Recyclable safety shoe and associated methods for manufacture and recycling

Abstract

A safety shoe (1) comprising an upper (10), a protective toe cap (20) which fulfils safety requirements with respect to resistance against impact, compression, penetration and temperature and an outsole (30), wherein a majority by weight of the upper, the protective toe cap and the outsole are made of bio-based thermoplastic material from the same material class A method for manufacturing the safety shoe as well as recovering materials from the safety shoe are also disclosed.

Description

RECYCLABLE SAFETY SHOE AND ASSOCIATED METHODS FOR MANUFACTURE AND RECYCLINGTechnical Field

[0001] The present invention relates to a recyclable safety shoe as well as methods for manufacturing a recyclable safety shoe and recovering material from a recyclable safety shoe.Background

[0002] The manufacture of footwear represents a considerable environmental impact. Estimates of the annual production range from 20-25 billion pairs of shoes and a large part of these end up in incinerators or landfills. Recycling footwear could thus help reducing the carbon footprint of the clothing industry. However, footwear is made from a wide variety of materials which present challenges to recycling.

[0003] EP3081109A1 discloses a sports shoe comprising an upper and a sole made of the same bio-based thermoplastic material selected from thermoplastic polyurethane (TPU), polyamide (PA), polyethylene terephthalate (PET), or polybutylene terephthalate (PBT).

[0004] US2023354947A1 discloses a shoe including recycled thermoplastic material, in the form of a heel counter with a density greater than that of the sole component. The recycled material is derived from scrap foam material from an operation of making the midsole of the shoe.

[0005] The complications with recycling are even more true regarding personal protective equipment (PPE) footwear, which have high protection requirements, e.g. according to European standard EN ISO 20345 :2021 / Amd 1:2024 or United States standard ASTM F2413-24 regarding safety footwear as a whole or EN ISO 22568-2:2019 and ASTM F2412-24 regarding the protective toe cap. In order to fulfil protection standards with respect to reinforcement in the toe (toe cap), penetration resistance, electrical resistance, thermal insulation, chemical resistance and / or skid resistance, different materials with different characteristics are combined to manufacture safety footwear. Protection standards also require specific constructions of the safety features inthe footwear which make them more difficult to recycle. As an example, a protective toe cap needs to be positioned inside the upper of the shoe to prevent unintended removal, which in turn leads to a more arduous process of separation to enable recycling.

[0006] WO2022179693 Al discloses a protective cap for footwear composed of a multilayer structure including a polymeric bonding material comprising at least one recycled material and at least one plasticizer. However, only a small portion of the recycled material originates from waste materials, whereas the majority comes from freshly produced raw materials.

[0007] Hence, there is a need to develop improved solutions for reducing the environmental impact of safety footwear.Summary of Invention

[0008] An objective of the present disclosure is therefore to provide an improved safety shoe to solve the problems identified above.

[0009] According to a first aspect of the present disclosure, there is provided a safety shoe comprising an upper; a protective toe cap which fulfils safety requirements with respect to resistance against impact, compression, penetration and temperature; and an outsole, wherein a majority by weight of the upper, the protective toe cap and the outsole are made of bio-based thermoplastic material from the same material class.

[0010] By providing a safety shoe with an upper, a protective toe cap and an outsole which are predominantly made of the same base material, the base material can be easily recovered from the safety shoe, without requiring separating and / or sorting the different components of the safety shoe. This allows the whole safety shoe to be prepared for recycling in a single step, e.g. by grinding the components of the safety shoe into pieces which may then be further treated to obtain raw material to be used in production of new safety shoes. The safety shoes according to the present invention may greatly simplify the recycling of used safety shoes, especially when the entire safety shoe is made from a single material. Moreover, the recovered base material may then be re-used both for the upper, the protective toe cap and / or the outsole of a new safety shoe such that all threecomponents may essentially be fabricated from the same recycled material. This brings lower costs and follows circular economy principles when materials stay in the loop.

[0011] Using substantially the same base material in the upper, the protective toe cap and the outsole and at the same time providing a high-quality safety shoe is enabled by the idea that various physical implementations (e.g. yam, foil, foam, pellets etc.) of one and the same chemical base material (e.g. thermoplastic polyamide) may be used to provide the various different properties that are needed to provide high-quality safety shoes (e.g. impact resistance, good comfort and feel). Another advantage with using substantially the same base material for the upper and the outsole is that joining of the two components is facilitated. The joining may be achieved even without involving any adhesives, e.g. by applying energy (heat) to melt the surfaces.

[0012] In one embodiment, the protective toe cap fulfils the safety requirements of European standard EN ISO 22568-2:2019 or United States standard ASTM 2412-24.

[0013] In one embodiment, the bio-based thermoplastic material is selected from one of the following materials: thermoplastic polyurethane (TPU), polyamide (PA), polyethylene (PE), polybutylene terephthalate (PBT), polylactic acid (PLA), polyhydroxyalkanoate (PHA), polybutylene succinate (PBS), polytrimethylene terephthalate (PTT), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), starch-based thermoplastics (TPS), or other polyesters. Preferably, the bio-based thermoplastic material is selected from PA6, PA66, PAI 1, PA1010, PA612, PA610, PAI 012, PA410, PA 12. Especially the use of PAI 1 for all components of the safety shoe enables an environmentally friendly manufacture since the raw material is sourced from castor beans which do not compete with food stocks.

[0014] In one embodiment, the upper comprises yam made of the bio-based thermoplastic material. The yam may be used to form the upper by knitting, weaving, braiding, crocheting, nalebinding (knotless knitting) or a combination thereof.

[0015] In one embodiment, the upper is a three-dimensional structure formed in one piece. In one embodiment, the upper is manufactured using 3D knitting, 3D braiding, 3D weaving and / or 3D printing to form a three-dimensional structure. These 3D textileforming techniques allow the shoe upper to be produced in one piece without any waste. Additionally, when the protective toe cap is also attached between the layers during the 3D textile forming, the manufacturing can be earned out in one process.

[0016] In one embodiment, the bio-based thermoplastic material comprises material recycled from another safety shoe. This contributes to keeping the material in the loop, thereby requiring less virgin material for manufacturing new safety shoes.

[0017] In one embodiment, at least 70%, preferably at least 80%, more preferably at least 90% and most preferably at least 95% of the weight of the upper, the protective toe cap and the outsole are made of bio-based thermoplastic material from the same material class.

[0018] In a second aspect of the present disclosure, there is provided a method for manufacturing a safety shoe, comprising the steps:manufacturing an upper;manufacturing a protective toe cap which fulfils safety requirements with respect to resistance against impact, compression, penetration and temperature;manufacturing an outsole;wherein the upper, the protective toe cap and the outsole are manufactured as separate components;attaching the protective toe cap to the upper; andattaching the upper with the protective toe cap to the outsole,wherein a majority by weight of the upper, the protective toe cap and the outsole are made of bio-based thermoplastic material from the same material class.

[0019] In one embodiment, the step of manufacturing the upper comprises 3D knitting, 3D weaving, 3D braiding and / or 3D printing to form a three-dimensional footshaped structure in one piece.

[0020] In one embodiment, the bio-based thermoplastic material is provided by recycling the upper, the protective toe cap and / or the outsole of another safety shoe.

[0021] In a third aspect of the present disclosure, there is provided a method for recovering a material from a safety shoe, comprising the steps:providing a safety shoe according to the first aspect;milling the shoe to obtain a plurality of particles;mixing the particles;applying heat to the particles to obtain a melt of molten particles;processing the melt to form an intermediate product; andprocessing the intermediate product to form a component for a new safety shoe.

[0022] Since a majority by weight of the safety shoe, i.e. the upper, the protective toe cap and the outsole are made of bio-based thermoplastic material from the same material class, it is possible to recover the material in a simplified process without requiring separating the components of the safety shoe prior to milling. By melting the milled and mixed particles, a homogeneous mass of molten material is obtained which allows manufacture of new safety shoe components, either directly or by means of an intermediate product such as pellets, yam etc.

[0023] In one embodiment, the component for a new safety shoe is one or more of, an upper, a protective toe cap, an outsole, a shank piece, a Strobel board, a heel counter or nail penetration material made from the same material class.

[0024] In one embodiment, the method further comprises the step of adding material to the mixed particles and / or the melt. The added material may be intermediate products from a prior recycling process and / or virgin material of the same material class as the components of the safety shoe.Brief Description of Drawings

[0025] The disclosure is now described, by way of example, with reference to the accompanying drawings, in which:Fig. 1 shows a safety shoe according to one embodiment of the present disclosure;Fig. 2 shows different components of a safety shoe according to one embodiment of the present disclosure;Fig. 3 shows different steps of manufacturing a safety shoe according to one embodiment of the present disclosure;Fig. 4 shows a first part of recovering material from a safety shoe according to one embodiment of the present disclosure; andFig. 5 shows an illustration of a material loop for a safety shoe according to one embodiment of the present disclosure.Detailed Description

[0026] In the following, a detailed description of a recyclable safety shoe and associated methods according to the present disclosure is presented. In the drawing figures, like reference numerals designate identical or corresponding elements throughout the several figures. It will be appreciated that these figures are for illustration only and do not in any way restrict the scope of the present disclosure. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of ‘including’, ‘comprising’, or ‘having’ and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otheiwise, the terms ‘mounted’, ‘connected’, ‘supported’, and ‘coupled’ and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings.Further, ‘connected’ and ‘coupled’ are not restricted to physical or mechanical connections or couplings.

[0027] In the context of the present invention, the term ‘material class’ used in conjunction with thermoplastic material shall be interpreted as a group or class of polymers having the same or similar characteristics. It is known that thermoplastic material is generally classified into to three polymer families or classes: amorphous, semi-crystalline and elastomers.

[0028] The term “bio-based,” when used in conjunction with thermoplastic material, shall be interpreted as polymers derived partially or entirely from carbon-neutral or carbonnegative feedstocks, where the bio-based content originates entirely or partly from biological sources (e.g., renewable plant, forestry, animal, algal, or marine materials) verified via radiocarbon analysis as defined by ASTM D6866, or alternatively where atleast a portion of the feedstock used to produce the bio-based thermoplastic is derived from biomass rather than fossil-based sources, following the mass-balance approach.

[0029] Referring now to Fig. 1, there is shown a safety shoe 1 according to the present disclosure in a perspective view. The safety shoe 1 comprises an upper 10, a protective toe cap 20 and an outsole 30. The protective toe cap 20 is attached to the upper 10 in such a way that it may not be easily removed. One way of achieving this is to insert the protective toe cap 20 in an integrated pocket of the upper 10 formed during manufacture thereof. Although the protective toe cap 20 is illustrated in Fig. 1 as being attached to the upper 10 as an exterior component, the present disclosure also encompasses solutions wherein the protective toe cap 20 is incorporated in the upper 10 or otherwise joined to the upper 10 as an interior component which is not visible from the outside.

[0030] The upper 10, the protective toe cap 20 and the outsole 30 are all by majority of weight made of bio-based thermoplastic material from the same material class. The biobased thermoplastic material may be selected from one of the following materials: thermoplastic polyurethane (TPU), polyamide (PA), polyethylene (PE), polybutylene terephthalate (PBT), polylactic acid (PLA), polyhydroxyalkanoate (PHA), polybutylene succinate (PBS), polytrimethylene terephthalate (PTT), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), starch-based thermoplastics (TPS), or other polyesters. With reference to the term ‘material class’ explained above, TPU belongs to the class thermoplastic elastomers, whereas PA, PE, PBT, PTT, PP, PBS, PLA and PHA belong to the class semi-crystalline thermoplastics, and PC, PET, and TPS to the class of amorphous thermoplastics. The polyamide PA may in turn be selected from one of PA6, PA66, PAI 1, PA1010, PA612, PA610, PA1012, PA410, PA12. Especially the use of PAI 1 for all components of the safety shoe 1 enables an environmentally friendly manufacture since the raw material is sourced from castor beans which do not compete with food stocks.

[0031] In one embodiment, the outsole 30 comprises poly ether block amide, PEBA. PEBA is a high-performance thermoplastic elastomer with superior mechanical and dynamic properties (flexibility, impact resistance, energy return, fatigue resistance) and keeping these properties at low temperature (lower than -40 °C), and good resistanceagainst a wide range of chemicals. The outsole material could be also supercritical foam such as TPU or polyamide made with a supercritical fluid foaming process.

[0032] The different components serve different purposes in the safety shoe such as e.g. cushioning, energy return, fatigue resistance for the outsole 30, comfortable fit for the foot for the upper 10 and impact resistance for the protective toe cap 20. In the present case with all components being made entirely or by majority of weight of the same material class, the respective material properties are achieved by varying the density and manufacturing technique of each component.

[0033] For example, the upper 10 may be formed by yam made of the bio-based thermoplastic material. The yam is then knitted, woven, braided, crocheted and / or nalebound to form a fabric structure of the upper 10. In Fig. 2, the upper 20 is illustrated prior to assembly of the safety shoe 1. The upper 10 may be formed as a three-dimensional structure in one piece, e.g. a sock-shaped structure matching the shape of a foot. For example, the upper 10 may be manufactured using 3D textile techniques such as 3D knitting, 3D weaving, 3D braiding and / or 3D printing to form the three-dimensional structure. 3D knitting may be carried out using a circular knitting machine. 3D textile forming techniques have the advantage of producing a desired three-dimensional structure in one process whilst reducing waste of materials in that only the material required for manufacture is used. Scraps of material may be eliminated altogether. Advantageously, reinforced portions to create e.g. toe bumper and heel bumper effects may be formed in the upper 10 by manipulating the yam accordingly during manufacturing. The upper 10 may also comprise a specialised type of hotmelt yam such as polyamide, TPU or polyester that melts and creates reinforcement areas to the upper 10, e.g. in the toe or heel area.

[0034] Referring further to Fig. 2, there is shown components of a safety shoe 1 prior to assembly, including a protective cap 20 which fulfils safety requirements with respect to resistance against impact, compression, penetration and temperature. In one embodiment, the protective toe cap 20 fulfils the safety requirements of European standard EN ISO 22568-2:2019 for non-metallic toe caps or United States standard ASTM 2412-24. It is understood that the protective toe cap 20 used in the safety shoe 1 according to the present disclosure is intended to function as a component of PPE footwear and thus fulfils the necessary protection requirements according to the applicable safety standards of the localmarket, e.g. Europe, North America, Asia etc. A shank piece 25 to be placed between the insole and outsole 30 to support the foot and provide structure to the safety shoe 1. The shank piece 25 may be made from the bio-based thermoplastic material reinforced with fiberglass. A heel counter 22 for stabilising the heel portion of the safety shoe 1. Similar to the protective cap 20, the heel counter 22 may be inserted in an integrated pocket of the upper 10. A waterproof membrane 15 can be provided over the upper 10. A Strobel board 35 to be attached to the upper 10. The Strobel board 35 may provide resistance to nail penetration. All the components above can be made from the same bio-based thermoplastic material described above.

[0035] Referring now to Fig. 3, different stages (a)-(g) of a manufacturing process of the safety shoe 1 are illustrated. In a first stage (a), a last 5 is provided. The upper 10 illustrated in stage (b) is then brought over the last 5 as shown in stage (c). Subsequently, in stage (d) the protective toe cap 20, and optionally the heel counter 22, is attached or joined to the upper 10. As explained above, this may be done by inserting the components in integrated pockets formed in the upper 10 during manufacture. Next, in stage (e) optionally a waterproof membrane is attached to the upper 10. In stage (f), the shank piece 25 and / or Strober board 35 is attached to the upper 10 and the upper structure of the safety shoe 1 is finalized. Finally, in stage (g) the outsole 30 is attached to the upper 10 to complete the safety shoe 1.

[0036] Referring now to Fig. 4, there is shown a schematic illustration of the first stage of the recycling process wherein safety shoes 1 are milled or shredded into smaller pieces or particles by means of a pair of rotating cutting elements 40. It is also foreseen that parts of safety shoes, such as uppers 10, may be recycled at this stage. For example, components that do not fulfil the quality requirements or for other reasons cannot be used in manufacturing new safety shoes may be recycled together with worn-out safety shoes.

[0037] After milling, the particles are mixed, e.g. by means of rotating cylinders 50, to create a substantially homogeneous mixture of particles. At this stage, additional materials may be introduced into the mixture, such as intermediate products from a prior recycling process in the form of pellets 60 and / or new virgin material 70 from the same material class as the components of the safety shoe 1. After mixing, the particles are subjected to heat to obtain a melt of molten particles whereafter the melt is processed to obtain anintermediate product. The intermediate product may include pellets, yam and / or film of the thus recycled bio-based thermoplastic material. This may be done e.g. by means of plastics extrusion using an appropriate extruder.

[0038] Referring now to Fig. 5, there is shown a schematic illustration of a loop showing the different forms of the material used in a safety shoe 1. On the right side of Fig.5, a safety shoe 1 according to the present disclosure is shown. When the safety shoe 1 is worn out or deemed to no longer be of use, it is sent to a suitable plant for recycling. There, the safety shoe 1 is milled into particles, mixed, heated and formed into intermediate products, such as pellets 60. The pellets 60 are then used as base material to manufacture new components of a safety shoe 1, such as a protective toe cap 20. The protective toe cap 20 is then used in the manufacture of a new safety shoe 1, thus completing the loop.

[0039] Embodiments of a recyclable safety shoe and associated methods for manufacturing and recovering material according to the present disclosure have been described. However, the person skilled in the art realizes that this can be varied within the scope of the appended claims without departing from the inventive idea.

[0040] All the described alternative embodiments above or parts of an embodiment can be freely combined without departing from the inventive idea as long as the combination is not contradictory.

Claims

CLAIMS1. A safety shoe (1) comprising:an upper (10);a protective toe cap (20) which fulfils safety requirements with respect to resistance against impact, compression, penetration and temperature; andan outsole (30);wherein a majority by weight of the upper (10), the protective toe cap (20) and the outsole (30) are made of bio-based thermoplastic material from the same material class.

2. The safety shoe (1) according to claim 1, wherein the protective toe cap (20) fulfils the safety requirements of European standard EN ISO 22568-2:2019 or United States standard ASTM 2412-24.

3. The safety shoe (1) according to claim 1 or 2, wherein the bio-based thermoplastic material is selected from one of the following materials: thermoplastic polyurethane (TPU), polyamide (PA), polyethylene (PE), polybutylene terephthalate (PBT), polylactic acid (PLA), polyhydroxyalkanoate (PHA), polybutylene succinate (PBS), polytrimethylene terephthalate (PTT), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), starch-based thermoplastics (TPS), or other polyesters.

4. The safety shoe (1) according to any one of the preceding claims, wherein the upper (10) comprises yam made of the bio-based thermoplastic material.

5. The safety shoe (1) according to any one of the preceding claims, wherein the upper (10) is a three-dimensional structure formed in one piece.

6. The safety shoe (1) according to claim 5, wherein the upper (10) is manufactured using 3D knitting, 3D weaving, 3D braiding and / or 3D printing to form the three-dimensional structure.

7. The safety shoe (1) according to any one of the preceding claims, wherein the bio-based thermoplastic material comprises material recycled from another safety shoe.

8. The safety shoe (1) according to any one of the preceding claims, wherein at least 70%, preferably at least 80%, more preferably at least 90% and most preferably at least 95% of the weight of the upper (10), the outsole (30) and the protective toe cap (20) are made of bio-based thermoplastic material from the same material class.

9. A method for manufacturing a safety shoe, comprising the steps:manufacturing an upper (10);manufacturing a protective toe cap (20) which fulfils safety requirements with respect to resistance against impact, compression, penetration and temperature;manufacturing an outsole (30);wherein the upper (10), the protective toe cap (20) and the outsole (30) are manufactured as separate components;attaching the protective toe cap (20) to the upper (10); andattaching the upper (10) with the protective toe cap (20) to the outsole (30), wherein a majority by weight of the upper (10), the protective toe cap (20) and the outsole (30) are made of bio-based thermoplastic material from the same material class.

10. The method according to claim 9, wherein the step of manufacturing the upper (10) comprises 3D knitting, 3D weaving, 3D braiding and / or 3D printing to form a three-dimensional foot-shaped structure in one piece.

11. The method according to claim 9 or 10, wherein the bio-based thermoplastic material is provided by recycling the upper (10), the protective toe cap (20) and / or the outsole (30) of another safety shoe.

12. A method for recovering a material from a safety shoe, comprising the steps:providing a safety shoe (1) according to any one of claims 1-8;milling the safety shoe (1) to obtain a plurality of particles;mixing the particles;applying heat to the particles to obtain a melt of molten particles;processing the melt to form an intermediate product; andprocessing the intermediate product to form a component for a new safety shoe.

13. The method according to claim 12, wherein the component for a new safety shoe (1) is one or more of, an upper (10), a protective toe cap (20), an outsole (30), a shank piece (25), a Strobel board (35) and a heel counter (22).

14. The method according to claim 12 or 13, further comprising the step of adding material to the mixed particles and / or the melt.

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