EP1601824B1

EP1601824B1 - The method of making modified cellulose fibers

Info

Publication number: EP1601824B1
Application number: EP03816268A
Authority: EP
Inventors: Bogumil Laszkiewicz; Piotr Kulpinski; Barbara Niekraszewicz; Piotr Czarnecki; Marcin Rubacha; Maria Okraska; Jolanta Jedrzejczak; Bogdan Peczek; Ryszard Kozlowski; Jerzy Mankowski
Original assignee: Politechnika Lodzka; Instytut Wlokien Naturalnych
Current assignee: Politechnika Lodzka; Instytut Wlokien Naturalnych
Priority date: 2003-03-10
Filing date: 2003-06-25
Publication date: 2007-01-17
Anticipated expiration: 2023-06-25
Also published as: WO2004081267A1; DE60311324D1; DE60311324T2; ATE351933T1; EP1601824A1; PL201205B1; PL359080A1

Abstract

The method of making modified cellulose fibers from cellulose solution in N-methylmorpholine-N-oxide, which involves mixing ccllulose with aqueous N-methylmorpholine-N-oxide, evaporating and filtration of the spinning solution subsequently forced through the holes in the spinning nozzle into the aqueous spinning bath, finally rinsing, drying and conditioning, is described by the fact that modifying substances such as ceramic oxides, metal oxides or their mixtures, if necessary containing additional surfactants, carbon, if necessary modified with silver, bactericidal agents, acid-base indicators, thermo chromic dyes with nano- or supra molecular break-up are added into the cellulose, the solvent or the spinning solution.

Description

The subject of the present invention is the method of making modified cellulose fibres from cellulose solutions in N-methylmorpholine-N-oxide.
One known process for manufacturing cellulose fibres from cellulose solutions in N-methylmorpholine-N-oxide (NMMO) consists of mixing cellulose with an aqueous solution of NMMO, evaporating excess water from the cellulose solution, filtrating the spinning solution, which is then forced through the spinneret holes into the airspace, followed by treatment in a spinning bath, drying and conditioning. In order to produce fibres with modified properties, modifiers such as titanium dioxide and organic or inorganic dyes in the form of particles or microcapsules with a diameter over I µm are added to the spinning solution (Textiles Magazine 2004, No 4, p.7); the modifiers may also include synthetic polymers with various molecular weights, as mentioned in the patent specification US 6245837 B1.
When manufacturing cellulose fibres by the process delineated in the present invention, the incorporation of either organic or inorganic, low- or high-molecular compounds into the spinning solution in the form of particles with diameters higher than 1 µm would result in unpredictable changes to the fibre properties, in comparison to those of fibres obtained without these modifiers.
Cellulose fibres such as Lyocell, produced from cellulose solutions in NMMO, are susceptible to fibrillation. The textile processing of such fibres creates technological problems connected with dusting and fluffing from yarns made from these fibres, especially in the production of knitted fabrics. To overcome this problem, low- or high-molecular modifiers are added to the spinning solution to change the structure of these fibres, and consequently to reduce their susceptibility to fibrillation.
Patent specification US 5 047 197 suggests the addition of polyethylene glycol with a molecular weight of 1:4.5 million to the spinning solution to improve the flow of the spinning solution through the spinneret capillaries, which would at the same time modify the fibre microcrystalline structure.
Patent Application DE 19542533 A1 describes the production of cellulose fibres by the NMMO process, in which carbon black particles with a diameter of about 20 nm are added to the spinning solution to modify the fibres' microcrystalline structure. This process yields electro-conductive fibres in which carbon black particles are distributed either throughout the fibre's whole volume or in its core. One drawback of such an incorporation of carbon nano-particles into the spinning solution, as described by D. Vorbach and E. Tanger in Chemical Fibres International 1998, No 48, p.120, is that these particles agglomerate in the polar medium of NMMO, which makes it necessary to add carbon black in quite a high quantity, over 30% by wt., in order to obtain good electro-conductivity of fibres. This high carbon particle content in the fibre-forming polymer reduces the tensile strength and knot breaking strength of fibres, making them unsuitable for textile processing. Such a modification results in weak and breakable fibres. Such undesirable fibre properties are due to the mechanical disintegration of carbon black into particles with an average diameter of 20 nm. The mechanical disintegration of solid particles of organic or inorganic pigments, e.g. carbon black, titanium dioxide, zinc oxide, coloured pigments based on spinel (MgAl₂O₄) or nickel-antimony yellow (Pigment Yellow 53/77780) or chromium-antimony yellow (Pigment Yellow 24/77310), makes it impossible to prepare a homogeneous pigment in terms of particle size. Mechanically disintegrated pigments added to the spinning solution to modify fibre properties show a wide distribution of particle size, as illustrated by Gauss' distribution curve. As a result, particles with high diameters deteriorated the physico-mechanical properties of the fibres, making them unsuitable for textile processes such as spinning, weaving or knitting. Solid particles of inorganic or organic pigments, disintegrated mechanically, e.g. in a ball mill, have almost circular shapes. The incorporation of such shaped pigments into the spinning solution prior to fibre formation disturbs the development of oriented crystalline structure of fibres, lowering the intermolecular interactions between cellulose macromolecules.
In such a case, the circular particles of modifier isolate particular cellulose macromolecules in the fibre, and eliminate possible intermolecular bonds via Van der Waals forces; this leads to the deterioration of mechanical fibre properties such as tensile strength and knot breaking strength.
Patent Application WO 96/27638 states that the drop in fibre tensile strength and knot breaking strength, as well as the disturbance of the fibre spinning process, result from the agglomeration of mechanically-disintegrated neutral pigments, e.g. titanium dioxide, barium sulphate, carbon black etc. Patent Application WO 96/27638 proposes producing modified fibres by incorporating mechanically disintegrated particles, into the spinning solution. Unfortunately, this method also fails to guarantee fibres with good properties, as solid coated particles or particles dispersed in a matrix are also agglomerated in a polar medium like the cellulose-NMMO-water system. This system causes the coat or matrix to dissolve, while the modifier molecules are agglomerated to form a heterogeneous dispersion in the fibre-forming polymer, which considerably reduces the properties of the modified fibres.
The properties of both nano-particles and supramolecular particles of organic or inorganic pigments such as titanium dioxide, zinc oxide or dyes are completely different from those of the molecules of pigments and dyes produced by traditional technologies, added in accordance with Patent Application WO 96/27638 to the spinning solution in order to prepare modified fibres.
Patent Application WO 01/06054 A1 states that the use of nano-particles for surface modification of textiles ensures that these textile products have excellent performance properties. Although the effect of surface modification of fibres and textiles with nano-particles is very resistant to washing under household conditions, it is not resistant to use and wear, during which the expected effect disappears due to superficial abrasion.
The method of making modified cellulose fibres from cellulose solutions in N-methylmorpholine-N-oxide consists of mixing cellulose with an aqueous solution of NMMO, evaporating the resultant cellulose solution to obtain a cellulose content of 12-20% by wt. and water content below 13% by wt., filtrating the spinning solution and extruding it through spinneret holes into airspace, from which it is led into an aqueous spinning bath followed by rinsing, drying and conditioning, the modification effect being obtained by adding modifiers in the form of ceramic oxides, metal oxides or a mixture of these oxides, if necessary containing an addition of surface-active agents, carbon, if necessary modified with silver, bactericidal agents, acid-base indicators, thermochromic dyes in a quantity no higher than 10% by wt. in relation to the weight of cellulose, according to the present invention characterised by the fact, that modifiers have nano particle size and they are added to cellulose, solvent or the spinning solution. Ceramic oxides, preferably silica, metal oxides or mixtures of these are used in the form of nano particle size or a suspension of this nano particle size in water or an aqueous NMMO solution. Carbon is used in the form of fibrous nano-tubes. As an acid-base indicator are preferably used thymol blue or phenolphthalein.
This method according to the invention allows relatively simply modified cellulose fibres with specific properties to be produced, owing to the incorporation of modifiers in the form of nano- particles into cellulose, solvent or the spinning solution. The process , according to which modifiers in the form of nano-particles, prepared by hydrolysis (among other things) of silicon- or organometallic compounds (as reported by the Journal of Nano-Crystalline Solids 1998, No 194, p. 72-77), are added to cellulose, solvent or the spinning solution, provides a durable modification of the fibre properties, and causes no deterioration in fibre tensile strength and knot breaking strength, which has turned out to be an unexpected effect. The nano-particle size of modifiers used in the process according to the invention ensures that the modified cellulose fibres which are produced show excellent properties specific to the given modifier. At the same time, not only are the mechanical properties of fibres not deteriorated, but they are in fact improved, which is also an unexpected effect. The incorporation of carbon nano-tubes of a fibrous character, prepared under special conditions (Carbon 38 (2000), 1933- 1937), ensures that the fibres produced show excellent mechanical and electrical properties.
The method according to the invention is illustrated by the examples given below which do not limit its range.

Example I.

60 cellulose parts by weight with the degree of polymerization of 800 comprising 8% humidity by weight were introduced into the crusher connected with the vacuum pump and equipped with indirect heating; thereto subsequently 720 parts by weight of 50% aqueous NMMO solution and 20 parts by weight of 30% aqueous water suspension of silicon dioxide with nano particle size were added, the molecules diameter being 7 nm.
Having set in motion the crusher mixers, the vacuum pump therein was switched on, and to start with the crusher was heated till the inside temperature reached 100° C, subsequently the temperature inside the crusher was raised till it reached 130° C.
After approximately 60 minutes the water content in the system cellulose-NMMO-water diminished to 10 weight %, the cellulose was thoroughly solved, and the pulp in the crusher became light brown in color, and it had viscosity 1300 Pa x s. The spinning solution made by this method contained 15% cellulose by weight, having been thoroughly filtered by acid resisting screen unit it was forced into the spinning head of worm spinning frame, where it was forced through the 0,16 mm holes in the spinning nozzle at temperature 100°C, placed 20 mm above the spinning bath, into the aqueous spinning bath of 80°C comprising 4% NMMO by weight. The formed fibers were rinsed in the rinsing bath of 80° C, taken up on the reel with the speed of 80 m/min, subsequently dried and conditioned.
The received fibers were circular in section, white and lustreless, tensile strength being 32 cN/tex, elongation 12 % and fibrillization 2-3, whereas the fibrillization of unmodified fibers is 6.

Example II.

Aqueous supension of silicon dioxide SiO₂ with nano particle size, the molecules diameter being 50 nm, was introduced into the cellulose solution in NMMO, prepared in the same conditions as in Example I, in such an amount that the SiO₂ content was 3 weight % in ratio to the cellulose weight, and the whole lot was mixed. The received spinning solution was filtered as in Example I, subsequently at temperature 110°C forced through the holes in the spinning nozzle, placed 20 mm above the spinning bath, into the spinning bath as in Example I. The next step was as in Example I. The speed of fiber forming was 120 m/ min. The received fibers were circular in section, tensile strength being 36 cN/tex, elongation 13 % and fibrillization 3-4.

Example III.

The spinning solution was prepared as in Example I, but at the same time, while dissolving the cellulose, aqueous supension of silicon dioxide SiO₂ with nano particle size (the molecules diameter being 78 nm), was added to the crusher in such quantity that SiO₂ content was equal to 5 weight % in ratio to the cellulose by weight. At the same time the surfactant under the trade name Berol V-4026 was introduced along with the silicon suspension in the amount 1 weight % in ratio to the cellulose weight. The received spinning solution was filtered as in example I, subsequently at temperature 110° C forced through the holes in the spinning nozzle, placed 45 mm above the spinning bath, into the spinning bath as in Example I. The next step was as in Example 1. The speed of fiber forming was 160 m/ min.
The received fibers were described as-having tensile strength 38 cN/tex, elongation 12 % and fibrillization 3-4.

Example IV.

Titan dioxide TiO₂ in the shape of powder, the grain diameter being 17 nm, was introduced into the cellulose solution in NMMO, prepared in the same conditions as in Example I, in the amount 1 weight % in ratio to the cellulose by weight, and the whole lot was exposed to mixing. The received spinning solution was filtered as in example 1, subsequently at temperature 110° C forced through the holes in the spinning nozzle, placed 150 mm above the spinning bath, into the spinning bath at temperature 30°C containing 6% NMMO. The next step was as in Example 1. The speed of fiber forming was 150 m/ min.
The received fibers were described as having tensile strength 36 cN/tex, elongation 10 % and fibrillization 3-4. Moreover they were described as having 50% greater ability to disperse UV radiation as compared to fibers received by all known methods.

Example V.

Aqueous supension of zinc oxide ZnO with powder, the particles diameter being 30 nm, was introduced into the cellulose solution in NMMO, prepared as in Example I, in such an amount that the ZnO content was 1 weight % in ratio to the cellulose weight, and the whole lot was mixed. The received spinning solution was filtered as in Example I, subsequently at temperature 110° C forced through the holes in the spinning nozzle, placed 60 mm above the spinning bath, into the spinning bath of 20° C, containing 4,5 % NMMO. The next step was as in Example I. The speed of fiber forming was 180 m/min.
The received fibers were described as having tensile strength 33 cN/tex, elongation 10%, fibrillization 3 and 37% greater ability to disperse UV radiation as compared to standard cellulose fibers.

Example VI.

The spinning solution was prepared as in Example 1, but at the same time, in the place of aqueous supension of silicon dioxide, aqueous solution of aluminium trioxide Al₂O₃ with nano particle size, the particles being 37 nm, was added in such quantity that Al₂O₃ content was equal to 1,5 weight % in ratio to the cellulose by weight. The received spinning solution was filtered as in example I, subsequently at temperature 110°C forced through the holes in the spinning nozzle, placed 40 mm above the spinning bath, into the spinning bath of 20°C, containing 4% NMMO. The next step was as in Example I. The speed of fiber forming was 80 m/min.
The received fibers, circular in section, were described by the tensile strength 39 cN/tex, elongation 14 % and fibrillization 3.

Example VII.

Aqueous supension of zinc oxide, titan dioxide and silicon dioxide (ZnO, TiO₂, SiO₂) by component weight in ratio I: I: I, with powder of, the particles diameter being 7-50 nm, was introduced into the cellulose solution in NMMO, prepared in the same conditions as in Example I, in such an amount that the oxides content was 3 weight % in ratio to the cellulose weight. The received spinning solution was filtered as in example I, subsequently at temperature 110°C forced through the holes in the spinning nozzle, placed 20 mm above the spinning bath, into the spinning bath of 20° C, containing 4% NMMO. The next step was as in Example I. The speed of fiber forming was 140 m/min.
The received fibers were described as having tensile strength 42 cN/tex, elongation 10%, fibrillization 3 and ability to disperse UV radiation 40% greater as compared to standard cellulose fibers.

Example VIII.

Solutions containing 12 weight parts of spruce cellulose (DP 840), 76 weight parts of NMMO, 12 weight parts of water, propyl ester of gallic acid under the trade name Tenox in the amount 1 weight % in ratio to cellulose weight and a bactericide agent triclosan under the trade name Irgasan DP 300 in the shape of powder, the particles diameter being 137 nm, in the amount 0,5-5 weight % in ratio to the cellulose weight were prepared. The solutions were mixed at 117°C for 70 minutes under lowered pressure. From the originated spinning solutions after filtration fibers were formed by forcing the spinning solutions at temperature 115°C through the 18-hole spinning nozzle, the hole diameter being 0,4 mm and the duct length being 3,5 mm, with the speed 82 m/min into the coagulation bath containing water at temperature 20°C. The distance between the spinneret and the coagulation bath was 100 mm. The produced fibers were rinsed in water bath at temperature 80°C, subsequently they were dried.
Antibacterial activity of produced fibers towards Escherichia coli was estimated based on the Japanese standard JIS L1902; 1998. It was stated that the fibers originating from the spinning solution already containing 0.5 weight % of antibacterial agent showed high both bactericidal and bacteriostatic activity. It was stated, moreover, that adding even 5 weight % of a bactericide agent into the spinning solution does not cause any significant changes in physico-mechanical parameters as compared to cellulose fibers produced without Irgasan.

Example IX.

The process of fiber making was repeated as in Example VIII, but instead of Irgasan silver iodide AgJ in the shape of powder, the grain diameter being up to 98 nm, was added to the spinning solution in the amount 0,2-5 weight % in ratio to the cellulose weight.
Antibacterial activity of produced fibers was estimated as in Example VIII. It was stated that the fibers received from the spinning solution already containing 0.5 weight % of antibacterial agent showed high both bactericidal and bacteriostatic activity. It was stated, moreover, that adding 5 weight % of AgJ to the spinning solution causes only slight reduction of fiber elongation at breaking, and of water retention, as compared to other fibers produced without AgJ.

Example X.

The process of fiber making was repeated as in Example VIII, but, instead of Irgasan, Al₂O₃, doped with silver ion, under the trade name Biostat, in the shape of powder, the grain diameter being 57 nm, was added to the spinning solution in the amount 0,2-5 weight % in ratio to the cellulose weight: Antibacterial activity of produced fibers was estimated as in Example VIII. It was stated that the fibers originating from the spinning solution already containing 0.5 weight % of antibacterial agent showed high both bactericidal and bacteriostatic activity. It was stated, moreover, that adding 5 weight % of Biostat causes only slight change in physicomechanical parameters of fibers as compared to other fibers produced without Biostat.

Example XI.

The process of fiber making was repeated as in Example VIII, but, instead of Irgasan, silver-zinc phosphate under the trade name Novaron, in the shape of powder, the grain diameter being 132 nm, was added to the spinning solution in the amount 0,2-5 weight % in ratio to the cellulose weight.
Antibacterial activity of produced fibers was estimated as in Example VIII. It was stated that the fibers originating from the spinning solution already containing 0.5 weight % of antibacterial agent showed high bactericidal and bacteriostatic activity. The addition of even 5 weight % of Novaron caused insignificant physico-mechanical changes of the fibers as compared to other fibers produced without Novaron.

Bactericidal properties of fibers made in Examples VIII-XI were shown in tab. 1, and physico-mechanical properties of these fibers, according to the amount of antibacterial agent added, in tab. 2.

Table 1.

Example number	The antibacterial agent used	The amount of antibacterial agent in the spinning solution [%]	Amount of bacteria on the fiber sample	Fiber bacteriostatic activity [S]	Fiber bactericidal activity [L]
VIII	Irgasan DP 300	0,5	<20	6,8	4,0
IX	AgJ	0,5	<20	6,5	3,5
X	Biostat	0,5	<20	7,0	3,5
XI	Novaron	0,5	<20	7,0	3,5

Table 2.

Example number	The antibacterial agent used	The amount of antibacterial agent in the spinning solution	Linear mass (dtex)	Tensile (tearing) strength (cN/tex)	Elongation %	Sorption in 65% RH [%]	Retention [%]
Fibres without antibacterial agent			2,97	36,82	12,87	10,69	73,21
VIII	Irgasan DP 300	0,5	3,40	32,73	10,75	10,70	72,32
IX	AgJ	0,5	2,71	38,64	9,73	10,57	67,82
X	Biostat	0,5	3,79	31,54	7,01
XI	Novaron	0,5	2,20	39,21	7,16

Example XII.

Carbon nanotubes in the shape of powder was introduced into the cellulose solution in NMMO, prepared as in Example I, in the amount 3 weight % in ratio to the cellulose by weight, and the whole lot was exposed to mixing. The received spinning solution was filtered, subsequently forced through the 18-hole spinning nozzle with the speed of 87m/min into the spinning bath at temperature 20°C The distance between the spinneret and the aqueous bath was 100 mm. The produced fibers were rinsed under stress in water bath at temperature 80° C, subsequently they were dried and conditioned. Subsequently mechanical and electrical properties of the fibers were measured.
The received fibers were described as having tensile strength 36 cN/tex and elongation 10%. The fibers conducted the current, their resistance was 10³ Ω·cm whereas the resistance of fibers not containing carbon nanotubes was 10¹⁰ Ω·cm

Example XIII.

The spinning solution was prepared as in Example XII, and at the same time carbon nanotubes, modified by metallic silver, in the shape of powder, were introduced into the cellulose solution in NMMO in the amount 3 weight % in ratio to the cellulose by weight, Nanotubes were modified in such way that they were impregnated by aqueous solution of silver salt, subsequently the silver salts were reduced. Fibers were formed from the filtered spinning solution following Example XII.
It was stated that tensile strength of the received fibers was 36 cN/tex , elongation was 8% and their resistance rose to 10^-2 Ω·cm

Example XIV.

The spinning solution was prepared as in Example I, with such difference, that instead of thymol blue, phenolphthalein in the shape of powder, the particles diameter being 96 nm, was introduced in the amount 0,3 weight % in ratio to the cellulose by weight. Fibers were formed from the filtered spinning solution following example XII.
Tensile strength of the received fibers was 32cN/tex , elongation was 10%. The produced fibers were white, and turned red, if dipped in an aqueous solution at the pH of 10, whereas if dipped in an aqueous solution at the pH of 8 they turned blue, what proved that the received fibers are the pH sensors.

Example XV

The spinning solution was prepared as in Example I, with such difference, that instead of thymol blue, thermochromic dye BT-31 in the shape of powder, the particles diameter being 173 nm, was introduced in the amount 3 weight % in ratio to the cellulose by weight. Fibers were formed from the filtered spinning solution following example XII.
The produced fibers were pale blue, and turned white at the temperature 31° C. It proved that the received fibers are temperature sensors. Tensile strength of the received fibers was 35cN/tex , elongation was 12 %.

Example XVI.

The spinning solution was prepared as in Example XIV, with such difference, that instead of thymol blue, thermochromic dye Bt-43 in the shape of powder, the particles diameter being 85 nm, was introduced in the amount 2 weight % in ratio to the cellulose by weight. Fibers were formed from the filtered spinning solution following example XII.
The produced fibers were pale blue, and turned white at the temperature 43° C. In the temperature rising above 43° C they become colorless, and if the temperature was lowered below 43° C they became pale blue again. It proved that the received fibers had stable thermochromic properties. Tensile strength of the received fibers was 35cN/tex , elongation was 12 %.

Claims

A method of making modified cellulose fibres from cellulose solutions in N-methylmorpholine-N-oxide, consisting of mixing cellulose with an aqueous solution of NMMO, evaporating the resultant cellulose solution to obtain a cellulose content of 12-20% by wt and water content below 13.3% by wt., filtering the spinning solution and extruding it through the capillaries of spinneret into the airspace, from which it is led into an aqueous spinning bath, finally rinsing, drying and conditioning, with the modification effect being obtained by adding modifiers, characterised in that the modifying compounds are selected from the group of oxides, metal oxides or their mixtures, if necessary containing an addition of surfactants, carbon, in the form of nano-tubes of a fibrous character if necessary carbon modified with silver, bactericidal agents, acid-base indicators, and thermochromic dyes have nano-particles size and they are added to cellulose, solvent or the spinning solution in a quantity not higher than 10% by wt. in relation to the weight of cellulose.
The method as claimed in claim 1 characterised in that ceramic oxides, advantageously silicon dioxide, metal oxides or their mixtures are used in the form of nano-particle size or suspension of this nano-particle size in water or an aqueous solution of N-methyl morpholine-N-oxide;
The method as claimed in claim 1 characterised in that as an acid-base indicator are preferably used thymol blue or phenolphthalein with nano-particle size.