DE102004007618A1 - Process for the production of nonwovens, nonwoven fabric and its use - Google Patents

Abstract

The invention relates to a process for the production of nonwovens, in which a cellulose carbamate solution is spun by extrusion through a die block containing a plurality of openings in a precipitation bath to form a plurality of continuous filaments, which is subsequently fluidized by influx with gaseous medium and / or fluid. Likewise, the invention relates to such a nonwoven fabric and its use.

Description

The Invention relates to a process for the production of nonwovens, in which a cellulose carbamate solution by means of Extrusion through a multiple openings containing nozzle block in a felling bath too several endless threads is spun, which is then by gushing with gaseous medium and / or fluid is fluidized. Likewise, the invention relates to a such nonwoven fabric and its use.

nonwovens are textile fabrics, where cohesion of the fibers is not achieved by weaving or knitting, but by entanglements and sometimes also gluing after swirling the Ensures fibers becomes. Because of the versatility and low production costs nonwovens production continues to show high annual growth rates on. The advantages of these nonwoven materials are in particular the high moisture absorption, the high variability of density and thickness as well as the extensive surface anisotropy, from which the numerous uses result, e.g. in medicine (surgical drapes, sheets, wound dressings, gauze, Cotton pads, etc.) for Hygiene products, as wipes in household and industry, as decorative nonwovens (tablecloths, Napkins, curtains), Nonwovens in the clothing industry and for many technical applications (e.g., insulation mats in the construction industry).

in principle is the nonwoven formation of short fibers, staple fibers or continuous filaments possible. The as spunbonding or spunlacing The nonwoven formation of continuous fibers have the advantage that the spinning fibers and laying to nonwovens in one process, and are the subject of this invention. As starting material for the nonwovens a variety of fiber-forming polymers can be used. Nonwovens off Continuous filaments are preferably made of synthetic fibers such as polyester, Polyacrylonitrile or polypropylene produced. Viscose fibers are preferably used as short or staple fibers for nonwoven production.

Since the viscose process, which still produces most of the cellulose regenerated fibers, involves considerable environmental pollution and high investment costs, extensive efforts have been made for several years to replace the viscose process with alternative processes. Thus, for example, the process has been developed for preparing shaped cellulose articles by precipitating a solution of cellulose in a system of N-methylmorpholine-N-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" method, cotton linters are spun by the cuproammonium process and processed into nonwovens ( US 3,833,438 ). In addition, both methods have the advantage that the nonwovens products can be produced from continuous filaments in a direct process.

One long known method for the production of moldings Regenerated cellulose consists in precipitating a solution of Cellulose carbamate (EP-A-57 105, EP-A 178 292), which by reacting cellulose with urea upon thermal decomposition of the urea into isocyanic acid and ammonia and reaction of isocyanic acid is formed with the OH groups of the cellulose. cellulose is more diluted in cold Sodium hydroxide solution and can be heated Sodium hydroxide be regenerated back to cellulose.

task It was therefore the object of the present invention to provide a process for the preparation nonwovens made of cellulose carbamate in a continuous process to provide with good product properties. Another task was that the procedure complied with the low investment and production costs and low environmental impact is sufficient.

These The object is achieved by the method having the features of the claim 1 and the nonwoven fabrics with the features of claims 21 and 23 solved. The Use of the nonwoven fabrics according to the invention is in the claims 28 to 32 described. The further dependent claims show advantageous developments.

According to the invention is a Process for the production of nonwovens provided in which a Cellulose solution by extrusion through at least 20 orifices, i. Nozzles containing nozzle block in a felling bath to several endless threads which is then spinned by gaseous medium and / or fluid are fluidized to form the nonwoven fabric.

Surprised could be shown that even after the carbamate spun Threads in a continuous process to nonwovens are processed can.

The number of openings arranged on the nozzle block, ie a rectangular area whose length is large in relation to the width, is dependent of the width and thickness of the intended product and is preferably at least 10,000.

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

In a preferred embodiment of the Procedure become the endless threads Spun vertically from bottom to top in the precipitation bath.

Farther it is preferred that the spinning of the filaments in the wet Condition occurs.

To spinning, the filaments are preferably in a slit-shaped funnel after guided down, wherein at the outlet of the funnel the turbulence with the gaseous medium and / or Fluid takes place. To improve the turbulence of the filaments is It further prefers a shaking motion of the funnel.

When gaseous Medium and / or fluid are preferably used air and / or water.

Farther it is preferred that the filaments after the turbulence on be stored a conveyor belt. Preferably, it is through shaking the conveyor belt realized a further swirling of the endless threads.

Preferably becomes a cellulose carbamate solution used, which has a cellulose carbamate content of at least 6 to 12, preferably 7 to 9 wt .-%, based on the solution contains.

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

In a further advantageous embodiment of the method The nonwoven fabric will follow the previously described steps washed, pressed and dried. The washing may preferably take place through a high pressure water jet.

Preferably the cellulose carbamate becomes cellulose in a regeneration bath regenerated.

Especially it is preferred that the cellulose carbamate in a regeneration from 0.3 to 1% by weight of sodium hydroxide in water at one temperature from 60 to 95 ° C is regenerated to cellulose. This makes it possible Producing nonwovens from regenerated cellulose. In a first advantageous variant it is possible perform the regeneration between extrusion and turbulence. A Another preferred variant provides that the regeneration after the swirling performed becomes.

According to the invention as well a nonwoven fabric made from a random knit of cellulose carbamate. It is preferred that the nonwoven fabric according to the invention by the method according to one of the claims 1 to 16 can be produced.

Also according to the invention a nonwoven fabric made of a random knit of regenerated cellulose filaments provided. The regenerated cellulose preferably has a residual nitrogen content (residual N content) from 0.3 to 0.5, more preferably 0.1 to 1.2.

Of the Nonwoven fabric has a pore structure with a preferred porosity of 1 up to 10%.

Furthermore, it is preferred that the nonwoven fabric have a specific internal surface area between 20 and 50 m ² / cm ³ as measured by small angle x-ray scattering (SAXS).

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

use find the nonwovens according to the invention preferably in medicine, in particular as surgical drapes, sheets, wound dressings, Gauze or cotton pads. Likewise, the nonwovens are also used as hygiene substances or as wipes can be used in the household. Another field of application of the nonwovens according to the invention are decorative nonwovens, especially tablecloths, napkins or curtains as well as inlaid nonwovens in the clothing industry.

A further use relates to insulating mats and reinforcing nonwovens, e.g. as replacement for Glass fiber fleece, in the construction industry.

Based the following figures of the following examples, the subject invention be explained in more detail, without limiting it to the embodiments described herein.

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

2 shows an inventive slit-shaped funnel, at its output the swirling takes place.

The basic procedure of the method is in 1 shown. This is the spinning solution 1 via a spinning pump 2 by means of a nozzle bar 3 , which contains a plurality of nozzles, in a precipitation bath 4 extruded. The spinning takes place vertically from bottom to top in the precipitation bath. About pulleys 5 The fibers are pulled off in a horizontal direction. Optionally, a first wash bath and a stretch can be located on this route. Another deflection roller 6 then leads the fiber bundle down into a slot-shaped funnel 7 , at the output of the fiber bundle is flown on both sides of air or water. The fibers so swirled on the underlying conveyor belt 8th filed, wherein by shaking the depositing device or the conveyor belt transversely to the direction of further turbulence takes place. The tape passes through a washing bath with a washing nozzle 9 , which can also be realized by a high pressure water jet, and thus leads to a further solidification of the material in the sense of spun-lacing. The conveyor belt consists of a wide-meshed, preferably made of metal, which ensures a rapid drainage of the washing liquid. Subsequently, the material can be dried in appropriate drying devices. But the water can also be squeezed out by a pair of rollers, which at the same time a compression of the nonwoven fabric can be achieved.

2 shows the structure of a slot-shaped funnel according to the invention. About the fiber inlet 1 The fiber can be introduced into said funnel. 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 takes place the supply of water, air or a mixture thereof, due to the Venturi profile so on the channel 4 flows past, that creates a negative pressure, which passes the fiber through the channel 4 transported. At the bottom 5 of the funnel is the Fa serausgang, from where the filaments can then be transported on.

example 1

800 g of pulp with a DP _(Cuoxam) of 520 are in a kneader with 3200 g of a solution consisting of 12 wt .-% NaOh, 30 wt .-% urea and 58 wt .-% water for 1 h at 25 ° C intensive mixed and then pre- _matured at 23 ° C for 48 h to a DP _(Cuoxam) of 300. The wet alkali cellulose is at room temperature in a 5 l kneader with 1200 g of solid crystalline urea for 30 min. kneaded. Subsequently, the temperature of the kneader is raised to 140 ° C and the water present withdrawn. After reaching a product temperature of 140 ° C, the mass is further kneaded for 120 minutes and then discharged from the kneader. To obtain the pure cellulose carbamate is the dry crumbly mass 3 washed with deionized water at a liquor ratio of 1:16, filtered with suction through a frit and then dried at room temperature. This loosened and crumbly product had a nitrogen content of 3.0% and a DP _(Cuoxam) of 290. It was in a dissolving kettle with agitator at -5 to + 2 ° C to a solution with 7.5% cellulose and 9% sodium hydroxide solution The solution was filtered, deaerated under vacuum and spun into a spin bath containing 140 g / l sulfuric acid and 240 g / l sodium sulfate of 25 ° C to filament yarns with 1000 capillaries, via a roller system to Verwirbelungsdüse ( 2 ), there swirled in a stream of water and stored continuously on a conveyor belt to a fleece, washed and dried. The basis weight of the nonwoven was 100 g / m ² .

Example 2

800 g of pulp with a DP _(Cuoxam) of 520 are in a kneader with 3200 g of a solution consisting of 12 wt .-% NaOh, 30 wt .-% urea and 58 wt .-% water for 1 h at 25 ° C intensive mixed and nashlig at 23 ° C for 48 h to a DP _(Cuoxam) of 300 pre- _matured . The wet alkali cellulose is at room temperature in a 5 l kneader with 1200 g of solid crystalline urea for 30 min. kneaded. Subsequently, the temperature of the kneader is raised to 140 ° C and the water present withdrawn. After reaching a product temperature of 140 ° C, the mass is further kneaded for 120 minutes and then discharged from the kneader. To obtain the pure cellulose carbamate is the dry crumbly mass 3 washed with deionized water at a liquor ratio of 1:16, filtered with suction through a frit and then dried at room temperature. This loosened and crumbly product had a nitrogen content of 3.0% and a DP _(Cuoxam) of 290. It was in a dissolving kettle with agitator at -5 to + 2 ° C to a solution with 7.5% cellulose and 9% sodium hydroxide solution the solution was filtered, deaerated under vacuum and spun into a spin bath containing 90 g / l sulfuric acid and 240 g / l sodium sulfate of 25 ° C. to filament yarns with 1000 capillaries, stretched over a roller system and a drafting system 25%, to Verwirbelungsdüse ( 2 ), there swirled in a stream of water and deposited continuously on a conveyor belt to a fleece, washed with a spray nozzle under high pressure and dried. The basis weight of the nonwoven was 75 g / m ² .

Example 3

800 g of pulp with a DP _(Cuoxam) of 520 are in a kneader with 3200 g of a solution consisting of 12 wt .-% NaOh, 30 wt .-% urea and 58 wt .-% water for 1 h at 25 ° C mixed thoroughly and then at 23 ° C for 48 h on a DP _(Cuoxam) pre- _matured . The wet alkali cellulose is kneaded at room temperature in a 5-liter kneader with 1200 g of solid crystalline urea for 30 minutes. Subsequently, the temperature of the kneader is raised to 140 ° C and the water present withdrawn. After reaching a product temperature of 140 ° C, the mass is further kneaded for 120 minutes and then discharged from the kneader. To obtain the pure cellulose carbamate is the dry crumbly mass 3 washed with deionized water at a liquor ratio of 1:16, filtered with suction through a frit and then dried at room temperature. This loosened and crumbly product had a nitrogen content of 3.0% and a DP _(Cuoxam) of 290. It was dissolved in a dissolving kettle with stirrer at -5 to + 2 ° C to a solution of 7.5 cellulose and 9% sodium hydroxide solution the solution was filtered, deaerated under vacuum and spun into a spinning bath containing 140 g / l sulfuric acid and 240 g / l sodium sulfate of 25 ° C to filament yarns with 1000 capillaries, via a roller system to Verwirbelungsdüse ( 2 ), there swirled in a stream of water and deposited continuously on a conveyor belt to a fleece. The fleece is passed through a 0.5% sodium hydroxide solution, then washed and dried. The basis weight of the nonwoven was 85 g / m ² .

Claims (32)

Process for the production of nonwovens, in which a cellulose carbamate solution by extrusion through a nozzle block containing at least 20 openings in a felling bath to several endless threads which is then spinned by gaseous medium and / or fluid swirling. Method according to claim 1, characterized in that that a nozzle block with at least 10,000 openings is used. Method according to one of claims 1 or 2, characterized that the openings of the nozzle block are arranged linear or array-like. Method according to one of the preceding claims, characterized characterized in that the ratio of length to diameter of the nozzles from 1 to 20. Method according to one of the preceding claims, characterized characterized in that the endless threads vertically spun from bottom to top in the precipitation bath. Method according to one of the preceding claims, characterized characterized in that the spinning of the continuous filaments takes place in the wet state. Method according to one of the preceding claims, characterized characterized in that the endless threads after spinning into a slot-shaped funnel down guided be at the output of the funnel, the turbulence with the gaseous Medium and / or fluid takes place. Method according to the preceding claim, characterized characterized in that by shaking movement the funnel reaches a further turbulence of the endless threads becomes. Method according to one of the preceding claims, characterized characterized in that as gaseous Me medium and / or fluid air and / or water are used. Method according to one of the preceding claims, characterized characterized in that the endless threads after the turbulence are stored on a conveyor belt. Method according to the preceding claim, characterized characterized in that by shaking movement the conveyor belt reaches a further turbulence of the endless threads becomes. Method according to one of the preceding claims, characterized characterized in that the cellulose carbamate is dissolved in sodium hydroxide solution. Method according to the preceding claim, characterized characterized in that the cellulose carbamate content of the cellulose carbamate solution is at least 6 to 12, in particular 7 to 9 wt .-%, based on the solution. Method according to one of the preceding claims, characterized characterized in that the precipitation bath from sulfuric acid with a concentration of 50 to 200 g / l, in particular 70 to 100 g / l and 100 to 300 g / l, in particular 150 to 200 g / l sodium sulfate consists. Method according to one of the preceding claims, characterized characterized in that the nonwoven fabric subsequently washed, pressed and dried. Method according to the preceding claim, characterized characterized in that the washing by a high pressure Water jet takes place. Method according to one of the preceding Claims, characterized in that the cellulose carbamate is regenerated in a regeneration bath to cellulose. Method according to the preceding claim, characterized characterized in that the regeneration bath from 0.3 to 1 wt .-% Sodium hydroxide is water and regeneration at one Temperature of 60 to 95 ° C he follows. Method according to the preceding claim, characterized characterized in that the regeneration between extrusion and turbulence carried out becomes. Method according to claim 18, characterized the regeneration is carried out after the production of the nonwoven fabric. Nonwoven fabric made of a random knit of endless filaments Cellulose. Nonwoven fabric according to claim 21, characterized that the nonwoven fabric according to the method of any one of claims 1 to 16 can be produced. Nonwoven fabric made of a random knit of endless filaments regenerated cellulose. Nonwoven fabric according to claim 23, characterized that the residual N content of 0.3 to 0.5%, in particular 0.1 to 0.2 is. Nonwoven fabric according to one of claims 23 or 24, characterized the nonwoven fabric has a pore structure with a porosity of 1 to 10 has. Nonwoven fabric according to one of Claims 23 to 25, characterized in that the nonwoven fabric has a specific internal surface area between 20 and 50 m ² / cm ³ , measured by means of small angle x-ray scattering (SAXS). Nonwoven fabric according to one of Claims 23 to 26, characterized that the nonwoven fabric with the method according to any one of claims 17 to 20 can be produced. Use of the nonwovens according to one of claims 21 to 27 in medicine, in particular as surgical drapes, sheets, wound dressings, Gauze or cotton pads. Use of the nonwovens according to one of claims 21 to 27 as hygiene substances or as wipes in the household. Use of the nonwovens according to one of claims 21 to 27 as decorative nonwovens, in particular tablecloths, napkins or curtains. Use of the nonwovens according to one of claims 21 to 27 as inlaid nonwovens in the clothing industry. Use of the nonwovens according to one of claims 21 to 27 as reinforcing nonwovens and insulating mats in the construction industry.