Note: Descriptions are shown in the official language in which they were submitted.
CA 02517716 2005-08-31
WO 2004/074351 PCT/US2004/004048
STARCH-LOADED POLYVINYL ALCOHOL COPOLYMER FILM
FOR PACKAGING NON-LIQUID PRODUCT AND
METHOD FOR MAKING THE SAME
TECHNICAL FIELD
The present invention relates generally to water-soluble polyvinyl
alcohol (PVOH) film. More specifically, the present invention relates to water-
soluble
PVOH film with particular applications for packaging of non-liquid products,
such as
cleansers, conditioners, disinfectants, and the like.
BACKGROUND
Polyvinyl alcohol (PVOH) is a synthetic resin generally prepared by the
alcoholysis, usually termed hydrolysis or saponification, of polyvinyl
acetate. Fully
hydrolyzed PVOH, where virtually all the acetate groups have been converted to
alcohol groups, is a strongly hydrogen-bonded, highly crystalline polymer
which
dissolves only in hot water-greater than about 140° F (60° C).
If a sufficient number
of acetate groups are allowed to remain after the hydrolysis of polyvinyl
acetate, the
PVOH polymer then being known as partially hydrolyzed, it is more weakly
hydrogen-
bonded and less crystalline and is soluble in cold water-less than about
50° F (10° C).
Both fully and partially hydrolyzed PVOH types are commonly referred to as
PVOH
homopolymers although the partially hydrolyzed type is technically a vinyl
alcohol-
vinyl acetate copolymer.
The term PVOH copolymer is generally used to describe polymers that
are derived by the hydrolysis of a copolymer of a vinyl ester, typically vinyl
acetate,
and another monomer. PVOH copolymers can be tailored to desired ftlm
characteristics by varying the kind and quantity of copolyrnerized monomers.
Examples of copolymerizations are those of vinyl acetate with a carboxylic
acid or
with an ester of a carboxylic acid. Again, if the hydrolysis of acetate groups
in these
copolymers is only partial, then the resulting polymer could be described as a
PVOH
terpolymer-having vinyl acetate, vinyl alcohol, and carboxylic acid groups-
although
it is commonly referred to as a copolymer.
CA 02517716 2005-08-31
WO 2004/074351 PCT/US2004/004048
It is known in the art that many PVOH copolymers, because of their
structure, can be much more rapidly soluble in cold water than the partially
hydrolyzed
type of PVOH homopolymers. Such copolymers have therefore found considerable
utility in the fabrication of packaging films for the unit dose presentation
of various
liquid and powdered products including agrochemicals, household and industrial
cleaning chemicals, laundry detergents, water treatment chemicals, and the
like.
The manufacture of packaging films for liquid products poses a unique
concern, as they must be free of bubbles and pin holes, and capable of
resisting
problems such as physical incompatibility exemplified by "weeping"-a condition
whereby the package contents seep from the film over a prolonged storage
period-
caused by certain components typically used in liquid detergent products. The
increased level of quality required to manufacture a film and package such
liquids adds
significantly to the packaged product cost.
Conversely, powdered products are far more forgiving when it comes to
packaging. Pin holes and micro bubbles in the film do not present problems for
packaging powdered products. Physical compatibility is less problematic, due
in part
to the non-existence of migrating materials in powdered detergents. Weeping
does not
commonly occur with the packaging of powdered products. For these reasons the
type
and quality of PVOH film used to package powered products can be significantly
varied from that for the liquid counterparts.
However, those in the powdered product industry have been directed
toward the use of either the higher quality, more expensive PVOH copolymer
films
designed for liquid product packaging or inferior films such as less diverse
and more
slowly soluble homopolymer-based films including films produced by blown
extrusion.
The present invention has solved this problem of film quality versus
manufacturing cost as it relates to packaging of powdered product, as well as
other
problems faced by those in the industry. By making a less expensive PVOH
copolymer film having good water-soluble qualities, those in the industry have
an
alternative source for packaging powdered products.
2
CA 02517716 2005-08-31
WO 2004/074351 PCT/US2004/004048
SUMMARY
A water-soluble film suitable for packaging a non-liquid product,
including the method for preparing the film composition and packaging for the
non-
liquid product, is disclosed. In one particular embodiment of the invention,
the film
combination comprises a hydrolyzed copolymer of vinyl acetate and methyl
acrylate in
the range of from about 30 to about 95 percent by weight, modified starch in
the range
of from about 4 to about 30 percent by weight, plasticizer in the range of
from about 5
to about 30 percent by weight, lubricant/release agent in the range of from
about 0.0 or
about 0.01 to about 1.5 percent by weight, and surfactant in the range of from
about
0.01 to about 1.5 percent by weight.
In a preferred embodiment of the invention, the film composition
utilizes a bleaching agent to prevent color drift, such as browning, of a
polymer
solution used to cast the film. Oxidizing bleaching agents (e.g., chlorine,
chlorinated
compounds, oxygen, and oxygenated compounds) and reducing bleaching agents
(e.g.,
hydrosulfites, borohydrides, and metabisulfites) are preferred. Examples
include
sodium percarbonate, sodium persulfate, peracetic acid, sodium hydrosulfite
and
sodium metabisulfite. Sodium percarbonate and sodium metabisulfite are
preferred,
and sodium metabisulfite is most preferred.
Preferably the agent comprises sodium metabisulflte in an amount in
the range of from about 0.12 to about 1.0 percent by weight. Most preferably,
the
sodium metabisulfite is used in an amount in the range of from about 0.4 to
about 0.7
percent by weight.
A preferred method for preparing a water-soluble copolymer film for
packaging of a non-liquid product is also disclosed and claimed. The method
comprises the steps of copolymerizing vinyl acetate and methyl acrylate to
form a
copolymer, hydrolyzing the vinyl acetate-methyl acrylate copolymer to form a
vinyl
alcohol-gamma lactone copolymer having a 4% solution viscosity in the range of
from
about 5 to about 50 cps at 20° C, slurrying the hydrolyzed polymer with
water, adding
modified starch to the copolymer-water slurry in an amount of from about 4.0
to about
25.0 percent by weight, heating the hydrolyzed copolymer and starch slurry to
form a
CA 02517716 2005-08-31
WO 2004/074351 PCT/US2004/004048
solution, treating the solution with caustic soda to create a solution of a
copolymer
having from about 1 to about I2 mol percent carboxylate groups, from about 0
to about
11 mol percent gamma lactone nits, and from about 88 to about 99 mol percent
vinyl
alcohol units, and then casting the hot copolymer solution on a suitable
surface to
create a film having a thickness in the range of from about 0.1 to about 5.0
mils (about
0.0025 to about 0.127 mm).
A package for containing a non-liquid product is also disclosed. A
preferred package comprises at least one compartment comprised of a water-
soluble
film comprising from about 30 to about 95 percent by weight of a hydrolyzed
copolymer of vinyl acetate and methyl acrylate, from about 4 to about 30
percent by
weight of modified starch filler, from about 5 to about 30 percent by weight
of
plasticizer, and from about 0.01 to about 1.5 percent by weight of a
surfactant.
In one embodiment the package may be used to deliver a unit dose of a
non-liquid agent. The preferred unit dose comprises a package comprising a
water-
soluble film comprising from about 40 to about 90 percent by weight of a
hydrolyzed
copolymer of vinyl acetate and methyl acrylate, from about 4 to about 30
percent by
weight of a modified starch filler, from about 5 to about 30 percent by weight
of a
plasticizer, and from about 0.01 to about 1.0 percent by weight of a
surfactant, and a
non-liquid agent contained within the package. The non-liquid agent may be a
cleanser, a disinfectant, a polish, a conditioner, or the like.
Further aspects and advantages will be apparent to those of ordinary
slcill in the art from a review of the following detailed description, taken
in conjunction
with the drawings. While the film, package, and methods are susceptible of
embodiments in various forms, the description hereafter includes specific
embodiments
with the understanding that the disclosure is illustrative, and is not
intended to limit the
invention to the specific embodiments described herein.
BRIEF DESCRIPTION OF THE DRAWINGS
The embodiments described herein can be more readily understood with
reference to the appended drawing figures where:
4
CA 02517716 2005-08-31
WO 2004/074351 PCT/US2004/004048
FIGURE 1 is a perspective view of a test apparatus used to analyze the
water disintegration and dissolution of film samples;
FIGURE 2 is a perspective view of the test apparatus and test set-up
illustrating the procedure for analyzing the water-solubility of film samples;
and
FIGURE 3 is a top view of the test set-up of FIGURE 2.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
While the invention is susceptible of embodiment in many different
forms, this disclosure will describe in detail preferred embodiments of the
invention
with the understanding that the present disclosure is to be considered as an
exemplification of the principles of the invention and is not intended to
limit the broad
aspect of the invention to the embodiments illustrated.
Film Composition:
The present invention includes a water-soluble film for packaging a
non-liquid product. The following is a list of terms used throughout the
application:
"Non-liquid" shall refer to any product that has as a component a form
characteristic of a solid, including but not limited to powder, caked,
shaving, solid, gel,
slurry, paste, pelletized, and the like.
"Package" or "packaging" shall refer to any receptacle or method
suitable for holding or enclosing, to a substantial degree, a quantity of non-
liquid
product, without regard to size, shape, or the number of parts used to form
the
container or carry out the method.
Further, all ranges set forth herein include all possible subsets of ranges
and any combinations of such subset ranges. Ranges are inclusive of the stated
endpoints.
The film is based on an amount of a hydrolyzed copolymer of vinyl
acetate and methyl acrylate and is a vinyl alcohol-gamma lactone copolymer, in
the
range of from about 30 to about 95 percent by weight. Preferably, the amount
of
copolymer is in the range of from about 50 to about 85 percent by weight. The
5
CA 02517716 2005-08-31
WO 2004/074351 PCT/US2004/004048
copolymer may be prepared in any manner known by those skilled in the art. A
particularly suitable copolymer is sold by E.I. duPont de Nemours under the
tradename ELVANOL. The ELVANOL range of water-soluble synthetic polymers has
excellent film-forming, emulsifying, and adhesive properties. Such polymers
offer
resistance to oil, grease and solvents, plus high tensile strength,
flexibility, and high
oxygen barrier.
Alternatively, and less preferably, a vinyl acetate-methyl acrylate
copolymer must first undergo hydrolysis (also called alcoholysis) to form a
vinyl
alcohol-gamma lactone copolymer. The vinyl alcohol-gamma lactone copolymer
preferably has a 4% solution viscosity in the range of from about 5 to about
50 cps
(0.005 to 0.050 pascal seconds) at 20° C (68° F). More
preferably the vinyl alcohol-
gamma lactone copolymer has a 4% solution viscosity in the range of from about
8 to
about 35 cps (0.008 to 0.035 pascal seconds) and, most preferably, the vinyl
alcohol-
gamma lactone copolymer has a 4% solution viscosity in the range of from about
15 to
about 25 cps (0.015 to 0.025 pascal seconds).
The hydrolyzed copolymer initially comprises an amount of gamma
lactone units preferably from about 2 to about 12 mol percent, more preferably
from
about 4 to about 6 mol percent. Modified starch is added to the hydrolyzed
copolymer,
which preferably is first slurried with water, in an amount in the range of
from about 4
to about 30 percent by weight, preferably about 4 to about 12 percent by
weight.
While other modified starches may be suitable, the preferred modified starch
is
hydroxyethyl modified starch in an amount of about 10 percent by weight. In
another
embodiment, the amount of starch is at least 5 percent by weight.
The composition also comprises plasticizer, such as in the range of from
about 5 to about 30 percent by weight, preferably about 10 to about 20 percent
by
weight, or preferably in the range of from about 20 to about 30 percent by
weight when
sorbitol is present as a plasticizer.
The composition also preferably comprises lubricant/release agent in the
range of from about 0.0 to about 1.5 percent by weight, and surfactant in the
range of
from about 0.01 to about 1.5 percent by weight. Other suitable components,
such as
6
CA 02517716 2005-08-31
WO 2004/074351 PCT/US2004/004048
additional plasticizers, lubricants, and release agents, fillers, extenders,
antiblocking
agents, detackifying agents, antifoams and other functional ingredients, may
be added
in proper amounts to achieve a desired effect to the extent such components do
not
inhibit other desired characteristics of the copolymer film.
The copolymer solution preferably is treated with caustic soda (sodium ,
hydroxide), to yield a copolymer solution having from about 1 to about 12 mol
percent,
preferably from about 2 to about 6 mol percent, and most preferably from about
3 to
about 4 mol percent carboxylate groups, from 0 to about 11 mol percent,
preferably
from 0 to about 5 mol percent, and most preferably from about 1 to about 2 mol
percent gamma lactone units, and from about 88 to 99 mol percent, preferably
from
about 92 to about 98 mol percent, and most preferably from about 94 to about
96 mol
percent vinyl alcohol units.
The copolymer solution is then cast to create a film having a thickness
in the range of from about 0.5 mils to about 5.0 mils (about 0.013 to about
0.127 mm).
The film thickness can have a direct effect on the speed at which the final
product will
dissolve in water, with thin films (e.g., less than 3.0 mil or 0.076 mm)
completely
dissolving in less time. Conversely, thinner films typically provide less
structural
protection than their thicker film counterparts. A balance must be struck
between these
and other factors. For many applications, a preferable film thickness is in
the range of
from about 0.5 to about 3.0 mils (about 0.013 to about 0.076 mm), and most
preferably
in the range of from about 1.0 to about 2.0 mils (about 0.025 to about 0.050
mm).
During preparation of the copolymer solution a browning effect can
occur. It is desirable in most applications that the water-soluble film have a
clear and
colorless appearance. To combat this, and any other known color drift to which
the
copolymer solution may be susceptible, a suitable bleaching agent can be added
to the
copolymer solution. The use of sodium metabisulfite has been found to
substantially
maintain the solution clarity and colorlessness during preparation when used
in an
amount in the range of from about 0.12 to about 1.0 percent by weight, most
preferably
in an amount from about 0.4 to about 0.7 percent by weight.
7
CA 02517716 2005-08-31
WO 2004/074351 PCT/US2004/004048
Suitable plasticizers include, but are not limited to, glycerin, diglycerin,
sorbitol, ethylene glycol, diethylene glycol, triethylene glycol,
tetraethylene glycol,
propylene glycol, polyethylene glycols up to 400 MW, neopentyl glycol,
trimethylolpropane, polyether polyols and ethanolamines. Preferred
plasticizers are
glycerin, triethyleneglycol, propylene glycol and trimethylolpropane.
Suitable surfactants may include the nonionic, cationic, anionic and
zwitterionic classes. Preferably, the surfactants will be of the nonionic,
cationic or
zwitterionic classes or combinations of these. Suitable surfactants include,
but are not
limited to, polyoxyethylenated polyoxypropylene glycols, alcohol ethoxylates,
alkylphenol ethoxylates, tertiary acetylenic glycols and alkanolamides
(nonionics),
polyoxyethylenated amines, quaternary ammonium salts and quaternized
polyoxyethylenated amines (cationics), and amine oxides, N-alkylbetaines and
sulfobetaines (zwitterionics). Preferred surfactants are alcohol ethoxylates,
quaternary
ammonium salts and amine oxides.
Suitable lubricants/release agents include, but are not limited to, fatty
acids and their salts, fatty alcohols, fatty esters, fatty amines, fatty amine
acetates and
fatty amides. Preferred lubricants/release agents are fatty acids, fatty acid
salts, and
fatty amine acetates.
Suitable fillers/extenders/antiblocking agents/detackifying agents
include, but are not limited to, starches, modified starches, crosslinlced
polyvinylpyrrolidone, crosslinlced cellulose, microcrystalline cellulose,
silica, metallic
oxides, calcium carbonate, talc and mica. Preferred materials are starches,
modified
starches and silica. If used, the preferred amount of such
filler/extender/antiblocking
agent/detackifying agent in the water-soluble film of the present invention is
between
0.1 % and 25% by weight, more preferably between 1 % and 15% by weight, and
preferably between 1% and S% by weight if starch is absent.
Suitable antifoams include, but are not limited to, those based on
polydimethylsiloxanes and hydrocarbon blends. If used, the preferred amount of
antifoam in the water-soluble film of the present invention is between 0.001 %
and
0.5%, more preferably between 0.01% and 0.1% by weight.
8
CA 02517716 2005-08-31
WO 2004/074351 PCT/US2004/004048
Film Formation:
The preferred method for preparing the water-soluble copolymer film
comprises the steps of copolymerizing vinyl acetate and methyl acrylate to
form a
copolymer. Alternatively, this vinyl acetate-methyl acrylate copolymer may be
more
readily purchased. In either case, the next steps include hydrolyzing the
vinyl acetate-
methyl acrylate copolymer to form a vinyl alcohol-gamma lactone copolymer
having a
4% solution viscosity in the range of from about 5 to about 50 cps at
20°C, and
slurrying the hydrolyzed polymer with water while adding modified starch to
the
copolymer-water slurry in an amount of from about 4.0 to about 25.0 percent by
weight. Preferably the amount of modified starch is about 4 to about I2
percent by
weight. The hydrolyzed copolymer and starch slurry is then heated to boiling
point to
form a solution.
The solution is then treated with caustic soda to create a solution of a
copolymer having from about 1 to about 12 mol percent carboxylate groups, from
about 0 to about 11 mol percent gamma lactone units, and from about 88 to
about 99
mol percent vinyl alcohol units. More preferable ranges have been previously
stated.
The next step is maintaining the solution at a temperature in the range of
from about
160° F to about 200° F (about 71°C to about 93°C),
and then casting the hot copolymer
solution on a suitable surface to create a film having a thickness in the
range of from
about 0.1 to about 5.0 mils (about 0.0025 to about 0.127mm).
The treated solution can undergo browning while being held at high
temperatures. This is undesirable for most applications, wherein a clear film
is sought.
Therefore, the method can further comprise the step of adding a bleaching
agent, such
as sodium metabisulfite, in an amount greater than 0.12 percent by weight to
substantially reduce or prevent browning of the heated solution. Most
preferably, a
bisulfate is added in the amount of from about 0.4 to about 0.7 percent by
weight.
The resulting film can then be formed into a package for containing a
non-liquid product, as previously described. Steps for forming a suitable
package are
known by those skilled in the art for similar handling films, or can be
derived without
undue experimentation. A preferred requirement of the film, and therefore the
formed
9
CA 02517716 2005-08-31
WO 2004/074351 PCT/US2004/004048
package, is that it be capable of complete dissolution in water in a
relatively short
period of time. A preferred film of the present invention, at a thickness of
about 1.5
mil (about 0.038 mm), dissolves in water at a temperature of about 20°C
in less than 60
seconds.
The following test procedure, referred to herein as MonoSol Test
Method 205 (MSTM 205), is used to determine the time required for a water-
soluble
film to break apart (disintegrate) and its subsequent relative dissolution
time when held
stationary. The test procedure is disclosed with reference to drawing FIGURES
1-3.
MonoSol Test Method 205 (MSTM 205)
APPARATUS AND MATERIALS.
600 mL Beaker 12
Magnetic Stirrer 14 (Labline Model No. 1250 or equivalent)
Magnetic Stirring Rod 16 (5 cm)
Thermometer (0 to 100° C, ~ 1 ° C)
Template, Stainless Steel (3.8 cm x 3.2 cm)
Timer, (0-300 seconds, accurate to the nearest second)
Polaroid 35mm Slide Mount 20 (or equivalent)
MonoSol 35mm Slide Mount Holder 25 (or equivalent, see FIGURE 1)
Distilled Water
TEST SPECIMEN:
1. Cut three test specimens from film sample using stainless steel
template (i.e., 3.8 cm x 3.2 cm specimen). If cut from a film web, specimens
should
be cut from areas of web evenly spaced along the transverse direction of the
web.
2. Lock each specimen in a separate 35 mm slide mount 20.
3. Fill beaker 12 with 500 mL of distilled water. Measure water
temperature with thermometer and, if necessary, heat or cool water to maintain
temperature at 20° C (about 68° F).
4. Mark height of column of water. Place magnetic stirrer 14 on base
27 of holder 25. Place beaker 12 on magnetic stirrer 14, add magnetic stifling
rod 16 to
CA 02517716 2005-08-31
WO 2004/074351 PCT/US2004/004048
beaker 12, turn on stirrer 14, and adjust stir speed until a vortex develops
which is
approximately one-fifth the height of the water column. Mark depth of vortex.
5. Secure the 35 mm slide mount 20 in the alligator clamp 26 of the
MonoSol 35mm slide mount holder 25 (FIGURE 1) such that the long end 21 of the
slide mount 20 is parallel to the water surface, as illustrated in FIGURE 2.
The depth
adjuster 28 of the holder 25 should be set so that when dropped, the end of
the clamp
26 will be 0.6 cm below the surface of the water. One of the short sides 23 of
the slide
mount 20 should be next to the side of the beaker 12 with the other positioned
directly
over the center of the stirring rod 16 such that the film surface is
perpendicular to the
flow of the water, as illustrated in FIGURE 3.
6. In one motion, drop the secured slide and clamp into the water and
start the timer. Disintegration occurs when the film breaks apart. When all
visible film
is released from the slide mount, raise the slide out of the water while
continuing to
monitor the solution for undissolved film fragments. Dissolution occurs when
all film
fragments are no longer visible and the solution becomes clear.
DATA RECORDING:
The results should include the following:
~ complete sample identification;
~ individual and average disintegration and dissolution times; and
~ water temperature at which the samples were tested.
Standard quality control procedures may be followed for water-soluble
PVOH film, with respect to bubble and pin-hole inspection, however, such
quality
checks are not absolutely necessary given the solid state of the contained
product. A
unit dose of a non-liquid agent contained within the formed package does not
necessarily pose the same packaging problems as a liquid product. With respect
to the
use of such a unit dose, however, no procedural changes are required. That is,
merely
adding the unit dose package to the appropriate quantity of water and
following the
11
CA 02517716 2005-08-31
WO 2004/074351 PCT/US2004/004048
necessary stirring or agitation times yields the desired cleaning,
conditioning, or
disinfectant solution.
While specific embodiments have been illustrated and described,
numerous modifications are possible without departing from the spirit of the
invention.
12
