Note: Descriptions are shown in the official language in which they were submitted.
WO 93/18218c~ ti 2 pcr/us93/o19o8
A MOLDED LINER ~OR A VEHICLE AND
METHOD OF ~KIN(3 THE SAME
Sro~_Refe~ to l~elated Ap~lica~iQn~
This is a continua8On~ part ap~lica~on of U. S. Patent Application
SeIial Nos.07/326,188, entitled ~A Coated ~iber Product with Superabsorbent
Particlesn; 071326,181, en~tled "A Natural Fiber Product Coated with a ThermosetBinder Material"; 07/326,196 entitled ~A Natural Fiber Product with a
Thermoplas~c Binder Matenal"; 07/673,685 entitled "Bin~er Cvated Discontinuous
Fibers with Adhered Par~culate Materials~ filed on March 22, 1991; and 07/6737899
enti~ed "Birlder Coated Discon~uous Fibers ~nth Adhered Particulate Materials"
filed on March 22, 1991; all of which are incorporated by reference herein in their
en~reties.
B~CRG~ OF THE I~ENTIC~N
This inveJldon relates generally to a process for making a molded liner
for a vehicle, such as a vehicle door~ trunk, ~ash or headliner and to such molded
ar~cles comprised of fibers with a substan~al majority of their surface area
20 con~nuously coated wi~ a b~der material.
One prior art approach for producing products of a fibrous material
and a binder is described in U. S. Patent No. 4,153,488 to Weigand; relating to a
process for fel~ng various fibers, including natural and synthetic fibers, with wood
and paper fibers being specifically mentioned. The use of binders such as starch,
25 synthe~c resins and adhesives to strengthen the structure is mentioned. The fibers
travel f~om a nozzle to a collecting screen for support with the variables affecting
fiber ~aYel being carefully ~on~olled, including the distance from the nozzle to the
collec~ng screen. The Weigand patent describes the introduction of an adhesive
binder as a liquid spray prior to collecting the fibers on the screen. The binder is
30 sprayed near the nozzle with the patent mentioning that the binder is able toadequately uniformly attach even to the fibers in the center of the stream without
wo 93/18~1x Pcr/u~93/01908
,. ,_ .
creating clots of plurality of fibers bound together by the binder. Vanous liquid
binders are described, including starch solutions, liquid latex binders, and other
liquid binders or suspensions in liquid such as resins. In connection with dry
binders, the patent mentions mixing between four and 30 pounds of powder for each
S 100 pounds of fiber in a hammermill prior to di~ecting the mixture from the fiber
nozzle. The patent also recites that various additives in liquid or solid form may be
incorporated into the mat, such as eoloIizers, fire retardants, seeds for grass,vegetables and the like. In liquid form, these may be included by spraying through
the nozzle either in combination with the liquid binder, if any, or alone. In solid
- 10 fonn, it is mentioned that these may be included into the product in the hammermill.
As a specific example, grass seed is introduced in a desired quantity into the outlet
of a cyclone collector with a stfar~h binder being applied by nozzles to the product
for binding purposes. A variet~ of products are disclosed in this patent including
paper wipe products, particularly diapers, wiping cloths, and molded products
including dash, hood, roof and trunk liners for automobiles. Fibers produced in
accordance with the Weigand process have been observed to exhibit a poor coatingof binder on the fibers. As a result, the presen~ inventors have deterrnined that
molded products produced from such fibers lack strength, which is rnore pronounced
in products of low density. Also, products from such fibers would lack desired
levels of stiffness and moisture resistance.
U. S. Patent No. 4,486,501 to Hol~ek is another patent relating to the
preparation of fibers coated with one or more polymers. Both thermoplastic and
thermoset~ng polymers are mentioned. Fiber material and polymers are fed to a
defiberator independently or the p~lymer or polymers are applied to the fiber
s 25 material prior to feeding the mixture to the defiberator. The patent mentions that it
.j is preferable to add the polymer or polymers to the fiber material in the form of a
~f suspension of solid particles or in the form of a solution, or in a melted or heat-
'7, softened condition. Spraying the polymer onto a web of fibers is specifically
mentioned. The fiber and polymers are e~posed to impact or grinding forces in the
defibe~ator wherein melting and softening of the polymer or polymers causes it to
adhere to the defiberated fibers. Coated fibers may be cooled within the defiberator
WO 93/18218 P~/US93/Olgl)8
4 t~ 2
so as, according to this patent, to prevent them from sticking together. The use of
polymers present at from five to thirty percent by weight of the fiber mass is
mentioned and the patent mentions that the polymer and additives normally shouldnot exceed fifty percent. Polymer additives are mentioned, including drying agents,
S hydrophobizing agents such as wa~, fungicides, antioxidants, softeners, tensides, etc.
The patent mentions that each single fiber processed in this manner is either
completely covered by a film of the polymer, or partly covered by flattened droplet
or film portions. Use of these fibers in mal~ng continuous web-shaped composite
products of various types, including paper, paste board, cardboard, plates, non--10 woven textile materials, insulating materials, etc. are mentioned. The fibers are
arranged in a layer having a suitable thickness and then bonded together, such as by
exposing them to solvents and heat. Hot pressing treatments or other finishing
treatments are mentioned and the use of higher pressures to produce more dense
structllres is also explained.
Testing of fibers produced in accordance with the Holbek reference has
conf~ned that the bulk of the fibers are poorly coated with binder material. In
addition, much of the binder ended up in clumpswith fibers. Clum~ed fibers are
more difficult to incorporate into finished products, for example, using air laying
techniques. In addition, poorly coated fibers again lack the desired strength.
U. S. Patent No. 5,057,166 to Young, Sr., et al. discloses a method
of producing fibers which are substantially continuously coated with a binder
material. A wide variety of thermoset and thennoplastic binders are mentioned assuitable for use in coating fibers. The use of thermoplasdc binders which are heat-
fused during processing of the fibers into products i5 mentioned. Densification of
a web of fibers prior to or after de~ivery to a thermobonder is also mentioned. Use
of the resulting material to manufacture products, such as absorbent pads, disposable
diapers, webs, and the like, is mentioned, with or without blending of untreatedfibers and with or wi~hout particulate additives.
This Young, Sr., et al. patent does not recognize the suitability of these
fibers for use in molded products, any relationship between the degree of coating
i
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fibers, densification and strength of molded articles, or processing molded articles
having areas of varying densities.
FIGS. 4 and 5 depict one prior art shaped liner 1 i 6 for the roof of a
vehicle. The headliner 116 has a densified edge section 119 which adds rigidity and
5 strength and a relatively undensified central section 117 which is intended to be
sound absorbing. Valious openings, some being shown in FI(: . 5, may be providedfor receiving fasteners and projecting vehicle components, such as overhead interior
vehicle lights. The automobile liner may be densified around the openings in
addition to along the vehicle periphery. Prior art automobile headliners resist
- 10 sagging, the effects of heat and temperature, and absorb sound to varying degrees,
depending upon the nature of the headliner.
From a sound absorbing and strength perspective, headliners of
fiberglass have been preferred ~or many applications. A high percentage of all
headliners being sold for automobiles are now made of fiberglass mats. FIG. 7
15 illus~ates a section of a prior art headliner 116, taken along A-A of PIG. 5, of a
fiberglass mat 200 with a hydroentangled nonwoven back overlay sheet 202. The
mat 200 is iypically formed of long glass fibers~,which are sprayed with phenolis
, - resin and then heated to tack the material together. Latex material is sometimes
applied to these fibers as a sizing. These mats with the cover sheet 202 are placed
20 into a mold and shaped into the desired liner. A cloth overlay may be positioned at
the vehicle interior side 204 of the FIG. 7 headliner. The vehicle exterior side 206
of the FIG. 7 headiiner typically abuts the roof of the vehicle. Although headliners
such as shown in FIG. 7 are sag, temperature and humidity resistant, and offer good
sound absorbing properties from both the exterior and interior sides of the headliner,
25 they suffer from significant drawbacks. For example, fiberg!ass liners tend to
release fiberglass dust which is irritating to individuals exposed to the dust. Also,
fiberglass is a much more expensive material on a per pound basis in comparison to
. other materials, such as wood pulp. Also, fiberglass headliners are relatively brittle,
especially a~ the densified edge section, and often break as they are flexed or bent
30 during the installation of the headliner. Broken headliners release additional
fiberglass dust and are normally discarded as scrap.
wO 93/1821B PCr/USs3/01908
- Other prior art automobile headlines have been made of corrugated
paperboard. ~;or example, as shown in FIG. 6, moving from the vehicle interior 204
to the vehicle exterior 206 sides of the headliner, one specific liner l l6 of this type
includes a core of corrugated medium 220 bounded at the interior by respective
S layers 222 of linerboard (e.g. 36 or 40 pound per l000 square feet Kraft paper,
which may be of double thiclcness at the edge of the liner for strength) 224 of a
porous foam, and 226 of cloth. Ihe corrugated medium 220 is bounded at the
ext~ior by a polyolefin layer 228 and a liner board 230 ~e.g. 36 or 40 pound per1000 square feet Kraft paper). When placed in a mold and heated, the polyolefin
- 10 layer melts and causes the liner to assume the shape of the mold when this layer
resolidifies after reduction below the melt temperatures which are present in the
mold. The exterior layer of ma~erial of this liner is relatively hard to reflect noise
from the outside environment. However, interiorly, liners of this type are
acoustically poor in comparison to fiberglass headliners. Therefore, although these
lirlers are common, they are less desirable from a noise reduction standpoint than
fibesglass liners.
Hardboard, pressed wood pulp line~ have also been used. However,
these liners are also acoustically very poor. Vehicle headliners having polyurethane
and polystyrene foam cores have also been made. However, these headliners are
believed more expensive and less sound absorbing than fiberglass headliners.
s Polystyrene foam headliners have been made by forming this material into a web,
preheating the web, and vacuum/compression molding the preheated web into a cold,~ mold wherein the material is shaped into the shape of the headliner.
Yet anothe~ pIior arti headliner is made of a resin containing polyester
~, 25 fiber core with resin saturated glass fiber surfaces. This material is much more
costly than fiberglass core headliners and tends to have a high density rough surface,
-` before being covered with cloth. Headliners of this material are believed to be less
sound absorbing than those of fiberglass.
Therefore, a need exists for improved molded liners for vehicles
produced from binder coated fibrous materials and improved processes for producing
~i such pr~ducts.
, ,,
~.
WO g3/1~218 Pcr/uS93/01908
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SUMMARY OF THE INVENTION
The present invention provides a method of making molded liners for
vehicles. These liners are typically used ~or lining doors, trunks, hoods, dashes and
roofs of vehicles. In the case of roof or headliners, it is important to provide a liner
with sufficient strength to prevent sagging during use. Also, liners which are
sufficiently ductile to prevent breakage during installation are also desirable. Also,
it is desirable to minimize the migration of fibers (dust) fsom the liners during
installation. Fibers, a substantial majority of which have a substantial majority of
their surface area continuously coated with a binder material, are delivered to a
mold. These fibers form at least one layer of the molded product together with any
fibers (e.g. synthedc fibers) and additives blended therewith. The fibers are molded
to selectively densify portions of the fibers. The fibers are bound together by the
binder matenal in ~he shape of ~he liner. Although the liners may be of a unifolm
density, such as for use as vehicle tmnk and h~od liners, the liners, especially when
used as vehicle headliners, are typically formed to have variable density areas, such
as a first region of a first density and a second region of a second density.
The fibers may be air laid or wet lat~d into the mold and heated within
the mold to the binder activating temperature. The binder material, being heat
bondable, will bind ~he fibers together into ~he desired shape. The fibers may also
be delivered to the mold in the form of a mat and similarly molded. The mat may
be wealdy bonded or l'tacked" together prior to delivery to the mold, for example
by heating the mat during its formation to cause the binder to stick the fibers
together.
The fibers, whether delivered to the mold by air-laying or in mat form,
~ 25 may be heated prior to delivery to the mold. When the fibers. are preheated, the
i mold may be at a temperature which is below the heat distortion temperature of the
binder material.
The fibers may be delivered to the mold on a cover sheet or cover
overlay. The cover overlay sheet may be of a heat bondable material so that the
fibers and the cover overlay may be heat bonded in the mold. The fibers and the
cover overlay may be heat bonded prior to deliver,v to the mold.
,f
.:
WO 93/18218 PCI~/US93J01908
f~
A backing sheet or backing overlay may also be included in a molded
liner formed in accordance with the present invention. When a backing overlay isincluded, the fibers are positioned between the cover overlay and the backing overlay
so that the fibers comprise a core therebetween. At least one of the cover and
S backing overlay sheets may be of a liquid perrneable material. Alternatively, at least
one of the cover and backing overlay sheets may be of a liquid imperrneable
material. For vehicle liners wherein noise is a problem, and therefore noise
reduction is important, the cover andtor backing overlays may be of sound absorbing
material, such as an open-celled or porous material. Also, in a preferred
- 10 construction, the cover overlay, at the vehicle interior side of a vehicle headliner is
sound absorbing so that sound can reach the core of the headliner. In addition, the
backing overlay, at the exterior vehicle side of the headliner, is of a sound reflective
material to reflect sound from the exterior of the vehicle away from the passenger
compartment of the vehicle.
The overlay sheets may each contain a resin or bindér which when
melted or cured adds rigidity to the overlay sheets.
The fibers used to make the molded l~ners are preferably discontinuous
natural fibers, such as wood pulp fibers. The fibers may be alTanged in plural layers
within the liners. One or more of the plural layers of fibers may be dyed. To resist
the effects of humidity, which can cause liners to sag, preferably at least eighty
J~ percent of all of the natural fibers included in the core of the liner have at least a
substantial majority of their surface area coated with a binder material. Most
!~ ~ preferably, virtually all of such natural fibers in the core are substantially
continuously i~oated with ~the binder material. By virtually all of the fibers being
substan~ially continuously coated, it is meant that over ninety-five percent of the
fibers have at least ninety-five percent of their surface area coated with the binder
material.
In a preferred method of the present invention, the liners have low
density areas molded to a density ranging from 0.04 g/cc to 0.1 g/cc and high
' 30 density areas ranging from 0.1 g/cc to 0.6 g/cc. Most preferably the liners have
.,
wo 93/18~18 Pcr/us~3/olgo~
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densities ranging from about O.l glcc to about 0.3 g/cc with variable density areas
being provided in the article.
Auto liners in accordance with the present invention are more ductile,
and less prone to breakage than fiberglass headliners.
As a specifically preferred embodiment, a core is provided of
substantially continuously binder coated discontinuous wood pulp fibers. A soundpassing layer, such as of an open structured nylon or polyester nonwoven material,
is coated, impregnated or saturated with a heat fusible resin, with phenolic resin
being a specific example, and positioned interiorly of the core. An inte:Iior cover
-10 layer, such as of adhesive, foam and cloth, is positioned interiorly of $he sound
passing layer. A resin (e.g. phenolic resin) impregnated, saturated or coated exterior
cover layer, such as an open structured nonwoven matenal or a line~gard is
positioned exteIiorly of the core. ~his multilayered construction is heated in a mold,
or heat~ prior to delivery to a cold mold, to bind the structure together in the form
of the headliner. The resulting headliner is more ductile than fiberglass liners and
yet absorbs sound like fiberglass liners. Surpnsingly low density structures of wood
- pulp and having a high strength which are highl~ suitable for vehicle liners are
produced in this manner. The basic weight arld density of these structures can be
substantially like these properties in fiberglass liners.
It is accordingly one object of the invention to provide improved
vehicle liners.
Another object of the invention is to provide such articles which are
strong, light weight, relatively rigid, and durable.
A further object of the present invention is to provide such articles
which resist sagging, particularly under humid and high heat condidons, such as the
interior of the passenger compartment or trunk of a vehicle.
Still another object of the present invention is to provide such ardcles
of readily available and less costly raw materials, such as using discondnuous wood
pulp fibers as a major component.
Yet another object of the present invention is to provide liners with
excellent sound absorption properties~
wo 93/1B218 Pcr~vs93/ol9o8
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The present invention relates to the above features, objects and
advantages individually as well as collectively. These and other advantages, features
and objects of the present invention will become more apparent from the description
of the preferred embodiments hereinbelow.
BBIEF DESC~IPllON QF THE DRAWINGS
In order that the present invention may be clearly understood and
readily practiced, preferred embodiments will now be described by way of exampleonly with reference to the acGompanying figures wherein:
- 10 FIG. 1 represents a schematic diagram of a preferred process used to
manu~acture the fibers used in manufacturing molded vehicle liners in accordancewith the present invention;
FIG. 2 represents;a schematic diagram of one process used for mal~ing
a molded vehicle liner from such fibers in accordance with the present inyention;
FIG. 3 represents a schematic diagram of an alternative process used
for making a molded vehicle liner in accordance with the present invention;
FIG. 4 represents a side view o~i one specific type of automobile
headliner, of a prior art shape, formed in accordance with the present invendon;FIG. 5 represents a top plan view of the molded liner of FIG. 4;
FIG. 6 is a sectional view, taken along line A-A of the materials used
in a prior art composite automobile headliner;
.. FIG. 7 is a sectional view, taken along line A-A of FIG. 5 of materials
used in another prior art composite automobile liner;
` FIG. 8 is~a sectio~al view, taken along line A-A of FIG. 5, of one
embodiment of the liner formed of materials in accordance with the present invention
wherein the molded liner has a cover sheet and a backing sheet;
FIG. 9 a sectional view, taken along line B-B of FIG. 5, of an
alternative embodiment of the molded vehicle liner formed of materials in accordance
with the present invention wherein the liner has a core of plural fiber layers;
FIG. lO is a sectional view, taken along line
d
. , .
,~
wo 93/1821~ PC~US93/01908
A-A of FIG. 5, of an altern~ive embodiment of the molded vehicle liner formed ofmaterials in accordance with the present invention;
FIGS. ll and 12 are gr~phs showing the degree of coating of well
coated arld poorly coated fibers used in a comparative example;
S FIGS. 13 and 14 are graphs (on two different scales) of the tensile
index versus densifica~ion of molded products produced from the well coated and
poorly coated fibers.
DETAILED DESCRIP rlON OF A PREFERRED EMBODIMENT
-10 The present invention provides a method for making a molded vehicle
liner. By way of exarnple only, such articles may include automobile headliners.lt will be appreciated that other three dimensional molded articles may be made using
the process of the present inventi~n.
L The molded liners are comprised af fibers which are at least partially
caated and more preferably ~rirtually all of the natural fibers included in the product
are substantially continuously coated with a binder material. The fibers are bound
together by the binder material in the shape of ~he article. A wide variety of
synthetic and/or natural ffbers may be used in fonning the article. However, it is
preferable to use discontinuous natural fibers, such as wood pulp fibers either alone
or in combination with from two to fifty percent, by weight, staple synthedc fibers.
~ ~ The term natural fibers refers to fibers which are naturally occurring, as opposed to
3 synthetic fibers. Non-cellulosic natural fibers are included, with chopped silk fibers
being one exarnple. In addition, the term natural fibers includes cellulosic fibers
such as w~od,pulpj bagasse, hempj~ jute, rice, wheat, bamboo, corn, sisal, cotton,
flax, kenaf, and the like and mixtures thereof. The term discontinuous fibers refers
to fibers of a relatively short length in comparison to continuous fibers treat~d during
an extrusion process used to produce such fibers~ The term discontinuous fibers also
includes fiber bundles. The terrn individual fibers refers to fibers that are comprised
J - substan~dally of individual separated fibers with at most only a small arnount of fiber
~- 30 bundles. Chopped or broken synthetic fibers also fall into the category of
discontinuous fibers. Although not limited to any particular type of fiber, the
~:,
... ,,,, . . ~ . . .. ~ .
WO 93~18218 PCr/US93/01908
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synthetic fibers commonly are of polyethylene, polypropylene, acrylic, polyester,
rayon and nylon. Discontinuous fibers of inorganic and organic mtaterials, including
cellulosic fibers, are also included in the tenn discontinuous fibers.
For puIposes of convenience, and not to be construed as a limitation,
5 ~he following description proceeds with reference to the treatment of individual
chemical wood pulp fibers. The treatment of individual fibers of other types andobtained by other methods~ as well as the trea~ment of fiber bundles, can be
accomplished in the same manner.
When relatively dry wood pulp fibers are being treated, that is fibers
-10 with less than about ten to twelve percent by weight mois~ure content, the lumen of
such fibers is substantially collapsed. As a result~ when binder materials, in
particular latex binder materials, are applied to these relatively dry wood pulp fibers,
penetration of the binder into theilumen is minimized. In comparison, relatively wet
fibers tend to have open lumen through which binder materials can flow into the
15 fiber in the event the fiber is immersed in the binder. Any binder that penetrates the
lumen may contribute less to the desired characteristics of the treated fiber than the
binder which is present on the surface of the fiber~ Therefore, when relatively dry
wood pulp fbers are treated, less binder material is required to obtain the sameeffect than in the case where the fibers are relatively wet and the binder penetrates
20 the lumen.
Binders used to treat the fibers broadly include substances which can
be applied in liquid form to entrained fibers during treatment. These binder
materials are preferably of the type which are capable of subsequently binding the
fibers produced by the process to one another` or to other fibers during the
25 manufacture of webs and other products using the treated fibers! Most preferably
these binders comprise organic polymer materials which may be heat fused or heatcured at elevated temperatures to bond the fibers when the fibers are used in
- manufacturing products. Also, in applications where solid particulate material is to
be adhered to the fibers by the binder, the binder must be of a type which is suitable
30 ~ this pulpose.
wo 93/1821$ Pcr/lJs93/ol9o8
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~uitable binders include polymeric materials in the fonn of aqueous
emulsions or solutions and nonaqueous solutions. To preven~ agglomeration of fibers
during the treatment process, preferably the total liquid content of the treated fibers
during treatment, including the moisture contributed by the binder together with the
Sliquid conten~ of the fibers (in the case of moisture containing fibers such as wood
pulp), must be no more than about forty-five to fifty-five percent of the total weight,
with a twenty-five to thirty-five percent moisture content being more typical.
Assuming wood pulp is used as the fiber, the moisture contributed by the wood pulp
can be higher, but is preferably less than about ten to twelve percent and more
- 10typically about six to eight percent. The remaining moisture or liquid is ~ypically
contributed by the binder. These polymer emulsions ar~ typically referred to as
"latexes.U In the present appli~ation, the term "latex" refers very broadly to any
aqueous emulsion of a polym¢ric material. The term "solutionN means binders
dissolved in w~ter or other solvents, such as acetone or toluene. Polymeric materials
1~used in binders in accordance with the present method can range from hard rigid
types to those which are soft and rubbery. Moreover, these polymers may be either
thermoplastic or thermosetting in nature. In the ~se of thermoplastic polymers, the
polymers may be a material which remains permanently ~hermoplastic.
Alternatively, such polymers may be of a type which is partially or fully cross-20linkable, with or without an external catalyst, into a thermosetting ~ype polymer.
Specific exarnples of latexes are set forth in U. S. Patent No. 5,057,166 and include,
but are not limited to: ethylene vinyl acetate, polyvinyl acetate, acrylic, polyvinyl
acetate acrylate, styrene, and polyvinyl chloride. One specifically preferred binder
material is DL2681/97i780 available from Reichhold Chemical Corporation of Dover,
3 25Delaware, and applied to the fibers in an amount which is from about seven to fifty
percent, and most preferably about thirty percent by weight to the total weight of the
fibers and the binder.
Cer~ain types of binders enhance the fire resistance of the treated
fibers, and thereby of products made from these f~bers. This is of particular benefit
, 30in products to be used in vehicles or other applications whereln fire retardancy is
.. . . . .
wo 93/1821X PCr/lJS93/01908
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extremely important. For example, polyvinyl chloride, polyvinyl dichloride,
ethylene vinyl chloride and phenolic binders are fire retardant.
Surfactants may also be included in the liquid binder as desired. Other
materials, such as colorants or dyes, may also be mixed with the liquid binder to
impart desired characteristics to the treated fibers. If a water insoluble dye is
included in the binder, the dye remains with the fibers, rather than leaching into
aqueous solutions used, for example, in wet laying applications of ~he ~reated fibers.
Also, dye would not leach from liners made from these fibers when these productsare exposed to moisture, for example to spilled beverages. Solid particulate
materials, such as pigments, may also be mixed with the binder ~or simultaneous
application with the binder. In this case, the particulate material is typically coated
with the binder rather than having exposed uncoated surfaces when adhered to thefibers as explained below. Other liquid materials may also be mixed with the binder
with the mixture still performing its function.
In addition, in accordance with the invention, one or more solid
particulate materials may be adhered to the fibers to provide desired ~unctionalcharacteristics. The solid particulate materials~are typically applied to a binder
wetted surface of the fibers and are then adhered to the fibers by the binder as the
binder dries. In this case, heat curing or heat ~using of the binder is not required to
adhe~e the particles to the fibers. Although not limited to specific materials,
examples of suitable particulate materials include pigments, such as titanium dioxide
and CaC03; fire retardant materials, such as alumina trihydrate and antimony oxide;
and hydrophobic and oleophobic materials. Thus, the solid particulate materials are
not limited to narrow categories.
FIG. 1 shows an apparatus, which is suitable for providing the binder
coated fibers used in $he molded articles of this inven~on. In this apparatus, a sheet
10 of fibrous material, such as chemical wood pulp, is unrolled from a roll 12 and
delivered to a refiberizing apparatus, such as a conventional hammermill 14. Thesheet 10 is readily converted into individual fibers 16 within the hasnmermill. 7hese
individual fibers are delivered, as by a conveyor 18, to a fiber loading zone 20 of
a fiber treatment apparatus.
;
wo 93/18218 pcr/us93/ol908
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14
Loading zone 20 forms part of a fiber treatment conduit 22. The
illustrated conduit 22 comprises a recirculating loop. A blower or fan 24 in the loop
22 is positionedi adjacent to the fiber loading zone 20. Blower 24 is capable ofmoving a gaseous medium, such as air, at a velocity and volume sufficient to entrain
the fibers which have been loaded into zone 20. The entrained fibers circulate in a
direction indicated by arrow 26 through the loop and pass through the loading zone
20 and blower 24 each time the loop is traversed.
The entrained fibers traveling in the loop pass one or nnore binder
material application zones, with one such zone being indicatedi in at 28. This binder
material application zone 28 forms a part of the conduit 22. A mechanism is
provided at the binder application zone for applying a liquid binder solution to the
entrained fibers. Plural nozzles, in this case nozzles 30, 32 and 34, may be used to
apply the liquid binder material. These nozzles produce an atomized spray or mist
of binder drops which impact and coat the fibers as the fibers pass the nozzles.Plural valves, 36, 38 and 40 are operated to control the flow of liquid
binder material to the respective nozzles 30, 32 and 34. In the illustrated
configuration, a first liquid binder material fro~ a tank or other source 42 is
delivered to the three nozzles 30, 32 and 34 when valves 36 and 38 are opened and
valve 40 is closed. As the fibers r~circula~e through the conduit 22, and each time
they pass the nozzles, an additional amount of the first liquid binder material is
applied. Different surfaces of the fibers are exposed to the nozzles 30, 32 and 34
as the fibers travel through the material application zone 28. After the desiredJ amount of the first liquid binder matenal has been applied, valve 36 is closedi. If
desired for a particular applicationi, a second liquid binder material from a tank or
i 25 other source 44 may also be applied to the fibers. With valves 38 and 40 open and
valve 36 closed, this second liquid binder material is applied to the fibers through
each of the nozzles 30, 32 and 34. In addition, the two liquid binder materials may
be simullaneously applied, at successive locations in zone 28. More than two types
- of liquid binder materials may be applied by adding additional binder sources and
suitable valving and noz~les.
.,
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WO 93/1821~ Pcr/US93JO~908
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At this poillt, a filler material such as Kaolin clay, TiO2, or ground
calcium carbonate particles can be introduced to the system so that they attach to the
coated fiber surface. As a result, when used in producing a molded product, the
product will have a smoother, more uniform surface.
The fibers may be retained in the loop until they have dried. The
recirculation of the fibers may then be stopped and the fibers removed at the loading
zone 20, which then functions as a fiber removal location. However, as shown in
FIG. 1, a cyclone separator 46 is selectively connected by a conduit section 48 and
a gate valve 50 to the conduit 22. At the same time a valve 52 is opened to allow
air to enter the loop 22 to compensate for air exiting through the separaitor 46. With
the separator in the loop, the entrained fibers are collected in the sepa~ator and then
removed from the separator at a fiber removal outlet 54.
As a result, treatedifibers are produced, a substantial majority of which
s~. have a substantial majority of their surfare area continuously coated with a binder,
with optional particles being adhered to the fibers by the binder. Most preferably,
a substantial majority of the fibers, and more typically virtually all (in excess of
ninety-five percent) of the fibers, have a substanti~ly continuous coating of a binder
material. At least a substantial majority (seventy percent) of the buLk treated fibers
^ - are unbonded so that they may be readily blended with other fibers and/or processed
into products (such as by conventional air laying techniques). By using a heat
curable material as the binder, the fibers may be subsequently heated to cure the
- binder and fuse them together. The fibers may also be combined with other
nontreated fibers and molded into a vehicle liner as explained below.
The binder provides a coating over a substantial majority of the surface
area, meaning at l ast about eighty percent of the surface area of the individual
fibers. More typically, the fibers are substantially continuously coated with a
-~ continuous binder coating over substantially the entire surface (at least about
, ninety-five percent of the surface area) of the individual fibers. Also, in many cases
virtually all of the surface area of the individual fibers is con~nuously coated,
meaning that the surface coating is an unbroken and void free, or at the most has a
~ few voids of less than the diameter of a fiber.
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16
Also, binder may be applied so that a substantial majority of the fibers,
that is a$ least eighty percent of the fibers: ~a) have a substantial majority of their
surface area coated; (b) a substantially continuous coating; or (c) have virtually ~heir
entire surface continuously coated. The remaining fibers typically have varying
5 degrees of coating ranging from discrete patches of coating to a major portion of
their surface (fifty percent or more) being continuously coated. Variations occur due
to the ~pe of binder being applied, the loading of the binder, and the fact that not
all of the fibers receive the complete treatment. Also, substantially all (at least about
ninety to ninety-five percent) of the individual fibers and fiber bundles being treated
10 in bulk have been produced with coatings falling into the above three categories. Of
course, for many applications it is desirable that substantially all of the fibers of the
buLk fibers being produced have a substantially continuous coating or virtually their
entire surface continuously coat~d because, in this case, the characteristics of the
binder (as opposed to exposed fiber surfaces) controls the properties of the fibers.
15 For example, wood pulp fibers coated with a hydrophobic binder will not pick up
moisture from the air, which ~ould otherwise cause a liner of these fibers to sag.
It has also been found that binder loading leve~s of approximately about seven
percent of the combined weight of the binder and fiber results in fibers a substantial
majority of which, and more typically substantially all of which, have a substantially
20 continuous coating.
In addition, the continuous coating is extremely uniform over the
coated surface of the fibers and fiber bundles. For instance, a fiber coated with
twenty percent by weight binder to the combined weight of the binder and fibers of
a binder such as polyethylene (Primacor), forms a coating which is about 0.5
25 microns thick, plus or minus about 0.25 micron. If the coating add-on were forty
percent by weight of this binder to the weight of the binder and fibers, then the
coadng thickness would be about l.0 micron, plus or minus 0.25 micron.
The fibers, prior to molding, may have substantial amounts of binder
material, yet still comprise individualized substantially continuously coated fibers.
30 It has been found that the binder material must be included in an amount of at least
about seven percent of the combined dry weight of the binder material and fibers in
wc) 93/1~218 Pcr/us93/01908
'~131~6~
order to produce a substantially continuous binder coating on the fibers. With asubstantially continuous coating, little or no surface area of the fibers is exposed and
the desired characteristics added to the fibers by the binder material are not nullified
or significantly altered by uncoated areas of the fiber. With a binder level of at least
S about ten percent of the combined dry weight of the binder material and fibers, the
coated fibers are capable of bonding relatively stsongly to one another when hea~
fused. In addition, substantially unbonded individualized fibers with binder levels
of thirty percent to fifty percent and higher, such as above ninety percent and with
no maximum limit yet being determined, can be produced. Also, high binder levels~ 10 are preferably used to maximize the bond strength and to adhere solid particulate
materials to the fibers. For some particles, however, lower binder concentrations
may be used to reduce the possibility of the binder coating the particles and
interfering with the functionalities.
An optional means for heating the binder coated fibers may be included
in conduit 22. For exarnple, heated air may be blended with the air flowing through
the conduit. Similarly, a heater 56 may be included in conduit 22 for heating the
fibers. The dried fibers from outlet S4 of the cy~one separator 46 may be deposited
onto a conveyer 58. These fibers may then be heated in a therrnobonder 60 to form
a preheated fiber mat 62.
~,, 20 Pibers may also be used as the wet laid sheet or otherwise wet laid,
for example directly into molding equipment.
The resulting fibers are thereby coated with a sufficient amount of
binder material to form a substandally continuous coadng of binder material on the
fibers. Furtherrnore, substaLndally unbonded individualized fibers may be produced
~5 in this manner. By substandally individualized, it is meant that ninety-five percent
or more of the fibers are unbonded. Also, a substantial majority of the individual
fibers, meaning seventy percent or more, may also be produced. By deposidng the
fibers wet with binder onto a belt or other conveyer, the fibers tend to stick together
somewhat as the binder dries. This increases the handleability of the fibers in web
form when used, for example when delivered in web form to a mold. Also the
, fibers may be heated in web form to above the heat distortion temperatures of the
-
~.
wo 93/18218 Pc~r/us93/01908
~,
~l~i4~
18
binder (that is, the temperature at which the binder begins to flow and become tacky)
to cause some adhesion of the fibers prior to molding. Ihis also incr~ases the
handleability of the webs. If the binder is a thermoset binder, this preliminaryheating is preferably at a temperature below that which causes the binder to set.
S An appaIatus for making the articles is shown in FIG. 2. The rnat 62
of binder coated fibers is deposited on conveyor 64 and pr~cessed through
thermobonder 65 along with a cover sheet material 66 and backing sheet material 68.
The fibers of mat 62 thus comprise a core between cover sheet 66 and backing sheet
68, best seen in FIGS. S and 6. The binder matenal on the fibers of mat 62 and the
- 10 cover and backing sheets, 66 and 68, may each be of a heat bondable material. Por
example, the cover and bacldng layers may be of rayon, polyester~ nylon, or
polypropylene or blends. A specific prefelTed example of a liquid impermeable
material for the cover and/or backing layer is polyethylene from Dow Chemical
Corp. A specific preferred example of a liquid permeable material for the cover
and/or bacldng layer is rayon/polyester. These materials may be varied for
production applications.
Following heating in thermobonder.~65, the fibers will bind together
and the cover sheet 66 and backing sheet 68 will be heat bonded to the core fi~ers.
Alternatively, the cover and backing sheets may be adhesively secured to the core
with or without thermobonding. A sui~able adhesive is Zero Pack from
H. B. Fuller which, for example, could be sprayed onto the surface of the core pAor
to positioning the cover and backing layers.
At least one of the cover sheet 66 and backing sheet 68 may be of a
liquid permeable or of a~liq~id impermeable material. Suitable liquid permeable
materials include, but are not limited to, nylon, polyester, ~ayon polypropylene and
~7 blends thereof. Additional examples of suitable liquid impermeable materials include
films of polyethylene, polypropylene and polyester and blends thereof along with. nylon and polyvinyl chloride films.
In FIG. 2, the mat 62, cover sheet 66 and backing sheet 68 are heated
in thermobonder 65 prior to delivery to mold 69. Mold 69 may then be at a
;1 temperatllre below the heat distortion temperature of the binder material. Again, the
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~131462
19
heat distortion temperature is the temperature at which the binder mateAal will
soften. It will be appreciated that the binder material must be h ated to at or above
the heat distortion temperature to bind the fibers together. This temperature isreached in thermobonder 65 (or in thermobonder 60). When reached in
S thermobonder 65, the fibers and cover and backing sheets are already bonded prior
to delivery to mold 69. Therefore, mold 69 need not be heated to the heat distortion
temperature to accomplish binding. Mold 69 is therefore not required to soften the
binder material. A mold which is at a temperature below the hea~ distortion
temperature is sometimes referred to herein as a "cold" mold. The temperature
-10 difference between the heated fibers and the cold mold causes a shock or quenching
of the fibers after they have been formed into the desired shape established by the
mold. The cold shock from $he temperature differential causes the fibers to harden
more quicldy in the mold.
It will be appreciated that the fibers and cover and backing sheets need
not be heated prior to delivery to the mold. The mold may be heated to at or above
~he heat distortion temperature to bind the fibers and cover and backing sheets. This
temperature is preferably below the temperature~t which charring of the fibers
would occur.
A specific example~ assuming the cover layer is rayon, the baclcing
layer is polypropylene, and the binder is Synthemur 40-800 ~from Reichhold
Chen~ical Company) at least partially coated onto wood pulp fibers, the
thennobonder 66 beats the combined core cover and backing layers to about 120-
130C. While still above about 100C, this heated material is delivered to a mold
at 25-30 C. T;he mold is typically closed for 0.5-2 minutes with a pressure of from
about 100 to about 1000 psi being applied to the materials.
The mold 69 may be of any type suitable for producing an article
having a first region of a first density and a second region of a second density.
Molded vehicle liners of the invention and other articles frequently contain areas of
variable density. As a result, the articles have variable strength and absorption
characteristics within the article as will be described hereinbelow. In a preferred
embodiment, the article is molded to a density of from about 0.04 g/cc to about 0.6
Wo ~3/18~18 Pcr/us93/01908
~13:~462 20
g/cc-with areas of varying densities within the article. These densities are like those
found in commercial fiberglass headliners.
The molded liner is removed from the mold onto conYeyor 70. The
sheets containing ~he molded articles would pass typically through a cutting device
72 such as a die or water knife. The molded articles may thus be forrned in a
con~nuous sheet. Cutting device 72 cuts each individual molded article out from ~he
process sheet.
An alternative process in accordance with the present invention is
shown in FIG. 3. In this case, fibers substantially continuously coated with binder
- 10 material are delivered to a conventional air laying device 74 (such a~s a Danweb
Model P75 Airlayer from Danweb Company of Denmark directly from the cyclone
separator 46 shown in FIG. 1 ~ia the line S4. These treated fibers may also be
bagged or otherwise collected from the apparatus and then subsequently used in the
production of the molded liners. Treated fibers ~nay be mixed with untreated fibers
76 and/or staple fibers 78 (shown in bags in this figure) which are broken apart using
a hammermill or other conventional means (not shown). Untreated fibers are fibers
which are not coated or only partially coated with,~inder material. Staple fibers are
fibers which are of a longer length than the treated fibers, such as rayon fibers,
polyester, nylon, and polypropylene. Staple fibers and/or untreated fibers may be
added to the treated fibers to strengthen and reinforce the molded product.
Typically, staple fibers of from two to fifty percent by weight are added to the core
of treated fibers.
c The fibers may be mixed together in air laying device 74 and delivered
in a mixture to the mold 76~ This mixture may be heated pnor to delivery to the
'5 25 mold, as by a thermobonder 66 descAbed above, and/or heated in the mold to
activate the binder. Alternatively, each type of fiber may be delivered separately to
~he mold, forming a molded article or core thereof comprised of plural layers of,3
! different types of fibers. A molded liner 116 with a core comprised of plural layers
of fibers is shown in FIG. 9. Por example, the top layer 62' of the core may
30 comprise one hundred percent substantially continuously coated fibers, and the lower
` layer 62 may comprise a fifty/fifty mix of substantially continuously coated fibers
WO 93/18218 ~ PCI/U593/0]908
and staple fibers. Other layers may also be included. Again, without limiting the
myriad of options, another specific example is to provide a plural layer variable
binder concentr~tion containing molded product. For example, the top twenty
percent of the fibers in the product may be substantially continuously coated fibers
S with a binder concentration of fifty percent by weight to the combined weight of the
binder and fiber. In addition, the bnttom eighty percent of the fibers may comprise
a blend of twenty-five percent substantially continuously coated fibers, coated with
binder in the amount of about twenty to about twenty-five percent of binder to weight
of binder and fibers and seventy-five percent untreated or staple fibers. When
-10 molded under high pressure (2,000 psi), the top layer in this product forms a liquid
imperrneable surface and the bottom layer includes enough binder to provide stiffness
to the molded product. Also, the-heavier binder concentration in the top llayer would
serve to bind the core to an overlying cover sheet.
A cover or overlay sheet 80 may be delivered to the air laying device
15 74. As described above, this cover sheet may be of a liquid perrneable or a liquid
impermeable material. Although not shown in FIG. 3, the molded product may also
include a backing sheet as previously described (e~s~. delivered to the mold with the
fibers sandwiched between the cover and backing layers). These overlay sheets may
include a resin or other binder to rigidify the overlay sheets. For example, curable
20 resins ~r binders which melt when heated may be used. The fibers are delivered to
the mold 76 on cover sheet 80. Unless the fibers are preheated, the mold 76 is
heated to the heat distortion temperature of the heat bondable binder material. The
fibas are heated within mold 76, binding the fibers together. Cover sheet 80 maybe heat bondable and in this case, is bound to the fibers in heated mold 76. Mold
25 76 is configured to provide a molded article of the desired shape and density.
- It will be appreciated by those of ordinary skill in the art that air laid
fibers may be heated prior to delivery to the mold by, for example, passing the fibers
through a hot air stream. Preheating will cause the fibers to bind together prior to
delivery to the mold. The mold m~y then be at temperature which is less than the30 heat distortion temperature of the binder to provide a cold mold as previously
described.
i
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~131462
22
One specific example of a molded vehicle liner formed in accordance
with the present invention is an automobile headliner 116 of the type shown in FIGS.
4 and 5. The headliner is formed by molding binder coated fibers, preferably wood
pulp fibers into a desired shape. The headliner preferably consists entirely of, or of
at least one layer of, fibers a substantial majority of which have a substantialmajority of their surface area continuously coated with a binder. However, such
fibers may be blended with untreated or only partially treated fibers. Most
preferably, virtually all of the natural fibers included in the liner are substantially
continuously coated with a binder material. The headliner preferably includes a
-10 nonwoven or fabric cover sheet. Both the fibers and the cover sheet may be dyed
to a desired color. It is preferable to use plural layers of fibers, at least one of
which is dyed. Synthetic fibers may be added to the natural fibers as reinforcing
fibers. Headliners of this type;are preferably provided with areas of differing
densities. For example, for cushioning purposes, the central portion 117 of $he
headliner may be of a density of from about .04 g/cc to about .1 g/cc, and most
,~ preferably about .06 g/cc. For added strength, the side portions 119 of the headliner
may be of a higher density, such as from about . lS g/cc to about .6 g/cc, and most
preferably about .3 g/cc. Also, areas bordering openings in the headliner may also
be densified, for example, $o the same degree as the side portions, to add strength.
Sag, due to gravity, is a factor that rnust be resisted in a vehicle
headliner application. In this case, preferably an overlay is provided at each of the
two major surfaces of the core, the core being forrned of fibers as explained above.
The overlay at the interior (vehicle) side of the headliner 130 (FIG. 10)
most preferably allows sound~ to pass through it and into the sound absorbing core
62. Preferably, the material does not increase the sound energy which is reflected
from the undersurface of the headliner. That is, the material must not significantly
change the flow resistivity of the structure. A nonwoven synthetic material or scrim
with an open or porous structure, such as a spunbonded material, containing an
applied rigidifying resin, is a specifically preferred material for the interior overlay.
The resin may be sprayed, dipped, or otherwise applied to the interior overlay. A
phenolic resin is a preferred exarnple. A phenolic saturated polyester nonwoven is
Wo 93~8218 Pcr/us93/01~08
31 ~1 6~
a specifically preferred example9- with a Dynofiber~ web being one such material.
This material is of a 29 gm per square meter polyester nonwoven (Remayn') saturated
with 29 gm resin per square meter and is available from Dyno Overlays, Inc. of
Tacoma, Washington. Polyester nonwovens are preferred because they are more
S ductile than glass fibers. Other resins, resin loadings, and resin systems may be
used, such as ~wo layer structure having a scrim or nonwoven as one layer and
another layer which melts and bonds at the mold temperatures during formation ofthe liner. Again, the interior overlay for a headliner must have the desired sound
penetration characteristics, when sound reduction is important in an application, as
-10 otherwise the structure will not have the desired sound absorbing properties
characterized by fiberglass headliners. For example, resin impregnated 32 and 40lb. per }000 square feet Kraft paper is too sound reflective for the interior overlay
when sound reduction is important.
The exterior overlay 132 (FIG. 10) at the exterior or roof side of the
headliner may be of the same material as tho interior overlay, such as a phenolic
r~ resin saturated polyester nonwoven sheet as described above. However, any resin
coated or saturated material may be used, such as~ resin coated or saturated Kraft
liner because sound penetration is not as impoItant at this location. That is, a sound
reflective surface at the exterior overlay is often beneficial as the exterior overlay
20 then assists in reflecting exterior road noise away from ~he interior of the vehicle.
Y As also shown in FIG. 10, the interior surface of the interior overlay
130 may be covered with a conventional cover stock, such as a multilayered Guilford
J cloth, as described below.
As a more specific example, NB316 Southern Pine pulp from
25 Weyerhaeuser company was coated with DL 2860 Styrene Butadiene Acrylonitrile
from Reichold Chemical Company to provide fibers with binder at a level of binder
which is thirty percent solids to the total weight of the binder solids and fibers.
Although not specifically tested in this example, based upon our expeAence in fiber
treatment, over ninety percent of these fibers would be substantially continuously
30 coated. The fibers were then felted on an air laying system and thermobonded below
the crosslinking temperature of the binder to soften the binder and tack the fibers
.,
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W093/18218 P~/USg3/01908
i~ 3~
24
together to aid subsequent handling and processing. 5peeifically, ~he fibers were
placed in a through air thermobonder at 120C for thirty seconds and the resulting
web had a basis weight of about 800 grams per square meter and was densified by
pressing to from 0.02 g/cc to O.OS g/ce. This web constituted a core for a vehicle
S headliner.
Calendar rolls may be used for this pressing operation. The
thermobonded mat was then heated and compressed in a mold at 177C for two
minutes to achieve crosslinking of ~he binder and the desired densification of the mat.
The pressed panel was then removed frorn the press. The pressed panel had areas
- 10 of differing density. The low density areas ranged from 0.04 g/cc to 0.1 g/cc and
the high density areas ranged from 0.1 g/cc to 0.6 g/cc. The densities could be
made higher or lower, if desired.- For example, densities of up to about 1.2 g/cc or
higher may be achieved. The ccre panel was overlayed (sandwiched between) by
cover and backing overlay sheets of resin saturated polyester nonwoven (DynofibeP')
15 prior to the pressing operation. A cover sheet was then positioned on the inteAor
side of the overlayed core and the assembled panel was then repressed at a
temperature of 177C for thirty seconds, causing ~ layer of the overlaying sheets to
melt and bond to the core panel. A specifically preferred covering material is
Guilford cloth, a tri-layered sheet material from Guilford Mills, Inc. of Greensboro,
20 North Carolina. Guilford cloth has a cloth face, a thin foam intermediate layer and
an adhesive back which adheres to the interior overlay during this repressing step.
A two-step process is used in this case because the cover sheet would degrade ifsubjected to the temperature for the time required to cure the resin in the overlay
sheets. Other resins and oover materials could be simultaneously pressed in a single
25 step.
Again, for better acoustic suppression properties, one or both of the
overlay sheets, the interior overlay sheets, is made of a material which allows sound
to readily pass to the core.
To compare the ductility of headliners of the present invention and
30 fiberglass headliners, two specific headliner stmctures, Structure "A" and Structure
"B" were compared. Structure "A" was the core structure described above with the
r
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wo 93/18218 pcr/uss3/o19o8
~13 i 462
above described exterior and interior overlays of phenolic saturated polyester
nonwoven material. Structure "B" was a commercially available fiberglass headliner
~with its cloth cover removed) formed of a resin impregnated fiberglass mat and an
interior overlay of a hydroentangled nonwoven material.
S ~or samples of Structure "A" and Structure "B" at the same density,
tests (pursuant to ASTM D-1037) have confirmed that Structure "A" is significantly
more ductile than Structure "Bn. The difference would be even more pronounced
if the overlay sheets of Structure "A" are eliminated. The densities of Structures
"A" and "B" that were tested ranged from about 0.12 gm/cm3 to about 0. l5 gm/cm3.
-10 Comparisons were made between samples of the two structures at the same density.
It is expected that at higher densities, such as at the edge of a
headliner, the differences in ducti~ity between Structures "A" and "B" would be even
more pronounced. That is, Structure "A" is more ductile than Structure "B" as
- . evidenced by Structure "A" following a stress,~strain curve that would have a higher
energy to failure as defined by the area under the stress/strain curve than the case
for Structure "Bn.
f When the stress/strain curves were~compared, Structure "A" was
uniformly more ductile than S~ucture "B" for each of the tests conducted to date.
'Jf As another specific comparative example, fibers were produced
20 utilizing thirty percent by weigh~ of latex solids (styrene-butadiene latex, 97-915
available from Reichhold Chemical Company, of Research Triangle, North Carolina), to NB 316 wood pulp available from Weyerhaeuser Company to produce well-coated
fibers. Examples of these fibers were tested and confirmed that eighty percent of the
fibers had at least ninety percent of their surface area continuously coated with the
25 latex binder material. More specifically, these tests also indicated that about eighty-
-, seven percent of the fibers had at least eighty percent of their surface area
' substantially continuously coated with binder.
In addition, poorly coated fibers were produced by adding thir~
j~ percent by weight, 97-910 latex solids to NB316 fluff pulp in a manner that limited
!,~, 30 the surface area of the fibers that were coated. Only about ten percent of the fibers
~? had about eighty percent of their surface area continuously coated with binder. In
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4~
26
addi~ion, eighty percent of the fibers tested had from virtually no binder present to
about forty-five percent of their surface area substantially continuously coated with
binder.
Air laid pads, six inches in diameter, were formed in the laboratory
S of each of these mateAals. These air laid pads were ~hrough-air thermobonded at
120C. for one minute. These pads were then pressed at 170C. for two minutes
to a variety of densities, ranging from 0.08 g/cc to 0.98 g/cc. The resulting
densified and bonded structures were then tested for tensile index strengths in
accordance with ASTM D648.
- 10 The results are set forth in Table I, below.
- TABLE I
Tensile Index vs l~ensitv of
Well Coaeed and Poorly (:~oated
30% Latex on Pulp Fibers
Density Tensile Index
g~ ~Im~
Well coated fibers 0.945 50.48
0.423 18.92
0.265 9.75
' 0.091 1.88
Poorly coated fibers0.980 15.03
0.354 2.23
0.262 1.22
0.083 0.20
.. . . . ..
As confirmed by this table, the use of fibers in vehicle liner products,
a substantial majoAty of which are substantially continuously cnated with binder,
results in much stronger molded products. FIGS. 11-14 graphically illustrate these
test results and set forth the best fit curve for these data points for molded products
.~ 35 produced ~rom the well coated and poorly coated fibers. Surprisin~ly, the use of
well coated fibers allows the production of an extremely strong molded product, even
at low densities.
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WO93/lg218 P~r/uS93/~)1908
2131'~fi2
27
While the present invention has been desc~ibed in connection wi~
preferred embodiments, it will be understood that modifications and variations
apparent to ~ose of ordinary skill in the art are within the scope of the present
invention.
1, .
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