U.S. patent application number 11/293490 was filed with the patent office on 2006-06-29 for structural reinforcement article and process for preparation thereof.
Invention is credited to Michelle L. Boven, Jason C. Brodil, Glenn G. Eagle, Zhicheng Li.
Application Number | 20060141235 11/293490 |
Document ID | / |
Family ID | 32962679 |
Filed Date | 2006-06-29 |
United States Patent
Application |
20060141235 |
Kind Code |
A1 |
Boven; Michelle L. ; et
al. |
June 29, 2006 |
Structural reinforcement article and process for preparation
thereof
Abstract
The invention is a process for the preparation of article
comprising placing a film on each inner surface of each part of a
two part mold; placing an article in the mold with film located
between the surface of the mold and the article such that there is
a small space between the article and the surface of the mold;
closing the mold about the article; injecting between the film and
the article an expandable plastic material under conditions that
the article is coated with the expandable material and the
expandable material does not expand; removing the plastic article
with the expandable material coated thereon with the two films
attached to the expandable plastic material. In another embodiment
the invention is an article comprising a shaped plastic article; an
expandable material coated in the shaped plastic article; and a
film covering the material coated shaped plastic article. In
another embodiment the invention is a method of reinforcing a
structural member which comprises inserting an article according to
this invention into a cavity of the structural member and heating
the structural member and the article to a temperature at which the
expandable plastic material expands and the film or the expandable
material bonds to the inner surface of the structural member so as
to fix the location of the article in the structural member.
Inventors: |
Boven; Michelle L.;
(Clarkston, MI) ; Li; Zhicheng; (Troy, MI)
; Eagle; Glenn G.; (Bloomfield Hills, MI) ;
Brodil; Jason C.; (Midland, MI) |
Correspondence
Address: |
THE DOW CHEMICAL COMPANY
INTELLECTUAL PROPERTY SECTION
P. O. BOX 1967
MIDLAND
MI
48641-1967
US
|
Family ID: |
32962679 |
Appl. No.: |
11/293490 |
Filed: |
December 2, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10794909 |
Mar 5, 2004 |
|
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|
11293490 |
Dec 2, 2005 |
|
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|
60452007 |
Mar 5, 2003 |
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Current U.S.
Class: |
428/304.4 ;
264/46.4 |
Current CPC
Class: |
Y10T 428/1376 20150115;
Y10T 428/249953 20150401; B29C 44/3484 20130101; B29C 44/1285
20130101; B29C 44/14 20130101; B62D 29/002 20130101; B29C 44/18
20130101 |
Class at
Publication: |
428/304.4 ;
264/046.4 |
International
Class: |
B32B 3/26 20060101
B32B003/26 |
Claims
1-7. (canceled)
8. An article comprising i) a shaped article; ii) an expandable
material coated in the shaped article; iii) and a film covering the
expandable material coated shaped article.
9. An article according to claim 8 wherein the shaped article
comprises a shaped hollow article with a rigid plastic shell or a
shaped solid foam plastic article.
10. An article according to claim 8 wherein the expandable material
exhibits adhesive properties under conditions at which the
expandable material is expanded.
11. An article according to claim 8 wherein the article is a
structural reinforcement member adapted to reinforce a cavity in a
structure.
12. An article according to 8 wherein the film is capable of
bonding to surfaces at a temperature above the temperature at which
the film covered expandable material coated article is
prepared.
13. An article according to claim 12 wherein the film bonds to
surfaces at a temperature of about 160.degree. C. to about
205.degree. C.
14. An article according to claim 10 wherein the expandable
adhesive comprises an epoxy resin based adhesive.
15. An article according to claim 9 wherein the shaped plastic
article comprises a solid polyurethane foam.
16-17. (canceled)
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/452,007, filed Mar. 5, 2003.
FIELD OF INVENTION
[0002] This invention relates to an article coated with an
expandable composition, such as a structural reinforcement article
which is adapted to reinforce a structural member, such as a
structural member of an automobile, a house or any construction
which includes structural members designed to give structural
integrity to the construction. In another embodiment the invention
is a process for preparing an article coated with an expandable
composition. In yet another embodiment the invention is a method of
reinforcing a structural member using the structural reinforcement
articles of the invention.
BACKGROUND OF INVENTION
[0003] The automotive industry is under regulatory pressure to
reduce average fuel consumption and improve the crashworthiness of
vehicles. To improve fuel consumption lighter and thinner materials
are being used. Unfortunately, this reduces the structural
integrity of parts of an automobile. To compensate automobile
producers place structural reinforcing members into hollow
structural members, such as A and B pillars of automobiles.
Structural reinforcing members and their use in automobiles are
described in Thum U.S. Pat. No. 5,194,199; Keller U.S. Pat. No.
6,146,565; Wycech U.S. Pat. No. 6,165,588; Hopton et al. U.S. Pat.
No. 6,199,940; Barz U.S. Pat. No. 6,131,897 and Sheldon et. al, US
Patent Application 2002/0160130, all incorporated herein by
reference. These structural reinforcing articles generally comprise
some structural part, which gives the reinforcing articles shape
and strength, which structural part is based on a light weight
metal or a rigid plastic. The structural part is coated with an
expandable composition, which expands when heated to a certain
temperature. Typically the expandable composition expands to
contact the inner walls of the structural member being supported.
Upon expansion, the expandable composition functions to hold the
structural reinforcing member in place permanently by adhering to
the inner wall of the structural member or by friction because the
expanded composition is wedged tightly in position. The expanded
composition also helps transfer a load from sheet metal to inner
reinforcement to sheet metal.
[0004] The expandable composition is applied to the structural part
of the structural reinforcing member by conventional means known in
the art, such as hand applied sheets of epoxy, compression molding,
resin transfer molding and injection molding. Some of the
expandable materials exhibit adhesive properties at elevated
temperatures. This is desirable for affixing the expandable
composition to the structural part of the structural reinforcing
member. The adhesive properties can cause problems in manufacturing
of the structural reinforcing member because it can be difficult to
remove the structural reinforcing member with the expandable
materials deposited thereon from the mold. In order to pump the
expandable material and apply it, it is necessary to heat the
expandable material and the mold to facilitate application.
Thereafter to prevent, or reduce adhesion to the mold, the mold is
cooled prior to opening the mold. Even when cooled some of the
expandable materials will still adhere to the mold, forcing an
operator to manually remove some of the expandable material.
Pleating the mold to application temperature and then cooling
before attempting to remove the coated structural reinforcing
member results in long processes, up to an hour per part per mold.
In high volume parts manufacture this results in the need for large
amount of capital to keep up with the demand for the part. In
addition to the long cycle times there are post process steps that
may need to take place to make a tack free part including but not
limited to dusting of the surface of the expandable material with a
material which renders the surface tack free such as glass
balloons.
[0005] What is needed is a part that can be manufactured in an
efficient manner with low part residence times in molds and little
or no post molding processing steps. What is also needed is a
process, which can produce expandable material coated articles,
such as structural reinforcing members, in a cost efficient manner
maximizing the productivity of tools used to manufacture the
parts.
SUMMARY OF INVENTION
[0006] The invention is a process for the preparation of article
comprising placing a film on the top inner and bottom inner half of
a insert molding tool; placing an article in the mold with film
located between the surface of the mold and the article; closing
the mold about the article such that there is a small space between
the article and the surface of the mold; injecting between the film
and the article an expandable material under conditions that the
article is coated with the expandable material and the expandable
material does not expand; removing the plastic article with the
expandable material coated thereon with the film attached to the
expandable material. Preferably, when the article is placed in the
mold, there is a small space between the article and the surface of
the mold; with the space between the article and the mold created
from crush stand offs on the article and or the over molding
tool.
[0007] In another embodiment the invention is an article comprising
a shaped article; an expandable material coated in the shaped
article; and a film covering the expandable material coated shaped
article.
[0008] In another embodiment the invention is a method of
reinforcing a structural member which comprises inserting an
article according to this invention into a cavity of the structural
member and heating the structural member and the article to a
temperature at which the expandable material expands and the film
or the expandable material bonds to the inner surface of the
structural member so as to permanently fix the article in the
structural member.
[0009] The process of the invention allows the preparation of an
article coated with an expandable material in an efficient manner
allowing tools to cycle with a hold time of about 5 minutes or
less, and more preferably as low as about 60 to about 90 seconds
per part.
[0010] In another embodiment the invention is a method of molding
with a film in which the melting point of the film is lower than
the temperature of the molding tool during molding operations. The
film with the low melting point is placed on top of another film
with a melting point above the molding temperature of the tool
during molding operations. The film with the high melting point is
referred to as the carrier film. The film with the low melting
point is referred to as the leave-on film. This two film
combination is placed on the top half and bottom half of the tool.
The carrier film and leave-on film are placed into the tool
together with the carrier film closest to the tool and the leave-on
film closest to the open cavity portion of the tool. The two film
combination can be placed into the tool as one piece, with the two
filn combination folded over with the insert in the middle of the
film or the two film combination can be placed in the tool as two
separate film pieces. The carrier film allows the use of a leave-on
film with a melting temperature lower then the temperature needed
to process the expandable material. Preferably, the carrier film
and the leave-on film are separated after removal from the mold.
The removed carrier film can thereafter be discarded.
DESCRIPTION OF FIGURES
[0011] FIG. 1 shows a cross-sectional view of a structural
reinforcing member.
[0012] FIG. 2 illustrates an apparatus used to perform the process
of the invention.
[0013] FIG. 3 shows a cross-sectional view of a structural
reinforcing member with a three layer film.
DETAILED DESCRIPTION OF THE INVENTION
[0014] This invention relates to a process for efficiently applying
an expandable material to a shaped article in an efficient manner
and to the article so prepared. Shaped article as used herein means
any article which is formed into a shape near its' final use shape.
Generally, the article can be fabricated from any known material,
such as plastic, metal, ceramic, glass and the like. In
applications where weight is a key factor, such as where the shaped
article is used in an automobile, lighter materials such as
plastics are preferably used. The plastic material may be nylon,
styrenic, polyolefin, such as polyethylene or polypropylene,
polycarbonate, polyester, polyurethane, polyepoxide, poyurea,
polyphenylene sulfide, polyetherimide, toughened plastics such as
ABS (acrylonitrile-butadiene-styrene) or previously mentioned
materials containing elastomers such as styrene-alkadiene block
copolymers, ethylene-octene copolymers and the like, and blends
thereof, such as a polycarbonate-ABS blends. The rigid plastic
shaped articles can be solid or hollow with hollow shaped articles
preferred for applications where weight is a critical factor. In
another embodiment the shaped article is foam. Foamed articles are
preferably solid and provide lower density and higher strength.
Preferably the shaped foamed articles are prepared from foam which
can withstand the time and temperatures to which the expandable
material must be exposed to expand. Preferably, the foam is based
on polystyrene, polyurethane, polyurea or epoxy resins; more
preferably on polyurethanes, polyureas, epoxy resins and most
preferably polyurethanes. In a preferred embodiment the foam used
is a foam described in the Allen, U.S. Pat. No. 6,423,755B1,
incorporated herein by reference.
[0015] The shaped article can be used in any application where it
is necessary to hold the article into place permanently in another
structure. Such applications include in transportation vehicles,
such at automobiles, light trucks, heavy-duty trucks and busses,
rail cars, aircraft; buildings, appliances and heavy machinery.
Preferably, the articles of the invention are used to reinforce
structural members. A structural member is a part of a structure,
as described above, which supports or protects the structure. In
this embodiment, the articles of the invention are structural
reinforcing members, which means that they are used to structurally
strengthen the structure and integrity of the structural member
into which they are inserted. Generally, the structural reinforcing
members are inserted into hollow cavities of the structural member
to improve the structural integrity of the structural member.
Preferably the structural reinforcing members are used in buildings
or vehicles, preferably vehicles, such as automobiles and light
trucks. The articles of the invention may further comprise a means
of locating and holding the article into a cavity until exposed to
conditions such that the expandable material expands to hold the
article in place. The means of locating and holding the article in
place can be means which function to locate and/or hold the article
in place prior to expansion of the expandable material. Such means
include shaped standoffs or projections, tabs affixed to the part
by mechanical affixing means (screws, nails, clips and the like),
pressure sensitive adhesives, magnets and the like.
[0016] The expandable material useful in the invention can be any
material which expands under controlled conditions and which does
not expand under conditions of application to the part as described
herein. In a preferred embodiment the expandable material exhibits
adhesive properties under controlled conditions. It is also
preferred that the expandable material is dry and not tacky to the
touch at ambient conditions to facilitate shipping and handling. In
the preferred embodiment, the expandable material is a polymeric
material, and more preferably an expandable adhesive. A typical
expandable adhesive includes a polymeric base material, such as an
epoxy resin or ethylene-based polymer which, when compounded with
appropriate ingredients (typically a blowing and curing agents),
expands and cures in a reliable and predictable manner upon the
application of heat. The expandable adhesive will also crosslink
upon curing rendering the material incapable of further flow or
shape change. Any material that is heat-activated and expands and
cures in a predictable and reliable manner under appropriate
conditions, while meeting structural requirements, for the selected
application can be used. Other useful materials include
polyolefins, copolymers and terpolymers with at least one monomer
type an alpha-olefin, phenol/formaldehyde materials, phenoxy
materials, and polyurethane materials with high glass transition
temperature such as disclosed in U.S. Pat. No. 5,766,719; U.S. Pat.
No. 5,755,486, U.S. Pat. No. 5,575,526; U.S. Pat. No. 5,932,680,
all incorporated by reference.
[0017] In a preferred embodiment, the expandable adhesive is a
material comprising a) a 1-part epoxy resin; b) a viscosity
increasing agent; and c) not greater than 25 parts by weight of an
inorganic filler, based on 100 parts of the epoxy resin. The
expandable material that is used to coat the article is prepared as
a 1-part epoxy resin formulation. Preferred epoxy resins include
diglycidyl ethers of bisphenol A and bisphenol F, as well as
oligomers of diglycidyl ethers of bisphenol A and bisphenol F,
either alone or in combination. More preferably, the epoxy resin is
a mixture of diglycidyl ether of bisphenol A and an oligomer of
diglycidyl ether of bisphenol A. The epoxy resin preferably
constitutes from about 40 weight percent to about 80 weight percent
of the total materials used to make the expandable adhesive. The
viscosity increasing agent is a material that increases the
viscosity of the blend used to make the expandable adhesive. The
viscosity increasing agent is preferably used as a fine powder
(volume mean average <200 .mu.m) and preferably has a T.sub.g of
at least about 70.degree. C., more preferably at least about
100.degree. C. Examples of preferred polymeric viscosity increasing
agents include polymeric acrylates and methacrylates, more
preferably polymethylmethacrylate (PMMA), most preferably a
carboxylic acid functionalized PMMA, such as the commercially
available Degalan.TM. 4944F PMMA (available from Rohm America). The
polymeric viscosity increasing agent is used in an effective amount
to control release of gas from the blowing agent so as to reduce
cell size in the resultant cured resin. The concentration of the
polymeric viscosity increasing agent is preferably at least 2, more
preferably at least 5, and most preferably at least 10 weight
percent; and preferably not more than 40 weight percent, more
preferably not more than 30 weight percent, and most preferably not
more than 20 weight percent, based on the total materials used to
make the expandable adhesive. The polymerization of the epoxy resin
is catalyzed by an effective amount of a polymerizing promoting
catalyst, preferably from about 0.1 weight percent to about 2
weight percent, based on the total materials used to make the
expandable adhesive. Preferable catalysts include, but are not
restricted to amides, blocked amines, ureas and imidazoles. An
example of a preferred catalyst is Acclerine CEL 2191
(1-(2-(2-hydroxbenzamido)ethyl)-2-(2-hydroxyphenyl-2-imidazoline,
which has the following chemical structure: ##STR1## The
preparation of this catalyst is described by Bagga in U.S. Pat. No.
4,997,951, which description is incorporated herein by
reference.
[0018] The epoxy resin is expanded to a desired volume in the
presence of an effective amount of a blowing agent, preferably from
about 0.5 weight percent to about 10 weight percent, based on the
total materials used to make the expandable adhesive. Preferred
blowing agents are heat activatable at a temperature of about
100.degree. C. or greater, more preferably at about 120.degree. C.
or greater; and even more preferably about 150.degree. C. or
greater, and most preferably about 160.degree. C. or greater and
preferably not greater than about 200.degree. C. Examples of
suitable blowing agents include those described by Fukui in U.S.
Pat. No. 6,040,350, column 4, lines 25-30, which section is
incorporated herein by reference. An example of a preferred
commercially available blowing agent is Celogen AZ.TM. 120
azodicarbonamide (from Crompton). The epoxy resin is cured using an
effective amount of a curing agent, preferably from about 2 to
about 10 weight percent, based on the total materials used to make
the expandable adhesive. Examples of suitable curing agents include
those described by Fukui in column 4, line 66-67 and column 5,
lines 1-9, which sections are incorporated herein by reference. The
expandable adhesive may also include organic filler such as a
polyethylene copolymer or an inorganic filler such as calcium
carbonate. The amount of inorganic filler is preferably not greater
than about 25 parts by weight, more preferably not greater than
about 15 parts by weight, and most preferably not greater than
about 10 parts by weight, relative to 100 parts by weight of the
expandable adhesive.
[0019] A preferred expandable adhesive is prepared by combining and
mixing the epoxy resin, the blowing agent, the catalyst, the curing
agent, the viscosity increasing agent, and optionally the inorganic
and organic fillers at a temperature above ambient temperature,
preferably from about 30.degree. C. to about 50.degree. C. for
about 15 minutes to about 2 hours. Entrapped air is removed in
vacuo.
[0020] The preferred cured (expanded) adhesive has a Young's
modulus of at least about 500 MPa, more preferably at least about
700 MPa, and most preferably of at least about 1000 MPa at 100
percent expansion. Furthermore, the preferred cured adhesive has
surprisingly small voids, preferably with a number weighted mean
diameter of less than about 1000 .mu.m, more preferably less than
about 500 .mu.m, and most preferably less than about 100 .mu.m.
Consequently, the adhesion of the SFI (structural foam insert) to
the automotive structure is strong and durable.
[0021] The expandable material must also be capable of being pumped
at temperature below the temperature at which the expandable
material expands. This is to facilitate injection of the expandable
material into the mold.
[0022] Alternatively the expandable material can be a material
without adhesive properties. This is enabled when the film
functions to bond the expandable material coated structural
reinforcement member to the structural member. Any polymeric
material, which can be expanded under controlled conditions and can
be applied to the structural reinforcement member, can be used in
this embodiment, examples include polyvinyl chloride (PVC), Poly
Methyl Methacrylate (PMMA), phenoxy thermoplastics which further
contain blowing agents.
[0023] The film used in this invention can be any film, which can
retain its structural integrity when exposed to the conditions of
applying the expandable material to the plastic article, and will
not adhere to the mold surface under such conditions. There are two
general types of films used. In one embodiment, the film does not
have any adhesive character and is simply used to allow easy
removal of the part from the mold. In another embodiment, the film
has adhesive character under conditions where the expandable
material expands. In this embodiment the expandable material does
not require adhesive character.
[0024] In the embodiment wherein the film does not require adhesive
character, the film is preferably a low surface energy film,
preferably a polyolefin, such as high density polyethylene, low
density polyethylene, fluorinated polyethylene or polypropylene.
Alternatively, the film can be a high surface energy film coated
with a low surface energy coating, for instance polyester coated
with a low surface energy coating. In the embodiment where the film
provides adhesion to the structural member, any film, which
provides adhesion at the temperature of expansion of the expandable
material, can be used. In one embodiment the film can be a corona
treated polyolefin. In another embodiment the film can be a
multilayer film with a layer on the outside which demonstrates
adhesive character under conditions of expansion of the expandable
material. The adhesive layer could be ethylene vinyl acetate or an
ethylene acrylic acid co-polymer layer. Alternatively the film can
function as a hot melt adhesive under conditions of expansion.
Where the film functions as a hot melt adhesive it is desirable
that the expandable material have adhesive properties also.
[0025] In another embodiment the film can be sprayed or coated on
the mold prior to placing the article into the mold. Water based
high molecular weight epoxy resins are useful in this embodiment,
for example EPI-REZ.TM. 3540 water based epoxy. The water-based
epoxy is contacted with the mold and the water is flashed off such
that a film is formed on the mold. Thereafter the article is placed
in the mold.
[0026] Molds used to prepare the articles of the invention are
generally insert molds wherein an article is placed into the cavity
of the tool. With the mold closed an outer shell cavity is created
which is close to the size of the article being coated. The molds
have at least one injection port to inject the expandable material
into the mold. The molds need to have the capability to heat the
expandable material and the article to facilitate application of
the expandable material to the article. Generally the molds need to
have the capability to be heated to a temperature high enough that
the expandable material can be processed or flows and below the
temperature at which the expandable material expands, such
temperatures are about 90.degree. C. or greater, and preferably
about 150.degree. C. or less and more preferably about 130.degree.
C. or less.
[0027] In the process of the invention, the film is applied to the
mold as described; the article is placed in the mold with the film
between the mold and the article. The expandable adhesive is then
injected into the hot mold (about 90.degree. C. to about
150.degree. C., preferably to about 150.degree. C.) that surrounds
and conforms to the shape of the article to achieve thickness of
adhesive over article ranging from about 1 mm to about 4 mm, the
thickness can vary across the surface of the articles. The article
is left in the mold for sufficient time to achieve a coating of the
desired thickness on the article. If the expandable material is
thermoplastic in nature this is sufficient. If the coating is a
liquid thermoset material, such as a paste epoxy, the material may
need to be heated for an additional period of time to gel the
expandable material to achieve the desired integrity of the
coating. Generally the residence time of the article in the mold is
about 6 minutes or less, preferably 3 minutes or less, and most
preferably 90 seconds or less.
[0028] After the article is removed from the mold, the article is
cooled. Generally, the mold can immediately be cycled, that is
another of the described process can be started.
[0029] There are two types of film that would require defilming.
The first is a film that would be removed and under that would be
the expandable material. The second would be the multi-layer film
using the carrier and leave-on film. Both types of film can be
defilmed or removed after cooling to or below ambient or it can be
left on the article until just before inserting it in the cavity of
the structural member. For the first film, it is advantageous to
leave the film on until just before insertion into the cavity of
the structural member to facilitate handling and exposure of
operators to uncured expandable material. If the film has adhesive
properties, such as the leave-on film, it can be left on the
article when it is inserted in the cavity of the structural member.
In the embodiment where the film is entirely removed after molding,
it is desirable to coat the part with a coating which renders the
surface of the part non-tacky. The coating is generally a
particulate material of a relatively small size. Any coating which
renders the surface non-tacky may be used. Preferable coating
materials include calcium carbide glass balloons and the like.
[0030] In one embodiment, two films may be used. One film is an
adhesive film (leave-on film) and the second is a carrier film
which does not have adhesive properties. In one embodiment, the
carrier film does not adhere to the adhesive (or leave-on) film.
The films typically are arranged in the mold with the carrier film
located adjacent to the mold and the adhesive film located adjacent
to the part. Preferably, the carrier film has a relatively high
melting temperature of 130.degree. C. or greater, and preferably
160.degree. C. or greater. The carrier film can be prepared from
any material which can maintain its integrity under molding
conditions. Further, it is preferable that the carrier film not
adhere in a significant way to the mold under molding conditions.
Preferably, the carrier film is prepared from a relatively
non-polar polymeric material. Preferred polymeric materials are
polyolefins or blends containing a volumetric majority of a
polyolefin. Preferred polyolefins are polypropylene and
polyethylene. A preferred polyethylene is low density polyethylene.
Alternatively, the film could be a fluorinated polyethylene or
silicon coated polyester. Most preferably, the carrier layer is a
homopolymer polypropylene. The thickness of the carrier film is
chosen to allow the carrier film to maintain its integrity during
molding. Maintain its integrity means the film continues to stay in
film form and can be handled in film form. Preferably, the carrier
layer has a thickness of about 2 mils 0.0051 (mm) or greater and
more preferably 2.5 mils (0.0645 mm) or greater. Preferably, the
carrier layer has a thickness of 8 mil (0.20 mm) or less, more
preferably about 6 mil (0.15 mm) or less and most preferably about
3 mil (0.076 mm) or less.
[0031] The second film is an adhesive or leave-on film. The
leave-on film functions to protect the surface of the part during
handling and transport. It also prevents contact of anyone who
handles the part with the adhesive coated on the part. The leave-on
film may also serve the function of an adhesive which aids in
bonding the part in place in the structural member which is
reinforced. Alternatively, the leave-on film melts under automobile
paint oven conditions allowing the adhesive coated on the part to
read through the film to bond to the inside surface of the
structural member reinforced. Preferably, the leave-on film is
tacky at elevated temperatures, but not tacky at ambient
temperatures, about 15 to about 35.degree. C. Preferably, the film
is tacky or melts at the temperatures of an automotive paint oven.
The leave-on layer may also be corona treated to improve bonding to
the adhesive on the part during molding. The leave-on film can be
prepared from any polymeric material which provides the properties
discussed hereinbefore. Preferably, the leave-on film comprises a
polymer which contains polar functional groups, such as carboxylic
acid, acetate, hydroxyl and the like. In another embodiment, the
leave-on film comprises a blend of a polymer with functional groups
and a non-polar polymer for instance a polyolefin, copolyester or
copolyamide, a polyolefin. Preferred polar group containing
polymers include ethylene vinyl acetates, ethylene ethyl acrylates,
maleic anhydride grafted polyolefins, alkylene acrylic acids (such
as ethylene acrylic acid) blends thereof and the like. The leave-on
film is preferably thick enough to render the surface of the part
non-tacky under ambient conditions. Preferably, the thickness of
the leave-on film is 0.1 mils (0.003 mm) or greater and most
preferably about 0.4 mil (0.01016 mm or greater). Preferably, the
leave-on film is about 4 mils (0.1 mm) or less, more preferably
about 2 mils (0.0051 mm) or less and most preferably about 0.8 mils
(0.020 mm) or less.
[0032] In one embodiment, the two films can be formed as a single
two-layer film and used as such in the preparation of the part. In
this embodiment, the carrier portion of the film must be removable
from the part after fabrication and the leave-on film is left
behind. In this embodiment, the two layer film is placed in the
mold, the mold is closed, and the adhesive is injected between the
part and film. After the part is removed from the mold, the carrier
film is removed and the leave-on film is left behind.
[0033] In another embodiment, the film can comprise three layers;
the carrier film, the leave-on film and an adhesion layer located
between the two layers which function to adhere the two layers
together. The adhesion properties of the intermediate layer are
preferably sufficient to hold the layers together during
processing, but not so strong as to prevent the carrier film from
being removed. Preferably, the intermediate film has a relatively
strong adhesive bond with the carrier film and a relatively weak
adhesive formed with the leave-on film so as to allow removal of
the intermediate film with the carrier layer. The intermediate film
can be prepared from any polymer which forms an adhesive bond with
both the carrier and leave-on films and which allows the carrier
film to be removed. Preferably, the intermediate layer is prepared
from a non-polar polymer. Preferred polymers used are polyolefins,
with homopolymer polypropylenes preferred. The intermediate film
has sufficient thickness to hold the two other layers together
during handling. Preferably, the intermediate layer has a thickness
of about 0.2 mils (0.0051 mm) or greater. Preferably, the
intermediate layer has a thickness of about 1 mil (0.025 mm) or
less thick and more preferably about 0.4 mil (0.010 mm) thickness
or less.
[0034] The films can be fabricated by well-known techniques such as
multilayer coextrusions, casting or blown film processes.
[0035] The resultant article is affixed within a cavity of a
structural member so as to create a gap between the article and the
structural member of about 1-mm to about 4-mm. The structure is
then exposed to conditions at which the expandable material cures,
preferably to temperatures of about 140.degree. C. or greater, more
preferably 150.degree. C. or greater, most preferably about
160.degree. C. or greater, and preferably less than 205.degree. C.
and more preferably less than 200.degree. C., preferably for a time
of about 15 minutes or more and preferably about 25 minutes or
more. In the embodiment where the structure is an automobile the
expandable material is expanded during the e-coat process, with
residual e-coat liquid escaping through the gaps between article
and the structural member. Finally, the e-coat and expandable
adhesive are cured at a suitable curing temperature, preferably
between about 150.degree. C. and about 200.degree. C.
[0036] FIG. 1 shows a cross-sectional view of a portion of
structural reinforcing member, (10). The structural reinforcing
member has a film (11) adhered to an expandable material layer (12)
coated onto a shaped rigid foam structure (13).
[0037] FIG. 2 illustrates a partially closed apparatus (20) for
performing the process of the invention. The apparatus (20)
comprises two halves of a mold (21 and 22) which when closed forms
a cavity (23). The apparatus further comprises an injection nozzle
(24) having a central tube (25) adapted for injecting expandable
material into the mold cavity (23). About a part (26) located in
the mold cavity (23) are two film portions (27) located between the
part (26) and the halves of the mold (21 and 22). To seal between
the injection nozzle (24) and the film portions (27), several
methods can be used, such as 0 rings (28) as illustrated here or
soft deformable seals, the film (27) itself squeezed between the
mold (21 and 22) and the injection nozzle (24). There are 0 rings
(28) located about the injection nozzle (24). The 0 rings (28) seal
the film (27) so that any injected material stays between the film
portions (27) and part (26). Located between the part (26) and the
walls of the mold halves (21 and 22) layered with the film (27) is
a gap (29) which is large enough to accommodate a coating of
expandable material.
[0038] FIG. 3 is similar to FIG. 1 except a three-layer film (11)
is used. The figure illustrates a cross-sectional view of a
structural reinforcing member (10). The structural reinforcing
member (10) has a film (11) adhered to an expandable material layer
(12) coated onto a rigid foam structure (13). The film (11)
comprises three layers, a leave-on layer (14) adjacent to the
expandable material layer (12); an adhesion layer (15) located
between the leave-on film layer and a carrier film layer (16)
wherein the carrier film layer (16) is located as the outside film
layer.
[0039] The process of the invention can be described in the context
of FIG. 2. The apparatus or mold (20) is opened and film (27) is
placed in each mold half (21 and 22). A part (26) is placed in the
cavity (23) of one of the mold halves (22). The other mold half
(21) is closed so that the two mold halves (21 and 22) surround the
part (26) with film (27) surrounding the part (26) and located
between the part (26) and the mold halves (21 and 22). There is a
gap (28) between the part (26) and the mold halves (21 and 22)
layered with the film (27). The film (27) is sealed by O rings (28)
about the injection nozzle (24). The mold is heated to the desired
temperature (about 90.degree. C. to about 150.degree. C.).
Expandable material is injected into the gap (29) between the part
(26) and film (27) through the tube (25) of the injection nozzle
(24), until the entire gap (29) is filled. If the expandable
material needs to about the part (26), the part (26) with the
injected epoxy is maintained in the mold cavity (23) until the
expandable material gels. Thereafter the mold half (21) is opened
to open the mold cavity (23). The part (26) with expandable
material coated thereon and film (27) adhered to the expandable
material is removed from the mold, and it is coated. The apparatus
(20) is now ready to repeat the process.
SPECIFIC EMBODIMENTS
[0040] The following examples are included to illustrate the
invention and are not meant to limit the scope of the claims.
Unless otherwise stated all parts and percentages are by
weight.
[0041] To automate the process and allow for multiple molds to feed
from one gun, a sheet separator is needed. This is a reusable or
disposable piece that keeps the sheets separated for the gun to
enter but allows the mold to be closed without the gun in place. A
temporary plug may be used after the gun is removed to prevent
black flow of the expandable coating from leaving the mold. The gun
can now be transferred to the next mold which is already closed and
ready to be filled.
[0042] BETAMATE.TM. 73607 adhesive comprises a mixture of 30 to 40
percent by weight of a Bisphenol A based liquid epoxy resin having
an epoxy equivalent weight of about 181, 15 to 25 percent by weight
of a blend of a high viscosity advanced liquid epoxy resin based on
Bisphenol A having an epoxy equivalent weight of 230 to 250 and a
solid advanced epoxy resin based on Bisphenol A having an epoxy
equivalent weight of about 675 to 750; polymethyl methacrylate as a
gelling agent, dicydicyanamide as a curing agent and a mixture of
phenyldimethyl urea and a modified benzamide (MMB 2191 available
from Celerity LLC as catalysts and as a blowing agent
azodicarbonamide.
[0043] XUS 66185 film comprises three layer a 0.8 mil (0.02032 mm)
layer of ethylene acrylic acid available from The Dow Chemical
Company, a film of the trademark PRIMACOR.TM. 3330, an intermediate
layer of 0.3 mils (0.00762 mm) of a homopolymer polypropylene and
2.5 mil (0.0635 mm) layer of a copolymer of polypropylene blended
with a minor amount of polyethylene available from The Dow Chemical
Company under the designation DC783.00, XV661.
EXAMPLE 1
[0044] 175 grams of BETAMATE.TM. 73607 adhesive was applied to a
less than 1 mil (0.0254 mm) LDPE (low density polyethylene) film. A
second sheet was placed on top of the opposite side of the epoxy
forming a sandwich configuration, film/epoxy/film. 2 mm spacers
were placed around the perimeter of the epoxy in a 25 cm square
shape between the two pieces of film to set the epoxy thickness.
The sandwich film/epoxy/film was placed into a heated press preset
to 110.degree. C. The press was then closed squeezing the epoxy to
a thickness of 2-mm. After 5 minutes the press was then opened and
the sheet was easily removed from the metal press. The sheet was
cooled to room temperature and the film was then easily
removed.
EXAMPLE 2
[0045] 175 grams of BETAMATE.TM. 73607 adhesive was sandwiched
between two sheets of a LDPE film, 3.5 mil (0.0889 mm) with a
corona treatment on one surface of the film. On one side of the
epoxy mass the film with the treatment was placed towards the epoxy
and on the opposite side of the epoxy mass the treatment was placed
away from the epoxy. The film/epoxy/film sandwich configuration was
heated for 5 minutes in the heated metal press to form a 2-mm
casting. A 10-cm.times.10-cm square was cut out of the 25-cm square
casting and placed between hot dip galvanized (HDG) panels with a
2-mm air gap, using spacers to form the air gap. The HDG
panel/film/epoxy/film/HDG panel sandwich configuration was than
baked for 45 minutes @ 170.degree. C. Each HDG panel was pulled
away from the epoxy, the side with the treatment towards the epoxy
came off the HDG panel easily, very little to no adhesion was
observed between the non treated side of the film and the HDG
panel. The treated side of the film bonded to the epoxy and could
not be removed. The side with the treatment towards the HDG panel
was very difficult to remove from the HDG panel, 100 percent
cohesive failure was observed.
EXAMPLE 3
[0046] A Teflon sheet with an adhesive backing was adhered to a HDG
panel. Two of these Teflon/HDG panels were prepared. Then one coat
of water based epoxy, EPI-REZ* 3540-WY-55, was brushed onto the
Teflon sheets and the water was allowed to flash off. The
BETAMATE.TM. 73607 epoxy adhesive was then applied between the two
epoxy-coated panels. Two mm spacers were placed around the
perimeter of the epoxy. This sandwich configuration was then placed
into the heated press at 110.degree. C. for 2 minutes, pre-gelling
the epoxy into a 2 mm casting. The sandwich configuration was
cooled to 55.degree. C. The sandwich configuration was pulled apart
and the water-based epoxy and the expandable epoxy were easily
pulled away from the HDG panel. The water based epoxy film was
bonded to the expandable epoxy surface with a tack free
surface.
[0047] This pre-gelled epoxy dried with the water based epoxy
coating was placed between two HDG panel with 4 mm spacers (i.e. 2
mm air gap) and baked at 170.degree. C. for 45 minutes. 100 percent
cohesive failure was observed between the epoxy and the steel
panel. The water-based epoxy film did not interfere with the
adhesion.
EXAMPLE 4
[0048] A 16'' (40.64 cm) square piece of XUS 66185 3 layer film was
placed on the bottom half of the heated tool 250.degree. F.
(121.degree. C.) with the carrier layer adjacent to the heated
mold, the foam article was placed on top of the leave-on layer of
the film and a second piece of the XUS 66185 film was placed on top
of the foam part with the carrier layer adjacent to the heated top
half of the mold. The mold was then closed leaving a 2 to 3 mm gap
between the film and the tool. A 132 gram mass of BETAMATE.TM.
73607 expandable adhesive was dispensed and injected into the open
area between the foam and the leave-on layer of the film.
[0049] The tool was opened after 90 seconds; the foam/epoxy/film
part was removed. The multi layer film was adhered to the
expandable epoxy. After the part reached ambient temperature the
carrier and B intermediate layer of the film were easily removed
from the part as one layer.
* * * * *