Note: Descriptions are shown in the official language in which they were submitted.
66925-509
2085789
--1
FIELD OF THE INVENTION
The present invention relates to laminates and
overlays, and more particularly to a miter-foldable
saturated paper-based overlay system and method for
fabricating the same.
BACKGROUND OF THE INVENTION
Decorative vinyl laminates are a recognized
alternative to natural woods in furniture manufacturing
and woodworking because they provide abrasion
resistance, scratch resistance, water resistance,
chemical resistance, barrier performance and flame
spread resistance. Adhesive technology has advanced to
the extent that various epoxy, emulsion and solvent
adhesives are available to bond the vinyl laminates to
the substrate, depending upon the desired application.
However, notwithstanding their physical
properties, vinyl laminates have high elongation which
result in a poor printed appearance. A typical vinyl
product has two plies, a solid color base (color
throughout) that is printed, and a clear vinyl that is
laminated over the print to protect it from abuse. The
clear film is often coated with a scratch-resistant
coating to enhance its protective properties. Vinyl has
a poor appearance when printed because it stretches in
the printing press and thereby "smears" the image.
20857~9
It would be deslrable to use paper instead of
vinyl because of the superior print quality and the
manageability of paper during lam~natlon. However,
papers lack the physical strength required of machinable
materlals. Particularly, in miter-fold applicatlons
wherein an overlay materlal (vlnyl) is glued to one side
of a partlcle board which is cut on the opposite side
w~th V-grooves and then bent at those grooves to form
corners and angles, paper would have to possess strength
sufflcient to resist tearing and/or splitting when the
miter-fold edge is formed.
Until the instant invention, the superior
printing quality of paper could not be exploited in
miter-fold appllcations because of the severe stresses
encountered during the miter-folding or "V-grooving"
operation. In view of the disadvantages of the prior
art vinyl laminate overlays, novel paper-based overlay
systems are needed.
2~5789
SUHMARr OF THE INVENTION
The present invention provides a paper-based
overlay system which comprises the use of a saturated
paper having sufficient "miter-fold" strength, adequate
smoothness for printers, and adequate adhesive anchorage
capab~lities for application to surface structures. A
method for making the overlay system is also disclosed.
A paper sheet is saturated with a saturant
comprising a latex having at least two components with
different Tg values to produce an overlay which
sufficiently resists the stresses of miter-folding, also
called "V-grooving", and possesses superior printing
qualities which favor its application on substrates such
as miter-folded boards and particle boards, cabinetry,
shelves, furniture, ~ntricate surfaces such as profile
wraps and molding strips, doors, frames, and other such
substrates which may or may not be formed by
m~ter-cutting/folding.
In an exemplary saturated paper-based overlay, a
sheet of paper is saturated with an acrylic/PVC blend
and hot calendered to a hlgh degree of smoothness.
Optionally, a thickener, such as sodium alginate, is
added to the saturant to reduce surface migration of the
lower Tg component, and a release agent, such as
sorbitan tristearate, is added to prevent the material
from sticking during calendering. The sheet may be
colored, printed, imaged, and/or patterned, such as by
rotogravure processes, and applied to one or more
surfaces of a substrate.
Overlaid substrates of the invention comprise the
use of the saturated paper sheet on a substrate such as
a board. The board may be miter-cut on at least one
surface and folded such that a continuous paper surface
~s presented at the miter-folded edge.
208~789
Other overlaid substrates include hlghly detailed
surfaces such as moldings and frames which have
intricate surfaces that may or may not involve
miter-cutting and folding but which nevertheless impose
stresses by v~rtue of the forces imposed on the paper by
the sharp grooves, angles, or detailing in the profile
wrapping.
The overlaid substrates of the inventlon may
therefore include cabinets, shelves, drawers,
enclosures, tabletops, doors, frames, molding, and the
like, which have saturated paper overlay adhered to at
least two non-coplanar surfaces.
A method for fabricating the overlay comprises
the step of saturating a paper sheet in a saturant
system comprising at least two components hav~ng
different Tg values. The saturated sheet is preferably
stack-calendered to obtain a uniform caliper and
smoothness, and optionally printed, colored, imaged,
and/or patterned, either before or after application to
boards or other surfaces. The method may further
compr~se the step of adhering the saturated paper sheet
to at least one surface of a substrate which is
miter-cut and folded to present a continuous paper
surface along the miter-folded cut.
A method for fabricating profile wrapping or
highly-detailed substrates overlaid with the saturated
paper-based overlay compr~ses the step of providing a
highly irregular surface and adhering the paper-based
overlay contiguously with the surface. In an exemplary
method, the paper ~s patterned with wood grain, and the
patterned paper is applied to a substrate surface to
create an appearance that the substrate or structure is
comprlsed of solld wood.
208578~
--5--
BRIEF DESCRIPTION ~F THE INYE TION
Flg. 1 is a dlagrammatlc view of a threadlng
system for the stack calender used ln accordance wlth
the present invent~on;
Flg. 2 is an lllustratlve comparison of ~mportant
properties of paper and vinyl for overlay applications;
Fig. 3 is a plan side-view of a saturated
paper-based overlay of the lnventlon appl~ed to a
substrate such as a board or structure;
F~g. 4 ls a plan slde vlew of the overlay-covered
substrate of Fig. 3 whereln the other surface of the
substrate has been mlter-cut;
Fig. 5 is a plan slde vlew of the miter-cut board
of Fig. 4 folded along mlter cuts;
Fig. 6 is a plan vlew of an enclosure formed by
foldlng together the miter-cut sectlons of the board
shown ~n Fig. 5;
Fig. 7 is a perspective illustratlon of ganged
saws for s~multaneous miter cuttlng;
F~g. 8 is a side lllustrative view of an
exemplary overlay system comprising a substrate havlng a
paper-based overlay; and
F~g. 9 is a slde cross-sectional view of a
substrate, such as a decoratlve molding strip, wh~ch has
a detailed surface upon which a saturated paper-based
overlay ls adhered.
2085789
DETAILED DESCRIPTION OF THE INVENTION
The invention comprises a saturated paper-based
overlay system, including overlaid substrates (or
structures), and methods for fabricating the same. As
used herein, the term "substrate" means and refers to
structures, materials, and/or objects.
The overlay system of the invention comprises a
paper sheet, preferably of heavy weight paper, that has
been saturated with a latex saturant having at least two
components with different glass transition (Tg) values.
An exemplary saturant comprises a latex blend of (1)
acrylic, which has a Tg of about -10; and
(2) unplasticized polyvinyl chloride (PVC), which has a
Tg of about +67. Although less preferred, ethylene
vlnyl acetate (EVA) can be substituted for the acrylic.
EVA also has a Tg of about -10. Styrene acrylate, vinyl
acetate, or methyl methacrylate may be substituted for
or added in combination with the PVC. Preferably, the
Tg of one of the latex components is such that at room
temperature the component does not tend to form a film.
Preferably, the Tg of the saturant components
d~ffer by 30. More preferably, the difference is at
least 40, and most preferably it is greater than 50.
For example, the acryllc/PVC blend has Tg values which
differ by 70. It is believed that the acrylic functions
as a binder which sets around or upon the cellulosic
fibers of the paper and the PVC latex particles which do
not form a film but remain for the most part as
individual particles; and that the PVC particles,
d~stributed about the cellulosic matrix, are then
melted, such as during calenderlng, and hold the system
together in a denser matrix than would the acrylic
acting alone.
20~5789
_
Suitable raw paper for use in the instant
invention must have good formation and good physical
strength, and must be saturable. The preferred raw
paper meeting these requirements is Owensboro HP-8 75#
available from W.R. Grace & Co.-Conn. Such paper has a
fiber composition of 85% (by weight) Northern Bleached
Softwood Kraft and 15% (by weight) Hemlock Sulfite.
Preferably, the paper is of a heavy weight, and the
cellosic fibers which constitute the paper are random,
such that the paper sheet has machine direction (MD) and
cross direction (CD) strength; in other words, it is
strong in many directions, although it is not necessary
that it be equally strong in all directions.
The saturant system must be able to withstand the
actual physical abuse delivered to the sheet during a
V-grooving operation. The physical properties that
relate best to this operation are, in the order of
importance, edge tear and tear initiation, internal tear
(tear propagation), delamination resistance, and tensile
strength/elongation. In addition, the saturant system
must have the ability to be calendered to a high degree
of smoothness, and must maintain that smoothness. An
immediate smoothness less than about 100 Sheffield units
is preferred.
An acrylic system, being plastic by nature,
calenders to the required smoothness. Acrylics are also
lightfast, which is a further advantage of the saturant.
Preferably, an acrylic latex such as HYCAR~ 26104
available from The B.F. Goodrich Chemical Company, i s
suitable for use in the invention. The acrvlic latex
can be used in an amount of from 55% to 96.75%, and
preferably 55-667., most preferably about 56.75%, on a
dry basis, depending upon the processing and smoothness
retentlon.
2085789
Wh~le lnorganic fillers may be used in the
saturant system, such as clay or titanium dioxide, these
tend to cause failures during miter-foldlng. Organic
fillers such as unplasticized PVC are less destructive
to the cellulose fibers during miter-folding because the
particles are spherical rather than platelet-shaped and
are believed to be less damaging to the strength of the
cellosic fibers in comparison with the inorganic
fillers. A suitable PVC latex is GEON~ 352, available
from B.F. Goodrich, which is used in an amount of from
OX to 40Z, preferably 33-40%, and most preferably about
40X, on a dry basis. An ethylene vinyl acetate ~EVA),
such as Dur-O-Set~ E-646, available from the National
Starch Company, may be used instead of the acrylic.
In order to increase the delamination resistance
of the overlay, it is necessary to reduce the level of
binder migration common during the drying of heavyweight
papers. ~ thickener can be added to the saturant system
for this purpose. Known cellulosic thickeners can be
used. Sodium polyacrylate and alkali reactive emulsions
can also be used. However, cellulosics impart solvent
resistance to the saturant (which can interfere with
printabiliy), and brittleness. Sodium polyacrylate and
the alkali reactive emulsions also exhibit these effects
and can be water sensitive as well. Accordingly, the
preferred thickener is sodium alginate. Kelgin~ MV,
available from Kelco, Inc., may be used in an amount of
from 0.15X to 0.35X, dry basis, to limit migration at
Yar jOU5 saturator line speeds.
208S7~J
g
Another functional ingredient for the saturant
system ls a release agent, whlch is belleved to mlgrate
to the surface of the sheet durlng the calenderlng
operation and provlde release from the hot steel rolls.
Emulsifled waxes or waxy materlals could be used for
this purpose, although emulsified waxes tend to cause
smoke generation during processlng. Waxy materials such
as stearylated melamine can impart other propert~es that
may or may not be undesirable, such as water res~stance
after processlng. Preferably, the release agent is
sorbitan trlstearate, such as T~EEN~ 65 from ICI
Americas, Inc. Sorbltan tristearate also can be used to
lmprove smoothness. It ~s used in an amount of from 0%
to 3% on a dry basis to provide release from the hot
calender rolls at varlous calender llne speeds.
Other lnert ingredients, such as pigments and
defoamers can be added. Preferably, the paper ls
saturated to a 40X add-on level.
An exemplary saturant system comprises the
following amounts of preferred ~ngredlents on a dry
sol~ds bas~s:
56.75% acrylic latex
40.00% polyvinyl chloride latex
0.25% sodlum alginate
3.00Z sorbitan tristearate
S1nce the pH of acryllc latexes ls generally low,
and the pH of PVC latexes is generally high. it is
preferred that the pH of the acryllc latex be rai;ed
w~th dilute ammonium hydroxide and that the PVC latex be
added thereto slowly. The order of addltion of the
remainlng ingredients is not crltical.
2085789
1 o
Fig. 1 illustrates an exemplary procedure for
fabricating an exemplary saturated paper-based overlay
in accordance with the instant invention. The paper is
unwound from roll 1, and passed by tension transducer
roll 2 to heated steel calender roll 4. The paper then
travels through a nip formed between roll 4 and fiber
calender roll 5, past mt. hope spreader roll 6, tension
rolls 3 and 3' (turned off and used as idler rolls~,
idler roll 7, and a eecond heated steel ca',ender roll 8
and fiber calender roll 5. The sheet then passes over a
steel idler roll 9, and is cooled by first and second
cooling rolls 10 and 11. Adequate heat transfer between
the paper web and these cooling rolls can be
accomplished by cooling the rolls with ordinary tap
water, which is typically at temperatures from 58F to
72~F, most typically 65F. The sheet then passes over a
large diameter mt. hope roll 12 and a large diameter
~dler roll 13, and is rewound on roll 14. The practical
m~nimum diameter of any of the rolls is about 3 inches.
The saturator squeeze rolls (not shown) and the calender
steel rolls must be of a diameter and construction that
will resist flexing while in operation. The m~nimum
diameter of any of the rolls is 3 inches.
Temperature of the heated calender rolls, line
speed and nip pressure are cr~tical ~n order to aehieve
uniform caliper and smoothness of the sheet. It is
preferred that the line speed be 150 feet/minute, that
the nip pressure be 1100 psig, and that the temperature
of the heated steel calender rolls a and 8 be 325F.
Sign1ficant deviations from these values may re5ult in a
product that is unstable in terms of smoothness.
74294-27
.. X. 1
_ 20857~9 66925-509
-1 1-
EXA~PLE 1
A comparlson of some of the properties of paper
and 8 mil vinyl sandwlch film is shown ln Fig. 2. The
vinyl sandwich film compared therein was produced in
accordance wlth the process outllned ln PLASTIC FILMS,
second edition, by John H. Briston, chapter 8, section
2, 1983.
In particular, the sandwich film is two
films, one colored and prlnted, and the other clear,
that are laminated together. Both of the films of thls
sandwich were made by the process outlined in section
8.2.
The saturated paper of Figure 2 was made in
accordance wlth the lnstant lnvention. The untreated
paper was saturated by forcinq the paper to enter a
large shallow pan containing the saturant mixture. The
paper was then d~rected through a pa~r of squeeze
rolls. The squeez~ng or wrlnglng of the paper controls
the add-on level. After squeez~ng, the paper was dried
by a combination of forced hot-air, infrared and contact
heat dryers. The paper was saturated to a 40X add-on
level. Once dry, the paper was rerolled and subjected
to the calendering process in accordance with the
lnstant ~nventlon.
208~789
Figure 2 shows the signif~cant advantages of
uslng paper instead of vinyl ~n terms of percent
elongat~on and Elmendorf tear (grams), w~thout
sacr~f~c~ng tensile strength (lbs/inch of w~dth). The
saturated paper does not stretch much in terms of
percentage elongat~on, and therefore reta~ns better
printing reglstration. However, the tear propert~es for
the paper are still high enough for adequate performance
in m~terfold applicat~ons. Preferably the saturated
paper used in accordance with the instant invention has
a caliper of 6-8 mils and a Sheffield smoothness of
about 8~.
In further exemplary paper-based overlays of the
invention, the saturated paper sheet is preferably
printed, colored, patterned, and/or imaged. The paper
overlays are compatible with nltrocellulose based ~nks
and pa~nts, polyurethane based ~nks and paints, and even
vinylic inks and paints. The papers may be ~maged or
patterned us~ng any known process, such as by
rotogravure processes which are often used by furn~ture
manufacturers to impart a woodgrain look. The papers
may also be colored with known ~nks or paints. In other
exemplary overlays, a protective coating may be applied
prior to or after ~nstallat~on of the paper to a
substrate surface. Most preferred are polyurethane
coatings and varnishes.
2085789
-13-
Exemplary saturated paper-based overlay systems
of the lnvention comprlse (1) a paper sheet saturated
wlth at least two latex components havlng dlfferent Tg
values and hot-calendered; and (2) a structure havlng at
least one surface upon which said saturated paper sheet
is adhered. Accordlngly, the system comprlses a sheet
of paper saturated ln a latex saturant comprlslng at
least two latex components, the flrst of said latex
components lncludlng acryllc or ethylene vlnyl acetate,
and the second of said latex components ~ncludlng
polyvlnyl chlorlde, styrene acrylate, vlnyl acetate, or
methyl methacrylate, said sheet belng calendered after
saturatlon; and a substrate havlng a surface for
dlsposltlon thereupon of sald saturated paper sheet,
whereby said paper sheet covers at least a portlon of
sald substrate. The substrate may further comprise
~oined non-planar surfaces, such as a mlter-folded
corner, across whlch the saturated paper is adhered as a
contlnuous, coherent sheet.
Flgs. 3-6 lllustrate a method for fabrlcatlng an
exemplary saturated paper-based overlay system whereln
the saturated paper sheet 28 ls adhered onto a flrst
side or surface 26 of a substrate such as a board 20 or
other surface structure. The adhesive 26 may be first
applled to the board 20 surface 22 or to the paper sheet
28 (Fig. 3). Mlter cuts 30 are made on the second or
opposlte side 24 of the board 20 to form separate
sectlons 30 (Fig. 4) whlch are then folded or joined at
the mlter cuts 30 (See Flg. 5~ to form the desired
object 34 such as a box 34. Cabinets, drawers, frames,
tabletops, doors, enclosures, speaker enclosures, and
other ob~ects may be fabricated using the saturated
paper 28, which wlthstands the stresses of mlter-cuttlng
30 and foldlng (Flg. 5) so as to present a contlnuous
sheet of paper at mlter-folded edges 29.
- -
20~5789
_
-14-
Known adhesives 26 may be used, such as urea
formladehyde, polyvinyl acetate, ethylene vinyl acetate
(EVA), or epoxies. The use of EVAs are preferred.
Fig. 7 illustrates the use of ganged saws 36 for
simultaneously miter-cutt~ng a number of grooves 30 at
once in a substrate such as a particle board 20. The
board has a saturated paper-based overlay 28 adhered on
a ma~or face. The paper overlay 28 may also be adhered
on minor faces 20b to provide a continuous appearance
when the ma~or and minor faces are simultaneously
viewed. The arrow 35 indicates a direction across the
mitercuts 30 for cutting a channel or groove (dotted
line) for containing a face plate or other surface
between the sides 20b when folded together.
As shown in Fig. 8, the saturated paper 28 may be
applied to a board 20, such as a particle, laminate, or
composite board, whlch has been miter-cut 30 at more
than one point on the board 28. The various miter cuts
30 may be variously angled and spaced from each other
such that an infinite variety of overlaid structures can
be fabricated. Accordingly, the saturated paper-based
overlay system of the invention is sufficiently strong
that the paper may be applied to a structure which is
subjected to numerous miter folds 30 which impose a
large cumulative stress to the coherent paper overlay
28, which nevertheless provides a continuous surface 29
at the folds 30.
The saturated paper-based system of the invention
may also include a substrate that is a decorative
mo1ding or strip, as shown in the cross-,ec~ional vi~w
at 35, which may or may not be miter-cut but which
presents irregularities and at least two surfaces which
are not co-planar. Such intricate surfaces may
seriously challenge the successful application of
decorative laminates.
2085789
-15-
Accord~ngly, an exemplary overlay system
compr~ses such a structure 35 as shown ~n Fig. 9 wh~ch
has a high degree of deta~l~ng, ~e. varlous sharp edges,
projections, ~ndentatlons, angles, and curves as
~ndicated generally at 36. The overlay 28 may be
opt~onally colored, pr~nted, and/or patterned.
As mod~f~catlons may be ev~dent to those sk~lled
~n the art, the forego~ng embod~ments are ~llustrat~ve
only, and the scope of the ~nvention ~s limited only by
the claims.
