WO2005080660A1 - Method for producing non-wovens, a corresponding non-woven and the production thereof - Google Patents

Abstract

The invention concerns a method for producing non-wovens during which a cellulose carbamate solution is spun by means of extrusion through a nozzle block having a number of openings into a precipitation bath to form a number of endless threads and, afterwards, is mingled by subjecting it to a flow of a gaseous medium and/or fluid. The invention also concerns a non-woven of the aforementioned type and the use thereof.

Description

 Process for the production of nonwovens, nonwoven and its use

The invention relates to a process for the production of nonwovens, in which a cellulose carbamate solution is spun by means of extrusion through a nozzle block containing a plurality of openings into a coagulation bath to form a plurality of continuous filaments which are subsequently intermingled with gaseous medium and / or fluid. The invention also relates to such a nonwoven fabric and to the use thereof.

Nonwovens are textile fabrics in which the cohesion of the fibers is ensured not by weaving or knitting, but by interlocking and sometimes also gluing after the fibers have been swirled. Because of the wide range of possible uses and the low production costs, nonwovens production continues to show high annual rates Growth rates. The advantages of these nonwoven materials lie in particular in the high moisture absorption, the high variability of density and thickness as well as the extensive surface anisotropy, which results in the numerous possible uses, e.g. in medicine (surgical drapes, sheets, wound coverings, gauze, cotton pads etc.) for hygiene products, as wipes in household and industry, as decorative nonwovens (tablecloths, serviettes, curtains), inlay nonwovens in the clothing industry and for numerous technical applications (eg insulating mats in the construction industry).

In principle, the formation of fleece from short fibers, staple fibers or continuous filaments is possible. As

"Spunbonding" or "spunlacing" methods of forming nonwovens from continuous fibers have the advantage that the fibers are spun and laid to form nonwovens in one process and are the subject of this invention. A large number of fiber-forming polymers can be used as the starting material for the nonwovens. Nonwovens made from continuous filaments are preferably made from synthetic fibers such as polyester, polyacrylonitrile or polypropylene. Viscose fibers are preferably used as short or staple fibers for the manufacture of nonwovens.

Since the viscose process, with which the majority of the cellulose regenerated fibers are still produced, is associated with considerable environmental pollution and high investment costs, extensive efforts have been made for several years to replace the viscose process with alternative processes. For example, the process was developed to produce cellulose tablets by precipitating a solution of cellulose in a system composed of N-methylmorpholine-N- To produce oxide (NMMNO) and water (US 3,767,756, DE 28 30 685), which can also be used for the production of nonwovens products (WO 00/18991, WO 98/07911). In the so-called “Bemsliese process”, cotton linters are spun using the Cuproammonium process and processed into nonwovens (US Pat. No. 3,833,438). Both processes also have the advantage that the nonwovens products can be made from continuous filaments in a direct process.

A process which has been known for a long time for the production of molded articles from regenerated cellulose consists in the precipitation of a solution of cellulose carbamate (EP-A-57 105, EP-A 178 292) which is obtained by reacting cellulose with urea with thermal splitting of the urea into isocyanic acid and Ammonia and reaction of the isocyanic acid with the OH groups of the cellulose is formed. Cellulose carbamate is soluble in cold, dilute sodium hydroxide solution and can be regenerated back to cellulose in heated sodium hydroxide solution.

The object of the present invention was therefore to provide a process for producing nonwovens from cellulose carbamate in a continuous process with good product properties. Another task was that the process meets the requirements in terms of low investment and production costs and low environmental impact.

This object is achieved by the method with the features of claim 1 and the nonwovens with the features of claims 21 and 23. The use of the nonwovens according to the invention is described in claims 28 to 32. The further dependent claims show advantageous developments on.

According to the invention, there is provided a process for producing nonwovens in which a cellulose carbamate solution is extruded through at least 20 openings, i.e. Nozzles containing the nozzle block is spun into a coagulation bath to form a plurality of continuous filaments, which are then swirled by flow with gaseous medium and / or fluid to form the nonwoven.

Surprisingly, it was shown that threads spun using the carbamate process can be processed into nonwovens in a continuous process.

The number of on the nozzle block, i.e. A rectangular area, the length of which is large compared to the width, arranged openings depends on the width and thickness of the desired product and is preferably at least 10,000.

The openings of the nozzle block are particularly preferably arranged in an array. However, it is also possible that the openings of the nozzle bar are arranged linearly. The ratio of length to diameter (L / D ratio) of the nozzles is preferably between 1 and 20.

In a preferred embodiment of the method, the continuous filaments are spun vertically from the bottom up into the precipitation bath.

It is further preferred that the continuous filaments are spun in the wet state. After spinning, the continuous filaments are preferably guided downwards in a slit-shaped funnel, the intermingling with the gaseous medium and / or fluid taking place at the outlet of the funnel. In order to improve the intermingling of the continuous filaments, it is further preferred to carry out a vibrating movement of the funnel.

Air and / or water are preferably used as the gaseous medium and / or fluid.

It is further preferred that the continuous threads are deposited on a conveyor belt after the intermingling. A further intermingling of the continuous threads is preferably realized by shaking the conveyor belt.

A cellulose carbamate solution is preferably used which contains a cellulose carbamate content of at least 6 to 12, preferably 7 to 9% by weight, based on the solution.

The precipitation bath preferably contains sulfuric acid with a concentration of 50 to 200 g / 1, particularly preferably 70 to 100 g / 1 and 100 to 300 g / 1, particularly preferably 150 to 200 g / 1 sodium sulfate.

In a further advantageous embodiment variant of the method, the nonwoven fabric is washed, pressed and dried following the steps described above. The washing can preferably be carried out by a high pressure water jet.

The cellulose carbamate is preferably regenerated to cellulose in a regeneration bath. It is particularly preferred that the cellulose carbamate is regenerated to cellulose in a regeneration bath from 0.3 to 1% by weight sodium hydroxide in water at a temperature of 60 to 95 ° C. This makes it possible to produce nonwovens from regenerated cellulose. In a first advantageous variant, it is possible to carry out the regeneration between extrusion and swirling. Another preferred variant provides that the regeneration is carried out after the swirling.

According to the invention, a nonwoven fabric is also provided from a random scrim made of continuous filaments made of cellulose carbamate. It is preferred that the nonwoven fabric according to the invention can be produced by the method according to one of claims 1 to 16.

According to the invention, a nonwoven fabric is also made from a

Tangled scrim made of continuous filaments made of regenerated cellulose. The regenerated cellulose preferably has a residual nitrogen content (residual N content) of 0.3 to 0.5, particularly preferably 0.1 to 1.2.

The nonwoven fabric has a pore structure with a preferred porosity of 1 to 10%.

It is further preferred that the nonwoven fabric has a specific inner surface between 20 and 50 m ² / cm ³ , measured by means of small angle x-ray scattering (SAXS).

It is particularly preferred that the invented Nonwoven according to the invention can be produced by the method according to one of claims 17 to 20.

The nonwovens according to the invention are preferably used in medicine, in particular as surgical drapes, bed sheets, wound coverings, gauze or cotton pads. The nonwovens can also be used as hygiene materials or as wipes in the household. A further field of application of the nonwovens according to the invention is decorative nonwovens, in particular tablecloths, napkins or curtains, and insert nonwovens in the clothing industry.

Another use relates to insulating mats and reinforcement fleeces, e.g. as a replacement for glass fiber fleeces, in the construction industry.

The subject according to the invention is intended to be explained in more detail with reference to the following figures of the following examples, without restricting it to the embodiment variants described herein.

1 shows a schematic representation of the process sequence according to the invention.

Fig. 2 shows a slot-shaped funnel according to the invention, at the exit of which the swirling takes place.

The basic sequence of the method is shown in FIG. 1. Here, the spinning solution 1 is extruded into a precipitation bath 4 by means of a spinning pump 2 by means of a nozzle bar 3, which contains a large number of nozzles. Spinning is carried out vertically from the bottom upwards into the precipitation bath. Be about 5 pulleys the fibers are drawn off in a horizontal direction. A first wash bath and a stretching section can optionally be located on this route. Another deflection roller 6 then leads the fiber bundle down into a slit-shaped funnel 7, at the exit of which the fiber bundle is flown by air or water on both sides. The fibers which are swirled in this way are deposited on the conveyor belt 8 located underneath, with further swirling being effected transversely to the running direction by shaking the depositing device or the conveyor belt. The belt runs through a washing bath with a washing nozzle 9, which can also be realized by a water jet under high pressure, and thus leads to a further solidification of the material in the sense of spun lacing. The conveyor belt consists of a wide-meshed network, preferably made of metal, which ensures that the washing liquid runs off quickly. The material can then be dried in appropriate drying devices. However, the water can also be squeezed out by a pair of rollers, which at the same time enables the nonwoven to be compressed.

Figure 2 shows the structure of a slot-shaped funnel according to the invention. The fiber can be introduced into said funnel via the fiber inlet 1. The transport of the fiber through the funnel is made possible by a Venturi nozzle, which implements the water jet principle. Through the opening 3 there is the supply of water, air or a mixture thereof which, due to the Venturi profile, flows past the channel 4 in such a way that a vacuum is created which transports the fiber through the channel 4. The fiber exit is located at the lower end 5 of the funnel, from where the continuous filaments then continue. can be transported.

example 1

800 g of pulp with a DP (uoχam) of 520 become intensive in a kneader with 3200 g of a solution consisting of 12% by weight NaOh, 30% by weight urea and 58% by weight water at 25 ° C. for 1 hour mixed and then matured at 23 ° C for 48 h to a DP _(C uoxam) of 300. The moist alkali cellulose is at room temperature in a 5 1 kneader with 1200 g of solid crystalline urea for 30 min. kneaded. The temperature of the kneader is then raised to 140 ° C. and the water present is drawn off. After reaching a product temperature of 140 ° C, the mass is kneaded for a further 120 min and then discharged from the kneader. To obtain the pure cellulose carbamate, the dry crumbly mass is washed 3 times with deionized water at a liquor ratio of 1:16, suctioned off over a frit and then at

Room temperature dried. This loosened and crumbly product had a nitrogen content of 3.0% and a DP ( _Cu oxam) of 290. It was in a dissolving kettle with a stirrer at -5 to + 2 ° C to a solution with 7.5% cellulose and 9% sodium hydroxide solution dissolved, the solution filtered, deaerated under vacuum and spun into a spin bath containing 140 g / 1 sulfuric acid and 240 g / 1 sodium sulfate at 25 ° C. to form filament yarns with 1000 capillaries, via a roller system to the swirling nozzle (Fig. 2) out there in one

Swirling water flow and continuously deposited on a conveyor belt to form a fleece, washed and dried. The basis weight of the fleece was 100 g / m ² . Example 2

800 g of pulp with a DP ( _CuoX am) of 520 are _mixed in a kneader with 3200 g of a solution consisting of 12% by weight NaOh, 30% by weight urea and 58% by weight

Water mixed intensively for 1 h at 25 ° C and then pre-ripened at 23 ° C for 48 h to a DP ( _CU oxam) of 300. The moist alkali cellulose is at room temperature in a 5 1 kneader with 1200 g of solid crystalline urea for 30 min. kneaded. The temperature of the kneader is then raised to 140 ° C. and the water present is drawn off. After reaching a product temperature of 140 ° C, the mass is kneaded for a further 120 min and then discharged from the kneader. To obtain the pure cellulose carbamate, the dry crumbly mass is washed 3 times with deionized water at a liquor ratio of 1:16, suction filtered over a frit and then dried at room temperature. This loosened and crumbly product had a nitrogen content of

3.0% and a DP ( _Cu oxam) of 290. It was dissolved in a dissolving kettle with a stirrer at -5 to + 2 ° C. to a solution with 7.5% cellulose and 9% sodium hydroxide solution, the solution was filtered under vacuum deaerated and spun into a spinning bath containing 90 g / 1 sulfuric acid and 240 g / 1 sodium sulfate at 25 ° C to filament yarns with 1000 capillaries, drawn by a roller system and a drafting device 25%, led to the swirling nozzle (Fig. 2), there in swirled in a stream of water and continuously on one conveyor belt to one

Fleece deposited, washed with a spray nozzle under high pressure and dried. The basis weight of the fleece was 75 g / m ² . Example 3

800 g of pulp with a DP ( _Cu oxam) of 520 are mixed in a kneader with 3200 g of a solution consisting of 12% by weight NaOh, 30% by weight urea and 58% by weight water at 25 ° C. for 1 hour mixed intensively and then matured at 23 ° C for 48h on a DP ( _u oxam). The moist alkali cellulose is kneaded at room temperature in a 5 l kneader with 1200 g of solid crystalline urea for 30 minutes. The temperature of the kneader is then raised to 140 ° C. and the water present is drawn off. After reaching a product temperature of 140 ° C, the mass is kneaded for a further 120 min and then discharged from the kneader. To obtain the pure cellulose carbamate, the dry crumbly mass is washed 3 times with deionized water at a liquor ratio of 1:16, suction filtered over a frit and then dried at room temperature. This loosened and crumbly product had a nitrogen content of 3.0% and a DP (cuo m) of 290. It was in a dissolving kettle with an agitator at -5 to + 2 ° C to a solution with 7.5% cellulose and 9% Sodium hydroxide solution dissolved, the solution filtered, deaerated under vacuum and spun into a spinning bath containing 140 g / 1 sulfuric acid and 240 g / 1 sodium sulfate at 25 ° C. to form filament yarns with 1000 capillaries, via a roller system to the swirling nozzle (FIG. 2) guided, swirled in a stream of water and continuously deposited on a conveyor belt to form a fleece. The fleece is passed through a 0.5% sodium hydroxide solution, then washed and dried. The basis weight of the fleece was 85 g / m ² .

Claims

claims 1. A process for the production of nonwovens, in which a cellulose carbamate solution is spun by means of extrusion through a nozzle block containing at least 20 openings into a coagulation bath to form a plurality of continuous filaments which are subsequently intermingled with gaseous medium and / or fluid. 2. The method according to claim 1, characterized in that a nozzle block with at least 10,000 openings is used. 3. The method according to any one of claims 1 or 2, characterized in that the openings of the nozzle block are arranged linear or array-like. 4. The method according to any one of the preceding claims, characterized in that the ratio of the length to the diameter of the nozzles is from 1 to 20. 5. The method according to any one of the preceding claims, characterized in that the continuous filaments are spun vertically from the bottom up into the precipitation bath. 6. The method according to any one of the preceding claims, characterized in that the continuous filaments are spun in the wet state. 7. The method according to any one of the preceding claims, characterized in that the continuous filaments are guided downwards after spinning in a slot-shaped funnel, with the swirling with the gaseous medium and / or fluid taking place at the outlet of the funnel. 8. The method according to the preceding claim, characterized in that a further swirling of the continuous threads is achieved by shaking the funnel. 9. The method according to any one of the preceding claims, characterized in that the gaseous measurement dium and / or fluid air and / or water are used. 10. The method according to any one of the preceding claims, characterized in that the continuous filaments are deposited on a conveyor belt after the intermingling. 11. The method according to the preceding claim, characterized in that a further intermingling of the continuous threads is achieved by shaking the conveyor belt. 12. The method according to any one of the preceding claims, characterized in that the cellulose carbamate is dissolved in sodium hydroxide solution. 13. The method according to the preceding claim, characterized in that the cellulose carbamate portion of the cellulose carbamate solution is at least 6 to 12, in particular 7 to 9 wt .-%, based on the solution. 14. The method according to any one of the preceding claims, characterized in that the precipitation bath from Sulfuric acid with a concentration of 50 to 200 g / 1, in particular 70 to 100 g / 1 and 100 to 300 g / 1, in particular 150 to 200 g / 1 sodium sulfate. 15. The method according to any one of the preceding claims, characterized in that the nonwoven fabric is then washed, pressed and dried. 16. The method according to the preceding claim, characterized in that the washing is carried out by a high pressure water jet. 17. The method according to any one of the preceding claims, characterized in that the cellulose carbamate is regenerated to cellulose in a regeneration bath. 18. The method according to the preceding claim, characterized in that the regeneration bath consists of 0.3 to 1 wt .-% sodium hydroxide in water and the regeneration takes place at a temperature of 60 to 95 ° C. 19. The method according to the preceding claim, characterized in that the regeneration is carried out between extrusion and fluidization. 20. The method according to claim 18, characterized in that the regeneration is carried out after the production of the nonwoven fabric. 21. Nonwoven fabric made of a random scrim made of cellulose carbamate filaments. 22. Nonwoven fabric according to claim 21, characterized in that the nonwoven fabric can be produced by the method according to one of claims 1 to 16. 23. Nonwoven fabric made of a random scrim made of continuous filaments made of regenerated cellulose. 24. Nonwoven fabric according to claim 23, characterized in that the residual N content is from 0.3 to 0.5%, in particular 0.1 to 0.2%. 25. Nonwoven fabric according to one of claims 23 or 24, characterized in that the nonwoven fabric has a pore structure with a porosity of 1 to 10%. 26. Nonwoven fabric according to one of claims 23 to 25, characterized in that the nonwoven fabric has a specific inner surface between 20 and 50 m ² / cm ³ , measured by means of small angle x-ray scattering (SAXS) , 27. Nonwoven fabric according to one of claims 23 to 26, characterized in that the nonwoven fabric can be produced by the method according to one of claims 17 to 20. 28. Use of the nonwovens according to one of claims 21 to 27 in medicine, in particular as surgical drapes, bed sheets, wound coverings, gauze or cotton pads. 29. Use of the nonwovens according to one of claims 21 to 27 as hygiene materials or as wipes in the household. 30. Use of the nonwovens according to one of claims 21 to 27 as decorative nonwovens, in particular tablecloths, serviettes or curtains. 31. Use of the nonwovens according to one of claims 21 to 27 as insert nonwovens in the clothing industry. 32. Use of the nonwovens according to one of claims 21 to 27 as reinforcing nonwovens and insulating mats in the construction industry.