EP0889978A1

EP0889978A1 - Process for producing cellulose fibres and cellulosic fibre products

Info

Publication number: EP0889978A1
Application number: EP97914266A
Authority: EP
Inventors: Abdulmajid Hashemzadeh
Original assignee: Akzo Nobel NV
Current assignee: Akzo Nobel NV
Priority date: 1996-03-27
Filing date: 1997-03-19
Publication date: 1999-01-13
Also published as: AU2157897A; WO1997036029A1; JP2000507315A

Abstract

The invention concerns a process for producing cellulose fibres and cellulosic fibre products. According to the invention, the properties of cellulosic fibres spun from tertiary amine solutions or fibre products produced therefrom are improved owing to a treatment with a zinc chloride solution, which optionally contains an acid, with a zinc chloride concentration ranging from approximately 30 to 70 wt % at a temperature ranging from approximately 10 to 250 DEG C. The following improvements are attained over untreated fibres or fibre products: the tendency to fibrillate is reduced; grey-film formation is prevented and does not occur even after repeated washing; and the feel is softer and retains its softness even after repeated washing. Furthermore, the depth of dye absorption and uniformity are improved and retained even after repeated washing.

Description

Process for the production of cellulose fibers and cellulosic fiber products

Description:

The invention relates to a method for reducing the tendency of cellulose fibers to fibrillate, which at the same time brings about a reduced formation of gray fog, improved dyeability and levelness and a softer feel of textile products which were produced from the fibers treated according to the invention.

These are fibers which were obtained by spinning a solution of cellulose in a tertiary amine oxide, in particular in N-methylrriorpholine-N-oxide (NMMO).

Processes for the production of cellulose fibers by dissolving cellulose in a tertiary amine oxide as a solvent, in particular in NMMO and spinning this solution, are becoming increasingly important since they serve as an alternative to the processes previously used for the production of cellulosic fibers. The viscose process, in which the cellulose is first chemically converted to make it soluble, should be mentioned here in particular. Since the cellulose is regenerated with a considerable amount of waste that has to be processed or disposed of for further use, this process is subject to criticism.

The process, which works with NMMO, on the other hand, is very environmentally friendly, since the tertiary amine oxide used can be circulated and the cellulose is practically only dissolved and re-precipitated without being too chemically see reactions coming in which by-products to be disposed arise.

A disadvantage of this method, however, is that the fibers obtained tend to fibrillate relatively strongly, which is perceived as very disruptive for very many applications. It has been shown that cellulosic fibers which are produced by the NMMO process, particularly when wet, have a great tendency to fibrillate, especially when mechanical forces act on the fibers. This occurs in particular when dyeing and washing yarns which have been produced from the fibers just mentioned.

Fibrils have a disturbing effect on dyed textiles in that along folds which arise when washing in the washing machine, as a result of the increased abrasion at these points, a gray haze which is undesirable for aesthetic reasons is formed, which increases with each washing cycle.

Furthermore, fabrics made of fibers which have been produced by the process mentioned have a lower dye absorption than viscose fibers and have an increasingly harder grip with each wash. Textiles made from fibers that tend to fibrillate therefore do not meet the expectations of the customer from the outset with regard to comfort, which also worsens with every wash.

Efforts have already been made to reduce the tendency of cellulose threads made from solutions of tertiary amines to fibrillate.

For example, the international patent application WO-Al-92/14871 describes a process in which an effort is made to control the pH value in the different wash baths to reduce the tendency of the threads to fibrillate.

In international patent application WO-Al-92/07124, a method is disclosed in which the as yet undried fiber is treated with an aqueous solution or dispersion of a polymer with a cationically ionizable side chain.

According to WO-Al-95/02082, attempts are made to reduce fibrillation by controlling the distortion between the spinneret and the precipitation bath and the moisture in the air gap.

According to WO-94/24343, attempts are made to improve the freshly spun fibers by treating them with textile auxiliaries which contain at least two reactive groups and irradiating them with electromagnetic waves with regard to the tendency to fibrillation.

Finally, WO-Al-95/16063 describes a method in which a surfactant is added to the precipitation bath and / or the washing baths.

In the processes mentioned, however, fibers are obtained which, despite in some cases considerable interventions in the existing process for producing cellulosic fibers from solutions of cellulose in a tertiary amine oxide, still have a not inconsiderable tendency to fibrillate in comparison to the untreated fiber.

The published literature expresses itself inconsistently about the possibility of achieving advantageous effects in the production of fibers from cellulose solutions containing a tertiary amine oxide by using zinc chloride solutions. On the one hand, the Japanese patent publication J-07-189019 describes zinc chloride as an inorganic additive in the coagulation bath, which in combination with a water-soluble organic additive, an alkali or an acid leads to fibers with increased tensile strength and extensibility.

On the other hand, the magazine Khim. Volokna, volume 33 (5), (1991), pages 28 to 32, spoke of inherent problems which occur when zinc chloride is used as a solvent for cellulose, a strong degradation of the cellulose being observed.

After all, it has been known for a long time and in "Chemistry and Technology of Plastics", editors R. Houwink and A.J. Staverman, 4th improved and expanded edition, Leipzig 1963, Volume II: "Industrial production and properties of plastics", Academic Publishing Company

Geest & Portig K.-G. on pages 895 and 896 describes the production of "Vulkanfiber", a material which is produced by treating paper with an aqueous solution of zinc chloride with a concentration of 65 to 73% by weight of zinc chloride, the solution being 30 is warm up to 50 ° C. As the name suggests, the paper is vulcanized, i.e. the cellulose filaments are intensively glued together.

Experiments carried out by the inventor, in which the treatment just described was carried out on cellulosic fibers or fabrics, gave, as expected and feared, vulcanized products which are very brittle and are therefore unsuitable for textile applications.

Thus, there is still a need for an improved process for the production of cellulosic fibers without the disadvantages described or with at least significantly reduced disadvantages, the process sought in the existing ones Process for producing cellulosic threads by spinning a solution containing a tertiary amine oxide, washing, squeezing and drying as little as possible.

The object of the invention is therefore to provide a method which does not require changes to the known spinning, drawing and precipitation bath technology which is optimized at high cost and which eliminates or at least substantially reduces the disadvantages mentioned .

This object is achieved by a process for the production of cellulosic fibers by spinning a solution of cellulose in a tertiary amine oxide, possibly also containing water and possibly a stabilizer, precipitation, washing, squeezing and drying of the fibers, which is characterized in that is that the fibers are treated either after washing or after squeezing or after drying with a zinc chloride solution which may contain an acid at a temperature in the range from about 10 to 250 ° C., the Zinc chloride solution has a zinc chloride concentration in the range from about 30 to 70% by weight and an acid concentration in the range from 0 to about 10% by weight, after which the fibers are washed free of zinc chloride and, if appropriate, of acid, optionally squeezes and dries.

The zinc chloride and possibly an acid-containing solution is preferably aqueous.

Acetic acid has proven to be a preferred suitable acid. The addition of acid leads to an accelerated occurrence of the desired effects, so that the acid is preferably used when, for example, very high spinning speeds are required or when a fiber with a high titer is to be treated. One embodiment of the invention is that the fibers are treated in a single device with the zinc chloride and optionally an acid-containing solution. In principle, any device is suitable for this which is capable of completely providing the fiber with the treatment solution and of allowing the necessary mass and heat transport processes to take place sufficiently quickly. A bath is preferably used in which there is an acidic zinc chloride solution and in which the fibers are treated. To accelerate the necessary heat and mass transfer processes, turbulence or pressure waves can be generated in the bath, for example by ultrasound.

When treating the fibers in the bath mentioned, a zinc chloride concentration in the range from approximately 40 to 65% by weight, in particular in the range from approximately 50 to 60% by weight, an acid concentration in the range from approximately 0 to 5% by weight is preferred. , a temperature in the range of about 15 to 60 ° C, in particular in the range of about 20 to 40 ° C and a residence time of the fiber in the bath in the range of about 0.2 seconds to 10 minutes, in particular in the range of about 1 Seconds to 5 minutes. The treatment times will move in the direction of the lower limit of the time ranges mentioned, the higher the treatment temperatures are selected, whereas the longer the treatment times, the lower the treatment temperatures. Furthermore, under otherwise identical conditions, the fibers require a longer treatment time the higher their average degree of polymerization.

A further embodiment of the invention is that the fibers are first completely provided with the zinc chloride and possibly an acid-containing solution in the device already described, preferably in a bath, the bath temperature being in the range from about 20 to 25 ° C. lies. The same applies to the zinc chloride and acid concentration said. The fibers are then heat-treated outside of the device mentioned.

In principle, any heat transfer medium that is capable of allowing the necessary mass and heat transport processes to run sufficiently quickly is suitable for the heat treatment. A zone of warm or hot gas is preferably used, the fibers being blown with the gas. Basically, all gases or vapors can be used which are inert with cellulose, zinc chloride, water and possibly with the acid under the conditions according to the invention. Air is preferably used.

When treating the fibers in the embodiment just described, a temperature in the range from approximately 40 to 250 ° C., in particular in the ranges from approximately 150 to 250 ° C. and 40 to 70 ° C., is preferred for the heat treatment Dwell time of the fiber in the bath in the range of about 0.1 to 5 seconds, in particular in the range of about 0.5 to 3 seconds, and a dwell time of the fiber in the heat treatment zone in the range of about 0.1 to 10 seconds, especially in the range of about 0.2 to 5 seconds.

The treatment according to the invention can be carried out not only as already described at various points in the spinning process, but also on cellulosic fiber products, the fibers of which are obtained by spinning a solution of cellulose in a tertiary amine oxide which may also contain water and possibly a stabilizer , Cases, washing, squeezing and drying were obtained, the washed and optionally dried or unwashed fiber products with an acidic zinc chloride solution at a temperature in the range from about 10 to 250 ° C. are treated and the zinc chloride solution has a zinc chloride concentration in the range of about 30 to 70% by weight and an acid concentration in the Has a range from 0 to about 10% by weight, after which the fibers are washed free from zinc chloride and possibly from acid, if necessary squeezed and dried.

The invention is applicable to all linear and flat cellulosic fiber products. However, textile fabrics such as e.g. Fabrics, knitwear, nonwovens or laid scrims or yarns, fiber sheets or tapes are treated. Staple fibers, short cuts or flakes or mixed yarns made of cellulosic and synthetic fibers can also be treated.

Acetic acid has proven to be a preferred suitable acid. The addition of acid leads to an accelerated occurrence of the desired effects, so that the acid is preferably used when very high treatment speeds of the cellulosic fiber product are required or when a fiber product with a very dense structure is to be treated.

One embodiment of the invention consists in treating the cellulosic fiber products in a single device with the zinc chloride and possibly an acid-containing solution. In principle, any device is suitable for this, which is capable of completely providing the treatment solution to the cellulosic fiber products and of allowing the necessary mass and heat transport processes to take place sufficiently quickly. The cellulosic fiber products are preferably treated in a bath in which the zinc chloride solution, which may contain an acid, is present. To accelerate the necessary heat and mass transfer processes, turbulence or pressure waves can be generated in the bathroom, for example by ultrasound. A further embodiment of the invention consists in first providing the cellulosic fiber products completely with the zinc chloride and possibly an acid-containing solution having a temperature in the range from approximately 20 to 25 ° C. in the device already described and then heat-treating outside the device .

For the treatment of the cellulosic fiber products in a bath or in a bath with subsequent heat treatment, what has already been said applies with regard to the zinc chloride and acid concentrations, the temperatures, the mass and heat transfer media and processes and with regard to the fiber residence times. The treatment parameters for a specific cellulosic fiber product can easily be optimized by the person skilled in the art who knows the invention. If the conditions are otherwise the same, the fiber products will generally require a longer treatment time than individual fibers.

Wet scrubbing equipment

The wet scrub test apparatus shown schematically in FIG. 1 is used to measure the tendency to fibrillation of individual threads. In order to assess the tendency to fibrillation of the fiber products already described, the wet abrasion test is carried out with threads which have been removed from the products mentioned. The wet abrasion test equipment essentially consists of the elements (1) to (6), which are explained in the following: The thread (2) is fixed in a PVC block (1). The scouring load is generated in that the thread (2) is guided over an arrangement rotating at 25 revolutions per minute, which consists of a 2.5 mm thick ceramic rod (4) attached to a glass rod (5) with a diameter of 6 mm Diameter exists. By dropping with water (3) by a weight (6) of 3 g tightened thread kept wet. The wet scrub test was run for 1 minute. The defined and reproducible fibrillation produced with the described apartment was assessed on a scale with the marks 1 to 6 by microscopic evaluation of the scrubbed, approximately 3 mm long fiber area.

To assess the fibrillation caused by scrubbing, it has proven to be advantageous to introduce the terms primary and secondary fibrillation.

Primary fibrillation means that fibrils are only observed on the fiber surface.

Secondary fibrillation means that the fibrils are also observed in the deeper layers of the filaments. The more secondary fibrillation progresses, the longer and thicker the fibrils become.

A grade scale from 1 to 6 was defined using the terms just described. The means

Grade 1 no fibrils,

Grade 2 weak primary fibrillation,

Grade 3 strong primary fibrillation,

Grade 4 weak secondary fibrillation,

Grade 5 strong secondary fibrillation and

Grade 6 the damage to the entire fiber surface

Primary and secondary fibrillation, such as those on untreated

Fibers is observed.

5 fibers each, which had been subjected to a specific treatment according to the invention, were wet-scrubbed and evaluated according to the grading scale just described. The scores of the 5 fibers were combined to an arithmetic mean. The notes given below give the just described Mean again. As previously stated, the wet scrub test was run for 1 minute. This time turned out to be suitable for fibers with a titer of 75 dtex and with 50 filaments, which are used throughout in the examples. The wet scrubbing time required for a reliable result depends on the titer: the larger the titer, the longer the specified time.

Dyeing recipe, dyeing conditions and measurement of the color depth

An aqueous recipe is used that consists of the dyes

Levafix navy blue E-4 Ra (6.0% by weight) and Levafix gold yellow

(1.2% by weight), the anti-wrinkle Perilan VF (4.0 g / 1) and the

Salts sodium sulfate (50.0 g / 1) and sodium carbonate (15.0 g / 1).

The dyeing of the fabrics takes 1 hour and is carried out at 50 ° C and a liquor ratio of 1: 160. A paddle serves as the coloring unit. This is followed by a 20 minute boiling soap with Perilan VF (4.0 g / 1) and the detergent Kieralon Jet B.

The brightness, which is determined with the Minolta Chroma Meter, is used to measure the color depth.

Washing conditions

The stability of the tendency to fibrillation, color depth, levelness and grip against changes when washing in the washing machine was tested with 10 washes in a household washing machine (Miele W 716) with the detergent Fewa supra (60 ml at 1 kg load). Each wash cycle consisted of a pre-wash (35 ° C, 15 minutes), a main wash (40 ° C, 60 minutes), three rinse cycles (15 minutes each) and from the spin cycle (2 minutes at 800 tours / minute).

Surprisingly, the fibers or fiber products treated according to the invention show a significantly reduced tendency to fibrillation with notes between 2 and 3, have no gray haze before washing in the washing machine or after 10 washes, and are distinguished by a pleasantly soft handle, which itself does not become harder after washing 10 times in the washing machine. Furthermore, the fiber products treated and dyed in accordance with the invention are surprising in that they have a higher level of levelness and a significantly deeper dyeability, the properties just mentioned not decreasing even after washing 10 times.

The invention is not restricted to the use of a certain average degree of polymerization DP of the cellulose raw material. Rather, cellulose or cotton linters with a DP in the range from about 400 to 7000 can be used individually or as a mixture of celluloses with a high and low degree of polymerization.

Furthermore, the invention is not restricted to a specific stabilizer in the spinning solution. Rather, all additives suitable as stabilizers can be used, e.g. Pyrrogallol, gallic acid or propyl gallate.

Furthermore, the invention is not restricted to a specific cellulosic fiber type, but encompasses all cellulosic fiber types such as e.g. Continuous filaments or fibers, and staple or short cut fibers, flakes or blended yarns made of cellulosic and synthetic fibers.

The invention is also not limited to the fact that the fibers or a textile fabric produced therefrom under a ner certain mechanical tension must stand. Rather, the fibers or the textile fabrics produced therefrom can be used without mechanical tension or in a state of mechanical tension.

Finally, the invention is not restricted to the use of a certain tertiary amine oxide, but preferably uses N-methylmorpholine-N-oxide (NMMO).

The invention is further illustrated by the following examples. The zinc chloride used was purchased from Fluka and has a purity of 98%.

Example 1:

A desized and dried fabric made of fibers (75 dtex, f 50) spun from an NMMO-containing cellulose solution is treated for 8 minutes in a bath containing a solution of 55% by weight zinc chloride in water. The bath has a temperature of 22 ± 3 ° C. The fabric is then squeezed, washed and dried in a known manner.

The fabric treated and dyed in this way shows no gray haze and is further characterized by a 25% deeper staining, a softer feel and a very high level of levelness in comparison to untreated fabric which has a clear gray haze and whose levelness is desirable leaves little. The tendency to fribrillation of fibers taken from the treated tissue was given a rating of 2, while untreated fibers were rated 6.

After 10 washes, the treated fabric shows no gray haze and is still characterized by a high level of levelness, an unchanged soft feel and a 25% deeper staining compared to the untreated fabric, the handle of which is significantly harder. The tendency to fribrillation of fibers taken from the treated tissue was given a grade of 2-3, while untreated fibers were rated 6.

Example 2:

A fiber (75 dtex f 50) spun, precipitated, washed and squeezed from an NMMO / cellulose solution is treated in a bath which contains a solution of 60% by weight zinc chloride in water. The solution has a temperature of 22 + 3 ° C. The fiber speed and the dimensions of the treatment bath are adjusted so that a fiber residence time of about 1.5 ± 0.5 seconds results. The fiber is then drawn through a hot air zone and blown with hot air at 225 ± 25 ° C. The fiber speed and the dimensions of the hot air zone are adjusted so that a fiber residence time of about 2 seconds results. Finally, the fiber is squeezed, washed and dried in a known manner. The tendency to fribrillation of fibers treated in this way was given a grade of 2-3, while untreated fibers were rated 6.

Example 3:

A fiber spun, precipitated, washed, squeezed and dried from an NMMO / cellulose solution (75 dtex f 50) is treated in a 22 + 3 ° C. bath containing a solution of 50% by weight zinc chloride in water. The fiber speed and the dimensions of the treatment bath are set in such a way that a fiber residence time of about 1 + 0.5 seconds results. The fiber is then placed in a warm air zone conducted and blown with 55 + 5 ° C warm air. The fiber speed and the dimensions of the warm air zone are set such that a fiber dwell time of about 2 seconds results. The fiber is then squeezed, washed and dried in a known manner. The tendency to fribrillation of fibers treated in this way was rated 2-3, while untreated fibers were rated 6.

Example 4:

A fiber spun, precipitated, washed, squeezed and dried from an NMMO / cellulose solution (75 dtex f 50) is treated in a 22 ± 3 ° C. bath containing a solution of 55% by weight zinc chloride in water. The fiber speed and the dimensions of the treatment bath are set so that a fiber residence time of about 2 minutes results. The fiber is then squeezed, washed and dried in a known manner. A fabric is produced from the fiber treated in this way, which shows the same properties as the treated fabric of Example 1.

Claims

Process for the production of cellulose fibers and cellulosic fiber products

1. A process for the production of cellulosic fibers by spinning a solution of cellulose in a tertiary amine oxide, optionally containing water and possibly a stabilizer, precipitation, washing, squeezing and drying, characterized in that the fibers are either washed according to the ¬ or, after squeezing, or after drying with a possibly containing an acidic zinc chloride solution at a temperature in the range of about 10 to 250 ° C, the zinc chloride solution having a zinc chloride concentration in the Has a range from about 30 to 70% by weight and an acid concentration in the range from 0 to about 10% by weight, after which the fibers are washed free from zinc chloride and possibly from acid, if necessary squeezed, and dried.

2. The method according to claim 1, characterized in that the solution containing the zinc chloride and optionally an acid is aqueous.

3. The method according to claim 1 or 2, characterized in that the acid is acetic acid.

4. The method according to one or more of claims 1 to 3, characterized in that the fibers are treated in a bath in which there is an acidic zinc chloride solution.

5. The method according to claim 4, characterized in that the zinc chloride has a concentration in the range of about 40 to 65 wt.%.

6. The method according to claim 5, characterized in that the zinc chloride has a concentration in the range of about 50 to 60 wt.%.

7. The method according to one or more of claims 4 to 6, characterized in that the acid has a concentration in the range of 0 to about 5 wt.%.

8. The method according to one or more of claims 4 to 7, characterized in that the temperature of the zinc chloride solution which may contain an acid is in the range of about 15 to 60 ° C.

9. The method according to claim 8, characterized in that the temperature of the zinc chloride solution which may contain an acid is in the range from about 20 to 40 ° C.

10. The method according to one or more of claims 4 to 9, characterized in that the residence time of the fiber in the bath is in the range of about 0.2 seconds to 10 minutes.

11. The method according to claim 10, characterized in that the residence time of the fiber in the bath is in the range of about 1 second to 5 minutes.

12. The method according to one or more of claims 1 to 3, characterized in that the fibers are first treated in a zinc chloride and optionally an acid-containing bath, which has a temperature in the range of about 20 to

Has 25 ° C, and then heat treated outside the bath.

13. The method according to claim 12, characterized in that the heat treatment of the fibers takes place by blowing with a gas.

14. The method according to claim 13, characterized in that the gas is air.

15. The method according to one or more of claims 12 to 14, characterized in that the temperature of the gas is in the range from about 40 to 250 ° C.

16. The method according to claim 15, characterized in that the temperature of the gas is in the range of about 150 to 250 ° C.

17. The method according to one or more of claims 12 to 15, characterized in that the temperature of the gas is in the range from about 40 to 70 ° C.

18. The method according to claim 12, characterized in that the fiber residence time in the bath in the range of about 0.1 to

5 seconds.

19. The method according to claim 18, characterized in that the fiber residence time in the bath in the range of about 0.5 to

3 seconds.

20. The method according to claim 12 to 17, characterized in that the fiber residence time in the heat treatment zone is in the range of about 0.1 to 10 seconds.

21. The method according to claim 20, characterized in that the fiber residence time in the heat treatment zone is in the range of about 0.2 to 5 seconds.

22. A process for the production of cellulosic fiber products, the fiber products being produced from fibers which were obtained by spinning a solution of cellulose, possibly still containing water and possibly a stabilizer, in a tertiary amine oxide, precipitating, washing, squeezing and drying , characterized in that washed and optionally dried or unwashed cellulosic fiber products are treated with a zinc chloride solution which may contain an acid at a temperature in the range from about 10 to 250 ° C., the zinc chloride solution being used has a zinc chloride concentration in the range from about 30 to 70% by weight and an acid concentration in the range from 0 to about 10% by weight, after which the fiber products are washed, optionally squeezed, and dried.

23. The method according to claim 22, characterized in that the cellulosic fiber products are textile fabrics or yarns, fiber sheets or ribbons.

24. The method according to claim 22 or 23, characterized in that the zinc chloride and possibly an acid-containing solution is aqueous.

25. The method according to one or more of claims 22 to 24, characterized in that the acid is acetic acid.

26. The method according to one or more of claims 22 to 25, characterized in that the fiber products are treated in a bath in which there is an acidic zinc chloride solution.

27. The method according to claim 22 to 25, characterized in that the fiber products are first treated in a zinc chloride and possibly an acid-containing bath, the one Has temperature in the range of about 20 to 25 ° C, and then be heat treated.