EP2294259B1 - Cellulose fiber and method for the production thereof - Google Patents

Description

The invention relates to a cellulose fiber of the genus Lyocell and a process for their preparation.

In recent decades, due to the environmental problems of the known viscose process for producing cellulosic fibers, intensive efforts have been made to provide alternative, more environmentally friendly processes. As a particularly interesting possibility has emerged in recent years to dissolve cellulose without forming a derivative in an organic solvent and to extrude molded articles from this solution. Fibers spun from such solutions have been assigned the genus name Lyocell by BISFA (The International Bureau for the Standardization of Man Made Fibers), where organic solvent means a mixture of an organic chemical and water.

Furthermore, such fibers are also known by the term "solvent-spun fibers".

It has been found that, as an organic solvent, in particular a mixture of a tertiary amine oxide and water is outstandingly suitable for the production of lyocell fibers or other shaped articles. The amine oxide used is predominantly N-methylmorpholine-N-oxide (NMMO). Other suitable amine oxides are in the EP-A 553,070 revealed. A process for producing cellulosic molded bodies from a solution of cellulose in a mixture of NMMO and water are, for. B. in the U.S. Patent 4,246,221 or in the PCT WO 93/19230 revealed. The cellulose solution is extruded from a spinneret, stretched in an air gap and precipitated from the solution in an aqueous precipitation bath. This process will hereinafter be referred to as "amine oxide process" or "lyocell process", which by the abbreviation "NMMO" in the following all tertiary amine oxides are meant that can dissolve cellulose. The processing of lyocell fibers immediately after spinning is for example in the WO 92/14871 and the WO 00/18991 described. Fibers produced by the amine oxide process are characterized by high fiber strength in the conditioned and in the wet state, a high wet modulus and a high loop strength.

It is further known that lyocell fibers have a certain tendency to fibrillate. Many measures have already been proposed against this feature, with the Treatment of the lyocell fiber with a crosslinking agent is a commercially significant procedure.

Suitable crosslinking agents are for example in the EP 0 538 977 , of the WO 97/49856 and the WO 99/19555 described. Other crosslinking agents are for example from WO 94/09191 and the WO 95/28516 known.

wobei X Halogen, R=H oder einen ionischen Rest darstellt und n=0 oder 1 ist, bzw. ein Salz dieser Verbindung.A particularly preferred crosslinking agent is a substance of the formula (I)

wherein X represents halogen, R = H or an ionic radical and n = 0 or 1, or a salt of this compound.

Lyocell fibers treated with such crosslinkers are better protected against fibrillation than untreated Lyocell fibers. One measure of fibrillation protection is the wet rub resistance (NSF) of the fibers.

However, even with lyocell fibers treated with crosslinking agents, in particular during their further processing into yarns and fabrics, pilling and fibrillation problems due to insufficient fibrillation protection can still occur again and again.

As has also been found, the fibrillation protection decreases during storage over time. It is believed that in some cases this is due to a slow but steady hydrolysis of the crosslinking bonds. The extent of this Vernetzerhydrolyse and thus the reduction of fibrillation protection can be very different, depending on how long and under which climatic conditions the cellulose fiber is stored.

The present invention has for its object to provide a cellulose fiber of the genus Lyocell, in which by treatment with a Crosslinking agent resulting fibrillation protection over a longer period of time than in conventional Lyocell fibers is maintained.

• der durch das Vernetzungsmittel induzierte Fibrillationsschutz verändert sich bei Lagerung der Faser innerhalb eines pH-Bereiches von 4,0 bis 10,0, insbesondere unter Einwirkung von Feuchtigkeit und/oder Wärme
• innerhalb des pH-Bereichs von 4,0 bis 10,0 existiert ein optimaler Wert, an welchem die Stabilität des durch das Vernetzungsmittel induzierten Fibrillationsschutzes bei Lagerung am größten ist
• um den optimalen Wert herum existiert ein geeigneter Bereich, in welchem die Stabilität gegenüber der Stabilität beim optimalen Wert um maximal 20 % verringert ist
• der geeignete Bereich wird innerhalb des pH-Bereiches von 4,0 bis 10,0 durch zumindest einen Grenzwert begrenzt, an welchem die Stabilität gegenüber der Langzeitstabilität beim optimalen Wert um 20 % verringert ist und unterhalb bzw. oberhalb desselben eine weitere Verringerung der Stabilität eintritt
• das Vernetzungsmittel hat ein den pH-Wert-veränderndes Potenzial.

This object is achieved by a cellulose fiber of the genus Lyocell, which is treated with a crosslinking agent, wherein the crosslinking agent on the fiber induces fibrillation protection and has the following properties:

• the fibrillation protection induced by the crosslinking agent changes upon storage of the fiber within a pH range of 4.0 to 10.0, in particular under the action of moisture and / or heat
• within the pH range of 4.0 to 10.0, there exists an optimum value at which the stability of the cross-linking agent-induced fibrillation protection on storage is greatest
• There is a suitable range around the optimum value, in which stability stability is reduced by a maximum of 20% at the optimum value
• the suitable range is limited within the pH range of 4.0 to 10.0 by at least one limit at which the stability to the long-term stability at the optimum value is reduced by 20% and below or above thereof a further reduction of the stability occurs
• the crosslinking agent has a pH-altering potential.

The fiber according to the invention is characterized in that the fiber contains a substance buffering in the suitable range and has a buffer capacity of at least 12 mmol / kg of fiber, preferably 15 to 70 mmol / kg of fiber in the suitable range.

• "Fibrillationsschutz" - Die mit dem Vernetzungsmittel behandelte Faser hat eine höhere Beständigkeit gegenüber Fibrillation als eine unbehandelte Faser. Dies wird mit dem in der WO 99/19555 beschriebenen Test auf Nass-Scheuerfestigkeit festgestellt.

For the purposes of the present invention,

• "Fibrillation Protection" - The fiber treated with the crosslinker has a higher resistance to fibrillation than an untreated fiber. This will be with the in the WO 99/19555 described test for wet abrasion resistance.

"The fibrillation protection induced by the crosslinking agent changes during storage of the fiber within a pH range of 4.0 to 10.0" - When storing the treated with the crosslinking agent fiber finds - eg by the action of heat and moisture, especially steam - one Change in fibrillation protection instead. This can be ascertained by means of a below-described wet scrub resistance test of fibers stored at different pHs held constant under buffering for a certain period of time. In each case, that period is determined up to which has reduced wet rub resistance from baseline by 30%.

"Within the pH range of 4.0 to 10.0 an optimal value exists" - This is the case when in a certain pH range within the range of 4.0 to 10.00 during storage with the Crosslinking agent treated fiber enters a lower drop in fibrillation protection than at other pH values. Thus, in the pH range of 4.0 to 10.0, there must be at least one pH at which the stability of the crosslinker-induced fibrillation protection is greatest on storage, i. at which the time to which the wet rub resistance has decreased 30% from baseline is the longest. This value is hereinafter referred to as "optimum value". "Since a constant optimum of the stability of the fibrillation protection in some cases instead of just one point over a certain pH range (eg, a range of 0.5 to 1 pH units) can be observed, the term "optimum value" also encompasses such a pH range.

"A suitable range exists around the optimum value" - There must be a region around the optimum value in which stability stability is reduced at the optimum value. In the following, the term "suitable range" refers to the range in which the stability stability is reduced by a maximum of 20% at the optimum value.

"The suitable range is limited within the pH range of 4.0 to 10.0 by at least one limit value" - that means that the suitable range is at least toward one direction (ie in the direction of acidic or in the direction of alkaline pH values) is limited by a pH at which the time to reach a 30% reduction in wet rub resistance has been reduced to 80% of the (maximum) time at the "optimum value". This value will be referred to as the "limit" below.

"The cross-linking agent has a pH-changing potential" - this criterion means that the cross-linking agent itself in the course of storage, for example by exposure to moisture or heat or by reacting with the fiber - be it by cleavage from the fiber or by further reacting unbound or free reactive groups - affects the pH of the fiber. This is determined by observing the evolution of the fiber pH of a fiber treated with the particular crosslinker (see below).

The pH of the fiber is determined by the method given below.

The buffer capacity of a fiber is also determined by a test described below.

The term "contains" for the purposes of the present invention also includes an attachment of the buffering substance to the surface of the fiber.

• a) verändert sich bei Lagerung der mit dem Vernetzungsmittel behandelten Faser innerhalb eines pH-Bereiches von 4,0 bis 10,0, insbesondere unter Einwirkung von Feuchtigkeit und/oder Wärme, der Fibrillationsschutz,
• b1) existiert innerhalb des pH-Bereichs von 4,0 bis 10,0 ein optimaler Wert, an welchem die Stabilität des durch das Vernetzungsmittel induzierten Fibrillationsschutzes bei Lagerung am größten ist,
• b2) existiert um den optimalen Wert herum ein geeigneter Bereich, in welchem die Stabilität gegenüber der Stabilität beim optimalen Wert um maximal 20 % verringert ist,
• b3) ist der geeignete Bereich innerhalb des pH-Bereiches von 4,0 bis 10,0 durch zumindest einen Grenzwert begrenzt, an welchem die Stabilität gegenüber der Langzeitstabilität beim optimalen Wert um 20 % verringert ist und
• c) hat das Vernetzungsmittel ein den pH-Wert veränderndes Potenzial,

so hat sich gezeigt, dass durch die Zugabe von puffernden Substanzen, welche im für das jeweilige Vernetzungsmittel spezifischen geeigneten pH-Bereich puffern, der pH-Wert der Faser in diesem geeigneten Bereich gehalten werden und damit auch der Abbau des Fibrillationsschutzes im Zuge der Lagerung hintangehalten werden kann.If a crosslinking agent meets the above criteria, ie

• a) changes during storage of the treated with the crosslinking agent fiber within a pH range of 4.0 to 10.0, in particular under the action of moisture and / or heat, the fibrillation protection,
• b1), within the pH range of 4.0 to 10.0, there is an optimum value at which the stability of the cross-linking agent-induced fibrillation protection is greatest at storage,
• b2) a suitable range exists around the optimum value, in which the stability stability is reduced by a maximum of 20% at the optimum value,
• b3) the appropriate range within the pH range of 4.0 to 10.0 is limited by at least one limit at which the stability to long-term stability at the optimum value is reduced by 20% and
• c) the crosslinking agent has a pH-changing potential,

it has thus been found that by adding buffering substances which buffer in the pH range which is specific for the particular crosslinking agent, the pH of the fiber is kept within this suitable range and thus also the degradation of the fibrillation protection during storage is prevented can be.

1. 1) Temperatur
2. 2) Feuchtigkeit
3. 3) Faser-pH

As has been shown in extensive investigations, the speed of the mentioned breakage of the crosslinking bonds depends in particular on the following 3 parameters:

1. 1) temperature
2. 2) moisture
3. 3) fiber pH

While the parameters 1) and 2) can be influenced only slightly by the manufacturer, it has been shown that the pH of the fiber can have a decisive influence on the rate of crosslinker hydrolysis. It was found that depending on it used crosslinking agents have a pH range in which the crosslinking of lyocell fibers is most stable.

Crosslinked lyocell fibers may vary depending on the process, e.g. Type of applied avivages, in the preparation of an initial pH in each case for the particular crosslinking agent used optimal range. However, it has now been found that, depending on the process control and the type of crosslinking agent used, the fibers have a more or less large proportion of partially reacted crosslinker molecules, which are e.g. may contain acid-forming radicals (e.g., chlorine radicals). These reactive radicals may be used in further processing steps, e.g. in the dryer, during the rewetting, steaming, but also during storage abreagieren. This will change the pH of the fiber. In turn, changing the pH away from the optimum pH range accelerates crosslinker hydrolysis.

The present invention is now based on this knowledge, which is not previously known, by using a substance which has a buffering effect in this pH range in order to maintain the pH of the fiber in the optimum range for the particular crosslinker.

This ensures that the fibrillation protection is maintained even during storage of the fiber over a longer period.

The fiber according to the invention preferably has a pH in the suitable range.

At least one of the buffering substances used preferably also has a pK _a value in the suitable range. Also suitable are substances having a pK _a value just outside the appropriate range, for example in the range of in each case up to 1 pH unit, preferably up to 0.5 pH units above or below having the "limit", provided that the Buffering effect towards those pH values at which a deterioration of the storage stability of Fibrillationsverhaltens occurs.

wobei X Halogen, R=H oder einen ionischen Rest darstellt und n=0 oder 1 ist, bzw. ein Salz dieser Verbindung ist. Die Verwendung dieser Vernetzungsmittel zur Behandlung von Lyocellfasern ist aus der WO 99/19555 bekannt. Besonders bevorzugt ist das Natriumsalz des 2,4-Dichlor-6-hydroxy-1.3.5-triazins.A crosslinking agent which satisfies the above criteria a) to c) and is particularly preferably used is a substance of the formula (I)

wherein X represents halogen, R = H or an ionic radical and n = 0 or 1, or a salt of this compound. The use of these crosslinking agents for the treatment of lyocell fibers is known from the WO 99/19555 known. Particularly preferred is the sodium salt of 2,4-dichloro-6-hydroxy-1,3,5-triazine.

It has been found that crosslinking agents of this group satisfy the above criterion a), i. upon storage of the crosslinker-treated fiber within a pH range of 4.0 to 10.0, particularly under the action of moisture and / or heat, the fibrillation protection changes.

Furthermore, these crosslinking agents, in particular the sodium salt of 2,4-dichloro-6-hydroxy-1,3,5-triazine, have an "optimum value" (or an optimum range in this case) at a pH in the range from 9 to 9.5 to (criterion b1)), in which the stability of the fibrillation protection during storage is best. In addition, these crosslinking agents, in particular the sodium salt of 2,4-dichloro-6-hydroxy-1,3,5-triazine, have a "limit value" (as defined above) at a pH of 8.5 (criterion b2)). , Below this limit, the fibrillation protection during storage of the fiber drops much faster than above this value. There is thus a "suitable" range according to the above definition (criterion b3)). The sodium salt of 2,4-dichloro-6-hydroxy-1,3,5-triazine has, in addition, another limit value at a pH of 10.5, above which the fibrillation protection in turn drops much faster during storage. However, storage of cellulosic fibers at pH values above 10.5 is not realistic, so that the use of buffering substances in this area is not necessary.

Finally, crosslinkers of this group also have a pH-altering potential (criterion c), apparently due to the release or the reaction of the halogen groups contained therein.

Therefore, a fiber treated with this crosslinking agent should preferably have a pH in the range of 8.5 to 10.5.

The buffering substances used in this preferred embodiment advantageously have a pKa in the range from 8.0 to 11.0.

In particular, substances from the group consisting of borax are suitable as the buffering substance; Carbonates or bicarbonates of alkali metal ions (eg Li, Na, K ions, ammonium or cations derived from substituted amines (eg mono-, di-, trimethyl-ammonium or mono-, di-, triethyl-ammonium), phosphates, hydrogen phosphates or dihydrogen phosphates cations derived from alkali metal ions, ammonium or substituted amines, ammonia, substituted amines (eg mono-, di-, trimethyl-amine or mono-, di-, triethyl-amine), guanidine or guanidinium salts, and mixtures thereof and mixtures with carboxylic acids and their salts.

Borax (Na ₂ B ₄ O ₇ × 10 H ₂ O) and the system bicarbonate / carbonate, and mixtures thereof, as well as mixtures of borax and phosphate buffer are particularly suitable for inorganic buffer systems. A mixture of carbonate and phosphate buffer can also be used. Particular preference is given to using borax as the buffering substance.

Borax buffers in both pH directions, thus partially preventing too high fiber pH levels by neutralizing any areas of higher alkali content.

The use of borax appears to make sense especially in the pH range of 8.8-9.7, wherein a pH value deviating from pKa (= 9.2-9.3) of borax can be adjusted by addition of customary acids or alkalis.

However, it is advantageous to maintain a pH value around the pKa value. Instead of borax alone, however, borax can also be used together with other buffer systems (bicarbonate / carbonate and / or phosphate buffer).

According to the invention, borax in amounts of 0.05% to 1.4% borax based on cellulose is added to the fiber, preferably 0.3-0.6%, wherein the application can be carried out simultaneously with the application of a finishing agent. Preferably, borax is added as a solid over a Feststoffdosiereinheit, since you do not need to dilute the lubricant. Borax can also be added as an aqueous solution when applying the finish.

The concentration of borax in the fiber is preferably at least 1525 mg borax per kg fiber. This corresponds to a content of at least 173 mg / kg boron on fiber. In particular, concentrations of 2860 mg to 14000 mg borax per kg fiber are favorable. This corresponds to a content of 324 to 1600 mg / kg boron on fiber.

Also well suited as a buffering substance is the buffer system sodium bicarbonate / sodium carbonate, in particular in concentrations of at least 848 mg per kg of fiber (calculated as sodium carbonate). Particularly preferred is a concentration range of 1580 mg to 7420 mg per kg of fiber (calculated as sodium carbonate).

The cellulose fiber according to the invention furthermore preferably has a fiber moisture content of 8-10%. At higher moisture contents, buffering, as provided according to the invention, is all the more important.

wobei X Halogen, R=H oder einen ionischen Rest darstellt und n=0 oder 1 ist, bzw. ein Salz dieser Verbindung ist, bevorzugt mit dem Natriumsalz des 2,4-Dichlor-6-hydroxy-1.3.5-triazins, welche die in Anspruch 1 aufgeführten Eigenschaften aufweist, behandelt ist, und dadurch gekennzeichnet ist, dass die Faser eine im pH-Bereich von 7,5 bis 11,0, bevorzugt 8,5 bis 10,5 gegen Säureeinwirkung puffernde Substanz enthält und in diesem pH-Bereich eine Pufferkapazität von mindestens 12 mmol/kg Faser, bevorzugt 15 bis 70 mmol/kg Faser aufweist.The invention also relates to a cellulose fiber of the genus Lyocell, which is reacted with a crosslinking agent of the formula (I)

wherein X is halogen, R = H or an ionic radical and n = 0 or 1, or a salt of this compound, preferably with the sodium salt of 2,4-dichloro-6-hydroxy-1,3,5-triazine, which has the properties listed in claim 1, is treated, and characterized in that the fiber contains in the pH range of 7.5 to 11.0, preferably 8.5 to 10.5 acid-buffering substance and in this pH Has a buffer capacity of at least 12 mmol / kg of fiber, preferably 15 to 70 mmol / kg of fiber.

This embodiment of the cellulose fiber according to the invention preferably contains the buffers specifically specified above in the amounts indicated there.

Another aspect of the present invention relates to a bale of cellulosic fibers containing the lyocell fibers of the present invention.

It is known that lyocell fibers, as well as other man-made fibers, are crimped into bales after their manufacture and are shipped in this form to customers (e.g., yarn producers). The storage of the fibers thus takes place both at the manufacturer (before shipping) and at the customer (before further processing) in the form of bales. In order to maintain the fibrillation protection during this storage, it is therefore particularly advantageous if the bale according to the invention contains Lyocell fibers stabilized by the presence of a buffering substance. In particular, the bale may consist essentially completely of the fibers according to the invention. By "substantially" is meant that minor admixtures of other fibers (e.g., tag fibers to better identify the product) may be included.

Also textile articles such as yarns, fabrics, knits, braids and knitted fabrics are stored, whereby degradation of the fibrillation protection can occur. Accordingly, the present invention also relates to such textile articles as yarns, fabrics, knits, braids and knitted fabrics which contain the lyocell fibers according to the invention. In particular, the invention relates to those textile articles which have not yet been subjected to a wet process (eg reactive dyeing), since, in conventional wet processes of cellulosic fibers in the textile chain, the majority of reactive groups of crosslinkers reacts as expected, which is why no (or hardly any) pH-changing potential is present, which would make the buffering invention necessary.

For the production of the fiber according to the invention, a method is used which comprises the step of applying a substance which buffers in a suitable range to a cellulose fiber of the genus Lyocell.

The application of the buffering substance preferably takes place in the course of the production process of the cellulose fiber, prior to its compression into a bale. In particular, the application should be done either during or after the last wet process intended to treat the fiber. If, after the application of the buffering substances, a wet step still takes place, they would be washed out of the fiber again.

For example, in the last process step, the buffering substance can be applied to the fiber at the same time as the drying bath with the oiling bath.

Alternatively, the buffering substance may be applied in an application process immediately prior to treatment of the fiber with the oiling bath.

It is also possible to apply the buffering substance to the fiber immediately before, during or at the end of the drying process, prior to pressing the fibers into a bale.

In all variants, the buffering substance can be applied in liquid form or sprayed as an aerosol onto the fiber, applied via a contact lip or mixed in the powdery state in a solid state in the fiber.

When using crosslinkers of formula (I), the addition of alkaline buffer systems such as borax, e.g. in all the cases examined, a pronounced stabilizing effect on the crosslinking of the lyocell fibers was observed in the bath. It can be assumed that the addition of borax in the lubricant, depending on the content and content of partially reacted crosslinker, the period in which the crosslinked lyocell fiber can be used without restrictions of Fibrillationsschutzes, compared to a non-buffered fiber approximately doubled. This can be ensured over a much longer period, the quality consistency in networked lyocell fibers.

Examples Measurement Methods: Measuring method for determining the pH value of fibers:

In this method, the fibers are treated with deionised (DI) water. Subsequently, the pH of the water is measured.

3g (+/- 0.01g) of dry (air-dry) fiber are weighed on the analytical balance into a 100 ml sample tube. Then, the fibers are mixed with 30 ml of deionized water and treated for one hour at room temperature, being shaken approximately every 15 min. Subsequently, the fiber is separated from the extract with the aid of a glass rod and the pH of the extract is determined with a pH meter (Knick).

Determining the stability behavior of the fibrillation protection during storage, the pH-dependent sensitivity of the crosslinker bond and the pH range suitable for the long-term stability of the crosslinker bond (criteria a) and b1) to b3)):

Principle:

There are from the expert known buffer systems (eg acetate, citrate, phosphate, bicarbonate, carbonate, borax) in the pH range 4.0 to 10.0 in increments of 0.5 pH units buffer solutions, with a concentration of the buffering substances of at least 0.1 mol / l and a pKa of the buffer system, which should not deviate more than 0.8 pH units from the adjusted pH.

Variant 1) Wet soaked in the fleet

First, the fibrillation protection of the starting fiber treated with the cross-linking agent to be tested is determined by wet rub resistance (test according to US Pat WO 99/19555 ) in at least 3 parallel determinations. The value for the wet abrasion resistance ("NSF") is given in x U / dtex (revolutions / dtex), where x should have a value> 450 for good fibrillation protection.

Thereafter, fibers in a liquor ratio of 1:10 are introduced into each of the said buffer systems in the pH range from 4.0 to 10.0 and kept in this liquid in a closed vessel at 50.degree.

Remove a fiber sample from each of the buffer vessels over a period of 25 days at intervals of 2 days, rinse them with demineralized water free of the buffer solution, gently dry at 60 ° C for 5 hours in the laboratory dryer and determine the NSF.

At the end of the 25-day storage, the NSF values obtained are plotted against time for each buffer system.

If at least one of the curves obtained in this way has a definite downward trend with a loss of at least 30% of the abrasion value from beginning to end, then criterion a) is fulfilled, ie it is a hydrolysis-sensitive crosslinking system.

If the presence of the criterion a) is established, the slopes of the curves at the various pH values are compared and, in particular, the time to reach a 30% reduction in the NSF. The pH at which the time to reach a 30% reduction in NSF is the longest compared to the baseline is the "optimal value" (criterion b1)). The range around the "optimal value" at which the time to reach a 30% decrease in the NSF has decreased by less than 20% from the maximum duration is the "appropriate range" (criterion b2)), within which the fiber should be buffered according to the invention. The pH at which the time to reach a 30% reduction has decreased to 80% of the maximum time is referred to as the "limit" (criterion b3)).

Variant 2) By impregnating the fibers with buffers, then drying and storing under humid climatic conditions

The method is similar to variant 1, except that in this case the starting material treated with a crosslinking agent, after determination of the original NSF, in each case in a buffer system, which should also contain about 0.1 mol / l of the respective buffer, in the pH range of 4 , 0 to 10.0 is impregnated with gradations of the pH in steps of 0.5 pH units. By subsequent pressing or spinning, care is taken to ensure an equally high liquor pickup of all fibers treated in this way. Subsequently, the fibers are gently dried in the laboratory dryer (60 ° C 5 hours).

• 2.1) Bei einer Temperatur von 40°C und einer relativen Luftfeuchte von 85 %:
  • Hierzu muss der Lagertest über 12 Wochen durchgeführt werden. 1 x pro Woche ist eine Bestimmung der NSF durchzuführen. (Man kann davon ausgehen, dass unter diesen Klimabedingungen die Veränderung des Fibrillationsschutzes gut 10x so schnell abläuft wie bei der Lagerung eines Ballens mit durchschnittlicher Feuchte bei 25°C)
• 2.2) Schnelltest bei 50°C und einer relativen Luftfeuchte von 100 %:
  • Hier wird als System ein dicht verschließbares Gefäß verwendet, dessen Bodenraum mit voll entsalztem Wasser gefüllt wird, wobei die Fasern in einigem Abstand oberhalb der Flüssigkeit positioniert werden. Es ist darauf zu achten, dass die Fasern keine Wandungen o.ä. berühren, um Kondensationserscheinungen zu vermeiden. Der Schnelltest ist wie System 1) nach 25 Tagen abgeschlossen, wobei jeden 2. Tag eine Bestimmung des NSF durchgeführt wird.

The hydrolytic stability of the crosslinking agent can now be determined as follows:

• 2.1) At a temperature of 40 ° C and a relative humidity of 85%:
  • For this, the storage test must be carried out for 12 weeks. Once a week, a determination of the NSF is to be carried out. (It can be assumed that, under these climatic conditions, the change in the fibrillation protection takes place about 10 times as fast as when storing a bale with an average moisture content at 25 ° C.)
• 2.2) Quick test at 50 ° C and a relative humidity of 100%:
  • Here is used as a system a tightly sealable vessel whose bottom space is filled with demineralized water, the fibers are positioned at some distance above the liquid. It is important to ensure that the fibers have no walls etc. Touch to avoid condensation. The rapid test is complete as system 1) after 25 days, with a determination of the NSF performed every 2nd day.

The evaluation is analogous to variant 1).

Again, the "threshold" is the pH at which the time to reach a 30% reduction has dropped to 80% of the maximum time.

Criterion c) - Determining a pH-altering potential

A crosslinking agent according to the invention is then maintained in its proper pH range by the use of buffering substances when it is present in the fiber or in a fiber containing article such as e.g. Bales, yarns and textile raw materials still reactive groups that during storage and / or typical moist or thermal treatment processes of yarn / text. Surfaces are capable of altering the fiber pH in a manner that will leave the appropriate pH range without buffering.

1. 1) Ermitteln des Faser-pH-Wertes der mit dem Vernetzungsmittel behandelten Faser - im folgenden "Ausgangsfaser" genannt (die Faser kann auch in Form eines Garns oder einer textilen Rohware vorliegen). Siehe dazu die oben beschriebene Messmethode
2. 2) Entfernen wasserlöslicher Substanzen (Salze, Puffer, Avivagen) durch 10maliges Waschen der Ausgangsfaser mit voll entsalztem-Wasser in einem Flottenverhältnis von mindestens 1:10 bei Raumtemperatur und vorsichtiges Trocknen (60°C 5 h). Die durch das Waschen erhaltene Faser wird im folgenden "gewaschene Faser" genannt.
   Durch das Entfernen der wasserlöslichen Substanzen wird eine Verfälschung des nachfolgenden Tests durch diese Substanzen, welche selbst den pH-Wert beeinflussen könnten, vermieden. Da umgekehrt aber durch ein Waschen und Trocknen der Faser bereits Folgereaktionen des Vernetzers hervorgerufen werden können, ist es notwendig, auch die (nicht gewaschene) Ausgangsfaser zu untersuchen.
3. 3) Ermitteln des Faser-pH der gewaschenen Faser
4. 4) Lagerstabilitätsversuch sowohl der Ausgangsfaser als auch der gewaschenen Faser gemäß der für die Kriterien a) und b) oben beschriebenen Varianten 2.1 oder 2.2 (jedoch ohne vorangehende Applikation von Puffern), unter Ermittlung der Veränderung der NSF über die Zeit
5. 5) Überprüfen des Faser-pH-Wertes nach der Lagerung sowohl in der Ausgangsfaser als auch in der gewaschenen Faser: Bei einer Änderung des Faser-pH-Wertes in wenigstens einer der beiden Typen um wenigstens 1 pH-Einheit gegenüber dem anfänglichen Faser-pH (insbesondere in Richtung weg vom hinsichtlich der Kriterien a) und b) ermittelten geeigneten pH-Bereich) liegt ein Vernetzungsmittel mit einem über die Lagerzeit den pH verändernden Potenzial vor.

To determine such a pH-changing potential, the procedure is as follows:

1. 1) Determining the fiber pH of the fiber treated with the crosslinking agent - hereinafter referred to as "starting fiber" (the fiber may also be in the form of a yarn or a textile raw material). See the measurement method described above
2. 2) Removal of water-soluble substances (salts, buffers, avivages) by washing the starting fiber 10 times with demineralised water in a liquor ratio of at least 1:10 at room temperature and gentle drying (60 ° C. for 5 h). The fiber obtained by washing is hereinafter called "washed fiber".
   By removing the water-soluble substances, a falsification of the subsequent test by these substances, which themselves could influence the pH, is avoided. Conversely, however, as a result of washing and drying of the fiber, subsequent reactions of the crosslinker can already be induced, it is also necessary to investigate the (non-washed) starting fiber.
3. 3) Determining the fiber pH of the washed fiber
4. 4) Storage stability test of both the starting fiber and the washed fiber according to variants 2.1 or 2.2 described above for criteria a) and b) (but without prior application of buffers), determining the change in NSF over time
5. 5) Check the fiber pH after storage in both the starting fiber and the washed fiber: If the fiber pH in at least one of the two types changes by at least 1 pH unit from the initial fiber pH (Especially in the direction away from the appropriate pH range determined with regard to criteria a) and b)), a crosslinking agent with a potential which changes the pH over the storage time is present.

Are all criteria a) to c) fulfilled, i. If a pH-dependent reduction in the fibrillation protection during the storage period and a change in the pH in the starting fiber or the washed fiber in the direction of lower stability of the crosslinker has been detected, then there is a crosslinker system which can be stabilized by the use of buffers according to the invention.

General proof of the use of buffer systems in a cross-linked fiber which has the abovementioned properties or determination of the buffer capacity:

1. i) Der Nachweis von säurepuffernden Substanzen ist dann notwendig, wenn im oben beschriebenen Verfahren ein "Grenzwert" oberhalb eines pH-Wertes von 4,0 und wenn eine Sensibilität in Richtung saurer pH-Werte festgestellt wurde (d.h. dass sich die Lagerungsstabilität in Richtung von pH-Werten unterhalb des Grenzwertes hin verschlechtert).

If the appropriate range of a particular cross-linking agent is established, the stabilization by buffer systems or the determination of the buffer capacity of the fiber can be demonstrated as follows:

1. i) The detection of acid-buffering substances is necessary when, in the process described above, a "threshold" above a pH of 4.0 and when sensitivity to acidic pH has been established (ie storage stability towards pH values below the limit deteriorated).

Detection of acid-buffering substances:

• ii) der Nachweis von alkalipuffernden Substanzen ist dann notwendig, wenn im oben beschriebenen Verfahren ein "Grenzwert" unterhalb eines pH-Wertes von 10,0 und wenn eine Sensibilität in Richtung alkalischer pH-Werte festgestellt wurde (d.h. dass sich die Lagerungsstabilität in Richtung von pH-Werten oberhalb des Grenzwertes hin verschlechtert).

Fibers (optionally in the form of yarns or textile raw materials) are extracted with demineralized water for one hour at room temperature in a liquor ratio of exactly 1:10. Fibers and extract are separated and an aliquot of exactly 50 ml of this extract is first titrated with 0.01 mol / l HCl to a pH which is exactly 1.50 units below the previously determined "limit". Thereafter, the solution is back-titrated with 0.01 M NaOH to a pH which is exactly 1.50 pH units above the "limit". From the titration curve, the consumption of 0.01 mol / l NaOH is read off within these 3.00 pH units. This corresponds to 5 ml of a buffer capacity of 10 mmol / kg fiber.

• (ii) the detection of alkali-buffering substances is necessary when, in the process described above, a "threshold" below a pH of 10.0 and when sensitivity to alkaline pH has been established (ie storage stability towards pH values above the limit deteriorated).

Detection of alkali-buffering substances

Fibers (yarns, raw materials) are extracted with deionized water for one hour at room temperature in a liquor ratio of exactly 1:10. Fibers and extract are separated and an aliquot of exactly 50 ml of this extract is first titrated with 0.01 M NaOH to a pH which is exactly 1.50 units above the previously determined "limit". Thereafter, the solution is back-titrated with 0.01 mol / l HCl to a pH which is exactly 1.50 pH units below the limit. From the titration curve, the consumption of 0.01 mol / l HCl is read off within these 3.00 pH units. This corresponds to 5 ml of a buffer capacity of 10 mmol / kg fiber.

embodiments Example 1:

• Beispiel 1a) (erfindungsgemäß) - Behandlung mit Borax (0,6 % auf Faser), pH-Wert der Faser = 9,2
• Beispiel 1b) (erfindungsgemäß) - Behandlung mit Carbonatpuffer (Na₂CO₃/NaHCO₃, molares Verhältnis 1:1; 0,2 % auf Faser), pH-Wert der Faser = 10,2
• Beispiel 1c) (Vergleichsbeispiel) - Keine Behandlung, pH-Wert der Faser = 8,5
• Beispiel 1d) (Vergleichsbeispiel) - Behandlung mit einem schwach sauren Faserfinisher, pH-Wert der Faser = 6,7

Lyocell fibers prepared in accordance with the prior art and cross-linked in the same way with a crosslinker of the above formula (I) (sodium salt of 2,4-dichloro-6-hydroxy-1,3,5-triazine) were treated as follows:

• Example 1a) (according to the invention) - treatment with borax (0.6% on fiber), pH of the fiber = 9.2
• Example 1b) (according to the invention) Treatment with carbonate buffer (Na ₂ CO ₃ / NaHCO ₃ , molar ratio 1: 1, 0.2% on fiber), pH of the fiber = 10.2
• Example 1c) (Comparative Example) - No treatment, pH of the fiber = 8.5
• Example 1d) (Comparative Example) - Treatment with a weakly acidic fiber finisher, pH of the fiber = 6.7

• Beispiel 1a) (Borax): ca. 11 Wochen
• Beispiel 1b) (Carbonat): 10 Wochen
• Beispiel 1c) (kein Puffer): ca. 7 Wochen
• Beispiel 1d) (saurer Finisher): 3 Wochen.

The wet rub resistance (NSF) of the fibers was determined according to, for example, US Pat
WO 99/19555 measured method described. Subsequently, the fibers were stored under identical conditions in an extreme climate with high humidity and temperature. The so-called "half-life" has been determined, which is the time in which the NSF has fallen to half the original value:

• Example 1a) (borax): about 11 weeks
• Example 1b) (carbonate): 10 weeks
• Example 1c) (no buffer): about 7 weeks
• Example 1d) (acid finisher): 3 weeks.

In addition, in the first weeks of storage in the fibers according to Example 1) and 2) no drop in the NSF was observed, while in the fibers according to Example 3) and 4) a steady drop in the NSF was observed.

Example 2:

The sodium salt of 2,4-dichloro-6-hydroxy-1,3,5-triazine has been found by the method described above to have a "cut-off" at pH 8.5, below which the storage stability of the fibrillation protection deteriorates.

• Ermittelt wurde der Verbrauch an 0,01 mol/l NaOH im pH-Bereich von 7,0 bis 10,0. Aus diesem errechnet sich die Pufferkapazität der Faser nach folgender Formel: $$\mathrm{ml\; Verbrauch\; NaOH}*0,01*1000/5=\mathrm{mmol\; Puffer}/\mathrm{kg\; Faser}$$
  

Accordingly, the buffer capacity was determined by titrating the extract of the fiber with 0.01 mol / l HCl to pH 7.0 and back titration with 0.01 mol / l according to the method described above on different samples of Lyocell fibers each treated with the same amount of this crosslinking agent. l NaOH to pH 10.0 determined:

• The consumption of 0.01 mol / l NaOH in the pH range of 7.0 to 10.0 was determined. From this, the buffer capacity of the fiber is calculated according to the following formula: $$\mathrm{ml\; consumption\; NaOH}*0.01*1000/5=\mathrm{mmol\; buffer}/\mathrm{kg\; of\; fiber}$$
  

• Probe 1: Faser mit 2 g Borax/kg Faser behandelt
• Probe 2: Faser mit 3,5 g Borax/kg Faser behandelt
• Probe 3: Faser mit 12 g Borax /kg Faser behandelt
• Probe 4: Faser mit 6 g Borax /kg behandelt
• Probe 5: Faser mit 1,5 g Natriumcarbonat /kg Faser behandelt
• Probe 6: Faser mit 1 g Natriumcarbonat/kgFaser behandelt
• Proben 7 bis 11: Proben von jeweils nicht mit puffernden Substanzen behandelten Fasern

Probe: ml 0,01m NaOH zwischen pH 7,0 bis pH 10,0 mmol Puffer/kg Faser zwischen pH 7,0 und 10,0 1 12,61 25,22 2 19,27 38,54 3 59,69 119,38 4 33,36 66,72 5 9,74 19,48 6 7,56 15,11 7 bis 11 (Durchschnittswert) 3,26 ± 0,95 6,52 ± 1,92 The following samples were tested:

• Sample 1: fiber treated with 2 g borax / kg fiber
• Sample 2: fiber treated with 3.5 g borax / kg fiber
• Sample 3: Fiber treated with 12 g borax / kg fiber
• Sample 4: fiber treated with 6 g borax / kg
• Sample 5: Fiber treated with 1.5 g sodium carbonate / kg fiber
• Sample 6: Fiber treated with 1 g sodium carbonate / kg fiber
• Samples 7 to 11: Samples of non-buffered fibers, respectively

Sample: ml of 0.01M NaOH between pH 7.0 to pH 10.0 mmol buffer / kg fiber between pH 7.0 and 10.0 1 12.61 25.22 2 19.27 38.54 3 59.69 119.38 4 33.36 66.72 5 9.74 19.48 6 7.56 15.11 7 to 11 (average) 3.26 ± 0.95 6.52 ± 1.92

It can be seen that for all samples containing a buffering agent ranging from 7 to 10, such as borax or carbonate, the buffering capacity is (significantly) more than 12 mmol / kg of fiber.

Claims (16)

1. A cellulose fibre of the genus Lyocell which is treated with a cross-linking agent, with the cross-linking agent inducing a protection from fibrillation on the fibre and exhibiting the following properties:

   - the protection from fibrillation induced by the cross-linking agent changes if the fibre is stored within a pH range from 4.0 to 10.0, in particular under the influence of moisture and/or heat

   - within the pH range from 4.0 to 10.0, an optimum value exists at which the stability of the protection from fibrillation induced by the cross-linking agent during storage is highest

   - a suitable range exists around the optimum value in which the stability is reduced by 20% at the most, compared to the stability at the optimum value

   - within the pH range from 4.0 to 10.0, the suitable range is limited by at least one limiting value at which the stability is reduced by 20% compared to the long-term stability at the optimum value and with a further decrease in stability occurring below and above said value, respectively

   - the cross-linking agent has the capability to change the pH value,

   characterized in that the fibre contains a substance buffering in the suitable range and exhibits a buffer capacity of at least 12 mmol/kg fibre, preferably from 15 to 70 mmol/kg fibre, in the suitable range.
2. A cellulose fibre according to claim 1, characterized in that the fibre exhibits a pH value in the suitable range.
3. A cellulose fibre according to claim 1 or 2, characterized in that the buffering substance or optionally at least one of the buffering substances has a pK_a value in the suitable range or outside of the suitable range by up to 1 pH unit.
4. A cellulose fibre according to any of the preceding claims, characterized in that the cross-linking agent is a substance of formula (I)

   

   wherein X represents halogen, R=H or a ionic moiety and n=0 or 1, or a salt of said compound, respectively, preferably the sodium salt of 2,4-dichloro-6-hydroxy-1.3.5-triazine, and that the fibre contains a substance buffering against the action of acid in the pH range from 7.5 to 11.0, preferably from 8.5 to 10.5.
5. A cellulose fibre according to claim 4, characterized in that the fibre exhibits a pH value ranging from 8.5 to 10.5.
6. A cellulose fibre according to any of claims 4 to 5, characterized in that the buffering substance or optionally at least one of the buffering substances has a pK_a value ranging from 8.0 to 11.0.
7. A cellulose fibre according to any of claims 4 to 6, characterized in that the buffering substance is selected from the group consisting of borax; carbonates or bicarbonates of alkali metal ions, ammonium or cations derived from substituted amines; phosphates, hydrogen phosphates or dihydrogen phosphates of alkali metal ions, ammonium or cations derived from substituted amines; ammonia; substituted amines; guanidine or guanidinium salts; and mixtures thereof as well as mixtures with carboxylic acids and salts thereof.
8. A cellulose fibre according to claim 7, characterized in that, as a buffering substance, it contains borax in concentrations of at least 1525 mg borax per kg fibre.
9. A cellulose fibre according to claim 8, characterized in that, as a buffering substance, it contains borax in concentrations from 2860 mg to 14000 mg borax per kg fibre.
10. A cellulose fibre according to claim 7, characterized in that, as a buffering substance, it contains the buffer system sodium hydrogen carbonate / sodium carbonate in concentrations of at least 848 mg per kg fibre (calculated as sodium carbonate).
11. A cellulose fibre according to claim 10, characterized in that, as a buffering substance, it contains the buffer system sodium hydrogen carbonate / sodium carbonate in concentrations from 1580 mg to 7420 mg per kg fibre (calculated as sodium carbonate).
12. A cellulose fibre according to any of the preceding claims, characterized in that it exhibits a fibre moisture of 8-10%.
13. A bale of cellulose fibres, containing cellulose fibres according to any of the preceding claims.
14. A yarn, woven fabrics, knitted fabrics, braided fabrics and hosieries, containing cellulose fibres according to any of claims 1 to 12.
15. A process for the production of a cellulose fibre according to any of claims 1 to 12, comprising the step of applying a substance buffering in the suitable pH range onto a cellulose fibre of the genus Lyocell.
16. A process according to claim 15, characterized in that the application of the buffering substance occurs in the course of the manufacturing process for the cellulose fibre, before it is pressed into a bale.