Waste packaging device

0001The present invention is directed to a waste packaging system, a method of storing waste and to a film for use in this system and method.

0002A lot of waste products produce smells that are annoying to the environment. Examples are decayed food, kid nappies and cat litter.

0003In the prior art there are many films that could be used for protection from malodors. As it is well known in the art, the use of materials like EVOH, PVDC, polyacrylonitrile is recommended in order to not allow malodors escape from the container (eg bag or other configuration) and create an unpleasant atmosphere.

0004There are also a lot of known configurations of packing a certain length of film (eg 20 meters) in a compressed form (eg in a cassette). Examples of the representative cassettes are shown in <patcit id="pcit0001" dnum="US4934529A"><text>US 4,934,529</text></patcit> or <patcit id="pcit0002" dnum="US3536192A"><text>US 3,536,192</text></patcit>.

0005Generally the cassette comprises a tubular core, casing wall, cassette bottom and lid. The film is stored in an area between tubular core, casing wall and cassette bottom in a compressed configuration. The flexible tubing is dispensed from the cassette. After the malodorous item is thrown into the bag the core or the lid is rotated and the flexible tube is twisted so that it closes as hermetically as possible the waste/environment area. To dispose the next diaper the user opens the lid and inserts the diaper. The previous pack is pushed downward and a new knot is formed by twisting the tube above the newly deposited diaper. Thus the device stores the diapers in a series of individually wrapped packages in the storage chamber, each package being separated from adjacent packages by twists in the tube.

0006Separation of one piece of flexible film from the next by means of a rotary knife is preferred.

0007In the prior art as a general rule the separation of each piece of the film in which the smelly item is contained from the next piece of the film is done with a twisting mechanism. This twist separates in a "hermetic" way the one piece from the other.

0008That is to say, it is a problem in the prior art techniques that the twist is never really hermetic. Odour molecules being extremely small have the capability to escape through the folds so the odour starts to be noticeable after a few days. There is still a need for a more hermetic way to isolate each individual pack with the next one.

0009Methods based on heat sealing have been proposed in the prior art as for example in <patcit id="pcit0003" dnum="EP0005660A"><text>EP 0005660</text></patcit>. This concept is quite complicated as it uses sheaths to form discrete packages. The complex nature of this design makes it expensive to manufacture.

0010According to the prior art document <patcit id="pcit0004" dnum="US4869049A"><text>US 4,869,049</text></patcit>, the use of electricity is to be avoided anywhere near babies therefore this approach has not been commercially successful. So, twisting is the preferred option for separating one pack from the next.

0011Heat sealing and cutting as means to separate each pack from the next is also an object of <patcit id="pcit0005" dnum="US6516588B"><text>US 6,516,588</text></patcit>. In this reference there is no mention to the use of a low voltage battery. So, in general this method is not suitable enough as it involves electricity of high voltage and this is to be avoided for this sensitive application. Also, there is no reference to a low voltage battery.

0012Further, <patcit id="pcit0006" dnum="US6516588B"><text>US 6,516,588</text></patcit> does not refer to a suitable film that can be sealed efficiently and also through pleats and wrinkles (which are unavoidable during this kind of application). According to this application "the plastic tubing may be any plastic tubing known in the art" as described in col. 4 lines 30-31.

0013Further, patent <patcit id="pcit0007" dnum="US4612221A"><text>US 4,612,221</text></patcit> refers to a thin film incorporating oxygen barrier material. The film comprises a cling agent (additive which offers cling property) and is suitable to be used as a food wrap. There is no mention of the possibility of the film to be used in a waste packing system. Also the cling additive makes it unsuitable in a waste packing system due to a number of reasons such as difficult unwinding, waxy feeling, more complicated production process etc.

0014The present invention provides a safe and simple apparatus that is quick and easy to operate, that stores soiled nappies in flexible tubing in a very hygienic way so that they can be disposed collectively after a certain amount of time. It also provides a suitable plastic film to be used accordingly.

SUMMARY OF THE INVENTION

0015The present invention in one aspect is directed to a device comprising <ol id="ol0001" compact="compact"><li>1. a dispensing apparatus wherein a plastic film with weight/surface ration less than 20 grams per square meter is stored</li><li>2. a bin wherein a fusion seal apparatus is located</li><li>3. a fusion seal apparatus comprising a battery with a maximum voltage of 20V.</li></ol>

0016The battery may be rechargeable or non-rechargeable. Preferably, it is rechargeable.

0017Also another object of the present invention is a method of packing waste items by <ol id="ol0002" compact="compact"><li>1. pulling out plastic film of weight/surface ration less than 20 grams per square meter from a dispensing apparatus</li><li>2. putting a waste item in a suitable length of the film</li><li>3. closing hermetically the plastic film with the use of a fusion seal where the seal is between a part of the film and another part of the same or other film, where the sealed parts are put sequentially in a bin.</li></ol>

0018The fusion seal is preferably done with a fusion seal apparatus comprising a battery with a maximum voltage of 20V.

0019Also another object of the present invention is a plastic film comprising at least a layer comprising at least 50% per weight of polyethylene homopolymer and/or copolymer, where the weight/surface ratio is less than 20 grams per square meter and the film can be heat sealed with the thermal energy transferred with a battery with a voltage of less than 20 V.

0020In a preferred embodiment, the present invention provides a multilayer plastic film comprising at least <ol id="ol0003" compact="compact"><li>1. an outer layer comprising of polyethylene homopolymer and/or copolymer</li><li>2. an internal layer comprising at least one oxygen barrier material</li><li>3. an inner layer comprising polyethylene homopolymer and/or copolymer,</li></ol> where the weight/surface ratio is less than 20 grams per square meter and the film can be heat sealed with the thermal energy transferred with a battery with a voltage of less than 20 V.

0021In a preferred embodiment, the outer and/or inner layer comprise at least 50% per weight of polyethylene homopolymer and/or copolymer.

0022The film preferably does not contain any cling agents.

Definitions:

0023In this application the following definitions are used: <ul id="ul0001" list-style="none" compact="compact"><li>The term "waste" refers to any receptable that is useless and has to be disposed of properly. For example, the term waste includes diapers or other dirt.</li></ul>

0024The term "dispensing apparatus" refers to any apparatus where the film is stored before the application process. Examples are cassettes or reels.

0025The term "cassette" refers to any container wherein the film can be put. Often the film is in compressed form. The cassette is usually plastic and circular but other configurations may be possible.

0026The term "fusion seal" refers to the sealing of film by melting. A different kind of seal is by twisting the plastic film or by used an adhesive(in this latter case a kind of seal is made by pressure alone).

0027The term "bin" refers to a container where many waste packs are put one after the other. Each pack comprises a portion of the sealed film and of course the waste inside.

0028The term "film" refers to a flat or tubular flexible structure of thermoplastic material.

0029The term "voltage" between two points refers to the electrical driving force that could determine an electric current between these points.

0030The term "battery" refers to one or more electrochemical cells that convert stored chemical energy to electrical energy.

0031The term "rechargeable" refers to batteries that are designed in a way to be recharged and used multiple times.

0032The term "heat shrinkable" refers to a film that shrinks at least 10% in at least one of the longitudinal and transverse directions when heated at 90°C for 4 seconds. The shrinkability is measured in water according to ASTM 2732. For temperatures like 100°C or more, glycerine is used as a reference liquid.

0033The term "total heat shrinkability" refers to the sum of heat shrinkability at the MD direction and heat shrinkability at the TD direction. In all cases, ASTM 2732 is used for measurement of shrinkabilities.

0034The term "multilayer" refers to a film comprising 2 or more layers.

0035The phrase "longitudinal direction" or "machine direction" herein abbreviated "MD" refers to a direction along the length of the film.

0036The phrase "outer layer" refers to the film layer which comes in immediate contact with the outside environment (atmosphere).

0037The phrase "internal layer" as used herein refers to a film layer located between the outer and the inner layer of the multilayer film. It is not in contact with the atmosphere or the good to be packaged and usually comprises an oxygen barrier material.

0038The phrase "inner layer" refers to the film layer that comes in direct contact with the product packed. This is also called "sealing layer" as this layer must be hermetically sealed in order to protect the product from ingress of air.

0039The phrase "abuse layer" refers to a film layer whose main contribution to the film structure is to increase the abuse resistance property. The layer comprises materials which offer high impact strength to the film. Often, the abuse layer is an inner layer of the film, but it can form the outer layer as well. In some embodiments, it may form an internal layer as well.

0040The phrase "intermediate layer" refers to a film layer whose main contribution to the film structure is to increase the bonding between an oxygen barrier layer and another layer (eg abuse layer, inner layer, outer layer etc).

0041As used herein, the term "homopolymer" refers to a polymer resulting from polymerization of a single monomer.

0042As used herein, the term "copolymer" refers to a polymer resulting from polymerization of at least two different polymers.

0043As used herein, the term "polymer" includes both above types.

0044As used herein, the term "polyolefin" refers to any polymerized olefin, which can be linear, branched, cyclic, aliphatic, substituted or unsubstituted. More specifically, included in the term polyolefin are homopolymers of olefin, copolymers of olefin, copolymers of an olefin and a non olefinic comonomer(such as ester) etc.

0045Specific examples include polyethylene homopolymer, polypropylene homopolymer, polybutene homopolymer, ethylene alpha olefin copolymer, propylene alpha olefin copolymer, butene alpha olefin copolymer, ionomer, ethylene ester copolymer etc.

0046As used herein the term "polyethylene" identifies polymers consisting essentially of the ethylene repeating unit. The ones that have a density more than 0.940 are called high density polyethylene (HDPE), the ones that are have less than 0.940 are low density polyethylene (LDPE).

0047As used herein the phrase "ethylene alpha olefin copolymer" refers to polymers like linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), very low density polyethylene (VLDPE), ultra low density polyethylene (ULDPE), metallocene catalysed polymers and polyethylene plastomers and elastomers.

0048As used herein the term "homogeneous ethylene alpha olefin copolymers" refer to ethylene alpha olefin copolymers having a molecular weight distribution less than 2.7 as measured by GPC. Typical examples of these polymers are AFFINITY from DOW or Exact from Exxon.

0049As used herein the phrase "styrene polymers" refers to styrene homopolymer such as polystyrene and to styrene copolymers such as styrene-butadiene copolymers, styrene-butadiene-styrene copolymers, styrene-isoprene-styrene copolymers, styrene-ethylene-butadiene-styrene copolymers, ethylene-styrene copolymers and the like.

0050As used herein the phrase "ethylene methacrylate copolymers" refers to copolymers of ethylene and methacrylate monomer. The monomer content is less than 40%.

0051As used herein the phrase "ethylene vinyl acetate copolymer" or EVA refer to copolymers of ethylene and vinyl acetate.

0052As used herein the phrase "ethylene ester copolymer" includes any polymer made from ethylene and ester monomers. It is obvious that this term includes EVAs, EMAs and other polymers.

0053As used herein the term "oxygen barrier polymer" refers to polymers which have the property to limit the passage of oxygen through a film or a layer comprising the polymer. Common materials, are EVOH, PVDC or polyamide. Those polymers usually are comprised in at least one internal layer of the multilayer film.

0054As used herein, the term EVOH refers to saponified products of ethylene vinyl ester copolymers. The ethylene content is typically in the range of 25 to 50% per mol. All the later references to EVOH ethylene content will be in % per mol.

0055As used herein the term PVDC refers to a vinylidene chloride copolymer wherein a major amount of the copolymer comprises vinylidene chloride and a minor amount of the copolymer comprises one or more monomers such as vinyl chloride and/or alkyl acrylates and methacrylates.

0056As used herein the term "polyamide" refers to homopolymers and copolymers. Polyamide 6, polyamide 66, polyamide 12, polyamide 6/66, polyamide 6/12, polyamide elastomers, MXD polyamides and other copolymers are specifically useful for the invention.

0057As used herein the term "polyester" refers to polymers comprising terephthalate units. Examples of polyesters are PET (polyethylene terephthalate), PBT(polybutylene terephthalate), polyester elastomer (block copolymer comprising ester or ether units), PTT and other similar polymers.

0058As used herein, the term "ionomer" comprises the copolymers of ethylene and methacrylic or acrylic acid being metal neutralized. An example of such material is Surlyn from Dupont.

0059As used herein, the term "polypropylene" refers to polymers incorporating propylene structural units. Examples of these, are homo polypropylenes, random copolymers of propylene and ethylene, block copolymers of propylene and ethylene, copolymers or blends of propylene and rubber (such as blends of polypropylene and ethylene propylene rubber), propylene ethylene alpha olefin terpolymers and others.

0060These polymers may be isotactic, syndiotactic or atactic. Isotactic is preferred.

0061In line with the above definition, it is noted that for the purposes of the present invention, the term "inner layer" is to be regarded as an additional outer layer of the multilayer film, which is in direct contact with the item to be packaged (i.e. an outer layer of the film which is located on the inside after a packaging process, not exposed to the environment).

0062As used herein the term "substantially non resilient material" refers to materials or material compounds comprising at least 40% per weight inorganics like calcium carbonate, titanium dioxide, wollastonite, mica, glass fibers, dolomite and the like. The rest percentage per weight can be polyethylene, polypropylene, styrene polymer or other thermoplastic material.

0063All measurement methods mentioned herein are readily available for the skilled person. For example, they can be obtained from the American National Standards Institute at: <u>www.webstore.ansi.org</u>

0064All percentages are based on weight per weight ratio, except when otherwise stated.

DETAILED DESCRIPTION OF THE INVENTION

0065The present invention is directed to a device comprising <ol id="ol0004" compact="compact"><li>1. a dispensing apparatus where a plastic film of weight/surface ration less than 20 grams per square meter is stored</li><li>2. a bin where a fusion seal apparatus is located</li><li>3. a fusion seal apparatus comprising a battery with a maximum voltage of 20V.</li></ol>

0066The battery preferably is rechargeable.

0067Another aspect of the present invention is a method of packing waste items by <ol id="ol0005" compact="compact"><li>1. pulling out plastic film of weight/surface ration less than 20 grams per square meter from a dispensing apparatus</li><li>2. putting a waste item in a suitable length of the film</li><li>3. closing hermetically the plastic film with the use of a fusion seal where the seal is between a part of the film and another part of the same or other film, where the sealed parts are put sequentially in a bin.</li></ol>

0068The fusion seal is preferably done with a fusion seal apparatus comprising a battery with a maximum voltage of 20V.

0069A still further aspect of the present invention is a method of packing waste items by <ol id="ol0006" compact="compact"><li>1. pulling out plastic film of weight/surface ration less than 20 grams per square meter from a dispensing apparatus</li><li>2. putting a waste item in a suitable length of the film</li><li>3. closing hermetically the plastic film with the use of a fusion seal where the seal is between a part of the film and another part of the same or other film where the film is able to be sealed through pleats and wrinkles, where the sealed parts are put sequentially in a bin.</li></ol>

0070A preferred embodiment of the present invention is a method of packing waste items by <ol id="ol0007" compact="compact"><li>1. pulling out plastic film of weight/surface ration less than 15 grams per square meter from a dispensing apparatus</li><li>2. putting a waste item in a suitable length of the film</li><li>3. closing hermetically the plastic film with the use of a fusion seal where the seal is between a part of the film and another part of the same or other film where the film is able to be sealed through pleats and wrinkles,</li></ol> where the sealed parts are put sequentially in a bin.

0071Also another object of the present invention is a plastic film comprising at least a layer comprising at least 50% per weight of polyethylene homopolymer or copolymer, where the weight/surface ratio is less than 20 grams per square meter and the film can be heat sealed with the thermal energy transferred with a battery with a voltage of less than 20 V.

0072Also another object of the present invention is a multilayer plastic film comprising at least <ol id="ol0008" compact="compact"><li>1. an outer layer comprising polyethylene homopolymer and/or copolymer</li><li>2. an internal layer comprising at least one oxygen barrier material</li><li>3. an inner layer comprising polyethylene homopolymer and/or copolymer,</li></ol> where the weight/surface ratio is less than 20 grams per square meter and the film can be heat sealed with the thermal energy transferred with a battery with a voltage of less than 20 V.

0073In a preferred embodiment, one or both of the outer and inner layers comprise at least 50% per weight of polyethylene homopolymer and/or copolymer.

DISPENSING APPARATUS

0074A dispensing apparatus of the present invention preferably has the form of a cassette. Nevertheless, other dispensing apparatus are also possible in which a cassette is not used. For example the film can be wound in the form of a mini roll around a paper core. Alternatively, two such mini rolls may comprise the film in such a way that the film wound in the first mini roll will heat seal to the film that is wound in the second mini roll.

CASSETTE

0075In a preferred embodiment the cassette useful for the invention is circular in shape (see <figref idref="f0001">figure 1</figref>). Preferably it is made by plastic, eg polypropylene.

0076It is also possible to be manufactured from other means more friendly to the environment such as paper, biodegradable plastic or non biodegradable plastic where a percentage of "degrading" additives have been added.

0077Generally, the cassette comprises a tubular core (see reference number 14 in <figref idref="f0001">Figure 1</figref>), casing wall (see reference number 12 in <figref idref="f0001">Figure 1</figref>), cassette bottom and lid (see reference number 13 in <figref idref="f0001">Figure 1</figref>). The film is stored in an area between tubular core, casing wall and cassette bottom in a compressed configuration. The flexible tubing is dispensed from the cassette.

0078In a further preferred embodiment of the invention the cassette comprises a malodor counteractant useful for absorbing, adsorbing or masking the smell of the waste.

0079In a preferred embodiment of the invention the film inside the cassette the film is in compressed configuration.

SEAL APPARATUS

0080A preferred version of the sealing apparatus of the present invention is an apparatus capable of impulse sealing. An impulse sealer is a jaw sealer backed with resilient silicone rubber. Electric current flows through Nichrome ribbon stretched over one over one or both surfaces and covered with high temperature release film and fabric.

0081Another preferred version of the seal apparatus is wire or knife sealing. According to this method a hot wire or knife seals and cuts the film.

0082Other methods for the seal apparatus that could be used according to the invention include bar sealing, band sealing, ultrasonic sealing, friction sealing, gas sealing, contact sealing, hot melt sealing, pneumatic sealing, dielectric sealing, magnetic sealing, induction sealing, radiant sealing, solvent sealing etc. For these methods please refer to the Wiley Encyclopedia of packaging technology, edition 1997.

0083In a preferred embodiment of the invention the electric current necessary for the heat sealing and fusion is provided through a rechargeable battery. The voltage of the rechargeable battery is preferably equal or less than 20 V, even more preferably less than 16 V, even more preferably less than 12V.

0084In a preferred version of the invention the temperature for the heat seal is less than 100°C, preferably less than 90°C, preferably less than 80°C.

0085In a further preferred version of the invention, the sealing time is less than 5 seconds, more preferably less than 3 seconds, more preferably less than 1 second.

0086In a further preferred version of the invention, the cutting of each pack to the previous one is done simultaneously with the sealing by the use of a wire/knife configuration. In another version, there is no cutting. In this case all the packs are put together inside the bin in a single line.

0087The use of a rechargeable battery of low voltage assures a safe procedure that is more user friendly than household electricity.

0088Another alternative possibility of the invention is the use of more than one heat seal to make an individual pack. So two, three or four seals are possible.

0089In the case of three or four seals, the film should be in a "single sheet" configuration instead of "flexible tubing".

0090In <figref idref="f0002">figure 2</figref> there is further explanation of the sealing apparatus. The two sealing jaws (see reference number 23) are heat sealing the flexible tubular film. The sealing jaws are movable on a railway (see reference number 22) and the movement is controlled through as gear reducer (see reference number 21). This is also displayed in <figref idref="f0003">figure 3</figref> from another view.

0091The activation of the sealing mechanism can be done by the person using the apparatus preferably by pushing an activation mechanism (eg a button or a lever) either by hand or by foot. The activation mechanism provokes by preferably mechanical or pneumatic transmission system the movement of the sealing jaws therefore allowing the fusion seal to occur. Electrical transmission is also possible by using a battery as a source of power.

FILM CHARACTERISTICS

0092The basic characteristics a film should have in order to be used in the particular case are <ol id="ol0009" compact="compact"><li>1. Barrier to odours</li><li>2. To have the proper deadfold properties (non resilient) so that is compressed efficiently in the cassette if a cassette is used as a dispensing apparatus.</li><li>3. To have sufficient mechanical properties (eg tensile strength at break, elongation).</li><li>4. To have sufficient sealing properties as to be sealed with a low voltage rechargeable battery. Also the sealing properties must be sufficient to seal through wrinkles or pleats that are inevitable for this kind of application.</li></ol>

0093We have surprisingly found that all these features can be achieved with a very lightweight multilayer film with weight per surface ratio less than 20 grams per square meter, preferably less than 18 grams per square meter. This is extremely beneficial for the environment as multilayer films are extremely difficult to be produced with so small weight per surface.

0094In order for a film to be able to heat seal hermetically to itself or to other film with the power generated by a low voltage battery and also be able to keep the other critical characteristics (odour barrier, sealability through pleats and wrinkles, mechanical strength) it should combine the following characteristics: <ol id="ol0010" compact="compact"><li>1. Comprise an internal layer comprising at least one oxygen barrier material</li><li>2. Comprise one outer layer comprising more than 50% per weight polyethylene homopolymer and/or copolymer and one inner layer comprising more than 50% per weight polyethylene homopolymer and/or copolymer</li><li>3. Have a weight/surface ratio of less than 20 grams per square meter.</li><li>4. The film can be heat sealed with the thermal energy transferred with a battery with a voltage of equal or less than 20 V.</li></ol>

0095According to a further aspect the present invention is directed to a multilayer film with weight less than 15g/m² which: <ol id="ol0011" compact="compact"><li>1. Comprises a layer comprising at least one oxygen barrier material</li><li>2. Comprise one outer layer comprising more than 50% per weight polyethylene homopolymer and/or copolymer and one inner layer comprising more than 50% per weight polyethylene homopolymer or copolymer</li><li>3. The film can be heat sealed with the thermal energy transferred with a battery with a voltage of equal or less than 20 V.</li></ol>

0096According to a further aspect the present invention is directed to a multilayer film with weight less than 13g/m² which: <ol id="ol0012" compact="compact"><li>1. comprises a high oxygen barrier layer comprising at least one oxygen barrier material</li><li>2. comprise two outer layers comprising more than 50% per weight polyethylene homopolymer or copolymer</li><li>3. the film can be heat sealed with the thermal energy transferred with a battery with a voltage of equal or less than 20 V.</li></ol>

0097In a further preferred embodiment, the film comprises the construction:

OUTER LAYER /ABUSE LAYER /INTERMEDIATE LAYER/ BARRIER LAYER /INTERMEDIATE LAYER /ABUSE LAYER /INNER LAYER

0098In another preferred embodiment, the film comprises the construction

OUTER LAYER /INTERMEDIATE LAYER /BARRIER LAYER /INTERMEDIATE LAYER /INNER LAYER

Detailed description of layers:

BARRIER (INTERNAL) LAYER

0099In a preferred version of the invention, the oxygen barrier material in the barrier (internal) layer is EVOH, PVDC or polyamide. The EVOH used preferably has an ethylene content less than 48%, more preferably less than 44%, more preferably less than 38%, more preferably from 27 to 32% ethylene.

0100The oxygen barrier material preferably has a weight of less than 3 g/m², more preferably less than 2 g/m² and even more preferably less than 1.5 g/m².

OUTER LAYER

0101In a preferred version, the outer layer comprises at least 50% per weight polyethylene homopolymer or copolymer.

0102In a further preferred version, the weight of the outer layer is less than 6 g/m² more preferably less than 5 g/m².

0103In a further preferred version, the polyethylene is a copolymer or a blend of different monomers or polymeric structures. This blending may take place during polymerization or as a later stage.

0104In a further preferred version the polyethylene is a copolymer of ethylene and butene or a copolymer of ethylene and hexene or a copolymer of ethylene and octene.

0105In a further preferred version the polyethylene has a density of between 0.885 and 0.960 g/m³, more preferably 0.910 to 0.940 g/m³.

INNER LAYER

0106Preferred materials for the inner layer include polyethylene homopolymer or copolymers, such as low density polyethylene, high density polyethylene, ethylene ester copolymer, ethylene alpha olefin copolymer and ethylene propylene copolymers. Ethylene based ionomers and ethylene styrene copolymers are also possible. Ethylene alpha olefin copolymer is particularly preferred.

0107According to a further embodiment, the present invention is of the same configuration where the inner layer comprises a "substantially non resilient material" (SNR).

0108In a preferred version of the invention, the SNR material is at least 10 percent, preferably at least 20, preferably at least 30 percent per weight of the inner layer.

INTERMEDIATE LAYER

0109In the intermediate layers, typical adhesive resins like maleic anhydrite modified polyolefins may be used. Typical examples are BYNEL from Dupont and OREVAC from Arkema.

0110In another preferred version of the invention, polyamide could be used as intermediate layer.

ABUSE LAYER

0111In a multilayer configuration where abuse layers are also present, these layers may comprise polyethylene and polypropylene homopolymers or copolymers. Polyamides are also possible.

General

0112Additives well known in the art may be used in one or more layers of the present invention. Slip additives, antiblock additives, antifog, polymer processing aids may be used if pertinent. Antimicrobial additives may also be used in one or more of the layers to inhibit the microbe formation. Preferably the antimicrobial is put on the side where the waste is in direct vicinity.

0113In order to increase the mechanical properties the film may be crosslinked with one of the following methods.

0114E-beam radiation, gamma radiation, moisture crosslinking using silane grafting compounds, peroxide crosslinking.

0115The film may be in tubular form or sealed at the edges or single sheet configuration. Centrefold configuration is also possible.

0116The preferred production method for the film is the hot blown film method, which is well known in the art. Other methods like extrusion through flat cast die is also possible. The hot blown film method allows orientation of the plastic from the melt state. Biaxiallly oriented film such as those produced by double bubble or tenter frame method are not really efficient for the application during the much higher complexity of the process which renders the production cost much higher.

0117As outlined above, the inner and outer layers of the present invention are substantially free of "cling" additives meaning additives that allow the layer adhere to itself by pressing force without the need of fusion seal. Addition of such additives is costly and complicated. Also it makes the whole process much less friendly due to the tacky nature of the cling additive.

EXAMPLES

0118A 5 layer film is produced in a commercial hot blown film line with the following recipe <ul id="ul0002" list-style="none"><li>Inner layer, 80% EAO1+ 15% SNR1+ 5% ADDITIVES</li><li>Adjacent layer 100% ADH 1</li><li>Barrier layer EVOH 1</li><li>Adjacent layer 100% ADH 1</li><li>Outer layer 100% EAO1</li></ul>

See table 1

0119The thickness of the structure is 4/1.5/1.5/1.5/4 starting from the inner and going to the outer layer. The weight of the film is 12.145 g/m². <tables id="tabl0001" num="0001"><table frame="all"><title>TABLE 1</title><tgroup cols="3"><colspec colnum="1" colname="col1" colwidth="16mm" /><colspec colnum="2" colname="col2" colwidth="46mm" /><colspec colnum="3" colname="col3" colwidth="25mm" /><thead><row><entry valign="top">Type</entry><entry valign="top">Description</entry><entry valign="top">Density g/cm³</entry></row></thead><tbody><row><entry>EAO1</entry><entry>Ethylene octene copolymer</entry><entry>0.92</entry></row><row><entry>SNR1</entry><entry>Calcium carbonate compound</entry><entry>1.6</entry></row><row><entry>AD1</entry><entry>LLDPE mod. Adhesive tie</entry><entry>0.92</entry></row><row><entry>EVOH 1</entry><entry>EVOH with 32% ethylene</entry><entry>1.19</entry></row><row><entry>EVOH 2</entry><entry>EVOH with 29% ethylene</entry><entry>1.2</entry></row></tbody></tgroup></table></tables>

EXAMPLE 2

0120A 5 layer film is produced in a hot blown film commercial line with the following recipe <ul id="ul0003" list-style="none"><li>Inner layer, 80% EAO1+ 15% SNR1+ 5% ADDITIVES</li><li>Adjacent layer 100% ADH 1</li><li>Barrier layer EVOH 2</li><li>Adjacent layer 100% ADH1</li><li>Outer layer 80% EAO1+ 15% SNR1+ 5% ADDITIVES</li></ul>

0121The thickness of the structure is 5/1.5/1.5/1.5/3 starting from the inner and going to the outer layer.

0122The weight of the material is 12.385 g/m².

EXAMPLE 3

0123A 5 layer film is produced in a hot blown film commercial line with the following recipe <ul id="ul0004" list-style="none"><li>Inner layer, 80% EAO1+ 15% SNR1+ 5% ADDITIVES</li><li>Adjacent layer 100% ADH1</li><li>Barrier layer EVOH 2</li><li>Adjacent layer 100% ADH1</li><li>Outer layer 80% EAO1+ 15% SNR1+ 5% ADDITIVES</li></ul>

0124The thickness of the structure is 5/3/1.5/3/5 starting from the inner and going to the outer.

0125The weight of the material is 17.1 g/m².

TESTS

0126<ol id="ol0013" compact="compact"><li>1. Tensile strength and elongation test is done according to ASTM D 882.</li><li>2. Odour test is done in the way described below.</li></ol>

TEST 1.

0127Tensile strength and elongation is measured as per ASTM D882.

0128MD stands for machine direction, whereas TD stands for transverse direction. <tables id="tabl0002" num="0002"><table frame="all"><tgroup cols="5"><colspec colnum="1" colname="col1" colwidth="20mm" /><colspec colnum="2" colname="col2" colwidth="40mm" /><colspec colnum="3" colname="col3" colwidth="33mm" /><colspec colnum="4" colname="col4" colwidth="41mm" /><colspec colnum="5" colname="col5" colwidth="33mm" /><thead><row><entry valign="top">EXAMPLE</entry><entry valign="top">TENSILE STRENGTH(MD)</entry><entry valign="top">ELONGATION (MD)</entry><entry valign="top">TENSILE STRENGTH(TD)</entry><entry valign="top">ELONGATION (TD)</entry></row></thead><tbody><row><entry align="center">1</entry><entry align="center">22</entry><entry align="center">250</entry><entry align="center">21</entry><entry align="center">630</entry></row><row><entry align="center">2</entry><entry align="center">21</entry><entry align="center">225</entry><entry align="center">19.8</entry><entry align="center">550</entry></row><row><entry align="center">3</entry><entry align="center">25</entry><entry align="center">190</entry><entry align="center">23</entry><entry align="center">520</entry></row></tbody></tgroup></table></tables>

ODOUR TESTING

012910 soiled diapers are put in a film of the present invention and also in a commercially sold film. The commercially sold film is believed to be monolayer.

0130The packs are put in PVDC comprising bags, so the odour cannot escape during the time of the evaluation.

0131The bags are opened 3 days after the soiling of the diapers and smell was evaluated by a 5 member panel.

0132The packs made from examples 1 and 2 were found substantially less smelly than the commercially sold ones.

SEALING TESTING

0133The sealing testing was done in comparison with a commercial film specialized for the particular application with a weight/surface ratio of 21.9 g/m². For the testing two sealing jaws that used the energy produced by a battery of 20 V were used.

0134It was surprisingly found that the film of examples 1, 2 and 3 were able to seal efficiently even through wrinkles with the sealing apparatus. On the other hand, the film of 21.9 g/m² was not able to seal efficiently. If the sealing time was increased (something which is not desirable according to the invention) the seal was "burned".