NZ514808A

NZ514808A - Bag with inner sealable pouch and outer covering of composite layer of paper and polymer bonded together

Info

Publication number: NZ514808A
Application number: NZ514808A
Authority: NZ
Inventors: A Munem Mohammad Al-Shakarchi
Original assignee: Carter Holt Harvey Ltd
Priority date: 2001-10-16
Filing date: 2001-10-16
Publication date: 2004-07-30
Also published as: WO2003033370A1; UY27496A1; AR036889A1

Abstract

The bag has an inner plastic pouch capable of being heat sealed after insertion of powder or granules. A removable outer protective covering consists of a single composite layer of one or more layers of paper and one or more layers of polymer film bonded to the paper layer(s).

Description

<div class="application article clearfix" id="description"> 514808 InteiteMual Property Office of NZ 14 OCT 2002 RECEIVED NEW ZEALAND PATENTS ACT, 1953 No: 514808 Date: 16 October 2001 COMPLETE SPECIFICATION "Bag" We, CARTER HOLT HARVEY LIMITED, a company duly incorporated under the laws of New Zealand of640 Great South Road, Manukau, Auckland, New Zealand, do 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: FIELD OF THE INVENTION This invention relates to packaging and in particular bags used for the packing of powders or granules. Such bags may have an inner plastic pouch, which can be heat sealed once filled with product, surrounded and supported, by an outer bag. Typically the outer bag is formed from multiple layers of paper. In other forms the bag may not have a distinct inner pouch and a distinct outer bag. Such bags may be used to pack and transport resins, plastics granules, and in particular food grade materials such as milk powders, casein, powdered cheese, protein products, and a variety of food ingredients. BACKGROUND OF THE INVENTION Bags for transporting particulate materials can, whether of a bag within bag form or not may accommodate with different sizes a range of product quantities, eg; 5 to 50 kg. Bags used for the packaging of powders and granules, e.g. resins, casein, milk powder may contain within an inner plastics pouch about 25 kg of product. The transport of these bags involves the stacking of a number of bags on pallets. The bags need to provide protection from atmospheric moisture during storage and need also to provide sufficient tear or burst resistance during transportation and handling. Such bags have an internal pouch made of a plastics material, attached to at least one side of the outer covering, and are manufactured with an open top end, so the pouch can be filled with powder by the insertion of an appropriate nozzle into the pouch. Usually the outer covering is two or more layers of Kraft paper. When filled, the plastics pouch can be heat sealed, and the outer covering sealed (typically by adhesives) to enclose the inner pouch and protect it and its contents from leakage or from contamination by dirt, insects, or the like. In order to provide sufficient tear strength and burst resistance (if the bags are dropped onto a hard surface) most multi-ply bags make use of multiple layers of Kraft paper. Each layer of Kraft paper is typically in the range of 60 to 100 gsm in the case of three or four layers of paper, and is often in the range of 90 to 150 gsm in the case of two layers of paper. An increasing numbers of layers of Kraft paper on the outer bag, increases the strength of the bag, but also increases the weight and more importantly the cost of the bags. OBJECT OF THE INVENTION It is an object of the present invention to provide improved bags suitable for packaging powders or granules which will at least provide the public with a useful choice. It is an object for some embodiments of the present invention to provide improved bags suitable for packaging powders or granules within an inner pouch and surrounded by a removable outer covering, or one, which will at least provide the public with a useful choice. STATEMENT OF THE INVENTION In a first aspect the present invention consists in a bag formed from a laminate of at least one ply of paper and at least one ply of a polymer film the bag having a factory sealed ("bottom") end (eg; a block bottom, pinch bottom, etc.) and a customer closable mouthed end or a customer useable valved end.. Preferably the inside layer is of the or a ply of the polymer film Preferably said polymer film is a heat sealable polymer film. Preferably the bag is a lie flat bag. Preferably the laminated materials of the bag are biodegradable and/or repulpable. Preferably the thickness of the polymer layer(s) is from 12 to 75 microns and the paper layer(s) is or collectively is from 90 gsm to 200 gsm. In another aspect the invention provides a bag having an inner plastics pouch capable of being heat sealed after insertion of powder or granules, and a removable outer protective covering, wherein the removable outer protective covering consists of a single layer of composite material laminate consisting of at least one layer of paper, and at least one layer of at least one polymer film bonded to the paper layer(s). Preferably it is one layer only of the polymer film. The at least one polymeric film layer of the outer protective covering maybe or have a plastics material or plastics materials similar, identical or different to that or those of the plastics pouch. Although it is possible for the composite material to have more than one layer of paper and more than one layer of polymer, our preferred examples make use of one layer of paper and one layer of polymer film. Preferably the paper layer is the outer most layer of the outer protective covering. In some applications, the polymer film may be the outer most layer with the paper being printed prior to application of the polymer film. In other applications the paper is sandwiched between two polymer film layers. The paper layer can be any suitable paper and of a suitable thickness and strength depending upon the size and intended weight of the bag and the thickness and strength of the polymer film. It is preferred that the paper layer is linerboard or Kraft paper, and optionally may included recycled fibre. More preferably this outer paper layer is Kraft paper, and is preferably Kraft paper in the range of 90 gsm -150 gsm. This layer can be printed. It may also be provided with an anti-slip coating. Preferably the polymer layer is in the range of from 12 to 75 microns. Preferably the polymer film layer forms the inner surface of the outer protective covering. More preferably this polymer layer is an extruded film which is bonded to the Kraft paper during production of the outer most layer prior to assembly of the bag. Preferably the polymer film is chosen from the polymer films capable of being bonded to Kraft paper. More preferably the bonding process and the polymer films are chosen so that the composite material can be recycled by separating the paper pulp from the polymer film. Preferably the polymer film is biaxially oriented. The polymer film may be chosen from: (a) polyester, (b) nylon, (c) polyethylene, (d) polypropylene, and (e) mixtures of polyethylene and polypropylene. More preferably the film is either (a) polyester film or (b) is made up of low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, and different grades of polypropylene, or mixtures of any of the above polyethylene and polypropylene. In some of the examples, the film is a mixture of polyethylene and polypropylene. More preferably the film has a thickness of between 15 microns and 70 microns. It will be appreciated that the thickness or weight of the film layer and/or the Kraft paper layer will be modified depending upon the users requirements. However it is preferable that these two layers are bonded together, in such a way that it satisfies the minimum burst strength capable of surviving appropriate drop tests. For example an industry standard "vertical drop test" for milk powder bags is to drop the filled and sealed bag at ambient temperature and relative humidity conditions from a height of 1.2 metres onto its butt. Such a sealed bag must survive at least two drops of such a butt test without failure of the outer layer or the manufactured sealed end. In addition the product must remain within its pouch intact. Similarly an industry standard "side drop test" requires the sealed bags to be dropped, at ambient temperature and relative humidity conditions, such that the bag must survive a total of two drops - one drop test on each side, and preferably survive at least a total of four side drops (with two drops per side), from a height of 1.2 metres without failure of the outer ply or the sealed ends, and with the product remaining in its pouch intact at all times. The invention also encompasses a method of manufacturing such bags together with the appropriate inner pouch attached to at least one side of the outer covering, as will be discussed in more detail below and/or with reference to any one or more of the accompanying drawings of the accompanying drawings. In another aspect the invention provides a method of filling and sealing such bags. These and other aspects of this invention, which should be considered in all its novel aspects, will become apparent from description, which is given by way of example only, with the accompanying drawings, in which; Figure 1 illustrates apparatus for the determination of resistance to water penetration, a solution to be contained by the specimen bag laminate material placed over a filter paper capable of revealing water penetration, Figure 2 is a schematic view of a preferred bag having an inner pouch (not shown) and a single layers of composite covering material, Figure 3 illustrates the outer bag material where the plastics film is on the outside of the bag, Figure 4 illustrates the outer bag material, where the plastics film is on the inside of the bag, Figure 5 illustrates a gusset tear strip, showing the inside face, Figure 6 illustrates a gusset tear strip, showing the outside face, Figure 7 shows a gusset handle of the rip type, Figure 8 shows a gusset finger tear type, Figure 9 shows a gusset double perforation type, Figure 10 shows a complete bag showing a block bottom base with its inserted gusset and a valve fillable customer end (eg; suitable for cement), Figure 11 shows in section a structure of a composite material useful in the present invention, there being a polymeric film on the right had side, a Kraft paper layer on the left hand side and an adhesive layer interposed therebetween, Figure 12 shows a still additional variant where there is a Kraft paper layer on each of the outer sides and affixed to each such paper layer by an adhesive layer a single polymeric film, the overall structure providing a composite material sandwich, Figure 13 is an example of a bag useful for dairy powders, there being a polymer on the inside and, by way of example, 125 gsm Kraft paper on the outside, Figure 14 shows a further dairy type bag again with a polymer on the inside but this time with a 98 gsm Kraft paper outer layer, Figure 15 is a composite material dairy bag again as an example with a polymer on the outside layer and 125 gsm Kraft paper inner layer, Figure 16 shows an example of a composite material sandwich, Figure 17 is a possible configuration for a laminating process for manufacturing a sandwich structure, Figure 18 is an alternative laminating process, Figure 19 shows a flow diagram of a filling method for bag assemblies of the present invention, Figure 20 is a flow diagram schematic of the tubing and bottoming process, and Figure 21 shows details of a bottoming station. DETAILED DESCRIPTION Some examples of the invention are detailed below. The examples in respect of the outer protective covering make reference to a polymer film. For the invention, the polymer film maybe chosen from (a) polyester [such a polyethylene terephthalate, polytetramethylene terephthalate, polyethylene 2,6-naphthalate, and polyethylene-1,4-cyclohexylene dimethylene terephthalate, etc.], (b) polyamide [such as nylon 6, nylon 66, etc.], (c) polyethylene, (d) polypropylene, (e) polyvinyl chloride and (e) mixtures of polyethylene and polypropylene, or polyethylene terephthalate/polyethylene, or a blend of polyester and polyamide, such as polyethylene terephthalate and nylon may be employed. Polyester films are preferred for the polymeric film layer/layers of the invention when hot adhesive is required to bond the polymer film to Kraft paper layer, and also because of its physical properties including smoothness, strength, tear resistance and moisture barrier characteristics. According to a preferred embodiment of the invention, polyethylene terephthalate is a preferred polymer film, particular oriented polyethylene terephthalate which has been stretched biaxially. The present invention also encompasses compositions derived from other blends of polymers. These compositions tend to provide compatible or semicompatible blends having good thermomechanical integrity, mechanical properties, and/or melt processability. In some of the examples, the film is a mixture of polyethylene and polypropylene [in different percentage ratio from 5:95 to 95:5]. When the polyethylene terephthalate which has been stretched biaxially. The present invention also encompasses compositions derived from other blends of polymers. These compositions tend to provide compatible or semicompatible blends having good thermomechanical integrity, mechanical properties, and/or melt processability. In some of the examples, the film is a mixture of polyethylene and polypropylene [in different percentage ratio from 5:95 to 95:5]. When the polyethylene percentage ratio is about 60% the hot adhesive either reduced, or not required due to its bonding ability to Kraft paper (self-bonding). More preferably the film has a thickness of from about 12 microns (12 ) to about 75 microns (75 micrometers). Figures 17 and 18 show a couple of process configurations. In Figure 17 there are shown, kraft paper unwind (1), polymer film unwind (2), adhesive station (3), press section (4), dyring station (5), slitting station (6), rewind (7), additional unwind station (8) and additional adhesive station (9). In Figure 18 there are shown, kraft paper unwind (10), polymer film unwind (11), heating stations (12), press rolls (13), chilling station (14), rewind (15) and slitting station The inner pouch can be of any suitable plastics material and can be from one or more of the materials mentioned earlier and including the following materials, low density polyethylene, linear low density polyethylene, medium density polyethylene, and resins with gas barrier properties, such as ethylene vinyl alcohol, polyamide (nylon), etc. The process for barrier film production is preferably multilayer blown film extrusion. The forming of a bag of the present invention can be by a procedure shown by way of Figure 19 in which 33 is a de-aireator, 34 is a vibrating conveyor/weighing/fine filling station, 35 is a neck strength stretch station, 36 is a heat sealing zone to seal the inner pouch, 37 involves scoring wheels to score the inner pouch, 38 is the hot melt adhesive system reactivation, 39 involves folding skis, 35 involves pressure rollers and 36 involves a weight station, metal detection station and warehousing. Figure 20 provides a schematic of tubing station with 37 depicting a roll shaping (16). 'I ^cILECTUAL PROPERTY OFFICE OF N.Z. 1 4 APR 2004 -9- and 54 is a take off area. Reference herein to "stations" is not to be taken as meaning that the process to be performed at any such a stage must necessarily involve a stationery web or stationery apparatus. Reference to "station" therefore should be interpreted as meaning a stage of the sequence in the scheme of things irrespective of whether or not it is continuous or continual in its operation. The examples are of composite materials/bags which have proven and/or are believed to provide useful options to users and to satisfy performance requirements. Example 1: A milk powder bag is formed with an internal polyethylene pouch and an outer protective covering (bag) of a composite material. The outer bag has a pair of broad faces, i.e.; front and back faces, joined by side faces which are joined at top and bottom ends, which bag as a composite material made up from Kraft paper outer layer and a plastic inner layer. The outer layer has a Kraft paper weight in the range from 90 - 150 gm per m2, and more preferably 100 to 130 gm per m2. The Kraft paper layer provides a soft, shock-absorbing layer. In addition, the paper is resistant to tear, and heat. The inner layer is conveniently provided as a polymer film, for instance a polyethylene/polypropylene film, on this Kraft paper. The inner surface of the Kraft paper layer is coated with the adhesive and laminated to the polyethylene/polypropylene film layer. Alternatively, the adhesive maybe coated on the polyethylene/polypropylene layer and laminated to the inner surface of the Kraft paper layer. In any case the polyethylene/polypropylene layer provides resistance to tear, and puncture, a gas barrier, and an odour barrier (to protect the product packaged from picking up off-odours). It is also the layer and material used to form hermetic seals through thermal welding (or otherwise) since it forms the inner surface for the bag. The film, or coating plastic "polyethylene/polypropylene" are used herein to describe a number of sealant materials, such as low density polyethylene, linear low density polyethylene, medium density polyethylene and high density polyethylene, and Intellectual Property Office of NZ 16 OCT 2002 10 RECEIVED outer wall of the bags while the plastic web (18) forms the inner wall. The web (17) consists of Kraft paper only which provides the outer layer of the bags with a weight of 125 gm/m2 covered on one surface (which becomes the interior of the outer layer) with 15 to 50 gm/m2 of polyethylene/polypropylene mixture film providing a vapour barrier, and tear resistance. The two webs are formed in known manner into a continuous flattened tube. The forming of webs into a continuous multi-layer tube which is then cut to length and the subsequent cutting, creasing and gluing of the end portions of each of the cut lengths so as to form bags are well known operations in paper bag manufacture and can be carried out on automatic machinery. The adhesive (gluing) layer provides secure bonding of the film layer to the Kraft paper layer. The adhesive selection of choice is polyester-urethane, due to its heat and chemical resistance. This adhesive is applied to the film in solution, or to Kraft paper layer. The liquid carrier is driven off using hot air leaving a thin layer of the adhesive. The adhesive is then thermally bonded to the second layer. Other adhesives and other laminating processes are well known in the converting industry and may be useful for the production of the laminated material of the package of this invention. An example is that of Figure 17. One example is the "polymounting-process", where molten polymer instead of adhesive is used to bond two layers together, may be used to form the milk bag of this example. For example in the "polymounting-process", a web of paper and a web of plastic film are passed into and through the nip of a pair of nip rolls, and layer of molten polymer-impregnating and bonding agent is extruded into the nip between the webs on the entry side of the nip. One or more of the speed of the webs, the temperature of the molten polymer, the pressure or spacing of the rolls at the nip, and the rate of extrusion is or are controlled relative to the porosity and surface characteristics of the paper web such that a substantial portion of the molten polymer impregnates partially into and becomes part of the paper web, and a substantial portion lies outwardly of the surface of the paper web and solidifies to form an enhanced surface. This surface is essentially a new surface, to which becomes part of the paper web, and a substantial portion lies outwardly of the surface of the paper web and solidifies to form an enhanced surface. This surface is essentially a new surface, to which the film is bonded and on which it is supported clear of the paper surface. There is collected from the nip rolls a composite comprising paper partially impregnated with solidified polymer, a contiguous layer of solidified polymer having the new surface outwardly of the paper surface, and the plastic film bonded to the new surface. An example of such a bonding agent is molten polyethylene. See Figure 18. TESTS The outer composite bag material made in accordance with Example 1 can be tested as follows: Method of Test for the Determination of Fatty Acids: Procedure: Preparation of Extract Cut a sample of the paper into pieces approximately 10 mm square. Weight accurately approximately 30g of this prepared sample and place directly into a Soxhlet apparatus of 200 cm 3 capacity, without thimble. Extract the sample with diethyl ether for (16 ± 1) hours on a water bath. The diethyl ether shall syphon from the Soxhlet apparatus approximately 9 times per hour. Filter the extract through a No. 1 Whatman filter-paper, make up to 150 cm 3 with diethyl ether in a measuring cylinder and divide into 2 portions in separate flasks, one of 50 cm 3 (portion A) and one of 100 cm 3 (portion B). Total acidity (portion A). Evaporate the diethyl ether from the extract until the volume is reduced to approximately 10 cm 3 then add 20 cm 3 of the methylated spirit. Boil the mixture under a reflux condenser for (10 ± 1) minutes, cool, add a few drops of phenolphthalein indicator solution, and titrate with 0.1 mol/1 sodium hydroxide solution and record the volume (VI) cm 3. Carry out a blank titration on the reagents and record the volume (V2) cm 3. Total acidity as oleic acid (C17H33COOH), % = (VI - V2) x 2.823 ml where ml = mass of sample, in volume of extract taken, i.e; approx. 10 g. Resin acidity (portion B). Evaporate the diethyl ether from the extract and then add 30 cm 3 of petroleum spirit to the residue. Boil the mixture under a reflux condenser for 30 minutes. After cooling, filter the extract into a separating funnel through a No. 41 Whatman filter paper. Wash the flask and filter paper with petroleum spirit then add the washings to the separating funnel. Wash the petroleum spirit in the separating funnel with three successive quantities of 20 cm 3 of water, then run off the petroleum spirit into a flask. Evaporate the petroleum spirit from the flask, dry the residue for 20 minutes at 95 to 100 °C and then add 30 cm 3 of methanol to which has previously been added 2 cm 3 of sulfuric acid. Boil the mixture under a reflux condenser for (180 ± 10) seconds and immediately add 50 cm 3 of the sodium chloride solution. Cool the flask and transfer the contents to a separating funnel. Wash the flask 3 times with 20 cm 3 portions of diethyl ether, adding the washings to the separating funnel. Shake the funnel vigorously and, after allowing the layers to separate, run off the aqueous layer into a second separating funnel. Extract the aqueous layer with two further separate 20 cm 3 portions of ether, combining the ether extracts in the original separating funnel. Wash the combined extract with successive 20 cm 3 portions of sodium chloride solution and continue washing until one portion, to which has been added a few drops of phenolphthalein indicator and one drop of 0.1 mol/1 sodium hydroxide solution remains pink. Transfer the washed diethyl ether extract to a flask and evaporate off the diethyl ether until about 10 cm 3 remain. Add 20 cm 3 of the methylated spirit and boil the mixture under a reflux condenser for 10 minutes. Cool the flask, add a few drops of phenolphthalein indicator solution and titrate the contents with 0.1 mol/1 sodium hydroxide solution and record the volume (V3) cm 3. Carry out a blank determination on the reagents and record the volume (V4) cm 3. - 13 - Calculation Resin acidity as oleic acid (C17H33COOH) per cent = (V3 - V4) x 2.823 m2 where m2 = mass of sample in volume of extract taken, i.e; approx. 20 g. Calculation Fatty acids per cent = the different between the per cent contents of total acidity and per cent resin acidity. Method of Test for the Determination of Thickness of Polyethvlene/polvpropylene Reagents Alcoholic potassium hydroxide solution 10g/100cm 3. Procedure: Cut 10 specimens, each approximately 75 mm square, diagonally across the sample. Immerse each specimen in the alcoholic potassium hydroxide solution. After approximately 20 minutes remove the specimens from the solution and carefully lift the polyethylene/polypropylene coating from the paper. Wash the polyethylene/polypropylene with distilled water and dry between filter papers. Condition the polyethylene/polypropylene using the conditioning atmosphere of (23 ± 1)°C and relative humidity (50 ± 2)% and then determine the thickness of each specimen in accordance. The mean value of the ten determinations is the thickness of the polyethylene/polypropylene. Method of Test for the Determination of Resistance to Water Penetration Procedure: Condition the material for at least 24 hours. Take a square of the conditioned material of suitable size and fold (not crease) along -14- one diagonal. Place the 2.0 kg weight flat side down on the centre of the fold and leave for (30 ±1) seconds. Remove the weight, open the specimen, fold along other diagonal with the reverse side folded in and apply the weight to the centre of the fold and allow to remain for (30 ± 1) seconds. After removing the weight unfold the specimen. Lay the prepared specimen on a sheet of filter paper and clamp them between the rubber faced annular discs of (150 ± 5) mm internal diameter as shown in Fig. 1. Using eosin solution, apply a hydrostatic pressure of (100 ± 2) mm of solution to the exposed area of the specimen, ensuring that the exposed area of filter paper remains out of contact with any object. Note: The Specimen and filter paper shall be securely clamped between the rubber washers by any suitable method. (Dimensions in millimetres). After the hydrostatic head has been maintained for 24 hours, examine the exposed area of the filter paper for penetration by the eosin solution. Method of Test for the Determination of Strength of Heat Sealed Joint Preparation of Heat-sealed Joints From the conditioned material cut eight test pieces (150 ± 5) mm by (25 ± 0.5) mm. In duplicate accurately superimpose two of the test pieces with the polyethylene coated surfaces in contact and two pieces with one polyethylene coated surface in contact with an uncoated surface. Heat-seal the four pairs of test pieces over a length of approximately 25 mm at one end at a temperature of(135±5)°C under a load of (2 ± 0.2) kg for (3 ± 0.5) seconds. Note: It may be necessary to adjust the temperature and/or pressure settings to achieve optimum sealing. If so the actual temperature and/or pressure settings used shall be included in the report. Procedure: Strength of Heat-sealed Joint of Material (Polyethylene/+ to Polyethylene/+). Using the test pieces heat-sealed with the polyethylene coated surfaces in contact, attach a (150 ± 2) g weight to one unsealed end of the joined strips. Suspend the - 15 - assembly by the other unsealed end at (60 ± 1) °C for (24 ± 0.25) hours. Report the mean separation of the heat-sealed j oints to the nearest millimetre. Procedure: Strength of Heat-sealed Joint of Material (Polyethylene/polypropylene to Paper). Condition the test pieces heat-sealed with the polyethylene coated surface in contact with the uncoated surface for at least 24 hours. The Joints shall then be broken using a tensile tester. Report the mode of failure of the joints. Method of Test for the Determination of Delamination in Water Procedure: Immerse a suitably sized piece of material in water at a temperature of (20 ± 5)°C for (60 ± 5) minutes. Remove from water and visually inspect for signs of delamination or breakdown. Method of Test for the Determination of Delaminatioii at High Temperature and Humidity Procedure: Place a suitably sized piece of material in the humidity chamber with the temperature and humidity maintained at (30 ± 3)°C and (90 ± 2)% r.h. respectively. After (168 ± 0.5) hours remove from the chamber and visually inspect for delamination. Table of Different Thicknesses: From these and other test we have prepared table A to show the properties of different thicknesses of composite material made in accordance with Example 1. -16- Table A Thickness Schedule Thickness (total) ±10%, mm Thickness of polyethylene (minimum), mm Grammage, g/m2 Bursting strength (minimum) kPa Tensile strength (minimum), kN/m Tear strength (mimimum), mN Machine direction Cross direction Machine direction Cross direction 90 25 65-80 240 5.3 2.6 700 900 150 25 110-130 380 6.1 3.5 1300 1400 250 25 155 - 185 450 8.8 5.3 2300 2400 300 50 190-220 515 11.4 6.1 2900 3000 Example 2 See Figure 4. Two webs (rolls) are used to form bags. In this case the paper web (19) forms the outer wall of the bags while the plastic web (20) forms the inner wall. The web 19 consists of Kraft paper only which provides the outer layer of the bags with a weight of 125 gm/m2 coated on one surface (which becomes the interior of the outer layer) with 15 to 50 gm/m2 of polyethylene/polypropylene mixture providing a vapour barrier, and tear resistance. The two webs are formed in a known manner into a continuous flattened tube. The forming of webs into a continuous multi-layer tube which is then cut to length and the subsequent cutting, creasing and gluing of the end portions of each of the cut lengths so as to form bags are well known operations in paper bag manufacture and can be carried out on automatic machinery. The adhesive (gluing) layer provides secure bonding of the film layer to the Kraft paper layer. The adhesive selection of choice is polyester-urethane, due to its heat and chemical resistance. This adhesive is applied to the film in solution or to the Kraft paper layer. The liquid carrier is driven off using hot air leaving a thin layer of the adhesive. The adhesive is then thermally bonded to the second layer. Other adhesives and other laminating processes are well known in the converting industry and may be useful for the production of the laminated material of the package of this invention. For example a "polymounting-process", where molten polymer instead of adhesive is used to bond two layers together, may be used to form the milk bag of this project. - 17- Example 3: See Figure 3. Two webs (rolls) are used to form a laminate material for use in the manufacture of the bag outer. A paper web (17) is used as the inner substrate layer while a plastic web (18) is secured to the substrate and forms the outermost layer of the laminate. This outermost layer will become the outside surface of the formed bag. The finished bag as shown in Figure 14 has a single wall outer bag surrounding and attached to an inner food grade plastics pouch. During manufacture the inner plastics pouch is formed as an open topped pouch with a closed heat sealed base, and the pouch is releasable attached to the bag outer by adhesives or the like. Preferably this is achieved by lightly tacking one side of the pouch to parts of the inner surface of the bag outer by used of a hot melt EVA or similar adhesive, or a Henkel Z 9835™ or Mercaptor Technology EM 186™ or similar adhesive. This adhesive is preferably strong enough to locate and hold the pouch in place during manufacture, transport and filling but allow the pouch to readily detached from bag outer, at the bags destination when the bag outer is removed. The web 17 consists of Kraft paper only, which provides the innermost layer of the bag outer. Preferably the Kraft paper is 125 gm/m2. This Kraft paper layer can be printed prior to attachment to the plastics web. By covering the printed side with a transparent layer of a plastics material such as a polyethylene/polypropylene layer the printed surface can be protected against moisture and the plastics layer can protect against ink bleeding or abrading as the bags are handled. Preferably the plastics layer is a biaxially oriented transparent or translucent layer of 15 to 50 gm/m2 of a polyethylene/polypropylene mixture which provides both a vapour barrier, and tear resistance. (This gives a film thickness of 15 microns to 79 microns). The adhesive (gluing) layer provides secure bonding of the film layer to the Kraft paper layer. The adhesive selection of choice is a polyester-urethane, due to its heat and chemical resistance. This adhesive is applied to the film in solution or to the Kraft paper layer. The liquid carrier is driven off using hot air leaving a think layer of the adhesive. The adhesive is then thermally bonded to the second layer as they pass through a nip Intellectual Property Office of NZ 1 o MAY 2004 18 roller. Other adhesives and other laminating processes are well known in the converting industry and may be useful for the production of the laminated material of the package of this invention. For example a "polymounting-process", where molten polymer instead of adhesive is used to bond two layers together, may be used to form the outer bag material as in Figure 17. Preferably the nip roller has a contoured surface (e.g. it may be etched or pitted by a laser or other means) to create a textured surface to the plastic layer to increase the friction between adjacent stacked bags. The degree of texture and hence surface roughness may be varied depending upon the thickness and material of the film and the shape and size of the resultant bags. Example 4: A web of paper and web of polymer plastic film (as made in the process of Figure 18) are passed into and through the nip of a pair of nip rolls, and a layer of molten polymer (preferably molten polyethylene) is extruded into the nip between the webs on the entry ' side of the nip. One or more of the speed of the webs, the temperature of the molten polymer, the pressure or spacing of the rolls at the nip, and the rate of extrusion is or are controlled relative to the porosity and surface characteristics of the paper web such that a substantial portion of the molten polymer impregnates partially into and becomes part of the paper web. A substantial portion lies outwardly of the surface of the paper web and solidifies to form an enhanced surface. This surface is essentially a new surface to which the film is bonded and on which it is supported clear of the paper surface. There is collected from the nip rolls a composite comprising paper partially impregnated with solidified polymer, a contiguous layer of solidified polymer having the new surface outwardly of the paper surface, and the plastic film bonded to the new surface. Example 5: The resulting laminates of the previous examples can be formed into a continuous flattened tube about an inner plastics pouch. Unlike prior art bags the bag outer is a - 19- formed from a single layer of the composite plastics/Kraft laminate. As the laminate is folded to form a bag a longitudinal seal is made between the overlapping layers down the length of the seam of the bag (as the seal is made between the Kraft surface contacting the opposite plastics surface. Preferably this seal is effected by two lines of adhesive. More preferably one line is a hot melt adhesive (e.g. a blend of EVA) and the second line is formed from a solvent based adhesive where both types of adhesive are adapted to seal the plastics to the Kraft layer. Preferably the base of the bag is a block base. Preferably the outer bag has a specially designed easy open portion to facilitate the manual opening and removal of the outer bag at its destination. The outer covering of the bag can be folded and cut to length. The steps of cutting, creasing and gluing of the base portions of each of the cut lengths, can all be carried out on automatic machinery. Figure 2 shows a typical bag produced from the material of the examples. It is shown schematically to comprise a bag having a base (21), a main face (22) and a flap (23). The front face (22) of the bag stops at line (25), with the flap (23) of the rear face protruding above the tope of the main face (22). The top of the main face (22) and the inside of the flap (23) may be provided with appropriate fastening means, preferably a heat resealable adhesive (preferably a heat resealable hot melt adhesive) which can be allowed to cure on the bag during manufacture, but which can during the filling of the bag allow the top of the bag to be folded over, and sealed through the application of heat. Preferably the top of the bag includes some form of tear stip (28) formed at or close to the fold line of the flap (23) to facilitate opening of the outer bag (20), and separation of the outer bag from the inner pouch (not shown) when the product reaches its destination. During manufacture the outer composite covering material is folded over the pouch, resulting in a longitudinal seam (29) from the folding over of the outer covering material. This seam can be closed by appropriate adhesives and is discussed above. Alternatively, the easy opening feature may involve a tear strip or removable portion -20- situated elsewhere on the bag. For example a tear strip may be provided along or in associated with the longitudinal seam (29), or may form part of the base of the bag. We prefer to provide the tear strip in association with the top of the bag, as described in the co-pending patent application by Carter Holt Harvey Limited, although we have designed a number of easy open bottom portions of the bag, some of which are described below. In examples 2 and 4 the polymer film (either polyethylene/polypropylene or polyester) is used as the inside of the bag as shown in Figure 2. This has the advantage that the Kraft paper provides a soft, shock absorbing layer on the outside which can be readily printed. The Kraft paper is generally resistant to tearing, and to heat. The inner polymer film layer (polyethylene/polypropylene or polyester) provides additional strength for the Kraft paper, as it is securely bonded thereto, and provides resistance to tearing, to puncturing, provides a gas barrier, and an odour barrier to protect the product packaged in the inner pouch from picking up off odours. The inner polymer film layer is also the layer which can be used to form hermetic seals through heat sealing (or otherwise) since if forms the inner surface of the bag. The material of example 3 can be used to form a bag with a plastics outer layer. In most cases it is preferable the inner pouch is formed of a plastics material such as HDPE (with or without special barrier layers) having a lower melting point or sealing point than the inner most film of the outer Kraft paper bag as it is desirable that heat sealing of the inner pouch, once the pouch has been filled, is effected through the use of heat sealing bars applied to the outer Kraft paper bag so the heat is transmitted through to the inner pouch. In some cases it might be preferable to include a anti-sealing coating, or layer of material which will prevent adhesion between the inner pouch and the innermost film of the outer Kraft paper at the point where heat sealing will take place. Example 6: A milk powder bag (Figure 13) is formed with an internal polyethylene pouch and an outer protective covering (bag) of a composite material. The outer bag has a pair of broad faces, i.e. front and back faces, joined by side faces which are joined at top and -21 - bottom ends, which bag has a composite material made up from Kraft paper outer layer and a plastic inner layer. The outer layer has a Kraft paper weight in the range from 90 - 200 gm per m2. In our example the outer layer has a Kraft paper weight of 125 gm per m2. The Kraft paper layer provides a soft, shock-absorbing layer. In addition, the paper is resistant to tear, and heat. The inner layer is conveniently provided as a polymer film, for instance a polyethylene/polypropylene film, on this Kraft paper. The inner surface of the Kraft paper layer is coated with the adhesive and laminated to the polyethylene/polypropylene film layer. Alternatively, the adhesive may be coated on the polyethylene/polypropylene layer and laminated to the inner surface of the Kraft paper layer. In any case the polyethylene/polypropylene layer provides tear and puncture resistance, a gas barrier, and an odour barrier (to protect the product packaged from picking up off-odours). It is also the layer and material used to form hermetic seals through thermal welding (or otherwise) since if forms the inner surface for the bag. The film, or coating plastic "polyethylene/polypropylene" are used herein to describe a number of sealant materials, such as low density polyethylene, linear low density polyethylene, medium density polyethylene and high density polyethylene, and different grades of polypropylene. Two webs (rolls) are used to form bags. In this case paper web (55) forms the outer wall of the bags while the plastic web (56) forms the inner wall (Figure 11). The web (55) consists of Kraft paper only which provides the outer layer of the bags with a weight of 125 gm/m2 covered on one surface (which becomes the interior of the outer layer) with 15 to 50 gm/m2 of polyethylene/polypropylene mixture film providing a vapour barrier, and tear resistance. The two webs are formed in known manner into a continuous flattened tube. The forming of webs into a continuous multi-layer tube which is then cut to length and the subsequent cutting, creasing and gluing of the end portions of each of the cut lengths so as to form bags are well known operations in paper bag manufacture and can be carried out on automatic machinery. The adhesive (gluing) layer (57) provides secure bonding of the film layer to the -22- Kraft paper layer (Figure 11). The adhesive selection of choice is polyester-urethane, due to its heat and chemical resistance. This adhesive is applied to the film in solution, or to Kraft paper layer. The liquid carrier is driven off using hot air leaving a thin layer of the adhesive. The adhesive is then thermally bonded to the second layer. Other adhesives and other laminating processes are well known in the converting industry and may be useful for the production of the laminated material of the package of this invention. For example a "polymounting-process", where molten polymer instead of adhesive is used to bond two layers together, may be used to form the milk bag of this project. For example in the "polymounting-process", a web of paper and a web of plastic film are passed into and through the nip of a pair of nip rolls, and a layer of molten polymer-impregnating and bonding agent is extruded into the nip between the webs on the entry side of the nip. One or more of the speed of the webs, the temperature of the molten polymer, the pressure or spacing of the rolls at the nip, and the rate of extrusion is or are controlled relative to the porosity and surface characteristics of the paper web such that a substantial portion of the molten polymer impregnates partially into and becomes part of the paper web, and a substantial portion lies outwardly of the surface of the paper web and solidifies to form an enhanced surface. This surface is essentially a new surface, to which the film is bonded and on which it is supported clear of the paper surface. There is collected from the nip rolls a composite comprising paper partially impregnated with solidified polymer, a contiguous layer of solidified polymer having the new surface outwardly of the paper surface, and the plastic film bonded to the new surface. An example of such a bonding agent is molten polyethylene. Example 7: It will be appreciate that although the inner pouch will be tacked to perhaps one side of the inside of the outer laminated plastics/Kraft paper bag (by a suitable adhesive such as "spots" of a hot-melt adhesive), the outer laminated plastics/Kraft paper bag can be readily removable from the inner pouch at the products destination, so that the outer covering and any dirt associated therewith can be removed before the product in its sealed -23- Intel I actual Properly Office of NZ 10 MAY 2004 inner pouch is opened in an appropriate hopper to release is contents. v* ^ This removal of the outer bag is facilitated by the design of an easy open portion, which is preferably included at the top of the bag. However, it is also possible to provide this elsewhere, and in the following drawings we show a number of alternative designs of the easy opening position. Figures 5 and 6 show the inside and outside faces of a gusset type tear strip formed on the base of the bag. Figure 7 shows a gusset with a handle-rip type on the base of the bag. Figure 8 shows a gusset with a finger tear type on the base of the bag. Figure 9 shows a gusset with a double perforation for the base of the bag. Figure 10 illustrates a schematic view of a completed bag showing its block bottom base with its inserted gusset and a valved customer end (eg; that which self seals when filling with, for example, cement is complete. Example 8: A milk powder bag is formed with an internal polyolefin polymer pouch and an outer protective covering (bag) of a composite material (Figure 14). The outer bag has a pair of broad faces, ie; front and back faces, joined by side faces which are joined at top and bottom ends, which bag has a composite materials made up from Kraft paper outer layer and a biodegradable plastic inner layer. The outer layer has a Kraft paper weight in the range from 90 - 200 gm per m2. In our example the outer layer has a Kraft paper weight of 98 gm per m2. The Kraft paper layer provides a soft, shock-absorbing layer. In addition, the paper is resistant to tear, and heat. The inner layer is conveniently provided as a polymer film, for instance a Cargill Dow EcoPLA® a polylactic acid polymer, or DuPont Biomax® hydro/biodegradable polyester (proprietary aliphatic polyesters). The inner surface of the Kraft paper layer is coated with the adhesive and laminated to the biodegradable polyester film layer. Alternatively, the adhesive may be coated on the biodegradable polyester film layer and laminated to the inner surface of the Kraft paper layer (Figure 11). In any case the biodegradable polyester layer provides puncture -24- and tear resistance, a gas barrier, and an odour barrier (to protect the product packaged from picking up off-odours). It is also the layer and material used to form hermetic seals through thermal welding (or otherwise) since it forms the inner surface for the bag. The film, or coating plastic "biodegradable polymers" are used herein to describe a number of sealant materials, such as: 1. BASF Ecoflex® is an aliphatic-aromatic copolyester. 2. DuPont Biomax® hydro/biodegradable polyester (proprietary aliphatic polyesters). New family or highly versatile polymers based on polyethylene terephthalate (PET) technology. 3. Cargill Dow's NatureWorks® PLA {PLA Polymer 4041D] is made from the lactic acid fermented from corn starch. 4. Eastman Eastar Bio® is a copolyester based on terephthalic acid and ethylene glycol. 5. Showa HIGH Polymer Bionolle® is a biodegradable polyester resin. To webs (rolls) are used to form bags. The paper web (55) forms the outer wall of the bags while the plastic web (56) forms the inner wall. The web (55) consists of Kraft paper only which provides the outer layer of the bags with a weight of 98 gm/m2 covered on one surface (which becomes the interior of the outer layer) with 15 to 50 gm/m2 of biodegradable polyester, or polyesters mixture film providing a vapour barrier, and tear resistance. The two webs are formed in known manner into a continuous flattened tube. The forming of webs into a continuous multi-layer tube which is then cut to length and the subsequent cutting, creasing and gluing of the end portions of each of the cut lengths so as to form bags are well known operations in paper bag manufacture and can be carried out on automatic machinery. Example 9: A milk powder bag is formed with an internal polyethylene pouch and an outer protective covering (bag) of a composite material of sandwich construction (Figure 6). -25- The outer bag has a pair of broad faces, ie; front and back faces, joined by side faces which are joined at top and bottom ends, which bag as a composite material made up from Kraft paper inner and outer layers and a polymeric internal layer. The outer and inner layer has a Kraft paper weight in the range from 20 - 90 gm per m2. In our example the outer Kraft paper weight is 40 gm per m2, and the inner Kraft paper weight is 90 gm per m2 (Figure 12). The Kraft paper provides shock-absorbing attributes. In addition, the paper is resistant to tear, and heat. The internal layer is conveniently provided as a polymer film, for instance a polyethylene/polypropylene film, between the layers of Kraft paper. The inner surface of the Kraft paper layers are coated with the adhesive and laminated to the polyethylene/polypropylene film layer. Alternatively, the adhesive may be coated on both sides of the polyethylene/polypropylene layer and laminated to the inner surface of the Kraft paper layers. In any case the polyethylene/polypropylene layer provides tear and puncture resistance, a gas barrier, and an odour barrier (to protect the product packaged from picking up off-odours). The film, or coating plastic "polyethylene/polypropylene" are used herein to describe a number of sealant materials, such as low density polyethylene, linear low density polyethylene, medium density polyethylene and high density polyethylene, and different grades of polypropylene. Three webs (rolls) are used to form the composite bag material. Paper webs (60 and 59) form the inner and outer wall of the composite bag material while the plastic web (61) forms the internal layer (Figure 12). The webs (60 and 59) consist of Kraft paper only which provides the inner and outer layer of the bags with a weight of 40 and 90 gm/m2 respectively. The internal layer (61) is 15 to 50 gm/m2 of biodegradable polyester, or polyesters mixture film providing a vapour barrier, and tear resistance. The three webs are formed in know manner into a continuous flattened tube. The forming of webs into a continuous multi-layer tube which is then cut to length and the subsequent cutting, creasing and gluing of the end portions of each of the cut lengths so as to form bags are well know operations in paper bag manufacture and can be carried out on automatic machinery. -26- The adhesive (gluing) layer (62) and layer (63) provides secure bonding of the film layer to the Kraft paper layer. The adhesive selection of choice is polyester-urethane, due to its heat and chemical resistance. This adhesive is applied to the film in solution, or to Kraft paper layer. The liquid carrier is driven off using hot air leaving a thin layer of the adhesive. The adhesive is then thermally bonded to the second layer. Other adhesives and other laminating processes are well known in the converting industry and may be useful for the production of the laminated material of the package of this invention. For example a "polymounting-process", as described in Example 5. Example 10: A milk powder bag is formed with an internal polyolefin polymer pouch and an outer protective covering (bag) of a composite material of sandwich construction (Figure 16). The outer bag has a pair of broad faces, ie; front and back faces, joined by the side faces which are joined at top and bottom ends, which bag as a composite materials made up from Kraft paper inner and outer layers and a biodegradable plastic internal layer. The outer and inner layer has a Kraft paper weight in the range from 20 - 90 gm per m2. In our example the outer Kraft paper weight is 40 gm per m2, and the inner Kraft paper weight is 90 gm per m2. The Kraft paper provides shock-absorbing attributes. In addition, the paper is resistant to tear, and heat. The internal layer is conveniently provided as a polymer film, for instance a Cargill Dow ExoPLA® a polylactic acid film, or DuPont Biomax® hydro/biodegradable polyester (proprietary aliphatic polyesters) between the layers of Kraft paper. The inner surface of the Kraft paper layer is coated with the adhesive and laminated to the biodegradable polyester film layer. Alternatively, the adhesive may be coated on the biodegradable polyester film layer and laminated to the inner surfaces of the Kraft paper layers (Figure 12). In any case the biodegradable polyester layer provides puncture and tear resistance, a gas barrier, and an odour barrier (to protect the product packaged from picking up off-odours). It is also the layer and material used to form hermetic seals through thermal welding (or otherwise) since it forms the inner surface for the bag. The film, or coating plastic "biodegradable polymers" are used herein to describe -27- a number of sealant materials, as in Example 8. Three webs (rolls) are used to form the composite bag material. Paper webs (60 and 59) form the inner and outer wall of the composite bag material while the plastic web (61) forms the internal layer. The webs (60 and 59) consists of Kraft paper only which provides the inner and outer layer of the bags with a weight of 40 and 70 gm/m2 respectively. The internal layer (61) is 15 to 50 gm/m2 of biodegradable polyester, or polyesters mixture film providing a vapour barrier, and tear resistance. The three webs are formed in known manner into a continuous flattened tube. The forming of webs into a continuous multi-layer tube which is then cut to length and the subsequent cutting, creasing and gluing of the end portions of each of the cut lengths so as to form bags are well known operations in paper bag manufacture and can be carried out on automatic machinery. ADVANTAGES Tests on sample bags having a single layer outer formed from a laminate having a substrate if 125 gsm Kraft paper and an outer layer of 15 gsm polymer film (comprising a mixture of polyethylene and polypropylene) and an inner 65 micron HDPE polyethylene pouch confirm that the bags exhibit toughness and tear resistance when both wet and dry and have good vapour barrier properties. The sample bags satisfy the drop tests mentioned above even thought they have only a single outer laminate layer. The sample bags were tested and survived : (a) the industry standard "vertical drop test" for milk powder bags were the filled and sealed bag (at ambient temperature and relative humidity conditions) was repeatedly dropped from a height of 1.2 metres onto its butt without damage; and (b) the "side drop test" which requires the sealed bags to be dropped, at ambient temperature and relative humidity conditions, such that the bag must survive a total of two drops - one drop test on each side, and preferably survive at least a total of four side drops (with two drops per side), from a height of 1.2 metres without failure of the outer ply or the sealed ends, and with the product remaining in its pouch intact at all times. By using a single layers of composite material for the outer bag, it is possible to -28 - produce an improved bag at a reduced cost compared to the multiple layer paper bags for example paper bags having two, three or four layers of Kraft paper surrounding an inner plastics pouch. By making the composite material from a combination of paper and polymer film layer so that the two are bonded together, the composite material can provide a heat sealable surface, increased tear and scuff resistance, a laminating medium, and an excellent barrier against grease, oil, gases, moisture and other environment. The composite material can also be recycled by separating the polymer from the paper layer. The preferred polyester film layer (example 4) and the preferred polyethylene/polypropylene film layer (Examples 2 and 3) offer a wide range of desirable features including: • Excellent adhesion to the substrate • Low sealing temperature • Good draw down and low neck-in • Excellent chill-roll release • Pinhole-free coatings • Adhesion to unprimed foil • Good grease resistance • Toughness • Excellent printing characteristics • Good seal strength • Low water vapour transmission rates. VARIATIONS: In some cases the polymer film may provide too much of a barrier against gasses, particularly where the material contained within the pouch requires some gas interchange with the atmosphere. In which case it is preferably that the polymer film is provided with minute gas permeable apertures prior to or after laminating to the payer layer. For example the material of the examples described above, is particularly suited to an outer covering for the packaging of full fat milk powder, but preferably should be modified before use in the construction of an outer covering for a skim milk powder bag. In some cases it may be preferably to reduced either the thickness of the paper layer, or the thickness of the polymer film layer, or to add more than one polymer film layer to the composite material (either on the same side of the paper, or on both sides of the paper). As mentioned above, the easy opening feature may involve a tear strip or the like at or adjacent to the top of the bag, or may involve one along the longitudinal seam, or elsewhere on the bag, or may be formed as part of the base of the bag. Preferably the top of the bag is formed with a fold over flap, which can be sealed by an appropriate adhesive after packing and sealing of the inner pouch. However, any convenient form of top can be provided, and in some cases it may be preferable to seal the outer bag with a separate outer top or covering (particularly as the outer bag is formed from a single layer of composite material, and hence the flap if it is included needs to be part of the bag which is longer than the pouch associated with the bag, and this may involve some relative displacement of the pouch material from the outer covering material during manufacture of the bag). Any convenient means of sealing the top of the bag can be used after the bag has been filled. It will be noted that the bag is so designed that the inner pouch can be heat sealed, by the application of heat bars to the outside of the bag, and it is thus preferable that the polymer film material bonded to the paper of the outer covering has a higher melting point or higher sealing point than the material of the pouch. During filling, heat sealing of the pouch should be effected, in such a way that the pouch is not in any way bonded to the outer covering of the bag as a result of the heat sealing process. Note however, that the inner pouch will be tacked to the outer covering of the bag in one or two places using spots of hot melt adhesive or the like, to facilitate location of the pouch during the various following operations, and to assist the pouch in being held in a stable position during filling of the bag. These spots of adhesive are designed to enable the outer covering to be readily pulled away from the inner pouch without damage to the inner pouch, when the product has reached its destination. -30- Finally, it will be appreciated that various alternations or modifications maybe made the foregoing without departing from the spirit or scope of this invention. -31 - </div>

Claims

CLAIMS:

1. A bag having an inner plastics pouch capable of being heat sealed after insertion of powder or granules, and a removable outer protective covering, wherein the removable outer protective covering consists of a single layer of composite material laminate consisting of at least one layer of paper, and at least one layer of at least one polymer film bonded to the paper layer(s).

2. A bag of claim 1 wherein there is one layer only of the polymer film.

3. A bag of claim 1 or 2 wherein the paper layer or layers is or totals in the range of from 90 gsm to 200 gsm and the polymer layer(s) is or totals to a thickness in the range 12 to 75 microns. INTELLECTUAL PROPERTY OFmnp OF M.Z 3 1 MAY 200*1 RECEIVED