AP374A

AP374A - Sealed package.

Info

Publication number: AP374A
Application number: APAP/P/1992/000437A
Authority: AP
Inventors: David Brian Edwards; William John Mccarthy
Original assignee: Rhone Poulenc Agrochimie
Priority date: 1991-10-16
Filing date: 1992-01-14
Publication date: 1994-11-27
Also published as: TW226321B; IL103426A0; ATE149131T1; EP0607316B1; NZ244732A; AU2783692A; IL103426A; EG19530A; WO1993008091A3; AP9200437A0; ZA928012B; DE69217665T2; CN1071636A; JPH07502003A; MX9205918A; CN1030831C; GB9121984D0; WO1993008091A2; BR9206762A; DE69217665D1

Abstract

A closed package comprising one or more flexible

Description

SEALED PACKAGE

This invention relates to a package particularly ζJ suitable for containing a pesticidal composition.

Pesticides, e.g. herbicides, «ore 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 the chemical pesticides, e.g. herbicides, a quantity of the pesticide is io 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 thd containers after use. Plastics containers with wide necks to facilitate pouring of their contents have bean used. Blow moulded

I 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 25 to spill the contents during the mixing process with the resulting risk of contamination of the environment and risk of contact with humans or animals. Also, it is relatively rare to empty containers so that farmers, and other users, tend to have partly full containers left around. These represent a further •-Λ

BAD ORIGINAL 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 pestialdes arc 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 or such a system in view of the need for standardisation of screw fitting sizes and the possibility of leakage if a satisfactory * tight seal ia 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. Such applications have however been limited by the capabilities of known water soluble containers which are often flexible and prone to rupture. In particular vhen a package is dropped it is particularly prone to rupture due to mechanical or hydraulic shock if it contains a liquid, gel or a fine powder.

In other fields where flexible packaging is employed, there is also a need to reduce the likelihood of rupture occurring due to mechanical shock.

The present invention seeks to overcome the disadvantages of known packages and to provide a flexible package having an improved resistance to mechanical shock.

BAD ORIGINAL

Accordingly the present invention provides a closed package comprising one or more flexible water soluble or dispersible polymeric sheets sealed to form an outer nonbreachable seal, an inner breachable seal and optionally a space between the inner and outer seals.

When the package is subjected to mechanical shock the breachable seal may be breached dissipating the energy of the shock without damaging the outer seal. Where the package comprises a space between the inner and outer seals, preferably the space contains substantially none of the contents of the package: if the inner seal is breached the extra volume accessible to the contents may help to dissipate shock.

The breachable seal used in the package is one which may be breached when the package is subjected to mechanical shock for example when dropped from a height of 1 to 2m.

The breachable seal may be breached by peeling apart the seal or by means of a gap in the seal.

The package of the invention comprises one or more sheets of flexible material, preferably thermoformable material, sealed to form a closed package. Preferably if more than one sheet is used, they are of the same material, but they may be different. Preferably the package is formed by two separate sheets of material sealed to form a closed package.

The use of water soluble or water dispersible material in the packages of the invention may allow one or more of the following advantageous features, particularly if the contents comprise a hazardous chemical, such as a pesticide:

the contents of package are released only after contact with water in which it is to be dissolved or dispersed, minimising the possibility of accidental contact of the undiluted material with the environment or with humans or animals;

the contents can be provided in unit dosage form suitable for dilution with a predetermined amount of water removing the need for the contents to be measured out in undiluted form;

the package is easy to use : the package can be simply placed in water prior to use; and the need for washing out of the residual chemical from containers to render them safe for disposal is removed: containers which have been in contact with the contents remain uncontaminated which facilitates their disposal.

Specific suitable water soluble or water dispersible materials include polyvinylalcohol, polyethylene oxide; alkyl and hyaroxyaixyicelluiose, such as ' hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropyiceliuiose; carboxymethylcellulose; polyvinyl ethers such as polymethylvinyl ether or poly (2-methoxy or ethoxy ethylene); poly(2,4-dimethyl-6-triazinylethylene; poly (3-morpho liny lethyl ene) ; poly(N-l,2,4-triazonylethylene; poly(vinylsulfonic acid); polyanhydrides; low molecular weight urea-formaldehyde resins? low molecular weight melamineformaldehyde resins; poly(2-hydroxyethyl methacrylate); polyacrylic acid and its homologs. Preferred materials are polyethylene oxide, methyl cellulose, or polyvinyl alcohol, most preferably polyvinyl alcohol. Generally polyvinylalcohol

BAD original £ will be used as a partially or fully alcoholised or hydrolysed polyvinyl acetate film.

Most preferably a thermformable, eg Vinex, polyvinylalcohol resin is used: such resins possess the advantages of being adaptable to deep draw molding without significant shrinkage problems.

The material may be unoriented, mono-axially oriented or bi-axially oriented. Water soluble materials are preferred since they provide less disposal 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 hot water.

The maximum tensile strength of the material of the sheets comprising the package is preferably at least 20, more preferably from 30 to 80, N/mm² and the elongation at break is preferably 200 to 380%, more preferably from 220 to 350%. Testing for these values is generally carried out at 23°C and 50% relative humidity.

Preferably when the package of the invention is placed in water it should release its contents in less than about 10 minutes. Typically the package will be placed in the spray tank of a conventional sprayer. The tank will generally be partly filled 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 it 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 pesticide 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 package may contain material in liquid, gel or granular form. When the contents is in liquid or gel form it is particularly important to avoid pinholes in the package through which leakage of the contents may occur.

In such cases therefore the or each sheet may be a laminate, generally of two layers of different or the same material, as pinholes are unlikely to coincide in two layers of material.

When the contents are in granular form, the sheets typically comprise a single layer of material. 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.

The or each sheet comprising the package will generally be from 20 to 500m, preferably 50 to 250μπι, thick. The thickness of the sheet or sheets of water soluble or water dispersible material 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 contents then released.

According to a particular embodiment the package is provided with an inner breachable seal or seals in the region of the package most likely to fail. The region of the package most likely to fail will vary according to a number of factors including the contents, shape and size of the package, the storage and usage conditions of the package and can be determined by routine experimentation.

According to a particular embodiment, the package may comprise an inner seal and an outer seal of higher peel strength than the inner seal. The inner seal may itself comprise regions of varying peal strength, typically being of lower peel strength in the inner region of the seal, or it may be of uniform peel strength. The inner and outer seals may be joined to form a single continuous seal of varying peel strength or they may be separated by a space.

Alternatively there may be more than one, typically up to four, inner seals of lower peel strength than the outer seal each of which is separated by a space, preferably containing substantially none of the contents of the package.

* In cases where more than one inner peelable seal is present then peel strengths may be the same or different. Where the strength of the seals does vary, then typically the innermost breachable seal will be of lowest peel strength,the outermost breachable seal of highest peel strength and any intermediate seals will be of intermediate strength, progressively increasing towards the outermost seal.

Mechanical shook to euch a package, when filled with liquid, gel or granular contents may result in partial peeling of the inner seal or seals thereby absorbing the energy of the shock without damaging the outer seal.

The inner and outer seals may be heat seals. The outer seal may be a. conventional heat seal typically, 2 to 5 ma thick. The or each inner heat seal will typically have a thickness from 1 to 10mm, e.g. 2 to 5mm.

BAD ORIGINAL

Where the inner and outer seals are produced by the aame sealing platen then typically each inner seal will be within 20 am of the outer seal. For example there may be l to inner heat seals, each 2 to 3mm thick with n spacing of 2 to mm from the outer eeal or from each other.

Alternatively where the or each inner heat seal is produced by a separate sealing platen fron the outer heat seal, then the inner and outer seals may be widely separated with the proviso that the space between them does not contain any of the contents of the package. For example the inner seal or seals may seal the portion of the package containing the contents and the outer seal be formed around a handle portion of the package.

Rather than using heat seals, either the or each inner peelable seal or the outer non-peelable seal may be sealed using an adhesive. Conventional polymeric adhesive may be used; the strength of the adhesive used may be adjusted to provide a peelable or a ποη-peelable seal as desired. In the case where the package is water soluble or water dispersible, suitable adhesives include small amounts of water or low molecular weight solutions of polyvinyl alcohol, optionally mixed with polyvinyl acetate.

Where the package of the invention comprises a peelable seal or seals and a ncn-peelable seal, the nonpeelable and peelable seal or seals may constitute a double cr multiple seal around the whole the package. In other cases however, the inner seals or seals may be used to reinforce the outer seal only in those regions of the package which are particularly vulnerable to damage by mechanical shock. In such

BAD

ORIGINAL ft cases the inner and outer seals may be joined to prevent the contents of the package entering the space between them, if present.

Alternatively the package may comprise more than one compartment, preferably of equal volume, divided by one o_rmore inner peelable eeals each compartment containing a portion of the contents of the package. When the package 1b subject to mechanical shock, one or more of the inner paelable seals may be peeled apart which increases the volume of the package and allows energy of the shock to be dissipated without damaging the outer seal.

According to an alternative embodiment the package of the invention may comprise an outer non-breachable seal and an inner breachable seal provided by folding over a 'portion of

- the package vhich contains substantially none of the contents of the package and sealing the folded portion of the package with a weak adhesive on tha outer surface of the package. Mechanical shock to the package may be dissipated by the weak adhesive giving and allowing the package to unfold; the contents of the package may then enter the space previously between the fold and the outer seal, and prevent damage to the outer seal. The outer seal and the adhesive used may be of the same type ae described above.

According to a further embodiment of the invention the package may comprise an outer non-breachable seal and a gusset which is tacked in place by a breachable seal.

Mechanical shock to the package may break the breachable seal thereby allowing the gusset to unfold and afford more space into which the contents may move, dissipating the shock and

BAD ORIGINAL $ preventing damage to the outer seal. The breachable seal may, for example be provided by a weak adhesive on that portion of the outer surface of the package which is folded inwards to form the gusset. The outer seal and the adhesive used may be of the same type as described above.

According to a third embodiment the package of the invention may comprise an outer non-breachable seal and one or more inner seals having a narrow gap in or between them providing access to a space between the inner seal or seals and the outer seal which space contains substantially none of the contents of the package. Mechanical shock to the package may be dissipated by the entry of the contents of the package into the space between the inner and outer seals. For example the package may comprise a single inner seal with a narrow gap in it, or a pair of overlapping seals with narrow gaps between them, which gaps are in a portion of the interior of the package which does not contain any of the contents of the package when in its normal upright orientation. The same type of seals may be used as are described above: a combination of non-peelable and peelable seals may be used but normally the seals will be non-peelable.

The contents of the package may be in liquid, gel or granular form, preferably liquid or gel form. Where the contents are in liquid form they may be in the form of a solution or of a dispersion e.g. an emulsion or a suspension. Similarly in gel form, the contents may be a single phase gel or a dispersion.

The contents will be substantially dry.

They may comprise any conventional carrier, diluent or surfactant.

When the contents are 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.

Tha packages of the present invention generally contain from 0.1 grams to 7kg, preferably lg to 5kg, where the composition is in granular form. Where the contents are in liquid or gel form, the package typically contains from 5ml to 10 litres, preferably from 50ml to 5 litres.

Generally the package will contain at least a small amount cf unfilled 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. The unfilled space further provides an area into which the contents of the packaga may move on exposure to mechanical shock which tends to dissipate the energy from the shock.

The package of the invention may, in a particular embodiment contain a pesticidal composition. Such a composition may be of conventional type.

Suitable pesticides 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 aa salts or eaters, e.g. heptanoates or octanoates) . Kolluscicidea, suitable for addition to, for exaaple, ponds or streams may also be employed.

BAD ORIGINAL

More generally, the package of the invention way contain chemicals which are potentially toxic or damaging or detrimental to health or to the environment. As well as pesticides this includes chemicals which are to be dissolved or dispersed in a large volume of water or aqueous liquid, such as compounds, e.g. metronidazole, used to combat spoilage in industrial aqueous liquids, or compounds for addition to the aqueous circuita of e.g. domestic or industrial heating systems, compounds for addition to swimming pools, photographic materials, inks, dyestuffs, non-aqueous organic acids and cement additives.

When the material comprising the sheet or sheets of package is a polyvinylalcohol the contents should generally not comprise borates, chlorides or chlorates in amounts-effective to lead .to deterioration of the material unless the material is protected from them.

Where tha contents are in liquid form then suitable organic solvents which may be used as carriers include petroleum based solvents, 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, 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 package) . It will be understood that mixtures of solvents, e.g. mixtures of a hydrocarbon eolvont with another solvent such as a ketone or

BAD ORIGINAL a higher alcohol# may alao toe used. The organic liquid must be reasonably dry and typioally contains less than 2 to 3% of water if the package is water soluble or water dispersible to ensure that it does not leak prematurely from the package.

Such compositions may comprise a surfactant# in addition to, or in some cases instead of# an organic solvent as a carrier or diluent. Preferably# such 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

IB - by condensation with ethylene oxide, alkali and alkaline earth metal salts of sulphuric acid esters and suiphonlc acids such as dinonyl- and dioetyl-sodium aulphonosuccinates and alkali and alkaline earth metal salts of high molecular weight sulphonic acid derivatives such as sodium and calcium lignosulphonates and sodium and calcium alkylbenzene sulphonates.

Suitably# the contents may comprise up to 10%, e.g. from 0.05% to 10% of surfactant but# if desired# may comprise higher proportions of surfactant for example up to 15% in liquid emulsifiable suspension concentrates and up to 2 5% in water soluble concentrates.

The contents of the package may be thickened or rendered thixotropic to provide a gel. An increased viscosity in ths contents can reduce the likelihood of the of rupture if

BAD ORIGINAL the package le subjected to mechanical shook. The contents cf the package may be rendered more viscous or thixotropic by the inclusion of additives, for example, a modified organophile, or bentonite, lecithin, polymothylene oxide or silioa gel.

The concentrations of the chemical, such as pesticide, dissolved or dispersed in the organic liquid 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 vill preferably contain at least about 500 aland vill 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 contents are in granular form then this may comprise any conventional carrier or diluent which if the

- package.is water soluble or dispersible is reasonably dry, in that it contains less than 2 to 3V of moisture. Examples of suitable solid diluents or carriers are aluminium silicate, talc, calcined magnesia, kieselguhr, 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 ba used as diluents or carriers,

As with compositions in liquid form, the concentration of chemical such as pesticide in the solid pesticidal compositions may be as conventionally used: concentrations may however be increased to reduce the bulk of the package.

bad original

The contents, such as peetioidal compositions, present in the package cf the present invention may be prepared by conventional means.

The packages of the present invention may be 5 obtained by first forming a receptacle adapted to retain the contents, filling the open receptacle with contents and then sealing it.

The open receptacle may be obtained by conventional means. For example, this may be achieved by a vacuum forming where material forming the receptacle is deformed to conform to the shape of a suitable mould and may, if desired, be a thermoforming procese to cause the sheet to retain its shape after release from the mould.

Where the deformation is by vacuum farming, the

- mould may be equipped with pinholes through which the space between the mould end the sheet can be evacuated.

Where deformation ie 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, or by mechanical displacement of the sheet (plug forming).

After forming the open receptacle, the contents of the package are placed inside and the receptacle closed to form a sealed compartment. The sealing step may involve the sealing of two surfaces of the package together, the folding of a or the sheet of the material forming the receptacle onto itself and then sealing to itself or the sealing of an additional sheet of material to the open receptacle. It will be appreciated that the open receptacle may be partially sealed

BAD ORIGINAL $ prior to filling it.

The inner breachable seal and outer non-breachable seals of the package may be produced simultaneously or using separate sealing steps. Either seal may be produced at least partially prior to filling the package. As previously mentioned either seal may be produced by heat sealing or by an adhesive.

Where the package is sealed by heat sealing, the heat sealing may be carried out using conventional heat sealing equipment and conventional conditions. The parameters of sealing jaw temperature, jaw pressure and dwell time may be controlled to obtain an optimum heat seal. In order to ensure optimum processability, heat sealing is generally carried out at 15 to 85% relative humidity (measured at 18 to 22’C). The relative humidity is preferably 35 to 55%.

Some routine experimentation may be required to obtain a suitable heat seal depending on the material forming the package, e.g. the particular grade and thickness of PVOH chosen. The quality of the seal can be checked, for 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 where this is desired.

According to a specific embodiment, an inner peelable seal and an outer non-peelable seal may be produced simultaneously using the same heat sealing platen. In such a case the strength of the heat seal produced may be varied for example by varying the sealing jaw temperature over the heat seal platen, λ slightly lower jaw temperature may be used on' the inner portion of the sealing surface which produces a peelable seal: a variation in sealing jaw temperature may be obtained using a stepped sealing jaw having a first sealing surface closer to a heating element and at a higher temperature than a second sealing surface. Rather than a stepped sealing jaw a contoured jaw may alternatively be used and there may be a space between the inner and outer sealing surface corresponding to a space between the seals. Similarly, a sealing jaw comprising more than two sealing surfaces may be used to produce a package comprising more than one inner breachable seal.

As an alternative to varying peel strength by varying sealing jaw temperature as described above,.such variation may be obtained by varying sealing jaw pressure or dwell time.

λ stepped sealing jaw may also be used in conjunction with a planar member of resilient material. A seal of variable strength may then be obtained by the variation in jaw pressure which is produced by the stepped jaw.

* Packages according to the invention are shown, by way of illustration, in the accompanying drawings in which: Figure I illustrates a package formed by thermoforming or vacuum forming a sheet (1) of water-soluble material into a mould (2), a pesticidal composition (3) being contained in tho recess thus formed. A second sheet (4) of water-soluble material is heat sealed to the first sheet on the flange (5) of the mould (2). The heat seal comprises an outer non-breachabls seal (6) and an inner breachable seal (7).

BAD ORIGINAL fl

Figurd ΪΙΙ shows two heat sealing Jaw arrangement· which nay be used to provide a variation in peel strength across the seal by varying the jaw pressure applied during the sealing process* Figures III(a) shows a resilient planar sealing jaw (14) which is heated and a non-heatad stepped sealing jaw (15) having a sealing surface a portion of which (16) is closer to the jaw (14) and a portion (17) further from jaw (14). In operation variation in jaw pressure is produced by the difference in the distance x _w « between 14 and 16 and the distance x + y between 14 and 17, bearing in wind the jaw (14) vill resile on closing, it vill be appreciated that more than one step may be present in the non-heated jaw leading to provide more than one variation in the peel strength of the seal. Figure HI(b) shows an alternative arrangement in which the sealing surface of the non-heated jaw has a portion (18) parallel to the heated jaw and a further portion (19) which slopes away from the heated jaw providing a oentinuous variation in the jaw pressure. Jaw (14) may be resilient.

Figure IV shows that two heat sealing Jaw * as arrangements which may be used to provide a variation in peel strength by varying tha jaw temperature across the seal during the sealing process. Five iv(a) show· a stepped

.......τ_bw>0M0'^nM19 * Al .

heated sealing jaw (20) and a corresponding stepped nonheated sealing jaw (31). The distance between the . corresponding sealing ourfcaa of the jaws ie a constant x.

Variation in the temperature at the steps of the sealing jaw, which is due to variation in the distance of the sealing surface from a heating element, produces a variation in peel strength. Either.of the jaws 30 and 31 may be resilient. Figure XV(b) shows an alternative arrangement in which two planar sealing jaws are employed, a non-heated jaw (32) and a heated Jaw (23) in vhich a variation in temperature is produced by the presence in the jaw of insulating material (24). Due to the insulating material the portions 25 and 26 of the heated jaw are at lover temperatures than the portion 22 when in operation. Hither of the jaws (20) and (si) may be resilient.

Figure V shows a heat sealing arrangement vhich may be used to provide a variation in peel strength by varying the dwell time. Λ heated jaw (28) is employed together with two separately removable non-heated jaws (29) and (30). in operation the heated and non-heated jaws are separated by a constant distance x and variation in dwell time is achieved by withdrawing one of the jaws 29 and 30 while continuing to seal against ths other. In this case a jaw, preferably jaw 28_y may be resilient t

5 Figure VI show» a heat sealing jaw arrangement in which variation in peel strength le produced by a combination of variation in jaw pressure and temperature.

BAD ORIGINAL

- ,20 *Th· arrangement shown le similar to that shown In Figure ' IIIB, eave that the non-heated jaw (31) is planar and the . heated jaw (32) has a portion (33) of Its sealing surface parallel to 31 and a portion (34) which slopes away from 31.

Variation in the jaw pressure is provided by variation in the distance between the jaws and variation in the temperature of the heated.jaw (32) is provided by the variation in the distance of the sealing surfaoe of 32 from a heating element. Either of the jaws may be resilient.

io Figure vix shows a heat sealing jaw arrangement in which variation in peel strength is produced hy a combination of variation in jaw pressure and dwell time, λ planar sealing jaw (34) is employed vith a non-heated jaw (39) having a stepped sealing surface. The portion of the stepped surface of 35 which is closer to 34 is mounted on a spring (37) and is movable relative to the remainder of 35. In operation a variation in jaw pressure is produced by the variation in the separation of the jaws. When the non, h heated jaw (35) is withdrawn the spring 37 extends increasing the dwell time of the sealing surface 36 in contact vith the preferably resilient jaw (34).

if in Figure VII jaw 35 is resilient but jaw 34 and member 36 are hot, or are more rigid/ the contact pressure at the interface 34/36 will he higher than that at the % interface 34/35 when the jaws are fully closed together.

Claims

1. A closed package comprising one or more flexible water soluble or dispersible polymeric sheets sealed to form an outer non-breachable seal, an inner breachable seal and optionally a space between the inner and outer seals.

2. A package according to claim 1 which comprises a space between the inner and outer seals containing substantially none of the contents of the package.

3. A package according to claim 1 or 2 which comprises more than one inner breachable seal.

4. A package according to claim 1, 2 or 3 in which the inner seal is of lower peel strength than the outer seal.

5. A package according to claim 4 comprising more than one inner seal of lower peel strength than the outer seal, and a space between the inner and outer seals and between each inner seal.

6. A package according to claim 4, divided into more than one compartment, each containing a portion of the contents of the package, by the or each inner seal.

7. A package according to claim 1, 2 or 3 which comprises an outer non-breachable seal and an inner breachable seal provided by a folded portion of the package containing substantially none of the contents of the package, which folded portion is adhered to an outer surface of the package by a weak adhesive.

8. A package according to claim 1, 2 or 3 which comprises an outer non-breachable seal and a gusset which is tacked in place by a breachable seal.

9. A package according to any one of the preceding claims which comprises one or more inner seals having a narrow gap in or between them providing access to the space between the inner and outer seals.

10. A package according to any one of the preceding claims which comprises a breachable seal in the region of the package most likely to fail.

11. A package according to any one of the preceding claims in which the water soluble or dispersible material comprises polyethylene oxide, methyl cellulose or a polyvinyl alcohol.

12. A package according to claim 11 in which the water soluble or water dispersible material comprises a cold water soluble polyvinyl alcohol which is 40 to 99% hydrolysed or alcoholised polyvinyl acetate.

13. A package according to any one of the preceding claims in which the contents are released in less than 10 minutes after contact with water.

14. A package according to claim 13 in which the contents are released in less than 1 minute.

15. A package according to any one of the preceding claims which contains a composition in liquid or gel form.

16. A package according to any one of the preceding claims which contains from 5ml to 10 litres in liquid or gel form.

17. A package according to any one of the preceding claims which contains a pesticidal composition.

18. A package according to claim 17 in which the composition comprises a hydroxybenzonitrile herbicide.

19. A package according to claim 18, in which the hydroxybenzonitrile herbicide comprises a mixture of ioxynil and bromoxynil esters.

20. A package according to any one of the preceding claims in which the or each sheet has a thickness from 20 to 500μιη.

- 23 preceding claims which contains a pesticidal composition.

19. λ package according to claim 18 in which the composition comprises a hydroxybenzonitrile herbicide.

20. A package according to claim 19, in which the 9 hydroxybenzonitrile herbicide comprises a mixture of ioxynil and bromoxynil esters.

21. A package according to any one of the preceding claims in which the or each sheet has a thickness from 20 to 500/na.