Note: Descriptions are shown in the official language in which they were submitted.
WO 92/17382 '~' PCT/GB92/00603
- 1 -
WATER SOLUBLE PACKAGE
This invention relates to a water soluble or water
dispersible package containing an agrochemical, eg a pesticidal
composition, and to a process for producing such a package.
Agrochemicals include pesticides, e.g. herbicides,
which are often potentially harmful materials and are commonly
produced as a concentrated solution or dispersion in an organic
liquid, as a gel or in solid form. Such chemicals are
typically supplied in a metal or blow-moulded plastics
container. To use chemical pesticides, e.g. herbicides, a
quantity of the pesticide is measured out of the container in
concentrated form and then mixed with a large volume of water
before being sprayed onto a locus to be treated or onto plants.
Such concentrated materials are frequently highly toxic so
great care must be taken in measuring and mixing them to avoid
spillage and to avoid human or animal contact with the
concentrated pesticide.
Efforts have been devoted to the design of containers to
minimise the risk of accidental spillage of their contents when
used and also to reduce residues remaining in the containers
after use. Plastics containers with wide necks to facilitate
pouring of their contents have been used. Blow moulded
plastics containers having hollow handles have been made in
which the hollow handles are isolated from the.body of the
container to avoid retention of material in the handle.
Nevertheless, with present packages it is relatively easy
to spill the contents during the mixing process with the
resulting risk of contamination of the environment and risl~: of
contact with humans or animals. Also, it is relatively rare to
WO 92/17382 - z - PCT/GB92/006r''
empty containers so that farmers, and other users, tend to have
partly full containers left around. These represent a further
hazard. Even when all of the contents have been used it is
difficult to dispose of the empty container. It is also
difficult to wash adequately the containers and measuring
instruments in which the concentrated pesticides are handled.
These devices represent a further hazard to personnel and to
the environment.
It has been proposed to package agricultural
chemicals in a container comprising a screw fitting adapted to
screw onto a corresponding fitting on a spray tank. The
contents of the container should be released only when a
satisfactory seal exists between the tank and the, container.
Practical difficulties exist in securing widespread use of such
a system in view of the need for standardisation of screw
fitting sizes and the possibility of leakage if a satisfactory
tight seal is not achieved.
It has also been proposed to package chemicals in a
water soluble container which releases the packaged chemical
only after contact with water. Thermoplastic polyvinyl alcohol
compositions which are resistant to strong acids are described
in European Patent No 155606. Such applications have however
been limited by the capabilities of known water soluble
containers which are often too prone to rupture. It has also
proved difficult to avoid pinholes at heat-sealed joints in
containers leading to leaking of the contents and unacceptable
weakness in the material of the container adjacent to heat
sealed joints.
The present invention seeks to overcome the
disadvantages of known packages and to provide a package which
contains an agrochemical such as a pesticidal composition and
CA 02107341 2002-10-29
has one or more of the following advantageous features:
the packaged chemical is released onl~a aster
L.ont~Ct W1 th Wcve~' ? T3 Wh~C.'1 1t 1S tC be ~15SO~Ved or diS~e2'S2d,
minimising the possiility of accidental contact of the
undiluted material With the environment or with humans or
animals;
the chemical can be provided in unit dosage fot-m
suitable for dilution with a predetermined amount of water
removing the ne=d =or undiluted chemical tc ae measu==d gut;
the packaged c'r~rmica? is eas; to use . the packaged
i.I~aem.'~C'e..~1 can ire 51~~1~1 p~~Wd :': ~T~.t~~ yr3o' to ~.1SE L'~f the
chem:.cais; and
.1 ? nBet°.4 ~or WaS hlng Jur i.'a the .-s=1"1.u$~ ::aeml.~r~~
om ~ "325 tC' r~i7d~°r v:l~'m Saes ~Or d.'..SpOSa~. 1S Y'"'c~~='!~C:
,..DT:L~r.a
con rain=_r s ~.~h i ch have 3~een i n cos. tact with the package?
~.I:,~II17.~~' remain uncun'am~na~~d which y~cl~?tSt~S th°_',.~
=.St.oSa~ .
~11~ haV~? ~~i~7 deV.SBCi ~ i7w°.'vi ~~c:~.aC.~~ ieri"?.1~h d_SS~viVe~
is. wa=er, may be cheaply and easily produced and is
unexpectedly strong and resistant to rupture or breakage.
accordingly the present invention provides a
;package containing an agrochemical, eg a pesticidal
vomposition, which package comprises a first sheet ~i non-
alanar Water soluble or water dispersible material-and a second
sheet of water salubl~ or water-dispersible material superposed
on the first sheet and sealed to it by a Continuous closed
Water soluble or wet°-r disp°-rsibl°- seal along a
continuous
CA 02107341 2002-10-29
-4-
region of the superposed sheets wherein the seal is a
heat seal and is free from any angular intersections with
itself.
The continuous region of the superposed sheets is
preferably substantially planar.
The invention further provides a process for
producing a package containing an agrochemical which
package comprises a first sheet of non-planar water
soluble or water dispersible material and a second sheet
of water soluble or water dispersible material superposed
on the first sheet and sealed to it by a continuous
closed water soluble or water dispersible seal along a
continuous region of the superposed sheets which process
comprises:
moulding a first, sheet of water soluble or water
dispersible material to form a non-planar sheet
comprising at least one recess adapted to retain an
agrochemical, eg a pesticidal composition, said recess
being bounded by a flange, which flange is preferably
substantially planar;
placing an agrochemical, eg a pesticidal composition
in the at least one recess;
placing a second sheet of water soluble or water
dispersible material on the flange and across the or
every recess; and
sealing the first and second sheets along the flange
to form a continuous closed water soluble or water
dispersible seal
wherein the sealing is performed by heat sealing.
The agrochemical may be, for example, a plant
protection agent, a plant growth regulator or a plant
nutrient. An example of a plant protection agent is a
pesticide (such as an insecticide, fungicide, herbicide,
acaricide or nematocide).
The agrochemical composition may be in liquid form,
CA 02107341 2002-10-29
-4a-
or solid form, or gel form. It may comprise any
conventio~aal carrier or diluent or surfactant. Where the
composition is in liquid form it may be in the form of a
solution or of a dispersion in an organic liquid. e.g. an
emulsion or a suspension. Similarly in gel form, the
composition may contain agrochemical either dissolved or
dispersed in the substantially
WO 92/1?382 ~ 1 ~ j ~ ~~ .~ PCT/GB92/00603
_ 5 _
dry medium.
The packages of the present invention generally
contain from 0.1 grams to 7kg, preferably 1g to 5kg, where the
composition is in solid form. Where the composition is in
liquid or gel form, the package typically contains from lml to
litres, preferably from 0.5 to 5 litres (0.1 litres to 1.5
litres is especially preferred); on a smaller scale a range of
5m1 to 1 litre is also useful.
Generally the package will contain at least a small
10 amount of space, eg at least about 5% by volume, so as to
minimise the likelihood of spillage of the composition during
the production of the package.
Particularly when the contents of the package are
solid, for example as a powder or granules, it may be
advantageous to ensure that the package produced is evacuated
of air or the contents are under reduced pressure. The package
thus produced has a number of advantages, for example
substantially increased resistance to shock. A powder or
granules in such a package is compacted and is, effectively,
2o skin-packaged within the film. Compaction of the product makes
the package more likely to sink when dropped into water and the
package occupies less space during storage. Thus, the
advantages of packaging under reduced pressure include:
a) the absence of gas surrounding the agrochemical
composition reduces the possibility of the package failing for
example, at low temperatures. Normally at low temperatures, eg
close to 0°C, water soluble plastics films, for example
polyvinyl alcohol, forming a package become brittle and
therefore the package becomes more likely to fail. Reducing
CA 02107341 2002-10-29
- 6 -
the space in which the agrochemical composition contained by
the package can move about reduces the likelihood of the
package failing;
b) where the agrochemical composition is in the form
of granules, the likelihood of the granules breaking down into
dust within the package (which can lead for example to the
active ingredient decomposing) is reduced when the package is
skin-tight;
c) the density of the package can be altered according
to the extent to which the package is under reduced pressure.
This offers further advantages, for example in increasing the
speed of dissolution of the package by ensuring that the
package sinks when placed for example in a spray tank;
d) where the agrochemical is a particulate solid which
does not comprise a binding agent, such as a plasticiser, it
may be advantageous for the package to hold the agrochemical
substantially rigid within the package to prevent segregation
and possible decomposition of the agrochemical (which may be
incompatible with certain plasticisers: the plasticiser in the
agrochemical may also be incompatible with the film).
Typically the two sheets of water soluble or water
dispersible material are of the same material, but they may be
different. One sheet of the water soluble or water dispersible
material may be easy to print upon.
When the agrochemical composition is in liquid or gel form
and comprises an organic solvent the water soluble or water
dispersible material will be one which is insoluble in the
organic solvent.
Suitable water soluble or dispersible materials are
CA 02107341 2002-10-29
_ 7 _
polyethylene oxide and methyl cellulose. More preferably a
polyvinyl alcohol (PVOH) film is used. Such a PVOH film may be
a partially or fully alcoholised or hydrolysed e.g.40-99%,
preferably 70-92% alcoholised or hydrolysed, polyvinyl acetate
film. The film may be a cast film or, more preferably. a blown
or extruded film.
The polyvinyl alcohol film may be unoriented, mono-
axially oriented or bi-axially oriented. Water soluble
materials are preferred since they provide less disposal
l0 problems. The materials used will generally be cold water
soluble; cold water soluble polyvinyl alcohol is preferred. It
will be understood that other materials may be used when the
package is to be dissolved or dispersed in water or hot water.
Generally the water soluble or water dispersible material will
be flexible.
The maximum tensile strength of the material of the
envelope is preferably at least 20, more preferably from 30 to
80, N/mm~ and may be as much as 200N/mm~ or more; and the
elongation at break is preferably 200 to 380%, more preferably
from 220 to 350% and may be as much as 500 per cent or more.
Testing for these values is generally carried out at 23°C and
50% relative humidity.
When the agrochemical composition is in liquid or gel
form it is particularly important to avoid pinholes in the
package through which leakage of the composition may occur. In
such cases therefore the water soluble or water dispersible
material will typically be a laminate, generally of two layers
of different or preferably the same water soluble or water
dispersible material, as pinholes are unlikely to coincide in
CA 02107341 2002-10-29
two layers of material. Typically the laminates will consist
of 2 layers of thickness from 20~sm to imm, preferably about
40um, each. Generally however the thickness of the layers
will be kept to the minimum needed to prevent rupture of the
package, so that the water soluble or dispersible material is
dissolved or dispersed as quickly as possible and the agrochemical
then released.
When the agrochemical composition is in solid form,
the sheets of water soluble or water dispersible material
to typically comprise a single layer of material. In such case
the material will generally be from 20 to 500um, preferably 30
to 100~em, thick. However, in cases where it is particularly
desirable to avoid pinholes in the package, eg. to prevent the
escape of unpleasant odours, a laminate material of the type
described above may be used. As with packages containing
liquids and gels, the thickness of the water soluble
dispersible material will generally be kept to a minimum in
packages containing solid compositions.
When the packages are produced by thermoforming, as
is preferred, the thickness of the first sheet will generally
not be less than 20~ and (to maintain ease of processing)
generally not more than 1 mm. A preferred range is from
80-400u, eg 100-400u, most preferably about 250u..
The thickness of the second sheet may be less than that
of the first sheet as the second sheet will not generally be
thermoformed so that localised thinning of the sheet will not
occur. The thickness of the second sheet will generally not be
less than 10~, preferably not less than 20u. For ease of
processing the film will generally not be more than 1 mm thick,
CA 02107341 2002-10-29
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a preferred range being from 20~ to 250u, most preferably about
150u.
In a particular embodiment the package is provided with a
region which will more readily dissolve in water than the rest
of the package. This offers advantages, for example by
speeding up the dispersion of the agrochemical contained in the
package. The region may be provided for example by making one
sheet of the water-soluble or water dispersible material
thinner than the other, or by making one portion of the package
thinner than the rest.
In the packages of the present invention, the package
does not possess a seam running down the centre of one of the
faces of the package. This offers advantages over known
packages, for example by reducing the likelihood of failure
occurring in the package when it is subjected to shock, because
packages having a seam running down the centre of one of the
faces of the packages necessarily have a point at which two or
more seals intersect which will be more likely to fail under
shock than the eguivalent package not having this point of
intersection.
The two water soluble or water dispersible sheets
in the packages are sealed together by a closed continuous
heat seal. To ensure that the seal does not suffer from leakage,
it is a single continuous seal and has no geometrical dis-
continuities, i.e. it does not comprise any angular inter-
sections with itself. Therefore the heat seal will usually
be curved, at least in portions, for instance at the corners of the
package: the radius of curvature of the heat seal will generally
not be less than lmm,
CA 02107341 2002-10-29
preferably not less than 5mm, and not more than half the width
of the package.
Suitable agrochemicals which may be used in the
package of the present invention include fungicides,
insecticides and herbicides (for example hydroxybenzonitrile
herbicides, e.g. bromoxynil or ioxynil or derivatives thereof
such as salts or esters, e.g. heptanoates or octanoates).
Molluscicides, suitable for addition to, for example, ponds or
streams may also be employed.
The invention is not limited to specific agrochemicals.
Agrochemicals which can be used in the invention include:
Fungicides such as Triadimefon, Tebuconazole, Prochloraz,
Triforine, Tridemorph, Propiconazole, Pirimicarb, Iprodione,
Metalaxyl, Bitertanol, Iprobenfos, Flusilazole, Fosetyl,
Propyzamide, Chlorothalonil, Dichlone, Mancozeb, Anthraquinone,
Maneb, Vinclozolin, Fenarimol, Bendiocarb, Captafol, Benalaxyl,
Thiram, Captan, Fosetyl-A1, Zineb, Sulfur, Quintozene, Copper
salts, Thiophanate-methyl, Tricyclazole, Dichloran, Chloroneb,
Cyproconazole, Hexaconazole, Imazalil, Dodine, Diniconazole,
Guazatine, Thiabendazole, Carboxin, Ferban, Glyodin, Fentin
(triphenyltin), Terrachlor, Terrazole and Benomyl;
Herbicides (or defoliants) such as quizalofop and its
derivatives, Acetochlor, Metolachlor, Imazapur and Imazapyr,
Glyposate and Gluphosinate, Butachlor, Acifluorfen or
Acifluorfen-sodium, Oxyfluorfen, Butralin, Fluazifop-butyl,
Bifenox, Bromoxynil and Ioxynil and esters thereof,
Diflufenican, Phenmedipham, Desmedipham, Oxadiazon, Mecoprop
MCPA, MCPB, Linuron, Isoproturon, Flamprop and its derivatives,
Ethofumesate, Diallate, Carbetamide, Alachlor, Chorpyralid,
2,4-D, Tribufos, Triclopyr, Diclofop-methyl, Sethoxydim,
Pendimethalin, Trifluralin, Ametryn, Chloramben, Amitrole,
Asulam, Dicamba, Bentazone, Atrazine, Cyanazine, Thiobencarb,
CA 02107341 2002-10-29
Prometryn, 2-(2-chlorobenzyl)-4,4-dimethyl-1,2-oxazolidin-7-
one, Fluometuron, Napropamide, Paraquat, Bentazone, Molinate,
Propachlor, Imizaquin, Metribuzin, Tebuthiuron, Oryzalin,
Pursuit, Norflurazon, Simazine, Linuron, Trichlopyr, Aclonifen,
Flurtamone, Sulfonylureas eg Nicosulfuron, Chlorsulfuron,
Sulfometuron-methyl, Metsulfuron-methyl, Bensulfuron-methyl,
Chlorimuron-ethyl, Tribenuron-methyl, Thifensulfuron-methyl,
Primisulfuron-methyl, Ethametsulfuron-methyl and
Rimsulfuron,and Trialkoxydim and
Insecticides, miticides, acaricides or nematicides such
as Ebufos, Carbosulfan, Amitraz, Vamidothion, Ethion,
Triazophos, Propoxur, Phosalone, Permethrin, Cypermethrin,
Parathion, Methylparathion, Diazinon, Metomyl, Malathion,
Lindane, Fenvalerate, Ethogrophos, Endrin, Endosulfan,
Dimethoate, Dieldrin, Dicrotophos, Dichloroprop, Dichlorvos,
Azinophos and its derivatives, eg Azinophos-methyl, Aldrin,
Cyfluthrin, Deltamethrin, Disulfoton, Chlordimeform,
Chloropyrifos, Carbaryl, Dicofol, Thiodicarb, Propargite,
Demeton, Phosalone, Acephate, Carbofuran, Methamidophos,
Fenbutalin oxide, Trichlorfon, Abamectin, Aldicarb, Pyrethroids
such. as alpha-Cypermethrin and Bacillus thuringiensis.
Plant growth regulators such as gibberellic acid, ethrel
or ethephon, cycocel, Chlormequat, Mephiquat, Thiadiazuron,
Tribufos and Dimethipin.
Where the agrochemical composition is in liquid form
then suitable organic solvents which may be used as carriers in
the agrochemical composition include petroleum based solvents,
W092/17382 ~ ~~ ~~"'I~;~,j '. PCT/GB92/00603
- 12 -
e.g, petroleum ethers, mineral oils, aliphatic or aromatic
hydrocarbons, e.g. hexane, octane, cyclohexane, benzene, xylene
and naphthalene, halogenated aliphatic or aromatic
hydrocarbons, e.g. carbon tetrachloride, chloroform, methylene
chloride and chlorobenzene, esters e.g. amyl acetate, ketones,
e.g. cyclohexanone, 1-methyl-2-pyrrolidinone (NMP), ethers, or
a higher alcohol (lower alcohols may migrate through the water
soluble or water dispersible materials described above: this
can result in product appearing on the outside of the
envelope). It will be understood that mixtures of solvents,
e.g. mixtures of a hydrocarbon solvent with another solvent
such as a ketone or a higher alcohol, may also be used. The
organic liquid must be reasonably dry and typically contains
less than 2 to 3% of water to ensure that it does not leak
prematurely from the package.
Such compositions may comprise, in additian to, or
in some cases instead of, an organic solvent as a carrier or
diluent, a surfactant, which is reasonably dry in that it
contains less than 2 to 3% water. Suitable surfactants may be
of the ionic or non-ionic types: for. example
sulphoricinoleates, quaternary ammonium derivatives, products
based on condensates of ethylene oxide with alkyl and polyaryl
phenols, e.g. nonyl- or octyl-phenols, or carboxylic acid
esters of anhydrosorbitols which have been rendered soluble by
etherification of the free hydroxy groups by condensation with
ethylene oxide, alkali and alkaline earth metal salts of
sulphuric acid esters and sulphonic acids such as dinonyl- and
dioctyl-sodium sulphonosuccinates and alkali and alkaline earth
metal salts of high molecular weight sulphonic acid derivatives
CA 02107341 2002-10-29
- 13 -
such as sodium and calcium lignosulphonates and sodium and
calcium alkylbenzene sulphonates, and block ethylene
oxide/propylene oxide copolymers.
Suitably, the agrochemical composition may comprise
up to 10%, e.g. from 0.05% to 10% of surfactant but, if
desired, it may comprise higher proportions of surfactant for
example up to 15% in liquid emulsifiable suspension
concentrates and up to 25% in water soluble concentra:.es.
The contents of the package may be thickened or
rendered thixotropic to provide a gel. An increased viscosity
in the contents can reduce the likelihood of rupture if the
package is subjected to mechanical shock. The contents of the
package may be rendered more viscous or thixotropic by the
inclusion of additives, for example, a modified organophile, or
bentonite, lecithin, polymethylene oxide or silica gel.
The concentrations of agrochemical
dissolved or dispersed in the organic liquac~ or in the gel will
generally be those conventionally used: in order to reduce the
bulk of each package, however, concentrations may be increased.
Each package will preferably contain 100m1 to 1.5 litres,
preferably at least about 500 ml and will preferably contain a
convenient standard volume, for example 500 ml or 1 litre,
although it will be appreciated that any convenient standard
volume may be chosen.
When the agrochemical composition is in solid form
then it may comprise any conventional carrier or diluent which
is reasonably dry, in that it contains less than 2 to 3% of
moisture. Examples of suitable solid diluents or carriers are
aluminium silicate, talc, calcined magnesia, kieselguhr,
CA 02107341 2002-10-29
- is -
tricalcium phosphate, powdered cork, adsorbent carbon black and
clays such as kaolin and bentonite. Solid compositions may
comprise surfactants, such as dispersing agents, for example
those surfactants previously mentioned. In some cases such
surfactants may also be used as diluents or carriers.
As with compositions in liquid form, the
concentration of agrochemical in solid compositions
may be as conventionally used: concentrations may however be
increased to reduce the bulk of the package.
The agrochemical compositions used in the package of
the present invention may be prepared by conventional means.
The packages of the present invention may be inside
an additional outer container. Such a container may provide
additional strength and if water resistant may serve to protect
the package of the present invention from accidental exposure
to water. The outer container is preferably sealed to avoid
exposing the package of the present invention to undue
moisture.
It will be appreciated that the package of the
present invention may comprise more than one compartment
containing the same or different agrochemical compositions. Such
multi-compartment packages are particularly useful where a
combination of components are to be employed together and
where the components are incompatible for a prolonged period,
for instance if they react chemically.
Preferably the packages according to the invention
should release their contents in less than about 10 minutes.
Typically the packages will be placed in the spray tank of a
conventional sprayer. The tank will generally be partly filled
CA 02107341 2002-10-29
- 15 -
with water, and the package added. When the tank is provided
with means to agitate the water the contents of the bag will be
released more rapidly. It is preferred that release should
take place in less than about a minute, for example in 30 to 40
seconds. It will be understood that the time taken to release
the agrochemical will depend upon a number of factors apart from
the nature of the bag, including the temperature of the water
and the level of agitation.
The packages of the present invention may be
l0 obtained by first deforming a sheet of water soluble or
dispersible material so as to form a recess adapted to retain a
agrochemical composition. This may be achieved for example by
vacuum forming where the sheet is deformed to conform to the
shape of a suitable mould and may, if desired, be a
thermoforming process to cause the sheet to retain its shape
after release from the mould.
Where the deformation is by vacuum forming, the
mould may be equipped with pinholes through which the space
between the mould and the sheet can be evacuated.
Where deformation is by thermoforming, the sheet
may be driven against the mould by vacuum forming, or by
applying a superatmospheric pressure to the other side of the
sheet (this may be effected using an operating pressure of, for
example 4~ to 6 bar) or by mechanical displacement of the sheet
(plug formingj. Thermoforming will generally be carried out
using a temperature not less than 40°C and not more than 110°C.
A temperature from 70-110°C is preferred, most preferably about
90°C.
After deforming the first sheet of water soluble or
CA 02107341 2002-10-29
- 16 -
dispersible material, the agrochemical composition is placed in
the recess formed by the deformation, and a second
substantially planar sheet of water soluble or water
dispersible material is then placed across the recess. The two
sheets of water soluble or water dispersible material are then
heat sealed so as to form a continuous closed heat seal. The
width of the heat seal itself is preferably 1-10 mm, preferably
about 5 mm. The dwell time for heat sealing will depend upon,
for example, the material used, its thickness and the heat seal
to temperature. A dwell time of about 3 seconds is generally
suitable when the thickness of the material is about 80u. A
sealed compartment is thus formed.
In order to ensure optimum processability the
heat sealing is generally carried out at 15 to 25~C and 15 to
85% relative humidity (RH). The relative humidity is
preferably 35 to 55%. Some routine experimentation may be
required to obtain a suitable heat seal depending on the
package material, e.g. the particular grade and thickness of
PVOH chosen. The quality of the seal can be checked, for
2o example by visual inspection for areas of opacity or for
bubbles. .Imperfections in the seal may give rise to a lack of
water solubility or water dispersibility of the seal. The heat
sealing process can be carried out on conventional heat sealing
equipment which permits control variation of the sealing jaw
temperature, jaw pressure and dwell time.
The following Examples illustrate the invention. In the
Examples the values for tensile strength refer to a seal of 25
mm width with a jaw separation speed of 300 mm/min.
CA 02107341 2002-10-29
- 17
EXAMPLE 1
A first sheet of polyvinyl alcohol (Vinex 2144: thickness
225u) is heated at 90°C and then thermoformed into a mould, the
draw depth being 80 mm, with a forming time of 6 seconds. The
product to be packaged is placed in the recess thus formed. A
second sheet of polyvinyl alcohol (Solublon KA40/KA40, a
laminate of two layers each of 40~ thickness: total thickness
80~) is placed across the recess thus formed and heat sealed
using a sealing temperature of 180°C with a dwell time of 8
seconds. The operating air pressure of the thermoforming
apparatus is 4.5 bar.
The tensile strength of the seal in the Water-soluble
bags thus produced is 32.4 N (mean). The production of the
water-soluble bags is carried out at 21°C (room temperature)
and a relative humidity of 38~.
EXAMPLE 2
A first sheet of polyvinyl alcohol (Vinex 2144:
thickness 225~c) is heated at 90°C and then thermoformed into a
mould, the draw depth being 80 mm, with a forming time of 6
seconds. The product to be packaged is placed in the recess
thus formed. A second sheet of polyvinyl alcohol (Vinex 2144:
thickness 75u) is placed across the recess thus formed and heat
sealed using a sealing temperature of 200°C with a dwell time
of 6 seconds. The operating air pressure of the thermoforming
apparatus is 4.5 bar.
The tensile strength of the seal in the water-soluble
bags thus produced is 28.7 N (mean). The production of the
water-soluble bags is carried out at 21°C (room temperature)
and a relative humidity of 38%.
