Note: Descriptions are shown in the official language in which they were submitted.
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GREASE AND WATER RESISTANT ARTICLE
BACKGROUND OF THE INVENTION
(1) Field of the Invention:
[00001] The present invention relates to methods to impart grease
resistance and/or water resistance to materials, and more particularly to
methods of improving grease resistance and/or water resistance that
reduce or replace the use of fluorochemical compounds and involve two or
more treatment agents.
(2) Description of the Related Art:
[00002] Materials, such as paper and textiles, are commonly treated or
coated to improve their resistance to liquids such as water, grease and oil.
Commercial compounds such as ScotchgardTM and Scotchban0, both
products of Minnesota Mining and Manufacturing Co. have been widely
used to improve the barrier properties of papers, textile fabrics, nonwoven
fabrics, upholstery, carpet fibers, and the like.
[00003] ScotchgardTMO and Scotchban0, and similar products, contain
fluorochemicals, which have recently become the object of health and
environmental concerns because of their persistence and tendency to
bioaccumulate. Consequently, there is strong interest in replacing or
reducing the use of fluorochemical compounds such as perfluorooctane
sulfonate (PFOS), perfluorooctanoate (PFOA), polytetrafluoroethylene
(PTFE), perfluoro-n-decanoic acid (PFDA) and other perfluorinated
compounds that are widely used for imparting grease, oil, and/or water
resistance to the substrates to which they are applied.
[00004] Recently several products have been introduced into the
marketpiace as potential replacements for the fluorochemical compounds.
These materials are based ori inorganic materials like silica and on organic
polymers, or combinations of those materials. However, to date, these
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replacements have fallen short of the cost/performance standards
established by the fluorinated compounds in this area of use.
[00005] It is well known to modify the barrier properties of various
materials by the addition of a wax, and paraffin waxes have been used in
many of these techniques. Examples of the use of waxes for surface
treatment, coating, and the like can be found in U.S. Patent No. 4,117,199.
In U.S. Patent No. 4,097,297 to Keene, an oil and water repellant barrier
coating is described that consists essentially of a film forming polymer, a
fluorochemical surface tension modifier, and a plasticizer. Waxes,
coalescing solvents, and dyes are optionally included.
[00006] Poly(vinyl alcohol) has been widely used in films and coatings for
properties that range from water dispersability to barrier properties.
Examples of these uses are found in U.S. Patent Nos. 5,468,526,
5,110,390, 5,283,090, 6,113,978, US 2005/0042443 Al, and GB 2 185
404A, among others. In U.S. Patent No. 5,981,011 to Overcash etal. a
coated sheet material is described that has as one component a barrier
coating comprising a polymer mixture in which one polymer can be
poly(vinyl alcohol).
[00007] Several references describe circumstances where either paraffin
wax or poly(vinyl alcohol) can be used for one purpose or another. For
example, in U.S. Patent No. 5,620,793 to Suzuki et a/., a printing paper is
provided that has no special coating on the printing face and does not
cause bronzing in ink-jet printing. The paper also comprises an ink
penetration-retarding agent on the printing face that can be, among other
things, either poly(vinyl alcohol) or paraffin wax. In U.S. Patent No.
5,648,164 to Sakaki et al., a recording paper is described in which both
poly(vinyl alcohol) or paraffin wax are mentioned as potential ink
penetration-retarding agents. In U.S. Patent No. 6,919,111, to Swoboda
et al., a cellulosic multi-ply paperboard is described that contains
predominantly cellulosic fibers, a bulk and porosity enhancing additive,
and a size press applied binder coating. The paperboard can be coated
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with either a binder, such as poly(vinyl alcohol), or with a wax. A similar
composition having a coating of either a binder such as poly(vinyl alcohol)
or a wax is described in U.S. Patent No. 6,379,497, to Sandstrom et al.
[00008] In U.S. Patent No. 5,843,544 to Andersen et al., hinged starch-
bound cellular matrix clam-shell type containers are described that can be
coated on the interior with a wax coating. The container can also be
coated on the exterior with an elastomeric coating that can comprise
poly(vinyl alcohol) in order to strengthen the outer surface and reduce its
tendency to fracture during the hinging action. Similar articles produced
from a starch-bound cellular matrix reinforced with dispersed fibers and
having optional coatings of materials such as poly(vinyl alcohol) or wax are
discussed in U.S. Patent Nos. 5,660,900 and 5,683,772 to Andersen et al.
[00009] Wenzel et al., in U.S. Patent Nos. 5,654,039 and 5,837,383,
describe recyclable and compostable coated paper stock comprising a
substrate having a primer coat that can be poly(vinyl alcohol) and, in
addition, having a top coat that can include a wax composition, which can
be a paraffin wax. However, mixtures of primer coat and top coat
materials are not described.
[00010] In U.S. Patent Nos. 5,626,945 to Berzins et al. and 5,635,279 to
Ma et al., repulpable, water repellant paperboard is described that has a
coating comprising a wax component that can be a paraffin wax, mixed
with a polymer matrix of polymer chains ionically cross-linked through
pendant carboxylate groups. A preferred polymer matrix was described as
comprising a polystyrene-butadiene polymer copolymerized with a
monomer having carboxylic acid pendant groups. In the 5,635,279 patent,
poly(vinyl alcohol) is described as being an ionically cross-linkable polymer
that could be used in the invention, however, some carboxylate
functionality must be added to the polymer prior to use by copolymerizing
with a monomer having carboxylic acid pendant groups.
[00011] Other references have described the use of both waxes and
substances such as poly(vinyl alcohol) for various purposes, in particular
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in the field of surface preparations for paper and textiles. For example,
U.S. Patent No. 5,151,404 to Suzuki et al. describes thermosensitive
recording paper that does not curl and provides clear images with high
image density. The inventors claim that paraffin wax can be used as a
sizing agent in the paper, and poly(vinyl alcohol) can be used as a
stiffness-imparting agent.
[00012] U.S. Patent No. 5,763,100 to Quick et al., describes recyclable
acrylic coated papers that have water and grease resistance and limited
moisture vapor transmission characteristics. The papers can have a
primer coat, which is commonly a water-based dispersion of a polymer
such as poly(vinyl alcohol), and a further coating of a water-based
emulsion of an acrylic-styrene copolymer and a wax, which can be a
paraffin wax.
[00013] In U.S. Patent No. 5,180,614 to Escabasse, a supple
biodegradable sheet is described that is resistant to bursting and has poor
water and other liquid absorbing power. The sheet comprises fibers, an
optional moisture resisting agent, a binder, which can be poly(vinyl
alcohol), a moisture retaining agent, and a sizing agent, which can be a
paraffin wax.
[00014] Dettling, in U.S. Patent No. 5,773,131, describes a paper product
having a flavor seal and a vapor barrier that is produced by applying a
primer coating to the paper that can include poly(vinyl alcohol), and after
polymerizing the coating to form an amorphous net structure, applying a
cover coating mixture suitable for generating a vapor seal. The cover
coating mixture can include paraffin wax.
[00015] Dragner et al., in U.S. Patent No. 5,795,932, describe a surface
sizing composition for nonwoven substrates that includes a waxy material,
that can be a paraffin wax, but is preferably a stearylated melamine, and a
surfactantless vinyl polymer or copolymer emulsion that contains an alkali
soluble, acid containing copolymer, which acts as the only surfactant for
the waxy material.
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[00016] In U.S. Patent No. 5,928,741 to Andersen et al., laminated
articles fashioned from sheets having a highly inorganically filled organic
polymer matrix are described. The sheets can be coated with various
materials, selected to improve water penetration, or grease and oil
penetration, or to render the article substantially liquid-tight, or pressure-
tight, or to increase the flexibility of the article, and poly(vinyl alcohol)
and
waxes are included in a list of several possible coating materials. It is
stated that mixtures of the coating materials can also be used, but no
particular mixture is identified as being preferred. Methods for the
production of articles of a similar nature are described by Andersen et al.
in U.S. Patent Nos. 5,580,409 and 5,800,647.
[00017] In U.S. Patent No. 6,159,612, Chu et al. describe multilayer films
having a barrier layer containing a wax. The films are said to provide an
effective moisture and oxygen barrier without requiring such barrier agents
as polyterpenes, alicyclic hydrocarbons, or high barrier polyvinylidene
chloride coatings. The films include a layer comprising an olefin polymer,
and a barrier layer comprising a syndiotactic polypropylene homopolymer
and a wax. They can further include an outer layer that can be coated, for
example, with a poly(vinyl alcohol) coating.
[00018] Chang et a/. describe a method of making a flushable film having
barrier properties in U.S. Patent No. 6,479,105. The film can have a
water-dispersible substrate layer that can comprise poly(vinyl alcohol) that
is covered with a coating of a low molecular weight amorphous poly(alpha-
olefin) that can be admixed with a branched paraffin wax.
[00019] In WO 02/14426 to Dixit et al. (also US 7,019,054) a formulation
for providing oil and grease resistance and release paper properties is
described as including a fatty acid melamine and paraffin wax emulsion
and a poly(vinyl alcohol). Alternatively, the formulation can include a fatty
acid melamine wax and a poly(vinyl alcohol). A preferred fatty acid
melamine wax is a stearylated melamine wax. The formulation can be
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used as a coating to provide oil and grease resistance on paper and
paperboard, and can also be applied inline on a paper machine.
[00020] Despite the advances that recently have been made in the
attempt to find effective and environmentally benign alternatives to
fluorochemical barrier coatings, there remains a need for compounds or
methods that can be used to reduce the use of or to replace the
perfluorinated compounds in present commercial use as greaseproofing
and waterproofing agents for paper and the like. It would be useful if such
compounds and methods were cost effective and easy to apply. It would
also be useful if such compounds and methods were more
environmentally benign than the current fluorochemical compounds and it
would be useful if such compounds and methods were totally free of such
fluorochemical compounds.
SUMMARY OF THE INVENTION
[00021] Briefly, therefore the present invention is directed to a novel
method of improving grease and/or water resistance of a material, the
method comprising treating the material with wax and poly(vinyl alcohol).
[00022] The present invention is also directed to a novel composition for
improving grease and/or water resistance of a material, the composition
comprising wax and poly(vinyl alcohol).
[00023] The present invention is also directed to a novel material that has
been treated with a composition comprising poly(vinyl alcohol) and wax.
[00024] The present invention is also directed to a novel material that has
been treated with poly(vinyl alcohol), wax and a polyamine.
[00025] The present invention is also directed to a novel method of
improving the gas, water, water vapor, or grease resistance of a porous
material, the method comprising: applying to the porous material a first
treatment agent; and after the first treatment agent has been applied to the
porous material, applying to a surface of the porous material wax,
poly(vinyl alcohol), and optionally a polyamine, thereby improving the gas,
water, water vapor, or grease resistance of the porous material.
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[00026] The present invention is also directed to a novel porous material
having improved gas, water, water vapor and/or grease resistance
comprising the porous material having a surface on which is a first coating
of a first treatment agent and a second coating comprising wax, poly(vinyl
alc(jhol) and optionally a polyamine over the first coating.
[00027] The present invention is also directed to a novel porous material
that has been treated by the method described above.
[00028] Among the several advantages found to be achieved by the
present invention, therefore, may be noted the provision of compounds
and methods that effectively improve the grease and/or the water
resistance of a material and which are cost effective and easy to apply, the
provision of such compounds and methods that are more environmentally
benign than the current fluorochemical compounds, and the provision of
such compounds and methods that require reduced amounts of, or are
free of fluorochemical compounds.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[00029] In accordance with the present invention, it has been discovered
that treatment of materials, such as paper, with a combination of wax and
poly(vinyl alcohol) greatly improves the grease and water resistance of the
materials. In preferred embodiments, the degree of improvement is more
than would have been expected based merely on the additive effect of the
combination. In tests with uncoated paper, coating with wax or poly(vinyl
alcohol) alone provided grease resistance (reported as Kit numbers
measured according to TAPPI TEST METHOD T-559 "Grease Resistance
for Paper and Paperboard") of from about 1- 3, even at dosage rates of
up to 0.624 lbs total dry substance per 3000 ft2 of paper (lb. d.s./3000 ft).
In contrast, however, treatment with a combination of paraffin wax and
poly(vinyl alcohol) provided protection levels of Kit number 4, even at a
dosage as low as 0.156 lb d.s./3000 ft2, and protection of Kit number 5 at
0.468 lbs d.s./3000 ft2, and Kit number 6 at 0.624 lbs d.s./3000 ft2.
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[00030] In accordance with the present invention, it has also been
discovered that treatment of porous materials, such as paper, with an
optional first treatment agent, such as a conventional polymer latex/filler
surface coating, followed by a treatment with wax, poly(vinyl alcohol) and
optionally a polyamine, greatly improves the gas, water, water vapor,
and/or grease resistance of the materials, even at relatively low levels of
the second treatment. In preferred embodiments, the degree of
improvement is more than would have been expected based merely on the
additive effect of the two treatments.
[00031 ] The intentof the invention is that the first treatment step is an
optional step, and the first treatment agent is an optional agent.
Accordingly, as used herein, reference to the second treatment step,
second treatment agent, and/or the second coating will be understood as
being the only treatment step or coating when the first treatment step or
coating is absent in accordance with the intent of the invention.
[00032] In tests with 190# whiteboard, a commercial coating of a polymer
latex and filler provided grease resistance (reported as Kit numbers
measured according to TAPPI TEST METHOD T-559 "Grease Resistance
for Paper and Paperboard") of about zero (0), but treatment of the coated
whiteboard with a wax/poly(vinyl alcohol)/polyamine coating, even at
dosage rates of under 10 lbs. d.s./ton of paper, improved Kit numbers to
about 5, while application of under 15 lbs. d.s./ton improved Kit numbers to
about 8, and under 20 lbs. d.s./ton improved Kit numbers to about 12.
[00033] Another feature of the present invention is that such superior
performance can be obtained without the use of higher, and more
expensive, grades of poly(vinyl alcohol). It has been shown that the
present methods can be carried out successfully with less expensive
grades of poly(vinyl alcohol), such as partially hydrolyzed and intermediate
hydrolyzed poly(vinyl alcohol), and that the use of higher grades, such as
fully hydrolyzed or super hydrolyzed, is not required. This feature is highly
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advantageous in controlling the expense of the coating procedure, and
improves the cost effectiveness of the innovative method.
[00034] In a further embodiment, the inventors have found that the
addition of a polyamine to the combination of wax and poly(vinyl alcohol)
provides additional improvement in the performance of the compositions.
For example, a combination of paraffin wax, poly(vinyl alcohol), and
dicyandiamide-formaidehyde condensate provided protection levels of Kit
number 7 at dosage rates of 0.468 lbs d.s./3000 ft2.
[00035] When the present specification refers to an improvement in the
gas, water, water vapor, and/or grease resistance of a porous material,
what is meant is any increase, no matter how small, in the resistance of
the porous material to penetration by any type of gas, water, water vapor
and/or grease. The term "grease", as used herein, refers to any type of oil,
fat, or lipid, whether natural or synthetic, and includes without limitation,
natural fats and oils, such as seed oils, including corn oil, soybean oil,
rapeseed oil, sunflower oil, and the like, lard, animal fats, and synthetic
oils, such as silicone oil and the like, and also liquid, semi-solid and solid
hydrocarbons.
[00036] In an embodiment of the invention, improving the gas, water,
water vapor, or grease resistance of the porous material comprises
increasing the grease resistance of the porous material as measured by
Kit number, where the wax, poly(vinyl alcohol) and optional polyamine are
applied in an amount sufficient to improve the grease resistance by at
least 3 Kit numbers. In another embodiment, improving the gas, water,
water vapor, or grease resistance of the porous material comprises
increasing the grease resistance of the porous material as measured by
Kit number, where the wax, poly(vinyl alcohol) and optional polyamine are
applied in an amount sufficient to improve the grease resistance by at
least a factor of 2 but no less than 2 Kit numbers.
[00037] In the present specification, the term "coating" is not intended to
be limiting to a surface coating, unless that is explicitly stated. By way of
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example, a coating of the first treatment agent can be applied by adding
the first treatment agent to the wet end of a paper machine. The first
treatment agent, therefore, is distributed throughout the depth of the
paper, but such application is still embraced by the term "coating", as used
herein. On the other hand, the terms "surface coating" are meant to refer
to a coating that is applied to the outer surface of a porous material, such
as a spray or roll coating applied to a dry paper web.
[00038] In an embodiment of the present method, the first treatment
agent can be any treatment agent that is know for use in sizing, increasing
water resistance, gas resistance, water vapor resistance, wet strength, dry
strength, softness, drape, hand, and/or the printability of a porous material,
except those agents that are not compatible with a subsequent treatment
comprising wax and poly(vinyl alcohol), optionally with a polyamine.
[00039] The first treatment agent can be applied during the formation or
manufacture of the porous material, such as at the wet end of a paper
machine. Preferably, however, the first treatment agent is applied to a
surface of the porous material after the material has been formed. An
example of this is the application of the first treatment agent as a coating
on paper at the dry end of the paper machine, or at any time after
formation of the paper web.
[00040] The first treatment agent can be provided in the form of a
waterborne coating formulation or a solventborne coating formulation.
Commonly, the first treatment agent comprises a polymer binder. The
polymer can be applied neat, as in a hot melt roll application (such as is
used for the application of a polyethylene wax to paperboard for the
manufacture of milk cartons), or it can be applied as a solution or in a
dispersion as a latex. It is common that the polymer is dispersed as a
waterborne latex due to the low toxicity, safety and low organic emissions
of the application process.
[00041] Examples of polymers that are useful as the polymer binder of
the first treatment agent include poly(vinyl alcohol), polyacrylate,
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polystyrene/polyacrylic copolymer,'cellulose derivative, nitrocellulose, vinyl
chloride, vinyl chloride copolymers, vinyl acrylate copolymers, vinyl acetate
homopolymers, vinyl acetate copolymers, styrene butadiene polymers,
styrene butadiene acrylonitrile polymers, polyvinylacetate, proteins, milk
proteins, starch, and mixtures of any of these.
[00042] In one embodiment, the first treatment agent can include wax,
poly(vinyl alcohol) and optionally a polyamine. In other words, it can be
the same as, or similar to the composition that is used in the subsequent
wax/poly(vinyl alcohol) and optional polyamine treatment.
[00043] The first treatment agent can have additional components and
common additional components can include pigments, such as natural or
synthetic pigments; minerals, such as calcium carbonate, titanium dioxide,
Kaolin clay, Montmorillionite clay, and gypsum; organic opacifiers;
lubricants; surface sizes, such as starch; saturants; release coatings;
rheology modifiers; dispersants; insolubilizers; or plasticizers, such as
dioctyl phthalate, tricresyl phosphate, and castor oil. The first treatment
agent can include any of these materials and any mixtures thereof. In
some embodiments, latex binders with inorganic fillers, as described
above, are preferred.
[00044] The first treatment agent is applied in any amount that will
achieve the beneficial effects described above. However, in some
embodiments, it is preferred that the first treatment agent is applied in an
amount of from about 0.1 to about 50 g/m2. It is more preferred that the
amount of the first treatment agent to be applied is from about 1 to about
30 g/m2 , and an amount of from about 2 to about 20 g/m2 is even more
preferred.
[00045] Many commercially available materials may be used as the first
treatment agent. These include products marketed under the tradenames
of RHOPLEX, POLYCO, ROPAQUE, ACUMER and TAMOL, all available
from RohmNova, Mogadore, OH.
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[00046] It should be noted that the present invention embraces the
embodiment where the step of applying the first treatment agent is done
by another. In other words, the first step of applying the first treatment
agent is intended to embrace the act of selecting a pre-coated porous
material, to which one can then apply the wax/poly(vinyl alcohol) and
optional polyamine.
[00047] Although the present invention offers an advantage of providing
superior water and grease resistance with the use of coatings that are free
of fluorochemical compounds, the invention also embraces the situation
where a reduced amount of a typical fluorochemical water, oil and/or
grease proofing agent, such as perfluorooctane sulfonate (PFOS),
perfluorooctanoate (PFOA), polytetrafluoroethylene (PTFE), perfluoro-n-
decanoic acid (PFDA), or the like, is used in conjunction with the present
method to obtain superior Kit numbers. The conventional fluorochemical
agent can be applied prior to the present method, or is optionally applied
as the first treatment agent, and the second treatment agent is then
applied to provide superior levels of grease and/or oil and water
resistance. When it is said that a reduced amount of a typical
fluorochemical agent is used, it is meant that at ieast 10% less of the
fluorochemical agent is used than would otherwise be required to obtain
the Kit number that is achieved when the fluorochemical agent is used in
conjunction with the present method. Preferably, the amount of the
fluorochemical agent is 25% less, more preferably 50% less than would be
required without the use of the novel method.
[00048] In the present method, after the application of the first treatment
agent to the porous material (or the selection of a porous material having
had a first treatment agent applied to it), wax, poly(vinyl alcohol), and
optionally a polyamine is applied to a surface of the porous material,
thereby improving the gas, water, water vapor, or grease resistance of the
porous material.
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[00049] Any suitable poly(vinyl alcohol) can be used in the present
methods and compositions. Poly(vinyl alcohol) is a polymer comprising
vinyl acetate monomer units, some of which have been hydrolyzed to yield
alcohol functional groups on the polymer. Poly(vinyl acetate) and
poly(vinyl acetate-co-vinyl alcohol) are also included in the definition of
poly(vinyl alcohol). The polymer can contain other co-monomers such as
ethylene, propylene, butylene, ethylene oxide, propylene oxide, and the
like without departing from the scope of the invention. The poly(vinyl
alcohol) can be in the physical form of a solid, an emulsion, a suspension,
or a liquid solution.
[00050] The physical properties of poly(vinyl alcohol) are controlled by
molecular weight and the degree of hydrolysis, and a wide range of
commercial grades is offered by poly(vinyl alcohol) manufacturers. Some
of the commercially available grades of poly(vinyl alcohol) are: Partially
Hydrolyzed, Intermediate Hydrolyzed, Fully Hydrolyzed, and Super
Hydrolyzed. The molecular weight depends on the conditions of
polymerization, and the degree of hydrolysis is defined as the percent of
acetate groups replaced by hydroxyl groups during the hydrolysis reaction.
The specific gravity of poly(vinyl alcohol) solutions depends on
concentration and temperature and is independent of grade. Poly(vinyl
alcohol) reacts in a manner similar to secondary alcohols.
[00051] The poly(vinyl alcohol) employed in accordance with this
invention may be any grade poly(vinyl alcohol) that is compatible with
paraffin waxes and optionally with polyamines such as dicyandiamide-
formaldehyde condensate and that provides improved grease resistance
or improved water resistance, or both, when applied to a material, such as
paper, in combination with paraffin wax and optionally a polyamine.
[00052] In a preferred embodiment, the poly(vinyl alcohol) component
comprises a partially hydrolyzed poly(vinyl alcohol), typically having a
percent hydrolysis of about 87% - 89% and a viscosity of about 45 - 55
centipoise (4% aqueous solution at 20 C).
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[00053] The manufacture of poly(vinyl alcohol) involves starting with
polyvinyl acetate and converting that material to poly(vinyl alcohol)
generally by base-catalyzed methanolysis. Polyvinyl acetate
polymerization is done by conventional processes such as, for example,
solution, bulk or emulsion polymerization. The polymerization step
controls the ultimate molecular weight of the poly(vinyl alcohol). Catalyst
selection, temperature and solvent control the degree of polymerization.
[00054] The degree of hydrolysis of poly(vinyl alcohol) is controlled
during the alcoholysis reaction and is independent of molecular-weight
control. Fully hydrolyzed poly(vinyl alcohol) is obtained if methanolysis is
allowed to go to completion. The reaction can be terminated by
neutralizing or removing the sodium hydroxide catalyst. The addition of
small amounts of water to the reactants promotes saponification of
polyvinyl acetate, which consumes sodium hydroxide. The extent of
hydrolysis is inversely proportional to the amount of water added. Typical
degrees of hydrolysis of commercial grades of poly(vinyl alcohol) are:
Super Hydrolyzed (over 99.3%), Fully Hydrolyzed (98.0 - 98.8%),
Intermediate Hydrolyzed (91.0 - 96.5%, with range varying by molecular
weight), and Partially Hydrolyzed (86.0 - 89.0, with range varying by
molecular weight).
[00055] An example of a commercially-available poly(vinyl alcohol) which
is partially hydrolyzed and which is suitable for use in the present invention
is Celvol 840, which is available from Celanese Corporation of Dallas, TX.
[00056] In the present invention, the poly(vinyl alcohol) can be used neat,
or it can be used in combination with a defoamer. It is not uncommon to
add a defoamer when using an intermediate or partially hydrolyzed grade
or poly(vinyl alcohol).
[00057] Any wax can be used in the methods and compositions of the
present invention. Useful waxes may be natural or synthetic, or
combinations thereof, and may be macrocrystalline or microcrystalline.
The wax can be obtained from animal, vegetable or mineral sources, or it
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may be produced synthetically. Useful waxes generally have melting
points within the range of about 20 C to about 200 C, and include animal
waxes, mineral waxes, vegetable waxes, insect waxes, and synthetic
waxes including: beeswax; bayberry-myrtle; candelilla; caranday;
carnauba; castor bean wax; esparto grass wax; Japan wax; montan crude
wax; ouricury; retamo-ceri nimbi; shellac wax; spermaceti; sugar cane
wax; and wool wax-lanolin.
[00058] Of these waxes, petroleum waxes and synthetic waxes are
preferred for the methods and compositions of the present invention.
Paraffins and chlorinated paraffin waxes also are of interest as the wax
components of the present methods and compositions, as are waxes
produced by the emulsion polymerization of ethylene, styrene, or acrylates
(weight average molecular weights of about 10,000 to about 50,000).
Oxidized hydrocarbon waxes, such as those manufactured from the
Fisher-Tropsch paraffins, and the microcrystalline petroleum waxes (ester-
type waxes) also are useful in the methods and compositions of the
present invention.
[00059] Other synthetic waxes of entirely different structure such as the
fatty amides, imides, amines, and nitrites can be waxlike and can be used
in the present invention. The polyoxyethylenes or carbowaxes are an
important group of waxes because of their solubility properties and
compatibility with fatty materials.
[00060] The petroleum waxes, particularly paraffin waxes but also the
microcrystalline waxes are particularly preferred for use in the present
invention. The petroleum waxes are predominantly long chain (C16 -C50)
alkane compounds. The paraffins are mostly straight-chain molecules, but
may have branched claims. The microcrystalline waxes range in
molecular weight from about 400 to about 700 and have average
molecules of about 40 to about 50 carbon atoms. The microcrystalline
waxes have more branched-chain molecules than in paraffin waxes,
containing an average of three carbon atoms per side chain. Oxidized
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microcrystalline waxes also are useful in the compositions of the present
invention. Petroleum waxes contain both solid and liquid hydrocarbons
with the liquid hydrocarbons held in discrete droplets within the petroleum
wax. The paraffin waxes used in the compositions of the present invention
may be crude scale wax and/or fully refined wax.
[00061] Synthetic paraffin waxes are mixtures of saturated straight-chain
paraffinic hydrocarbons with short side chains (Cl - C4). The weight
average molecular weight is about 700 to about 800 or about 45-60 carbon
atoms per molecule.
[00062] Paraffin wax is a preferred wax for use in the present invention.
Any type or grade of paraffin wax can be used in the present invention that
is compatible with poly(vinyl alcohol) and optionally with a polyamine, and
that provides improved resistance to grease or improved resistance to
water, or both, when applied to a material such as paper in combination
with poly(vinyl alcohol) and optionally with a polyamine such as
dicyandiamide-formaidehyde condensate.
[00063] Preferred paraffin waxes are unbranched or sparsely branched
waxy white or colorless solid hydrocarbon mixtures that can be used to
make candles, wax paper, lubricants, and sealing materials. The chemical
composition of a preferred paraffin wax is a mixture of predominantly non-
aromatic saturated hydrocarbons with the general formula CnH(2n+2) where
n is preferably an integer between 12 and 50, and more preferably
between 22 and 27. It is preferable that the paraffin has a melting point, or
melting point range, between about 25 C and about 200 C, more
preferably between about 47 C and 95 C, and yet more preferably
between about 47 C and abut 65 C, and is insoluble in water. An example
of a preferred paraffin wax is available from Sigma-Aldrich, Milwaukee, WI,
as Cat. No. 31,765-9, having a CAS RN of 8002-74-2, and a melting point
range of 52 - 58 C.
[000641 Other organic materials can be used with, or added to, the wax
without departing from the scope of the invention. For example, when the
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wax is to be used as an aqueous emulsion, it is common to add an
emulsifier to the mixture to stabilize the emulsion. A commonly used
emulsifier for this purpose is a styrene-acrylate copolymer. Another
commonly used material is Morez 101 (a butyl acrylate methyl-
methacrylate copolymer available from Rohm & Haas). The wax, water,
and the emulsifier can be intermixed with high shear to form a stable
emulsion, which can then be used in suitable amounts to produce the
compositions of the present invention.
[00065] In some embodiments, it is preferred that paraffin wax and
poly(vinyl alcohol) be the only materials present that have a significant
effect on the grease and/or water resistance of the material. This is
advantageous in circumstances where it is desirable to limit the cost or
complexity of the treatment. In this instance, the treatment and
compositions are said to consist essentially of poly(vinyl alcohol) and
paraffin wax.
[00066] Optionally, a polyamine can be included as a component of the
wax/poly(vinyl alcohol)/polyamine coating. The preferred polyamine is an
amine-aldehyde condensate that is the reaction product of an amine
containing an active hydrogen atom and an aldehyde. Examples of the
amine include guanidine, urea, dicyandiamide, melamine, aniline,
ethylenediamine, diethylenetriamine, monoethanolamine, diethanolamine,
polyoxyalkyleneamines, polyoxyalkylenediamines,
polyoxyalkylenetriamines, and the like. Examples of the aldehyde include
formaldehyde, acetaidehyde, glutaraidehyde, glyoxal,
hexamethylenetetramine, and paraformaldehyde. Accordingly, examples
of polyamines that are useful in the present invention include a
condensation product of any one or more of the amines listed above with
any one or more of the aldehydes listed above. Polyamines that are
useful in the present invention also include, without limitation,
polyoxyalkyleneamines, polyoxyalkylenediamines,
polyoxyalkylenetriamines, and mixtures of any of these. Examples of
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these materials include the Jeffamine series of polyoxyalkyleneamines
available from Huntsman Corporation, The Woodlands, TX.
[00067] The reaction between the amine and aidehyde is usually
conducted in aqueous solution and can be done at acid, neutral, or
alkaline pH. The preferred condition is acid pH. Additional information
regarding the production of suitable dicyandiamide-formaldehyde
condensates can be found, for example, in U.S. Patent 3,957,574 to
Anderson.
[00068] A preferred polyamine for the present invention is a
dicyandiamide-formaldehyde condensate. Examples of polyamines that
are considered to be dicyandiamide-formaldehyde condensates, and
which are useful in the invention are available from Polymer Ventures,
Inc., Charleston, SC, as RD111-013 and PC-540. RD111-013 is an acid
condensation product of dicyandiamide, urea, and formaldehyde, and is
available as a clear viscous solution of 46% d.s. having a viscosity of 50 -
250 cps and a pH of about 5.5. It is cationic and has a density of about 10
lbs/gal. PC-540 is an acid condensation product of dicyandiamide, urea,
and formaldehyde and is available as a clear viscous solution of 50% d.s.
having a viscosity of 10 - 100 cps and a pH of about 3.5. It is cationic and
has a density of about 10 lbs/gal. Either of these polyamines can be used
as commercially supplied.
[00069] Polyamines, and dicyandiamide-formaldehyde condensates in
particular, are described in U.S. Patent No. 6,576,086 by Etti et al. as
being useful as fixing agents in the production of paper or paperboard
during paper stock draining. Similar materials are also discussed by
Anderson in U.S. Patent' No. 3,957,574 as being preferred dye fixatives in
a paper sizing agent. Dicyandiamide-formaldehyde condensates were
also discussed as possible replacements for cationic starch in sizing
agents in U.S. Patent No. 4,222,820 to Hiskens et al., and as
replacements for cationic resins used in a size for ink jet recording paper
by Miyamoto in U.S. Patent No. 4,576,867. However, none of these
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publications suggests the use of these polyamines in combination with a
wax and a poly(vinyl alcohol) for use to improve grease and/or water
resistance as is done in the present invention.
[00070] Furthermore, in U.S. Patent No. 5,423,911 to Coutelle et al. and
U.S. Patent No. 5,660,622 to Nikoloff, the use of dicyandiamide-
formaldehyde condensates as in paper coatings is described as being
undesirable for one reason or another.
[00071] In the present invention, combinations of poly(vinyl alcohol) and
wax, and optionally, a polyamine, are used in the second coating which
provides the superior, improvement in gas, water, water vapor and/or
grease resistance that has been described.
[00072] When the first treatment agent or the second coating include only
poly(vinyl alcohol) and wax as the penetration-resistance controlling
agents, the two components can be used in any amounts. However, it is
preferred that the ratio of the poly(vinyl alcohol) to the wax, by weight, is
within a range of about 10:90 to about 90:10, a range of about 25:75 to
about 75:25 is more preferred, a range of about 40:60 to about 60:40 is
even more preferred, and a range of about 45:55 to about 55:45 is yet
more preferred. In one embodiment, about 44% poly(vinyl alcohol) and
about 56% wax, by weight, has been found to provide improved
resistance.
[00073] When a polyamine is included in the second coating of the
present invention, the poly(vinyl alcohol), the wax, and the polyamine can
each be included in almost any relative amount. However, it has been
found to be preferred that the three components be used in combinations
in which the poly(vinyl alcohol) is within a range of about 3.to about 74 %
by wt. d.s. (where the dry solids (d.s.) include only the three components
of interest), the wax is within a range of about 13 - 96 % by wt. d.s., and
the polyamine is within a range of about 0.5 - 13 % by wt. d.s. It is more
preferred that the three components be used in combinations in which the
poly(vinyl alcohol) is within a range of about 22 to about 68 % by wt. d.s.,
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the wax is within a range of about 25 - 74 % by wt. d.s., and the
polyamine is within a range of about 3 - 12 % by wt. d.s. It is even more
preferred that the three components be used in combinations in which the
poly(vinyl alcohol) is within a range of about 38 to about 68 % by wt. d.s.,
the wax is within a range of about 25 - 55 % by wt. d.s., and the
polyamine is within a range of about 6 - 12 % by wt. d.s.
[00074] Alternatively, it has been found that the present methods and
compositions can be achieved with combinations of poly(vinyl alcohol),
wax, and polyamine having a weight ratio of the three components,
respectively, of about 4/5/1, or 5/4/1, or 4.5/4.5/1.
[00075] In the present invention, the poly(vinyl alcohol) and the wax, and
optionally the polyamine, can be intermixed into a composition that can be
applied to the porous material to be treated. Alternatively, the components
can be applied separately. If the components are administered separately,
they can be administered at approximately the same time, or they can be
administered at different times. By way of example, separate solutions or
emulsions of each component can be administered to the material to be
treated, or the solutions or emulsions can be intermixed and then applied
to the material as a single composition.
[00076] The poly(vinyl alcohol), wax, and optionally, the polyamine, of the
present invention can be present in the solutions, suspensions,'
dispersions, or emulsions, or in the compositions of the invention, in
almost any concentration. It is preferred that the present compositions
contain from about 0.5% to about 60% by weight dry substance, based
only on the poly(vinyl alcohol), wax, and polyamine, more preferred that
they contain from about 1% to about 50% by wt. d.s., and even more
preferred that they contain from about 20% to about 40% by wt. d.s. The
present compositions can be diluted prior to use, and after dilution, a d.s.
of about 3% to about 10% would be typical, and from about 5% to about
8% d.s. would be preferred.
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[00077] The wax/poly(vinyl alcohol) and optionally polyamine are applied
in a sufficient amount so as to provide the level of performance desired,
and that amount may vary widely according to the porous material and its
characteristics, such as porosity and surface roughness, as well as the
type and amount of the first treatment agent when one is used. The
rheological characteristics of the wax/PVOH/optional polyamine coating
composition, such as viscosity can also have an affect. When the
wax/PVOH/optional polyamine compositions are applied to sheet material
having a measurable surface area, such as paper, for example, typical use
rates for the present invention, whether only poly(vinyl alcohol) and wax
are used, or when a polyamine is also included, range from about 0.1 to
about 4 lbs dry solids (d.s.) per 3000 ft2 of surface of the material to be
treated. It is preferred, however, that the components be applied at a rate
of between about 0.1 and about 3 lbs d.s./3000 ft2, even more preferred is
an application rate of between about 0.15 to about 2.0 lbs d.s./3000 ft2,
more preferred is an application rate of between about 0.15 and 1.0 lbs
d.s./3000 ft2 , and yet more preferred is an application rate of between
about 0.4 and 1.0 lbs d.s./3000 ft2.
[00078] As mentioned above, materials other than the poly(vinyl alcohol),
wax, and optional polyamine can be used in the second treatment along
with these ingredients without departing from the scope of the invention. It
has been shown, for example, that it is often desirable to add an emulsifier
along with the wax in order to form a stable aqueous emulsion. Other
materials, such as colorants, dyes, preservatives, anti-fungal agents,
surfactants, and the like, can also be used along with the wax, poly(vinyl
alcohol) and optional polyamine in the present method.
[00079] Although it is possible, and even desirable, to provide and use
the wax, the poly(vinyl alcohol) and the optional polyamine in aqueous
solutions or emulsions, that is not required. In certain circumstances, for
example, it might be useful to provide one or more of the components in
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an organic solvent, or in a molten form, or even in a dry form, such as a
powder or flake.
[00080] The methods and compositions of the present invention can be
used to treat materials of any sort that would benefit from an improvement
in resistance to grease, or resistance to water, or both. The components
of the present methods can be applied as coatings or in any other fashion
at any point during the manufacture, packaging, storage, or use of the
material to be treated.
[00081] When the present methods and compositions are used to form a
coating, examples of materials to which they can be applied include
packaging and non-packaging materials such as paper, cardboard, bakery
board, butter and margarine chips, candy board, cup stock, frozen food
containers, plate stock, artist's papers, asphalt laminations, carbonizing
tissue, carton overwraps, cover and text papers, envelopes, garbage and
trash bags, label papers, paper placemats, release papers, soap
containers, wallpaper, liner board, folding cartons, multiwall bags, flexible
packaging, duplicator and reproduction papers, support cards and medical
dressings.
[00082] In addition, the present methods and compositions can be used
to improve grease, oil, and moisture resistance of asphalt, wood, textile
fabric, such as woven and non-woven fabrics, yarn, thread, carpets,
upholstery, paperboard, formed articles, medical dressings, and the like.
[00083] Present materials to be treated are porous, and therefore not
impervious to gas, water, water vapor and grease, although such
resistance may vary widely. The present porous materials are commonly
in sheet form and include substrates comprised of non-woven and woven
polymers such as fabrics, and cellulose-based materials, such as paper
and cardboard substrates, and the like. As used herein, the terms "sheet
material" refer to a material in a form that has length and width dimensions
that are each significantly greater than the thickness of the material.
Examples of sheet materials include paper, paperboard, housewrap,
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tarpaper, and the like. The amount of sheet materials can often be
characterized in terms of surface area, and the dosage rate of material
that is added to a sheet material can be expressed on the basis of the
surface area of the material. An example of this type of measurement is a
dosage rate expressed as lbs per ft2, or pounds per unit area.
[00084] In a preferred embodiment, the paper comprises a porous sheet
material made of a cellulosic material, or a cellulose-based material. Such
paper sheet materials include, for example, corrugated paperboard (or
"cardboard"), newsprint paper, uncorrugated Kraft paper stock, pan liner
paper stock, and the like. In addition to paper and paper-like materials,
other cellulose-based sheet materials, such as pressed board, may also
be suitable. It is also possible to use other fibrous materials for the
substrate sheet material.
[00085] As discussed above, the present invention can be used to
improve the grease and/or water resistance of paper. When used to treat
paper, the first treatment agent alone or along with the first treatment
agent and the wax/poly(vinyl alcohol) and optional polyamine can be
added to the wet end of a typical Fourdrinier machine, or they can be used
to coat paper after it has been dried. Alternatively, the first treatment
agent can be added to the wet end of a paper machine and the
wax/poly(vinyl alcohol) and optional polyamine can be added as a coating
to the paper at the dry end of the machine.
[00086] When the first treatment agent and/or the wax/poly(vinyl alcohol)
and optional polyamine are used as a coating, particularly on paper, the
components may be applied as a solution, emulsion, or dispersion, by roll
coater, brush, doctor blade or blade coater, sprayer or other such suitable
application means. Typically, the coated materials are dried after the
wax/poly(vinyl alcohol) and optional polyamine has been applied.
[00087] After the application of the wax/poly(vinyl alcohol) and optional
polyamine, further coatings or treatments may be applied to the material.
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Such coatings could include heat shielding coatings, UV-resistant
coatings, coatings with specific chemical resistance, or the like.
[00088] The coated material may be formed into a shaped article by
means other than folding and gluing, such as, for example, by pressure-
forming. Such shaped articles may be used for cooking or baking
purposes. For example, the coated material may be used to make a
container for storing food on a shelf (such as for storing pet food) while
preventing penetration of grease, oil and/or water through the material. Or
the coated material may be used to form a container such as a baking
tray. Likewise, the coated material may be used to form a food receptacle
such as a paper plate. Or the coated material may be used for fast-food
containers, such as boxes for fried chicken, or food wrappers, such as
wrapping materials for hamburgers and sandwiches. Thus, the coated
material may be used for any of a variety of applications as a food
container, wrapper or receptacle.
[00089] The following examples describe preferred embodiments of the
invention. Other embodiments within the scope of the claims herein will be
apparent to one skilled in the art from consideration of the specification or
practice of the invention as disclosed herein. It is intended that the
specification, together with the examples, be considered to be exemplary
only, with the scope and spirit of the invention being indicated by the
claims which follow the examples. In the examples all percentages are
given on a weight basis unless otherwise indicated.
EXAMPLE 1.
[00090] This example shows the preparation, application and efficacy of
compositions containing wax and polyvinyl alcohol and optionally a
polyamine as coatings for paper.
[00091] Paper sheets were supplied from a paper mill in Wisconsin. The
sheets were production run non- coated paper having a basis weight of 20
and 20.5 pounds per 3000 square feet.
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[00092] Sheets were coated with a Gardco automated drawdown
machine (available from Paul N. Gardner Company, Inc., Pompano Beach,
FL) running at 1.5 cm/ second, using various drawdown rod sizes to give
coat weights ranging from 0.05 to 2 dry pounds / 3000 square feet.
[00093] Grease resistance tests were conducted in accordance with
TAPPI TEST METHOD T-559 "Grease Resistance for Paper and
Paperboard"
[00094] Compositions A, B, and C, were made up as aqueous solutions
or emulsions with the various components of the present compositions.
[00095] Composition A (Poly(vinyl alcohol) solution in water).
[00096] Distilled water (450 g) was added to a 1-liter glass reaction flask
fitted with a condenser, and temperature probe. Agitation was started
using an overhead mixer and a glass rod fitted with a half moon mixing
blade. Celvol 840 (50 g), a partially hydrolyzed poly(vinyl alcohol) (PVOH)
available from Celanese Ltd., was slowly poured into the vortex to ensure
full wetting of the PVOH particles. The temperature was then increased to
85-90 C and the solution was allowed to cook for 1 hour until the PVOH
was fully dissolved.
Composition B (solution of poly(vinyl alcohol) and polyamine in water)
[00097] Distilled water (439.5 g) was added to a 1-liter glass reaction
flask fitted with a condenser, and temperature probe. Agitation was
started using an overhead mixer and a glass rod fitted with a half moon
mixing blade. Then 15.5 g of a 50% active urea-dicyandiamide-
formaldehyde copolymer (polyamine) was added. Celvol 840 (45 g) was
slowly poured into the vortex to ensure full wetting of the PVOH particles.
The temperature was then increased to 85-90 C and the solution was
allowed to cook for 1 hour until the PVOH was fully dissolved.
Composition C (emulsion of paraffin wax in water with styrene-acrylate
copolymer as an emulsion stabilizer)
[00098] Distilled water (300 g), 50 g of Morez 101 (a butyl acrylate
methyl-methacrylate copolymer available from Rohm & Haas), and 150g of
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paraffin wax (Sigma -Aldrich 52-58 C melting point) was added to a 1-liter
glass reaction flask fitted with a condenser, and temperature probe.
Agitation was started using an overhead mixer and a glass rod fitted with a
half moon mixing blade. The reactor was heated to 80 C and allowed to
mix for 1 hour until both the Morez and paraffin was completely melted. A
lab homogenizer (Ultra Turrax T25 from IKA Works, Inc.) was the placed in
the reactor and the reactor was allowed to cool to - 60 C. At 60 C the
homogenizer was turned on at 24,000 rpm for several minutes.
Compositions D - J (mixtures of wax and PVOH and optionally with
polyamine)
[00099] Compositions D-J where made in accordance with the relative
amounts of components as shown in Table 1. The appropriate amount of
Composition A or Composition B was placed in a 500m1 beaker fitted with
an over head mixing shaft, and the appropriate amount of Example C was
slowly added with agitation until the blend was smooth. Table 2 shows the
amounts of each of the three ingredients in each of Compositions A - J in
terms of the percent by weight of the component relative to the dry weight
of the total amounts of wax, poly(vinyl alcohol) and urea-dicyandiamide-
formaldehyde copolymer condensate in the composition. Accordingly, any
amount of other materials, such as emulsifiers, and the like, are not
reflected in the calculation shown in Table 2.
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Table 1: Grease and water resistance-improving compositions of
the present invention having various relative amounts of poly(vinyl alcohol)
and wax.
Composition Weight Ratio (g/g)
D B/C (95/5)
E B/C (90/10)
F B/C (70/30)
G B/C (50/50)
H B/C (30/70)
I B/C (10/90)
J A/C (70/30)
Table 2: Relative amounts of components in the compositions of Table 1
in terms of percent dry weight.
Composition PVOHa WaXb Polyamine
(% by wt. d.s.)d (% by wt. d.s.)d (% by wt. d.s.)d
A 100 0 0
B 85.3 0 14.7
C 0 100 0
D 74.2 13 12.8
E 67.5 25 11.6
F 38.4 54.9 6.6
G 22.2 74 3.8
H 11.2 86.9 1.9
1 3.2 96.2 0.6
J 43.8 56.2 0
Controle 0 0 0
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Notes:
a) PVOH is poly(vinyl alcohol) Celvol 840, from Celanese
Corporation.
b) Wax is paraffin wax having a melting point of 52 - 58 C from
Sigma-Aldrich.
c) Polyamine is dicyandiamide-formaldehyde condensate.
d) (% by wt. d.s.) means the percent of the component relative
to the total amount of PVOH, Wax, and Polyamine.
e) In the control sample, the paper had no treatment
[000100] All compositions were diluted with distilled water to 2% solids
before coating the base sheets. All sheets were coated using a Gardco
Automated Draw Down Machine to obtain a specific wet film of coating
and then dried on a LabTech Instruments Inc., Speedy Dryer for 3 minutes
at 105 C. Grease resistance was then measured by using TAPPI TEST
METHOD T-559 and reported as Kit numbers (Kit #'s). In the last column
on the right of Table 3, the 0.1 ml water drop size is an indication of the
wetting of the sheet and water repellency. In this test, distilled water (0.1
ml) was applied to the coated sheets using an automatic pipette and the
diameter of the water drop on the sheet was measured with a ruler. The
larger the water drop diameter, the more wettable the sheet and the lower
the water repellency. Those results are shown in Table 3.
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Table 3: Kit numbers for grease resistance and water repellency for
paper treated with the compositions shown in Tables I and 2. Dosage
rates were determined by the use of different drawdown rods and the base
paper was 20 - 20.5 Ib/3000 ft2 basis weight.
Drawdown Rod # 20 15 10 5 Size of
Dosage (lbs. dry/3000 0.156 0.1 ml
ft2) 0.624 0.468 0.312 water
Compositio Composition Weight drop
n Ratio (B/C) Kit Number (mm)
D 95/5 4 5 4 <3 8
E 90/10 8 7 5 3 8
F 70/30 6 7 6 5 7
G 50/50 5 5 5 4 7
H 30/70 5 5 4 4 7
1 10/90 5 5 4 4 7
A Composition A 2 2 1 10
B Composition B 2 1 1 10
C Composition C 3 3 3 7
F 70/30 (B/C) 7 6 4 7
J 70/30 (A/C) 6 5 4 7
Control No additives 0 0 0 0 12
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Discussion:
[00101] As the data show, compositions A, B, and C alone as a coating
at various dosages add little to no grease/oil resistance to the paper
substrate. At even the highest levels of application, the highest Kit number
obtained was 3. However, upon blending Composition A (PVOH) and
Composition C (paraffin wax) a noted increase in Kit number is observed
(Kit number 2-3 up to Kit number 5-6), even at the same total dosage of
solids. The incorporation of the polyamine into the combination with
poly(vinyl alcohol) and wax (noted as Composition F), but at the same
level of solids dosage, further increases the Kit number to 6-7.
[00102] The results for Compositions D-1 show that an optimum in
grease/ oil resistance is established with the blending of the paraffin wax
to the poly(vinyl alcohol)/polyamine blend, as indicated by the data in
Tables 2 and 3.
[00103] As for water repellency, the uncoated sheet resulted in a water
drop diameter of 12 mm compared to a range of 7 - 8 mm for the treated
samples. Furthermore, the uncoated sheet resulted in the water spreading
over time and soaking into the sheet, whereas the sheets coated with
Compositions D - I, as well as Composition C, showed smaller water drop
diameters, thus indicating improved water repellency, and showed no drop
spreading over time and no soaking in of the water drop. Paper coated
with Compositions A and B showed slightly improved water repellency
over the control, however there was some droplet spread over time, but
the drops did not soak into the sheets.
[00104] It can be concluded from the data that a combination of wax and
poly(vinyl alcohol) provided significantly improved grease and water
resistance to papers coated with the combination. Because the
improvement was obtained without any increase at all in the total amount
of solids used for the treatment, It is believed that such an increase is
unexpected. Furthermore, when a polyamine was added to the
combination, the grease and water resistance was further increased, and
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again without any increase in the total amount of solids used in the
treatment. Therefore, it is believed that the addition of a polyamine to the
combination of wax and poly(vinyl alcohol) used as a paper coating
provides an unexpected improvement in the grease and/or water
resistance of the coated material.
EXAMPLE 2.
[00105] This illustrates the efficacy of applying a wax/poly(vinyl
alcohol)/polyamine coating to coated and uncoated paperboard according
to the present method.
[00106] A coating having the composition of formulation "F" of Example
1, above, was applied to coated and uncoated 190# whiteboard by using a
Gardco Auto Draw II automated drawdown machine (Paul N. Gardner
Company, Inc., Pompano Beach, FL) operating at 1.5 inch/second coat
speed and using drawdown wire coating rods of different sizes to obtain
coatings of different thicknesses. The coated paperboard had been
commercially coated with a polymer latex binder/filler formulation prior to
the application of the wax/PVOH/polyamine coating.
[00107] The wax/PVOH/polyamine coating comprised 38.4% poly(vinyl
alcohol) Celvol 840, from Celanese Corporation, 54.9% paraffin wax
having a melting point of 52 - 58 C from Sigma-Aldrich, and 6.6%
dicyandiamide-formaldehyde condensate as the polyamine (all
percentages are on a percent of dry matter basis). The components were
dispersed in distilled water and applied to the paperboard at a solids
concentration of 6% or 8%. Films of several different thicknesses were
used. The method of coating and drying was the same as described
above in Example 1, as was the method of measuring grease resistance
(Kit Number). Table 4 shows film thicknesses, product application rates
and Kit Numbers resulting from coatings placed on uncoated (1 - 8) and
coated (9 - 12) paperboard.
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Table 4: Grease resistance of 190# white paperboard with and
without a latex polymer/filler precoat and with different application rates of
a wax/PVOH/polyamine second coating.
COATING APPLICATION RATE
DRY
FILM SOLIDS DRY COATING
TEST ROD THICKNESS (Ibs/3000 SOLIDS FORMULATION KIT
NO. NO. (IN.) ft2) (lbs/ton) (Ibs/ton)a NUMBER
UNCOATED 190# WHITEBOARD
0UN - - 0 0 0 0
1 6 .00060 0.56 5.896 25.64 0
2 10 .00100 0.94 9.827 42.73 0
3 15 .00150 1.40 14.740 64.09 0
4 20 .00200 1.87 19.654 /85.45 1
25 .00250 2.34 24.567 106.82 1
6 30 .00300 2.81 29.481 128.18 2
7 20 .00200 2.50 26.205 113.94 2
8 30 .00300 3.74 39.308 170.90 3
COATED 190# WHITEBOARD
OCO - 0 0 0 0 0
9 6 .00060 0.56 5.896 25.64 4
10 .00100 0.94 9.827 42.73 5
11 15 .00150 1.40 14.740 64.09 8
12 20 .00200 1.87 19.654 85.45 12
Notes:
a. This refers to the number of pounds of a formulation of the
wax/PVOH/polyamine coating at 23% solids in water that was applied per,
ton of dry paper. That formulation was diluted further prior to application
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with water to 6% solids for tests 1- 6 and 9 - 12 and to 8% solids for tests
7 and 8.
b. OUN refers to uncoated paperboard with no
wax/PVOH/polyamine coating; OCO refers to coated paperboard with no
wax/PVOH/polyamine coating.
[00108] The results of this test showed that while the application of a
coating comprising wax, PVOH, and polyamine improved the grease
resistance of the uncoated whiteboard from 0 Kit number to about 3, as
the application rate of the coating formulation increased up to about 170
lbs of the 23% actives formulation/ton of paper (about 39 lbs dry solids/ton
of paper), the application of the same coating at a much lower level to pre-
coated whiteboard provided unexpectedly superior increases in grease
resistance. Coated whiteboard without the subsequent
wax/PVOH/polyamine coating had a Kit number of 0. However, the
grease resistance of the board increased significantly in a dose-responsive
manner up to a Kit number12 at a coating rate of about 19.8 lbs dry
solids/ton of paper of the wax/PVOH/polyamine coating (about 85 lbs of
the 23% actives formulation/ton of paper).
[00109] Based on the results shown in Example 1, it is believed that the
treatment of a pre-coated porous material with a wax/PVOH coating,
without the use of the optional polyamine, would also be useful in
increasing the grease resistance of the pre-coated material.
[00110] The discussion of the references herein is intended merely to
summarize the assertions made by their authors and no admission is
made that any reference constitutes prior art. Applicants reserve the right
to challenge the accuracy and pertinency of the cited references.
[00111] In view of the above, it will be seen that the several advantages
of the invention are achieved and other advantageous results obtained.
[00112] As various changes could be made in the above methods and
compositions by those of ordinary skill in the art without departing from the
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scope of the invention, it is intended that all matter contained in the above
description shall be interpreted as illustrative and not in a limiting sense.
In addition it should be understood that aspects of the various
embodiments may be interchanged both in whole or in part.
34
