U.S. patent application number 10/734937 was filed with the patent office on 2004-07-01 for trim articles with light stable covering containing invisible tear seam, and process of making the same.
This patent application is currently assigned to Magna Interior Systems Inc.. Invention is credited to Gardner, John A. JR..
Application Number | 20040126532 10/734937 |
Document ID | / |
Family ID | 32473936 |
Filed Date | 2004-07-01 |
United States Patent
Application |
20040126532 |
Kind Code |
A1 |
Gardner, John A. JR. |
July 1, 2004 |
Trim articles with light stable covering containing invisible tear
seam, and process of making the same
Abstract
A panel structure is mountable in a vehicle to form a part of
the interior thereof in concealing relation to a secondary
restraint system. The novel panel structure of this invention
includes a layered composite structure and a reinforcing substrate
having a door structure movable through the layered composite
structure upon the operation of the secondary restraint system. The
layered composite structure includes an outer layer and an inner
layer adhered to the outer layer, the inner layer including a
seam-defining structure. In one embodiment, the seam-defining
structure is a narrow elongated structure configured to define an
exteriorly invisible tear seam generally corresponding with
portions of an outline of the door structure, and the inner layer
has a reduced thickness portion along the exteriorly invisible tear
seam by virtue of the presence of the narrow elongated structure.
In another embodiment, the seam-defining structure is a sheet
structure severed to define an exteriorly invisible tear seam
generally conforming to an outline of the movable door structure.
The invisible tear seam defined by the narrow elongated structure
or the severed sheet structure causes the layered composite
structure to fracture generally along the invisible tear seam in
response to the movement of the door structure through the layered
composite structure during the operation of the secondary restraint
system.
Inventors: |
Gardner, John A. JR.;
(Deerfield, NH) |
Correspondence
Address: |
RADER, FISHMAN & GRAUER PLLC
39533 WOODWARD AVENUE
SUITE 140
BLOOMFIELD HILLS
MI
48304-0610
US
|
Assignee: |
Magna Interior Systems Inc.
|
Family ID: |
32473936 |
Appl. No.: |
10/734937 |
Filed: |
December 12, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10734937 |
Dec 12, 2003 |
|
|
|
09394032 |
Sep 13, 1999 |
|
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60100124 |
Sep 14, 1998 |
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Current U.S.
Class: |
428/43 ;
280/728.3 |
Current CPC
Class: |
B32B 2375/00 20130101;
Y10T 428/15 20150115; Y10T 428/24273 20150115; B32B 2266/0292
20130101; B32B 2355/02 20130101; Y10T 428/24322 20150115; B32B
27/304 20130101; B29C 2043/186 20130101; B60R 21/2165 20130101;
B32B 27/08 20130101; Y10T 428/23 20150115; Y10T 428/249921
20150401; B32B 2605/00 20130101; B32B 2307/51 20130101; B32B 27/32
20130101; B32B 2369/00 20130101; Y10T 428/24331 20150115; B29L
2031/3008 20130101; B32B 5/18 20130101; B32B 27/40 20130101; B29C
37/0057 20130101 |
Class at
Publication: |
428/043 ;
280/728.3 |
International
Class: |
B32B 033/00 |
Claims
What is claimed is:
1. A process for making a layered composite structure for a panel
structure mountable in a vehicle to part of the interior thereof in
concealing relation to a secondary restraint system, said process
comprising: forming on a mold surface the layered composite
structure comprising an outer layer defining at least a portion of
an exterior surface of the panel structure, an inner layer adjacent
the outer, said inner layer including a seam defining structure
adhered to the inner layer defining a frangible line of an
invisible tear seam corresponding with the secondary restraint
system.
2. A process as defined in claim 1, wherein said forming of the
layered composite structure comprises: establishing the outer layer
on the mold surface so as to have a configuration complementary to
mold surface; applying the seam defining structure on the inner
surface of the outer layer while the outer layer is on the mold
surface; and applying the inner layer over the inner surface of the
outer layer and the seam defining structure applied thereto while
the outer layer is on the mold surface to adhere the outer layer
thereto.
3. A process as defined in claim 1, wherein said forming of the
layered composite structure comprises: establishing the outer layer
on the mold surface so as to have a configuration complementary to
the mold surface; applying a first portion of the inner layer on
the inner surface of the outer layer while the outer layer is on
the mold surface to adhere the outer layer thereto; applying the
seam defining structure on the inner surface of the first portion
of the inner layer while the outer layer is on the mold surface and
positioning the narrow seam defining structure to define the
exteriorly invisible tear seam; and applying a second portion of
the inner layer over the inner surface of the first portion of the
inner layer and the seam defining structure applied thereto while
the outer layer is on the mold surface.
4. A process as defined in claim 1, wherein said forming of the
layered composite structure comprises: establishing the outer layer
on the mold surface so as to have a configuration complementary to
the mold surface; applying the inner layer on the inner surface of
the outer layer while the outer layer is on the mold surface to
adhere the outer layer thereto; applying the seam defining
structure on an inner surface of the inner layer while the outer
layer is on the mold surface; and pressing the narrow seam defining
structure into the inner layer while the inner layer is in a
reactive state to embed the seam defining structure in the inner
layer.
5. A process as defined in claims 2 to 4, wherein the seam defining
structure comprises a thermoplastic material.
6. A process defined in claims 2 to 4, wherein the seam defining
structure comprises a sheet structure.
7. A process as defined in claim 6, wherein the sheet structure
comprises an open mesh fabric.
8. A process as defined in claim 7, where in the open mesh fabric
comprises a fiber glass mat treated with an adhesive coupling agent
compatible to bond with the inner layer.
9. A process as defined in claims 7 or 8 wherein said sheet
structure is severed along said frangible line.
10. A process as defined in claim 9, wherein the severed sheet
structure comprises peripheral walls surrounding the invisible tear
seam and protruding from the inner layer away from the outer
layer.
11. A process as defined in claims 2 to 4, wherein the seam
defining structure comprises twine.
12. A process according to claims 5, 6 or 11, wherein said
establishing of the outer layer on the mold surface comprises:
applying a water-dispersed composition onto the mold surface, the
water-dispersed composition comprising at least one light-stable
thermoplastic polyurethane, at least one coloring agent, and at
least one heat-activated crosslinker, applying sufficient heat to
induce partial crosslinking of the light-stable thermoplastic
polyurethane with the crosslinker, and substantially drying the
water-dispersed composition while on the mold surface so as to
establish the outer layer; and the inner layer is formed by
applying a composition onto an inner surface of the outer layer
and, crosslinking the inner layer which extends about the seam
defining structure with the polyurethane of the outer layer via
residual unreacted functional groups of the crosslinker to form
interfacial chemical bonding between the inner surface of the outer
layer and an adjacent surface of the inner layer.
13. A process according to claim 12, wherein the outer layer has a
thickness in a range of from about 0.0025 cm to about 0.0038
cm.
14. A process according to claim 13, wherein the inner layer has a
thickness in a range of from about 0.10 cm to about 0.15 cm.
15. A process according to claim 12, wherein the mold surface has a
complementary configuration to an exterior surface of a door
panel.
16. A process according to claim 12, wherein the mold surface has a
complementary configuration to an exterior surface of an instrument
panel.
17. A process according to claim 12, wherein the composition from
which the inner layer is formed comprises an aromatic
polyisocyanate, and wherein the crosslinker is a blocked,
heat-activated diisocyanate.
18. A process according to any one of the preceding claims wherein
the process further comprises a step of uniting the layered
composite structure after the formation thereof with a reinforcing
substrate so that the reinforcing substrate reinforces the layered
composite structure in such a way that the layered composite
structure fractures generally along the tear seam in response to
the operation of the secondary restraint system.
19. A process as defined in claim 18, wherein said uniting of the
layered composite structure with the reinforcing substrate
comprises placing a rapid reacting mixture between the layered
composite structure and the reinforcing substrate and forming a
cellular polyurethane foam therefrom.
20. A layered composite structure for a panel structure mountable
in a vehicle to form a part of the interior thereof, said panel
structure having an exterior surface exposed to the vehicle
interior and an interior surface disposed in cooperating and
concealing relation with a secondary restraint system, said layered
composite structure comprising: an outer layer with an opaque
visual appearance defining an exposed exterior surface of said
panel structure; and an inner layer adhered to an inner surface of
said outer layer and including an adhesively bonded seam defining
structure, said seam defining structure defining a frangible line
corresponding to an invisible tear seam which fractures in response
to operation of the secondary restraint system.
21. A layered composite structure as defined in claim 20, wherein
the seam defining structure comprises a thermoplastic material.
22. A layered composite structure defined in claim 20, wherein the
seam defining structure comprises a sheet structure.
23. A layered composite structure as defined in claim 22, wherein
the sheet structure comprises an open mesh fabric.
24. A layered composite structure as defined in claim 23, where in
the open mesh fabric comprises a fiber glass mat.
25. A layered composite structure as defined in claims 22, 23 or 24
wherein said sheet structure is severed along said line.
26. A layered composite structure as defined in claim 25, wherein
the severed sheet structure comprises peripheral walls surrounding
the invisible tear seam and protruding from the inner layer away
from the outer layer.
27. A layered composite structure as defined in claim 20, wherein
the seam defining structure comprises twine.
28. A layered composite structure according to claims 21, 22 or 27,
wherein said outer layer comprises: a water-dispersed composition
comprising at least one light-stable thermoplastic polyurethane, at
least one coloring agent, and at least one heat-activated
crosslinker; and the inner layer is a composition which crosslinks
the inner layer about the seam defining structure with the
polyurethane of the outer layer via residual unreacted functional
groups of the crosslinker to form interfacial chemical bonding
between the inner surface of the outer layer and an adjacent
surface of the inner layer.
29. A layered composite structure according to claim 28, wherein
the outer layer has a thickness in a range of from about 0.0025 cm
to about 0.0038 cm.
30. A layered composite structure according to claim 29, wherein
the inner layer has a thickness in a range of from about 0.10 cm to
about 0.15 cm.
31. A layered composite structure according to claim 28, wherein
the layered composite structure has a configuration of an exterior
surface of a door panel.
32. A layered composite structure according to claim 28, wherein
the layered composite structure has a configuration of an exterior
surface of an instrument panel.
33. A layered composite structure according to claim 28, wherein
the composition from which the inner layer is formed comprises an
aromatic polyisocyanate, and wherein the crosslinker is a blocked,
heat-activated diisocyanate.
34. A layered composite structure according to any one of the
preceding claims wherein the layered composite structure is united
with a reinforcing substrate so that the reinforcing substrate
reinforces the layered composite structure in such a way that the
layered composite structure fractures generally along the tear seam
in response to the operation of the secondary restraint system.
35. A layered composite structure as defined in claim 34, wherein a
rapid reacting mixture which forms a cellular polyurethane foam
unites the layered composite structure and the reinforcing
substrate and therefrom.
Description
[0001] This application is a continuation of application Ser. No.
09/394,032, filed Sep. 13, 1999, which in turn claims the benefit
of Provisional Application No. 60/100,124, filed on Sep. 14, 1998,
the entire contents of which are incorporated herein by
reference.
FIELD OF INVENTION
[0002] This invention relates to interior trim articles containing
a panel structure mountable in a vehicle to form a part of the
interior thereof, and in particular to automobile interior trim
articles, such as instrument panels and door panels, which conceal
a secondary restraint system including an air bag. This invention
further relates to a process for making the aforementioned interior
trim articles.
BACKGROUND OF THE INVENTION
[0003] The escalation of the commercial significance of air bag
restraint systems in automobiles as secondary restraint systems has
manifested itself in the appearance of air bag restraint systems in
many, if not most, new automobiles. The commercial impact of such
secondary systems is attributable both to government regulations
and consumer demand for safety.
[0004] Generally, air bag restraint systems are concealed from view
during normal operation of the vehicle by arranging the air bag
restraint systems behind automotive interior trim articles, such as
instrument panels and/or door panels.
[0005] In order to permit the deployment of the air bags upon
collision of the vehicle, interior trim articles are often formed
with a multi-layered structure comprising a rigid substrate having
hidden doors formed therein, an outer decorative skin layer, and a
soft cellular polyurethane foam layer formed therebetween. The
hidden doors of the rigid substrate are configured and arranged in
such a manner that the edges of the doors define discernible
patterns, such as patterns in the form of H, C, U, and X
shapes.
[0006] During deployment of the air bag, the air bag is actuated
via a gas generating system and expands from a folded, undeployed
state to an inflated, deployed state. The expansion of the gas
inflates the air bag against the backside of the hidden doors and
forces the hidden doors to open into the passengers' compartment of
the vehicle. The emergence of the hidden doors into the passengers'
compartment creates a passageway which permits deployment of the
air bag into the passengers' compartment of the vehicle. The
deployed air bag protects the driver and passenger from violent
collision against the panel structure.
[0007] In order to minimize obstruction of the passageway through
which the expanding air bag traverses, the underside of the outer
skin can be provided with structurally weakened tear seams. These
tear seams often take the form of perforated or channel-like
patterns, and are constructed and arranged to substantially
correspond to and overlay the pattern (e.g., H-shaped) defined by
the edges of the hidden doors of the substrate. During deployment
of the air bag, the outer skin tears or fractures along the
structurally weakened tear seams. Absent the presence of such
structurally weakened tear seams in the outer skin, the outer skin
may possess sufficient internal strength to resist fracture upon
deployment of the rapidly expanding air bag. If the skin does not
fracture, the entire outer skin can become separated from the rigid
substrate and/or the multi-layered structure can be dismounted from
the vehicle frame, thereby imperiling the safety of the driver and
passengers.
[0008] Different techniques have been proposed to form a
multi-layered structure having an outer skin with a structurally
weakened, rupturable tear seam. One conventional technique involves
the preparation of a rotational-cast poly(vinyl chloride) ("PVC")
skin by providing a powder box including a seam-defining structure
or gasket, which partitions the powder box into two chambers. A PVC
powder with appropriate colorants and additives, such as
plasticizers, is retained in each of the chambers. Where a
dual-tone appearance is desired, the chambers can be supplied with
PVC powders containing different colorants, in which case the
seam-defining structure simultaneously serves as a color division
rim. The powder box is then engaged to a metal mold component to
define a closed casting system having the seam-defining structure
closely spaced from a heated mold surface of the metal mold
component. The PVC powder is then tumbled against a heated molding
surface of the metal mold by a rotational casting method until the
PVC powder is formed against a moderately heated mold surface in a
gelled state. Excess powder collects in the powder box, and is
thereafter separated and removed from the mold. Since the
seam-defining structure obstructs the gelling of PVC powder on the
portion of the heated mold surface therebelow, the structurally
weakened portion of the skin is formed below the seam-defining
structure. A lower density or lower strength tear seam material
(also referred to as a filler material) is then sprayed into the
perforated or channel-like seams and gelled. The gelled PVC
material and the gelled tear seam material are then fused by
heating the materials to their fusion temperatures, and thereafter
cooled to provide the PVC-based covering in a thermoplastic solid
state. The skin can then be united with the rigid substrate, such
that the low density material of the outer skin is positioned to
substantially correspond to and overlay the edges of the hidden
doors.
[0009] There are at least two problems associated with the
above-described conventional method. First, the presence of the
seam-defining structure hinders the normal compacting of the PVC
powder which occurs during rotation of the closed system. Hence,
the portion of the skin layer corresponding to the structurally
weakened tear seam possesses a greater porosity than the remainder
of the skin. The difference in porosity between the structurally
weakened portion and the remaining portion of the outer skin makes
the pattern of the tear seam visible, especially in bright light.
The second problem is due to the difference in composition of the
cast skin and the sprayed tear seam material. In top-mount
applications in which the tear seam is exposed to high temperatures
and intense UV radiation, the sprayed material introduced into the
tear seam ages differently than the surrounding cast material and
will become clearly visible over time. For these reasons,
multi-layered structures made by the aforementioned conventional
method are only effectively employed in mid mount applications
where the hidden tear seam is not exposed to direct sunlight.
[0010] In order to overcome these problems, it has been proposed to
form a PVC skin layer of uniform thickness, and thereafter form the
structurally-weakened tear seams by laser cutting the backside of
the skin. Due to the relatively small thickness of the skin,
however, it is very difficult to precisely control the depth of the
cut portion. Consequently, errors in laser cutting can lead to the
disposal of skins as unusable scrap. In addition, the capital
investment associated with obtaining and operating a laser cutting
apparatus is very high.
[0011] A need therefore exists to provide a process for making a
panel structure containing a decorative covering having an inner
surface with a structurally weakened tear seam in which the tear
seam is concealed from view, even after employing the covering in
top mount applications which subject the covering to prolonged use
and exposure to high temperatures and intense UV radiation.
SUMMARY OF THE INVENTION
[0012] The disadvantages of the prior art may be overcome by
providing a process for making a panel structure comprising a
layered composite structure and a reinforcing substrate including a
door structure movable through a portion of the layered composite
structure upon the operation of the secondary restraint system. The
panel structure is mountable to a vehicle to form a part of the
interior thereof in concealing relation to a secondary restraint
system.
[0013] In accordance with one embodiment of this inventive process,
the layered composite structure is formed on a mold surface, the
layered composite structure comprising an outer layer with an
exterior surface having an opaque visual appearance, a seam
defining structure configured to define an exteriorly invisible
tear seam generally corresponding with portions of an outline of
the door structure movable through the layered composite structure
during the operation of the secondary restraint system, and an
inner layer having a frangible line along the exteriorly invisible
tear seam by virtue of the presence of the seam defining structure.
The layered composite structure is united with the reinforcing
substrate so that the reinforcing substrate reinforces the layered
composite structure in such a way that the narrow elongated
structure and the reduced thickness portion of the inner layer
along the invisible tear seam causes the layered composite
structure to fracture generally along the invisible tear seam in
response to the movement of the door structure through the layered
composite structure during the operation of the secondary restraint
system. Optionally, a soft cellular foam layer can be interposed
between the layered composite structure and the reinforcing
substrate.
[0014] In accordance with another embodiment of this inventive
process, the layered composite structure is formed on a mold
surface and comprises an outer layer with an exterior surface
having an opaque visual appearance and an inner layer adhered to
the outer layer and including a seam defining structure in the form
of a severed sheet structure through which the door structure moves
during the operation of the secondary restraint system. The layered
composite structure and the substrate are united so that the
substrate reinforces the layered composite structure. The sheet
structure is severed to define an exteriorly invisible tear seam
generally corresponding with portions of an outline of the door
structure. The severed portion defining the invisible tear seam
causes the layered composite structure to fracture generally along
the invisible tear seam in response to the movement of the door
structure through the layered composite structure during the
operation of the secondary restraint system. A soft cellular foam
layer optionally can be interposed between the layered composite
structure and the reinforcing substrate.
[0015] Other objects of the invention are achieved by providing an
article comprising a panel structure made by the above-mentioned
embodiments of the inventive process of this invention.
[0016] Since the layered composite structures provided in
accordance with the above-discussed embodiments have an outer layer
that can be uniformly sprayed onto heated mold surface without
requiring a seam-defining structure for forming a structurally
weakened seam in the outer layer, the outer layer of the composite
structure does not exhibit the non-uniform porosity that
characterizes conventional skins. Further, the outer layer assists
in masking and concealing the non-uniform porosity and/or
differentials in aging between the portion of the layered composite
structure defining the structurally weakened tear seam.
[0017] The layered composite structure of this invention also
exhibits excellent chemical, scuff and mar resistance to external
influences. Further, appropriate additives can be introduced into
one or more of the layers of the layered composite structure to
provide the composite structure with the non-reflective and low
gloss surface appearance desired for such panel-like structures.
Furthermore, both the inner and outer layers of the layered
composite structure are characterized by excellent extensibility,
such that the layered composite structure can withstand indentation
and flexure during use without resulting in cracking in the outer
layer over a wide temperature range, such as from -30EC to
120EC.
[0018] The principles of this invention enunciated above are
applicable to all types of skinned panel structures through which
an air bag might deploy, but have particular applicability to
instrument panels (also referred to as dashboards), door panels,
steering wheels, pillar covers, headliners, and rear interior
quarter panels. Moreover, the principles of this invention are
applicable to various types of automotive vehicles, including
passenger cars, trucks, vans, utility vehicles, and others.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The accompanying drawings illustrate this invention. A first
embodiment of the invention is illustrated in FIGS. 1-12, in
which:
[0020] FIG. 1 is a perspective, partially phantomed view of a
completed vehicle instrument panel constructed in accordance with a
first embodiment of this invention;
[0021] FIG. 2 is a sectional view of the instrument panel of a FIG.
1 taken along line II-II;
[0022] FIG. 3 is a sectional view showing the air bag in a
partially inflated deployment position;
[0023] FIG. 4 is a sectional view like FIG. 3, except showing the
air bag in a fully inflated deployment position;
[0024] FIG. 5 is a sectional view of a mold surface showing a step
of applying a water-dispersed polyurethane composition to a heated
mold surface to form a partially crosslinked light-stable
polyurethane outer layer;
[0025] FIG. 6 is a sectional view similar to FIG. 5 showing a step
of drying the polyurethane outer layer;
[0026] FIG. 7 is a depiction of one construction and arrangement of
a narrow elongated structure of the first embodiment;
[0027] FIG. 8 is a depiction of another construction and
arrangement of a narrow elongated structure of the first
embodiment;
[0028] FIG. 9 is a sectional view similar to FIG. 6 showing a
layered composite structure formed on the heated mold surface;
[0029] FIG. 10 is a sectional view similar to FIG. 9 showing a step
of removing the layered composite structure from the mold
surface;
[0030] FIG. 11 is a sectional view showing a step of depositing a
relatively rigid polyurethane cellular foam intermediate layer on
the inner layer while the layered composite structure is disposed
on a second mold surface; and
[0031] FIG. 12 is a sectional view showing a step of uniting the
layered composite structure on the second mold surface with a
pre-formed relatively rigid substrate disposed on a third mold
surface.
[0032] A second embodiment of the invention is illustrated in FIGS.
13-17, in which:
[0033] FIG. 13 is a perspective, partially phantomed view of a
completed vehicle instrument panel constructed in accordance with a
second embodiment of this invention;
[0034] FIG. 14 is a sectional view of the instrument panel of a
FIG. 13 taken along line XIV-XIV;
[0035] FIG. 15 is a depiction of one construction and arrangement
of a thin sheet structure of the second embodiment;
[0036] FIG. 16 is a depiction of another construction and
arrangement of a thin sheet structure of the second embodiment;
[0037] FIG. 17 is a sectional view showing a step of uniting the
layered composite structure on the second mold surface with a
pre-formed relatively rigid substrate disposed on a third mold
surface; and
[0038] FIG. 18 is a depiction of another construction and
arrangement of a thin sheet structure of the second embodiment.
DETAILED DESCRIPTION OF THE INVENTION
[0039] Referring now more particularly to the drawings, there is
shown in FIG. 1 a panel structure comprising a vehicle instrument
panel, generally designated by reference numeral 10, made by a
method in accordance with a first embodiment of this invention.
[0040] In this embodiment of the invention, the panel structure 10
is shown in a top mount position. The structure 10 includes pivotal
doors 12 having edges that define a hidden H-shaped pattern 14. In
this top mount position, the panel structure 10 underlays a sloped
windshield 16. Although shown in the upper portion of the
instrument panel 10, it is understood that the doors 12 could also
be formed in the front portion of the instrument panel 10, which
constitutes a mid mount position.
[0041] As shown in cross-section in FIGS. 2 and 3, the panel
structure 10 has an exterior surface 10a exposed to the vehicle
interior and an interior surface 10b which is hidden from the
vehicle interior when the panel structure 10 is mounted in the
automobile vehicle. The panel structure 10 includes a rigid (or
reinforcing) substrate 22 having one surface defining the interior
surface 10b of the panel structure 10. A portion of the substrate
22 defines the pivotal doors 12. Alternatively, the pivotal doors
12 can be formed separately from the substrate 22, and attached to
the substrate 22 via, for example, hinges or the like (not shown).
In the illustrated embodiment, when viewed from the backside of the
substrate 22, the doors 12 define an H-pattern; however, it is
understood that the doors 12 can define other patterns and can be
displaced by other means (other than pivotal movement). For
example, other possible patterns include X, C, U, and inverted U
shapes.
[0042] The panel structure 10 further includes a layered composite
structure, generally designated by reference numeral 24 (FIG. 2),
comprising an outer layer 26 having an outer surface 26a defining
at least a portion of the exposed exterior surface 10a (FIG. 4) of
the panel structure 10, a seam defining structure, namely a thin
narrow elongated structure 27, and an inner layer 28. At least a
portion of the outer layer 26 is exposed to the vehicle interior,
while a portion of the outer layer 26 may be hidden from view by a
decorative or other masking item. An intermediate layer 30
comprising a relatively rigid (or semi-rigid) polyurethane cellular
foam is interposed between the layered composite structure 24 and
the substrate 22.
[0043] The inner layer 28, which is relatively thick in comparison
to the outer layer 26, has an outer surface adjacent to both a
portion of an inner surface 26b of the outer layer 26 and the
narrow elongated structure 27. Preferably, the inner layer is
interfacially chemically bonded with the outer layer 26. The narrow
elongated structure 27 preferably has a shape that substantially
corresponds to the shape of the edges of the doors 12 that part
from the substrate 22 during pivoting movement of the doors 12
(e.g., an H-shape in the illustrative embodiment). Generally, the
narrow elongated structure 27 can be made of a material having a
lower tensile strength than that of the inner layer 28. Preferably,
the tensile strength of the narrow elongated structure 27 is about
50% lower than that of the inner layer 28, thus defining a
frangible line or an inherent line of weakness. The density and/or
tensile strength of the elongated structure 27 can be lowered by
including silica, glass beads, talc, and other fillers, and/or by
adding blowing agents, such as azo-blowing agents, into the
elongated structure 27. The elongated structure 27 is made of or
coated with a material which is chemically and adhesively
compatible with the material of the inner layer 28.
[0044] In the illustrated embodiment of FIG. 3, an air bag
deployment system 40 used in combination with this invention can
include any conventional system disposable behind a panel-like
structure and capable of deploying an air bag 42 at an adequate
rate to protect the vehicle occupants. A typical system 40 can
include, for example, a stationary gas generator or canister 44
situated in a housing 46 mounted on a suitable vehicle component
(not shown). When the vehicle is impacted, an impact sensor 48
actuates the gas generator 44, causing the gas generator 44 to
condition a controller 49 to initiate gas generation and expel a
suitable inflatant gas into the air bag 42.
[0045] As shown in FIGS. 3 and 4, as the air bag 42 is inflated
from its folded, undeployed state to a fully inflated, deployed
state, the expanding air bag 42 impacts against the backside of the
panel structure 10. The force of the impact displaces the doors 12
into the passengers' compartment of the vehicle and thereby
fractures the composite structure 24 along the narrow elongated
structure 27 to create a passageway (unnumbered). The formed
passageway permits expansion of the air bag 42 into the passengers'
compartment of the vehicle and protects the occupants from violent
collision against the panel structure 10 or windshield 16.
[0046] As shown in FIG. 5, the method of this first embodiment is
generally described in U.S. Pat. No. 5,885,662 and utilizes a first
mold component or part 50 having a first mold surface 52. The first
mold component 50 preferably is formulated by electrolytically
depositing nickel over a rigid cast epoxy substrate which is
secondarily removed at the end of the deposition/plating process to
yield a self-supporting mold capable of being mounted and
controlled in a tooling module. The first mold surface 52 has a
complementary configuration to the desired configuration of the
outer layer 26, and is grained to define a texture that
substantially complements the desired texture of the outer layer 26
and simulates real leather.
[0047] FIG. 5 illustrates the first step in this embodiment in
which the outer layer 26 is obtained by applying, preferably by
spraying, a water-dispersed composition 54 onto the first mold
surface 52. The water-dispersed composition 54 comprises at least
one light-stable aliphatic thermoplastic polyurethane containing
one or more pendent hydroxyl and/or carboxyl functional groups, at
least one desired coloring agent, and at least one heat-activated
crosslinker. Suitable crosslinkers include blocked, heat-activated
aliphatic diisocyanates, carbodiimide (H_N.dbd.C.dbd.N_H), also
known as cyanamide, and compounds having a plurality of aziridine
groups. The average molecular weight of the thermoplastic
polyurethane can be in a range of from about 5000 to about 7000,
and more preferably about 6000. An exemplary thermoplastic
polyurethane and blocked, heat-activated aliphatic diisocyanate can
be obtained from Titan Finishes Corp. of Detroit, Mich. under the
trade designation PROTOTHANE WR, WATER BASED IN-MOLD COATING. The
aliphatic diisocyanate may be cyclic or non-cyclic, but should be
light stable. As referred to herein, diisocyanates also encompasses
prepolymers having two _NCO groups which are reactive with the
thermoplastic polyurethane. An exemplary aliphatic diisocyanate is
hexamethylene diisocyanate (HMI), which is available from Bayer,
Rhone Poulenc, and Nippon Polyurethane. An exemplary
water-dispersed composition comprising a thermoplastic polyurethane
and carbodiimide can be obtained from C.F. Jameson & Company,
Inc. of Bradford, Mass. under the trade designation JAMESON WVF
SERIES FLEXCOAT IMC. The desired weight ratio of thermoplastic
polyurethane to crosslinker for these particular compositions is
about 8 to 1 by volume (equivalent ratio of 1.44 thermoplastic
polyurethane to 1.08 crosslinker on a dry basis).
[0048] The water-dispersed composition 54 can be prepared by
providing the thermoplastic polyurethane component as a colloidal
solution in a solvent such as N-methyl pyrrolidone, then dispersing
the solution by adding water, the coloring agent, and conventional
additives, if desired. Sufficient water (e.g., about 61.1% by
weight) can be added so that the solvent concentration in the
water-dispersed composition 54 is, for example, about 8.1% by
weight before drying.
[0049] The optional additives in the water-dispersed composition 54
can include, without limitation, any combination of the following:
heat and ultra-violet light stabilizers, pH stabilizers to maintain
an alkaline state of dispersion, plasticizers, antioxidants,
dulling agents, surfactants, colloidal protectants to maintain
particles in suspension, carbon black, thixotropic agents (e.g.,
hydroxy methyl cellulose), and fillers such as clay particles.
[0050] The water-dispersed composition 54 can contain, for example,
about 25% to about 35% solids by weight, and more preferably about
29% solids by weight, about 10% to about 80% water by weight, and
more preferably about 61% water by weight, and about 6% to 10%
solvents by weight, depending on desired color and additives. An
insufficient amount of water in the composition 54 can adversely
affect the viscosity of the composition 54 and thus adversely
affect the application of the water-dispersed composition 54 onto
the first mold surface 52. On the other hand, an excess amount of
water in the water-dispersed composition 54 can alter the
sprayability and coating efficiency of the water-dispersed
composition 54.
[0051] To the thermoplastic polyurethane solution may be added a
solution of the blocked, heat-activated aliphatic diisocyanate,
which can include as a solvent, for example, 1-methyl-2-pyrrolidine
and/or 4-hydroxy-4-methyl-2-pentanone. A discussion of blocked
isocyanates is included in Practical Chemistry of Polyurethanes and
Diisocyanates, Akron Polymer Laboratories, David Russell (1991),
the complete disclosure of which is incorporated herein by
reference. The blocked, heat-activated aliphatic diisocyanate is
preferably maintained at room temperature and protected from heat
until use. When influenced by the heat, such as the heat of the
tooling during spraying application, the blocked, heat-activated
aliphatic diisocyanate reacts with the hydroxyl and/or carboxyl
groups of the thermoplastic polyurethane to crosslink the
thermoplastic polyurethane with itself or with polyol constituents
of the rapidly reacting composition.
[0052] Alternatively, the water-dispersed composition 54 can be
prepared by adding to the thermoplastic polyurethane solution a
solution comprising the carbodiimide, which can include, for
example, glycol ether acetate and/or xylene as the solvent.
[0053] The water-dispersed composition 54 can be prepared by
withdrawing the light-stable thermoplastic polyurethane and the
heat-activated crosslinker from separate storage chambers in
continuous, metered streams, and mixing these constituents
immediately prior to contact with the first mold surface 52.
Alternatively, the light-stable aliphatic thermoplastic
polyurethane and the crosslinker constituents can be stably
premixed, or "hot-potted", for up to about 24 hours at room
temperature before application. This technique is known as
"hot-potting" since the thermoplastic polyurethane and crosslinker
slowly react with each other at room temperature in a spray
pressure pot. If the admixture is hot-potted for more than about 24
hours at room temperature before application of the water-dispersed
composition 54 onto the first mold surface 52, the resulting
crosslinked light-stable polyurethane exhibits inferior solvent and
wear resistance properties and extensibility and may not provide an
idealized bond to the inner layer 28. The water-dispersed
composition 54 may be formed from a colloidal solution of resin
particles, which is added to water to disperse the resin particles
in the water.
[0054] Application of the water-dispersed composition 54 onto the
heated first mold surface 52 induces chemical reaction between the
pendent hydroxyl and/or carboxyl functional groups of the
light-stable thermoplastic polyurethane and the heat-activated
crosslinker to thereby produce a partially crosslinked light-stable
polyurethane. The first mold surface 52 should be heated to a
sufficient temperature to drive the crosslinking reaction, but
should not be so high as to cause delamination of the composition
54 from the mold surface 52. Preferably, the first mold surface 52
is heated to a temperature in a range of from about 60EC (140EF) to
about 71.1EC (160EF). The heating of the first mold surface 52 to
such elevated temperatures prior to application of the
water-dispersed composition 54 thereto also serves to melt and
disperse semi-permanent mold releasing agents, such as
microcrystalline wax mold releasing agents, applied to the first
mold surface 52. The heated mold surface 52 evaporates the wax
dispersants and leaves a thin residue that does not collect in the
intricate grain detail of the first mold surface 52.
[0055] Once the crosslinked light-stable polyurethane has been
formed on the first mold surface 52, the water-dispersed
composition 54 is substantially dried while being retained on the
first mold surface 52 to obtain the outer layer 26. As shown in
FIG. 6, the partially crosslinked light-stable polyurethane can be
subjected to a heat source 56 to induce evaporation of the water
and solvent therefrom and coalesce the resin particles to form the
outer layer 26 with the outer surface 26a adjacent to the first
mold surface 52. Although not shown in FIG. 6, such heat source 56
is preferably integrated with the first mold 50, and preferably
heats the first mold surface 52 to an elevated temperature of about
65.6EC (150EF) or higher. At least a portion of the outer surface
26a of the outer layer 26 has the desired touch, color, and
grain-like configuration of the panel-like structure 10.
[0056] Generally, the outer layer 26 has a thickness in a range of
from about 0.0025 cm to about 0.0038 cm (that is, from about 0.001
inch to about 0.0015 inch; or from about 1.0 mils to about 1.5
mils). The particular coloring agent selected can directly
influence the desired thickness of the outer layer 26. Darker
colors, such as grays and browns, usually only require a relatively
small film thickness to mask the color of the hidden elongated
structure 27 and the inner layer 28, whereas lighter colors such as
reds and blues usually dictate the provision of a relatively larger
thickness to obtain an opaque, non-transparent outer layer 26 that
conceals the structure 27 and the elongated inner layer 28 from
view.
[0057] In accordance with a variant of the present invention, the
outer layer 26 can exhibit a dualtone or multitone appearance. This
variant embodiment can be accomplished, for example, by abrasive
treatment of a portion of the mold surface of the tooling. The
greater the amount of abrasive treatment, the duller the appearance
of the outer layer 26. A dualtone appearance can be especially
desirable for instrument panels, since the upper region of an
instrument panel generally should have a low gloss in order to
reduce reflectance and veiling glare.
[0058] A secondary or alternative heat source can be applied for
activating the reaction between the light-stable thermoplastic
polyurethane and the crosslinker. For example, the water-dispersed
composition 54 can be preheated before being applied to the first
mold surface 52, such that the first mold surface 52 does not have
to be heated to initiate the reaction between the crosslinker and
the light-stable thermoplastic polyurethane.
[0059] Referring to FIGS. 7 and 8, there are shown different
constructions and arrangements of the seam defining structure. As
shown in FIG. 7, according to one embodiment the narrow elongated
structure 27a may be a strip of film, and may be made from, by way
of example, a thermoplastic material, including, by way of example,
a polyester, polyurethane, and/or polyamide (nylon). In one
preferred embodiment, the elongated structure 27 is made of MYLAR.
The width of the tape may be on the order of from about 2 mm to
about 3 mm, and its thickness may be on the order of from about 0.1
mm to about 0.2 mm.
[0060] As shown in FIG. 8, the seam defining structure may be in
the form of a string or twine. The string or twine may be, for
example, from about 1 mm to about 1.5 mm in diameter. Any material
that is capable of being formed into a twined configuration to
create a disruption into the structure, without introducing a
foreign entity that will cause the string or twine to significantly
expand or contract over time that might cause "read-through", may
be used. Materials that are similar to those selected for the inner
layer are preferred. The physical properties, including
extensibility, of the twine or string (or the elongated strip) may
be selected to cause tearing in the twine or string (or the
elongated strip) and/or at the interface of the twine or string (or
the elongated strip) and the inner layer 28 in a controlled and
predictable way. Accordingly, the twine or string material 27b (or
elongated strip 27a) may be non-homogenous, and may have a lesser
or greater tensile strength than the inner layer 28. However, the
elongated structure 27 should be made of a material that, during
and after deployment, will not fragment or be sufficiently stiff to
injure the driver or passenger.
[0061] Returning to the process, as shown in FIG. 9, the narrow
elongated structure 27 is applied onto the inner surface 26b of the
outer layer 26. The elongated structure 27 is positioned and
configured to define an exteriorly invisible tear seam generally
corresponding with a portion of an outline of the doors 12 movable
through the layered composite structure 24 during the operation of
the secondary restraint system 40. Next, an inner layer 28 is
deposited over the inner surface 26b of the outer layer 26 and the
thin narrow elongated structure 27 applied thereto while the outer
layer 26 is retained on the first mold surface 52 in a
substantially dry state. The thin narrow elongated structure 27
adheres to the inner layer 28. The adhesive bond between the
elongated structure 27 is inherently less than the interfacial bond
between inner layer 28 and outer layer 26 creating a frangible line
in the inner layer 28 along the exteriorly invisible tear seam.
[0062] Next, the polyurethane elastomer inner layer 28, as is also
depicted in FIG. 9, is formed by spraying a rapidly reacting
composition onto the inner surface 26b of the outer layer 26 while
the outer layer 26 is retained on the first mold surface 52 in a
substantially dry state.
[0063] It is to be understood that the above-discussed sequence of
applying the narrow elongated structure 27 and the inner layer 28
may be reversed or modified. For example, in one alternative
embodiment a first portion of the inner layer 28 is applied onto
the inner surface 26b of the outer layer 26 while the outer layer
26 is on the mold surface 52, but before the narrow elongated
structure 27 has been applied thereto. The narrow elongated
structure 27 is then applied onto the first portion of the inner
layer 28 while the first portion is still tacky so that the
elongated structure 27 is spaced from the inner surface 26b of the
outer layer 28, thereby decreasing the likelihood of "read-through"
of the pattern of the elongated structure 27. A second portion of
the inner layer 28 is then applied over both the first portion of
the inner layer 28 and the narrow elongated structure 27 applied
thereto while the outer layer 26 is on the mold surface 52. The
second portion of the inner layer 28 can be applied in such a
thickness so that the elongated structure 27 is partially exposed
or completely encapsulated by the inner layer 28.
[0064] In another alternative method, the inner layer 28 is applied
on the inner surface 26b of the outer layer 26 while the outer
layer 26 is on the mold surface 52, but before the narrow elongated
structure 27 has been applied thereto. The narrow elongated
structure 27 is then applied on an inner surface 28b of the inner
layer 28 (while the inner layer 28 is still tacky and not fully
reacted, i.e. in a reactive state) and pressed into the inner layer
28 to embed the narrow elongated structure 27 in the inner layer 28
and create, by virtue of the presence of the embedded narrow
elongated structure 27, the exteriorly invisible tear seam. Again,
spacing the narrow elongated structure 27 from the inner surface
26b of the outer layer 26 decreases the chance of read-through.
[0065] The inner layer 28 can be made from one or more base
polymers that can be sprayed or cast by conventional techniques.
Suitable base polymers include, for example and without limitation,
PVC, thermoplastic polyurethanes, thermoplastic polyolefins,
thermoplastic elastomers, and any combination thereof. The
composition for forming the inner layer 28 can also contain one or
more additives. Preferably, at least one of the base polymers
and/or the additives is highly reactive with unreacted, residual
functional groups of the crosslinker in the outer layer 26 that
have not reacted with the pendent functional groups of the
polyurethane of the outer layer 26. Unreacted functional groups of
the crosslinker penetrate into the inner layer 28 and provide
reactive sites for crosslinking the polyurethane of the outer layer
26 with the inner layer 28. An interfacial chemical bond between
the inner surface 26b of the outer layer 26 and the adjacent outer
surface 28a of the inner layer 28 can thereby be formed. The
layered composite structure 24 is thus obtained. If the
crosslinking is performed under optimum crosslinking conditions,
the boundary between the outer and inner layers 26 and 28 about the
seam defining structure of the layered composite structure 24 can
become visually indistinct, such that a transition phase appears at
the interface of the two layers. As referred to herein, interfacial
chemical bonding encompasses, but is not limited to, such
crosslinking reactions in which the interfacial boundary between
the outer and inner layers 26 and 28 is visually indistinct and the
layers 26 and 28 are inseparable.
[0066] In a preferred embodiment, the inner layer 28 is prepared
from a polyurethane elastomer, and even more preferably from an
aromatic polyurethane elastomer. The polyurethane elastomer inner
layer 28 may be formed by spraying a rapidly reacting composition
onto the inner surface 26b of the outer layer 26 and optionally the
elongated structure 27, which are retained on the first mold
surface 52 in a substantially dry state. The rapidly reacting
composition preferably contains at least one aromatic
polyisocyanate and at least one polyol, which react with each other
to form the non-light-stable polyurethane elastomeric inner layer
28. As referred to herein, the term elastomer encompasses a
resilient polymer composition stretchable under moderate tension
and compressible and having a relatively high tensile strength and
memory so that, upon release of the tension, the elastomer retracts
into and recovers its original dimensions or dimensions
substantially similar to its original dimensions.
[0067] In addition to being reactive with the polyisocyanate, the
polyol of the rapidly reacting composition can contain one or more
pendent hydroxyl and/or carboxyl functional groups that are highly
reactive with unreacted functional groups of the crosslinker, which
is preferably a blocked, heat-activated aliphatic diisocyanate, in
the outer layer 26 that have not reacted with the pendent
functional groups of the polyurethane of the outer layer 26.
Unreacted functional groups of the blocked, heat-activated
light-stable diisocyanate penetrate into the inner layer 28 and
react with the pendent functional groups of the polyol constituent.
As a result, the blocked, heat-activated light-stable diisocyanate
crosslinks the polyurethane of the outer layer 26 with the
polyurethane elastomer of the inner layer 28 and thereby forms an
interfacial chemical bond between the inner surface 26b of the
outer layer 26 and the adjacent outer surface 28a of the inner
layer 28. The layered composite structure 24 is thus obtained.
[0068] Generally, provisions should be taken to ensure that an
adequate interfacial chemical bond is achieved between the inner
surface 26b of the outer layer 26 and the adjacent outer surface
28a of the inner layer 28. For example, once the blocked,
heat-activated light-stable diisocyanate is activated by heat, the
crosslinking reaction between the heat-activated diisocyanate and
the pendent hydroxyl and/or carboxyl reactive groups of the
thermoplastic polyurethane goes to completion within minutes,
leaving the heat-activated light-stable diisocyanate with
substantially no residual reactive sites for crosslinking the
polyurethane of the outer layer 26 with the polyol of the rapidly
reacting composition. Therefore, the rapidly reacting composition
generally should be sprayed within six minutes, and preferably
within two to four minutes, of completing the application of the
water-dispersed composition 54 to the first mold surface 52.
Significant delays in spraying the rapidly reacting composition
also can cause the outer layer 26 to constrict and delaminate from
the first mold surface 52. As a consequence of delamination, the
outer layer 26 will not have a shape complementary to the
configuration of the first mold surface 52, and the entire
composite 24 will have to be disposed of as scrap.
[0069] On the other hand, if the thermoplastic polyurethane of the
water-dispersed composition 54 is not given sufficient time to
crosslink before the rapidly reacting composition is sprayed
thereon, the polyol component of the rapidly reacting composition
can undergo a condensation reaction with unreacted hydroxyl and/or
carboxyl pendent functional groups of the polyurethane of the outer
layer 26 to form ester or ether linkages, respectively. While some
formation of these linkages can advantageously enhance the
interfacial chemical bond, the condensation reactions release
water, which in excess amounts can undesirably increase the
cellularity of the inner layer 28 and interfere with the
interfacial chemical bond.
[0070] The interfacial chemical bond is further enhanced by
separately storing the highly reactive polyol and aromatic
polyisocyanate components of the rapidly reacting composition in
separate storage chambers and spraying these components on the
inner surface 26b of the outer layer 26 so as to avoid contact
between these components until spraying is conducted. A suitable
dual nozzle spraying mechanism for accomplishing this task is
disclosed in U.S. Pat. Nos. 5,028,006 and 5,071,683. By keeping
these components separate until immediately prior to spraying, a
portion of the polyol reacts with the heat-activated aliphatic
diisocyanate (and the hydroxyl and/or carboxyl pendent functional
groups of the thermoplastic polyurethane) before all of the polyol
can completely react with the polyisocyanate.
[0071] Furthermore, given the hygroscopic nature of the aromatic
polyisocyanate component of the rapidly reacting composition, it is
important that the outer layer 26 and the surrounding atmosphere
(e.g., humidity levels) be substantially dry during this spraying
step in order to obtain a strong interfacial chemical bond. While
small amounts of moisture may be retained in the outer layer 26,
the concentration of such moisture should not be so great as to
permit the water to substantially interfere with the reaction
between the polyol and polyisocyanate of the rapidly reacting
composition. Undesirable reactions between the water and the
polyisocyanate can disrupt the stoichiometric balance between the
polyol and the polyisocyanate, leaving localized unreacted polyol
deposits behind on the layered composite structure 24. The water
also can serve as a blowing agent, reacting with the polyisocyanate
to release carbon dioxide which imparts a cellular structure to the
inner layer 28. Excess amounts of water also can deleteriously
interfere with the crosslinking reaction effected via the polyol
and the residual reactive sites of the blocked, heat-activated
diisocyanate.
[0072] The rapidly reacting composition is preferably applied to
the inner surface 26a of the outer layer 26 at an elevated
temperature to advance these objectives. Suitable temperatures to
which the first mold component 52 can be heated range, by way of
example and without limitation, from about 60EC (140EF) to about
71.1EC (160EF).
[0073] As mentioned above, the inner layer 28 can also be formed by
casting, for example, a PVC or thermoplastic polyurethane casting
composition. Suitable techniques and apparati for accomplishing
casting are disclosed in the collection of WO 98/57790, U.S. Pat.
No. 4,623,503, U.S. Pat. No. 4,621,995, U.S. Pat. No. 5,597,586,
and U.S. Pat. No. 4,217,325.
[0074] Generally, the inner layer 28 can have a thickness in a
range of from about 0.10 cm to about 0.15 cm (that is, from about
0.040 inch to about 0.060 inch; or from about 40 mils to about 60
mils).
[0075] Aromatic Polyurethane Elastomer Inner Layer
[0076] Exemplary polyisocyanates that can be selected for forming
the inner layer 28 include diisocyanates having aromatic
closed-ring structures, such as diphenylmethane diisocyanate
prepolymer (MDI prepolymer), which can be obtained from BASF Corp.
of Wyandotte, MI. under the trade designation ELASTOLIT M50555T,
ISOCYANATE, NPU U05275, or diphenylmethane-4,4'-diisocyanate (MDI),
or mixed isomers of MDI or mixtures of the above, which are
available from BASF or Dow Chemical Corp. of Midland, Mich., Mobay
(Bayer) Chemical Corp. of Baytown, Tex., or ICI America of Geismar,
La. The above-mentioned non-light-stable aromatic polyisocyanates
are very desirable for use in the inner layer in view of the higher
rate of reactivity and completion of property development and
better physical properties (e.g., tensile strength, elongation, and
tear strength) of these non-light-stable aromatic polyisocyanate
when compared to light-stable isocyanates such as isophorone
diisocyanates, in which the --NCO groups are sterically hindered
due to their spatial arrangement at either end of the molecule. By
contrast, the aromatic diisocyanates used in this invention
preferably have --NCO groups directly attached to the aromatic
ring. In this preferred embodiment, the aromatic diisocyanates
yield faster rates of reaction because of the arrangement and
reactivity of the --NCO groups on the aromatic ring structure
(e.g., in diphenylmethane diisocyanate) and the availability of the
_NCO groups for reaction with the hydrogen donors of the _OH type
residing on the organic chain of the polyols of the rapidly
reacting composition.
[0077] Suitable polyols for this rapidly reacting composition
include, without limitation, polyether polyols having average
molecular weights in a range of from about 200 to about 2000 and
containing one or more pendent hydroxyl and/or carboxyl groups in
addition to primary hydroxyl groups, which can chemically react
with unreacted functional --NCO groups of the blocked,
heat-activated aliphatic diisocyanate and the hydroxyl and/or
carboxyl pendent functional groups of the polyurethane of the outer
layer 26. An exemplary polyol is ELASTOLIT M50555R NPU U05274 from
BASF Corp. of Wyandotte, Mich.
[0078] The rapidly reacting composition can also contain
appropriate additives, including, by way of example and without
limitation, any combination of the following: heat and ultra-violet
light stabilizers, pH stabilizers, antioxidants, dulling agents,
surfactants, carbon black, chain extenders (e.g., ethylene glycol),
thixotropic agents (e.g., amorphous silica), fillers such as clay
particles, and catalysts such as tin catalysts (e.g., dibutyltin
dilaurate).
[0079] Non-Aromatic Polyurethane Elastomer Inner Layer
[0080] Exemplary polyisocyanates that can be selected for making
the inner layer 28 include polyisocyanates having closed aliphatic
ring structures with pendent --NCO groups, such as isophorone
diisocyanate, which can be obtained from Recticel under the
tradename ISOFAST. Also suitable is tetramethyl xylene
diisocyanate, which can be obtained from Texaco under the tradename
TMXDI.
[0081] Suitable polyols for this rapidly reacting composition
include, without limitation, polyether polyols having molecular
weights in a range of from about 220 to about 250 and containing
one or more pendent hydroxyl and/or carboxyl groups (in addition to
primary hydroxyl groups), which can chemically react with unreacted
functional --NH groups of the carbodiimide and the hydroxyl and/or
carboxyl pendent functional groups of the polyurethane of the outer
layer 26. An exemplary polyol is POLYFAST from Recticel.
[0082] Additives as mentioned above in connection with the aromatic
polyurethane elastomer may be used for non-aromatic polyurethane
elastomer inner layers 28 as well.
[0083] Cast PVC Inner Layer
[0084] Where PVC is selected as the base polymer, the casting
composition can include one or more plasticizers. In a preferred
embodiment, the plasticizers selected for this invention are
capable of reacting with the crosslinker (e.g., carbodiimide) in
the outer layer 26, so that the crosslinker can successfully
crosslink the polyurethane of the outer layer 26 with the
plasticizer of the casting composition. Exemplary plasticizers
include, without limitation, plasticizers having one or more
pendent hydroxyl or carboxyl functional groups. These plasticizers
are preferably incorporated around the backbone of the base polymer
as an internal lubricant.
[0085] Preferably, both a low molecular weight plasticizer and a
medium molecular weight plasticizer are included in the casting
composition having PVC as its base polymer. The low molecular
weight plasticizer is selected to provide low temperature
flexibility, so that performance of the inner layer 28 at low
temperatures, such as .sub.--30EC, is not hindered. An exemplary
low molecular weight plasticizer is di-2-ethylhexylphthalate (also
known as DUP). On the other hand, the medium molecular weight
plasticizer is selected to provide high temperature stability to
the inner layer 28. An exemplary medium molecular weight
plasticizer is trioctyltrimellitate (TOTM).
[0086] The amount of low molecular weight plasticizer should be
maintained fairly low so as to reduce volatilization and,
consequently, window fogging. For example, the weight ratio of low
molecular weight plasticizer to PVC base resin in the casting
composition can be from about 0.25:100 to about 1:100. The weight
ratio of medium molecular weight plasticizer to PVC base resin in
the casting composition can be in a range of from about 10:100 to
about 40:100, and more preferably in a range of from about 20:100
to about 40:100. If an insufficient amount of medium molecular
weight plasticizer is used, the inner layer 28 may not exhibit
adequate high temperature aging properties, resulting in, for
example, premature stiffening of the inner layer 28 after exposure
to elevated temperatures. On the other hand, if an excess amount of
medium molecular weight plasticizer is used, the article surface
may tend to gloss at elevated temperatures, creating unacceptable
surface reflectance.
[0087] Where PVC is selected as the base polymer of the casting
composition, the casting composition can be prepared by any
suitable technique, including suspension or mass polymerization
followed by drying to provide a white, free-flowing powder of PVC
having, for example, an average particle size of about 350:m. The
resulting PVC powder can then be thoroughly mixed with the
plasticizer to form the casting composition by employing any
suitable technique, such as high energy compounding. During
compounding, the plasticizer is absorbed by the PVC and thereby
causes the PVC to swell. Compounding can be performed, for example,
at a temperature in a range of from about 150EF (about 60EC) to
about 190EC (about 88EC).
[0088] The plasticizer selected should impart thermal stability to
the PVC powder and be permanent to render the article flexible for
the life of the application. Generally, PVC powder consists of
discrete particle groups that, when subjected to excessive
temperatures, decompose prior to melting. This decomposition
liberates hydrogen chloride, which autocatalytically degrades the
PVC. Since the PVC is melted during gelling and fusing steps, a
suitable internal plasticizer is mixed with and absorbed in the PVC
powder prior to casting in order to inhibit thermal degradation of
the PVC and provide the inner layer 28 with a soft, flexible,
compressing feel.
[0089] Preferably, the plasticizer is bound in the PVC matrix with
sufficient bond energy to form a permanent part of the polymer
matrix and thereby permit the finished fused article to exhibit
good flexibility and weathering at super- and sub-ambient
conditions in use.
[0090] The casting composition having PVC as its base resin can
contain appropriate additives, including, by way of example and
without limitation, any combination of the following: heat and
ultra-violet light stabilizers, such as hydroquinones; internal
lubricants, such as stearic acid; antioxidants; dulling agents;
carbon black; and fillers, such as clay and/or diatomaceous earth.
Other additives can also be introduced into the inner layer 28 to
protect against oxidation and destabilization of the cast PVC. Such
additives include barium, calcium, and zinc heat stabilizers, such
as barium nonylphenate, calcium carboxylate, and zinc stearate.
These and other additives can be included to form the dry resin
material by using, by way of example and without limitation, a high
intensity dry powder mixer such as a Henschel mixer.
[0091] In addition, the PVC composition can comprise one or more
copolymer alloys or blends of PVC and another polymer, such as one
or more polyurethanes. Such copolymer alloys and blends can be
prepared by techniques well known to those skilled in the art, such
as compounding.
[0092] Cast Thermoplastic Polyurethane Inner Layer
[0093] Where a thermoplastic polyurethane is selected as the base
polymer for the casting composition, the thermoplastic polyurethane
preferably contains at least one ethylenically unsaturated bond in
its backbone and/or hydroxyl or carboxyl groups. In a preferred
embodiment, the ethylenically unsaturated bond and/or hydroxyl
groups of the thermoplastic polyurethane is/are capable of reacting
with the crosslinker (e.g., carbodiimide) in the outer layer 26, so
that the crosslinker can successfully crosslink the polyurethane of
the outer layer 26 with the polyurethane of the casting
composition. Exemplary thermoplastic polyurethanes include, without
limitation, ESTANE (provided by B. F. Goodrich of Akron, Ohio) and
PELLETHANE (provided by Dow Chemical Company of Midland Mich.).
[0094] The thermoplastic polyurethane of the casting composition
can be prepared by, for example, a prepolymerization technique,
followed by drying, compounding, chopping, and grinding, to provide
a free-flowing powder of thermoplastic polyurethane. Excess polyols
can be provided in preparing the thermoplastic polyurethane of
casting composition. As mentioned above, the hydroxyl groups of the
excess polyols can serve to promote crosslinking and the chemical
bonding between the outer layer 26 and the inner layer 28. The
resulting thermoplastic polyurethane powder typically has a
brownish appearance, and can possess, for example, a 425 mesh size.
The powder can contain additives, as needed or required by the
intended use, to form the composition by employing any suitable
technique, such as introducing the additives during
prepolymerization. The weight ratio of the total additives to the
base resin can be, for example, in a range of from about 3:100 to
about 7:100, depending on the intended use and additives
included.
[0095] The casting composition including a thermoplastic
polyurethane as its base polymer can contain appropriate additives,
including, by way of example and without limitation, any
combination of the following: heat stabilizers; flexibilizers, such
as low molecular weight polyurethanes (incorporated into the
backbone, for example, during the compounding or like step);
antioxidants; dulling agents; carbon black; fillers, such as clay
particles; and free flowing additives. Other additives can also be
introduced into the inner layer 28 to protect against scorching.
These and other additives can be included to form the dry resin
material by using, by way of example and without limitation, a high
energy extruder/chopper.
[0096] In similar fashion, other thermoplastic powders based upon
polyolefins or elastomers may be formed. Extruded micropellets of
the PVC, TPU, TPO, TPE, or other thermoplastic formulations or
combinations thereof may be cast instead of the powder form.
[0097] Various blends of polyether polyols and polyisocyanates
having suitable resilience properties can be employed to form the
semi-rigid polyurethane cellular foam of the intermediate layer 30.
For example, the polyisocyanate blend can include methylene
diisocyanate. The semi-rigid polyurethane cellular foam also can
contain appropriate additives, including, by way of example and
without limitation, any combination of the following: surfactants,
antioxidants, fillers, stabilizers, catalysts such as tin catalysts
(e.g., dibutyl tin dilaurate) and tertiary amines (e.g.,
diethanolamine), and small amounts of foaming agents such as water.
In this regard, it is noted that the condensation reaction between
the blends of polyols and polyisocyanates releases water, which
reacts with the polyisocyanate to generate carbon dioxide and
thereby impart the cellular structure to the intermediate layer 30.
Accordingly, a slightly stoichiometric excess of polyol can be
provided to form the semi-rigid polyurethane cellular foam.
[0098] FIG. 10 illustrates the next step of this embodiment, in
which the layered composite structure 24 is demolded (i.e.,
removed) from the first mold surface 52. The demolding process is
often a relatively labor intensive, tedious, and time consuming
task. Formation of tears in or undue stretching of the layered
composite structure 24 during demolding can irreversibly ruin and
thereby necessitate disposal of the layered composite structure 24
as scrap. Such demolding problems and inefficiencies are largely
overcome by practice of this invention, since the interfacial
chemical bond between the outer layer 26 and inner layer 28
strengthens the layered composite structure 24 by discouraging
separation of the outer and inner layer 26 and 28 and elongated
structure 27 during demolding procedures. Moreover, such demolding
problems and inefficiencies are further obviated by the use of the
aromatic-based elastomer, since it has advantageous physical
properties.
[0099] To enhance the releasibility from the first mold surface 52
further, the mold surface 52 can be pretreated with a releasing
agent. Exemplary releasing agents include, by way of example, high
molecular weight microcrystalline wax mold releases, such as
Chem-Trend PRC 7140, supplied by Chem-Trend, Inc. of Howell, Mich.,
or PRC 2006, also supplied by Chem-Trend. These mold releasing
agents dry quickly on a heated mold within about 5 to about 10
seconds and form a release barrier between the grained mold surface
52 and the outer layer 26. Care should be taken to avoid the
accumulation of the mold releasing agent on the first mold surface
52 or excess solids content in the agent, since such accumulation
or excess solids content tends to fill the interstices of the
decorative, grained mold surface 52, thereby removing from the
exterior surface of the panel structure 10 the appearance of the
intricate, hair-like grained configuration of the mold surface 52.
Further, the use of excess mold releasing agents can cause the
agents to transfer from the first mold surface 52 to the layered
composite structure 24 during demolding of the composite structure
24, thus requiring additional wash-removal and drying steps after
demolding and hence a loss in productivity.
[0100] After being demolded from the first mold surface 52, the
layered composite structure 24, including the combination of the
outer and inner layers 26 and 28 and narrow elongated structure 27,
can be examined for defects with a light source (not shown) while
the layered composite structure 24 is positioned on a transparent
substrate (not shown). Such defects usually are present as cosmetic
blemishes in the outer layer 26, and may include the presence of
tears and rupturable portions lacking sufficient thickness to
withstand stresses associated with demolding or the further
processing steps, especially the uniting step. If minor and
isolated, such localized defects can be remedied by post
application of additional water-dispersed composition 54 onto the
outer layer 26. Additionally, minor tears or thin areas can be
repaired using thermoplastic, heat formable polyurethane tape on
the backside 28b of the layered composite structure 24.
Advantageously, the need to scrap the entire layered composite
structure 24 is thereby averted. As a cautionary note, however,
post application spray repair of surface 26a is generally
undesirable and its use should be minimized to correcting localized
defects, since post application spray repair can negate the grained
leather-like appearance of the outer surface 26a of the outer layer
26 which is transcribed from the first mold surface 52.
[0101] As discussed in further detail below, the steps of demolding
and examining of the layered composite structure 24 from the first
mold surface 52 are not required to be conducted immediately
subsequent to the formation of the layered composite structure 24.
For example, the layered composite structure 24 optionally can be
maintained against the first mold surface 52 until completion of
the panel structure 10.
[0102] Optionally, the layered composite structure 24 can be
retained in the first mold component 50 instead of being demolded
and transferred to a second mold component 94 for the uniting step.
Alternatively, the layered composite structure 24 can be returned
to the first mold component 50 after being examined and
treated.
[0103] After the layered composite structure 24 is demolded from
the first mold surface 52 and examined, the layered composite
structure 24 is placed on a second mold surface 96 of a second mold
part 94. As shown in FIG. 11, the second mold surface 96 is shaped
to have a complementary configuration to the outer layer 26. Then,
a reactive mixture 98 for forming a semi-rigid cellular foam, such
as a polyurethane semi-rigid cellular foam, is applied to an inner
surface 28b of the inner layer 28 while the composite structure 24
is disposed on the second mold surface 96 to form the intermediate
layer 30. The reactive mixture 98 can be applied, for instance, by
employing high pressure impingement mixing and a mix-head nozzle.
The second mold component 94 is generally heated to a temperature
in a range of from about 35EC to about 45EC, and more preferably in
a range of from about 35EC to about 40EC, during application of the
reactive mixture 98. The mixture 98, which is typically relatively
viscous, is in a transient state of reaction during application to
the second mold component 94 and begins to foam within seconds of
application.
[0104] Although the desired thickness of the intermediate layer is
partially dependent upon the intended use of the panel structure
10, generally the intermediate layer can have a thickness in a
range of from about 5 mm to about 12 mm.
[0105] Once the reactive mixture 98 has been applied to the layered
composite structure 24 located on the second mold surface 96, a
third cooperating mold part or component 100 carrying the
pre-formed rigid substrate 22 having a doors 12 is moved into
cooperating relation with the second mold component 94, as shown in
FIG. 12. The third mold component 100 has a third mold surface 102
(FIG. 11) which is complementary to the interior surface 10b of the
panel structure 10. Thereafter, the reactive mixture 98 is foamed
and cured, preferably under heat of approximately 43.3EC (10EF) and
a self-generated cavity pressure of about 0.8 atm to form the
intermediate layer 30. The semi-rigid polyurethane cellular foam
serves to unite the layered composite structure 24 with the
pre-formed rigid substrate 22 disposed on the third mold surface
102. The panel structure including the combination of the layered
composite structure 24, the rigid substrate 22, and the
intermediate layer 30 then can be removed from the mold parts 94
and 100 and additional components can be affixed.
[0106] The rigid substrate 22 may be formed from any material
possessing the requisite strength to reinforce and mount the outer
layer 26, inner layer 28, and intermediate layer 30. Suitable
materials include any material with sufficient rigidity to permit
the composite to be mounted into a vehicular sub-structure,
including, by way of example, injection molded thermoplastics, such
as, without limitation, a styrene maleic anhydride (SMA),
acrylonitrile butadiene styrene (ABS), polycarbonates (PC), an
alloy of ABS-PC, reinforced reaction injection molded polyurethanes
(RRIM), metals, metal alloys, wood-fiber composites, or any
combination thereof. Fillers can be used in the substrate 22, as is
known in the art.
[0107] The reinforcing substrate 22 may optionally also include
reinforcement nanoparticles comprising platelet minerals dispersed
in the desired polymer in desired ratios. The components can be
blended by general techniques known to those skilled in the art.
For example, the components can be blended and then melted in
mixers or extruders.
[0108] The illustrated embodiment of this invention can also be
modified by applying the reactive mixture 98 for forming the
polyurethane semi-rigid cellular foam 30 to the surface of the
rigid substrate 22 instead of the layered composite structure 24.
Alternatively, the second and third mold components 94 and 100 can
be cooperatively engaged to define a cavity between the inner
surface 28b of the inner layer 28 and the outer surface of the
substrate 22, with the reactive mixture 98 thereafter being
injected between the rigid substrate 22 and the composite structure
24.
[0109] Additional specific preferred methods, for the purposes of
this invention, for forming a polymer composite having dispersed
therein exfoliated layered particles are disclosed in U.S. Pat.
Nos. 5,717,000, 5,747,560, 5,698,624, and WO 93/11190. For
additional background the following are also references: U.S. Pat.
Nos. 4,739,007 and 5,652,284.
[0110] Where the doors separate from each other during deployment
of the air bag, the doors can be attached to the substrate with
hinge components or tether devices to ensure that the doors do not
become projectiles during actuation of the air bag assembly.
Suitable connecting means and arrangements for practice in this
invention are disclosed in U.S. Pat. Nos. 5,456,490, 5,222,760,
5,569,959, and 5,560,646. Where the doors are integrally molded,
the doors can be reinforced at the hinged or tethered areas.
[0111] The second embodiment of this invention will now be
described with reference to FIGS. 13-17. In describing the second
embodiment, identical reference numerals to those used in FIGS.
1-12 will be used to describe structures and parts having similar
properties or functions to those of the first embodiment. For the
purpose of brevity, steps and features involved in the second
embodiment that are the same as those described above in connection
with the first embodiment will not be repeated hereinbelow.
[0112] Referring now more particularly to the drawings, and in
particular FIGS. 13 and 14, in accordance with this second
embodiment, the layered composite structure 24 comprises the outer
layer 26 and the inner layer 28, and a seam defining structure,
namely a thin sheet structure 29 interposed therebetween (or
partially or fully embedded within the inner layer 28). The thin
sheet structure 29 overlays a portion of the outer layer 26
corresponding to the portion of the layered composite structure 24
through which the doors 12 move during the operation of the
secondary restraint system 40. The thin sheet structure 29 is
severed in a position and configuration to define an exteriorly
invisible tear seam generally conforming to a portion of the
outline of the movable doors 12.
[0113] During deployment of the air bag 42, the expanding air bag
42 impacts against the backside of the panel structure 10 and
fractures the composite structure 24 along the severed portion of
the thin sheet structure 29 to create a passageway. The formed
passageway permits expansion of the air bag 42 into the passengers'
compartment of the vehicle and protects the occupants from violent
collision against the panel structure 10 or windshield 16.
[0114] Referring to FIGS. 15 and 16, there are shown two
constructions of the thin sheet structure 29 with an H-shaped
pattern 31 severed therein. The pattern should correspond to the
movable portion of the doors 12. The thin sheet structure 29 is
severed in a position and configuration to define an exteriorly
invisible tear seam generally conforming to an outline of the
movable doors 12. As referred to herein, severing includes the
formation of continuous or non-continuous cuts or perforations or
channels (having a width), and cuts or perforations or channels
that pierce all or only a portion of the thickness of the thin
sheet structure 29.
[0115] As shown in FIG. 15, the sheet structure 29 is constructed
as a continuous sheet, which may be made of a thermoplastic
material. Among the materials suitable for preparing the continuous
sheet structure 29 are MYLAR polyester, polyurethane, or polyamide
(Nylon) film with adhesive backing to self-adhere to the outer
layer 26 while the polyurethane elastomer inner layer 28 is
applied. The size of the sheet 29 may be, for example, on the order
of 30 mm by 38 mm, with a thickness on the order of from about 0.1
mm to about 0.2 mm. The pattern of the severed film depends on the
configuration of the outline of the doors 12.
[0116] As shown in FIG. 16, alternatively the sheet structure 29
may be formed from a mesh with a severed portion, designated by
reference numeral 31. The mesh (or a porous layer) is advantageous
inasmuch as it contains voids through which the outer and inner
layer 26 and 28 may contact and undergo interfacial chemical
bonding. It has even been observed that during deposition of the
inner layer 28, the mesh sheet structure 29 may be lifted from the
surface 26b of the outer layer 26 and encapsulated in the inner
layer 28. The mesh may be made of spunbonded polyester (available
from Reemay located in Old Hickory, Tenn.) or fiberglass mesh or
polyester non-woven cloth, to name a few examples. The mesh should
have a heat-activated adhesive coupling agent compatible to bond
with the inner layer 28 and so as to maintain the mesh in place
during the application of the inner layer 28. The mesh sheet 29 may
have dimensions on the order of from about 30 mm to about 38 mm
with a thickness in a range of from about 0.1 mm to about 0.2
mm.
[0117] The thin sheet structure 29 applied to the inner surface 26b
of the outer layer 26 and replaces the elongated structure 27 and
the process steps associated therewith. Otherwise, the process
steps are identical with the first embodiment.
[0118] The thin sheet structure 29 is substantially larger than the
area of the opening through which the doors 12 egress, but may have
a lesser width and height than the inner and outer layers 26 and
28. As with the first embodiment, the inner layer 28 may be formed
from a variety of different base polymers and additives; however,
the use of a polyurethane elastomer, especially an aromatic
polyurethane elastomer, is preferred.
[0119] In another alternative method as illustrated in FIG. 18, the
sheet structure 29 is provided with peripheral walls that extend
perpendicular from the plane of the sheet structure 29 so as to
define an open ended box. The peripheral walls face away from the
first mold surface 52 and protrude from the inner surface 28b of
the inner layer 28. The protruding portions of the peripheral walls
are attached to substrate 22. The attachment of the sheet structure
29 to the substrate 22 localizes elongation of the outer and inner
layers 26 and 28 (caused during movement of the doors 12 through
the layered composite structure 24) to those portions of the layers
26 and 28 located within the area defined by the peripheral walls
of the sheet structure 29. As a consequence, the portions of the
layered composite structure 24 located outside of the area defined
by the peripheral walls of the sheet structure 29 are not subjected
to excess elongation and are less likely to separate from the rigid
substrate 22 and the optional cellular foam 30. This embodiment is
especially useful for panel designs that do not provide sufficient
area of support for the layered composite structure 24, permitting
the sheet structure 29 to be self-restraining (relative to the
layered composite structure 24) during airbag deployment.
[0120] Although the method of this invention has been embodied
above in connection with the preparation of a instrument panel, it
is understood that the method is equally applicable to other panel
structures, including for example door panels, interior rear
quarter panels, pillar covers and headliners.
[0121] The foregoing detailed description of the preferred
embodiments of the invention has been provided for the purpose of
explaining the principles of the invention and its practical
application, thereby enabling others skilled in the art to
understand the invention for various embodiments and with various
modifications as are suited to the particular use contemplated. The
foregoing detailed description is not intended to be exhaustive or
to limit the invention to the precise embodiments disclosed.
Modifications and equivalents will be apparent to practitioners
skilled in this art and are encompassed within the scope of the
appended claims.
* * * * *