NZ244732A - Package for pesticide: flexible water soluble or water dispersible polymeric sheets sealed together to form an inner breachable seal and an outer non-breachable seal - Google Patents

Description

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OTiniofn ^rcci ...J.4-]j.Q.lfi.^\ < : : i5).JSb.S I Dp'.G* , n n- =-vn';*!:il, No: 2 6 JUL 1995 i^V ii.C2 NEW ZEALAND PATENTS ACT, 1953 No.: Date: COMPLETE SPECIFICATION SEALED PACKAGE We, RHONE-POULENC AGRICULTURE LTD, a British body corporate, of Fyfield Road, Ongar, Essex CM5 OHW, United Kingdom hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- (followed by page -la-) - la- I This invention relates to a package particularly suitable for containing a pesticidal composition.

Pesticides, e.g. herbicides, are often potentially 5 harmful materials and aro connonly produced aa a ccncontratod solution or dispersion in an organic liquid, as a gel or in solid form. Such ch«aicalo are typically supplied in a metal or blow-inculded plastics container. To use the chemical pesticides, e.g. herbicides, a quantity of the pesticide is 10 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 bo great care must be taken in measuring and mixing them to avoid spillage and to 15 - avoid human or aninal 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 tc reduce residues remaining ir. thd containers after use. Plastics containers with wide necks to facilitate 2 0 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 25 to spill the contents during the nixing 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 loft around. These represent a further J.; a ^ ^ - 2 - n i, ', / ^ / » U / W in hazard. Even when all of the contents have been used it is diffioult to dispose of the empty container. Xt is also difficult to wash adequately the containers and measuring instruments in which the concentrated pesticides arc handled.

These devices represent a further ha2ard 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 10 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 4 fitting sizes and the possibility of leakage ir a satisfactory 15 " 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 20 containers which are often flexible and prone to rupture. In particular when a package ia 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 25 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. m 244732 Accordingly the present invention provides a closed package comprising one or more flexible water soluble or water dispersible polymeric sheets sealed to form an outer non-breachable seal, an inner breachable seal and 5 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 10 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 15 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 20 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 25 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 30 pesticide: tha contents of package are released only after contact with water in which it ia to be dissolved or dispersed, minimising the possibility of accidental contact of the undiluted material with the environment or with humans or 5 animals; the contents can be provided in unit dosage form suitable for dilution with a predetermined amount of water removing the need for the oontonts to b« 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 th.e residual chemical from containers to render them safe for disposal is removed: containers which have been in contact with the contents remain 15 - uncontaminated which facilitates their disposal.

Specific suitable water soluble or water dispersible materials include polyvinylalcohol/ polyethylene oxide; alXyl and hyaroxyalkylcellulose, such as hydroxymethylcellulose, hydroxyethylcellulose, 20 hydroxypropyiceliuiose; carboxymethylcellulose; polyvinyl ethers such as polymethylvinyl ether or poly(2-methoxy or ethoxy ethylene); poly(2,4-dimethyl-6-triazinylethylene; poly(3-morpholinylethylene) ; poly (N-1,2, 4-triazonylethylene; poly(vinylsulfonic acid); polyanhydrides; low molecular weight 25 urea-foraaldehyde resins; low molecular weight melaaine-formaldehyde resins; poly(2-hydroxyethyl methacrylate); polyacrylic acid and itB homologs. Preferred materials are polyethylene oxide, methyl cellulose, or polyvinyl alcohol, oost preferably polyvinyl alcohol. Generally polyvinylalcohol 244732 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 the package of the invention releases its contents in less than about 10 minutes after contact with water. 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 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 500^1", preferably 50 to 250^m, thick. The thickness of the sheet or sheets 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 embodiaent. the packago may comprise an inner seal and an outer Beal of higher peel 5 strength than the inner seal. The inner seal may itself comprise regions of varying peel strength, typically being of lower peel strength in the inner region of the seal, or it may be of uniform peal strength. The inner and outer seals may be joined to form a single continuous seal of varying peel 10 strength or thoy say be separated by a space.

Alternatively there may be core 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. 15 - In cases where nore than one inner peelable seal is present then peel strengths may be the same or different. Where the strength of the seala does vary, then typically the innermost breachable seal will be of lowest peal strength,"the outermost breachable seal of highest peel strength and any intermediate 20 seals will be of intermediate strength, progressively increasing towards the outermost seal.

Mechanical shock to such a package, when rilled with liquid, gel or granular contents may result in partial peeling of the inner seal or seals thereby absorbing the energy 25 of the shock without daaaging 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 mm thick. The or each inner heat seal will typically have a thickness from 1 to 10am, e.g. 2 to 5mm.

| Where the inner and outer seals are produced by the same sealing platen then "typically each inner seal will be within 20 nun of the outer seal. Por example there may be l to 3 inner heat seals, each 2 to 3mm thick with a opacing of 2 to 5 3 loin from the outer Beal or from each other.

Alternatively where the or each inner heat seal is produced by a separate sealing platen from 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 lo 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 rormed around a handle portion of the package.

Rather than using heat seals, either the or each IS ■ inner praelabla seal or the outer non-paalabla seal may bo sealed using an adhasive. Conventional polymeric adhesive may be used; the strength of the adhesive used may be adjusted to provide a peelable or a non-peelable seal as desired. In the case where tha package is water soluble or water dispersible, 20 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 non-peelable seal, the non-25 peelable and peelable seal or seals may constitute a double cr multiple Beal 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 caaaa the inner and outor 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 5 one compartment, preferably of equal volume, divided by one or more inner peelable seals each compartment containing a portion of tho contents of the package. When the package is subject to mechanical shock, one or more of the inner peelable seals maybe peeled apart which increases the volume of the package and 10 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 15 - the package which contains substantially none of the contents of the package and sealing the folded portion of the package with a weak adhasive on tha outer surface of tho package. Mechanical shock to the package may be dissipated by the weak adhesive giving and allowing the package to unfold; the 20 contents of tho package may then enter the space previously between the fold and tha outer seal, and prevent damage to the outer seal. The outer seal and the adhesive used may be of the sane type as described above.

According to a further embodiment of the invention 25 the package may comprise an outer non-breachable seal and a gusset which is tacked in placo by a breachable seal.

Mechanical shock to the package may break the breachable seal thereby allowing tta gusset to unfold and afford more space into which the contents may move, dissipating the shock and preventing damage to the outer saal. Tha breachable ccal may, for example be provided by a weak adhesive an that portion of the outer surface of the package which ia folded inwards to form the gusset. The outer seal and the adhesive used may be 5 of the sane type ag described above.

According to a third embodiment the package of the invention may comprise an outer non-breachable seal and one or mors inner seals having a narrow gap in or between them providing access to a space between the inner seal or seals and 10 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 nay comprise a single inner seal with a narrow gap in 15 - 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 20 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 gal form. Whore tha contents are in liquid form they may be in the form of a 25 solution or of a dispersion e.g. an emulsion or a suspension. Similarly in gel form, the contents aay be a single phase gol or a dispersion Where tlie package comprises water soluble or water dispersible material, the contents will b« 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 5 dispersible material will be one which is insoluble in the organic solvent.

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

Generally the package will contain at least a small amount of unfilled apace, eg at least about 5% by volume, so as to minimise the likelihood of spillage of the composition 15 - 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 say, in a particular 20 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 25 hcrbioidoe, e.g. bromoxynil or ioxynil or derivatives thereof such as salts or esters, e.g. heptanoates or octanoates). Molluscicidee, suitable for addition to, for ex&aple, ponds or streams may also be employed.

/ More generally/ the package of the invention may 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 5 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 circuits of e.g. domestic or industrial heating systems, compounds for addition to swimming pools, photographic 10 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 15 to lead .to deterioration of the material unless the material is protected from them.

Where the 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, 20 aliphatic or aromatic hydrocarbons, e.g. hexane, octane, cyclohexane, benzene, xylene and naphthalene, balogenated aliphatic or aromatic hydrocarbons, e.g. carbon tetrachloride, chloroform, methylene chloride and chlorobenzene, esters e.g. anyl acetate, ketones, e.g. cyclohexanone, ethers, or a higher 25 alcohol (lower alcohols may migrate through the water soluble or water dispersible matorials 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 colvant with another solvent such as a ketone or I a higher alcohol/ may also be used. The organic liquid must be reasonably dry and typioally contains loss than 2 to 3% of water if the package iB 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: 10 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 15 - by condensation with ethylene oxide, alkali and alkaline earth metal salts of sulphuric acid esters and sulphonic acids such as dinonyl- and dioctyl-sodiura aulphonosuccinates and alkali and alkaline earth metal salts of high molecular weight sulphonic acid derivatives such as sodiuaa and calcium 20 lignosulphonates and sodium and calcium alkylbenzene sulphonates.

Suitably, the contents may conprise up to 10*, e.g. froa 0.05% to 10% of surfactant but, if desired, aay conprisa higher proportions of surfactant for exanple up to 15% in 25 liquid eaulsifiable suspension concentrates and up to 2S% in water soluble concentrates.

The contents of the package svay be thickened or rendered thixotropic to provide a gel. An increased viscosity in the contents can reduce the likelihood of the of rupture if s tho package ia subjected to mechanical chock. The contents of tho package may be rendered more viscous or thixotropic by the inclusion of additiveB, for example, a modified organophile, or bentonite, lecithin/ polymethylene oxide or silica gel.

The concentrations of the cheaical, 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 will preferably contain at least 10 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 contents are in granular form then this may comprise any conventional carrier or diluent which if the 15 - package.is water soluble or dispersible 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/ tricalcium phosphate, powdered cork, adsorbent carbon black and clays such as kaolin 20 and bentonite. Solid compositions may comprise surfactants, such"as dispersing agents, for example those surfactants previously mentioned. In some cases such surfactants may also bo uasd as diluents or carriers.

As with compositions in liquid form, the 25 concentration of chemical such as pesticide in the solid pesticidal compositions may bo as conventionally used: concentrations may however be increased to reduce the bulk of the package.

- ID - ^ Tha contents, suah aa pcoticidal compositions, present in the package of the present invention may be prepared by conventional means.

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

The open receptacle may be obtained by conventional means. For example, this may be achieved by a vacuum forming 10 where material forming the receptacle ia 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 frora the mould.

Where the deformation is by vacuum forming, the 15 • 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 auperatmospheric pressure to the other side of the 2 0 sheet, or by mechanical displacement of tho 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 25 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 b-e partially sealed 244732 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, 5 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 10 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 15 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 20 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 25 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 / " 244732 seal platen. A 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 5 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. 10 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 15 may be obtained by varying sealing jaw pressure or dwell time.

A 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 2 0 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 l illustrates a package formed by thermoforming or vacuum forming a sheet (1) of water-soluble material into a 25 mould (2), a pesticidal composition (3) being contained in the 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-breachable seal (6) and an inner breachable seal 30 (7). 244 Figure 2 illustrates a package having an integral handle (8). The contents of the package (9) are contained by a heat seal comprising an outer non-breachable seal (10) , an inner breachable seal (11) and an additional 5 breachable seal (12) at the base of the container. The package is also sealed (13) around the handle portion.

Figure 3 shows two heat sealing jaw arrangements which may be used to provide a variation in peel strength across the seal by varying the jaw pressure applied during 10 the sealing process. Figure 3(a) shows a resilient planar sealing jaw (14) which is heated and a non-heated 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 15 pressure is produced by the difference in the distance x between 14 and 16 and the distance x + y between 14 and 17, bearing in mind the jaw (14) will resile on closing. It will be appreciated that more than one step may be present in the non-heated jaw leading to provide more than one 20 variation in the peel strength of the seal. Figure 3(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 continuous variation 25 in the jaw pressure. Jaw (14) may be resilient.

Figure 4 shows that two heat sealing jaw arrangements which may be used to provide a variation in peel strength by varying the jaw temperature across the seal during the sealing process. Figure 4(a) shows a stepped heated sealing jaw (20) and a corresponding stepped non-heated sealing jaw (21). The distance between the corresponding sealing surface of the jaws is 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 20 and 21 may be resilient. Figure 4(b) shows an alternative arrangement in which two planar sealing jaws are employed, a non-heated jaw (22) and a heated jaw (23) in which 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 lower temperatures than the portion 27 when in operation. Either of the jaws (20) and (21) may be resilient.

Figure 5 shows a heat sealing arrangement which may be used to provide a variation in peel strength by varying the dwell time. A 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 3 0 while continuing to seal against the other. In this case a jaw, preferably jaw 28, may be resilient.

Figure 6 shows a heat sealing jaw arrangement in which variation in peel strength is produced by a combination of variation in jaw pressure and temperature. r 244 7 The arrangement shown is similar to that shown in Figure 3(b), save 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 5 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 surface of 32 from a heating element. Either of the jaws may be resilient. 10 Figure 7 shows a heat sealing jaw arrangement in which variation in peel strength is produced by a combination of variation in jaw pressure and dwell time. A planar sealing jaw (34) is employed with a non-heated jaw (35) having a stepped sealing surface. The portion of the 15 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-heated jaw (35) is withdrawn the spring 37 extends 20 increasing the dwell time of the sealing surface 36 in contact with the preferably resilient jaw (34).

If in Figure 7 jaw 35 is resilient but jaw 34 and member 3 6 are not, or are more rigid, the contact pressure at the interface 34/36 will be higher than that at the 25 interface 34/35 when the jaws are fully closed together.

Claims (22)

244732 - 21 - what yvt cu.alu'1 13 glaimc

1. A closed package comprising one or more flexible water soluble or water dispersible polymeric sheets sealed to form an outer non-breachable seal and an 5 inner breachable seal.

2. A package according to claim 1 which comprises a space between the inner and outer seals.

3. A package acording to claim 1 in which the space contains substantially none of the contents of the 10 package.

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

5 . A package according to any one of the preceding claims in which the inner seal is of lower peel strength 15 than the outer seal.

6 . A package according to claim 5 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. 20

7. A package according to claim 5 or 6, divided into more than one compartment, each containing a portion of the contents of the package, by the or each inner seal.

8. A package according to claim 1, 2 or 3 in which the inner breachable seal is provided by a folded portion 25 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.

9. A package according to claim 1, 2 or 3 in which the inner breachable seal is provided by a gusset which is 3 0 tacked in place by a breachable seal.

10. 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 a space between the inner and outer seals. 3 5

11. A package according to any one of the preceding claims which comprises a breachable seal in the region of # ,c 5 10 15 20 25 24 4 7^2 - 22 - the package most likely to fail when dropped from a height of 1 to 2m.

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

13. A package according to claim 12 in which the or each water soluble or water dispersible polymeric sheet comprises a cold water soluble polyvinyl alcohol which is 4 0 to 99% hydrolysed or alcoholised polyvinyl acetate.

14. A package according to any one of claims 11 to 13 in which the contents are released in less than 10 minutes after contact with water.

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

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

17. A package according to claim 16 which contains from 5ml to 10 litres of liquid or gel.

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

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

20. A package according to claim 19, in which the 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/im.

22. A package according to claim 1 which substantially as hereinbefore described and illustrated in any one of the accompanying Figures 1 to 7. ftw-fiuhx....fctiicdLuSL Lmitert / il.e 2.;uiorised agents / J PARK & SON