WATER-SOLUBLE BAG ENCLOSING AGRICULTURAL CHEMICAL

SAC HYDROSOLUBLE RENFERMANT DES PRODUITS CHIMIQUES AGRICOLES

English Abstract

A containerization system and containers which are particularly suitablc for storing, packaging and transporting toxic or hazardous
products such as agricultural chemicals is provided. The containerization system comprises the agricultural chemical in the form of a gel,
solid or liquid which is contained within a water-soluble bag. The bag is made of co-extruded film of at least two separate polyvinyl alcohol
layers combined directly after extrusion in the fluid melt state. The film is characterized in that it shows no interface boundaries.

French Abstract

Système de conteneurisation et conteneurs convenant particulièrement au stockage, à l'emballage et à l'expédition de produits dangereux ou toxiques tels que des produits chimiques à usage agricole. Le système de conteneurisation comprend ledit produit chimique sous forme de gel, de solide ou de liquide contenu dans un sac soluble dans l'eau. Le sac est composé d'un film coextrudé comportant au moins deux couches séparées d'alcool polyvinylique combinées immédiatement après l'extrusion à l'état fondu et coulant. Le film se caractérise en ce qu'il ne présente aucune démarcation d'interface.

Claims

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WHAT IS CLAIMED IS:
1. A containerization system for holding and securing agricultural chemical compounds
which comprises a water soluble bag made of co-extruded film which completely encloses
an agricultural chemical compound, said co-extruded film containing at least two separate
polyvinyl alcohol layers combined directly after extrusion in the fluid melt state, and said
film also characterized in exhibiting no interface boundaries.
2. The containerization system of claim 1, wherein the agricultural chemical compound is
a pesticide or a plant protection agent.
3. The containerization system of claim 1, wherein the co-extruded polyvinylalcohol film
has a thickness between about 20 and 240 microns.
4. The containerization system of claim 3, wherein the film has a thickness between about
40 and 160 microns.
5. The containerization system of claim 4, wherein the film has a thickness of about 120
microns.
6. The containerization system of claim 1, wherein the bag has a capacity of between
about 0.1 and 4.0 liters.
7. The containerization system of claim 1, wherein the co-extruded film is a tri-extruded
film.
8. The containerization system of claim 1, wherein the agricultural chemical compound is
in the form of a gel.

Description

21 63548
i'O 94/29188 PCTIIB94/00136
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WATER-SOLUBLE BAG ENCLOSING AGRICULTURAL CHEMICAL
The present invention relates to a containerization system and containers which are parti-
cularly suitable for storing, packaging and transporting toxic or hazardous products such
as agricultural chemicals. In particular, the present invention relates to water-soluble bags
enclosing the agricultural chemical in the form of a gel, solid or liquid which is contained
within a water-soluble bag made of co-extruded film of at least two separate polyvinyl al-
cohol layers combined directly after extrusion in the fluid melt state. The film is characte-
rized in that it shows no interface boundaries.
Water-soluble bags containing agricultural chemicals in gel or liquid form have just re-
cently been developed and put into practical use. These water-soluble bags may be thrown
into a water tank of a spray system whereupon the bags dissolve and the chemicals con-
tained therein are dispersed into the water supply. Thus, there is no need to dispose of the
packaging of the chemicals. U.S. Patent No. 5,080,226 to Hodakowski et al. discloses a
water-soluble bag, preferably made of polyvinylalcohol (PVA) film, containing agricultu-
ral chemicals in gel form.
Until recently, polyvinylalcohol film was made by a casting process, and then several lay-
ers were l~min~ cl together to increase strength and reduce pinholes. However, these bags
are less than completely satisfactory because the dissolution time of the laminated
polyvinylal~ohol film is very high. Since the bag does not rapidly dissolve in the water
tank, the fa~ner user must either subject the tank water to vigorous stirring over an exten-
ded period of time, or risk tank apparatus clogging by premature application before the
bag is thoroughly dissolved.
Additionally, the laminated bags are less than completely satisfactory in that they are
J susceptible to breakage upon application of pressure.
Recently, however, polyvinylalcohol films have been made by an extrusion process. For
example, EP-A-0 347 222 discloses a container system comprising a semi-rigid outer con-
tainer accommodating a water-sol~lble bag. The waler-soluble bag is disclosed as compri-
sing PVA, polythylene oxide or methylcelllllose. This publication stated that the PVA may
be extruded.
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Although single extruded PVA film dissolves quickly, it is also less than completely satis-
factory, because the film lacks strength.
Accordingly, an object of the present invention is to provide a water-soluble bag contain-
ing agricultural gel, solid or liquid which dissolves rapidly.
Yet another object of the present invention is to provide a water-soluble bag which has
suf~lcient strength to resist breakage and pinhole leaks.
To achieve this object, the water-soluble bag is made of a co-extruded film of at least two
separate polyvinyl alcohol layers combined directly after extrusion in the fluid melt state.
The film is characterized in that it shows no interface boundaries.
The invention relates to a containerization system for holding and securing agricultural
chemical compounds which comprises a water soluble bag made of co-extruded film
which completely encloses an agricultural chemical compound, said co-extruded film con-
taining at least two separate polyvinyl alcohol layers combined directly after extrusion in
the fluid melt state, and said film also characterized in exhibiting no interface boundaries.
Until recently, all polyvinylalcohol (PVA) films are made by a casting process where the
dissolved PVA is poured onto a conveyor-type belt or sheet and then the film is removed
or rolled after drying. To add strength and reduce pinholes, several layers of these films
are then laminated together with an adhesive applied by spraying or other techniques.
Recently there is developed an extrudible resin process for making PVA film. Contrary to
the casting process, the extrudible resin process is an extrusion blown process. This pro-
cess has severàl advantages, one of which is that several layers may be simultaneously for-
med and bonded together without the use of an adhesive.
Applicants have ascertained that, for use in water-soluble bags containing agricultural
gels, solids or liquids, these multiple-layer extmded films are advantageous over either la-
min~t~d cast ~llms which dissolve slowly or single layer extruded films which are suscep-
tible to breakage and pinhole leaks. In particular, applicants have ascertained that the tri-
extruded film (three-layered film) is particularly advantageous for use in water-soluble
bags containing agricultural gel or liquid.
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The co-extruded film has preferably a thickness between 20 and 240 microns, particularly
preferably between about 40 and 160 microns and most preferably about 120 microns.
The thickness is important for balancing bag stability with rapid dissolution.
)
Whereas the layers of laminated film are clearly discernible under a microscope at a mag-
nification factor of 200-fold, the co-extruded film appears as one layer. Nevertheless, the
co-extruded film when used in a water soluble bag is stronger than a single-layer extruded
film of the same thickness.
The bag should have a capacity from about 0.1 to 4.0 Iiters of gel, solid or liquid.
The agricultural chemical compound is preferably a pesticide or a plant protection agent.
The compounds may be formulated as for example water-dispersable powders or granules,
as emulsifiable liquids or preferably as gels.
The bag may be formed as a twin-bag connecting two bags with a heat sealing boundary,
or as a two-chambre bag (bag-on-bag) constructed with PVA film placed between two
other films and bound together by heat-sealing, or as a bag in bag system where a little
chemical filled PVA bag is placed in a chemical filled greater outer bag.
The following examples are presented for illustrative purposes only, and are not intended
in any way to limit the scope of the invention.
Example 1:
Two water soluble bags, each containing 610 grams of gel product, are shock tested in a
Lansmont~ vertical free fall shock machine. The first bag is made of a 3.0 ml mono-ex-
truded PVA film, whereas the second bag is made of a 3.0 ml tri-extruded PVA film. The
first mono-extruded bag exhibits a velocity change of 12~ inches per second, whereas the
second tri-extruded bag exhibit~ a velocity change of 210 inches per second.
Example 2:
Two water soluble bags, each containing 610 grams of gel product, are drop tested in a
Lansmont(~ vertical free fall shock machine. The first bag is made of a 3.0 ml mono-ex-
truded PVA film, whereas the second bag is made of a 3.0 ml tri-extruded PVA film. The
first mono-extruded bag exhibits a critical drop height of 48 inches, whereas the second
tri-extruded bag exhibits a critical drop height of over 48 inches (beyond the meàsuring
capacity of the machine).
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Example 3:
In multiple trials, three water soluble bags, each containing 204 grams of gel product, are
compressed in an Instron(~) Test System Model 4200 machine. The first bag is made of 3.0
ml laminated PVA film, the second bag is made vf a 3.0 ml mono^extruded PVA film, and
the third bag is made of a 3.0 ml tri-extruded PVA film. After averaging the trials, the first
l~min~t.od film bags exhibit breakage at an average of 300 lbs, the mono-extruded bags ex-
hibit breakage at an average of 325 lbs, and the tri-extruded bags exhibit breakage at an
average of 528 lbs.
Although the present invention has been described above in connection with a preferred
embodiment thereof, various changes and modifications will become apparent to those of
ordinary skill in the art. Therefore, such changes and modifications are intended to be
within the true spirit and scope of the present invention as defined by the appended claims.
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