Note: Descriptions are shown in the official language in which they were submitted.
CA 02726586 2015-12-17
FOODSTUFF CONTAINER
[0001]
TECHNICAL FIELD
[0002] This invention relates to a new class of
materials to be used as substitutes for polyethylene and
poly(ethylene terephthalate), commonly known as PET.
Polyethylene and PET have many uses. For example,
waterproof or water-resistant paper or paperboard can be
made with polyethylene and PET coatings. Many products can
be produced from such waterproof or water-resistant paper
or paperboard, for example: dishes, trays or other
containers. These products can be used, for example, in
prepackaging foodstuffs that are to be reheated or cooked
in a microwave oven.
BACKGROUND ART
[0003] Kirk-Othmer Encyclopedia of Chemical Technology,
3rd Edition, Volume 24, Page 454, et seq. John Wiley & Sons,
Inc., 1984., teaches that waterproof paper or paperboard,
coated or laminated with a multi-thermoplastic material,
such as high-density polyethylene, or coated with an
aqueous latex solvent solution of a polymer include, among
the commercially important thermoplastic products PET. The
resulting paper or paperboard is useful for boxes, bags,
drums, and case liners among other industrial products and
packaging materials. Excellent barrier properties to
1
ak 02726586 2010-11-30
WO 2009/146454
PCT/US2009/045849
water, oil, water vapor, oxygen, and some other gases make
paper and paperboard coated with these resins especially
valuable and flexible for use as packaging materials and
boxes.
[0004] Ideally, these products would be recycled.
However, PET is not recyclable when contained on paper
and/or paperboard products (See, the aforementioned Kirk-
Othmer, Volume 3, Pages 497 - 502). PET is not recyclable
when in a mixture with paper and/or paperboard products.
PET is not recyclable when layered with paper and/or
paperboard products. Thus, a need exists to identify a
suitable alternative for polyethylene and PET. Otherwise,
timber resources will be further despoiled to create new or
replacement products; scarce landfill space will be filled;
and incineration of used paper products will cause further
pollution.
DISCLOSURE OF INVENTION
[0005] The present invention provides a substitute for
paper or paperboard products coated or laminated with
multi-thermoplastic materials, such as polyethylene, or
coated with an aqueous latex solvent solution of such
materials, such as PET. The polyethylene and/or PET
replacement coating, according to the present invention, is
also useful for all types of paper, bag stock, ream wrap,
roll wrap, corrugated, folding board, solid fiber, paper-
based microwavable or conventional oven, food trays.
According to the present invention, waterproof or water-
resistant paper and paperboard products are formed by
2
CA 02726586 2010-11-30
WO 2009/146454
PCT/US2009/045849
substituting an acrylic containing material for the
polyethylene and/or PET previously utilized.
[0006] According to the present invention, acrylics or
polyacrylates, which are preferably derivatives of acrylic
acid (CH2=CHCO2H) , or methacrylic acid (CH2=CH(CH3)CH2H), can
be made into polymeric substances to replace PET or
polyethylene in products, such as waterproof or water-
resistant paper and paperboard.
[0007] Such acrylics or polyacrylates can be used to
prepare coatings and solution polymers and polymerization
processes providing high yields of polymers in a form
suitable for a variety of applications. The polymer
products can be made to vary widely in physical properties
through controlled variation in the ratios of monomers,
employed in their preparation, cross-linking, and control
of molecular weight. They share common qualities of high
resistance to chemical environmental attack, excellent
clarity, and attractive strength properties. In addition
to acrylic acid itself, methyl, ethyl, butyl, isobutyl, and
2-ethyl acrylates are commercially manufactured on a large
scale and are available at better than 98 - 99% purity.
[0008] Suitable cross-linking agents for the acrylates
include compounds of zinc, such as zinc oxide solution.
Zinc oxide solution is a fine suspension of zinc oxide
particles usually in an aqueous vehicle. Many other
compounds can be used as cross-linking agents. Preferably,
at least one crosslinking agent is selected from the group
consisting of zinc oxide, ammonium oxide, calcium oxide,
calcium stearate, magnesium stearate, aluminum oxide,
isostearate, magnesium oxide, stannous oxide, tungsten
3
CA 02726586 2010-11-30
WO 2009/146454
PCT/US2009/045849
oxide, sodium tungstate, sodium tungstate dihydrate,
titanium oxide, aluminum stearate, zinc octoate, zinc salts
of fatty acids, zirconium oxide, calcium isosterate,
calcium salts of fatty acids, magnesium salts of fatty
acids, and aluminum salts of fatty acids.
[0009] In one embodiment of the invention, the cross-
linking agent includes a salt (as described herein) plus a
butyric acid and 5-carbon acids, such as isobolic 2-methyl
buteric and N-valeric acid. Generally, the fatty acids are
fatty acids of animal and/or vegetable fats and oils and
would be exempt from kosher compliance, since the potential
use of animal oils in the origin of the animal in question
may be unspecified. In such cases, the inorganic
substances would be preferred. It is considered within the
scope of this invention to incorporate more than one
substance to form the cross-linking agent. However, as
used throughout this description and claims the term,
"cross-linking agent" includes the above-described
compositions as well as heat, radiation or any other method
for initiation a cross-linking reaction in acrylic
materials.
[0010] Commercially available suitable cross-linking
agents include ZINC OXIDE SOLUTION NO. 1, available from
Johnson Wax Specialty Chemicals of Racine, Wisconsin. The
cross-linking agent is used in amounts sufficient to cross-
link the acrylic material.
[0011] The acrylic materials of the present invention
are preferably coated onto the paper or paperboard material
in any of a variety of ways. For example, in making paper
and kraft grades of liner, rolls of paper and kraft liners
4
CA 02726586 2010-11-30
WO 2009/146454
PCT/US2009/045849
are unwound from a parent reel or a slit or slash winder
into rolls of smaller size or feed into sheeters, such as
cut-size sheeters. Two methods of coating boxes or other
paper products are preferably utilized. The first method
is identified as a curtain coating process. A completed
board is passed through a curtain of emulsion of an acrylic
as in the present invention in a procedure commonly known
in the art of paper making as "curtain coating." The face
side of the board and the opposite side are coated with the
emulsion. The second coating process is "cascading." The
cascading procedure is different from the curtain coating
procedure in that a regularly corrugated box of any shape
or size can be placed on one end, such that the corrugated
flutes are vertical, to allow the emulsion to permeate the
entire structure with the acrylic emulsion cascading around
and through the container in a flat position that is easy
to stack for shipping. Other methods of coating include
coating the paper or paperboard during the paper making
process. For example, the paperboard during the paper
making process or a paper or kraft grade of liner may be
sprayed with an emulsion after the press section, but
before the drying section of a typical paper making process
or may be dipped into an emulsion such that in a typical
size press or applied before or after the calendar section.
[0012] It should be understood that according to the
present invention and throughout the specification and
claims, "coating" means "coating" or "impregnation" unless
otherwise indicated. The coatings of the present invention
exhibit excellent resistance to penetration by oil, grease
and other materials, but they also exhibit excellent
release properties when utilized as trays or pans
CA 02726586 2010-11-30
WO 2009/146454
PCT/US2009/045849
containing a flour or flour substitute foodstuff, eggs,
pastas, and sauces and vegetables and/or meets with or
without gravies or sauces. Thus, the present invention has
a wide range of packaging of foodstuffs that may require
heating, cooking, reheating, microwave and/or other ovens.
BRIEF DESCRIPTION OF DRAWINGS
[0013] These and other features, aspects, and advantages
of the present invention will become better understood with
reference to the following description and appended claims,
and accompanying drawings where:
[0014] FIG. 1: shows a photograph, illustrating
various releases of yellow cake and
traditional fudge brownies as baked in
baking trays;
[0015] FIG. 2: shows a photograph of Quiche baked in a
tray having a 56 lb pine liner; and
[0016] FIG. 3: shows a photograph of trays made
according to the present invention
after release of the Quiche baked
therein.
MODES FOR CARRYING OUT THE INVENTION
[0017] In the following examples, coatings and products
are compared to give a wide variety of test conditions
6
CA 02726586 2010-11-30
WO 2009/146454
PCT/US2009/045849
based on available samples. All tests were conducted using
a 10 oz. round "pie pan," six different coating
compositions chosen are as follows:
1.) 56# Kraft w/Bake-Kote 48 RC (Spectra-Kote)
2.) 354$ Kraft w/coating
3.) 354$ Kraft w/coating
4.) Coating Laminated to 564$ Kraft
5.) Coating Laminated to 564$ Kraft
6.) Adhesive laminated, Gold PET w/Gloss Coating on
PET
[0018] Yellow cakes and traditional fudge brownies were
baked in two sample trays for each coating. There were no
significant differences between samples 1, 2 and 3, but
sample 1 seemed to stick slightly more than 2 and 3.
Samples 4, 5 and 6 released product better than 1, 2 and 3.
The location of each sample in the oven caused some
different bake qualities and the samples that seem to be
baked more completely such as sample 4, release the
brownies and cakes very well. This was also the case with
samples 5 and 6, but neither released as well as sample 4.
[0019] Sample 4, 5 and 6 have better release than
samples 1, 2, and 3. Sample 4 had the best release,
especially if well-baked. A summary of release properties
can be found in FIG. 1.
[0020] A second battery of tests was conducted similar
to the first round including a comparative example to PET.
The coatings are as follows:
1.) 564$ Kraft w/Bake-Kote 48 RC (Spectra-Kote)
7
CA 02726586 2010-11-30
WO 2009/146454
PCT/US2009/045849
2.) 56# Pine Liner
3.) Laminated to 56# Kraft
4.) 56# Pine Liner w/Gold Matte Coating on PET
5.) 56# Pine Liner w/ Coating
[0021] Quiches were baked in two sample trays for each
coating. There were no significant differences between
samples 2 - 5, but sample 2 did have slightly more Quiche
stuck in it. Sample 1 performed poorly, one of them barely
released the Quiche at all. Much more grease soaked
through Sample 1 than any of the other samples. All
samples, except for sample 1, are acceptable coatings.
FIG. 2 shows a photographic illustration of the sample 1,
as compared to FIG. 3, which is a photographic comparison
of the trays made according to the present invention after
release of the product.
8
