Title: High gloss disposable pressware
Abstract: A high gloss, disposable pressed paperboard food container includes a glossy bilayer finish. The container is formed in a heated die set from a paperboard substrate provided with a first finish coating layer consisting essentially of a styrene-butadiene resin composition and a second, top coating finish layer consisting essentially of an acrylic resin composition applied to the first finish coating layer. The products of the invention typically exhibit a 60° gloss of greater than about 40 gloss units, as well as reduced moisture pickup and enhanced rigidity.
Patent Number: 6,893,693 Issued on 05/17/2005 to Swoboda, et al.
| Inventors:
|
Swoboda; Dean P. (DePere, WI);
Hultman; Jack D. (Neenah, WA);
Krause; Darrell F. (Appleton, WI)
|
| Assignee:
|
Georgia-Pacific Corporation (Atlanta, GA)
|
| Appl. No.:
|
004874 |
| Filed:
|
December 7, 2001 |
| Current U.S. Class: |
428/34.2; 428/34.1; 428/35.7 |
| Intern'l Class: |
B32B 029/00; B32B029/04; A47J027/00 |
| Field of Search: |
428/341,357,411
229/584
|
References Cited [Referenced By]
U.S. Patent Documents
| 2911320 | Nov., 1959 | Phillips.
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| 3336862 | Aug., 1967 | Brundige et al.
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| 3963843 | Jun., 1976 | Hitchmough et al.
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| 4078924 | Mar., 1978 | Keddie et al.
| |
| 4112192 | Sep., 1978 | Vreeland.
| |
| 4238533 | Dec., 1980 | Pujol et al.
| |
| 4478974 | Oct., 1984 | Lee et al.
| |
| 4503096 | Mar., 1985 | Specht.
| |
| 4521459 | Jun., 1985 | Takeda.
| |
| 4567099 | Jan., 1986 | Van Gilder et al.
| |
| 4606496 | Aug., 1986 | Marx et al.
| |
| 4609140 | Sep., 1986 | Van Handel et al.
| |
| 4609704 | Sep., 1986 | Hausman et al.
| |
| 4721499 | Jan., 1988 | Marx et al.
| |
| 4721500 | Jan., 1988 | Van Handel et al.
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| 4781566 | Nov., 1988 | Rossi et al.
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| 4832677 | May., 1989 | Hudgens et al.
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| 4898752 | Feb., 1990 | Cavagna et al.
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| 4948635 | Aug., 1990 | Iwasaki.
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| 4997682 | Mar., 1991 | Coco.
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| 5033373 | Jul., 1991 | Brendel et al.
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| 5049420 | Sep., 1991 | Simons.
| |
| 5088640 | Feb., 1992 | Littlejohn.
| |
| 5169715 | Dec., 1992 | Maubert et al.
| |
| 5203491 | Apr., 1993 | Marx et al.
| |
| 5249946 | Oct., 1993 | Marx.
| |
| 5326020 | Jul., 1994 | Cheshire et al.
| |
| 5334449 | Aug., 1994 | Bergmann et al.
| |
| 5340611 | Aug., 1994 | Kustermann et al.
| |
| 5603996 | Feb., 1997 | Overcash et al.
| |
| 5609686 | Mar., 1997 | Jerry et al.
| |
| 5770303 | Jun., 1998 | Weinert et al.
| |
| 5776619 | Jul., 1998 | Shanton.
| |
| 5795928 | Aug., 1998 | Janssen et al.
| |
| 5830548 | Nov., 1998 | Andersen et al.
| |
| 5852166 | Dec., 1998 | Gruber et al.
| |
| 5869567 | Feb., 1999 | Fujita et al.
| |
| 5932651 | Aug., 1999 | Liles et al.
| |
| 5972167 | Oct., 1999 | Hayasaka et al.
| |
| 5981011 | Nov., 1999 | Overcash et al.
| |
Primary Examiner: Pyon; Harold
Assistant Examiner: Patterson; Marc
Attorney, Agent or Firm: Ferrell; Michael W.
Parent Case Text
CLAIM FOR PRIORITY
This non-provisional application claims the benefit of the filing date of U.S.
Provisional Patent Application Ser. No. 60/257,339, of the same title, filed Dec.
21, 2000.
Claims
1. A disposable shaped paperboard food container with a bilayer finish press-formed
in a heated die set from a paperboard blank,
said paperboard blank being prepared from a paperboard substrate provided with
a first finish coating layer consisting essentially of a styrene-butadiene resin
composition and a second, top coating finish layer consisting essentially of an
acrylic resin composition applied to said first finish coating layer wherein said
first and second coatings contain up to about 2 lbs of mineral filler per 3,000
square foot ream and, wherein said food container exhibits a surface gloss of at
least about 40 gloss units as measured by test method ASTM D523-89, 60 degree method.
2. The paperboard food container according to claim 1, wherein said food container
exhibits a surface gloss of at least about 50 gloss units as measured by test method
ASTM D523-89, 60 degree method.
3. The paperboard food container according to claim 1, wherein said food container
exhibits a surface gloss of between about 45 gloss units and about 65 gloss units
as measured by test method ASTM D523-89, 60 degree method.
4. The paperboard food container according to claim 1, wherein said styrene-butadiene
resin composition and said acrylic resin composition are aqueous emulsions.
5. The paperboard food container according to claim 1, wherein said first finish
coating layer is applied to said paperboard substrate in an amount of from about
0.25 pounds to about 1.5 pounds per 3,000 square foot ream.
6. The paperboard food container according to claim 5, wherein said first finish
coating layer is applied to said paperboard substrate in an amount of at least
about 0.5 pounds per 3,000 square foot ream.
7. The paperboard food container according to claim 6, wherein said first finish
coating layer is applied to said paperboard substrate in an amount of from about
0.6 pounds to about 1 pound per 3,000 square foot ream.
8. The paperboard food container according to claim 1, wherein said second top
finish coating layer is applied to said paperboard substrate in an amount of at
least about 0.5 pounds per 3,000 square foot ream.
9. The paperboard food container according to claim 1, wherein said second top
finish coating layer is applied to said paperboard substrate in an amount of from
about 0.25 pounds to about 1 pound per 3,000 square foot ream.
10. The paperboard food container according to claim 1, wherein said styrene-butadiene
resin composition comprises a carboxylated styrene-butadiene resin.
11. The paperboard food container according to claim 1, wherein said paperboard
substrate has a basis weight of from about 100 to about 300 pounds per 3,000 square
foot ream.
12. The paperboard food container according to claim 11, wherein said paperboard
substrate has a basis weight of from about 125 pounds to about 150 pounds per 3,000
square foot ream.
13. The paperboard food container according to claim 11, wherein said paperboard
substrate has a basis weight of from about 150 to about 200 pounds per square foot ream.
14. The paperboard food container according to claim 1, wherein said paperboard
substrate is sized with a starch composition in an amount of from about 4 to about
15 pounds per 3,000 square foot ream and provided with a clay coating prior to
being coated with said first finish coating layer.
15. The paperboard food container according to claim 14, wherein said paperboard
substrate is coated with one or more clay coatings in a coatweight amount of from
about 8 lbs of clay coating per 3,000 square foot ream to about 24 lbs of clay
coating per 3,000 square foot ream underneath with said first and second finish
coating layers.
16. The paperboard food container according to claim 1, wherein the forming surfaces
of said heated die set are maintained at a temperature of from about 250°
F. to about 400° F. during pressing of said container.
17. A coated paperboard for making a paperboard food container with a bilayer
finish wherein said container exhibits a surface gloss of at least about 40 gloss
units as measured by test method ASTM D523-89, 60 degree method, said coated paperhoard comprising:
a) a paperboard substrate sized with from about 4 pounds of starch per 3,000
square foot ream to about 15 pounds of starch per 3,000 square foot ream and provided
with a clay coating;
b) a first finish coating layer consisting essentially of a styrene-butadiene
resin composition applied to said clay coating; and
c) a second finish top coat layer consisting essentially of an acrylic resin
composition applied to said first layer wherein said first and second finish coatings
contain up to about 2 lbs of mineral filler per 3,000 square foot ream.
18. The coated paperboard according to claim 17, wherein said paperboard substrate
is coated with one or more clay coatings in a coatweight amount of from 8 lbs of
clay coating to about 24 lbs of clay coating per 3,000 square foot ream underneath
said first finish coating layer and said second finish top coat layer.
19. The coated paperboard food container according to claim 17, wherein said
styrene-butadiene resin composition acid said acrylic resin composition are aqueous emulsions.
20. The coated paperboard according to claim 17, wherein said first finish coating
layer is applied to said paperboard substrate in an amount of from about 0.25 pounds
to about 1.5 pounds per 3,000 square foot ream.
21. The coated paperboard according to claim 20, wherein said first finish coating
layer is applied to said paperboard substrate in an amount of at least about 0.5
pounds per 3,000 square foot ream.
22. The coated paperboard according to claim 21, wherein said first finish coating
layer is applied to said paperboard substrate in an amount of from about 0.6 pounds
to about 1 pound per 3,000 square foot ream.
23. The coated paperboard according to claim 17, wherein said second top finish
coating layer is applied to said paperboard substrate in an amount of at least
about 0.5 pounds per 3,000 square foot ream.
24. The coated paperboard according to claim 23, wherein said second top finish
coating layer is applied to said paperboard substrate in an amount of from about
0.25 pounds to about 1 pound per 3,000 square foot ream.
25. The coated paperboard according to claim 17, wherein said styrene-butadiene
resin composition comprises a carboxylated styrene-butadiene resin.
26. The paperboard food container according to claim 1, wherein said food container
exhibits a surface gloss of 45 or more gloss units as measured by test method ASTM
D523-89, 60 degree method.
27. The coated paperboard according to claim 17, formed into a container exhibiting
a surface gloss of 45 or more gloss units as measured by test method ASTM D523-89,
60 degree method.
Description
TECHNICAL FIELD
The present invention relates generally to disposable paper plates, paper bowls
and the like and more particularly to disposable paper pressware having a a styrene-butadiene
and acrylic surface. Preferred coats exhibit gloss of at least about 40 gloss units
(60 degree) and preferably at least about 50 gloss units and/or enhanced performance characteristics.
BACKGROUND
Disposable paper food containers are well known. Typically, such articles
are made by way of pulp-molding processes or by way of pressing a planar paperboard
container blank in a matched metal heated die set. Illustrative in this regard
are U.S. Pat. No. 4,606,496 entitled "Rigid Paperboard Container" of R. P. Marx
et al; U.S. Pat. No. 4,609,140 entitled "Rigid Paperboard Container and Method
and Apparatus for Producing Same" of G. J. Van Handel et al; U.S. Pat. No. 4,721,499
entitled "Method of Producing a Rigid Paperboard Container" of R. P. Marx et al;
U.S. Pat. No. 4,721,500 entitled "Method of Forming a Rigid Paper-Board Container"
of G. J. Van Handel et al; U.S. Pat. No. 5,088,640 entitled "Rigid Four Radii Rim
Paper Plate" of M. B. Littlejohn; U.S. Pat. No. 5,203,491 entitled "Bake-In Press-Formed
Container" of R. P. Marx et al; and U.S. Pat. No. 5,326,020 entitled "Rigid Paperboard
Container" of J. O. Chesire et al. Equipment and methods for making paperboard
container are also disclosed in U.S. Pat. No. 4,781,566 entitled "Apparatus and
Related Method for Aligning Irregular Blanks Relative to a Die Half" of A. F. Rossi
et al; U.S. Pat. No. 4,832,677 entitled "Method and Apparatus for Forming Paperboard
Containers" of A. D. Johns et al; and U.S. Pat. No. 5,249,946 entitled "Plate Forming
Die Set" of R. P. Marx et al.
Paperboard for disposable pressware typically includes polymer coatings.
Illustrative in this regard are U.S. Pat. No. 5,776,619 to Shanton and U.S. Pat.
No. 5,603,996 to Overcash et al. The '619 patent discloses plate stock provided
with a base coat which includes a styrene-acrylic polymer as well as a clay filler
as a base coat as well as a top coat including another styrene acrylic polymer
and another clay filler. The use of fillers is common in the art as may be seen
in the '996 patent to Overcash et al. In the '996 patent a polyvinyl alcohol polymer
is used together with an acrylic emulsion as well as a clay to form a barrier coating
for a paperboard oven container. See column 12, lines 50 and following. Indeed,
various coatings for paper form the subject matter of many patents including the
following: U.S. Pat. No. 5,981,011 to Overcash et al.; U.S. Pat. No. 5,334,449
to Bergmann et al.; U.S. Pat. No. 5,169,715 to Maubert et al..; U.S. Pat. No. 5,972,167
to Hayasaka et al..; U.S. Pat. No. 5,932,651 to Liles et al.; U.S. Pat. No. 5,869,567
to Fujita et al.; U.S. Pat. No. 5,852,166 to Gruber et al.; U.S. Pat. No. 5,830,548
to Andersen et al.; U.S. Pat. No. 5,795,928 to Janssen et al.; U.S. Pat. No. 5,770,303
to Weinheart et al.; U.S. Pat. No. 4,997,682 to Coco; U.S. Pat. No. 4,609,704 to
Hausman et al.; U.S. Pat. No. 4,567,099 to Van Gilder et al.; and U.S. Pat. No.
3,963,843 to Hitchmough et al. The disclosure of the foregoing patents is incorporated
into this application by reference.
SUMMARY OF INVENTION
There is provided in accordance with the present invention a high gloss disposable
paperboard food container with a glossy bilayer finish formed in a heated die set
from a paperboard blank. The paperboard blank is prepared from a paperboard substrate
provided with a first finish coating layer consisting essentially of a styrene-butadiene
resin composition and a second, top finish coating layer consisting essentially
of an acrylic resin composition applied to the first layer. The food container
of the invention exhibits a surface gloss of at least about 40 gloss units at 60°
as measured by test method ASTM D523-89. More preferably, the high gloss paperboard
food container according to the invention exhibits a surface gloss of 45 or more,
and in some embodiments at least about 50 gloss units at 60° (ASTM D523-89).
Typically the products exhibit a surface gloss between about 45 and 65 gloss units.
In general, the coating compositions applied to the paperboard include suitable
cross-linking agents and are water-borne compositions. The first finish coating
layer of resin is generally applied to the paperboard substrate in an amount of
from about 0.25 pounds per 3,000 square foot ream to about 1.5 pounds per 3,000
square foot ream. Typically the first coating is applied in an amount of at least
about 0.5 pounds per square foot ream, from about 0.6 to about 1 lb per 3,000 square
foot ream being preferred in some cases.
The second (acrylic) finish coating or top finish coating is generally applied
in amounts similar to the first coating. That is, generally from about 0.25 pounds
per 3,000 square foot ream to about 1 pound per 3,000 square foot ream. Again,
the top finish coating is typically applied in an amount of at least about 0.5
pounds per 3,000 square foot ream
If the primary goal is strength enhancement or reduced moisture pickup over the
current control; we would prefer to use from about 0.25 to about 0.5 lbs/3000 square
foot ream of styrene-butadiene resin and approximately double that amount of acrylic coating.
Most preferably, the styrene-butadiene resin composition includes a carboxylated
styrene-butadiene resin.
In general, the paperboard substrate has a basis weight of from about 100 to
about
300 pounds per 3,000 square foot ream. In some embodiments the paperboard substrate
may have a basis weight of from about 125 to about 150 pounds per square foot ream
while in other embodiments the paperboard substrate may have a basis weight of
from about 150 to about 200 pounds per square foot ream. The paperboard is usually
sized with a starch composition in an amount of from about 4 to about 8 pounds
per 3,000 square foot ream prior to being coated. In some embodiments the paperboard
will be sized with a starch composition in an amount of from about 6 to about 7
pounds per 3,000 square foot ream. For higher strength products, the amount of
starch in the board is preferably in the range of from about 8 to about 15 lbs
of starch per 3000 square foot ream. The sized paperboard substrate is typically
coated with one or more clay coatings in a coatweight amount of from about 8 lbs
of clay coating per 3,000 square foot ream to about 24 lbs of clay coating per
3,000 square foot ream prior to being coated with the first and second finish coating layers.
The first finish coating composition consists essentially of a styrene-butadiene
resin composition that includes a styrene-butadiene resin, crosslinking agents
and so forth, but does not include a substantial amount of mineral fillers which
would alter the basic and novel characteristics of the invention, i.e., enhanced
gloss, increased wet and dry rigidity and reduced moisture pickup. Preferably,
the styrene-butadiene resin composition contains no mineral filler whatsoever.
Likewise, the acrylic resin composition forming the second or top finish layer
includes an acrylic resin, crosslinking agents and so forth, but does not include
substantial amounts of mineral filler which would alter the basic and novel characteristics
of the present invention. Preferably, the acrylic resin composition contains no
mineral filler whatsoever; in some embodiments, however, it may be possible to
add up to about 2 lbs of mineral filler per 3,000 square foot ream in the two finish
layers while maintaining enhanced gloss and performance characteristics. For embodiments
where gloss enhancement is not the primary goal, only those mineral fillers detracting
from the rigidity and moisture pickup qualities of the coating need be avoided
and it may be possible to add slightly more mineral filler to the finish coats
without changing the basic and novel characteristics of the pressware.
As used herein, "coatweight", lbs of coating per 3,000 square feet and like terminology
refers to the lbs of coating on a dry basis, i.e., without the water medium in
which the coating is dispersed prior to its application to the paperboard.
As noted above the inventive articles are generally made in a heated die set.
Such apparatus is well known in the art and is operated in accordance with the
present invention with a die forming surface temperature of from about 250°
F. to about 400° F.
In another embodiment of the present invention there is provided a method of
making
a high gloss paperboard food container with a glossy bilayer finish including the
steps of:
- a) preparing a coated paperboard substrate provided with a first finish
coating layer consisting essentially of a styrene-butadiene resin composition and
a second, top finish coating layer consisting essentially of an acrylic resin composition
applied to the first layer;
- b) scoring the paperboard with a pre-determined scoring pattern suitable
for forming the food container;
- c) cutting the scored paperboard into a shape suitable for forming the
food container; and
- d) heat pressing the paperboard blank into a high gloss pleated container
wherein the food container exhibits a surface gloss of at least about 40 gloss
units at 60° as measured by test method ASTM D523-89.
In a still further aspect of the present invention there is provided a coated
paperboard for making high gloss food containers which exhibit a surface gloss
of at least about 40 gloss units at 60° as measured by test method ASTM D523-89
including a paperboard substrate sized with starch in an amount of from about 4
to 15 pounds of starch per 3,000 square feet of paperboard and provided with a
clay coating; a first finish layer consisting essentially of a styrene-butadiene
resin composition in an amount of from about 0.25 pounds per 3,000 square foot
ream to about 1.5 pounds per 3,000 square foot ream and a second, top coat finish
layer consisting essentially of an acrylic resin composition applied to the first
layer in an amount of from about 0.25 pounds per 3,000 square foot ream to about
1 pound per square foot ream. The paperboard substrate is typically coated with
one or more clay coatings in a cumulative coatweight (solids) amount of from about
8 lbs of clay per 3,000 square foot ream to about 24 lbs of clay coating per 3,000
square foot ream.
In still yet another further aspect of the invention, there is provided a method
for improving the wet rigidity of a food container formed in a heated die set from
a paperboard blank, wherein the paperboard blank is prepared from a starch-sized
paperboard substrate provided with a clay coating and a finish coating applied
thereto, the improvement comprising applying a first finish coating layer to the
clay coating consisting essentially of a styrene-butadiene resin composition, and
applying a second top finish coating layer to the first finish coating layer consisting
essentially of an acrylic resin composition. The product is provided with a plurality
of pleats about its periphery and is characterized by enhanced wet rigidity. A
typical moisture pickup reduction may be 40% or so in accordance with the invention.
The first coating typically is applied in an amount of at least about 0.5 lbs per
3000 square foot ream of paperboard. A carboxylated styrene-butadiene resin is
preferred as are starch loadings of from about 4-15 lbs of starch per 3000 square
foot ream of paperboard. The claimed method typically reduces moisture pickup as
well and enhances dry rigidity.
BRIEF DESCRIPTION OF DRAWINGS
The invention is described in detail below with reference to the various figures
wherein like numbers indicate similar parts and wherein:
FIG. 1 is a schematic diagram illustrating a coated structure in accordance
with the present invention;
FIG. 2 is a schematic diagram of a matched die set forming press;
FIG. 3 is a schematic illustration of the apparatus of FIG. 2 showing a scored
paperboard blank positioned for forming; and
FIG. 4 is a schematic detail of the apparatus of FIG. 2 showing a finished product
after forming.
DETAILED DESCRIPTION
The invention is described in detail below with reference to the various figures
and tables. Such description is for purposes of exemplification only. Various modifications
to specific embodiments described within the spirit and scope of the present invention
which is set forth in the appended claims will be readily apparent to one of skill
in the art.
Generally speaking, the present invention is directed to high gloss pressware
containers with a glossy bilayer finish exhibiting a surface gloss of at least
about 40 gloss units at 60° as measured by ASTM D523-89. The surface gloss
is achieved by a unique combination of coatings as described hereinafter. The paperboard
may be any suitable paperboard known in the art; typically coated or sized with
a starch (sizing) composition in a sizing press in an amount of from about 4 to
about 15 pounds per 3,000 square foot ream. Suitable commercially available sizing
agents containing starch include: "PENFORD.RTM. GUMS 200," "PENFORD.RTM. GUMS 220,"
"PENFORD.RTM. GUMS 230," "PENFORD.RTM. GUMS 240," "PENFORD.RTM. GUMS 250," "PENFORD.RTM.
GUMS 260," "PENFORD.RTM. GUMS 270," "PENFORD.RTM. GUMS 280," "PENFORD.RTM. GUMS
290," "PENFORD.RTM. GUMS 295," "PENFORD.RTM. GUMS 300," "PENFORD.RTM. GUMS 330,"
"PENFORD.RTM. GUMS 360," "PENFORD.RTM. GUMS 380," "PENFORD.RTM. GUMS PENCOTE.RTM.,"
"PENFORD.RTM. GUMS PENSPRAE.RTM. 3800," "PENFORD.RTM. GUMS PENSURF," "PENGLOSS.RTM.,"
"APOLLO.RTM. 500," "APOLLO.RTM. 600," "APOLLO.RTM. 600-A," "APOLLO.RTM. 700," "APOLLO.RTM.
4250," "APOLLO.RTM. 4260," "APOLLO.RTM. 4280," "ASTRO.RTM. GUMS 3010," "ASTRO.RTM.
GUMS 3020," "ASTROCOTE.RTM. 75," "POLARIS.RTM. GUMS HV," "POLARIS.RTM. GUMS MV,"
"POLARIS.RTM. GUMS LV," "ASTRO.RTM. X 50," "ASTRO.RTM. X 100," ASTRO.RTM. X 101,"ASTRO.RTM.
X 200," "ASTRO.RTM. GUM 21," "CALENDER SIZE 2283," "DOUGLAS.RTM.-COOKER 3006,"
"DOUGLAS.RTM.-COOKER 3007," "DOUGLAS.RTM.-COOKER 3012-T," "DOUGLAS.RTM.-COOKER
3018," "DOUGLAS.RTM.-COOKER 3019," "DOUGLAS.RTM.-COOKER 3040," "CLEARSOL.RTM. GUMS
7," "CLEARSOLS.RTM. GUMS 8," "CLEARSOL.RTM. GUMS 9," "CLEARSOL.RTM. GUMS 10," "DOUGLAS.RTM.-ENZYME
3622," "DOUGLAS.RTM.-ENZYME E-3610," "DOUGLAS.RTM.-ENZYME E-3615," "DOUGLAS.RTM.-ENZYME
3022," "DOUGLAS.RTM.-ENZYME 3023," "DOUGLAS.RTM.-ENZYME 3024," "DOUGLAS.RTM.-ENZYME
E," "DOUGLAS.RTM.-ENZYME EC," "CROWN THIN BOILING X-10," "CROWN THIN BOILING X-18,"
"CROWN THIN BOILING XD," "CROWN THIN BOILING XF," "CROWN THIN BOILING XH," "CROWN
THIN BOILING XJ," "CROWN THIN BOILING XL," "CROWN THIN BOILING XN," "CROWN THIN
BOILING XP," "CROWN THIN BOILING XR," "DOUGLAS.RTM.-UNMODIFIED PEARL," and "DOUGLAS.RTM.-UNMODIFIED
1200." These sizing agents are all commercially available from Penford Products
Co. "PENFORD.RTM.," "PENCOTE.RTM.," "PENSPRAE.RTM.," "PENGLOSS.RTM.," "APOLLO.RTM.,"
"ASTRO.RTM.," "ASTROCOTE.RTM.," "POLARIS.RTM.," "DOUGLAS.RTM.," and "CLEARSOL.RTM."
are all registered trademarks of Penford Products Co. Other suitable starches,
including "SILVER MEDAL PEARL.TM.," "PEARL B," "ENZO 32 D," "ENZO 36W," "ENZO 37D,"
"SUPERFILM 230D," "SUPERFILM 235D," "SUPERFILM 240DW," "SUPERFILM 245D," "SUPERFILM
270W," "SUPERFILM 280DW," "PERFORMER 1," "PERFORMER 2," "PERFORMER 3," "CALIBER
100," "CALIBER 110," "CALIBER 124," "CALIBER 130," "CALIBER 140," "CALIBER 150,"
"CALIBER 160," "CALIBER 170," "CHARGE +2," "CHARGE +4," "CHARGE +7," "CHARGE +9,"
"CHARGE +88,""CHARGE +99," "CHARGE +110," "FILMFLEX 40," "FILMFLEX 50," "FILMFLEX
60," and "FILMFLEX 70," are all commercially available from Cargill, Inc. Cofilm
compositions which are film forming starch compositions available from National
Starch are also preferred in some cases.
Following sizing, one or more clay coatings are typically applied to the
paperboard substrate. A preferred clay coating may include 2 clay containing layers
each having a coatweight of from about 4 to about 12 lbs per 3,000 square foot
ream. Particular pigmented coatings are described in U.S. Pat. No. 5,776,619 to
Shanton as noted above. It will be appreciated that the coatweight of such clay
coatings is predominately due to the weight of the clay.
Following the base coat or coatings, a first finish coating consisting
essentially of a styrene-butadiene resin composition is applied to the coated paperboard
substrate. Any suitable styrene/butadiene containing resin composition may be used.
A preferred resin composition includes a carboxylated styrene-butadiene resin.
A particularly preferred resin is sold by Reichold under the Trademark Tykote 96038-00.
After the first finish coating is applied a second finish coating of consisting
essentially of an acrylic resin composition is applied to the first finish coating.
By acrylic coating it is meant that any suitable acrylic emulsion may be used.
Such emulsions are generally polymers of acrylic acid or its derivatives and salts.
Such compounds may include one or more of the following: polyacrylics and polyacrylic
acids such as poly(benzyl acrylate), poly(butyl acrylate)(s), poly(2-cyanobutyl
acrylate), poly(2-ethoxyethyl acrylate), poly(ethyl acrylate), poly(2-ethylhexyl
acrylate), poly(fluoromethyl acrylate), poly(5,5,6,6,7,7,7-heptafluoro-3-oxaheptyl
acrylate), poly(heptafluoro-2-propyl acrylate), poly(heptyl acrylate), poly(hexyl
acrylate), poly(isobornyl acrylate), poly(isopropyl acrylate), poly(3-methoxybutyl
acrylate), poly(methyl acrylate), poly(nonyl acrylate), poly(octyl acrylate), poly(propyl
acrylate), poly(p-tolyl acrylate), poly(acrylic acid) and derivatives and salts
thereof; polyacrylamides such as poly(acrylamide), poly(N-butylacrylamide), poly(N,N-dibutylacrylamide),
poly(N-dodecylacrylamide), and poly(morpholylacrylamide); polymethacrylic acids
and poly(methacrylic acid esters) such as poly(benzyl methacrylate), poly(octyl
methacrylate), poly(butyl methacrylate), poly(2-chloroethyl methacrylate), poly(2-cyanoethyl
methacrylate), poly(dodecyl methacrylate), poly(2-ethylhexyl methacrylate), poly(ethyl
methacrylate), poly(1,1,1-trifluoro-2-propyl methacrylate), poly(hexyl methacrylate),
poly(2-hydroxyethyl methacrylate), poly(2-hydroxypropyl methacrylate), poly(isopropyl
methacrylate), poly(methacrylic acid), poly(methyl methacrylate) in various forms
such as, atactic, isotactic, syndiotactic, and heterotactic; and poly(propyl methacrylate);
polymethacrylamides such as poly(4-carboxyphenylnethacrylamide); other alpha- and
beta-substituted poly(acrylics) and poly(methacrylics) such as poly(butyl chloracrylate),
poly(ethyl ethoxycarbonylmethacrylate), poly(methyl fluoroacrylate), and poly(methyl
phenylacrylate). Both finish coating layers should be FDA approved material.
The first finish coating layer and second top finish coating layer are typically
water borne and press-applied, suitably by way of a printing-type apparatus. Suitable
coating methods include gravure techniques, flexographic techniques, hydrophilic
coating techniques, coil coating, trailing blade coating methods and so forth.
A typical coated paperboard structure
5 of the present invention includes
paperboard
6, provided with a starch coating
8 on its upper and lower
surfaces. The starch may or may not form a continuous film on the surface of paperboard
6 as shown and largely penetrates into the paperboard as shown by dotted
lines
10 in the diagram, well toward the center of the fibrous paperboard structure.
On the food service side of the paperboard, there is provided atop starch
8
a first clay coating, typically a kaolin pigment coating
12 which includes
a latex binder. A second clay coating
14 is advantageously applied to coating
12. Coating
14 is likewise predominately clay and includes a latex
binder. The first finish coating
16 of the present invention is applied
directly to coating
14 and the second finish or top coating
18 is
applied directly to the first finish coating. First finish coating
16 consists
essentially of a styrene-butadiene resin composition, whereas second or top finish
18 consists essentially of an acrylic resin composition as noted above.
The product of the invention is, in general, formed with a heated matched pressware
die set, from paperboard plate stock of conventional thicknesses in the range of
from about 0.010 to about 0.040 inches. The springs upon which the lower die half
is mounted are typically constructed such that the full stroke of the upper die
results in a force applied between the dies of from about 6000 to 8000 pounds.
The paperboard which is formed into the blanks is conventionally produced by a
wet laid paper making process and is typically available in the form of a continuous
web on a roll. The paperboard stock is preferred to have a basis weight in the
range of from about 100 pounds to about 400 pounds per 3,000 square foot ream and
a thickness or caliper in the range of from about 0.010 to about 0.040 inches.
Lower basis weight paperboard is preferred for ease of forming and to save on feedstock
costs. Paperboard stock utilized for forming paper plates is typically formed from
bleached pulp furnish, and may be double clay coated on one side. Such paperboard
stock commonly has a moisture (water content) varying from about 4.0 to about 8.0
percent by weight.
The effect of the compressive forces at the rim is greatest when the proper moisture
conditions are maintained within the paperboard: at least 8% and less than 12%
water by weight, and preferably 9.5 to 10.5%. Paperboard having moisture in this
range has sufficient moisture to deform under pressure, but not such excessive
moisture that water vapor interferes with the forming operation or that the paperboard
is too weak to withstand the high compressive forces applied. To achieve the desired
moisture levels within the paperboard stock as it comes off the roll, the paperboard
is treated by spraying or rolling on a moistening solution, primarily water, although
other components such as lubricants may be added. The moisture content may be monitored
with a hand held capacitive type moisture meter to verify that the desired moisture
conditions are being maintained. It is preferred that the plate stock not be formed
for at least six hours after moistening to allow the moisture within the paperboard
to reach equilibrium.
The stock is moistened on the uncoated side after all of the printing and coating
steps have been completed. In a typical forming operation, the web of paperboard
stock is fed continuously from a roll through a scoring and cutting die to form
the circular blanks which are scored and cut before being fed into position between
the upper and lower die halves. The dies halves are heated as described above,
to aid in the forming process. It has been found that best results are obtained
if the upper die half and lower die half—particularly the surfaces thereof—are
maintained at a temperature in the range of from about 250° F. to about 400°
F., and most preferably at about 325° F.±25° F. These die temperatures
have been found to facilitate the plastic deformation of paperboard in the rim
areas if the paperboard has the preferred moisture levels. At these preferred die
temperatures, the amount of heat applied to the blank is apparently sufficient
to liberate the moisture within the blank under the rim and thereby facilitate
the deformation of the fibers without overheating the blank and causing blisters
from liberation of steam or scorching the blank material. It is apparent that the
amount of heat applied to the paperboard will vary with the amount of time that
the dies dwell in a position pressing the paperboard together. The preferred die
temperatures are based on the usual dwell times encountered for normal production
speeds of 30 to 60 pressings a minute, and commensurately higher or lower temperatures
in the dies would generally be required for higher or lower production speeds, respectively.
As will be appreciated by one of skill in the art, the knock-outs are important
for holding the container blank on center during formation and for separating the
finished product from the die halves, particularly during high speed operation.
There is shown in FIGS. 1 through 4 a metal die press
20 including an upper
die press assembly
22, commonly referred to as a punch die assembly and
a lower die assembly
24. That is, assembly
24 includes a mounting
plate
26, a segmented die
28 with a knock-out
30, a sidewall
forming section
32, a rim forming portion
34 and a draw ring
36.
It will be appreciated that metal die press
20 is ordinarily operated in
an inclined state in accordance with the following United States Patents, the disclosures
of which have been incorporated by reference into this application:
- U.S. Pat. No. 5,326,020;
- U.S. Pat. No. 5,249,946;
- U.S. Pat. No. 4,832,676;
- U.S. Pat. No. 4,721,500;
- U.S. Pat. No. 4,721,499;
- U.S. Pat. No. 4,609,140;
- U.S. Pat. No. 4,606,496 The die set includes a plurality of freely rotating
stop pins 38, 40, 42 and 44. Each pin 38-44
is constructed of steel or other suitable material and includes an elongated shaft
as well as a central bore. Bolts, preferably socket head shoulder bolts, are used
to secure pins 38-44 to draw ring 36 of segmented die 28
as shown in FIG. 2. Referring to FIG. 3 there is shown a blank 46
provided with a plurality of scores 48 which are subsequently formed into
pleats in the final product. That is to say, paperboard is gathered and pressed
into a pleat about scores 48. The pleats preferably are of the same thickness
as adjacent regions of the plate and are substantially radially coextensive with
the scores from which they are formed. Products in accordance with the present
invention thus preferably include a plurality of circumferentially spaced densified
regions of integrated fibrous structures extending radially over the sidewall and
rim; most preferably including at least about three layers of paperboard reformed
into substantially integrated fibrous structures generally inseparable into their
constituent layers and having a thickness generally equal to circumferentially
adjacent areas of the rim.
As shown in FIG. 3 it would be appreciated that the rotating pin blank stops
38-
44
are located on the forward portion of the lower die assembly
24, that is,
the downstream production portion of the die, such that a gravity fed blank, such
as blank
46, will contact the blank stops as shown. It could be seen that
pins
38-
44 are in opposing relationship at the periphery at the lower
die at a distance which is less than the maximum transverse dimension of the blank,
in this case the diameter of blank
46 since it is a circular blank and that
pins
40 and
42 are also located at a distance which is also less
than the diameter of the blank inasmuch as the plate will move in the direction
indicated by arrow
50 in the production process, it is important that the
rotating pin blank stops do not interfere with the motion of the finished product.
After the blank is positioned as shown in FIG. 3, the top assembly
22 is
lowered and the forming process is carried out in a conventional manner and the
product
52 is formed as shown in FIG.
4. In FIG. 4 there is shown
schematically a plurality of pleats
56 which correspond to scores
48.
That is to say, the excess circumferential material from the planar paperboard
blank gathers about scores
48 when a three-dimensional geometry is imparted
to the product to form pleats
56 which thus have an amount of material therein
corresponding to a plurality of paperboard layers. Preferably, this excess material
is pressed into substantially integrated fibrous structures, that is, where pressed
layers exhibit reduced void fractions as compared to the uncompressed board and
are not readily separated into their constituent layers in normal use under the
loads normally encountered in such use. Without wishing to be bound by any theory,
it is believed the finish coatings of the present invention enhances the formation
of strong pleats as reflected particularly by the enhanced rigidity of the inventive
articles seen below.
Most preferably, the integrated fibrous structures of the pleats contain material
corresponding to about 3 thicknesses of paperboard, yet have a thickness substantially
similar to adjacent circumferential areas of the sheet.
Materials and Test Methods
In the examples below, the following water-borne coating materials were used:
| Designation |
Class |
Source |
| |
| Tykote Base |
Aqueous Carboxylated |
Reichold Inc. (North |
| 96038-00 |
Styrene-Butadiene |
Carolina) |
| ("Tykote") |
Emulsion |
| Existing Acrylic |
Aqueous Acrylic Emulsion |
*** |
| Cork 6979a |
Aqueous Acrylic Emulsion |
Cork |
| |
|
Industries (Pennsylvania) |
| Michelman 706 |
Aqueous Acrylic Emulsion |
Michelman, Inc. (Ohio) |
| |
In the following Examples, gloss was measured using test method ASTM D523-89,
entitled 60° Gloss. Plate moisture pickup was determined by weighing the test
specimens, filling the plates approximately ½ fall with dionized water, the
initial temperature of the water in the plates being 71° C. (160° F.),
leaving the water in the plates for 30 minutes and measuring weight increase. Wet
and Dry Rigidity were measured on a Single-Service Institute (SSI) Plate Rigidity
Tester, Model ML4431-2, motorized. Each of these tests uses the SSI Rigidity Tester
to measure the force required to deflect the rim 0.5 inches while supporting the
plates at their geometric center. For the Wet Rigidity test, the plates are wet
with hot sauce at 150° F.
EXAMPLES 1-3
A series of paperboard pressware containers were prepared as generally above
utilizing
a starch-sized and clay-coated paperboard substrate provided with the 2 finish
coats (the base finish coat being the first applied finish coat) using the materials
indicated above in the amounts set forth in Table 2. A hydrophilic coating technique
was employed and the containers were pressed utilizing a die temperature of from
about 300 to about 350° F. Gloss was measured in accordance with ASTM D523-89.
Gloss units (60 degrees) are reported. The SBR/Acrylic finish coating exhibited
high gloss especially when at least about 0.5 lbs/ream SBR resin composition is used.
EXAMPLES 4-7
Following the procedure of Examples 1-3, another series of containers were
prepared using more finish coating resin as is reported in Table 3. The gloss of
the SBR/Acrylic system is even further improved in this series.
EXAMPLES 8-10
The coated paperboard containers of the invention were compared with acrylic/acrylic
finish coated products for performance in Table 4.
| TABLE 2 |
| Comparison of Gloss SBR/Acrylic vs. Acrylic/Acrylic |
| |
|
|
|
|
Gloss 60 |
| |
|
|
|
|
Degree, units |
| |
Base |
Base Finish |
|
Top Coat |
Die positions |
| |
Coat |
Coat Amount |
Top Finish Coat |
Amount |
1-5 Average |
| Example |
Type |
#/rm |
Type |
#/rm |
(Std. Dev) |
| 1 |
Existing |
0.55 |
Existing Acrylic |
0.50 |
25 (1.5) |
| |
Acrylic |
|
(Control) |
| 2 |
Tykote |
0.55 |
Michelman 706 |
0.60 |
50 (1.3) |
| 3 |
Tykote |
0.35 |
Cork 6979a |
0.61 |
31 (2.7) |
| TABLE 3 |
| Comparison of Gloss SBR/Acrylic vs. Acrylic/Acrylic |
| |
|
|
|
|
Gloss 60 |
| |
|
Base Finish |
|
Top Coat |
Degree, |
| |
Base Finish |
Coat Amount |
Top Finish Coat |
Amount |
units |
| Example |
Coat Type |
#/rm |
Type |
#/rm |
Average |
| 4 |
Existing |
0.61 |
Existing Acrylic |
0.57 |
31 |
| |
Acrylic |
|
(Control) |
| 5 |
Tykote |
0.73 |
Cork 6979a |
0.56 |
55 |
| 6 |
Existing |
0.61 |
Existing Acrylic |
0.61 |
29 |
| |
Acrylic |
|
(Control) |
| 7 |
Tykote |
0.81 |
Michelman 706 |
0.60 |
57 |
| TABLE 4 |
| Physical Properties SBR/Acrylic vs. Acrylic/Acrylic |
| Physical Property |
Example 8 |
|
Example |
| ↓ |
(Control) |
Example 9 |
10 |
| Base Finish Coating |
Existing Acrylic |
Tykote |
Tykote |
| Top Finish Coating |
Existing Acrylic |
Michelman |
Cork 6979a |
| |
|
706 |
| Dry Rigidity, grams |
294 |
405 |
383 |
| Wet Rigidity, grams |
214 |
325 |
346 |
| Plate Moisture Pickup, % |
11 |
3 |
6 |
The containers of Table 4 are of like construction, that is the plates of Examples
8 through 10 have the same geometry and coatings except that control Example 8
has 2 finish coatings of the same thickness but different composition than Examples
9 and 10 of the invention. The plates of the invention have reduced moisture pickup
of roughly 73% and 45% over Control Example 8; increased dry rigidity of roughly
38% and 30% as well as increased wet rigidity of a
