GB2576377A

GB2576377A - Sheet material

Info

Publication number: GB2576377A
Application number: GB1813469.2A
Authority: GB
Inventors: Miles Cassingham Darryl; Lewis Nicholls John
Original assignee: Joryl Logic Ltd
Current assignee: Joryl Logic Ltd
Priority date: 2018-08-17
Filing date: 2018-08-17
Publication date: 2020-02-19
Also published as: WO2020035621A1; GB201813469D0

Abstract

A sheet material including inherently flame-retardant fibres entangled with tanned collagen fibres. The tanned collagen fibres may be natural tanned collagen fibres derived from animal leather. Also disclosed is a process for producing a sheet material, the process comprising providing tanned collagen fibres, providing inherently flame-retardant fibres, and entangling the tanned collagen fibres and flame-retardant fibres to form a fibre mixture. Optionally, a binder may be added, and the sheet material may be embossed. The process may further comprise providing one or more tanned leather pieces and defibrillating the tanned leather pieces to form the tanned collagen fibres. Entangling the tanned collagen fibres and flame-retardant fibres may be by spun-lacing, hydroentanglement, or air entanglement. An especially preferred flame-retardant fibre is polbenzimidazole (PBI).

Description

Sheet Material

The present invention relates to sheet materials and processes for producing such sheet materials. More particularly, the present invention relates to flame retardant sheet materials containing tanned collagen; the sheet materials may be used as leather-based materials.

A great deal of waste leather is produced annually by the leather industry. Waste leather may derive from animal hides with imperfections and from leather off-cuts.

Natural leather and other materials may be used in transport applications to cover seating and other internal parts of ground, air and water vehicle cabins. The requirements for such applications include good mechanical properties, good flame-retardant properties and, especially for relatively high value vehicles, good softness and hand-feel.

It is known to produce imitation or synthetic leather from polymer materials that can be embossed and made to look like natural leather. Such synthetic materials however do not have the fibrous structure, or hand-feel, of natural leather nor other beneficial properties such as tensile strength and elasticity. Flame retardants may be added to such materials, but fire and flame-retardant properties can nevertheless be problematic.

There have been attempts to use off-cuts and waste leather to form leather-based materials with similar appearance and hand-feel to natural leather.

CN-A-103 233 324 discloses a low-cost collagen fibre reconstituted leather. The reconstituted leather comprises the following ingredients in percentage by weight: collagen fibre 85 - 99% and viscose fibre 1 - 15%.

CN-A-103 233 321 discloses spun-laced collagen fibre bonded leather as well as a manufacturing method and a spun-lace device.

CN-A-103 276 531 discloses a low-cost collagen fibre regenerated hide and a method of manufacturing the same. The regenerated hide consists of a double-layered web in which one layer of the web contains up to 100% by weight of a low-cost viscose fibre and the other layer is composed of collagen fibres.

WO-A-01/94673 discloses an artificial leather sheet material made by hydroentanglement of waste leather fibres.

WO-A-2005/118932 discloses a development of the materials of WO 01/94673 of leather sheet material made by hydroentangling a web of mixed reclaimed leather fibres and synthetic fibres of a meltable bicomponent material which are heated prior to entanglement to fuse and form a supporting network. During manufacture, a sheet of tissue paper is laid over the surface of the leather fibre web and hydroentanglement jets.

Flame retardant requirements are becoming more stringent and, unfortunately, there can be problems of delamination and adhesion failure in known materials. There is, therefore, a need for improved leather-based materials with good mechanical properties, good flame-retardant properties, long life and good softness and hand-feel.

It is an aim of the present invention to address this need.

The present invention accordingly provides, in a first aspect, a sheet material comprising inherently flame-retardant fibres entangled with tanned collagen fibres.

The materials preferably further comprise a binder, preferably a resinous binder. Example of suitable binders include vinyl copolymers, vinyl-styrene, melamineformaldehyde, polyurethane (PU) and/or acrylic binders. To provide enhanced flame retardant (FR) properties, the binder may comprise halogen (i.e. be halogenated) or another flame-retardant component. The binder may be solvent- or aqueous-based. The binder may contain cross-linking moieties e.g. isocyanates, carbodiimides, aziridines, polyurea, or others.

Generally, the weight percentage of flame-retardant fibres in the material may be in the range 1% to 60%, preferably in the range 1% to 40%, more preferably in the range 1% to 30% and most preferably in the range 1% to 20%. The lower end of the range may be 2%, 3%, 4%, or 5%. Thus, the weight percentage of flame-retardant fibres in the material may be in the range 2% to 60%, preferably in the range 3% to 40%, more preferably in the range 4% to 30% and most preferably in the range 5% to 20%.

Generally, the weight percentage of tanned collagen fibres in the material may be in the range 15% to 95%, preferably in the range 40% to 95% (other ranges may be 45% to 95%, or 43% to 93%), more preferably in the range 70% to 95% and most preferably in the range 80% to 95%.

The inherently flame-retardant fibres may have been treated before incorporation in the sheet material and/or may be composed of flame retardant materials, in particular inherently flame-retardant materials. The flame-retardant fibres may comprise an inorganic material, a flame-retardant treated natural fibre, and/or a flame-retardant polymer.

Examples of flame-retardant fibres may comprise a material selected from one or more of glass, carbon, silicon carbide, elongated carbonaceous Dow™ fibre (EDF), carbonised viscose or acrylic fibres (e.g. Panox ™ generated through thermo-oxidative stabilisation of viscose or acrylic fibres), modacrylic (e.g. Kanecaron™ or Protex™), Zeroxy™, Lastan™ (an oxidised acrylic based fibre), flame retardant treated wool (e.g. wool fibre treated by the ZIRPRO™ process), Proban™ treated cotton fibres, fungal mycelium-derived fibres, novoloid fibres (phenolic fibres, e.g. Kynol™), oxidised poly(aciylonitrile) fibre (OPF), polyhydroquinone-diimidazopyridine (PIPD), aramid (para- or meta-), polybenzimidazole (PBI), polyphenylenebenzobisozazole (PBO), polyimide, polyphenylene sulfide (PPS, e.g. Procon™), melamine, polytetrafluoroethylene (PTFE), poly(ether-etherketone) (PEEK), phenolic fibre, polyamide-imide (PAI), copolymer p-aramid fibre, poly(m-phenylene isophthal-amide) (PMIA), and poly(p-phenylene terephthal-amide) (PPTA).

The flame-retardant fibres may have a length in the range 100 pm to 10 cm, preferably in the range 500 pm to 6 cm, more preferably in the range 1 mm to 4 cm. Staple fibres may be 20 to 35 mm in length.

Preferably, the tanned collagen fibres are natural collagen fibres derived from animal leather. Natural collagen may include collagen from animal sources (for example bovine, porcine, ovine, caprine and/or kangaroo animal sources), and/or collagen that can be extracted from waste leather materials. As used in this specification, the term “collagen” includes modified collagens and collagen-like proteins.

Generally, the tanned collagen fibres may have a length in the range 50 gm to 8 cm, preferably in the range 100 gm to 5 cm, more preferably in the range 500 gm to 5 cm, most preferably in the range 1000 gm to 3 cm.

Generally, the tanned collagen fibres may have a width in the range 0.1 gm to 2000 gm, preferably in the range 1 gm to 500 gm, more preferably in the range 10 gm to 50 gm.

Sizes may refer to size (e.g. width and/or length) determined by microscope, by hydrodynamic methods or by coagulation methods.

In some embodiments, the material may comprise at least two layers. The layers may differ in weight percentage of collagen fibres. For example, a first layer may have collagen at 95% by weight to give hand-feel essentially indistinguishable from natural leather and a second layer at 50% by weight to provide for more flame-retardant fibres and/or polymer fibres.

Generally, the material may further comprise fat liquor. Preferably, the fat liquor may be a flame-retardant fat liquor or flame-retardant lubricant, preferably comprising a siloxane-base lubricant or halogenated fat liquor. The use of fat liquor may be advantageous so that the collagen fibres have their bound water replaced with a lubricant as they dry, to reduce or prevent the fibres sticking together and maintain flexibility. Halogenated fat liquors (e.g. Truposol FRF from Trumpler GmbH) and siloxane-based lubricants (e.g. Densodrin CD, BASF) may improve flame retardant properties.

The sheet material may comprise surfactants (e.g. cationic or anionic or amphiphilic) and/or other lubricants.

The materials may also include other additives to modify properties of the materials. Such additives may include, but are not limited to fragrances, dyes and/or pigments.

To still further improve flame-retardancy, the material may further comprise a flame-retardant composition comprising a particulate material selected from one or more of aluminium trihydrate, magnesium hydroxide, huntite, hydromagnesite, vermiculite, ammonium polyphosphate, organically modified phyllosilicate (e.g. Cloisite™), and expanded graphite.

The sheet material may also include particles intended to provide porosity.

The sheet material may, in some circumstances, further comprise additive polymer fibres selected from polyester, viscose, polyalkene (e.g. polyethylene and/or polypropylene), and polyamide. The additive polymer fibres may be optionally present in an amount in the range lwt% to 25wt%. The preferred polymer fibres comprise polyester.

The sheet material may further comprise one or more web layers comprising a thermoplastic polymer. The web layer may be on one of the surfaces of the sheet material and/or may be a web layer disposed between two layers of the sheet material. The web may be of relatively open structure (e.g. a scrim) to aid entangling through the web.

To improve the appearance of the sheet material, the sheet material may be embossed. Embossing the sheet material would usually involve forming a coating on the surface of the sheet material and embossing the surface of the coating. Alternately, the sheet material may comprise a coating that has been pre-embossed using an embossed release paper.

The area density of the sheet material may be 20 g/m² to 3500 g/m², preferably 20 g/m² to 1500 g/m², more preferably 200 g/m² to 700 g/m².

Sheet materials according to the invention may be made by entangling processes.

Thus, in a second aspect, the present invention accordingly provides, a process for producing a sheet material, the process comprising: a) providing tanned collagen fibres, b) providing inherently flame-retardant fibres, and c) entangling the tanned collagen fibres and flame-retardant fibres to form a fibre mixture, and d) optionally adding a binder.

Providing collagen fibres may comprise providing one or more leather pieces and defibrillating the leather pieces to form tanned collagen fibres.

The process may further comprise e) forming a layer of a sheet material from the fibre mixture.

If present, the process may further comprise curing the binder (e.g. by drying, UV curing, radiation curing, depending on the nature of the binder).

The process may comprise needle punching the sheet material to increase porosity.

In a third aspect, the present invention provides, a process for producing a sheet material, the process comprising: a) providing one or more tanned leather pieces, b) defibrillating the leather pieces to form tanned collagen fibres, c) providing inherently flame-retardant fibres, d) entangling the tanned collagen fibres and flame-retardant fibres to form a fibre mixture, and e) forming a layer from the fibre mixture, thereby forming the sheet material. One or more further layer may be formed on the sheet material if desired.

Entangling the collagen fibres and flame-retardant fibres is preferably by a process selected from spun-lacing, hydroentanglement, and air entanglement.

The preferred method of entangling the collagen fibres and flame-retardant fibres is hydroentanglement performed using high pressure waterjets. The waterjets may be 80 to 250 pm diameter hydroentangling jets at 0.2 to 1.9 mm apertures and pressure of 12 MPa (120 bar) to 70 MPa (200 bar), usually up to 30 MPa.

In a fourth aspect, the present invention provides, a leather-based material formed by the process of the second or third aspects.

Embodiments of the present invention will now be described with reference to the following figures, in which:

Figure 1 shows micrographs of (a) 95% (by weight) collagen fibres entangled with 5% (by weight) polyester fibres, (b) 85% (by weight) collagen fibres entangled with 15% (by weight) polyester fibres, and (c) 85% (by weight) collagen fibres entangled with 15% (by weight) polyester fibres with an automotive type re-tan and finish.

Figure 2 shows micrographs of the top layer of the samples as in Figure 1 (a) and (b).

Figure 3 shows micrographs of the bottom layer of the samples as in Figure 1.

The materials have high tensile strength including meeting the requirements in terms of the force to break on elongation for items such as a footwear and seating.

The present invention is further illustrated by the following examples.

Examples Method A (using only fibres)

a. Weighing: raw staple tanned collagen fibres (one or more types of fibres may be used in order to provide the desired physical attributes of the finished product). Weighed amounts of fibres are provided in an amount to provide a finished material with area density 20 g/m² to 1500 g/m² (or higher if required). A density of 500 g/m² is typically used for many purposes. In some embodiments, two or more layers may be prepared, with each layer having a different area density, the overall density will preferably be in the range indicated above by laying the webs of fibres in different densities on top of each other. Inherently fire-retardant fibres for use in the invention are fibres that are made of a fire-retardant material, have been treated with a fire-retardant composition and/or have undergone a process to render them fire retardant before use in the invention. PBI is a particularly suitable flame-retardant fibre for use in the invention.

b. Blending: After the tanned collagen and FR fibres are weighed, they are blended.

c. Opening: the blended fibres are carried by a belt to a hopper to fluff and open the material and blend further.

d. Carding: the blend fibres are carded. Carding machines contain cylinders wrapped with fine metal pins and teeth that are used to stretch and comb the fibres. Carding is advantageous in the invention because it combs, opens, and aligns the fibres, removing hard clumps and creating a uniform, soft and fluffy web. After carding, the carded blend is formed into a web and wet laid or air laid onto a belt to be carried to the entangling stage. If two or more layers are to be formed, the different webs to form the different layers may be laid on top of one another at this stage. The air-laid or wet-laid web is compressed and then pre-wetted to remove air pockets before the hydroentangling process.

e. Hydroentangling: High-pressure waterjets are applied to the web of fibres, entangling them together to form a non-woven fabric and providing strength and integrity to the wet-laid or air-laid carded web of fibres from the previous operation. The water pressure usually increases from the first to the last waterjet injectors. The pressure is typically 2200 psi (15 MPa), used to direct the waterjets on top of the web, but can be as high as 10,000 psi (69 MPa). The high-pressure jet of water entangles the fibres in the web. The jets’ kinetic energy is primarily used in rearranging fibres inside the web, and secondly, during bounce back against the substrates, dissipating energy to the fibres. A vacuum inside the roller (typically 500 mbar (50 kPa) or greater) removes used water from the product, avoiding flooding of the product and consequently maintaining the effectiveness of the jets to move the fibres & cause entanglement. Hydro-entanglement may be performed on both sides of the web in a stepwise approach. If required, the first entanglement roll may be subjected to further hydroentanglement as necessary, to generate the desired amount of interwoven bonding and strength. The material may also pass over a second entanglement roller in an overturned direction in order to treat and, thereby, consolidate the other side of the fabric. Furthermore, additional webs of fibres can be hydroentangled on top of the initial hydroentangled material in order to build up thickness.

f. Smoothing: The non-woven material may be finally subjected to a series of water jets at a much lower pressure (such as a pressure of 750 psi (5 MPa)) in order to smooth out the surface of the material from any irregular surface aspects caused through the higher-pressure waterjets.

g. Drying: After hydroentanglement, the newly formed non-woven composite fabric is dewatered typically through a pressing system to reduce the moisture content to 10 50wt% and further dried by being pulled over large drying cans or routed through a tunnel dryer to remove excess water and moisture before being wound into a large roll. The drying stage can be completed at temperatures ranging from 40 °C to 100 °C, typically at 70 °C for 3-12 minutes.

Method B (using binder)

a) As a modification to Method A above, the non-woven material can be provided with increased strength using a binder, usually in the form of a resin. This may be accomplished by passing the roll of material through a roller coater applying a resin (e.g. aqueous or solvent based). The resin may be curable (e.g. an isocyanate, carbodiimide, aziridine, polyurea, etc resin). Once the resin has sufficiently penetrated the roll, it may be cured (e.g. by air drying, heat drying, UV curing, radiation curing, etc). The properties of the resin, in particular the tensile strength at specific elongation values, can determine the degree of softness. For example, resins tested at 100% elongation: Resin A having a tensile strength of 5 MPa and Resin B having a tensile strength of 0.8 MPa; Resin B will have a softer handle than Resin A. Usually, a flame-retardant based resin may be used, such as a halogenated polyurethane (PU) type or an ethylene vinyl-chloride copolymer.

b) A typical process would be as involve the roll of nonwoven being fed to a roller coater that applies 50 g/m² of an aqueous PU resin that is allowed to penetrate through the roll. Subsequently, the web is dried at 80 °C through a tunnel dryer for 60 seconds. After drying, the roll would be rewound.

Method C (coating)

a) The sheet material produced according to the above methods A and B may be coated. Because of the advantageous properties of the sheet material, traditional leather coating techniques may be used or to transfer type coating systems. With transfer type systems in particular care has to be used to ensure that the coating does not subsequently de-laminate, especially if the coating adhesive layer does not penetrate nor react well enough to give high adhesion values over time. The preferred method is therefore as follows:

a. The sheet material is passed through a roller coater to apply an adhesion coat at an application level of 80 g/m², before being dried at 80 °C for 90 seconds. The sheet material is then again passed through a roller coater to apply a coloured basecoat at an application of 120 g/m² before being dried at 80 °C for 120 seconds. Finally, the process is repeated with a colourless topcoat at an application of 40 g/m² before being dried at 80 °C for 60 seconds. After coating, the sheet material may be embossed by passing through a rotopress having an engraved cylinder with an appropriate pattern at 80 °C to impart a permanent texture to the material.

The coating materials compositions may be as follows:

1) Adhesion coat: 10 parts of levelling agent (e.g. DRL 1261 from Dr Leather Ltd), 43 parts of water, 30 parts of Butyl Icinol (2-butoxyethanol), 9.5 parts of adhesion promoter (e.g. DRL 506 from Dr Leather Ltd), 7 parts of a PU binder (e.g. RU3961 from Stahl) and 0.5 parts of isocyanate crosslinker (e.g. Astacin Hardener CI from BASF)

2) Coloured Basecoat: 65 parts Compact basecoat formulation (NLC Ltd), 30 parts pigment (e.g. PP-39-lxx range of pigments from Stahl) and 5 parts of isocyanate crosslinker (e.g. Astacin Hardener CI from BASF)

3) Topcoat: 94 parts Compact topcoat formulation (NLC Ltd) and 6 parts of isocyanate crosslinker (e.g. Astacin Hardener CI from BASF)

In each of the methods, particulates may be added either in the coatings stage or during the hydroentanglement process.

Sheet materials according to the invention achieve flame retardancy according to the following test:

Aviation flame retardant (FR) tests include: a. Flammability - CS25.853 (a) Arndt 18 App.F Pt.I(a)(l)(ii) & (b)(4) 12 second edge test (Vertical); b. Heat Release - CS25.853 (d) Arndt 18 App.F Pt IV (e) & (g); c. Smoke Emission - CS25.853 (d) Arndt 18 App.F Pt V (a) & (b)

Train flame retardant (FR) tests include BS 6853: 1999, in which BS476-7 and Annex B and annex D.

Claims

1. A sheet material comprising inherently flame-retardant fibres entangled with tanned collagen fibres.

2. A sheet material as claimed in claim 1, further comprising a binder, preferably a resinous binder.

3. A sheet material as claimed in either claim 1 or claim 2, wherein the weight percentage of flame-retardant fibres in the material is in the range 1% to 60%, preferably in the range 1% to 40%, more preferably in the range 1% to 30% and most preferably in the range 1% to 20%.

4. A sheet material as claimed in any one of the preceding claims, wherein the weight percentage of tanned collagen fibres in the material is in the range 15% to 95%, preferably in the range 40% to 95%, more preferably in the range 70% to 95% and most preferably in the range 80% to 95%.

5. A sheet material as claimed in any one of the preceding claims, wherein the flameretardant fibres comprise an inorganic material, a flame-retardant treated natural fibre (treated or untreated), and/or a flame-retardant polymer.

6. A sheet material as claimed in claim 5, wherein the flame-retardant fibres comprise a material selected from one or more of glass, carbon, silicon carbide, elongated carbonaceous Dow™ fibre (EDF), carbonised acrylic fibres, modacrylic, Zeroxy™, Lastan™, flame retardant treated wool, Proban™ treated cotton fibres, fungal myceliumderived fibres, novoloid fibres, oxidised poly(acrylonitrile) fibre (OPF), polyhydroquinone-diimidazopyridine (PIPD), aramid (para- or meta-), polybenzimidazole (PBI), polyphenylenebenzobisozazole (PBO), polyimide, polyphenylene sulfide (PPS), melamine, polytetrafluoroethylene (PTFE), poly(ether-etherketone) (PEEK), phenolic fibre, polyamide-imide (PAI), copolymer p-aramid fibre, poly(m-phenylene isophthalamide) (PMIA), and poly(p-phenylene terephthal-amide) (PPTA).

7. A sheet material as claimed in any one of the preceding claims, wherein the flameretardant fibres have a length in the range 100 pm to 10 cm, preferably in the range 500 pm to 6 cm, more preferably in the range 1 mm to 4 cm.

8. A sheet material as claimed in any one of the preceding claims, wherein the flameretardant fibres have a width in the range 0.1 pm to 2000 pm, preferably in the range 1 pm to 500 pm, more preferably in the range 10 pm to 50 pm.

9. A sheet material as claimed in any one of the preceding claims, wherein the tanned collagen fibres are natural tanned collagen fibres derived from animal leather.

10. A sheet material as claimed in any one of the preceding claims, wherein the tanned collagen fibres have a length in the range 50 pm to 8 cm, preferably in the range 100 pm to 5 cm, more preferably in the range 500 pm to 5 cm, most preferably in the range 1000 pm to 3 cm.

11. A sheet material as claimed in any one of the preceding claims, wherein the tanned collagen fibres have a width in the range 0.1 pm to 2000 pm, preferably in the range 1 pm to 500 pm, more preferably in the range 10 pm to 50 pm.

12. A sheet material as claimed in any one of the preceding claims, wherein the material comprises at least two layers, the layers differing in weight percentage of tanned collagen fibres.

13. A sheet material as claimed in any one of the preceding claims, further comprising fat liquor, optionally wherein the fat liquor is a flame-retardant fat liquor or flameretardant lubricant, preferably comprising a siloxane-base lubricant or halogenated fat liquor.

14. A sheet material as claimed in any one of the preceding claims, further comprising a flame-retardant composition comprising a particulate material selected from one or more of aluminium trihydrate, magnesium hydroxide, huntite, hydromagnesite, vermiculite, ammonium polyphosphate, organically modified phyllosilicate (e.g. Cloisite™), and expanded graphite.

15. A sheet material as claimed in any one of the preceding claims, further comprising additive polymer fibres selected from polyester, viscose, polyalkene (e.g. polyethylene and/or polypropylene), polyamide, the additive polymer fibres being optionally present in an amount in the range lwt% to 25wt%.

16. A sheet material as claimed in any one of the preceding claims, further comprising a web layer comprising a thermoplastic polymer.

17. A sheet material as claimed in any one of the preceding claims, wherein the sheet material is embossed.

18. A process for producing a sheet material, the process comprising:

a) providing tanned collagen fibres,

b) providing inherently flame-retardant fibres,

c) entangling the tanned collagen fibres and flame-retardant fibres to form a fibre mixture, and

d) optionally, adding a binder.

19. A process as claimed in claim 18, wherein providing tanned collagen fibres comprises providing one or more leather pieces and defibrillating the leather pieces to form tanned collagen fibres.

20. A process as claimed in either claim 18 or claim 19, wherein the process involves forming a layer of a sheet material from the fibre mixture.

21. A process as claimed in any one of claim 18 to 20, further comprising curing the binder.

22. A process for producing a sheet material, the process comprising:

a) providing one or more tanned leather pieces,

b) defibrillating the tanned leather pieces to form tanned collagen fibres

c) providing inherently flame-retardant fibres,

d) entangling the tanned collagen fibres and flame-retardant fibres to form a fibre mixture,

e) thereby forming at least one layer of the sheet material.

23. A process as claimed in any one of claims 18 to 22, wherein entangling the tanned collagen fibres and flame-retardant fibres is by a process using air and/or waterjets and may be selected from spunlacing, hydroentanglement, and air entanglement.

5

24. A process as claimed in any one of claims 18 to 23, wherein entangling the tanned collagen fibres and flame-retardant fibres is hydroentanglement performed using high pressure waterjets.

25. A process as claimed in any one of claims 18 to 24, further comprising coating

10 and optionally embossing the sheet material.