WO2015147719A1

WO2015147719A1 - Closure of paper bags

Info

Publication number: WO2015147719A1
Application number: PCT/SE2015/000018
Authority: WO
Inventors: Lars Smedlund; Theodor SKOGLUND
Original assignee: Miljösystem I Göteborg Kb
Priority date: 2014-03-28
Filing date: 2015-03-26
Publication date: 2015-10-01
Also published as: SE1400171A1; SE541195C2

Abstract

The present invention relates to a Refuse bag made of paper comprising a front, wider and rear wider wall (3,4) having mutual substantially the same width, and two side walls(2) to be fold in between said front and rear walls (3,4), whereby the rear wall (4) is drawn up to a level above the front wider wall (3), whereby a folding line (9) is arranged across the rear side wall (4) substantially in level with the upper edge of the front side wall (3) to the formation of a lid (10) to be able to provide for a simple folding around of this lid (10) to said front side wall (3), that the side walls (2) further are drawn up to a level over the wider front wall (3) to reach up to 25 to 65% of the level of the wider rear wall (4), whereby said folding line (9) moreover is present on the side walls (2) in level with the upper edge of the front wall (3), and that an adhesive layer (5) is distributed over at least two surfaces with at least one non-adhesive slit (11) between these surfaces on either the lid (10) or on the wider front wall (3), whereby the adhesive layer (5) reaches substantially at least from the upper edge of the lid (10) until the upper edge of the drawn up side walls (2) or substantially at least from the upper edge of the wider front wall (3) to a line corresponding a folded lid (10) to the wider front wall (3), whereby the slit (11) forms an air valve comprising 25 to 65% of the width of the bag to allow release of air after a closure.

Description

TITLE

CLOSURE OF PAPER BAGS

DESCRIPTION

Technical field

The present invention relates to a means for closing paper bags, which can be sorted by means of an optical sorting system used in refuse suction devices, in multi vessel systems or in compartment systems, in particular it relates to sorting of paper bags comprising food offal. Background of the invention

With regard to the environment the fractionation of refuse has become more and more essential. Thus most households in Scandinavia separate food offal, glass, paper, metal products and polymer packages, as well as more toxic products such as chemicals (solvents, paints, a.o.), batteries, and leftover drugs into different fractions for reuse or recovery. The reasons are on one side thus reuse or recovery of materials, or energy on the other side that the costs for treatment have risen considerably.

In many places the households themselves have to transport their different fractions to recovery stations. In other places different fractions are collected separately at the house/estate. Residual offal and food offal are almost always collected at the house. Also the working areas restaurants, dining rooms, and other activities can have sorting of food offal and are included in the present invention.

A rational way to collect different, out-sorted fractions is to collect them in a common refuse vessel, and then to separate the different fractions at a central sorting plant, whereby the fractions are packed in polymer bags having different colours, which are separated by means of an optical separation technology using an optical reader which recognizes the different colours and controls the separation to different collecting vessels. Optical separation of food offal, which shall be used for compost or biogas production creates, however, a problem as one today requires to to use polymer bags even for the food offal. This is due to the fact that the bags in the collection chain are subject to strong outer impact and that polymer bags up til now have been the only alternative, which have been able to fulfil the requirements of below. The principle of optical sorting is that different materials and offal fractions are sorted at the source in differently coloured bags. All bags are part of the same vessel, and after collection, and deloading they are separated in a central sorting plant. The sorting is carried out in such a way that the bags arriving on a transport belt are optically identified and a selected bag is pushed away from the belt to a respective container or the similar. Everything at the detection which is not recognized as a predetermined identifiable colour bag is interpreted as rest offal. The number of fractions being sorted out is from two to seven.

Today optical sorting systems are present at about 30 plants, primarily in Scandinavia, and the number rises steadily. It is a collecting system having several advantages, in particular for reducing transports, and as one can use existing equipment at collection. However, the system has been struggling with problems what concerns food offal all since the first plant in 1991. This, as the system cannot be combined with paper bags used for the food offal but requires polymer bags as carriers, which provides negative effects.

Problem

From studies carried out by Avfall Sverige (primarily B2009:l, U2010:10, and U2011:04) it is evident when one compares polymer bags with paper bags at the collection of household food offal that

• Paper bags give quite 4 times, less faults sorting by the households that polymer bags give (96% cleanness compared to 83%). Higher cleanness gives lower costs at the pre-preparation and in that the putrefaction process as well, as it gives cleaner bio manure.

• Paper gives 50% larger amount of out sorted food offal per connected household and year, as paper has an inherent pedagogics (180 kg compared to 122 kg).

• Paper gives in practise 39% higher recovery of methane per connected household.

• Paper gives 27% reduction of weight (mostly water evaporation) from kitchen to treatment plant due to the fact that paper allows water evaporation; polymer bags give 2% reduction of weight.

• In normal cases one need not to separate the paper from the food offal at the pre-treatment.

• Polymer bags are, on the other hand more simple to close and will not leak as simply as the paper.

When composting is used as a method of treatment, the handling problems are less evident, but in the more sensitive putrefaction process more considerable problems arise: 1. At the handling of food offal bags made of polymer at the receiving plant larger or minor costs and additional works at the pre-treatment arise. There is a loss of food offal simultaneously as polymer residues can pass over to the food offal fraction. The loss can arise at the identification and the sorting out, bag opening, and sieving or separation. The problem has become less concurrently with the fact that more plants have been built, but is still considerable. Some communes, which wish to replace composting with putrefaction, state that they is such cases have to replace polymer bags with paper bags.

2. Food offal is a biologically living material having a high content of water. When it becomes enclosed in a tight environment, which hinders ventilation to the surrounding air, an undesired decomposition will rapidly take place, a forced putrefaction process, which starts already in the kitchen and refuse rooms. A wet material having a low pH and bad odour will be obtained. The material will also loose a certain amount of its inherent energy (according to tests made, about 25%; ref. Rapport Torrkonservering, matavfall, Part Study 3, Avfall Sverige 2009).

3. As polymers are not biologically and easily degradable, and as polymers are also used for other offal, the polymers give a wrong intuitive message to the users, which is the primary reason to the fact that polymer bags give a clearly worse sorting result at the households than the paper bags do. For example there is a system where one uses black polymer bags for food offal which is the same colour as that of the transporting belt. Here this is not a question "real" identification of different colours, but all that can be identified as non-black are pushed away from the belt, whereby the black bags continues to the end of the belt. Here there is a problem situation in that all unidentified material follows the food offal, which is a fairly large part. There is a total loss of food offal from deloading to putrefaction treatment of 40 to 60% of the food offal. There is further a problem to get the material out of the bags in a good way.

Since 2001 another example of optical sorting into two fractions has been carried out, today with green and white bags. One experiences a problem in that the cleanness of the green bags (food offal) is too bad, and that a great part of the green bags land up in the residual fraction. There is also too much of polymers in the food offal fraction, which influences the final compost negatively.

There are further 4 plants in the Nordic countries that have closed their optical sorting, primarily depending on the problem with food offal in combination with polymer bags. The conclusion is that it would be of great advantage if one can use paper bags at the collection of the food offal within the optical system.

Demand concerning function of the bag and its closure

The optical reader which controls the separation from a transport belt using differently coloured bags has today been developed in such a way that also dirty paper bags having non-conform colour thereon can be identified, which could not be made previously with an accuracy sufficiently high enough. This means that it is now possible to use paper bags under the condition that they fulfils all other demands which are needed within the optical sorting:

1. The bag shall keep its content intact without opening up or break, all the handling way from the household up to the push away at the belt of the sorting plant. Further leakage of food offal from the bag shall be minimized.

2. The bag and its closure function shall be user-friendly to the household.

3. The bag or closure means shall be economically feasible.

4. The bag shall not add any disturbing material to the treatment or to biomanure, and shall fulfil the demands for decomposition according to SPC 120 Biogodsel and 150 Kompost.

5. The bag shall not break at emptying and compression in the refuse lorry.

Comments to item 5: The emptying of vessels into a refuse lorry means that the vessels are lifted and the bags are emptied out and fall about 2 metres. Then a compression is carried out via pushing wall which presses the material forward in the lorry. A bag which contains air can within the run of some 1/10 of a second be compressed with a large force and is brought to break. Simultaneously as the air from the bag shall be able evacuate rapidly, leakage of food offal from the bag shall be minimized. In the same way there a first compression takes place, often when the contents of an offal vessel is turned upside down into the refuse lorry, when a heavy load hits previously loadad offal bags.

Polymer bags which have been knitted together will in most cases have an opening large enough at the knot so that the air manage to evacuate during the compression without having the polymer bag explode, furthermore the polymer is elastic and yield to a certain extent.

Besides the use within optical sorting, the present invention also solves problems connected to other collection systems using multi vessel systems (food offal being collected in separate vessels) and multi compartment systems (several compartments for different fractions present in the same vessel). Today's problem when using paper bags for food offal is that the bags will open easily when they are dropped down into the vessel or are rolled away to a refuse lorry. In that way food offal will leak out into the vessel and increase the need for cleansing of the vessel against insect infestation and odour.

The central sorting process from the deloOading of the lorry to the sorting out of the bag can be divided into three steps:

• Emptying into a receiving hopper provided with a transport to a belt

• Transport on the belt to an optical identification

• Sorting out/pushing away of the bag Previous tests using paper

There have been previous attempts to replace polymer bags with paper. These have not lead up to a tenable solution. The following obstacles have been brought forward:

• The closure ability of the paper bag: one has not found any solution which is durable enough simultaneously as it economically feasible and user-friendly enough. Tape as closure cannot be used as there are still no biodegradable alternative, and in that tape causes mechanical problems in the putrefaction process. Other alternatives are often too costly at a serial production, or too difficult to understand and to handle by the households. Attempts made with bags of biopolymer, "maize bags", fail primarily in that they causes large problems at the stirring in the putrefaction reactors, as long tough bands are created which are whirled into the rotating mixing mechanism.

• Detection has previously been a hinder as paper changes it colour when it becomes wet.

Today, the leading company in optical sorting that this has been solved, so now one may also sort out paper bags with a high accuracy. The advantages using paper as a carrier are that the bag is biodegradable and can follow its contents in the wole handling chain. Further, the paper bag allows the food offal to "breath", which gives a slower decomposition before the material shall be treated, less odour and weight reduction in the form of water evaporation. This will also provide for a higher pH in the treatment plant. There is a clear pedagogic profit using paper instead of polymer, as paper intuitively is experienced as degradable and that the material harmonizes with the food offal. Paper is a "messenger". Further paper contributes with carbon at the treatment and bio manure/compost. In order to be able to stand the hard handling in an optical collection system a paper bag need to be strong and resistant both in closure as in the material itself.

WO 9640561 describes a bag for composting of vegetable material, which bag consists of a laminate structure comprising a top layer of paper, a non-toxic laminate comprising protein based adhesive mixed with a hardener, which makes the adhesive insoluble in water, a reinforced thread enclosed into the laminate, as well as a bottom fold comprising a paper. According to one embodiment this bag may comprise an adhesive flap for the closure of the bag. Different from the present invention there is nothing in the description or claims of WO 9640561 pointing at or hinting at a valve function. Rather the contrary, figures 2, 3 and 5 show a complete closing of the opening end of the bag, which is completely contrary to the object of the present invention, which shall provide an evacuation of the air enclosed in the bag. The embodiment of Fig. 6 of WO 9640561 is completely contrary against the object of the present invention as that embodiment only shows a folding over of the upper parts of the parts of the bag, i.e. no real closing but a closing that can open in a very simple way and thereby release the contents.

Further the bag according to WO 9640561 shall be hard to compost according to the description of WO 9640561, page 4, first paragraph.

US 6214392 describes a polymer bag for the enclosing of a product, whereby the bag is provided with a complex closure comprising a first valve hole and a second closing provided with a second valve hole, which are intended to release air in a controlled manner at the stacking of the products/bags through a zigzag path way and which valve holes also admits a return of air into the bag when an outer pressure ends in order to provide for an uniform shape for presentation and sale. The purpose is that the bag shall allow a controlled evacuation of air during stacking maintaining shape in order to allow exhibition for sale.

Different from the present invention the complex closing shown in US 6214392 only a very slow evacuation of air and the solution can in no way allow a rapid evacuation required in the present invention in order not to let the bag burst at a rapid compression which can exist at the handling in a refuse system, such as a central refuse chute or at lorry emptying of refuse vessels.

The bag according to US 6214392 cannot be rapidly evacuated with regard to enclosed air. GB 2447108 describes a bag comprising a bottom part, to opposite wide sides, and two opposite short sides. The walls of the bag consists typically of a laminate of paper surrounded by a paper based layer which forms the outer side, as well as compostable polymer material, such as polylactic acid or cellophane. The bag is primarily intended to be used at the sale of products to become filled therein. In an embodiment shown (Fig. 1) the bag is closed (sealed). This means that there is no possibility for evacuation of air present therein. The object of the closing is to store e.g., food stuffs, food stuffs that normally has a "best-before-date" with regard to consumption.

The bag according to GB 2447108 is thus not intended for a rapid evacuation or even a slow evacuation of air enclosed therein.

It has also turned out that bags made of polymer foil cannot stand the loadings in different collection systems but break, often through an outer scratching. The overall object of the present invention, within primarily optical sorting of food offal, is to offer a paper bag which can replace the polymer bag of today, as a carrier for food offal from households.

The present invention relates to the substantiation of food offal bags made of paper primarily at optical detection, but also commune systems using separate vessels and multi compartment vessels are included. The present invention reduces the amount of loss of food offal in the vessel and provides thereby less problem with regard to vessel washing, odour and insects.

Summary of the present invention

The present invention thus relates to a method and a package to facilitate sorting of paper bags containing food offal by means of optical detection.

The basic main object is thereby that a filled closed paper bag shall withstand a compression without breaking and without letting any content out present in the bag. Description of the present invention

In particular the invention relates to a method for closing of a food offal bag made of paper in an efficient and hygienic way to, on one side facilitate optical sorting, and/or on the other side create hygienic storage conditions. Detailed description of the present invention

The present invention will now be described with reference to a series of embodiments showed i.a., in attached drawing, wherein

FIG. 1 shows a perspective view of an embodiment of a paper bag according to the present invention;

FIG. 2 shows a front view of the embodiment of a paper bag according to FIG. 1;

FIG. 3 shows a front view of an alternative embodiment of a paper bag according to the invention; and

FIG. 4 shows a front view of a further embodiment of a paper bag according to the invention.

1 denotes generally a paper bag with a folded wedge (FIG. 1) comprising a front side wall 3 and a rear side wall 4, which are connected by means of two narrower side walls 2. The narrower side walls are inwardly foldable behind the front and rear wider side walls 3, 4, and attached to the wider side walls 3,4 at the bottom 21 of the paper bag 1. The narrower side walls 2are provided with folding lines 7 in connection to the wider side walls 3, 4 to facilitate and infolding of the narrower sides 2 and provided with a folding line 8 in their respective longitudinal centre to allow a folding to a flat paper bag 1.

The bottom of the paper bag 1 may either be a folded bottom where the wall 3 is folded to overlap the wall 4 and is glued to this to the formation of a pointed bottom or may formed by foldings to form a flat bottom.

The rear wall 4 is drawn up to a level above the wider wall 3, whereby a folding line 9 is arranged across the rear wall 4in level with the upper edge of the front wall 3 to for a lid 10 of the drawn up rear wall 4 to facilitate a simple folding over by this lid 10.

The side walls 2 are further drawn up to a level over the front wider wall 3 to reach up to 25 to 65% of the level of the rear wall 4. The previously mentioned folding line 9 is present on the side walls 2 in the level of the upper edge of the front wall, as well. The object is herewith that the drawn up side walls 2 shall, at a folding over the front wall 3, reach down over this front wall and become locked over this by means of an adhesive layer of the lid 10, either direct or indirectly.

The lid 10 can be provided with an adhesive layer of a pressure sensitive, biodegradable glueing polymer 5, such as Duro-Tak 8673E, provided with a protecting foil 11 or being laminated with a heat sensitive biodegradable polymer 5, such as a polymer of lactic acid, polylactic acid or polylactide (polylactic acid or polylactide). The polymer in the latter case has a melting point of 150 to 180°C and a glass transition temperature of 650 to 65°C, and a molecular weight of 128 to 152 kDa. The melting temperature and the glass transition temperature depend on which mixture of D- and L-form of lactic acid that are used at the polymerization. Other ways of modifying polylactic acid is to bind xylane for formation of side chains (more exactly a way to make xylane formable to a foil).

As evident from FIG. 1 the adhesive layer 5 of the lid part 10 distributed over at least two surfaces with at least one non-adhesive provided slit 11 between these surfaces. The adhesive layer 5 extends substantially from the level of the upper edge of the lid 10 up to the upper edge of the side walls 2. It is preferred that the adhesive layer 5 reaches substantially to the folding line 9 on the rear wider wall 4, i.e., from substantially at east to the upper edge of the rear wall 4. The slit 11 forms an air valve comprising 25 to 65%, preferably 25 to 50%, more preferably 50 to 65% of the width of the bag to allow evacuation of air after closure. By means of the level of the side walls 2 above the front wall 3 these will also to become folded down over the front wall 3 at a closure, and by means of the adhesive surfaces 5 to become blocked to the wall 3. Thereby the side walls 2 are hindered from become pressed outwardly at a compression. Tests carried out using only a lid forming rear wall have shown that at a compression the side walls are pressed outwardly and large amounts of the content thereby will slip out during transport and sorting performance. In FIG. 3 an embodiment is shown wherein adhesive layers 5 are arranged substantially from the upper edge of the rear wall until the upper edge of the folding line 9, which means that at a folding over of the lid 10 the adhesive surface will fasten against the rear surface of the side wall 2, as well as against the forward surface of the side wall 2 which further increases the resistance against a splitting of the side walls 2. This means an increased risk minimization for the release of material from the bag 1.

In FIG. 4 an alternative embodiment is shown wherein the adhesive layer 5 has been arranged onto the front wall 3 and whereby the adhesive layer 5 has been divided into three parts 5a, 5b, and 5c to arrange for two slits 11 through which air can pass at a compression of the bag 1.

When the bag 1 is to be closed the closing flap 4, the lid 10, is folded around the opening having the laminated side turned inwardly. When a heat sensitive adhesive is used, PTC thermistor tongs having a working temperature of about 160°C is introduced on each side over the closing flap 4, and is squeezed, whereby the laminate melts and binds to the bag 1 on each side of the opening. Example

Example 1

70 bags according to the present invention filled with food offal were tested in a central refuse suction plant. No bag burst but all bags were intact and their contents could be completely recovered for biogas production.

In the same plant polymer bags were tested even those filled with food offal, whereby it turned out that 50% of the bags burst at the handling in the central refuse suction plant. Example 2

At a test using bags according to the present invention having been collected using refuse vessel collection 1.5% of the bags were damaged.

Example 3

At the collection of paper bags where closure had been done along the whole folding edge by means of a double adhesive tape and the collection had been carried out in a magnum vessel 20% of the bags had burst due to the pressure arising in the bag.

PTC thermistor (Positive Temperature Coefficient) consists of a doped polycrystalline ceram based on barium titanate, which gives dynamic properties or self-regulating properties, which means a high resistance at higher temperatures and a low resistance at low temperatures. The PTC element is of semi-conductor type. Usually an aluminium case is used to conduct away heat from the PTC thermistor/element. The energy of the PTC resistor is often provided with 230V AC. The PTC element can be applied on each side of the closing flap or only be present on one side, in particular if the closing flap is pre-attached to the bag 1, such as shown in FIG. 2. In this case the tongs comprising the PTC element has a holding up tool made of silicon rubber.

The PTC element itself is preferably consisting of two part element placed at a distance from each other in order thereby to create a slit in the closure, i.e., a non-continuous closure over the total width of the paper bag. This slit allows air to pass out of the bag 1 at the compression, such as after loading in a refuse lorry.

Herein the bag 1 has been shown as a bag having wedged sides but can likewise consist of a bag of so called canister-type. In particular, larger bags/sacks are often of canister-type. The bottom of the bag can be either a folded bottom without extension or can be a rectangular bottom which facilitates the placing of the bag on a surface.

In a paper bag the risk is great that , when closing the same so much air is being enclosed that the bag bursts at a compression. The invention solves this problem by the fact that the closure leaves an evacuation way large enough in the middle of the closure flap for the air as the closure is non- continuous simultaneously as the construction still hinders the food offal to leak out. Further the construction provides a sufficient durability against the opening of the bag before transport and sorting.

In the embodiment above the bag opening is closed by means of a laminated adhesive which is adhered to the outer side of the paper bag.

The bag 1 is suitably provided with a marking line showing the filling level whch is common at the paper bags commonly used for food offal collection.

In a further embodiment the inside of the bag can be provided with a barrier layer to reduce permeability of fat and moisture, partly to increase the strength of the bag, partly to improve the optical reading at the sorting by reducing large colour changes of the paper surface. Such a barrier may be made of a Bim Kemi fat and water barrier or a Bim Kemi fat barrier and which are applied as a liquid by spraying or application.

Claims

1. Refuse bag made of paper comprising a front, wider and rear wider wall (3,4) having mutual substantially the same width, and two side walls(2) to be fold in between said front and rear walls (3,4), characterized in

that the rear wall (4) is drawn up to a level above the front wider wall (3), whereby a folding line (9) is arranged across the rear side wall (4) substantially in level with the upper edge of the front side wall (3) to the formation of a lid (10) to be able to provide for a simple folding around of this lid (10) to said front side wall (3),

that the side walls (2) further are drawn up to a level over the wider front wall (3) to reach up to 25 to 65% of the level of the wider rear wall (4), whereby said folding line (9) moreover is present on the side walls (2) in level with the upper edge of the front wall (3), and that an adhesive layer (5) is distributed over at least two surfaces with at least one non- adhesive slit (11) between these surfaces on either the lid (10) or on the wider front wall (3), whereby the adhesive layer (5) reaches substantially at least from the upper edge of the lid (10) until the upper edge of the drawn up side walls (2) or substantially at least from the upper edge of the wider front wall (3) to a line corresponding a folded lid (10) to the wider front wall (3), whereby the slit (11) forms an air valve comprising 25 to 65% of the width of the bag to allow release of air after a closure.

2. Refuse bag according to claim 1, wherein the adhesive layer (5) extends substantially to the folding line (9) on the wider rear wall (4).

3. Refuse bag according to claims 1-2, wherein there are at least two slits (11) present between the parts of the adhesive layer (5).

4. Refuse bag according to claim 1, wherein the lid (10) is provided with a laminate (5)

consisting of a biodegradable and by heat meltable polymer.