through the core and the skin of the sheet to form a first packing
member; and cutting through the core of the sheet and leaving the
skin connected to the first packing member to form a first hinged
region, whereby the first packing member can be pivoted about the
hinge from a storage position in which the first packing member is
parallel to and contained with a gap in, the second packing member,
to a packing position in which the first packing member is oriented
transverse to the second packing member.
81. The method of claim 80, wherein the sheet is laminated foam
structure, the core includes a first foam having an average foam
density of between about 1 and 6 pounds per cubic foot and a
thickness of between 1 and 14 inches, and the skin includes a
second foam having an average foam density of between about 3 and
18 pounds per cubic foot and a thickness less than {fraction
(5/16)}inch.
82. The method of claim 81, wherein the first packing member is
tapered, having a wide end nearest to the first hinged region.
83. The method of claim 82, further comprising the steps of:
cutting through the core and the skin of the sheet to form a third
packing member; and cutting through the core of the sheet and
leaving the skin connected to the third packing piece to form a
second hinged region, whereby the third packing member can be
folded along the second hinged region, whereby in the storage
position, both the first and the third packing member are parallel
to and positioned within the second packing member, and, in the
packing position, the first and third packing members are generally
parallel, forming a well for containing a packed item.
84. The method of claim 83, wherein the first packing member is
tapered, having a wide end nearest to the first hinged region, and
the third packing member is tapered, having a wide end nearest to
the second hinged region.
85. The method of claim 84, wherein the first packing member and
the third packing member are oriented so that the first hinged
region and the second hinged region are located opposite to each
other on the sheet.
86. The method of claim 85, wherein the first foam has an average
foam density less than 3 pounds per cubic foot and the core
thickness is between 1 and 5 inches.
87. The method of claim 86, wherein the second foam has an average
foam density greater between 10 and 12 pounds per cubic inch and a
thickness of between {fraction (1/16)}and 1/8inch.
88. The method of claim 87, wherein each of the foams comprises a
polyolefin.
89. The method of claim 88, wherein the polyolefin includes a
polyethylene or polypropylene.
90. The method of claim 89, wherein each of the foams further
comprises a single-site initiated polyolefin resin.
91. The method of claim 90, wherein at least one of the foams is
cross-linked.
92. The method of claim 91, wherein the laminated foam structure is
heat laminated.
Description
CROSS-REFERENCE TO RELATED APPLICATION
1. This application is a continuation-in-part of co-pending
application U.S. Ser. No. 08/678,513, filed Jul. 9, 1996. Each of
the above applications and any patents issuing on them are hereby
incorporated by reference.
BACKGROUND OF THE INVENTION
2. The invention relates to polymer foams. In particular, the
invention relates to polymer foams having low densities with
enhanced physical properties.
3. Foam structures are useful in the areas of packaging, athletics,
water sports, and construction. In general, the foams are low
density polymeric materials with good physical properties that are
capable of supporting loads without adverse deformation. In
general, the physical properties required by these applications
suggest the use of high density foams. It is generally required
that the foams have good proportional limit, compressive
properties, shear properties, fatigue properties, and buckling
limits, as defined, for example, in "Machinery's Handbook," E.
Oberg, et al., Green, Ed., Industrial Press Inc., New York, 1992,
pages 166, 168 and 253.
4. Physically-blown foams, particularly foams with enhanced
physical properties are useful, for example, in packaging,
automotive, construction, contact sports, water sports, exercise,
and appliance applications. It is important to maintain good foam
properties (e.g., cushioning and resistance to creasing) at low
foam densities.
5. Packaging design has focused on the use of systems such as end
caps which fit on opposite ends of the packaged product (e.g.,
televisions, computers, and electronic equipment, or high value
artifacts such as glass vases or fragile art work) and suspend the
product in the center of a container during shipping and storage.
Previous suspension-type packaging systems have been composed of
corrugated or paperboard materials, molded low density foams such
as polystyrene, protective films or sheeting, wood, plastic,
organic or inorganic fill, or combinations of the above materials
that are glued together. Molded packaging materials, such as
styrofoam end caps, are bulky to transport and store. It is most
desirable for the structure to provide the required packaging
protection with the lowest amount of added weight.
SUMMARY OF THE INVENTION
6. The invention features foam structures that are laminated and
have enhanced physical properties, making them useful in the areas
of packaging, athletics, water sports, and construction. In
general, these structures include a core of a low density foam and
one or more skins of relatively high density foam covering the
core. The skins provide improved physical properties to the foam
structures by, for example, improving the flexural strength,
resistance to bending (or crimping), and resulting damage from
bending in the laminated foam structure. The foam structures have
improved stiffness, resist creasing, and more effectively dissipate
loading forces of the foam. The outer surface of the foam
structures is smooth and flat relative to the surface of the low
density case. The low density core provides a relatively low-weight
product that uses relatively small amounts of polymer material. The
laminated foam structure can be die cut so that the skin of higher
density foam on the outside of the structure can act as a hinge
allowing the die cut piece to be folded to make a collapsible
packaging system. Examples of physically-blown foams are described
in U.S. Ser. No. 08/638,122, filed Apr. 26, 1996 and entitled
"Cross-Linked Low-Density Polymer Foam", which is incorporated
herein by reference.
7. In one aspect, the invention features a laminated foam structure
that includes a first foam article laminated to a first surface of
a second foam article and a third foam article laminated to a
second surface of the second foam article. The first foam article
and the third foam article each have an average foam density that
is at least 1.5 times greater than the average foam density of the
second foam article and a volume that is at least 1.5 times smaller
than the second foam article. The flexural stiffness of the
laminated foam structure is 2-20 times higher than the flexural
stiffness of the second foam article. Flexural stiffness can be
determined directly from beam bending tests.
8. In preferred embodiments, the second foam article is a laminated
foam article including at least two foams. Each of the two foams
have an average foam density of less than 4 pounds per cubic foot.
Preferably, each of the two foams has a thickness between about
1/4and 1 inches. It is preferred that the first foam article and
the third foam article each have an average foam density of between
about 4 and 15 pounds per cubic foot. Preferably, each of the first
foam article and the third foam article has a thickness between
about {fraction (1/16)}and {fraction (5/16)}inches.
9. Preferably, the second foam article has an average foam density
of between 1 and 3 pounds per cubic foot, the first foam article
has an average foam density of between about 4 and 12 pounds per
cubic foot, and the third foam article has an average foam density
of between about 4 and 12 pounds per cubic foot. The first foam
article and the third foam article each can be laminated foam
articles including two foams each having an average foam density of
greater than 4 pounds per cubic foot.
10. In preferred embodiments, the second foam article can further
include a foam layer having an average foam density greater than
about 4 pounds per cubic foot. Preferably, the foam layer has an
average foam density between 4 and 15 pounds per cubic foot and a
thickness between about {fraction (1/16)}and 1/2inches.
11. In preferred embodiments, the structure has a total thickness
between about 3/4and 12 inches.
12. In another aspect, the invention features a laminated foam
structure including a first skin laminated to a first surface of a
core, and a second skin laminated to a second surface of the core.
The core includes a first foam having an average foam density of
between about 1 and 4 pounds per cubic foot, the first skin
includes a second foam and the second skin includes a third foam
each having an average foam density of between about 4 and 15
pounds per cubic foot and a thickness less than 1/2inches, and the
laminated foam structure has a total thickness of less than about
12 inches. The flexural stiffness of the laminated foam structure
is 2-20 times higher than the flexural stiffness of the core.
13. In yet another aspect, the invention features a body board that
includes a laminated foam structure. The laminated foam structure
includes a first skin laminated to a first surface of a core, and a
second skin laminated to a second surface of the core. The core
includes a first foam having an average foam density of between
about 1 and 4 pounds per cubic foot, the first skin includes a
second foam and the second skin includes a third foam each having
an average foam density of between about 4 and 15 pounds per cubic
foot and a thickness less than 1/2inches, and the laminated foam
structure has a total thickness of less than about 3 inches. The
higher densities of the first and second skins can make the
structure more resistant to mechanical damage from impact, shear,
and abrasive loads due to the higher polymer and lower air content
of the higher density foam.
14. In preferred embodiments, the first foam includes at least two
laminated foam articles. The second foam can include at least two
laminated foam articles or the third foam can include at least two
laminated foam articles. Preferably, each of the foam articles has
an average foam density of between 1 and 4 pounds per cubic foot
and a thickness of between 1/4and 1 inches. It is preferred that
the first foam further include a foam layer having an average foam
density greater than about 4 pounds per cubic foot and a thickness
less than 1/2inch.
15. In another aspect, the invention features a method of
increasing the flexural strength of a core foam structure including
the steps of laminating a first skin to a first surface of the
structure, and laminating a second skin to a second surface of the
core foam structure. The first skin includes a first foam having an
average density that is at least 1.5 times greater than the average
density of the core foam structure and a thickness that is at least
1.5 times smaller than the thickness of the core foam structure.
The second skin includes a second foam having an average density
that is at least 1.5 times greater than the average density of the
core foam structure and a thickness that is at least 1.5 times
smaller than the thickness of the core foam structure.
16. In preferred embodiments, the core foam structure is a
laminated foam article including at least two foams each having an
average foam density of less than 4 pounds per cubic foot. In other
preferred embodiments, the first skin and the second skin each have
an average foam density of between about 4 and 15 pounds per cubic
foot. Preferably, the core foam structure has an average foam
density of between 1 and 3 pounds per cubic foot, the first skin
has an average foam density of between about 4 and 12 pounds per
cubic foot, and the second skin has an average foam density of
between about 4 and 12 pounds per cubic foot. The first skin and
the second skin each can be laminated foam articles including two
foams each having an average foam density of greater than 4 pounds
per cubic foot.
17. In other preferred embodiments, the method further includes the
step of including a foam layer having an average foam density
greater than about 4 pounds per cubic foot in the core foam
structure.
18. In other preferred embodiments, the foam includes a polyolefin.
The polyolefin includes a polyethylene or polypropylene.
Preferably, the foam further includes a single-site initiated
polyolefin resin. In preferred embodiments, at least a portion of
the foam is cross-linked.
19. In another aspect, the invention features a laminated foam
structure including a first skin laminated to a first surface of a
core. The core includes a first foam having an average foam density
of between about 1 and 6 pounds per cubic foot, the first skin
includes a second foam having an average foam density of between
about 3 and 18 pounds per cubic foot and a thickness less than
1/2inches, and the laminated foam structure has a total thickness
of less than about 14 inches.
20. In another aspect, the invention features a laminated foam
structure including a first article laminated to a first surface of
a second foam article. The first article is a first foam article
having an average foam density that is at least 1.5 times greater
than the average foam density of the second foam article and a
volume that is at least 1.5 times smaller than the volume of the
second foam article.
21. In another aspect, the invention features a collapsible
packaging system. The system includes a sheet having a skin
laminated to a surface of a core. The sheet includes a first
packing member connected by a hinge region of the sheet to a second
packing member, and the core is scored or cut entirely through in
the hinged region to form the first and second packing members.
22. In preferred embodiments, the first packing member is partially
defined by a slit extending entirely through the sheet, and by a
gap or a thinned region of the sheet permitting clearance between
the first and the second packing members as they move relative to
one another about the hinged region. The first packing member can
be pivoted about the hinge from a storage position in which the
first packing member is parallel to and contained within a gap in
the second packing member, to a packing position in which the first
packing member is oriented transverse to the second packing member.
In other preferred embodiments, the first packing member is
tapered, having a wide end nearest to the first hinged region.
23. In other preferred embodiments, the sheet further includes a
third packing member attached to the second packing member by a
second hinged region. The third packing member is partially defined
by a slit extending entirely through the sheet, and by a gap or a
thinned region of the sheet permitting clearance between the second
and the third packing members as they move relative to one another
about the second hinged region. In the storage position, both the
first and the third packing member are parallel to and positioned
within the second packing member, and, in the packing position, the
first and the third packing members are generally parallel, forming
a well for containing a packed item.
24. In other preferred embodiments, the first packing member is
tapered, having a wide end nearest to the first hinged region and
the third packing member is tapered, having a wide end nearest to
the second hinged region. Preferably, the first packing member and
the third packing member are oriented so that the first hinged
region and the second hinged region are located opposite to each
other on the sheet.
25. In another aspect, the invention features a method of making a
hinge. The method includes the steps of: providing a sheet
including a skin laminated to a surface of a core; cutting through
the core and the skin of the sheet to form a first packing member;
and cutting through the core of the sheet and leaving the skin
connected to the first packing member to form a first hinged
region. The first packing member can be pivoted about the hinge
from a storage position in which the first packing member is
parallel to and contained with a gap in, the second packing member,
to a packing position in which the first packing member is oriented
transverse to the second packing member. In preferred embodiments,
the sheet is laminated foam structure.
26. In preferred embodiments, the method further includes the steps
of: cutting through the core and the skin of the sheet to form a
third packing member; and cutting through the core of the sheet and
leaving the skin connected to the third packing member to form a
second hinged region, whereby the third packing member can be
folded along the second hinged region. In the storage position,
both the first and the third packing member are parallel to and
positioned within the second packing member, and, in the packing
position, the first and third packing members are generally
parallel, forming a well for containing a packed item.
27. In other preferred embodiments, the first foam structure, which
is a skin, is laminated to a surface of the second foam structure,
which is a core, the core including at least two core elements
separated by a bending region that is a gap or crease in the core,
whereby the laminated foam structure can be folded along the
bending region.
28. In other preferred embodiments, the first foam article is a
skin having an average foam density of between about 3 and 18
pounds per cubic foot and a thickness less than {fraction
(5/16)}inch, and the second foam article is a core having an
average density of between about 1 and 6 pounds per cubic foot and
a thickness of between 1 and 12 inches. More preferably, each of
the foam articles has an average foam density of less than 3 pounds
per cubic foot and the core thickness is between 1 and 5 inches. In
other preferred embodiments, the second foam has an average foam
density greater between 10 and 12 pounds per cubic inch and a
thickness of between {fraction (1/16)}and 1/8inch. In other
preferred embodiments, the first foam article includes at least two
laminated foam articles.
29. The foam structures can include a variety of polyolefins in the
composition, including single-site initiated polyolefin resins.
Polyethylenes include ethylene-containing polyolefins. Single-site
initiated polyolefin resins include polyolefins prepared from a
single-site initiator that has controlled molecular weights and
molecular weight distributions. The polyolefin can be polyethylene,
polypropylene, or a copolymer of ethylene and alpha-unsaturated
olefin monomers.
30. Copolymers include polymers resulting from the polymerization
of two or more monomeric species, including terpolymers (e.g.,
resulting from the polymerization of three monomeric species),
sesquipolymers, and greater combinations of monomeric species.
Copolymers are generally polymers of ethylene with C.sub.3-C.sub.20
alpha-olefins, and/or diolefins.
31. The average foam densities can be measured according to
ASTM-3575; for example.
32. The foams in the laminated foam structures of the invention can
be cross-linked. Cross-linking can occur by high energy
irradiation, most preferably electron beam irradiation, peroxide
treatment, or silane-grafting and cross-linking by treatment with
water. Silane-grafting generally involves attaching one or more
silicon-containing monomer or polymer to the original polymer
chains. The use of silane-grafting for cross-linking in polymer
foams is described, for example, in U.S. Ser. No. 08/308,801, filed
Sep. 19, 1994 and entitled "Cross-Linked Foam Structures of
Essentially Linear Polyolefins and Process for Manufacture," which
is incorporated herein by reference, and in U.S. Ser. No.
08/638,122. The preferred foam structures contain silane-grafted
cross-linked resins.
33. The foams of the laminated foam structures are generally
closed-cell foams. The term "closed-cell," as used herein, means
that predominantly, greater than approximately 70% of the foam cell
volumes have cell walls isolating them from the external
atmosphere. One way to determine this is by measuring the amount of
water that is absorbed into the foam when the foam is immersed in
water.
34. The invention can have one or more of the following advantages.
The laminate structures include a core of a low density foam and
one or more skins of relatively high density foam covering the core
which improves, for example, the flexural strength, resistance to
bending, and resulting damage from bending in the laminated foam
structure. Because the skin is thin relative to the core, the
overall weight of the laminated structure is increased little
relative to the increase obtained in the physical properties of the
structure. Additional improvement in the physical foam properties
can result when a high density layer is added in the center of the
low density core. The high density layer can help further dissipate
loading forces.
35. In addition to improving the overall structural properties of
the foam structures, the laminated structures can also have an
improved smoother surface on the laminate. Because the skin
generally has a higher average density than the core, it is
generally a tougher material than the core. The "toughened" surface
of the structure makes it more durable as well.
36. The foams including silane-grafted single-site initiated
polyolefin resins generally have lower foam densities while
retaining good strength and other physical foam properties. See,
for example, U.S. Ser. No. 08/638,122. In general, by lowering the
average density and improving the physical properties of the
laminated foam structures, laminated structures that contain less
material are obtained. This decreases the cost of the materials and
decreases wasted material compared to non-laminated structures.
37. The laminated foam structures can be produced in a continuous
laminating operation. Moreover, the structures can be die cut
quickly and efficiently, for use in a variety of applications, such
as packaging. Efficient heat lamination of the skin to the core
eliminates the need to bond to dissimilar surfaces with adhesives
for many applications, contributing to the recyclability of the
materials.
38. By cutting through the core layer of the laminated structure
and not one of the skins to form a hinge, the resulting laminated
foam structures are versatile. For example, in packaging
applications, the packaging system is readily shipped in flat,
collapsed position to take up less space, saving freight and
storage expense and simplifying reuse of the material.
39. Other features and advantages of the invention will be apparent
from the following detailed description thereof, and from the
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
40. FIG. 1 is a drawing depicting a laminated foam structure having
a low density core and two high density skins.
41. FIG. 2 is a drawing depicting a laminated foam structure having
a low density core with a high density foam layer and two high
density skins.
42. FIG. 3 is a drawing depicting a laminated foam structure having
a low density core and two laminated high density skins.
43. FIG. 4 is a graph depicting the bending stress curves for a low
density foam core and a laminated foam structure having one higher
density skin layer on each surface.
44. FIG. 5 is a graph depicting the bending stress curves for a low
density foam core and a laminated foam structure having two higher
density skin layers on each surface.
45. FIG. 6 is a drawing depicting a laminated foam structure having
a low density core and one high density skin.
46. FIG. 7 is a drawing depicting a perspective view of a laminated
foam structure that has been die cut for a packaging application in
the collapsed configuration.
47. FIG. 8 is a drawing depicting a bottom view of the laminated
foam structure of FIG. 7.
48. FIG. 9 is a drawing depicting a top view of the laminated foam
structure of FIG. 7.
49. FIG. 10 is a drawing depicting a side view of the laminated
foam structure of FIG. 7.
50. FIG. 11 is a drawing depicting a cross-sectional side view of
the laminated foam structure of FIG. 7.
51. FIG. 12 is a drawing depicting a perspective view of a
laminated foam structure that has been die cut for a packaging
application in the expanded configuration.
52. FIG. 13 is a drawing depicting a top view of the laminated foam
structure of FIG. 12.
53. FIG. 14 is a drawing depicting a bottom view of the laminated
foam structure of FIG. 12.
54. FIG. 15 is a drawing depicting a cross-sectional side view of
the laminated foam structure of FIG. 12.
DETAILED DESCRIPTION
55. The laminated polymeric foam structures include a core of a low
density foam and one or more skins of high density foam relative to
the core that are laminated to the core. The skin covers a surface
of the core. In general, the core has a skin on at least one
surface of the core and can have a second skin laminated to another
surface of the core. In general, each of the skins and the core can
be a laminated foam structure. The laminated structure can be
produced using any conventional lamination technique, including
heat, film, or adhesive lamination. The laminated construction
improves the mechanical properties of the structure such as
proportional limit, compressive properties, shear properties,
fatigue, and buckling.
56. Preferably, the foam articles are foam sheets or planks which
can be prepared as described, for example, in U.S. Ser. No.
08/638,122. Foam articles with a broad range in physical
properties, including a broad range of average foam densities, can
be prepared by the methods described therein. Particularly
preferred laminated foam structures are described and illustrated
in FIGS. 1, 2, and 3
57. Referring to FIG. 1, the laminated foam structure 1 has a core
4 laminated to a first skin 6 on one surface of core 4. The core 4
is also laminated to a second skin 8 on a second surface of core 4.
Skin 6 and skin 8 are generally foams having average densities of
between 4 and 12 pounds per cubic foot and thicknesses of between
{fraction (1/16)}and 1/8inches. Core 4 is a laminated foam with
multiple layers. In these preferred embodiments, core 4 has four
layers including foam 10, foam 12, foam 16, and foam 18. The foams
10, 12, 16, and 18 in core 4 each have average foam densities of
between 1.2 and 2.5 pounds per cubic foot and thicknesses of
between 3/8and 5/8inches. Core 4, and its constituent foams 10, 12,
16 and 18, have average foam densities that are low relative to the
first skin 6 and second skin 8. The structure 1 has a total
thickness 20 which is generally between 3/4and 8 inches. Foams
according to FIG. 1 can be used in packaging applications.
58. Referring to FIG. 2, the laminated foam structure 2 has a core
consisting of a low density sub-core 4a and a low density sub-core
4b laminated, respectively, to each surface of a relatively high
density foam layer 7. The foam layer 7 is a foam having an average
density of between 4 and 12 pounds per cubic foot and a thickness
of between {fraction (1/16)}and 1/8inches. The core is laminated to
a first skin 6 on one surface of the core and to a second skin 8 on
a second surface of the core. Skin 6 and skin 8 are generally foams
having average densities of between 4 and 12 pounds per cubic foot
and thicknesses of between {fraction (1/16)}and 1/8inches. Each of
the sub-cores 4a and 4b is a laminated foam with multiple layers.
In this preferred embodiment, sub-core 4a has three layers
including foam 10, foam 12, and foam 13 and sub-core 4b has three
layers including foam 14, foam 16, and foam 18. The foams 10, 12,
13, 14, 16, and 18 in the core each have average foam densities of
between 1.2 and 2.5 pounds per cubic foot and thicknesses of
between 3/8and 5/8 inches. Each sub-core 4a and 4b, their
constituent foams, and the core including foam layer 7 have average
foam densities that are low relative to the first skin 6 and second
skin 8. The structure 2 has a total thickness 20 which is generally
between 3/4and 8 inches or greater. Foams according to FIG. 2 can
be used in packaging applications.
59. Referring to FIG. 3, the laminated foam structure 3 has a core
4 laminated to a first skin 6 on one surface of core 4. The core 4
is also laminated to a second skin 8 on a second surface of core 4.
Core 4 is a laminated foam with multiple layers. In this
embodiment, core 4 has four layers including foam 10, foam 12, foam
16, and foam 18 each have average foam densities of between 1.2 and
2.5 pounds per cubic foot and thicknesses of between 3/8and
1/2inches. Core 4, and its constituent foams 10, 12, 16 and 18,
have average foam densities that are low relative to the first skin
6 and second skin 8. Skin 6 is a laminated foam including outer
foam 22 and inner foam 24. Skin 8 is a laminated foam including
outer foam 26 and inner foam 28. Foams 22, 24, 26, and 28 each have
average densities of between 4 and 12 pounds per cubic foot and
thicknesses of between {fraction (1/16)}and 1/8inches, with the
outer foams 22 and 26 having average densities lower than the inner
foams 24 and 28. In preferred embodiments, each of outer foams 22
and 26 has an average density of 6 pounds per cubic foot and a
thickness of between {fraction (1/16)}and 1/8inches and each of
inner foams 24 and 28 has an average density of 8 pounds per cubic
foot and a thickness of about 1/8inch. Core 4 is a laminated foam
with multiple layers. In these preferred embodiments, core 4, and
its constituent foams 10, 12, 16 and 18, have average foam
densities that are low relative to the first skin 6 and second skin
8. The structure 3 has a total thickness 30 generally between 2 and
21/4inches. Foams according to FIG. 3 can be used in water sports
as body boards or kick boards, in exercise equipment (e.g., as gym
mats), and in construction applications as eaves fillers.
60. The preferred foams are polyethylene foams that are described,
for example, in U.S. Ser. No. 08/638,122. The preferred skins are
foams that have an average foam densities of between about 4 and 15
pounds per cubic foot (pcf), preferably between about 4 and 12 pcf,
and thicknesses between {fraction (1/16)}and 3/8inches. Most
preferably, the skins have average foam densities of about 8 pcf
and thicknesses of 1/8inch. The preferred core is a foam with an
average foam density of less than 4 pcf, preferably between about
1.2 and 2.5 pcf. The core is a foam laminate with multiple foam
layers each-having thicknesses between about 3/8and 5/8inches. The
laminated core preferably has between 2 and 20 foam layers. The
total thickness of the core layer is determined by the overall
thickness requirement of the application of the laminated foam
structure. The total thickness of the laminated foam structure is,
most preferably, between about 3/4and 12 inches. The laminated core
can include a high density foam layer, having an average foam
density between about 4 and 12 pcf and thicknesses between
{fraction (1/16)}and 3/8inches.
61. In embodiments in which the skin is a laminate, the outer layer
of the skin preferably has a higher density than the adjacent foam
layer. In the laminated skin, the preferred skin preferably has an
average foam density of 8 pcf and a thickness of 1/8inch which is
laminated to an outer skin of having an average foam density of 6
pcf and a thickness of about {fraction (1/16)}inch. The laminated
skin structure gives better resistance to creasing in flexure,
which is important, for example, in the water sports applications
such as body boards.
62. The laminated foam structures and their potential applications
are varied. For example, a laminated foam structure with a total
thickness between about 3/4to 8 inches is useful in packaging. The
low density foam core contributes to a low weight of the total
package while the high density foam of the skin provides aesthetic
improvement and improved load spreading properties. The skin has a
higher foam density, generally as a result of smaller cell size. As
a result, the surface of the skin is denser and smoother than the
surface of the low density core and has the appearance of a highly
cross-linked surface.
63. The embodiments depicted in FIG. 1 or FIG. 2 are examples of
structures that can be used in packaging applications. In another
example, a 2 inch laminated foam structure can be used in exercise
equipment such as gym mats, where the high density skin gives
improved load spreading and resistance to damage resulting from
heavy use. In another example, a 1 inch laminated foam structure
can be used as a construction eaves filler, where the high density
skin gives the structure improved compression resistance, a more
durable surface, and improved die cutting characteristics. In
another example, a 2 inch laminated foam structure can be used in
the water sports industry for making body boards, where the
improved flexural strength gives resistance to bending and
creasing, as well as fatigue resistance. The embodiments depicted
in FIG. 3 are examples of structures that can be used in water
sports, exercise, and construction applications. In each of the
preceding examples, the laminated foam structures generally
provides for overall weight reductions over an extruded plank
construction, increased compression resistance, and improved load
spreading behavior.
64. Assorted shapes can be cut for the laminated foam structures
with either solid or foamed cores. The shape is configured for
particular end applications (e.g., to fit into an end product).
Alternatively, the structure is cut to form a hinge so that the
structure can be folded into different shapes. For example, the
core of the laminated foam structure of a sheet can be cut to form
a piece (i.e., packing member), leaving a section of the skin
intact in one region of the perimeter of the piece so that the skin
can act as a hinge. The piece can be positioned in the plane of the
sheet from which it was cut (i.e., in a collapsed or closed form).
Alternatively, the piece can be positioned out of the plane of the
sheet (i.e., in an expanded or open form). By tapering the piece,
it is possible to form a locking mechanism to hold the piece in the
expanded or collapsed form. In the expanded form, the area formerly
occupied by the piece forms a void in the sheet that can be sized
to fit a product for packaging.
65. Cutting of pieces or shapes can be achieved by hand using
knives or scissors. A more efficient method is to use sharpened
steel rule dies of forged dies to cut the entire shape all at once
(i.e., die cutting). In this process, a hydraulic press, or a
"Clicker" type press, operating at pressures between 50 and 150 psi
and at room temperature, can be used to press the die into the
laminated polymer structure. Once the press has forced the die
through the material, completely severing it from the rest of the
structure, the "puzzle-like" piece can be removed for use. In order
to form a hinge from the skin to link the cut piece to the
remainder of the sheet, a section of the die is offset so that it
cuts through the core, but does not cut through or sever the
skin.
66. Referring to FIG. 6, the laminated foam structure 3 is a flat
sheet that has a core 4 laminated to a first skin 6 on one surface
of core 4. Structure 3 has a top surface 30, which is an exposed
surface of core 4, and a bottom surface 35, which is an exposed
surface of skin 6. Skin 6 is generally foams having average
densities of between 3 and 18 pounds per cubic foot and thicknesses
of between {fraction (1/32)}and {fraction (5/16)}inches. Core 4 is
a laminated foam with multiple layers. Alternatively, core 4 can be
a single section of foam. In preferred embodiments, core 4 has four
layers including foam 10, foam 12, foam 16, and foam 18. The foams
10, 12, 16, and 18 in core 4 each have average foam densities of
between 1.5 and 2.5 pounds per cubic foot and thicknesses of
between 3/8and 5/8inches. The core foams are preferably polyolefin
foams, such as a polyethylene or polypropylene foam that is closed
cell in nature. Core 4, and its constituent foams 10, 12, 16 and
18, have average foam densities that are low relative to skin 6.
Skin 6 provides strength to the structure and can act as a hinge
when the structure of the foam is properly cut. The structure 3 has
a total thickness 20 which is generally between 1 and 14 inches.
The laminated foam structure is effectively bonded together using
heat lamination to enhance recyclability of the material, however,
glue or adhesive or any other material useful for lamination may be
used to effect the bond. Structures according to FIG. 6 can be used
in packaging applications.
67. Referring to FIGS. 7-11, laminated foam structure 3 can be die
cut for packaging applications to form a collapsible packaging
system that is shown in the collapsed configuration. Piece 40
(i.e., a first packing member) and piece 42 (i.e., a second packing
member) are cut from structure 3 by completely cutting through core
4 and skin 6 at head slit 44 and side slits 46. Referring to FIG.
11, tail slit 48 is cut from the top surface 30 through core 4 and
not through skin 6, forming a hinge between piece 40 (or piece 42)
and the remainder of the sheet. Tail slit 48 does not extend to
bottom surface 35. The die cut can be designed so that sections of
the laminated foam article can be removed altogether to lower the
total weight of the collapsible packaging system.
68. Referring to FIGS. 12-15, die cut laminated foam structure 3
depicted in FIGS. 7-11 can be expanded to form end cap 50 for use
in packaging. Piece 42 is extended out of the plane of the sheet by
bending along the hinge formed at tail slit 48 onto bottom surface
35. Piece 40 is similarly extended to form the expanded
configuration. In this expanded configuration, well 60 is
formed.
69. Pieces 40 and 42 are tapered, having wider ends at tail slits
48 than at head slit 44. Referring to FIG. 14, the tapering of
pieces 40 and 42 allow them to lock into place when extended from
the sheet and the hinge is bent at an angle 90.degree. to bottom
35.
70. The dimensions of well 60 are suited to fit end cap 50 onto,
for example, each end of a packaged product. The outer dimensions
of end cap 50 are suitable securing the product having two end caps
in a carton, box, or other suitable container.
71. When not being used for packaging a product, the expanded
configuration of end cap 50 can be collapsed back into the
space-efficient sheet form for storage or transport of the
collapsible packaging system. The hinge structures allow the
packaging system to be efficiently reused.
72. Die cutting is the preferred operation for cutting the
laminated foam structures since it is simple to carry out and
repeat (e.g., automate). The cutting operation is the only
necessary step for producing protective collapsible packaging
systems directly from the laminated foam structures. Laminated foam
structures having more than one high density skin (i.e., a skin on
both surfaces of the structure) can be cut in a similar manner to
form the hinges and collapsible packaging systems. For example, the
additional skin can be added for additional structural stability
and support.
73. The foams are generally foamed polymers and polymer blends.
Examples of suitable polymers include single-site initiated
polyolefins, low density polyethylene (LDPE), high density
polyethylene (HDPE), linear low density polyethylene (LLDPE),
ethylene-propylene rubber, ethylene-propylene-diene monomer
terpolymer (EPDM), polystyrene, polyvinylchloride (PVC),
polyamides, polyacrylates, celluloses, polyesters, polyhalocarbons,
and copolymers of ethylene with propylene, isobutene, butene,
hexene, octene, vinyl acetate, vinyl chloride, vinyl propionate,
vinyl isobutyrate, vinyl alcohol, allyl alcohol, allyl acetate,
allyl acetone, allyl benzene, allyl ether, ethyl acrylate, methyl
acrylate, acrylic acid, or methacrylic acid. The polymer blends can
also include rubber materials such as polychloroprene,
polybutadiene, polyisoprene, polyisobutylene, nitrile-butadiene
rubber, styrene-butadiene rubber, chlorinated polyethylene,
chlorosulfonated polyethylene, epichlorohydrin rubber,
polyacrylates, butyl rubber, or halobutyl rubber. The rubber
material can be peroxide-cured or vulcanized. Preferred resins
include single-site initiated polyolefins, LDPE, LLDPE,
polypropylene, polystyrene, or ethylene copolymers such as
ethylene-vinyl acetate copolymer (EVA), or ethylene-ethyl acrylate
copolymer (EEA).
74. The single-site initiated polyolefin resins are derived from
ethylene polymerized with at least one comonomer selected from the
group consisting of at least one alpha-unsaturated C.sub.3-C.sub.20
olefin comonomers. Preferably, the alpha-unsaturated olefins
contain between 3 and 16 carbon atoms, most preferably between 3
and 8 carbon atoms. Examples of such alpha-unsaturated olefin
comonomers used as copolymers with ethylene include, but are not
limited to, propylene, isobutylene, 1-butene, 1-hexene,
3-methyl-1-pentene, 4-methyl-1-pentene, 1-octene, 1-decene,
1-dodecene, styrene, halo- or alkyl-substituted styrene,
tetrafluoroethylene, vinylcyclohexene, and vinylbenzocyclobutane.
The comonomer content of the polyolefin resins is generally between
about 1 mole percent and about 32 mole percent, preferably between
about 2 mole percent and about 26 mole percent, and most preferably
between about 6 mole percent and about 25 mole percent.
75. The copolymer can include one or more C.sub.4-C.sub.20 polyene
monomers. Preferably, the polyene is a straight-chain, branched
chain or cyclic hydrocarbon diene, most preferably having between 6
and 15 carbon atoms. It is also preferred that the diene be
non-conjugated. Examples of such dienes include, but are not
limited to, 1,3-butadiene, 1,4-hexadiene, 1,6-octadiene,
5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6-octadiene,
3,7-dimethyl-1,7-octadiene, 5-ethylidene-2-norbornene, and
dicyclopentadiene. Especially preferred is 1,4-hexadiene.
76. The preferred single-site initiated polyolefin resins include
either ethylene/alpha-unsaturated olefin copolymers or
ethylene/alpha-unsaturate- d olefin/diene terpolymers.
77. Single-site initiated polyolefin resins can be prepared using
single-site initiators. One class of a single-site initiators of
particular interest are the metallocene initiators which are
described, for example, in J. M. Canich, U.S. Pat. No. 5,026,798,
in J. Ewen, et al., U.S. Pat. No. 4,937,299, in J. Stevens, et al.,
U.S. Pat. No. 5,064,802, and in J. Stevens, et al., U.S. Pat. No.
5,132,380, each of which are incorporated herein by reference.
These initiators, particularly those based on group 4 transition
metals, such as zirconium, titanium and hafnium, are extremely high
activity ethylene polymerization initiators. The single-site
initiators are versatile. The polymerization conditions such as a
initiator composition and reactor conditions can be modified to
provide polyolefins with controlled molecular weights (e.g., in a
range from 200 g mol.sup.-1 to about 1 million or higher g
mol.sup.-1) and controlled molecular weight distributions (e.g.,
M.sub.w/M.sub.n in a range from nearly 1 to greater than 8, where
M.sub.w is the weight average molecular weight and M.sub.n is the
number average molecular weight). Molecular weights and molecular
weight distributions of polymers can be determined, for example, by
gel permeation chromatography.
78. When the single-site initiated polyolefins are copolymers, the
composition distribution breadth index (CDBI) is generally greater
than 50% and most preferably above 70%. The CDBI is a measurement
of the uniformity of distribution of comonomers among the
individual polymer chains having a comonomer content within 50% of
the median bulk molar comonomer content.
79. Preferred single-site initiated polyolefin resins are
described, for example, in S.-Y. Lai, et al., U.S. Pat. Nos.
5,272,236, 5,278,272, and 5,380,810, in L. Spenadel, et al., U.S.
Pat. No. 5,246,783, in C. R. Davey, et al., U.S. Pat. No.
5,322,728, in W. J. Hodgson, Jr., U.S. Pat. No. 5,206,075, and in
F. C. Stehling, et al., WO 90/03414, each of which is incorporated
herein by reference. The resins contain varying amounts of
short-chain and long-chain branching, which depend, in part, on the
processing conditions.
80. Some single-site initiated polyolefin resins are available
commercially from Exxon Chemical Company, Houston, Tex., under the
tradename Exact.TM., and include Exact.TM. 3022, Exact.TM. 3024,
Exact.TM. 3025, Exact.TM. 3027, Exact.TM. 3028, Exact.TM. 3031,
Exact.TM. 3034, Exact.TM. 3035, Exact.TM. 3037, Exact.TM. 4003,
Exact.TM. 4024, Exact.TM. 4041, Exact.TM. 4049, Exact.TM. 4050,
Exact.TM. 4051, Exact.TM. 5008, and Exact.TM. 8002. Other
single-site initiated resins are available commercially from Dow
Plastics, Midland, Mich. (or DuPont/Dow), under the tradenames
Engage.TM. and Affinity.TM., and include CL8001, CL8002, EG8100,
EG8150, PL1840, PL1845 (or DuPont/Dow 8445), EG8200, EG8180,
GF1550, KC8852, FW1650, PL1880, HF1030, PT1409, CL8003, and D8130
(or XU583-00-01). Most preferably, the single-site initiated
polyolefin resins are selected from the group consisting of
Exact.TM. 3024, Exact.TM. 3031, Exact.TM. 4049, PL1845, EG8200, and
EG8180.
81. The preferred foams include polyethylene, such as, for example,
single-site initiated polyethylenes or LDPE. LDPE resins are
described, for example, in "Petrothene.RTM. Polyolefins . . . A
Processing Guide," Fifth Edition, Quantum USI Division, 1986, pages
6-16, incorporated herein by reference. Some LDPE resins are
commercially available from Exxon Chemical Company, Houston, Tex.,
Dow Plastics, Midland, Mich., Novacor Chemicals (Canada) Limited,
Mississauga, Ontario, Canada, Mobil Polymers, Norwalk, Conn.,
Rexene Products Company, Dallas, Tex., Quantum Chemical Company,
Cincinnati, Ohio, and Westlake Polymers Corporation, Houston, Tex.
Commercially available LDPE resins include Eastman 1924P, Eastman
1550F, Eastman 800A, Exxon LD 117.08, Exxon LD 113.09, Dow 535I,
Dow 683, Dow 760C, Dow 768I, Dow 537I, Novacor LF219A, Novacor
LC05173, Novacor LC0522A, Mobil LMA-003, Mobil LFA-003, Rexene 2018
(7018), Rexene 1023, Rexene XO 875, Rexene PE5050, Rexene PE1076,
Rexene PE2030, Quantum NA953, Quantum NA951, Quantum NA285-003,
Quantum NA271-009, Quantum NA324, Westlake EF606AA, Westlake EF612,
and Westlake EF412AA.
82. The foams can be cross-linked, however, non-cross-linked foams
also can be made. The foams can be cross-linked with peroxides, UV
irradiation, or by silane-grafting. The use of silane-grafting for
cross-linking in polymer foams is described, for example, in U.S.
Ser. No. 08/308,801, and in U.S. Ser. No. 08/638,122.
83. The foam can preferably be a polymer blend including at least
one silane-grafted single-site initiated polyolefin resin. The
preferred level of silane-grafted single-site initiated polyolefin
resin, in weight percent of the total polymeric content of the
foam, is preferably between about 2 percent and about 30 percent
more preferably between about 3 percent and about 18 percent. The
single-site initiated polyolefin resin can be silane-grafted before
blending with other polymer resins. Alternatively, the foam can be
a polymer blend. The blend can be silane-grafted.
84. Silane-grafting of the polyolefin resin or resin blend occurs
when the polymer backbone is activated and reacts with a silane
reagent to form the graft copolymer. The silane-graft can include a
subsequently cross-linkable moiety in the graft chain. For example,
the cross-linking can occur under warm, moist conditions when the
cross-linkable moiety is hydrolyzable, optionally in the presence
of a suitable catalyst. Levels of cross-linking can be adjusted by
varying the amount of silane-grafting introduced to the polymer
blend. Alternatively, cross-linking can be introduced by reaction
of the polymers with peroxides. UV irradiation of the polymers can
also be used to introduce cross-linking.
85. A cross-linking graft can include other monomers, such as di-
and tri-allyl cyanurates and isocyanurates, alkyl di- and
tri-acrylates and methacrylates, zinc dimethacrylates and
diacrylates, styrenes, divinylbenzene, and butadiene.
86. The graft initiator, or peroxide cross-linking agent can be a
free radical generating species, for example, a peroxide. Examples
of peroxides include dicumylperoxide,
2,5-dimethyl-2,5-di(t-butylperoxy)hexa- ne,
1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane,
1,1-di-(t-butylperoxy)cyclohexane,
2,2'-bis(t-butylperoxy)diisopropylbenz- ene,
4,4'-bis(t-butylperoxy)butylvalerate, t-butylperbenzoate,
t-butylperterephthalate, and t-butyl peroxide. Most preferably, the
peroxide is dicumylperoxide or
2,2'-bis(t-butylperoxy)diisopropylbenzene.
87. The silane-grafted polymer can be cross-linked by exposure to
moisture to effect silanol condensation reactions of the
hydrolyzable groups of the pendant silane-grafts. Cross-linking
develops through hydrolysis of the silane Y groups to form silanols
which condense to form siloxanes. The condensation of silanols to
siloxanes is catalyzed by metal carboxylates such as, for example,
dibutyl tin dilaurate or dibutyl tin maleate. The most preferred
silanol condensation catalyst is dibutyl tin dilaurate.
88. The cross-linking of silane-grafted polymers can be induced by
the presence of atmospheric moisture, steam, or hot water.
Cross-linking can take place predominantly (e.g., more than 50% of
the potential cross-linking) prior to expansion (or extrusion) of
the foam. Alternatively, the cross-linking can take place
predominantly after expansion of the foam.
89. Exposure of the compositions to high energy radiation to induce
cross-linking can be accomplished at dosages of ionizing radiation
in the range of about 0.1 to 40 Megarads, and preferably, at about
1 to 20 Megarads. The amount of cross-linking can be appropriately
controlled by adjusting the dosage of high energy radiation.
90. Regardless of the method of cross-linking used, acceptably
flexible articles, particularly foamed articles, can only be
obtained in certain ranges of cross-linking density or level, which
is related to the amount of silane-grafting in the blend. Too much
cross-linking can render the material inelastic. In a foam, this
can result in less than optimal expansion and greater than optimal
density for a given level of foaming agent. Too little
cross-linking can be detrimental to physical properties such as
compression set properties or thermal resistance, for example. It
is important to choose cross-linking levels that afford materials
with particular desired properties. The silane-grafting and
resulting cross-links increase the melt strength of the
composition. The cross-linking levels can be determined by
establishing the gel content of the of the composition, for
example, by extraction with a solvent such as xylenes.
91. The foams can be prepared using physical or chemical foaming
agents. Physical foaming agents include low molecular weight
organic compounds including C.sub.1-C.sub.6 hydrocarbons such as
acetylene, propane, propene, butane, butene, butadiene, isobutane,
isobutylene, cyclobutane, cyclopropane, ethane, methane, ethene,
pentane, pentene, cyclopentane, pentene, pentadiene, hexane,
cyclohexane, hexene, and hexadiene, C.sub.1-C.sub.5 organohalogens,
C.sub.1-C.sub.6 alcohols, C.sub.1-C.sub.6 ethers, C.sub.1-C.sub.5
esters, C.sub.1-C.sub.5 amines, ammonia, nitrogen, carbon dioxide,
neon, or helium. Chemical foaming agents include, for example,
azodicarbonamide, p-p'-oxybis(benzene)sulfonyl hydrazide,
p-toluenesulfonyl hydrazide, p-toluenesulfonyl semicarbazide,
5-phenyltetrazole, ethyl-5-phenyltetrazole,
dinitrosopentamethylenetetram- ine, and other azo, N-nitroso,
semicarbazide, sulfonyl hydrazides, carbonate, and bicarbonate
compounds that decompose when heated. The preferred foaming agents
include azodicarbonamide or isobutane.
92. The foam can be partially or extensively cross-linked prior to
expansion, or can be extensively cross-linked after expansion.
93. Additional additives in the foam composition can dramatically
effect the properties of the foam. These include gas exchange
additives and cell nucleating agents, such as zinc stearate and
talc, respectively. The preferred gas exchange additive
concentration in the foam is between 0.5 and 2.0 percent. The
preferred cell nucleating agent concentration in the foam is
between 0.05 and 2.0 percent. The foam can also include gas
exchange additives, also known as cell-structure stabilizers, such
as, for example, fatty acids, fatty acid carboxylate salts (e.g.,
zinc stearate), fatty acid esters (e.g. glycerol monostearate), or
fatty acid amides, assist in the gas exchange process and the aging
of the foams.
94. Other additives, alone or in combination, can be added to the
foam compositions, including antioxidants (e.g., hindered phenolics
such as Irganox 1010, phosphites such as Irgafos 168, or
polymerized trimethyl-dihydroquinoline such as Agerite AK, Resin D
or Flectol H), ultra-violet stabilizers, thermal stabilizers,
antistatic components, flame retardants, pigments or colorants, and
other processing aids.
95. The foam can take virtually any physical configuration,
preferably the form of a sheet, plank, or other regular or
irregular extruded profile. Foam sheets are extruded from circular
dies and have thicknesses between about {fraction (1/32)}inch and 1
inch and widths up to 82 inches. Parts of smaller size, depending
on requirements of the application, can be cut from the sheets. For
example, a board with typical dimensions of 20 inches by 30 inches
may be cut from the larger sheets, and further shaped by molding or
machining to produce a body board for water sports. Alternatively,
the foams can be configured as planks, extruded from flat dies,
with plank thicknesses between about 1 inch and 4.5 inches and
widths between about 24 inches and 48 inches. The foam planks and
sheets can be laminated by direct application of heat or adhesives
to the interface between two or more planks. In preferred
embodiments, it is not necessary to add an adhesive to the
interface to laminate the planks or sheets.
96. The foam lamination can be achieved by heat treatment of the
laminate interface, film lamination, or by using an adhesive. These
techniques are generally well known in the sheet fabrication
industries. Heat lamination is a process in which two sheets of
foam or other sheet material are brought together under pressure
and heat to join the materials. In practice, foam is taken from
rolls of approximately 1/2inches thickness.times.48 inches
width.times.400 feet in length. The foam sheets are fed together
with pressure exerted by two turning rollers. Immediately prior is
to the materials meeting in the nip of the rollers, heat is applied
to the surfaces which are about to be pressed together. The heat
can be supplied by hot air guns, gas-fired flames, infrared
heaters, or a combinations thereof. Heat can be applied to both
foam sheets, or only to one. The heat makes the foam surface tacky
by creating local regions of melting on the surface. The foam
sheets passing through the rollers nip are joined by a bond upon
cooling. A similar laminate can be made by applying an adhesive to
one or both sheets prior to the foam passing through the nip
rollers, or by extrusion of a thin continuous layer of polymer onto
one surface immediately prior to the foam passing through the nip
rolls. By choosing a film material which is compatible with the
substrates, a laminate is formed. Adhesives include, but are not
limited to, rubber, epoxy, and acrylic adhesives. Heat and film
lamination methods are preferred since those methods can avoid the
use of solvents in the lamination process.
97. In adhesive lamination, the foam articles can be coated with an
adhesive using any of a number of conventional coating techniques
including reverse roll coating, knife over roll coating, or
extrusion coating. Optionally, the coated substrate can be passed
through an in-line dryer to remove solvent or water, or to
chemically alter the coating. Machinery for coating these tapes can
be purchased from equipment suppliers such as Ameriflex Group
Incorporated, Black Clawson Converting Machinery Corporation,
Inta-Roto, Incorporated, Klockner Er-We-Pa, and Wolverine
Massachusetts Corporation.
98. The following specific examples are to be construed as merely
illustrative, and not limitive, of the remainder of the
disclosure.
EXAMPLES
99. A laminated foam structure having four low density foam layers
in a core and a higher density skin on each surface of the core can
be manufactured using the following steps:
100. Step 1
101. Four layers of 1/2inch polyethylene foam with a density of 1.7
pcf are continuously laminated from roll stock using hot air
injected between the layers which are then pressed together between
nip rolls. Sheets are cut after lamination to make handling easier.
The 1.7 pcf laminated foam core (hereafter referred to as Example
1A) had a total thickness of 1 inch.
102. Step 2
103. A layer of 8 pcf polyethylene foam that is {fraction
(3/16)}inches thick is laminated to one side of the foam core of
Example 1A (i.e., the 1 inch thick 1.7 pcf laminated foam core) by
feeding the 1 inch thick sheets into the laminator used in step 1.
The 8 pcf layer is fed from roll stock. The resultant sheets are
cut as in step 1.
104. Step 3
105. Step 2 is repeated to laminate a second 8 pcf polyethylene
foam layer that is {fraction (3/16)}inches thick to the other side
of the 1.7 sheet, resulting in a laminated foam structure
consisting of a core of four laminated 1.7 pcf polyethylene foams
with a skin of 8 pcf polyethylene foam on each side of the core
with a total thickness of 2.1 inches (i.e., an 8/1.7/8 laminate,
hereafter referred to as Example 1). Example 1 has a structure
similar to that shown in FIG. 1.
Example 2
106. A foam laminate structure having four low density foam layers
in a core and a two-layer higher density skin on each surface of
the core can be manufactured using the following steps:
107. Step 1
108. A four-ply laminated foam core of 2 pcf, 1/2inch thick
polyethylene foam sheets is produced by the process of step 1 of
Example 1 (hereafter referred to as Example 2A).
109. Step 2
110. A layer of 8 pcf polyethylene foam that is {fraction
(3/16)}inches thick is laminated to each side of the four-ply
laminated foam core Example 2A by the process of step 2 and step 3
of Example 1 to afford an 8/2/8 laminated foam structure.
111. Step 3
112. A layer of 6 pcf polyethylene foam that is 1/8inches thick is
laminated to each side of the 8/2/8 laminated foam structure of
step 2 by the process of step 2. The final laminated foam structure
has a core of four laminated 2 pcf polyethylene foams with a skin
of 8 pcf foam and an outer skin of 6 pcf foam on each side of the
core with a total thickness of 2.25 inches (i.e., an 6/8/2/8/6
laminate, hereafter referred to as Example 2). Example 1 has a
structure similar to that shown in FIG. 3.
113. Bending Test
114. The flexural stiffness, or flexural strength, of the laminated
foam structures were tested by bending a 36 inch length of the
laminated foam structures Example 1 (the 8/1.7/8 laminate) and
Example 2 (the 6/8/2/8/6 laminate). A 36 inch length of the
corresponding core structures Example 1A (the 1.7 pcf core) and
Example 2A (the 2 pcf core) at the same thicknesses was bent as a
comparison. Beam bending tests are used in the plastics industry as
a measure or stiffness. As an example, ASTM-D790 and ASTM-D229 are
used extensively to evaluate the flexural modulus (i.e., flexural
strength) of solid plastics. In our method, two point supports are
located 36 inches apart on a solid horizontal surface. The midpoint
of the supported length is determined. Successive weights are added
to the midpoint in increments of 100 to 1000 grams, and the
deflection is immediately measured. Stiffer materials are more
resistant to bending and produce lower deflection. Deflection is
measured in inches displaced from the straight beam position. The
bending stress curves for Example 1A and Example 1 are shown in
FIG. 4. The bending stress curves of Example 2A and Example 2 are
shown in FIG. 5.
115. Generally, the laminated foam structures have much higher
resistance to bending than the comparative core foams. Also, the
uncut laminated foam structures (e.g., Example 1) do not crease
when bent at angles up to 90 degrees. However, under the same
conditions, the laminate without a higher density foam outer layer
(e.g., Example 1A), creases on the surface.
116. Example 2 is a suitable construction for use in a body board,
for example. Suitable foams balance the stiffness and density
properties for particular applications. The body board product
should be as light as possible, affording the greatest flotation
for its size (i.e., have the lower total density). The surfaces
should resist abrasion (e.g., from sand) and resist absorption of
water (i.e., it should be a closed cell foam). The board should be
stiff enough to resist the mechanical forces imparted to the board
during use (i.e., it should resist creasing). Buckling under
ordinary use is undesirable, since this results in permanent damage
which cannot be repaired.
Example 3
117. A collapsible packaging system was prepared by die cutting a
laminated foam structure. The core foam consisted of four laminated
cross-linked polyethylene foam layers having a thickness of 0.530
inches and a density of 1.7 pcf taken from base roll stock. The
layers were laminated using 1060.degree. F. hot air and a
compression roller nip. Following application of the hot air to the
surfaces to be laminated, two foam sheets were forced together and
padded through a cool roller nip, bonding the two surfaces
together. This afforded a 2 ply laminate that was approximately 1
inch thick. The lamination procedure was repeated twice to afford a
low density core having a density of approximately 2 pcf and a
total thickness of about 2 inches. A skin was laminated to one
surface of the core using the same procedure to produce the
laminated foam structure (i.e., a 6/2/2/2 laminate) for use in a
collapsible packaging system. The skin was a cross-linked
polyethylene foam having a density of 6 pcf and a thickness of
about 1/8inch.
118. The collapsible packaging system was die cut from the
laminated foam structure having a 2 pcf, 2 inch thick laminated
core and a 6 pcf, 1/8inch thick skin on one surface. The rule was
1.5 inches wide and had a serrated, center bevel profile. A 5/8inch
rule board exposed 7/8inches of the rule for cutting. The press
capacity was 100 tons. The die was configured to cut the laminated
foam article in the form shown in FIGS. 7-15, which serves as a
collapsible packaging system.
119. Other embodiments are within the claims.
* * * * *