Flame-resistant molded cellulose bodies produced according to a direct dissolving method

Abstract

The invention relates to molded cellulose bodies, in particular fibers, filaments, directly spun nonwovens, films, or foams which have flame-resistant properties. The fibers and filaments can be further processed as textiles into yarns, wovens, knitted fabrics, and nonwovens. The molded bodies are produced from solutions of cellulose and melamine cyanurate or cellulose and crosslinked or partially crosslinked melamine resin particles in an organic solvent. The melamine cyanurate or the melamine resin particles provide the molded cellulose bodies with flame-retardant properties. The molded cellulose bodies made of cellulose and melamine cyanurate or melamine resin particles can further contain flame retardants, in particular flame retardants which act synergistically, in a particulate form. The obtained textile fibers and nonwoven materials have a soft touch and can be processed or finished as filaments or yarns on conventional textile machines.

Claims

1. A shaped lyocell article having a cellulose matrix and being of low flammability by virtue of the presence therein of melamine cyanurate or of partly or wholly crosslinked melamine resin, wherein the melamine cyanurate or the melamine resin is distributed homogeneously in the form of particles over the cross section of the cellulose matrix, the shaped article having a fraction of melamine cyanurate or melamine resin particles of 20 to 35 wt.% for textile applications with flame retardancy properties.

2. The shaped article of claim 1, wherein said article is a fiber, filament, non-woven, film or foam.

3. The shaped article of claim 1, wherein the shaped article is a fiber having a diameter or film having a thickness and the melamine resin particles possess a degree of crosslinking of 75 to 100% and a relation between an average size of 98% of the melamine resin particles (D.sub.98) and the diameter of the resulting fibers or thickness of the resulting films (D.sub.f) satisfies the following equation: $\frac{{\left(D_{98}\right)}^2}{{\left(D_f\right)}^2}0.25.$

4. The shaped article of claim 1, wherein said article comprises at least one further flame retardant, the solubility of the further flame retardant in water of 25 C. being less than 10 mg/l and the further flame retardant is in particulate form, the particles being smaller than 50 m.

5. The shaped article of claim 4, wherein said further flame retardant is synergistic and selected from aluminum hydroxide, red phosphorus, an organophosphorus compound, silicatic nanoparticles or a compound comprising boron.

6. The shaped article of claim 4, wherein the further flame-retardant particles are smaller than 10 m.

7. The shaped article of claim 1, wherein, in addition to melamine cyanurate, said article further comprises melamine or other melamine salts.

8. The shaped article of claim 7, wherein said melamine salts are melamine oxalate, melamine phosphate or melamine borate.

9. A method for producing a shaped, low-flammability lyocell article of claim 1, comprising: a) producing a suspension of cellulose in a hydrous or anhydrous organic solvent which is a direct solvent for cellulose, b) converting the suspension into a cellulose solution by shearing, optionally in conjunction with evaporative removal of water, c) forming the cellulose solution by extruding or blow molding, d introducing the shaped article into a precipitation bath, e) washing and optionally after treating, and f) drying of the shaped article; wherein in step a) or in or at the end of step b), a fraction of 20 to 35 wt. % of particles of melamine cyanurate or of wholly or partly crosslinked melamine resin are admixed.

10. The method of claim 9, wherein the organic solvent is N-methylmorpholine N-oxide monohydrate or an ionic liquid.

11. The method of claim 9, wherein said forming comprises extruding or blow molding by means of a shaping tool.

12. The method of claim 10, wherein the organic solvent is butylmethylimidazolium chloride, ethylmethylimidazolium acetate or ethylmethylimidazolium diethylphosphate.

13. Apparel comprising the shaped article of claim 1.

14. A shaped lyocell article having a cellulose matrix and being of low flammability by virtue of the presence therein of melamine cyanurate or of partly or wholly crosslinked melamine resin, wherein the melamine cyanurate or the melamine resin is distributed homogeneously in the form of particles over the cross section of the cellulose matrix, the shaped article having a fraction of melamine cyanurate or melamine resin particles of 17 to 35 wt. % for textile applications with flame retardancy properties, wherein said shaped lyocell article is self-extinguishing and does not burn through a measuring mark made at 38 mm.

15. The shaped article of claim 14, wherein said article is a fiber, a filament, a nonwoven, a film or a foam.

16. The shaped article of claim 14, wherein said article is mixed with other shaped articles in the form of blends or laminates.

Description

EXAMPLE 1

(1) By mixing together and stirring, a suspension was produced from 6% of cellulose having a Cuoxam DP of 615, 6% of melamine cyanurate (BUDIT 315 from Chemische Fabrik Budenheim KG), 52.5% of NMMO, and 35.5% of water. This suspension was brought to a solution by shearing and evaporation of water under conditions of 95 C. and 70 mbar reduced pressure, and the solution was subsequently forced through a fiber spinneret, passed through an air gap into a precipitation bath, and drawn off. This was followed by washing to remove the solvent, finishing, cutting, and drying of the fibers. The resultant fiber had a BUDIT 315 content of 50% and a linear density of 3 dtex. From these fibers, nonwoven webs of 250 g/m.sup.2 were produced. These webs were subjected to LOI (in accordance with ISO 4589) and also to a fire chamber fire test (in accordance with DIN 4102-1 Class B2, DIN 75 200, ISO 3795 DIN 75200).

(2) Furthermore, by varying the composition, further fibers with different amounts of BUDITwere produced, from which nonwoven webs were likewise produced and tested. An overview of the composition of the fibers, and the LOI values and fire tests determined on nonwoven webs, are given in the table below:

(3) TABLE-US-00001 Comparative Fiber Fiber Fiber Fiber fiber 1a 1b 1c 1d Fiber composition 100/0 83/17 75/25 67/33 50/50 Cellulose/Budit 315 Linear fiber density, 1.9 2.0 2.0 2.0 3.0 dtex Fiber tenacity, cN/tex 40.8 32.3 28.9 24.2 17.5 Fiber elongation, % 15.3 Web grammage, g/m.sup.2 250 250 250 250 250 Fire test Fire chamber Burning distance, mm 180 0 0 0 0 Classification B SE SE SE SE LOI, % oxygen 19 23 25 26 31 SE - self-extinguishing (specimen ignites, but does not burn through to the first measuring mark (38 mm)) B - flame travels the entire burning distance to the end of the sample (180 mm)

EXAMPLE 2

(4) A spinning solution with a composition of 13% of cellulose and 87% of NMMO monohydrate, and also a suspension of 30% of melamine cyanurate (MELAPUR MC 15) in aqueous solution with 83% NMMO, were produced. Thereafter the solution and the suspension were mixed intensively using a dynamic mixer in a ratio of 5.4 parts of cellulose solution to 1 part of melamine cyanurate suspension. Furthermore, the resulting solution was spun to give fibers, and nonwoven webs were produced as set out in Example 1. The resultant 250 g/m.sup.2 web was self-extinguishing, and the flame went out without traveling the burning distance; the LOI measured was 27%. The fiber processed in the web had a melamine cyanurate fraction of 33% with a linear density of 1.9 dtex.

EXAMPLE 3

(5) The procedure of Example 2 was repeated, but the suspension admixed to the solution was composed of 25% of melamine cyanurate (BUDIT 315), 5% of aluminum hydroxide (APYRAL 40CD) in aqueous solution with 83% of NMMO. The spun fiber had a 27% melamine cyanurate content and 5.5% aluminum hydroxide content. The 250 g/m.sup.2 web obtained from these fibers was self-extinguishing, and the flame went out without traveling the burning distance; the LOI measured was 26%.

EXAMPLE 4

(6) The procedure of Example 1 was repeated, but as well as cellulose, melamine cyanurate, and aqueous NMMO, a separately prepared dispersion of phyllosilicate (NANOFIL 116), dispersed in water and stabilized with a dispersing system, was additionally added. Moreover, the solution and the fibers were produced as in Example 1. The resulting fibers, Linear density of 2 dtex, had a composition of 75% of cellulose, 20% of melamine cyanurate, and 5% of phyllosilicate. Fire tests on a knitted fabric of 300 g/m.sup.2, produced from 100% fiber yarns of this fiber with a cut length of 38 mm, produced the following assessment: LOI: 29%

(7) Burning test in the fire chamber: self-extinguishing without a flame traveling the burning distance.

(8) After 50 industrial washes, the tests concluded with virtually identical results (LOI: 28, burning test self-extinguishing).

EXAMPLE 5

(9) By mixing together and stirring, a suspension was produced from cellulose having a DP of 615, melamine cyanurate (BUDIT 315), and 60% aqueous NMMO. This suspension was converted by shearing and evaporation of water, at a temperature of 95 C. and under a pressure of 70 mbar, into a solution whose composition was as follows: 2.9% of cellulose, 26.5% of melamine cyanurate, 70.6% of NMMO monohydrate.

(10) The resulting solution had a zero-shear viscosity of 620 Pa.Math.s (85 C.) and was converted by a modified meltblown process into a spunbonded web which, after washing to remove the NMMO and drying, consisted of 91% of melamine cyanurate and 9% of cellulose. According to the setting of the conditions of the spinning pump, the quantity and temperature of blowing air, and the belt speed of web transport, spunbonded webs of 15 to 400 g/m.sup.2 with linear fiber densities of 1 to 10 m were obtained.

EXAMPLE 6

(11) By joint mixing of 64 g of air-dry cellulose having a DP of 620, 775 g of aqueous NMMO (60%), and 21 g of finely ground, etherified melamine resin (D.sub.98 5 m), and evaporation of 238 g of water by application of a reduced pressure of 60 mbar at 95 C., a homogeneous suspension of melamine resin in a cellulose solution was obtained. This solution was spun by an air-gap spinning process, with subsequent washing and drying, to form fibers with a linear density of 2.3 dtex. Nonwoven webs produced from these fibers, in the burning test in a combustion chamber, were self-extinguishing and were characterized by an LOI of 25.