Technical field

The present invention relates to multi-component binder fiber for use in cushion materials. Further, the present invention relates to a cushion material comprising multi-component binder fibers and staple fibers.

Background

In the art, flexible and semi-flexible polyurethane foams have found extensive use as upholstered furniture cushion materials, e.g. in seats and backs of chairs and sofas. An important feature of cushion materials, is their ability to be compressed and distribute surface pressure, and to recover after the load is removed, also after repeated compression and de-compression. However, given the use of isocyanates in producing polyurethane, as well as the formation of isocyanates and/or hydrogen cyanide upon combustion of polyurethanes, alternative cushion materials are desired. Further, polyurethane foams are not suited for recycling. Sustainable alternatives are thus desired.

Blends of polyethyleneterephthalate (PET) and co-PET used for high-loft cross-lapped nonwovens - often called waddings or battings - are recyclable and do not give rise to hazardous chemicals when combusted, but they do typically not provide sufficient performance to replace polyurethane foams. To further improve mechanical properties other polyesters than PET and Co-PET has been used, such as PBT and PTT including co-polymers thereof.

This has led to the development of polyester based cushion materials. In WO 2018/099962 molded cushion members provided by molding a fiber blank comprising a thermally activated binding agent into a three-dimensional fiber block article are disclosed. The molded cushion members are typically polyester based. The molded cushion members are typically molded three-dimensional fiber block article that are resilient. Such resilient three-dimensional fiber block articles are useful as comfort filings in furniture applications, e.g. as cushion members in seats and/or back rest of sofas and chairs.

Another polyester based material for cushion members is provided by Teijin. The material is sold as elk®. Polyester based cushion materials are general safe, as very low amounts of toxic gases form upon combustion thereof and the fire behavior becomes less dangerous. Elk® comprises a 3-dimentional nonwoven structure, and it helps keep a stable fix at the cross point between crossing fibers. Elk® is stated to have good stability at an intersection of the fiber structure, which improve the basic performances, such as air permeability, elasticity and durability. Further, contrary to polyurethane, even if elk® is combusted, there is little toxic gases formed. Therefore, it is reported to make a substantial contribution to the global environment, industry and life. According to Teijin, the properties of elk® are associated with a special bi-component binder fiber, which makes the stable cross point keep the form of structure. This structure is alleged to keep the appropriate hardness upon loading. The properties of bi-component binder fiber used in elk® are associated, at least partly, with its eccentric cross-section

(cf. WO 97/23670 and Fig. 1 herein). The general composition of the bi-component binder fiber used in elk® was known already back in 1991, as can be seen from inter alia EiS 5,183,708, relating to a novel cushion structure which comprises non- elastomeric, crimped polyester staple fibers serving as the matrix in which heat-bonded spots with elastomeric conjugated fibers are scattered. It is stated that the cushioning structure has improved impact resilience, compression endurance and compression recovery and free from the impression of bottoming out. However, in order to achieve this, the cushion member has to have a high density. Further, a relatively large proportion of the binder fiber is required. Still, it has been found that the cushion material elk® is prone to suffer from the impression of bottoming out, especially after prolonged use.

Thus, there is a need in the art to provide an improved cushion material. Especially, it would be of interest to improve the pressure distribution provided by the cushion material to avoid the impression of bottoming out. Further, it would also be of interest to be able to reduce the amount of material needed, in order to keep the cost down, due to the comparatively more expensive co-polymers used, to provide the desired cushion effect.

Summary Accordingly, there is according to a first aspect provided a multi-component binder fiber. The multi-component binder fiber comprises at least a first component, such as a core component, and a second component, such as a sheath component. In the binder fiber, the second component acts as binding component, typically as a heat activated binding component. The components may be arranged in different ways in the multi-component binder fiber, such as side-by-side or in core-sheath manner. If arranged in a core- sheath manner, the first component may be arranged as a core component, and the second component as a sheath component. Further, the sheath and the core may be concentrically arranged in such embodiment, the cross-section of the fiber typically being cylindrical. Alternatively, the sheath and the core may be eccentrically arranged in such embodiment, the cross-section of the fiber typically being cylindrical.

The first component of the multi-component fiber comprises a first thermoplastic polymer. The melting point of the first thermoplastic polymer is at least 200°C. Similarly, the second component of the multi-component fiber comprises a second thermoplastic polymer. The melting point of the second thermoplastic polymer is lower than the melting point of the first thermoplastic polymer. The melting point of the second thermoplastic polymer may be at least 20°C, such as at least 30°C, lower than the melting point of the first thermoplastic polymer.

The second thermoplastic polymer is a block-copolymer in the form of a co- polyester polyether. The block-copolymer comprises first blocks of a polyester and second blocks of an aliphatic polyether. The first blocks of the block-copolymer, being a polyester block, comprises residues of a first alkylenediol, residues of terephthalic acid (benzene- 1,4-dicarboxylic acid), and residues of isophthalic acid (benzene-1, 3- dicarboxylic acid). The molar ratio of residues of terephthalic acid to residues of isophthalic acid in the first blocks of the polyester is 2:1 to 4:1. The second blocks of the block-copolymer, being an aliphatic polyether block, comprises residues of a second alkylenediol.

The molar ratio of residues of the first alkylenediol of the polyester to the residues of the second alkylenediol of the aliphatic polyether is at least 1:1, such as 1:1 to 3:1, or 1.5:1 to 2.5:1. Whereas the first blocks may be considered to represent hard segments, the second blocks may be considered to represent soft segments. The ratio between the hard and soft segments will affect the properties of the polymer. Further, the isomer ratio within the hard segments, i.e. the molar ratio of residues of terephthalic acid to residues of isophthalic acid could be seen as affecting the hardness of the hard segments. Thus, the overall properties of the block-copolymer result from various factors in a complex manner.

A block co-polyester polyether may have the general structural formula below, if the first blocks are poly (butylene terephthalate co-isophthalate) and the second blocks are poly(tetram ethylene ether) glycol. The molar ratio of residues of the first alkylenediol (butylene - (Clh - in the structural formula below) of the semi-aromatic polyester to the residues of the second alkylenediol (butylene - (0¾)4 - in the structural formula below) of the aliphatic polyether is given by the ratio of the numbers “m” and “n”, representing the number of repeating units in each block, i.e. the ratio corresponds to m:n. As “m” and “n” represent the average number of repeating units, they are typically not integers, while they inherently are integers in a discrete, given molecule. The ratio m:n may be determined by ¾ NMR (Proton nuclear magnetic resonance), as the chemical shifts of the butylene groups will differ (ester vs. ether).

Blocks of a semi-aromatic polyester Blocks of an aliphatic poly ether

Structural formula of a block co-polyester polyether (i.e. co-poly (butylene terephthalate co-isophthalate ) polytetramethylene oxide)

In the multi-component binder fiber of the present invention, the molar ratio of residues of the first alkylenediol of the polyester to the residues of the second alkylenediol of the aliphatic polyether is at least 1:1, such as 1:1 to 3:1, or 1.5:1 to 2.5:1. On the contrary, in the bi-component fiber of elk®, the corresponding ratio is about 1 :2, i.e. far less than 1:1. Further, the molar ratio of residues of terephthalic acid to residues of isophthalic acid in the first blocks of the polyester of the present invention is 2: 1 to 4:1; preferably lower than 3:1, such as lower than 2.7:1. Thus, the molar ratio may be from 2:1 to less than 3:1, such as from 2:1 to less than 2.7:1. Structural formulae of residues of terephthalic acid and isophthalic acid, respectively, are provided below.

Residues of terephthalic acid (left) and isophthalic acid (right)

Further, the melting point of the second component, acting as binding component, of the present multi-component binder fiber is somewhat higher (about 10 degrees Celsius) than the melting point of the corresponding second component typical bi-component binder fibers in the art. The melting point of the second component of the present multi-component binder fiber may be in the range of 155 to 175°C, such as in the range 160 to 170°C.

It was surprisingly found that when such a multi-component binder fiber is used together with staple fibers to provide a heat bonded nonwoven, the heat bonded nonwoven has improved pressure distribution, also after prolonged use. Improved pressure distribution will lessen or even eliminate the impression of bottoming out. Further, less material may be required to provide corresponding or improved properties as for elk®, at least according to some embodiments. For a cushion member, the ability of the heat bonded nonwoven to distribute pressure, whereby affecting the resulting maximum pressure, is a desired property, in order to avoid a too high pressure at a specific, limited area (cf. Figs. 6 and 11). This is often referred to as bottoming out. Without being bound by any theory, it is believed that the improved properties result from the composition of the present multi-component binder fiber. The properties of elk® may be improved by increasing the surface weight of the nonwoven (i.e. using more fibers) and/or increasing the amount of binder fiber in the nonwoven. This will however also increase the cost.

The first thermoplastic polymer may be a polyester, such as polyethyleneterephthalate (PET), polybuty 1 eneterephthal ate (PBT), poly(trimethylene terephthalate) (PTT), or polyethylene furanoate (PEF). According to an embodiment, the first thermoplastic polymer is polyethyleneterephthalate (PET) or polybuty 1 eneterephthal ate (PBT).

The second thermoplastic polymer is a co-polyester polyether. According to an embodiment, the polyester in the first blocks is poly (butylene terephthalate co- isophthalate). Further, the aliphatic polyether in the second blocks may be poly(tetramethylene ether) glycol (also known as polytetrahydrofuran or poly(tetramethylene oxide)). Preferably, the polyester in the first blocks is poly (butylene terephthalate co-isophthalate) and the aliphatic polyether in the second blocks is poly(tetramethylene ether) glycol. Thus, according to a preferred embodiment, the polyester in the first blocks is poly (butylene terephthalate co-isophthalate) and the second aliphatic polyether in the second blocks is poly(tetramethylene ether) glycol. In such an embodiment, the molar ratio of butylene (cf. poly (butylene terephthalate co- isophthalate)) to tetramethylene (cf. poly(tetramethylene ether) glycol) may be 1 : 1 to 3:1, such as 1.5:1 to 2.5:1. A multi-component binder fiber, which according to an embodiment is a bi component binder fiber, comprises at least a first and a second component. The components may be arranged in different ways along the longitudinal extension of the multi-component binder fiber. According to an embodiment, the binder fiber is a sheath-core binder fiber. In such a sheath-core binder fiber, the first component is present in the core and the second component is present in the sheath. Further, the fiber may have different kinds of cross-sections. The cross-section of the present multi- component binder fiber is preferably circular. In a multi-component binder fiber with circular cross-section, the first component and the second component may be concentrically arranged.

According to an embodiment, the first component and the second component are concentrically arranged to provide a self-crimping fiber. The multi-component binder fiber may thus be self-crimping. In such a fiber, the first component and the second component may be arranged side by side. It may however be preferred to use a concentric sheath-core arrangement to maximize the binding efficacy. In such a sheath- core binder fiber, the first component is present in the core and the second component is present in the sheath. Use of a self-crimped binder fiber may facilitate carding and blending with a conjugated or crimped staple fiber.

According to an embodiment, the cross-section of the present multi-component binder fiber is multi-lobal, such as tri-lobal. In a multi-component binder fiber with a tri-lobal cross-section, the first component and the second component are typically concentrically arranged to provide a self-crimping fiber. In such a binder fiber, the second component may be present in the tip of at least one of the lobes, but not all lobes. The ratio of the first component to the second component in the multi - component binder fiber is typically given as a volume ratio, as the feeding ratio in extruding the components to provide the multi-component binder fiber typically determines the ratio. Furthermore, the volume ratio of the first component to the second component in the multi-component binder fiber may be in the range 1:2 to 8:1, such as 1:1 to 5 : 1. Especially from a cost perspective, it is preferred if the second component is the minor component, as it typically is more expensive. Further, the first component being the major component will improve the mechanical properties of the multi - component binder fiber. However, in order to provide for efficient binding, the second component should be present in a sufficient amount. As already mentioned, the melting point of the first thermoplastic polymer is at least 200°C. This first thermoplastic polymer provides the fiber with structural integrity also when heated. The second component serving as binding component has a lower melting point and may hence be activated, e.g. melted, without melting the first component. The second thermoplastic polymer may have a melting point in the range of 155 to 175°C, such as in the range 160 to 170°C. At room temperature, also the second component contributes to the structural integrity and mechanical properties of the multi - component binder fiber. The second thermoplastic polymer may have flexular modulus of at least 80 MPa and/or a tensile modulus of at least 80 MPa. The multi-component binder fiber may have a linear density of 1 to 10 dtex, such as 2 to 8 dtex. Further, the multi-component binder fiber may be 10 to 100 mm long, such as 25 to 80 mm long. The multi-component binder fiber may be provided a spin-finish to improve the processing thereof and/or the properties of the fiber.

Whereas multi-component binder fibers in the art typically are crimped, be it mechanically and/or by self-crimping, it was found that the present multi-component binder fiber may be efficiently blended with a conjugated or crimped staple fiber (cf. Fig. 4b), acting as matrix fiber in providing a nonwoven, without having to crimp the multi-component binder fiber. As the need to crimp the multi-component binder fiber may be dispensed with, the present multi-component binder fiber is easier to produce with consistent properties since one variable to consider in the production is removed. According to an embodiment, the multi-component binder fiber has a lower crimp frequency than 8 crimps/25 mm, preferably less than 5 crimps/25 mm, more preferably less than 3 crimps/25 mm, according to ASTM D 3937-01 (preparation option 9.2.1), and/or a crimp degree below 20%. The binder fiber may be un-crimped, i.e. essentially free from crimps. On the contrary, the binder fiber in elk (cf. Fig. 2) is crimped.

According to an alternative embodiment, the multi-component binder fiber is crimped, such as mechanically crimped. The multi-component binder fiber may in addition or alternatively be self-crimping. Although not necessary, crimping may facilitate carding and blending with a conjugated or crimped staple fiber. The present multi-component binder fiber may thus have a crimp frequency of 1 to 8 crimps/25 mm, according to ASTM D 3937-01 (preparation option 9.2.1).

According to another aspect there is provided a nonwoven comprising the present multi-component binder fibers mixed with staple fibers. The nonwoven is a heat bonded nonwoven, being bonded by activating, i.e. heating, the multi-component binder fibers, to provide a 3 -dimensional nonwoven structure. The staple fibers to be mixed with the multi-component binder fibers typically have the following properties:

- a length of 25 to 100 mm, such as 38-75 mm, or 50-64 mm; and/or

- a linear density of 1 to 20 dtex, such as 4 to 16 dtex, or 6 to 12 dtex; and/or - are crimped fibers or conjugated fibers; and/or

- a solid or hollow cross-section, preferably a hollow cross-section (typically 10 to 25% of the cross-section being hollow); and/or

- are polyester fibers, such as fibers of poly ethyl eneterephthal ate (PET), polybutyleneterephthalate (PBT), poly(trimethylene terephthalate) (PTT), or polyethylene furanoate (PEF); preferably the polyester fibers are fibers of polyethyleneterephthalate (PET), or polybuty 1 eneterephthal ate (PBT).

According to an embodiment, the staple fibers are polyester fibers, such as polyethyleneterephthalate (PET) fibers or polybuty 1 eneterephthal ate (PBT) fibers. Such staple fibers may be 38-75 mm long, such as 50-64 mm long, and a have linear density of 4 to 16 dtex, such as 6 to 12 dtex. Further, the staple fibers are crimped or conjugated; preferably they are conjugated. Crimping is cheaper but conjugation generally provides better filling power and resilient properties. Furthermore, it is preferred if the polyester fibers have a hollow cross-section.

In the heat bonded nonwoven, the staple fibers and the multi-component binder fibers may be present in different proportions. The ratio between the staple fibers and the multi-component binder fibers is typically given as a weight ratio in nonwovens.

The weight ratio between the staple fibers and the multi-component binder fibers may thus be in the range 8:1 to 1:2. However, the multi-component binder fibers are typically not the major component in the heat bonded nonwoven. The weight ratio between the staple fibers and the multi-component binder fibers may be in the range as 4:1 to 1:1.

As recognized by the skilled person, nonwovens comprising staple fibers and binder fibers are typically provided by mixing fibers and subsequently carding the mixed fibers into webs and subsequently bonding the fibers. Apart from arranging the fibers into a web, the carding also serves to at least partly arrange the fibers in a given direction within the web. Thus, the fibers may be arranged in the longitudinal extension of the web. Further, before bonding the web it may be further structured, such as cross- lapped or vertically lapped, to inter alia increase the thickness of the nonwoven.

However, lapping may also affect other properties of the resulting nonwoven. According to an embodiment, the present heat bonded nonwoven is vertically lapped. Vertically lapped nonwovens may e.g. be produced by machinery for vertical lapping nonwoven provided by V-Lap Pty Ltd, Hallam, Australia. The technology provided by V-Lap Pty Ltd represents a preferred technique. Alternative techniques for vertically lapped nonwovens are provided by inter alia Struto international Inc., Huntley, IL, USA, Aconic High Tech Fiber (Shenzhen) Co. Ltd. Guan Lan, China, and Shinih Enterprise Co. Ltd, Taoyuan City Taiwan. Furthermore, R.H. Gong have in Chapter 8 “Developments in 3D nonwovens", p. 183-205 of “Advances in 3D Textiles", edited by Xiaogang Chen, from 2015, described various lapping techniques. In a vertically lapped nonwoven, the fibers are arranged essentially perpendicular to the longitudinal extension of the nonwoven, whereby improving the cushion properties.

According to another aspect there is provided a cushion member comprising a heat bonded nonwoven. In a cushion member comprising a heat bonded nonwoven, the nonwoven may, at least partly, be covered by a fabric. A vertically lapped heat bonded nonwoven is especially useful in cushion members. As the fibers in a vertically lapped nonwoven are arranged essentially perpendicular to the longitudinal extension of the nonwoven, the comfort of the cushion member is improved. Further, the stiffness of the cushion member is improved. Arranging the fibers in this manner imply that the main load the cushion member is subjected to may be essentially parallel with the longitudinal extension of the fibers. Hence, each fiber may act as a spring subjected to buckling and not subjected to bending, as for a cross lapped nonwoven, and thereby improve the resilience and the stiffness. Examples of different cushion members are presented hereinafter.

Without being bound by any theory, the compressive behavior of a cross lapped nonwoven could be seen as being based, at least partly, on general beam bending theory (following the equation integral for the elastic line) and the same applies also for a VLAP material, although a VLAP material is stiffer than a cross-lapped nonwoven. Further, if the fibers of a VLAP would be essentially straight (i.e. not crimped or conjugated, or with a relatively low degree of crimping or conjugation) and vertically oriented in a VLAP, the initial deformation follows Eulers buckling theories in the beginning of the compression curve until the straight fibers have been bent under compression to a level that bending of each fiber becomes the case. Therefore, the compression curve of a VLAP with essentially straight bonding fibers is likely, in contrast to a compression curve of a VLAP with crimped or conjugated fibers, to be similar to a PU-foam compression curve (such PU-foam compression curve being a desired property of a cushion material), with the PU-foam compression curve typically illustrating a rather high stiffness initially, followed by a “plateau” before the stiffness increases rapidly again at the end of the compression curve (Figs. 7 and 12).

The present cushion member is useful in various applications in which it will be exposed to the human body applying pressure on the cushion member. Examples include furniture, apparel, underwear, sleeping bags etc. The cushion member has specific advantages in applications where a human body will often and repeatedly contact, directly or indirectly, the cushion member, causing a fatigue exposure to the cushion member. Therefore, the cushion member is particularly suitable for use in sitting furniture, armrests, mattresses and other furniture intended for laying, sitting and/or resting, etc. According to an embodiment, the cushion member is a furniture cushion member. In particular, a furniture cushion member may be a furniture cushion member onto which a human body may rest, such as the cushion member being a fatigue exposed furniture cushion member. Thus, the cushion member may be used in upholstered furniture or parts thereof, such as in chair pads, arm rests, upholstered chairs (seat and/or back), or mattresses. The cushion member may further be used in other types of upholstered furniture, such as sofas, bed sofas, daybeds, headboards for beds, and upholstered bed frames.

Although the present invention has been described above with reference to specific embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the invention is limited only by the accompanying claims and other embodiments than the specific embodiments described above are equally possible within the scope of these appended claims.

In the claims, the term " compri ses/ compri sing" does not exclude the presence of other elements or steps. Additionally, although individual features may be included in different claims, these may possibly advantageously be combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous.

In addition, singular references do not exclude a plurality. The terms "a", "an", “first”, “second” etc. do not preclude a plurality.

Brief description of the drawings

These and other aspects, features and advantages of which the invention is capable of will be apparent and elucidated from the following description of embodiments of the present invention, reference being made to the accompanying drawings, in which: Fig. 1 Shows a SEM (Scanning electron microscopy) image of the cross- section of the binder fiber used in prior art;

Fig. 2 Shows an optical microscope image of the binder fiber used in prior art showing its mechanically crimps (the crimp frequency according to ASTM D 3937-01, preparation option 9.2.1, is 9 crimps/25 mm);

Figs. 3a-3b Show optical microscope images of the present binder fiber according to different embodiments. In Fig. 3a the volume ratio of sheath: core is 50/50, whereas the volume ratio of sheath: core in Fig.3b is 30/70.

Fig. 4a Shows a SEM (Scanning electron microscopy) image of a heat bonded nonwoven according to an embodiment. The heat bonded nonwoven comprises staple fibers and binder fibers;

Fig. 4b Shows a photograph of a test specimen of a heat bonded nonwoven according to an embodiment, the test specimen is about 40 mm thick.

Fig. 5 Shows the pressure distribution test data for cushion member according to an embodiment;

Fig. 6 Shows a corresponding pressure distribution as for Fig. 5, but for a cushion member according to the prior art;

Fig. 7 Shows a plot of load vs deformation for cushion member according to an embodiment before and after fatigues testing as well as corresponding data for a cushion member according to the prior art;

Fig. 8 Shows the pressure distribution test data for a virgin cushion member according to an embodiment;

Fig. 9 Shows a corresponding pressure distribution as for Fig. 8, but for a cushion member according to the prior art; Fig. 10 Shows the pressure distribution test data for the cushion member in

Fig. 8 after fatigue testing;

Fig. 11 Shows the pressure distribution test data for the cushion member in Fig. 9 after fatigue testing;

Fig. 12 Shows a plot of load vs deformation for a cushion member according to an embodiment before and after fatigues testing as well as corresponding data for a cushion member according to the prior art. Experimental

Material in vertically lapped nonwoven, according to an embodiment of the present invention

Binder fiber Sheath: Hytrel HTR 6108, a thermoplastic polyester elastomer from

DuPont

Core: i) PBT-core: Ultradur B4500, a high molecular weight PBT from BASF, Schwarzheide, Germany), or ii) PET-core: RAMAPET N180, a recycled PET from Indorama, Kells, Ireland

Binder fiber design: Non-crimped, concentric core-sheath binder fiber with 50 wt.%

PBT-core or PET-core (8.8 dtex, 51 mm long staple fibers)

Staple fiber Conjugated hollow three-dimensional crimp staple polyester fiber (non-siliconized) from Huvis, Zigong, China, (7.8 dtex, 64 mm long)

Reference material with Teijin elk ^® a polyester (PBT or PET) elastomer bi-component fiber Binder fiber: elk® from Teijin Polyester Ltd, Klong Nueng, Thailand

(eccentric side-by-side binder fiber) with 50 volyme% PBT-core or PET-core (6.6 denier, 51 mm long staple fibers)

Staple fiber: same as above (i.e. Conjugated hollow three-dimensional crimp staple polyester fiber (non-siliconized) from Huvis)

Multi-component binder fiber

The novel binder fiber was produced in a small-scale fiber spinning machine manufactured by Hills, Inc. West Melbourne, FI., USA. using a bi-component, core sheath spinneret. Processing parameters were adjusted to get a well working, continuous process. After final drawing, the fibers were relaxed at elevated temperature to reduce their shrinkage. Since the fiber’s cross section was concentric and fully symmetric (cf. Figs. 3a-b), no tendency of self-crimping could be observed. The spin finish used was not washed off, and no mechanical crimp process was added, hence the binder fibers were straight without any type of crimp. The resulting binder fiber used in the testing described below comprised 50 volume% (fibers with 30 volume% sheath polymer were also produced; cf. Fig. 3b) of the sheath polymer (i.e. Hytrel HTR 6108) and its linear density was 8.8 dtex. Fibers with PET- and PBT-core, respectively, were produced.

The resulting filaments were cut into 51 mm long binder fibers (same length as the elk® fibers from Teijin)

Nonwoven

The binder fiber (elk and the one described herein above, respectively) and staple fiber (weight ratio binder fiber: staple fiber 35:65) was evenly distributed on a conveyor belt and feed into a standard type of blending machine, thereafter forwarded to the carding line where the fibers were carded to a web with good homogeneity, vertically lapped by a machine from V-Lap Pty Ltd, and thermo-bonded at 190°C in a through air hot-air double belt oven to provide test cushion members.

The following cushion members were produced: Sample 1 (PET core, Hytrel sheet - core: sheet ratio 50:50 (volumewolume);

Huvis staple fiber)

Sample 2 (PBT core, Hytrel sheet - core: sheet ratio 50:50 (volumewolume); Huvis staple fiber)

Comparative sample 1 (elk binder fiber (PET core); Huvis staple fiber) Comparative sample 2 (elk binder fiber (PBT core); Huvis staple fiber)

In a further example, the core of the binder fibers was colored black using carbon black to confirm that they could be evenly distributed among the staple fibers.

As can be seen from Fig. 4b, illustrating a quite even grey-scale color, the straight binder fibers were evenly distributed among the staple fibers. As the binder fibers, contrary to elk (cf. Fig. 2), was not crimped or conjugated this was actually quite surprising. According to the common belief, staple fibers need to be crimped and/or conjugated in order to be efficiently mixed and intertangled in the carding thereof. As conjugation and crimping is not necessary with these binder fibers, the binder fibers are easy to produce in an efficient manner.

Testing

The produced V-Lap cushion members were thereafter measured and tested with respect to mechanical properties, including pressure distribution tests. Further, also the binder fibers as such were evaluated. Most of the properties of the invented fibers were similar to the ones of elk fibers. However, compressive stiffness was higher for a V-Lap cushion member comprising the inventive fibers. Importantly, the V-Lap cushion member comprising the invented fibers had significantly lower maximum surface pressure; especially after fatiguing testing, as can be seen below.

Pressure distribution testing

Measurement of pressure distribution in the contact area between a test person (79 kg, 184 cm length) and two different cushion members (targeted thickness 40 mm), Sample 1 and Comparative sample 1, both comprising a binder fiber with a PET core, were performed. The pressure sensor used was an Xsensor LX21040x40, calibrated in conjunction with the measurements.

In Fig. 5 and 6, the pressure distribution over the Xsensor LX210 is shown. As indicated in Fig. 6 (cf. arrows), a tendency of bottoming out was observed with the reference cushion member (i.e. Comparative sample 1), but not with the inventive cushion member (i.e. Sample 1) despite a significant lower surface weight.

Three pressure measurements per cushion member were conducted, and the respective average maximum pressure values determined (the maximum pressure was defined as the average of the 10 highest pressure values from the individual pressure sensors of the sensor matt) is reported in Table 1 below. A low maximum pressure is desirable from a comfort perspective.

Table 1 - Cushion member (binder fiber with PET core) and the measured average ^' n=3) maximum pressure*

* Different samples were used in testing pressure before and after fatigue testing

Further, compression data for the materials is shown in Fig. 7. This data is in line with the pressure distribution data in Fig. 5 and 6. As can be seen from Table 1, despite 10% higher surface weight and thickness, the virgin cushion member with commercial fibers (cf. Comparative sample 1) had about 40% higher maximum surface pressure compared to the virgin cushion member with the inventive fibers (cf. Sample 1). In another comparison, the virgin cushion member with the commercial fiber (cf. Comparative sample 1) had about 20% higher maximum surface pressure after subjected to an 80.000 cycle fatigue test, despite the cushion member comprising the inventive fibers (cf. Sample 1) having 20% lower surface weight and being 15% thinner. Other relevant parameters such as bonding fiber ratio, carding parameters and oven parameters were kept the same. Corresponding pressure distribution testing was performed for cushion members (cf. Sample 2 and Comparative sample 2) comprising a binder fiber with PBT-core as well (cf. Table 2). In Fig. 8 and 9, the pressure distribution over the Xsensor LX210 for virgin cushion members is shown. In Fig. 10 and 11, the pressure distribution over the Xsensor LX210 for fatigued (cf. above) cushion members is shown. Compression data for the cushion members is shown in Fig. 12. As recognized by the skilled person, there is a correlation between the stiffness of the material and the pressure distribution, but the correlation is complex. Generally, high initial stiffness (first 10-25% deformation), followed by a lower stiffness at medium compression, and then rapidly increasing stiffness at the end of the compression curve is a preferred property of a cushion member.

Table 2 - Cushion member (binder fiber with PBT core) and the measured average n=3) maximum pressure*

* Different samples were used in testing pressure before and after fatigue testing For virgin cushion members (cf. Comparative sample 2 and Sample 2), pressure distribution was similar. Further, the softer PBT core provided somewhat less efficient pressure distribution in cushion members comprising the inventive fibers (cf. Sample 2). However, whereas the pressure distribution remained essentially the same for the cushion members comprising the inventive fibers (cf. Sample 2), the pressure distribution for elk (cf. Comparative sample 2) after fatigue testing (80.000 cycles) was inferior, as can be seen in Fig. 11 and Table 2 and an obvious tendency of bottoming out was observed (cf. arrows).