WO2023195850A1

WO2023195850A1 - Method of diassembling a mattress

Info

Publication number: WO2023195850A1
Application number: PCT/NL2023/050179
Authority: WO
Inventors: Peter BOERHOF; Stijn Gerard VRERIKS
Original assignee: Koninklijke Auping B.V.
Priority date: 2022-04-08
Filing date: 2023-04-06
Publication date: 2023-10-12
Also published as: NL2031538B1

Abstract

The invention pertains to a method for disassembling a mattress (1) comprising as constituting parts a) a base layer (2), b) an in essence rectangular assembly of contiguous pocketed springs (8) provided on the base layer, c) a resilient top layer (10) to cover the assembly of pocketed springs (8), and d) optionally resilient side walls (3-6) at opposing lateral sides of the assembly of pocketed springs (8), wherein the said constituting parts a) to c) and the optional part d) are interconnected with a hot melt adhesive that has a melting temperature Tm, the method comprising putting the said mattress (1) in a convection oven wherein a flow of air is created, wherein the air has a temperature above Tm and below Tm + 50°C, heating the mattress (1) until the hot melt adhesive acquires a temperature above Tm, releasing the mattress (1) from the oven and taking away the top layer (10), the base layer (2) and the optional side walls (3-6), from the assembly of pocketed springs (8). (Fig. 4)

Description

METHOD OF DIASSEMBLING A MATTRESS

FIELD OF THE INVENTION

The invention pertains to the disassembling of a mattress, in particular the disassembling of a so called pocketed spring mattress. Such a mattress consists of various very different materials, typically the metal springs and various types of textile and foams, and due to the difficulty of disassembly, is often simply burned to recover the relatively expensive metal of the springs. Still, disassembling is preferred since this way various parts can be reused, either in a new mattress or as raw material for creating new objects.

BACKGROUND OF THE INVENTION

Sleep plays a vital role in good health and well-being throughout life of any person. Getting enough quality sleep at the right times can help protect the mental health, physical health, quality of life, and safety of a person. It has been known for a long time that during sleep, the body is working to support healthy brain function and maintain physical health. The damage from sleep deficiency can occur in an instant (such as a car crash), or it can harm over time. For example, ongoing sleep deficiency can raise the risk for some chronic health problems. It also can affect how well one thinks, reacts, works, learns, and gets along with others.

That is why the quality of a mattress is key for attaining high quality sleep. In practice therefore, a mattress is replaced when the quality starts to decrease. Commonly a lifespan of about 10 years is accepted for a mattress, after which the mattress is replaced for a new one. However, in many cases only parts of the mattress are no longer up to the required standard, whereas other parts, such as for example the pocketed springs, still meet these standards. However, recycling the old mattress by re-using the parts that are still okay is a common problem in the art, since it is very cumbersome to take a mattress apart in its constituting parts. Because mattresses are expensive to recycle, most mattresses are simply burned and remaining metal is used as scrap for the metal industry.

JP6032957, filed on 12-06-2012 and assigned to Simmons Corporation, discloses a method to efficiently sort and disassembling a pocketed spring mattress. For this a disassembling apparatus is disclosed that includes an accommodation space for the mattress and a heating means which sets the accommodation space to an atmospheric temperature capable of melting the polymer materials of the mattress. The apparatus also comprises a storage space which stores the molten material, flown down below the accommodation space. The springs remain and can be reused. Disadvantage of this method is that all polymer material gets mixed and is low quality. This can be prevented by making all materials of the same polymer, but this severely restricts the freedom in manufacturing the mattress. Also, relatively high temperatures are needed to actually melt the polymer materials, which high temperature treatment means that the coil springs cannot simply be re-used in a mattress without any further treatment. Therefore, the metal in most cases is used as a raw material.

JP6832552, filed on 27-12-2019 and assigned to Asuka Kohsan Co Ltd, discloses a method and device similar as that known from JP6032957. The device also aims at releasing the polymer material from the pocketed spring mattress without any effort to separate the useful substances beforehand. Likewise, heat is used to melt the polymer material, remove the molten material form the springs and re-using the metal of the springs. This method however suffers form the same disadvantages as mentioned here above.

W02020/025551 , filed on 29-07-2019, assigned to DSM IP Assets BV, discloses a method that can be used for recycling a mattress wherein the various parts are interconnected using a so-called hot melt adhesive that transfers from a solid adhesive into a non-adhesive liquid when heated. In the method, the adhesive is locally heated around the worn part, whereafter this part is grasped and pulled out of the assembly. Although this method is very adequate for refurbishing worn mattresses, it is not very suitable for completely disassembling mattresses after their actual end-of-life has been reached. The process of removing the parts one by one after local heating of the adhesive is too cumbersome to be economically viable. OBJECT OF THE INVENTION

It is an object of the invention to provide an alternative method for disassembling a mattress, in particular a pocketed spring mattress, which method does not have the disadvantages of any of the methods as identified here above.

SUMMARY OF THE INVENTION

In order to meet the object of the invention, a method for for disassembling a mattress has been devised, wherein the mattress comprises as constituting parts a base layer, an in essence rectangular assembly of contiguous pocketed springs provided on the base layer, a resilient top layer to cover the assembly of pocketed springs, and optionally resilient side walls at opposing lateral sides of the assembly of pocketed springs (optionally two pairs of two side wall, thus forming a rectangular enclosure for the assembly of contiguous pocketed springs), wherein the said constituting parts, including the optional side walls, are interconnected (thus parts a, b, c and the optional parts d forming one unit) with a hot melt adhesive that has a melting temperature Tm, wherein the method comprises putting the said mattress in a convection oven wherein a flow of air is created, wherein the air has a temperature above Tm and below Tm + 50°C, heating the mattress until the hot melt adhesive acquires a temperature above Tm, releasing the mattrass from the oven and taking away the top layer, the base layer and the optional side walls (not necessarily in that order), from the assembly of pocketed springs.

Thus, the invention starts from a mattress (and is restricted to the recycling of such a mattress) of a particular constitution, viz. a mattress wherein the various parts are interconnected using a hot melt adhesive. Such a mattress is known from W02020/025551 . However, as explicitly taught in the ‘551 application, in order to disassemble the mattress, local heating must be applied to melt the adhesive, in particular via the use of microwaves, heat radiation or light radiation. The reason for this is that conventional bulk heating of the mattress in an oven is commonly thought to be very slow because of the inherent thermal insulating properties of a mattress. This means that either the retention time is very long in a conventional oven, or the temperature should be set that high that all polymer material in the mattress would melt. In any case, prolonged heating at high temperatures would mean, even if the temperature is set such that the polymer materials (apart form the adhesive) would not actually melt, they would at least run the risk of deterioration, or soften such that for example the pockets elongate under the tension of the springs, making the pockets (i.e. the most expensive and most durable part of the mattress) virtually unsuitable for reuse. Surprisingly however, against the teaching of W02020/025551 , it was found that heating the complete mattress in oven is a technically viable method for disassembling the mattress as long as few pre-requisites are met: Firstly, the oven has to be a convection oven wherein a flow of air is created. In a convection oven, heat is distributed actively by the forced airflow and thus if needed, heat can be directed at particular sites of the object to be heated. The fact that the hot melt adhesive for interconnecting the base and top layer as well as the side walls to the pocketed spring assembly is mainly found around the outer circumference of the mass of the mattress is very helpful in this respect: the inventors recognised there is no inherent need to heat the core of the mattress to a temperature above Tm. A second prerequisite is that the air has to have a temperature above Tm (of course, only this way the hot melt adhesive can be melted), but importantly has to stay below Tm + 50°C. This way, it can be prevented that the other polymer materials (typically polyesters and polyamides which have a melting point above 230°C) are melted or even deteriorated. This can be understood by recognising that the typical melting point of (non-reactive) hot melt adhesives is below 180°C (typically between 90 and 170°C, such as between 100 and 160°C, or even between 120 and 150°C; see W02020/025551 , in particular Example 1 , including Table 1 , in combination with figure 1 of that patent application where it is explained what a hot melt adhesive is). Thirdly, it is essential that after the mattress is heated such that the hot melt adhesive acquires a temperature above Tm, the mattress is released from the oven to take away the top layer, side walls, and base layer from the assembly of pocketed springs. To be able and take away these parts outside of the oven greatly simplifies the method. Here, the fact that the mattress inherently has good insulating properties is an essential advantage: the mattress only very slowly cools down after being released from the oven, in particular the sites inside of the mattress where the melted hot melt adhesive is present. It was found that not only is the method relatively simple and needs in fact only conventional process apparatus, but also the pocketed springs remain in very good quality. Hardly any elongation, if at all, is seen as a result of the heating of the mattress which means that these pocketed springs can be re-used as they are released from the mattress.

In case the side-walls are not optional, the method of the invention is thus for disassembling a mattress comprising as constituting parts a base layer, an in essence rectangular assembly of contiguous pocketed springs provided on the base layer, a resilient top layer to cover the assembly of pocketed springs, and resilient side walls at opposing lateral sides of the assembly of pocketed springs, wherein the said constituting parts are interconnected with a hot melt adhesive that has a melting temperature Tm, wherein the method comprises putting the said mattress in a convection oven wherein a flow of air is created, wherein the air has a temperature above Tm and below Tm + 50°C, heating the mattress until the hot melt adhesive acquires a temperature above Tm, releasing the mattrass from the oven and taking away the top layer, the base layer and the side walls (not necessarily in that order), from the assembly of pocketed springs.

It is noted that a typical mattress comprises a ticking (textile cover) for comfort and hygiene. If so, such a ticking has to be removed before applying the method of the present invention. Most tickings nowadays have a zipper for easy removal. If not, they can be cut from the mattress.

DEFINITIONS

A convection oven is an apparatus having an internal space for accommodating an object to be heated, means to heat the air in that space and means to actively create an airflow therein.

A/ris any gaseous constitution, such as in particular normal atmospheric gas.

A mattress is a fabric case filled with resilient material (such as for example cotton, hair, feathers, foam rubber, or an arrangement of springs) used either alone as a bed or on a bedstead to support a person sleeping thereon.

The length and width of a mattress are respectively the head-to-toe direction of a person that lies on the mattress during normal use (as intended by the mattress manufacturer), and the direction in the same plane but perpendicular thereto.

The lifetime of an object is the time between an object's manufacturing for a particular purpose and the point in time where its intended use ends, for example when it is destructed or used for another purpose. A hot melt adhesive is a non-reactive polymer adhesive which contains no solvent (that is less than 2% m/m, in particular less than 1%, or even less than 0.5%, 0.4%, 0.3%, 0.2%, 0.1% or 0% m/m), which adhesive undergoes a reversible first-order phase transition at its melting temperature (Tm), at which temperature the adhesive undergoes a discontinuous change in density. Below the melting temperature the adhesive is a solid, and above this temperature the adhesive is a low viscous liquid, and therewith having no (practical) adhesive properties. It is noted that in the art sometimes adhesives which are not a hot melt adhesive in the above sense are still classified as “hot melt adhesives” simply because they do not contain any solvent. This however does not mean that they undergo a first order solid to liquid transition upon heating, and thus that they are hot melt adhesives in the sense of the present invention.

A pocketed spring is a spring is a spring wrapped in fabric encasement and which may thus deform rather independently from a neighbouring spring in another encasement. Pocketed springs are also called wrapped coils, encased coils, encased springs, or Marshall coils.

EMBODIMENTS OF THE INVENTION

In a first further embodiment of the method according to the invention, the flow of air comprises a first and a second sub-flow, the first sub-flow being directed towards the top layer of the mattress and the second sub-flow being directed towards the base layer of the mattress. It was found that by having these sub-flows directed at the top and base layer of the mattress, the heating of the hot melt adhesive is more effective, requires less time and a lower temperature of the air. This is advantages for preventing any overheating and therewith deterioration of parts of the mattress.

In particular, it was found that air could be used having a temperature between Tm + 5°C to Tm + 30°C, thus ranging from anything between 5-30°C above the melting temperature of the hot melt adhesive. Even stronger, air can be used having a temperature between Tm + 10°C to Tm + 25°C, or even between Tm + 15°C to Tm + 20°C. The latter range combines advantageously quick heating with a very low risk, if any, of deterioration of any materials that constitute the mattress. It was found that heating of the mattress can take place in a time-frame of between 1 -15 minutes of presence in the oven, in particular for 5-10 minutes. Given the inherent insulating properties of a typical pocketed spring mattress, these are very short retention times, well below what was expected before hand when heating at a relatively low temperature of just above Tm of the hot melt adhesive.

In yet a further embodiment, the matrass in the oven lies flat on a supporting surface of a carrier, wherein the supporting surface is open for at least 50% (in particular for at least 51 , 52, 53, 54, 55, 56, 57, 58, 59, 60, 61 , 62, 63, 64, 65, 66, 67, 68, 69, 70, 71 , 72,73, 74, 75, 76, 77, 78, 79, 80, 81 , 82, 83, 84, 85, 86, 87, 88, 89, 90, 91 , 92, 93, 94, 95, 96 97, 98, or even 99%) to allow a free flow of air through the surface towards the mattress. Transporting the mattress lying flat instead of while taking an upright position increases the reliability and hence the automation of the process. However, in order for the airflow to reach the mattress as the site of the carrier, and therewith to effectively heat the mattress in line with the invention, the carrier surface has to be open for more than 50% (meaning that 50% of the area on which the mattress lies is open, not hindered by any material hat blocks the flow of air.

In again a further embodiment of the method of the invention the oven has an extraction unit for actively removing volatile components that are released from the mattress during the heating process.

In yet again a further embodiment of the method of the invention, in which embodiment the oven is a pass-through oven having an entrance and a separate exit, the mattress is transported through the oven from the entrance towards the exit for heating the mattress. This way, a continuous process can be applied to heat a row of mattresses in a consecutive order in one go, instead of heating each mattress (or set of mattresses) batch-wise in a non-pass-through oven (having only one opening, both for entry and exit). This makes automation of the process simpler and hence has the ability to decrease the costs of disassembly. Preferably the mattress is transported through the oven in its width direction while lying flat. The applicant recognised that the variation in length of various sizes of mattresses is not very big (most mattresses have a length between 2.0 and 2.2 meters) whereas the variation in width is very large (typically ranging from 0.8 to 1 .60 meters). By transporting the mattresses in their width direction to the oven, optimal use can be made of (expensive) oven space. In yet a further embodiment, after release from the oven the mattress is transported further but is turned around a vertical axis for 90° such that the mattress is transported further in its length direction. This way, it is easier to handle the taking away steps of the various parts and at least allow the top layer and the optional side walls to be taken away manually, irrespective of the width of the mattresses.

In still a further embodiment, the pocket spring assembly is taken away as one part from the base layer. It was recognised that in particular the assembly of pocketed springs is not only a relatively expensive part of a mattress, but also a part that is often okay for use in manufacturing a new mattress, even if the other parts of the mattress, in particular the top layer and side walls, are substantially worn.

Still, in another embodiment in which the pocketed springs are also adhered to each using the hot melt adhesive, the mattress is heated such that the hot melt adhesive present between adjoining interconnected pockets also acquires a temperature above Tm, whereafter the adjoining pockets are deconnected, in particular after the top layer and side walls are taken away. It was found that it is in many cases not necessary to heat the mattress much longer, since the mattress inherently is a good insulator. Even when the core is not completely heated to reach a temperature above Tm at the end of the heating process in the oven, by transfer of heat through the mattress even after the mattress is taken out of the oven, the hot melt adhesive present between the pockets may still be sufficiently heated.

The invention will now be further explained using the following examples.

EXAMPLES

Figure 1 is a schematic view of the main components of a pocketed spring mattress.

Figure 2 is a side view of variants of a mattress according to figure 1 , provided with a deck layer.

Figure 3 schematically shows a set-up of a semi-automated disassembly method in line with the present invention.

Figure 4 schematically shows details of the set-up of figure 3.

Figure 1

Figure 1 is a schematic view of the main components of a pocketed spring mattress 1 . The mattress has as a base a dimensionally stable felt layer 2, having a length (X direction) and width (Y direction) that are virtually the same as the dimensions of the ultimate mattress (which in addition to the parts shown has an upholstery ticking as a cover). Adhered to the base layer 2 with a polyester hot melt adhesive are two pairs of two opposing resilient side walls (pair 3,4 and pair 5,6 respectively), which side walls are made of a polyester foam and together form an enclosure for the mattress core. The core consists of an assembly of pocketed metal springs 8 (of which only a part is shown in figure 1 ) that fill up the open space 7 of the enclosure. The height of the side walls and pocketed springs (direction Z) correspond to the thickness of the mattress (see also figure 2A and 2B). In this embodiment, the contiguous pockets are made of a polyester fabric. The pockets are interconnected connected using polyester thread (in an alternative embodiment, as described here below with reference to figure 3, the pockets are adhered to each other using the same polyester hot melt adhesive). The same adhesive is used to adhere the pocket assembly to the base layer 2. Also, the pocket assembly is adhered to the sidewall using the same polyester hot melt adhesive. So apart from the felt base layer and the metal springs, all materials of the mattress 1 are made of polyester.

Figure 2

Figure 2 is a side view of variants of a mattress according to figure 1 , provided with a top layer 10, also denoted as the deck layer. This deck layer 10 is connected to the other parts of the mattress using the same hot melt adhesive. The components 2, 5 and 6 are also depicted in figure 1 . In figure 2A a variant is shown wherein the pocketed springs 8 and the side walls 5,6 have the same height, which height corresponds to the height (thickness) of the ultimate mattress, but is slightly less than that height. This is because the deck layer 10 covers the assembly of pocketed springs as well as the top end of the sidewalls. The hot melt adhesive is applied to the top of the sidewalls as well as the top of the pocket spring assembly. In figure 2B a variant is shown wherein the deck layer 10 covers only the assembly of pocketed springs but is laterally enclosed by the sidewalls. The hot melt adhesive is applied to the top of the pocket spring assembly, and the lateral sides of the side walls adjacent their upper end. In this embodiment the side walls have a height that is virtually the same as that of the ultimate mattress, differing only in the thickness of the upholstery cover (as such not shown in figure 2) and the felt base layer.

The complete method of assembling the mattress is described in Dutch priority patent application number N2029662, filed in the name of Koninklijke Auping BV on 8 November 2021 , in particular with reference to the Examples section, starting at page 9, line 5 to page 13, line 15. This example section is incorporated herein by reference.

Figure 3

Figure 3 schematically shows a set-up 20 of a semi-automated disassembly method in line with the present invention. The set-up basically comprises a transport line 21 (including downstream parts 2T and 21 ”) for automatically transporting mattresses 1 (see figures 1 and 2) in a transport direction T from an upstream end (at 21 ) where the mattresses are not yet disassembled (apart from a potential removal of a ticking, if present), towards a downstream end (at 21 ”) where the heated mattress is manually disassembled in its main constituting parts in three consecutive steps. At 21 , the mattress is transported toward the oven in its width direction while lying flat on a carrier (see figure 4 for more details).

The set-up comprises a pass-through convection oven 22, having an entrance 25 and an exit 26, in which oven the mattress is heated as a whole, using air having a temperature of 20°C above the Tm of the hot melt adhesive, in this case a polyester adhesive having a Tm of 130°C. The air thus has a temperature of 150°C which is well below any deterioration temperature of any of the other materials used in the mattress. The oven 22 comprises an extraction unit 23 for actively removing volatile components that are released from the mattress during the heating process. During a period of 10 minutes the mattress gets heated and then leaves the oven at exit 26. The mattress is transported further after release from the oven, but the mattress is firstly turned around a vertical axis for 90°C (indicated with an R; section 21 ’) such that the mattress is transported further in its length direction.

At section 21 ”A, the top layer and side walls are taken away manually. Because of the hot melt adhesive being heated above Tm, it has virtually lost its adhesive properties and these parts can easily be taken away using light manual force. At section 21 ”B, the mattress (what is left of it) is turned around and the base layer is taken away manually. Lastly, at section 21 ”C the assembly of pocketed springs is checked and if okay, left on the transport line for further use. If the assembly is not okay, it is removed from the line.

In the alternative embodiment as referred to here above with reference to figure 1 , in which embodiment the pocketed springs are adhered to each other using the hot melt adhesive, the mattress is heated such that the hot melt adhesive present between adjoining interconnected pockets also acquires a temperature above Tm. If so, the adjoining pockets are deconnected automatically by cascading the assembly in a container (not shown). In this case, at section 21 ”B, the mattress is not turned around, but the base layer is manually grabbed before the pocketed springs are cascaded into the container, and then put aside for further use.

It is noted that the steps of manually removing the various parts from the mattress can in principle also be automated, for example using robotic arms to take away the various parts.

Figure 4

Figure 4 schematically shows details of the set-up of figure 3. It can be seen that the transport line 21 is in fact as assembly of consecutive rollers, as is commonly known in the art. The distance between the rollers is such that air can freely flow between each pair of adjacent rollers.

The mattress 1 is lying flat on a carrier 27, a metal frame with a bottom that is open for 95% of its surface (a metal gauze). The carrier lies on the rollers and is therewith forwarded into the oven 22 through entrance opening 25 that is covered with a flexible cover 28. In the oven fans 29 are present to provide for the air flow. In this oven the flow of air comprises a first and a second sub-flow, the first sub-flow 30 being directed towards the top layer of the mattress and the second sub-flow 31 being directed towards the base layer of the mattress.

It is noted that it is an option to use different types of hot melt adhesive to interconnect different parts. For example, it is foreseen that the pocketed springs are interconnected to form the assembly of pocket springs using a hot melt adhesive with a slightly higher melting point. This way, using different oven settings a selective disassembly process can be performed.

Claims

1 . A method for disassembling a mattress comprising as constituting parts a) a base layer, b) an in essence rectangular assembly of contiguous pocketed springs provided on the base layer, c) a resilient top layer to cover the assembly of pocketed springs, and d) optionally resilient side walls at opposing lateral sides of the assembly of pocketed springs, wherein the said constituting parts a) to c) and the optional part d) are interconnected with a hot melt adhesive that has a melting temperature Tm, characterised in that the method comprises putting the said mattress in a convection oven wherein a flow of air is created, wherein the air has a temperature above Tm and below Tm + 50°C, heating the mattress until the hot melt adhesive acquires a temperature above Tm, releasing the mattrass from the oven and taking away the top layer, the base layer and the optional side walls, from the assembly of pocketed springs.

2. A method according to claim 1 , characterised in that the flow of air comprises a first and a second sub-flow, the first sub-flow being directed towards the top layer of the mattress and the second sub-flow being directed towards the base layer of the mattress.

3. A method according to any of the preceding claims, characterised in that the air has a temperature between Tm + 5°C to Tm + 30°C.

4. A method according to any of the preceding claims, characterised in that the air has a temperature between Tm + 10°C to Tm + 25°C.

5. A method according to any of the preceding claims, characterised in that the air has a temperature between Tm + 15°C to Tm + 20°C.

6. A method according to any of the preceding claims, characterised in that the mattress is heated in the oven for 1 -15 minutes.

7. A method according to any of the preceding claims, characterised in that the mattress is heated in the oven for 5-10 minutes.

8. A method according to any of the preceding claims, characterised in that the matrass in the oven lies flat on a supporting surface of a carrier, wherein the supporting surface is open for at least 50% to allow a free flow of air through the supporting surface towards the mattress.

9. A method according to any of the preceding claims, characterised in that the oven has an extraction unit for actively removing volatile components that are released from the mattress during the heating process.

10. A method according to any of the preceding claims, wherein the oven is a pass- through oven having an entrance and an exit, characterised in that the mattress is transported through the oven from the entrance towards the exit for heating the mattress.

11 . A method according to claim 10, wherein the mattress has a length, a width and a thickness, characterised in that the mattress is transported through the oven in its width direction while lying flat.

12. A method according to claim 11 , wherein the mattress is transported further after release from the oven, characterised in that the mattress is turned around a vertical axis for 90° such that the mattress is transported further in its length direction.

13. A method according to any of the preceding claims, characterised in that the top layer and the optional side walls are taken away manually.

14. A method according to any of the preceding claims, characterised in that the pocket spring assembly is taken away as one part from the base layer.

15. A method according to any of the claims 1 -14, wherein the pocketed springs are adhered to each other and thereby form the assembly of pocketed springs using the hot melt adhesive, characterised in that the mattress is heated such that the hot melt adhesive present between adjoining interconnected pockets acquires a temperature above Tm, whereafter the adjoining pockets are deconnected, in particular after the top layer and the optional side walls are taken away.