Flame-retardant lyocell fibers and use thereof in flame barriers

Abstract

The present invention relates to flame-retardant Lyocell fibers which include incorporated inorganic additives which are particularly suited for use in flame barriers for articles of manufacture, such as mattresses and upholstered furniture applications.

Claims

1. A flame barrier comprising a fiber blend comprising: a. about 20% (w/w) to less than about 70% (w/w) of flame-retardant Lyocell fibers, wherein said Lyocell fibers comprise from about 12% to about 50% (w/w) of incorporated inorganic additives selected from the group consisting of kaolin, talc, and mixtures thereof, b. at least one fiber selected from the group consisting of natural and synthetic fibers, wherein said fiber blend is capable of imparting to an article of manufacture the ability to pass a test according to 16 CFR 1633; and wherein said flame barrier is capable of forming a stable charred layer when exposed to a flame.

2. The flame barrier according to claim 1, comprising from about 30% (w/w) to about 70% (w/w) of the flame retardant Lyocell fibers.

3. The flame barrier according to claim 1 or 2, wherein the flame barrier comprises a nonwoven material.

4. The flame barrier according to claim 3, wherein the nonwoven material is a high loft nonwoven material.

5. An article of manufacture comprising a flame barrier which comprises a fiber blend comprising: a. about 20% (w/w) to about 70% (w/w) of flame-retardant Lyocell fibers which comprise from about 12% to about 50% (w/w) of incorporated inorganic additives selected from the group consisting of kaolin, talc, and mixtures thereof, b. at least one fiber selected from the group consisting of natural and synthetic fibers, wherein the article of manufacture is capable of passing a test according to 16 C.F.R. 1633; and wherein the flame barrier is capable of forming a stable charred layer when exposed to a flame.

6. The article of manufacture according to claim 5, wherein said article of manufacture is selected from the group consisting of mattresses, upholstered furniture, cars, airplanes, and carpets.

7. The article of manufacture according to claim 6, wherein said article of manufacture is a mattress.

8. The flame barrier according to claim 1, wherein the flame barrier is for use in an article of manufacture selected from the group consisting of mattresses and upholstered furniture.

9. The flame barrier according to claim 1, wherein the natural and synthetic fibers are selected from the group consisting of cotton and PES.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) The excellent flame-retardant properties of the preferred kaolin-incorporated Lyocell fibers for use as flame barrier in the test 16 CFR 1633 may be tentatively explained as follows: The essential point which makes fibers suitable as flame barrier in the test above seems to be the ability to form after action of a flame a carbonaceous stable, heat insulating layer which prevents the breaking open and loss of the integrity of the mattress. The idea that it is really the ability to form a stable charred layer which retains some strength after being exposed to flame and not a general flame-retardant effect is supported by the surprising fact that a Lyocell fiber containing a known flame-retardant aluminum hydroxide does not pass 16 CFR 1633 (as shown in the examples). Also another known filler, calcium carbonate, incorporated in Lyocell fibers, does not pass 16 CFR 1633 showing the surprising difference to kaolin in passing/not passing the test. The flame barrier must be impermeable such that heat and hot gases cannot be transmitted through the fabric causing internal materials to ignite.

(2) The fiber of the present invention is a fiber of the Lyocell type, the designation of the fiber adopted by the CIRFS (the European man-made fibers association) for cellulosic fibers produced by the direct solvent process. The solvent for the fiber of the present invention may be N-methylmorpholine-N-oxide (NMMO) or alternatively a ionic liquid known to dissolve cellulose as e.g. 1-ethyl-3-methyl-imidazolium chloride or -acetate or 1-butyl-3-methyl-imidazolium chloride or -acetate. Fibers produced with the solvent NMMO are commercially produced under the brand Tencel. Preferably the fiber is produced by the NMMO-process.

(3) The kaolin used in the present invention is preferably of high purity (especially heavy metal content) and have a particle size sufficiently low not to disturb the spinning process, preferred types are those used for paper coating as e.g. Miragloss by BASF or Hydragloss by KaMin LLC. In the production process of the Lyocell fiber the kaolin may be added either to the slurry of cellulose and aqueous NMMO or added to the spinning dope as powder or in a suitable dispersion. The Lyocell-dope containing the kaolin additive is then spun to fibers in a dry-wet spinning process according to EP 0584318 B1.

(4) The fiber according to the present invention preferably contains between 12% kaolin and 50% kaolin in fiber, preferably between 20% and 30% in fiber. Fibers containing less than 12% kaolin in fiber show reduced flame-retardant effect in flame barriers and fibers with more than 50% kaolin in fiber suffer from low textilemechanical properties. Another preferred additive suitable in the present invention is talc. The fibers can be staple fibers of a definite length or continuous filaments.

(5) The fibers described herein may be processed to textile structures by any way known to those skilled in the art of textile manufacturing. The fibers may be processed to knitted or woven or nonwoven structures. Preferably the fibers are processed to a nonwoven textile structure. Making of nonwoven texile products is described in Non-Woven Textile Fabrics Kirk-Othmer Encyclopedia of Chemical Technology, 3rd Ed., Vol. 16 p. 72-124. Nonwoven textile structures consisting of continuous filaments may also be made e.g. by the Meltblowing process. Manufacturing of the flame barrier of the present invention can include chemical, thermal, mechanical bonding or no additional bonding after web formation of a nonwoven flame barrier product.

(6) Preferably the flame barrier described herein is a high loft nonwoven product. The term high loft is used for nonwoven fiber products not densified or purposely compressed over a significant portion of the product in the manufacturing process preferably having a greater volume of air than fiber, i.e. more than 50% of the material volume is air. The high-loft nonwoven material typically has a thickness of more than 6 mm. Typical products for the market flame barrier are either carded or air laid and thermally bonded.

(7) The flame barrier of the present invention may comprise besides the Lyocell fibers comprising incorporated inorganic additive one or more other fiber types of natural or synthetic origin. The fiber blend may include inherent flame-retardant fibers such as e.g. aramid, arimid, melamine or novoloid fibers. The fiber blend may include fibers made flame-retardant by including a flame-retardant monomer in the polymer or incorporation of a flame-retardant additive as e.g. modacrylics, polyvinylchloride, polyvinylidenechloride or flame-retardant polyester fibers. The fiber blend may include natural fibers such as cellulosics (e.g. cotton) or wool. The fiber blend may include synthetic fibers such as e.g. polyester, polyamide, polyurethane, polyolefin or polyacrylonitrile fibers. The fiber blend may include polyester fibers made from natural raw materials such as e.g. polylactic acid fibers. Typical products for the market flame barrier are blends of cellulosics with synthetic fibers.

(8) The flame barrier according to the present invention may contain between 20% and 100%, preferably between 30% and 70% of the kaolin containing fiber.

(9) The flame barrier according to the present invention may get an additional flame-retardant topical treatment. Such topical treatments are well-known to the expert as described at the beginning.

(10) Such Lyocell fibers could also find application in areas such as automotives, trains and airplanes as lightweight sound or flame barriers.

(11) The invention will now be illustrated by examples. These examples are not limiting the scope of the invention in any way.

Examples 1 to 2

(12) Kaolin (Miragloss 90, from BASF) was added to a dope of sulfite pulp in aqueous N-Methylmorpholine-N-oxide in certain amounts being sufficient to give a resulting amount of 15 resp. 30% (w/w) in the fiber. This dope was spun into 3,3 dtex fibers according to the well-known dry-jet-wet spinning method. The textile mechanical properties of the resulting fibers are shown in Table 1.

(13) TABLE-US-00001 TABLE 1 Additive content % Tenacity Elongation Example Fiber type Additive (w/w) cond. cN/tex cond. % 1 Lyocell Kaolin 15 22.2 11.3 2 Lyocell Kaolin 30 18.8 13.3 3 Lyocell Aluminum 15 25.9 10.1 hydroxide 4 Lyocell Aluminum 30 17.9 14.1 hydroxide 5 Lyocell Calcium 15 19.1 10.3 carbonate 6 Lyocell Calcium 30 15.6 13.0 carbonate 7 Viscose Kaolin 23 13.7 15.4 8 Viscose Kaolin 40 8.0 16.9

(14) The examples clearly show that the mechanical properties of the fibers decrease with increasing content of the incorporated inorganic additives. But even with 30% of incorporated inorganic additives they are sufficient for the use in flame barriers for mattresses and upholstered furniture.

(15) Comparative example 3 to 4Lyocell-fibers were spun in the same way as in example 1 to 2. However, instead of kaolin aluminum hydroxide was incorporated to give fibers with 15% and 30% aluminum hydroxide respectively. The textile mechanical properties of the resulting fibers are shown in Table 1.

Comparative Example 5 to 6

(16) Lyocell-fibers were spun in the same way as in example 1 to 2. However, instead of kaolin calcium carbonate was incorporated to give fibers with 15% and 30% calcium carbonate respectively. The textile mechanical properties of the resulting fibers are shown in Table 1.

Comparative Example 7 to 8

(17) Viscose fibers 1,7 dtex were spun in a conventional, well-known way. Kaolin was incorporated to give fibers with 23% and 40% kaolin respectively. The textile mechanical properties of the resulting fibers are shown in Table 1. Compared to the fibers according to inventive examples 1 and 2 the tenacity was very low and the spinning behavior was quite bad.

Examples 9 to 14

(18) The fibers of examples 1 to 6 were blended with cotton and polyester fibers in the ratios as shown in Table 2, carded and slightly needle-punched to give high-loft nonwoven materials of square weight and thickness described in Table 2. Additionally the thickness was measured according to EN-ISO 9073-2.

(19) These materials were used to manufacture mattresses for burn tests. The construction of the mattresses to be tested according to 16 CFR 1633 was as shown in FIGS. 1 to 3, wherein FIG. 1 shows the construction of the mattress panel in order from top to bottom, FIG. 2 shows the mattress border and FIG. 3 shows the foundation in order from outer to inner. The burn tests were performed according to the test protocol of 16 CFR 1633. For each example three mattresses were burned. Materials will pass the 16 CFR 1633 test only if all three mattresses fulfill the test criteria.

(20) TABLE-US-00002 TABLE 2 Incorporated Incorporated square Thickness Thickness 16CFR 1633 Fibers Fibers Cotton PES weight at 0.1 kPa at 0.5 kPa Test Example of example % % % g/m.sup.2 mm mm result 9 1 23.4 40.6 36.0 291 13.2 7.2 Pass 10 2 30.5 50.3 19.2 262 12.5 6.5 Pass 11 3 32.5 35.1 32.4 289 11.8 6.9 Fail 12 4 27.0 29.0 44.0 270 10.5 6.4 Fail 13 5 27.0 34.4 38.6 241 10.0 5.9 Fail 14 6 29.2 29.3 41.5 204 9.9 4.9 Fail