Note: Descriptions are shown in the official language in which they were submitted.
i'74Z
-- 1 --
SELF-SUPPORTING MOLDABLE FIBER MAT
~ND PROCESS FOR PRODUCING SAME
TECHNICAL FIELD
. . _
The invention relates to a moldabIe fiber mat structure, to
processes for forming fiber mats which subsequently can be shaped or
molded into a variety of fiberboard products, and to processes for
preparing cellulosic fibers which are used to form fiber mats. A fiber
mat such as this is usually composed of a mixture of comminuted
cellulosic fibers and binder which has been compressed into a mat having
the desired thickness and mechanical properties. Such fiber mats are
widely used in fabricating a variety of articles and products, including
automotive parts, such as dashboards and interior door pane]s, and
products made of flat hardboard, medium density fiberboard, cardboard
(such as 9 point), and Kraft linerboard.
BACKGROUND ART
Many different processes have been and are now in use for
~orming flat or molded fiberboard products. Generally speaking, in the
manufacture of fiberboard, ligno-cellulosic material such as wood, corn
stalks, sugar cane waste (bagasse), straw and the like, and other materials
such as waste paper and cardboard, are first reduced to their basic
comminuted celluiosic fiber form in hammermills or refiners. The fibers
are treated with the reguired resins and then air layed or felted into
a predetermined shape or mat which then is consol~dated to the desired
density by the application of heat and pressure. In this procedure, the
quality and properties of the fiber mat produced from a given ligno-
cellulosic material are most strongly determined by the physical and
chemical treatment to which the ligno-cellulose fibers have been
~ !
11717~2
-- 2 --
ubjected. These are the factors that the present invention addresses.
Some of the known fiberboard forming processes are referred
to as "wet" slurry processes, wherein a slurry having a very small
cellulosic solids constituent is applied directly to a porous chaffing
surface until a sufficient thickness is built up to form the desired
article. Basic examples of these "wet" processes are the old "Chapman
Batch Process" which is obsolete and probably no longer in use, and the
"Fibrit" process, which was developed in Germany.
In the Fibrit process, debarked wood is first cut to chip
size to facilitate handling with material handling equipment. The chips
are further reduced by mechanical grinding aided by saturated steam in
a defibrator unit. The resultant coarse pulp passes through a cyclone
that separates the steam. The next step involves a hydropulper where
small amounts of cellulose fiber and ~ibrit scrap are added. Here the
pulp is broken down to a uniform fiber length.
The mixture is then diluted to 5% consistency and stored
in large tanks prior to pumping the resultant fluid through a secondary
refiner which processes it to the correct molding conditions. At this
point resins and water are added to reduce the consistency further.
The next stage of the process is a 3-stage molding sequence
which starts by making a "felt" or pre-form. The diluted pulp mix is
pumped into a closed, mold-like container that has on its surface a
perforated screen shaped to the final component form. As water is
forced through the perforations the individual fibers in the suspension
interlock and build up to the required primary thickness. Pulp flow
stops when this point is reached, and compressed air is introduced which
further reduces the water content and densifies the mat.
The felt is now picked up by a rigid male tool which
transfers it to a wet pressing station. Here the female tool in the
form of the final component is a rubber diaphram that is expanded by
fluid pressure to apply a uniform squeezing action over the entire working
surface. This extracts most of the remaining liquid from the felt and
at the same time reduces its thickness by about 50%. The felt is now
in a "handleable" state. The last operation involves hot pressing with
a matched pair of oil-heated steel dies. There the pre-formed work
!
117~7~
-- 3 --
piece is reduced to its final thickness and density under heat and
pressure.
In contrast to the above described "wet" process,
Weyerhaeuser had developed a "dry" process called "Press-Tock", which
is described in U.S. Patent Nos. 3,230,287 and 3,261,898. In such a
process the fiber-resin mixture is dried under carefully controlled
conditions to form a pre-form or mat which later can be molded to
form an article of desired shape.
A known fiberboard forming process which is closely related
to that of the invention is disclosed in U.S. Patent No. 3,741,863. In
this process ligno-cellulosic material in the form of wood chips is
pulverized in a hammermill and then dried to remove excess moisture.
The material then is heated in the presence of steam and is abraded
under steam pressure to raise its temperture sufficiently to rupture the
hydrogen bonds in the fibers and cause softening of the lignin present
in the material, thereby separating the fibers from one another. After
separating the fibers from the steam, a resin binder is mixed with the
fibers. The mixture is then formed into a mat which is compressed
under heat and pressure to form a fiberboard product.
In connection with the above described process it was
believed that the temperature of the fibers undergoing abrasion should
not be permitted to exceed approximately 500 F. for fear that the
fibers would be scorched and darkened or otherwi~e damaged. Quite
unexpectedly, however, it has been discovered in connection with the
process of the invention that temperatures on the order of 500 to
700F. do not have such a detrimental effect on the fibers, and in fact
actually contribute to producing a superior product because the lignin
present in the fibers is actually melted and redistributed over the surface
of the fibers. These high temperatures are attained according to the
invention by using steam at a pressure of 50 to 150 p.s.i.g. in the
defibering or refining stage. The steam and the heat of attrition
contribute to raise the temperature of the fibers to 500 to 700 F.
range, also causing the steam to become superheated. This is
accomplished with a relatively small expenditure of energy because of
the fact that the material is first dried before being heated. The
117i7
-- 4 --
energy normally expended to generate steam in wet chips is now expended
to superheat the steam atmosphere.
It also has been found, quite surprisingly, that superior fiber
mat characteristics can be obtained by mixing the refined fibers with
a binder in a batch blender, instead of in a conventionally used continuous
blender. It also has been discovered, quite surprisingly, that a superior
fiberboard product could be obtained by mixing relatively wet refined
fibers (solids content of 90 to 80 percent) with a very small amount
of dry powdered binder. This represents a three to twenty-five fold
reduction in the amount of binder needed as compared to so-called wet
processes. Also unexpected is the successful use of textile or organic
fibers in the process according to the invention, wherein a small
percentage of relatively long textile fibers, or long organic fibers, are
intermixed with the cellulosic fibers and the binder prior to formation
of the fiber mat.
Most fiber mat preforms produced by known processes
present difficult handling problems due to their relatively low tensile
strength. These prior art mats therefore require special handling
equipment to transfer them without breakage from the mat forming
machines to the presses which press and heat the mats to form rigid
fiberboard end products. It has been found, quite surprisingly, that
superior fiber mat characteristics can be obtained by compacting the
fiber web longitudinally (that is, in the direction of its travel) while
compressing it to reduce its thickness. Such compaction results in much
more intimate fiber-to-fiber contact. In a preferred embodiment this
is accomplished by passing the web through a special two-roll compactor
having web retarding surfaces. Conventionally a single-roll compactor
similar to this piece of equipment is used to crepe much thinner web
products such as paper and textiles. In using this machine in the process
of the invention, however, a creping action does not occur. Rather, a
retarding of the web parallel to the flow of the web occurs. This
retarding effect tends to densify the web, reduce its thickness and
surprisingly makes the final web structure extremely flexible and gives
it a high mechanical and tensile strength, enabling it to be wound into
rolls.
117~7~
DISCLOSURE OF THE INVENTION
In accordance with the present invention, a method of
producing cellulosic fibers, suitable for use in moldable fiber mats, from
small pieces of ligno-cellulosic material comprises the steps of drying
the small pieces to a 75 to 85 percent solids content to remove excess
moisture therefrom, heating the dried pieces with a non-flammable
heating medium, and abrading the pieces in the heating medium to
elevate the temperature of the pieces to approximately 500 to 700 F.
to melt to lignin in the pieces, rupture the lignin bonds in the cellulosic
fibers and redistribute the lignin on the surface of the fibers.
The invention also encompasses a method of making a fiber
mat from small pieces of ligno-cellulosic material which comprises the
additional steps of separating the fibers from the heating medium,
intermixing a binder with the fibers, forming the mixed fibers and binder
into a mat, and pressing the fibers and binder in the mat together.
The invention further comprises a method of making a fiber
mat from small pieces of ligno cellulosic material having a 75 to 85
percent solids content comprising the steps of heating the pieces with
a non-Mammable heating medium, abrading the pieces in the heating
medium to elevate the temperature of the pieces sufficiently to melt
the lignin in the pieces, rupture the lignin bonds in the cellulosic fibers
and redistribute the lignin on the surface of the fibers, separating the
fibers from the heating medium, intermixing a measured amount of
binder into a discrete batch of fibers, forming the mixed batch of fibers
and binder into a mat and pressing the fibers and binder in the mat
together.
The invention also includes a method of making a fiber
mat from small pieces of ligno-cellulosic material having a 75 to 85
percent sdids content, comprising the steps of heating the pieces with
a non-flammable heating medium, abrading the pieces in the heating
medium to elevate the temperature of the pieces sufficiently to rF elt
the lignin in the pieces, rupture the lignin bonds in the cellulosic fibers
and redistribute the lignin on the surface of the fibers, separating the
fibers from the heating medium, the separated fibers having an 80 to
90 precent solids content, intermixing 1 to 5 percent dry binder with
1~ ~717~
-- 6
the fibers, forming the mixed fibers and binder into a
mat and pressing the fibers and binder in the mat together.
The invention also comprises a method of making
a fiber mat from small pieces of ligno-cellulosic material
having a 75 to 85 percent solids content, comprising the
steps of heating the pieces with a non-flammable heating
medium, abrading the pieces in the heating medium to
elevate the temperature of the pieces sufficiently to
melt the lignin in the pieces, rupture the lignin bonds
in the cellulosic fibers and redistribute the lignin on
the surface of the fibers, separating the fibers from
the heating medium, intermixing a binder with the fibers,
forming the mixed fibers and binder into a mat, and
retarding longitudinal movement of the pressed mat to
reduce its length and increase its density.
Other aspects of this invention are as follows:
A method of making a formable, superior strength,
self-supporting and easily handled fiber mat preform
of substantially uniform thickness which is an intermediate
preform formable by the application of heat and pressure
into a superior strength, rigid fiberboard end product,
comprising the steps of:
intermixing fibers with a small percentage
of binder by dry weight of fibers;
forming the mixture of fibers and binder into
a mat; and
moving the mat longitudinally through pressing
and retarding means to reduce the thickness of the mat
substantially uniformly by at least 60 percent, and to
compress the mat lengthwise by at least 10 percent,
thereby increasing the density of the mat by at least
175 percent.
A formable, superior strength, self-supporting
and easily handled fiber mat of substantially uniform
thickness which is an intermediate preform formable by
D
11 71~7'~
- 6a -
the application of heat and pressure into a superior
strength, rigid fiberboard end product, the mat comprising
a weblike mixture of fibers and a small percentage of
binder by dry weight of fibers, which has been compressed
in the direction of its thickness by at least 60 percent
and in the direction of its length by at least 10 percent
to increase its density by at least 175 percent.
Finally, the invention comprises fiber mats produced
by the above described methods, and fiberboard products
produced by compressing and heating these mats.
BRIEF DESCRIPTION OF THE DRAWINGS
The details of the invention will be described
in connection with the accompanying drawings, in which
Figures la through ld, and 2a and 2b are schematic rep-
resentations of various portions of the process, the figures
being interrated as indicated therein, and Figure 3 is
a schematic illustration of a compactor used in connection
with the process~
BEST MODE FOR CARRYING OUT THE INVENTION
Referring to Figure la, the process is designed
to utilize ligno-cellulosic material from any available
source, such as green logs delivered to a log deck 2,
or chips from a local mill 4. Logs are fed through a
debarker 6, the bark removed and stored in a fuel silo
8 (Figure lb). The debarked logs are then reduced to
chips in a chipper 10. Metering bin 12 combines these
chips with the chips delivered from mill 4.
Referring to Figure lb, a feeder and blower 14
delivers the chips selectively to fuel silo 8 through
a collector filter 16, to a chip silo 18 for further pro-
cessing through a collector 20, or to yard storage 22.
Chips delivered from chip silo 18 are reduced in size
in hog 24 to a maximum 3/4 inch mesh. Magnet 26 extxacts
ferrous metal pieces.
T~
11'7~'7'~'
-- 7 --
The chips then pass into dryer surge bin 28, thence to dryer 30 (Figure
lc).
Dryer 30 produces hot gases by wood combustion in burner
32. The fuel for this burner is the chips or bark stored in fuel silo
8 delivered through metering bin 34 (Figure lb). This fuel may also be
used to power one or more wood burning boilers 36.
In dryer 30 the solids content of the chips is increased
from 50 percent to 75 to 85 percent. The chips are then blown by
fan 38 into a cyclone separator 40 which separates air and gases from
the chips. After passing through a rotary air lock 42 the chips are
again exposed to a magnet 44 to extract any ferrous metal which may
have adhered to the moist chips prior to drying. The dried chips are
then screened at 46, the unacceptably small chips (those smaller than
1/8" diameter) being returned to fuel silo 8 through collector filter 16
by fan 48. Small fan 50 propels the chips through collector filter 52
and rotary air lock 54 into metering bin 56 (Figure ld).
Referring to Figure ld, items 61 through 68 all relate to
the refining stage of the process. Chips flow from hopper 61 through
refiner preheater 62 into preheater 65. A proper proportion of water
from pump 63 is mixed with the chips through ratio meter 64 as the
chips enter preheater 65. This added water cools the chips and adjusts
their moisture content to an appropriate level. Feed screw 66 delivers
the chips to pressurized refiner 67. The chips are exposed to high
pressure steam in the range of 50 to 150 p.s.i.g. while being abraded
in the single disc or double disc pressurized refiner 67. Refined fibers
are then delivered to collector 68.
Because the chips are pre-dried, very little water is left
to be driven off. Hence, most of the heat of the steam and the heat
of attrition applied to the chips elevates their temperature to
approximately 500 to 700 F. This represents a substantial savings in
energy. For example, the conventional refiner ground wood system used
as much as 80 to 100 horsepower days per ton of finished fiber. The
process of high temperature refining according to the invention requires
only 4 to io horsepower days per ton of fiber. The process according
to the invention is therefore highly energy effieient, a major consideration
71'7~ '
-- 8 --
in contemporary manufacturing processes. A minimum of 0.5 lbs. of
steam is required for each pound of dried fiber produced. In the refiner
the high temperatures literally melt the lignin contained in the fibers.
During refining the lignin is redistributed over the surface of the fibers.
Lignin redistribution is important in order to obtain an effective reaction
with the surface resin subsequently to be applied, to produce the superior
product formed in accordance with the present invention.
After, refining the fibers are classified at 70, rejects being
blown by fan 72 back to collector filter 52. The final fibers are
gathered in collector 74. If the fibers are to be shipped to another
location for further processing, they are baled in baler 76, weighed in
scale 78 and shipped.
Referring to Figures 2a and 2b, the refined fibers are now
processed to form a fiber mat. If the fibers arrive in baled form, a
bale opener 80 liberates the fibers, while fan 82 delivers them to
collector 84, thence to doffing roll bin 86.
l:~offing roll bin 86 meters the fibers by holding a few
minutes of processed fiber to reduce surges. The fibers are then
delivered to a batch blender 88. Blender 88 also receives resin binder
and, if desired, wax through pump 90, and any other auxiliary chemicals
through feeder 92. Textile fibers are also introduced into blender 88
from collector 94, which receives a supply of textile fibers through fan
96, opener blender 98, prefeeder 100 and bale opener 102.
A phenolic dry powdered resin binder finely ground to a
mesh of 200 may be used, in the range of 1 to S percent of dry phenolic
resin to dry weight of wood fiber. The wood fiber entering blender 88
has a solids content of approximately 90 to 80 percent. Surprising, only
l to 5 percent resin is required to produce a highly satisfactory product.
Other resins which may be used are urea-formaldehyde, isocynate or
lignin based resins, to name just a few.
The binder employed may be virtually any organic binder
of the type conventionally used to produce medium density fiberboard,
hardboard and particle board products. The binder can be either
thermoplastic, thermosetting or a two-polymer type, the only real
requirement is that the binder be capable of bonding the fiber in such
il~71'~
g
a way that the end product produced is capable of passing end product
use specifications. Animal, vegetable and other adhesives meeting such
requirements are also acceptable.
Additional additives used, if any, may comprise such
compositions as wax for water resistance, copper salts for preservation,
borax compounds for fire prevention, etc., as desired, each in a manner
and amount well-known to the art.
The following is a list of a Iew of the binders which may
be used. The list is not exhaustive.
From Plastic Engineering Company (Plenco), Sheboygen,
Wisconsin 53601:
B Plenco 374 and 675 dry powdered penol ground to a minus
200 mesh.
Prom Richhold Limited, Northbay, Ontario:
lB936 PF and RD-019 dry powdered phenol ground to a
minus 200 mesh.
From Richhold Limited, Charlotte, North Carolina:
One part urea-formaldehyde resin rich-450 low viscosity M
D F resin.
From Pacific Resins and Chemicals, Inc., Atlanta, Georgia:
Resorcinol-phenol-formaldehyde resin
S-3409 - Catalyst
~3409-E - Resin
Fast curing phenol-formaldehyde resin
N-2212 at 40 percent N V (non-volatiles)
From Borden Chemical, Ontario, Canada:
Cascamite 1513~white powdered urea-formaldehyde resin.
From Upjohn Polymer Chemicals Div., LaPort, Texas:
ISO bind 100 ~ isocyanate-binder.
The textile fibers ~e for admixture in blender 88 are
relatively long, having a fineness of 3 to 4 denier and a length of 1/2
~ tr~e rna rk5
1~7~7'~
- 10 -
to 2 1/2 inches. Only a very small percentage of textile fibers is
required (1 to 3 percent) in order to achieve a high quality end product.
Typical fibers which may be used comprise nylon, polypropylene, rayon,
vinyon (waster polypropylene) cotton linters and cotton shoddy, to name
just a few.
The mixture is then metered through doffing roll bin 104
into feeder 106A, webber 106B and slitter 106C. Items 106A, B and C
B are par~ of a web or mat forming mechanism such as the "Rando-
Webber manufactured by Rando Machine Corporation of Macedon, New
York. This machine forms the fiber into a very well consolidated mat.
The mat emerging from the webber and slitter is compacted
in a compactor 108 (see Figure 3). Compactor 108 has a pair of
counterrotating cooperating driven rolls 120 which compress the mat 109
in their nip and propel it forward into a retarding cavity 122. The
retarding cavity has opposed stationary flexible retarding surfaces or
platens 124 which frictionally engage the advancing mat and tend to
retard its forward motion. This results in a lengthwise compression of
the mat and an increase in its density, with much more intimate fiber-
- to-fiber contact. Platens 124 are supported in holders 125 which are
pivoted at 126. The positions of platens 124 are maintained by pneumatic
or hydraulic cylinders 128. Pressure exerted on the mat by platens 124
snay be selected in accordance with the positions of the pistons in
cylinders 128.
Cornpactors exist which utilize a single roll fo~ advancing
material toward the retarding cavity. The basic principles of operation
of such compactors, and of the two-roll compactor used in connection
with the invention, are disclosed in Walton, U.S. Patent No. 3,260,778.
Single roll compactors are ordinarily used to crepe paper and laminated
webs. However, a single roll cannot adequately thrust a thicker mat
forward into the retarding cavity to obtain the desired longitudinal
compaction. The two rolls of compactor 108 overcome this deficiency
by cooperating as calender rolls to compress the mat and positively
drive it forward.
The fiber mat according to the invention is not visibly
creped by the two roll compactor. Instead, compactor 108 reduces the
de m~k
l7'~
-- 11 --
thickness of the mat by at least 60 percent from up to 3 or 4 inches
to approximately 1/4 inch or less. Upon emerging from the nip of the
two rolls the mate is compressed lengthwise to reduce its length by
about 10 to 15 percent and desirably increase its density by at least 175
percent. The mat has a density of approximately 3 to 5 lbs. per cubic
foot before entering the compactor, and a density of 10 to 20 lbs. per
cubic foot upon emerging. The mat emergir.g from the compactor is
self-supporting and strong enough to be wound into a roll on mat wind
up stand 110. In tests run on the two roll compactor 108 various mats
were produced in accordance with the invention using Aspen wood fibers
from Bemiji, Wisconsin. The results are as follows:
-12-
I o o o o o o o o
U~ r 111 U~ ~r O IS~ Il') O 11~ 0 0 0 0 el~ ~r ~r et~
~ ~ o ~ ~ ~ ~ ~ ep r~ ~r ~ ~r ~ ~ ~ ~ ~
~ ~' . ~3 '
W H O O O O O O O O O ~ O O G O O
~ --~ 0 ~
~ ~ o o o o o o o o o o o o o o o
:
~1 co o ~ o ~ o u~ ~
a
~o ~ co u~ ~ a~ ~ ~ ~ ~ ~ ~o o~ ~ ~
~ _1 O U~ o er O O ~ ~ _I ~ 0 00
li3 ~ ~ 00 ao ~ 1~ GO C~ 1~ t- 00 ~O 00 X 0~
E~ ~0 O.Oooooooo oooooo
'0 0 0 0 0 0 0 0 0 0 o O O o
I O ~ O u~
r~ ~r ~~1~ ~ ~r ~ ~ t~ ~ ~ t~
~N ~ 1 ~ o 1~ ~ D N ~ It~ a ~ ~
1~; ~ r~ ~U 1 ~ r~ r~ O r~ 0~ r~l O ~ o NO
~t r l r~l r l r l r l r l r-~ r-~ O r~l r l r1 r~l r l
~3 U~ ;~ r~ OO O O O O O O O O O O O O O
01
1~ ~3.r U 1~ t~ 1~ 1~ 1~ 1~ 1~ 1~ 1~ 1~ 1~ t~ al
~r; t~ ~ ~ ~ ~7 ~ ~ ~) ~ ~) ~ ~ ~ ~ ~ j5
~ ~ 8
U ra~ O ~ ~ O t~ N r l ~ 1~ r~ rt o U~ U~ ~ ~
~ ~. co ~ o a~ o ~r o L~ ~ co ~ 0
l~i ~ ~ ~ o o o o o o o o In ~ O ~ O O rl . ~
~d~ ~ *~lc
m ~0 ~ ~
r l r l ~ ~ ~r ~D 1~ CO a~ r~l r~l r l r I r-l r-l ~
f~
1~71'7~
- 13 -
Because compactor 108 develops such an intimate fiber-to-
fiber contact in the mat, a satisfactory mat may contain a relatively
high percentage of fibers which contain little or no lignin. For example,
satisfactory mats have been produced according to the invention using
up to 50% comminuted municipal refuse fiber, added to refined ligno-
cellulosic fibers before blending with the required resin. In fact, it has
been possible to produce certain fiberboard products from mats made in
accordance with the invention exclusively of municpal refuse fiber and
resin. Of course, such "all-refuse" products are not as strong as those
formed from mats containing a relatively high percentage of ligno-
cellulosic fibers, but they do find useful application in certain areas.
One use for such a mat is a core in a fiberboard product, sandwiched
betweeh and laminated to two stronger mats made in accordance with
the invention containing a relatively high percentage of ligno-cellulosic
fibers.
Referring to Pigure 2b, the wound mat may be installed in
a mat unwind stand 112, from which it is unwound and delivered to a
molding press 114,` a continuous press 116, a calender stack or other
machinery for subsequent formation into a finished fiberboard product.
Example: A sample fiberboard product was form ed (having
a density of 46 lbs. per cubic foot) from a mat produced by the process
of the invention. The resultant modulus of rupture of the fiberboard
product was 5,000 p.s.i. The resultant modulus of elasticity of this
sample was 350,000 p.s.i. Its internal bond was 150 p.s.i.
In contrast to this, a fiberboard sample having the same
density was made from a mat produced by a process wherein the refining
of the cellulosic fibers took place at atmospheric pressure and relatively
low temperature. The resultant modulus of rupture of this sample was
2500 p.s.i., only half of that of the preceding sample. It modulus of
elasticity was only 250,000 p.s.i, and its internal bond strength was 70
p.s.i.
It is flpparent from the foregoing description that the process
according to the invention successfully accomplishes its objectives. The
process forms a self-supporting mat structure of uniform thickness and
density. The mat could contain as much as 98% dry refined comminuted
1'7'~
- 14 --
cellul-osic fibers, thermosetting or thermoplastic resins as well as long
organic (over 1/2") or inorganic textile fibers, depending on end product
requirements. The basic cellulosic fibers can be treated with fire
retardants as required.
The mat structure that is described is very unique in that
the mat has been compacted or densified in a direction parallel to the
mat surface. This quite unexpectedly produces a mat structure that
has high tensile, as well as mechanical strength and is extremely flexible.
These factors allow the mat to be rolled up in much the same way as
sheet metal or aluminum is coiled.
The mats as described have also been pre-treated with their
required resins. The mats can now be stacked to form several layers
depending on the thickness and density rquirements for the finished
product. The stacked mats when put under heat and pressure in a final
compaction stage, either in a stationary press, continuous press or heated
calender roll, will become one unified mass. There is no need for
additional resins to be applied between the layers of fiber mats.
It is also possible to produce a 3-dimensional molded product
that has varying cross sectional thickness with a constant density. This
is made possible by the capability of stacking mats, and the fact that
the second and other mats stacked can be pre-punched with voids that
will match up with die sections in a molding press to yield a part with
varying thicknesses, etc.
The self-supporting mat structure, due to its inherently good
tensile and mechanical strength, allows the mat to be automatically
unrolled and fed to multi-opening or single-opening presses, without the
need for caulless loaders, caul plates or press conveyors to transport
the mat into or out of such presses. Due to the unique parallel
compaction or densification of the fiber mat, a much more intimate
fiber to fiber contact is developed. This is not achievable through the
use of conventional formers and other devices. This more intimate fiber
to fiber contact increases final product strength, and allows products
such as typical nine point (chipboard) liner board, corrugating medium,
dry felt for asphalt impregnation, as well as medium density fiberboard
products to be produced.
l~L 71'7'~
-- 15 --
The self-supporting mat structure produced by this process
can be compressed, shaped or formed into either a flat board such as
medium density fiberboard, cardboard such as 9 point, or a Kraft-like
product such as linerboard corrugating medium. This unique new self-
supporting mat structure can also be used to produce at least the
following deep draw molded 3-dimensional contoured articles:
a) Building Industry 1. Exterior and interior
decorative wall panels.
2. Exterior and interior
window sills, as well as
window frames and door
jambs.
3. Concrete forms.
4. Crated suspended ceilings.
5. Embossed panels.
b) Automobile Industry 1. Dashboards.
2. Seats.
3. Body parts, such as ienders,
doors, and interior door
panels.
c) Furniture Industry 1. Table tops for indoor and
outdoor use.
2. Frames for upholstered
furniture.
3. Fronts for kitchen and
living room furniture.
d) Electronics Industry 1. Cabinets for television sets.
2. Cases for record players.
3. Loudspeaker fronts.
e) Packaging Industry 1. Pallets and containers.
2. Fruit cases.
3. Crates and vegetables.
It will be obivous to one of ordinary skill that numerous
modifications may be made without departing from the true spirit and
scope of the invention, which is to be limited only by the appended
claims.
