U.S. patent application number 12/101355 was filed with the patent office on 2008-08-07 for in-mold decorated articles and methods.
This patent application is currently assigned to Trexel, Inc.. Invention is credited to Levi A. Kishbaugh, Kevin J. Levesque, David E. Pierick, Joseph P. Vadala.
Application Number | 20080187741 12/101355 |
Document ID | / |
Family ID | 24713775 |
Filed Date | 2008-08-07 |
United States Patent
Application |
20080187741 |
Kind Code |
A1 |
Vadala; Joseph P. ; et
al. |
August 7, 2008 |
IN-MOLD DECORATED ARTICLES AND METHODS
Abstract
The invention provides in-mold decorated articles and methods to
form the articles. The in-mold decorated articles include a
polymeric portion having a substrate material adhered to a surface
of the polymeric portion. The substrate material may be, for
example, a film or a fabric. In some embodiments, the polymeric
portion may be a foam and, particularly, a microcellular polymeric
material. The articles are formed by injecting a mixture of blowing
agent and polymeric material into a mold cavity in which the
substrate material is disposed, so that the substrate material is
forced against a wall of the mold cavity. The blowing agent, which
in certain preferred cases is a supercritical fluid, decreases the
viscosity of the polymeric material and, therefore, enables
reductions in injection pressures and temperatures. Reduced
injection temperature and pressure may widen the processing window,
increase flexibility in the selection of substrate materials, and
can eliminate the need for a barrier layer that is sometimes used
in conventional processes. The method may be used to produce a
variety of in-mold decorated articles.
Inventors: |
Vadala; Joseph P.;
(Leominster, MA) ; Kishbaugh; Levi A.; (Groveland,
MA) ; Levesque; Kevin J.; (Andover, MA) ;
Pierick; David E.; (San Diego, CA) |
Correspondence
Address: |
WOLF GREENFIELD & SACKS, P.C.
600 ATLANTIC AVENUE
BOSTON
MA
02210-2206
US
|
Assignee: |
Trexel, Inc.
Woburn
MA
|
Family ID: |
24713775 |
Appl. No.: |
12/101355 |
Filed: |
April 11, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10849277 |
May 18, 2004 |
7364677 |
|
|
12101355 |
|
|
|
|
09676251 |
Sep 29, 2000 |
|
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|
10849277 |
|
|
|
|
Current U.S.
Class: |
428/315.5 ;
264/241; 521/50 |
Current CPC
Class: |
B32B 3/26 20130101; B32B
5/18 20130101; B29C 44/12 20130101; Y10T 428/249978 20150401; B29C
44/348 20130101; B29C 44/14 20130101 |
Class at
Publication: |
428/315.5 ;
264/241; 521/50 |
International
Class: |
B32B 3/26 20060101
B32B003/26; B29C 45/14 20060101 B29C045/14; C08J 9/00 20060101
C08J009/00 |
Claims
1. An in-mold decorated article comprising: an injection-molded
microcellular polymeric material; and a substrate adhered to a
surface of the microcellular polymeric material.
2. The article of claim 1, wherein the substrate has a single
layer.
3. The article of claim 1, wherein the substrate comprises a fabric
material.
4. The article of claim 1, wherein the substrate comprises a
plastic film.
5. The article of claim 1, wherein the microcellular polymeric
material is essentially free of any residual chemical blowing agent
or reaction by-product of chemical blowing agent.
6. The article of claim 1, wherein the microcellular polymeric
material article has a void fraction of between about 0.05 and
about 0.30.
7. The article of claim 1, wherein the substrate covers an entire
first side of the microcellular polymeric material.
8. The article of claim 1, wherein the microcellular polymeric
material has an average cell size of less than 100 microns.
9. An in-mold decorated article comprising: an injection-molded
polymeric material; and a single-layer fabric substrate adhered to
a surface of the polymeric material.
10. The article of claim 9, wherein the polymeric material
comprises a polymeric foam.
11. A method for forming an in-mold decorated article comprising:
providing a substrate within a mold cavity; and injecting a mixture
of a thermoplastic polymeric material and blowing agent into the
mold cavity to form an in-mold decorated article in the mold
cavity, the article including a microcellular thermoplastic
polymeric material portion adhered to the substrate.
12. The method of claim 11, wherein the blowing agent comprises
carbon dioxide.
13. The method of claim 11, wherein the blowing agent comprises
nitrogen.
14. The method of claim 11, comprising injecting a single-phase
solution of polymeric material and blowing agent into the mold
cavity.
15. The method of claim 11, wherein the substrate material has a
single layer.
16. The method of claim 11, wherein the substrate comprises a
fabric material.
17. The method of claim 11, wherein the substrate comprises a
plastic film.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 10/849,277, filed May 18, 2004, entitled
"In-Mold Decorated Articles and Methods", which is a divisional of
U.S. patent application Ser. No. 09/676,251 (now abandoned), filed
Sep. 29, 2000, entitled "In-Mold Decorated Articles and Methods".
Each of these applications is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates generally to injection molding
of polymeric materials and, more particularly, to in-mold decorated
articles and methods for producing the articles.
BACKGROUND OF THE INVENTION
[0003] Polymeric materials may be processed to form articles having
a number of different shapes and sizes. Conventional polymer
processing techniques include injection molding, extrusion, and
blow molding. Injection molding generally involves injecting molten
plastic into a mold cavity, cooling the molten plastic, and opening
the mold to produce an injected molded article having a shape
similar to the mold cavity.
[0004] In some cases, it may be desirable to adhere a substrate
material to an exterior surface of a polymeric article. Such
substrates may be used to enhance the appearance of the article
and/or to improve properties (e.g., stiffness) of the article.
Exemplary substrate materials include films and fabrics.
[0005] In-mold decorating techniques produce molded articles which
include a substrate adhered to a surface of the article. These
techniques typically involve placing a substrate within the mold
cavity so that molten polymer injected into the mold forces the
substrate material against a mold wall. When the polymer cools, it
adheres to the substrate material. The mold may be opened to
produce a molded article having a substrate on its exterior
surface.
[0006] Conventional in-mold decorating techniques typically involve
injecting molten polymer at high temperatures and pressures into
the mold to ensure adequate filling and/or sufficient adherence of
the substrate to the plastic molded article. However, these
conditions may damage certain types of substrates. For example,
film substrates may shrink or crack as a result of high
temperatures. Furthermore, when fabric substrates are used, a
barrier layer may be required to prevent polymer from bleeding
through the fabric as a result of high injection pressures. The
barrier layer may add to the cost of producing the injection molded
article and may reduce the adherence of the fabric to the polymeric
material.
[0007] Accordingly, there is a need for improved in-mold decorated
articles and a method to produce the articles.
SUMMARY OF THE INVENTION
[0008] The invention provides in-mold decorated articles and
methods to form the articles. The in-mold decorated articles
include a polymeric portion having a substrate material adhered to
a surface of the polymeric portion. The substrate material may be,
for example, a film or a fabric. In some embodiments, the polymeric
portion may be a foam and, particularly, a microcellular polymeric
material. The articles are formed by injecting a mixture of blowing
agent and polymeric material into a mold cavity in which the
substrate material is disposed, so that the substrate material is
forced against a wall of the mold cavity. The blowing agent, which
in certain preferred cases is a supercritical fluid, decreases the
viscosity of the polymeric material and, therefore, enables
reductions in injection pressures and temperatures. Reduced
injection temperature and pressure may widen the processing window,
increase flexibility in the selection of substrate materials, and
can eliminate the need for a barrier layer that is sometimes used
in conventional processes. The method may be used to produce a
variety of in-mold decorated articles.
[0009] In one aspect, the invention provides an in-molded decorated
article. The article includes an injection-molded microcellular
polymeric material having an average cell size of less than 100
microns, and a substrate adhered to a surface of the microcellular
polymeric material.
[0010] In another aspect, the invention provides an in-mold
decorated article. The article includes an injection-molded
polymeric foam material wherein at least 70% of the total number of
cells have a cell size of less than 150 microns, and a substrate
adhered to a surface of the polymeric foam material.
[0011] In another aspect, the invention provides an in-mold
decorated article. The article includes an injection-molded
polymeric material and a single-layer fabric substrate adhered to a
surface of the polymeric material.
[0012] In another aspect, the invention provides an in-mold
decorated article. The article includes an injection-molded
polymeric material having a softening temperature, and a substrate
adhered to a surface of the injection molded polymeric material.
The substrate includes a polymer having a softening temperature
within 20.degree. C. of the softening temperature of the injection
molded polymeric material.
[0013] In another aspect, the invention provides a method for
forming an in-mold decorated article. The method includes molding a
fluid polymeric material against a substrate, and allowing the
fluid polymeric material to harden and adhere to the substrate as a
microcellular polymeric material having an average cell size of
less than 100 microns.
[0014] In another aspect, the invention provides a method for
forming an in-mold decorated article. The method includes
positioning a substrate material within a mold cavity and
introducing a physical blowing agent into polymeric material in a
polymer processing apparatus. The method further includes mixing
the blowing agent and the polymeric material under conditions at
which the blowing agent is a supercritical fluid, and injecting a
mixture of polymeric material and blowing agent into the mold
cavity.
[0015] In another aspect, the invention provides a method for
forming an in-mold decorated article. The method includes providing
a polymer molding system including an extruder, a mold, and a
substrate disposed within a cavity of the mold. The system is
constructed and arranged to deliver blowing-agent-free molten
polymeric material from the extruder into the mold cavity at a
minimum injection pressure and to solidify the polymeric material
in the mold to form an in-mold decorated article having the
substrate adhered to a surface of a polymeric material portion. The
method further includes delivering polymeric material admixed with
a blowing agent from the extruder into the mold cavity, at an
injection pressure of less than 95% of the minimum injection
pressure, and solidifying the polymeric material in the mold to
form an in-mold decorated article having the substrate adhered to a
surface of a polymeric material portion.
[0016] Other advantages, aspects, and features of the invention
will become apparent from the following detailed description of the
invention when considered in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1A schematically illustrates an injection molding
system at the beginning of a molding cycle used to produce in-mold
decorated articles according to a method of the present
invention.
[0018] FIG. 1B schematically illustrates the injection molding
system of FIG. 1A after a charge of polymeric material and blowing
agent has been accumulated.
[0019] FIG. 1C schematically illustrates the injection molding
system of FIG. 1A after the charge of polymeric material and
blowing agent has been injected into the mold to form the in-mold
decorated article.
[0020] FIGS. 2A and 2B schematically illustrate an injection mold
and an assembly for providing a continuous sheet of substrate
material to the mold when the mold is open and when the mold is
closed, respectively.
[0021] FIG. 3 schematically illustrates an in-mold decorated
article according to one embodiment of the present invention.
[0022] FIG. 4 is an SEM photo of the microstructure of the
polymeric material portion of the in-mold decorated article
produced in Example 1.
DETAILED DESCRIPTION
[0023] The invention provides an in-molded decorated article and a
method for producing the article. The method includes introducing a
blowing agent into polymeric material in a polymer processing
apparatus to form a mixture of blowing agent and polymeric material
having a reduced viscosity relative to the polymeric material. The
mixture is injected into a mold cavity in which a substrate
material is positioned. The substrate is forced against the mold
wall and the mixture is cooled to form an in-mold decorated article
having a substrate covering a polymeric portion of the article. As
described further below, the polymeric portion of the article may
be a polymeric foam and, in particular, a microcellular polymeric
material.
[0024] Referring to FIGS. 1A-1C, an injection molding system 10 is
used to produce an in-mold decorated article according to one
method of the present invention. An extruder 12 of molding system
10 includes a polymer processing screw 14 that is rotatable within
a barrel 16 to convey polymeric material in a downstream direction
18 within a polymer processing space 20 defined between the screw
and the barrel. A source 22 of blowing agent is connected to a
blowing agent port 24 formed within the barrel to introduce blowing
agent into the polymeric material, as described further below.
Extruder 12 includes an outlet 26 of the extruder, for example a
gate, connected to an injection mold 28 in which a substrate
material 30 is positioned.
[0025] Generally, injection molding system 10 operates cyclically
to produce a series of in-mold decorated articles. At the beginning
of a typical molding cycle, screw 14 is positioned at a downstream
end 32 of barrel 16 as illustrated in FIG. 1A. Polymeric material,
typically in pelletized form, is fed into polymer processing space
20 from a hopper 34 through an orifice 36. Barrel 16 may be heated
by one or more heating units 37. Screw 14 rotates to plasticate
polymeric material and to convey the polymeric material in
downstream direction 18. Blowing agent is introduced into the
polymeric material from source 22 through blowing agent port 24 to
form a mixture of blowing agent and polymeric material in
processing space 20. The mixture is conveyed downstream by the
rotating screw and accumulated in a region 38 within the barrel
downstream of the screw. The accumulation of the mixture in region
38 creates a pressure that forces the screw axially in an upstream
direction in the barrel. After a sufficient charge of the mixture
has been accumulated, screw 14 ceases to rotate and stops moving in
the upstream direction (FIG. 1B). Preferably, when the screw no
longer plasticates polymeric material the flow of blowing agent
into the polymeric material may be stopped, for example, by the
operation of a shut-off valve 40 associated with the blowing agent
port. Then, the screw is moved axially in a downstream direction to
downstream end 32 of the barrel (FIG. 1C) to inject the accumulated
charge of the mixture through outlet 26 of the extruder and into a
cavity 33 of mold 28. A valve 42 associated with the outlet of the
extruder typically is opened to permit the mixture to flow into the
mold. The injected mixture forces substrate 30 against a mold wall
44. The mixture of polymeric material and blowing agent is cooled
in the mold, after which the mold is opened to produce an in-mold
decorated article 60 (FIG. 3) having a substrate formed integral
with the molded polymeric portion.
[0026] In some embodiments, it may be preferable to form a
single-phase solution of polymeric material and blowing agent
within polymer processing space 20 and to maintain the single-phase
condition until the solution is injected into mold 28, particularly
when the polymeric portion of the in-mold decorated article is a
microcellular material.
[0027] To aid in the formation of the single-phase solution,
blowing agent introduction may be done through a plurality of
blowing agent ports 24 arranged in the barrel, though it should be
understood that a single port may also be utilized to form a
single-phase solution. When multiple ports 24 are utilized, the
ports can be arranged radially about the barrel or in a linear
fashion along the axial length of the barrel. An arrangement of
ports along the length of the barrel can facilitate injection of
blowing agent at a relatively constant location relative to the
screw when the screw moves axially (in an upstream direction)
within the barrel as the mixture of polymeric material and blowing
agent is accumulated. Where radially-arranged ports are used, ports
24 may be placed at the 12:00 o'clock, 3:00 o'clock, 6:00 o'clock
and 9:00 o'clock positions about the extruder barrel, or in any
other configuration as desired. Blowing agent port 24 may include a
single orifice or a plurality of orifices. In the multi-orifice
embodiments (not illustrated), the port may include at least about
2, and some cases at least about 4, and others at least about 10,
and others at least about 40, and others at least about 100, and
others at least about 300, and others at least about 500, and in
still others at least about 700 blowing agent orifices. In another
embodiment, port 24 includes an orifice containing a porous
material that permits blowing agent to flow therethrough and into
the barrel, without the need to machine a plurality of individual
orifices.
[0028] To further promote the formation of a single-phase solution,
blowing agent port 24 may be located at a blowing agent injection
section 46 of the screw. The blowing agent injection section of the
screw may include full, unbroken flight paths. In this manner, each
flight, passes or "wipes" the blowing agent port including orifices
periodically, when the screw is rotating. This wiping increases
rapid mixing of blowing agent and polymeric material in the
extruder and the result is a distribution of relatively finely
divided, isolated regions of blowing agent in the polymeric
material immediately upon injection into the barrel and prior to
any mixing. This promotes formation of a uniform polymer and
blowing agent mixture which may be desired in certain types of
polymeric processing including microcellular processing. Downstream
of the blowing agent injection section, the screw may include a
mixing section 48 which has highly broken flights to further mix
the polymer and blowing agent mixture to promote formation of a
single-phase solution.
[0029] In some embodiments in which a single-phase solution of
polymeric material and blowing agent is formed, it may be
preferable to nucleate the solution when injecting into mold 28.
Nucleation is achieved via a pressure drop, for example, that
occurs when the solution passes through outlet 26 (e.g., a gate)
which functions as a nucleating pathway. The nucleated sites in the
solution grow into cells within the mold to form a polymeric foam
material. In some cases, the cell nucleation rate and growth may be
controlled to form a microcellular polymeric material as described
in International Publication No. WO 98/31521 (Pierick et. al.)
which is incorporated herein by reference. Particularly, nucleating
pathways (e.g. gates) that provide a high pressure drop rate, for
example greater than 0.1 GPa/s, may be utilized to form
microcellular materials in certain cases.
[0030] It should be understood that injection molding system 10 may
be any suitable type known in the art. Examples of suitable
injection molding systems, particularly when microcellular
polymeric material are being produced, have been described, for
example, in International Publication No. WO 98/31521 (Pierick et.
al.) referenced above. Similarly, the in-mold decorating method of
the present invention and the injection molding system 10 may have
any number of variations known to one of ordinary skill in the art.
For example, the methods and systems may utilize a separate
accumulator external of the barrel to accumulate the mixture of
polymeric material and blowing agent prior to injection into the
mold. The methods and systems may also use a tandem extruder having
a primary and secondary extruder.
[0031] Referring to FIGS. 2A-2B, substrate material 30 is provided
as a continuous sheet according to one embodiment of the present
invention. At the beginning of a mold cycle, a first mold half 50
is separated from a second mold half 52 to provide a space 54
therebetween (FIG. 2A). A continuous sheet of substrate material 30
extends from a delivery roll 56 to a take-up roll 58 through space
54. Mold halves 50, 52 are closed on peripheral portions of the
continuous sheet so that substrate 30 is held across mold cavity 33
(FIG. 2B). As described above, a mixture of polymeric material and
blowing agent is injected into mold cavity 33 and sufficiently
cooled, after which mold halves 50, 52 separate so that the article
may be removed from the mold. Rolls 56, 58 operate to provide a new
portion of continuous sheet between the mold halves, and the
process is repeated to produce additional in-mold decorated
articles.
[0032] It should be understood that substrate 30 may be provided
according to any other technique known to one of ordinary skill in
the art. For example, individual sheets of substrate material may
be positioned within mold cavity 33 after each respective molding
cycle. Also, substrate 30 may only extend across a portion of mold
cavity 33 to provide in-mold decorated articles with substrate
material covering selective regions of the article surface.
[0033] The introduction of a physical blowing agent into the
polymeric material in the method of the present invention reduces
the viscosity of the polymeric material. The reduction in viscosity
improves the flow of the mixture into the mold which can allow a
decorated article to be molded at relatively low injection
temperatures and pressures. As used herein, "injection pressure" is
defined as the pressure of the polymeric material entering the mold
cavity. The injection pressure is also related to the "hydraulic
pressure" which, as used herein, is defined as the pressure of
fluid (e.g., oil) used to provide the force that pushes the screw
forward during the injection period of a molding cycle. Thus, the
method of the invention also provides a reduction in hydraulic
pressure. As used herein, "injection temperature" is defined as the
melt temperature of the polymeric material entering the mold
cavity. Conventional in-mold decorating processes generally require
relatively high injection pressures (and hydraulic pressures) and
temperatures to adequately fill the mold and, in some cases, to
sufficiently impregnate the substrate to provide adequate adherence
between the polymeric material and the substrate (e.g., between
polymeric material and a fabric substrate). However, high injection
pressures and injection temperatures may damage the substrate and
can thus limit the types of substrates which are suitable. By
lowering the injection temperature and pressure required, the
present method advantageously expands the type of substrates that
can be used as described further below.
[0034] In some cases, the injection pressure in the present method
may be reduced by at least 100 psi as compared to the injection
pressure required for a polymeric material with no physical blowing
agent under otherwise similar processing conditions. In some cases,
the injection pressure is reduced by at least 200 psi, in other
cases by at least 500 psi, and in still other cases by at least
1000 psi, as compared to polymeric material with no physical
blowing agent under similar processing conditions. In some cases,
the injection pressure in the present method may be less than about
95% of the injection pressure, in other cases less than about 80%
and in other cases less than about 70%, of the injection pressure
required using a polymeric material with no physical blowing agent
under otherwise similar processing conditions. Similarly, the
injection temperature may be reduced relative to the injection
temperature required for a polymeric material with no physical
blowing agent under otherwise similar processing conditions. In
some cases, the injection temperature is reduced by at least
10.degree. C., in other cases by at least 30.degree. C., and in
other cases by at least 50.degree. C. as compared to polymeric
material with no physical blowing agent under similar processing
conditions.
[0035] The physical blowing agent utilized in the methods of the
present invention may have any suitable composition known in the
art including nitrogen, carbon dioxide, hydrocarbons,
chlorofluorocarbons, noble gases and the like, or mixtures thereof.
The blowing agent may be introduced into the polymeric material in
any flowable state, for example, a gas, liquid, or supercritical
fluid. Preferably, once introduced into the polymeric material in
the extruder, the blowing agent is in a supercritical state. That
is, the blowing agent is a supercritical fluid under the
temperature and pressure conditions within the extruder.
Supercritical blowing agents are particularly effective at lowering
the viscosity to a desired level for the methods of the present
invention. According to one preferred embodiment, the blowing agent
is carbon dioxide. In another preferred embodiment the blowing
agent is nitrogen. In certain embodiments, the blowing agent is
solely carbon dioxide or nitrogen. In preferred methods, carbon
dioxide and nitrogen blowing agents are in the supercritical state
within the extruder.
[0036] Blowing agent may be introduced into the polymeric material
to provide a mixture having the desired weight percentage for a
particular process. The weight percentage of blowing agent may
depend upon a number of variables including the selected viscosity
reduction and the desired void fraction of the polymeric material
in the in-mold decorated article. Generally, increasing the weight
percentage of blowing agent in a mixture will further decrease the
viscosity. The blowing agent percentage is typically less than
about 15% by weight of the mixture of polymeric material and
blowing agent. In some embodiments, the blowing agent level is less
than about 8% and in some embodiments less than about 5%. In some
cases, it may be preferable to use low weight percentages of
blowing agent. For example, the blowing agent level may be less
than about 3%, in others less than about 1% and still others less
than about 0.1% by weight of polymeric material and blowing agent
mixture. The blowing agent weight percentage may also depend upon
the type of blowing agent used. For example, to achieve the same
reduction in viscosity, carbon dioxide typically has to be added at
greater amounts than nitrogen.
[0037] The blowing agent introduction rate may be coupled to the
flow rate of polymeric material to produce a mixture having the
desired weight percentage of blowing agent. Blowing agent may be
introduced into the polymeric material over a wide range of flow
rates. In some embodiments, the blowing agent mass flow rate into
the polymeric material may be between about 0.001 lbs/hr and about
100 lbs/hr, in some cases between about 0.002 lbs/hr and about 60
lbs/hr, and in some cases between about 0.02 lbs/hr and about 10
lbs/hr.
[0038] Referring to FIG. 3, an in-mold decorated article 60
produced according to a method of the present invention is
schematically illustrated. Article 60 includes a polymeric material
portion 62 and a substrate portion 64 adhered to a surface 66 of
the polymeric material portion. As described above, substrate 64 is
molded integral with the polymeric material portion and, thus, no
external adhesive is required to adhere the portions together.
In-mold decorated article 60 may be used in any number of
applications including automotive, furniture, packaging, cosmetic,
business equipment, and communication applications.
[0039] Polymeric material portion 62 generally may comprise any
type of polymeric material used in the art. Suitable materials
include thermoplastic polymers which may be amorphous,
semicrystalline, or crystalline materials. Typical examples of
polymeric materials used to form portion 62 include styrenic
polymers (e.g., polystyrene, ABS), polyolefins (e.g., polyethylene
and polypropylene), fluoropolymers, polyamides, polyimides,
polyesters, and the like. Substrate 64 generally may be any type of
substrate used in the art to form in-mold decorated articles.
Examples of substrates materials include fabrics, carpets, sheets,
films such as plastic or metal films, and the like.
[0040] Because the method of the present invention permits lower
injection pressures and temperatures, a wider range of plastic
material and substrate combinations may be utilized than with
certain conventional in-mold decorating techniques. For example
using certain conventional techniques, the high temperatures and
pressures required to process certain polymeric materials cause
damage to certain substrate materials (e.g., distortion or
rupture). Relatively lower temperatures and pressures used in the
methods of the present invention permit greater options for
substrate materials selection. Polymeric substrate materials having
a softening temperature similar to the softening temperature of the
polymeric material portion may be utilized. For example, the
softening temperature of the substrate may be within than
20.degree. C. of the softening temperature of the polymeric
material, in some cases within than 10.degree. C. of the softening
temperature of the polymeric material, and in some cases
substantially equal to the softening temperature of the polymeric
material. As used herein, "softening temperature" is defined as the
melting temperature (T.sub.m) for crystalline polymers and as the
glass transition temperature (T.sub.g) for amorphous plastics. In
some embodiments, in-mold decorated article 60 may include a
substrate material 64 and a polymeric portion 62 each of which
comprise the same polymeric component. For example, the substrate
material and the polymeric material may each be made of
polypropylene. Also, the substrate material may be made of
acrylonitrile-butadiene-styrene (ABS) and the polymeric material
may be made of polystyrene.
[0041] Polymeric material portion 62 is generally a foam material
which includes a plurality of cells formed within a polymer matrix.
In these cases, the blowing agent causes the nucleation and growth
of the cells. However, in other cases, plastic material portion 62
may be a solid plastic without any cells. In these cases, the
blowing agent functions only as a viscosity lowering aid and does
not nucleate and grow cells.
[0042] In embodiments in which the polymeric material portion is a
foam material, the foam may have a wide range of void fractions.
Polymeric foams may be used that have a void fraction of between
about 1% and about 99%. In some embodiments, higher density foams
are used having a void fraction of less than 50%, in other cases a
void fraction of less than 30%, and in some cases a void fraction
of between about 5% and about 30%. The particular void fraction
will depend upon the application.
[0043] In certain embodiments, the plastic material portion may be
a microcellular material. Microcellular foams, or microcellular
materials, have small cell sizes and high cell densities. As used
herein, the term "cell density" is defined as the number of cells
per cubic centimeter of original, unexpanded polymeric material. In
some embodiments, the microcellular materials have an average cell
size of less than 100 microns; in other embodiments, an average
cell size of less than 75 microns; in other embodiments, an average
cell size of less than 50 microns; in other embodiments, an average
cell size of less than 25 microns; and, in still other embodiments,
an average cell size of less than 10 microns. In some of these
microcellular embodiments, the cell size may be uniform, though a
minority amount of cells may have a considerably larger or smaller
cells size. In some cases, the microcellular materials have a cell
density of greater than 106 cells/cm.sup.3, in others greater than
10.sup.7 cells/cm.sup.3, in others greater than 10.sup.8
cells/cm.sup.3, and in others greater than 10.sup.9
cells/cm.sup.3.
[0044] In another set of embodiments, in-mold decorated article 60
includes a polymeric foam portion 62, wherein at least 70% of the
total number of cells in the polymeric portion have a cell size of
less than 150 microns. In some embodiments at least 80%, in other
cases at least 90%, in other cases at least 95%, and in other cases
at least 99% of the total number of cells have a cell size of less
than 150 microns. In other embodiments, the foam portion may be
provided in which at least 30% of the total number of cells have a
cell size of less than 800 microns, more preferably less than 500
microns, and more preferably less than 200 microns.
[0045] In certain cases, polymeric material portion 62 may be a
foam having a non-uniform cell size. In some of these cases,
different regions of portion 62 may have cells of different size.
For example, edge regions of portion 62 may generally have a
smaller cell size than interior regions of portion 62.
[0046] Polymeric material portion 62, as described above, is
processed using a physical blowing agent and, thus, is generally
free of residual chemical blowing agents or reaction byproducts of
chemical blowing agents. Optionally, the polymeric material may
include a nucleating agent, such as talc or calcium carbonate. In
other embodiments, polymeric material portion 62 may be free of a
nucleating agent. Polymeric material portion 62 may also include
any number of other additives known in the art such as lubricants,
plasticizers, colorants, fillers and the like.
[0047] Polymeric material portion 62 may be formed over a wide
variety of thicknesses depending upon the particular application.
In some cases, the thickness may be less than 0.5 inches. In other
cases, relatively thin polymeric material portions are produced,
for example, having a thickness of less than 0.2 inches and, in
other cases, less than 0.1 inches. The reduction of viscosity of
polymeric material via the addition of the blowing agent permits
formation of thin polymeric material portion and polymeric portions
having large length-to-thickness ratios (1/t). As used herein, "1/t
ratio" is defined as the ratio of the length of extension of a
section of polymeric portion extending away from an injection
location (gate) in the mold and the average thickness across that
length. In some cases, polymeric material portion has an 1/t ratio
of greater than 50:1, in other cases greater than 100:1, and in
still other cases greater than 200:1.
[0048] Substrate portion 64 may be any of the type used in the art
and is selected for the particular application of the in-mold
decorated article. Substrate portion 64 may include decorative
features such as a design, print, or other indicia. In some cases,
the decorative features are formed using ink which is applied to
the substrate surface. In other cases, the decorative features are
created during the molding process. Substrate portion 64 may be
colored, clear, shiny, and the like. When the substrate is a
fabric, it may have any fabric pattern known in the art.
[0049] When desired, substrate portion 64 may include only a single
layer even when the substrate is a fabric material. In these
embodiments, no additional layer (e.g., a separate barrier layer or
a backing layer) separates the fabric substrate portion 64 from
polymeric material portion 62. Conventional techniques generally
employ a barrier layer, such as a finely knit textile or plastic
layer, which prevents polymer from bleeding through under typical
injection conditions. Because low pressures may be utilized in the
present method, as described above, such barrier layers are not
required. Substrate portion 64 may also be thin, even when fabric
substrates are utilized. For example, substrate portion 64 may have
a thickness of less than 0.01 inches.
[0050] The function and advantages of these and other embodiments
of the present invention will be more fully understood from the
examples below. The following examples are intended to illustrate
the benefits of the present invention but do not exemplify the full
scope of the invention.
EXAMPLE 1
Production of In-Mold Decorated Article Including Polymeric Portion
and Fabric
Substrate
[0051] An injection molding machine (Engel-500 ton) was modified to
have a configuration similar to the system illustrated in FIGS.
1A-1C. A two cavity pillar mold was used. The mold contained 3
gates per cavity and a hot runner system with 9 control zones.
[0052] A fabric including a suede layer with a non-woven cotton
backing was placed within each mold cavity. The suede layer had a
thickness of about 0.850 inches and the backing had a thickness of
about 0.160 inches to give a total fabric thickness of about 0.245
inches. Polymeric pellets having a PC/ABS composition (GE Plastics
Cycloloy MC 2231) were fed into the molding machine using the
hopper. Trials were run using a variety of different blowing agent
conditions, gate configurations, injection speeds, barrel
temperatures, and hydraulic pressures. The conditions were
summarized in Table 1.
TABLE-US-00001 TABLE 1 Processing conditions Injection Barrel
Blowing Agent Speed Temperature Hydraulic (Type - Wt. %) # of Gates
(inch/sec) (.degree. C.) Pressure (psi) Solid - 0% 3 2 271 2320
Solid - 0% 3 0.5 271 2194 N.sub.2 - 0.5% 3 0.8 249 2291 CO.sub.2 -
2% 3 0.7 249 1745 CO.sub.2 - 3.4% 3 0.7 249 1697 CO.sub.2 - 3.7% 3
1.0 249 1455 CO.sub.2 - 3.1% 1 1.8 249 2205
[0053] In-mold decorated automotive pillars having a polymeric
ABS/PC portion adhered to the fabric substrate were produced. The
pillars had a curved cross-section, a length of about 24 inches,
and a thickness of about 0.10 inches. The in-mold decorated
articles produced using blowing agent (CO.sub.2 and N.sub.2) had a
void fraction of between about 0.05 and 0.14.
[0054] The use of blowing agent reduced the hydraulic pressures and
barrel temperatures which were used to produce the in-mold
decorated articles. The reduction in hydraulic pressure was
indicative of a reduction in injection pressure and the reduction
in barrel temperature was indicative of a reduction in injection
temperature. The reduction in hydraulic pressure was achieved even
while increasing the injection speed, which at a fixed blowing
agent percentage, would otherwise be expected to increase hydraulic
pressure.
[0055] This example illustrates the effectiveness of the method of
the invention for producing an in-mold decorated article at low
injection pressures and temperatures.
EXAMPLE 2
Production of In-Mold Decorated Article Including Polymeric
Material and Fabric Substrate without a Barrier Layer
[0056] An injection molding machine (Milacron-400 ton) was modified
to have a configuration similar to the system illustrated in FIGS.
1A-1C. A pillar mold was used. The mold contained 3 gates and a hot
runner system with 6 control zones. Only 1 gate was utilized in the
experimentation.
[0057] A single layer polypropylene fabric with no backing or
separate barrier layer was placed within the mold cavity. The
fabric had a thickness of about 0.010 inches. Polymeric pellets
having a PP composition which included 20% talc by weight (Mitsui
Plastics TS0P5, 30 MFR) were fed into the molding machine using the
hopper. Trials were run using different blowing agent conditions,
barrel temperatures, and hydraulic pressures. The conditions were
summarized in Table 2.
TABLE-US-00002 TABLE 2 Process Conditions Barrel Hydraulic Blowing
Agent Temperature Injection Speed Pressure (Type - Wt. %) (.degree.
C.) (inch/sec) (psi) Solid - 0% 204 1.0 1550 N.sub.2 - 0.5% 193 1.0
1420
[0058] When no blowing agent was used, polymeric material bled
through the fabric substrate. Thus, the in-mold decorated article
produced without blowing agent was unacceptable.
[0059] In-mold decorated automotive pillars having a polymeric PP
portion adhered to the fabric substrate were produced using blowing
agent (N.sub.2). No polymeric material bled through the fabric when
blowing agent was used. The pillars had a curved cross-section, a
length of about 30 inches, and a thickness of about 0.20 inches.
The pillars produced using blowing agent (N.sub.2) had a void
fraction of about 0.14. The polymeric portion of the in-mold
decorated pillars produced using blowing agent (N.sub.2) was a
microcellular material having an average cell size of about 50
microns. FIG. 4 is an SEM photo showing the microstructure of a
typical cross-section of the microcellular material of the in-mold
decorated article.
[0060] The use of blowing agent reduced the hydraulic pressure and
barrel temperature which were used to produce the in-mold decorated
articles. The reduction in hydraulic pressure was indicative of a
reduction in injection pressure and the reduction in barrel
temperature was indicative of a reduction in injection
temperature.
[0061] This example illustrates the effectiveness of the method of
the invention for producing an in-mold decorated article including
a single fabric substrate without a barrier layer due to reductions
in injection pressure and temperature. Furthermore, this example
illustrates the production of an in-mold decorated article
including a microcellular polymeric portion.
[0062] Those skilled in the art would readily appreciate that all
parameters listed herein are meant to be exemplary and that the
actual parameters would depend upon the specific application for
which the methods and articles of the invention are used. It is,
therefore, to be understood that the foregoing embodiments are
presented by way of example only and that, within the scope of the
appended claims and equivalence thereto, the invention may be
practiced otherwise than as specifically described.
* * * * *