EP0686712B1 - Flexible cellulosic fibers with reduced modulus and NMR-characteristics and process for their production - Google Patents

Abstract

This invention relates to flexible cellulose fibers with a reduced modulus and a decreased NMR degree of order, particularly for use in the textile field, which are obtained by pressing out solutions of the cellulose in hydrous NMMNO through spinning nozzles along an air travel into an NMMNO-containing aqueous and/or alcoholic precipitation bath as well as by a conventional rinsing, aftertreatment and drying, with strengths of between 15 and 50 cN/tex, and to a process for their production. According to the invention, these flexible cellulose fibers have an initial modulus of less than 1,500 cN/tex, and the relationship of the heights of the lines at 88 ppm and 85 ppm above the spectrum base line in the highly resolved 13C-NMR solid-body spectrum is </=1. Furthermore, these flexible cellulose fibers are obtained by means of a process in which specified hydrophilic, low-molecular weight, organic additives, which are soluble in the polymer solution and have mainly nitrogen-containing groupings are added in defined amounts to the spinning solution of the cellulose as well as to the precipitation bath.

Description

The invention relates to flexible cellulose fibers with a reduced modulus and a reduced degree of NMR order for predominant use in such textile areas where flexible moldings, e.g. textile fibers and filament yarn are produced and required, hereinafter called fibers, and those that are more environmentally friendly than the viscose process N-methylmorpholine-N-oxide (NMMNO) spinning process can be produced, and a Process for their production.

Because of the high investment costs and especially because of the high environmental impact, there is considerable interest in finding alternatives to the viscose process, according to which the majority of regenerated cellulose fibers are currently produced. One of the most promising processes is the spinning of cellulose solutions in amine oxides, preferably in N-methylmorpholine-N-oxide (NMMNO), not least because it avoids the cumbersome process of derivatizing cellulose. It is known that cellulose is soluble in an NMMNO water system and can be processed into textile fibers by spinning in a mostly aqueous NMMNO solution (US Pat. No. 3,767,756, German Pat. No. 2,830,685, DD PS 142 898). It is also known that a mixture of NMMNO and caprolactam derivatives also has good solubility properties for cellulose (US Pat. No. 5,362,867, TW 210359).
A special feature of this process is the instability of the solvent under certain conditions at temperatures just above the processing temperature of the spinning solutions, which can lead to an uncontrolled chain reaction. It is therefore part of the prior art that additives are added to the spinning solution with the aim of stabilizing the spinning solution, in particular preventing or at least limiting the breakdown of the cellulose and the decomposition of the NMMNO (DD 201 703, DD 229 708, DD158 656) . For this purpose, a number of substances such as amines, gallates, ascorbic acid, hydroquinone and urea are mentioned by various authors. Propyl gallate has proven to be particularly effective even at low concentrations. The amounts used for stabilization are in a range below 1% based on cellulose.

Additives are also used to prevent the threads from sticking during the process Spinning process recommended (DD 218 121) e.g. Polyethylene glycol, or as useful for that Increased tear strength and the modulus of the threads detected (Chanzy, H. et al .: polymer 31: 400-405 (1990).

For the fibers produced by the NMMNO process are compared to viscose fibers characteristic of high strengths and moduli. The tensile strengths are in general in an approximate range of approx. 20 to 50 cN / tex, where cN / tex centi Newtons per tex means, and the initial moduli in a range above about 1500 cN / tex. It means that the strengths are pleasantly high, but often higher than necessary and the moduli significantly high for an advantageous application in the area of flexible fibers with good textile usage properties in which e.g. the usual, for textile use in clothing proven viscose fibers with initial moduli well below 1500 cN / tex will.

Although the NMMNO process is already being used on an industrial scale, the fibers produced with it also have some other disadvantages compared to those which are produced using the conventional viscose process. Among other things, they show brittleness and fibrillation resistance. The values achieved for the elongation at break cannot be satisfactory either, so that Krutschinin et al. (SU 1 224 362) and Romanov et al. (Fiber Chemistry, 21, 4 (1990), 317-320) correct this defect in place of the most commonly used Falling bath from an aqueous NMMNO solution, a solution of NMMNO in isopropanol or amyl alcohol has been described. It also proves to be disadvantageous that the range of variation of the textile-physical characteristic values is small when the production conditions change. Furthermore, the fibers have a relatively high degree of order, which can be seen in the high-resolution ¹³ C-NMR solid-state spectrum at C-1, C-4 and to a certain extent also at C-6. From the ratio of the line heights (distance of the maximum of the respective line from the baseline of the spectrum) at C-4 at approx. 88 and 85 ppm, a relatively easily accessible measure, it can be seen, for example, that this ratio has a value ≤ 1 for flexible viscose fibers , 0, while for NMMNO fibers it is above one, for example 1.35.

Chanzy et al. Showed one way of influencing the module of the fibers. (see polymer 31 (1990), 400-405) by adding inorganic salts such as e.g. Ammonium chloride or calcium chloride, to the NMMNO spinning solution of the cellulose. But with that achieved a significant increase in strength and modulus. The fibers tend even more on brittleness and fibrillation. The result is a splitting of the fibers in bending and Buckling stress. Such fibers, the typical behavior of high strength, high modulus Show fibers are for many technical purposes, especially in the form of composites in solid matrix, excellently suitable, but hardly usable in the textile area.

Despite the large number of additives already described for addition to cellulose NMMNO spinning solutions So far, there has been no possibility of using flexible cellulose fibers to be able to produce a significantly reduced module and a reduced degree of order.

Thus, there is still a general interest in using flexible cellulose fibers to provide a reduced module from NMMNO solutions and thus the spinning process influence that with it also flexible, provided with a low module and thus for the more suitable fibers with a low degree of order can be produced can.

The object of the present invention is to provide such flexible cellulose fibers, all Do not have disadvantages of the prior art to specify.

It is therefore an object of the invention to provide flexible cellulose fibers with reduced modulus and reduced Provide NMR order by the NMMNO method, which for the textile use can be used.

In addition, it is an object of the invention to provide flexible cellulose fibers with a reduced modulus and reduced order of NMR order, which do not have high brittleness and tendency to fibrillation demonstrate.

Furthermore, it is an object of the invention to provide a method for producing the flexible cellulose fibers of the type mentioned.

Another procedural object of the invention is that it is proposed Process for producing the flexible cellulose fibers of the type mentioned lower Investment costs required and less polluting than the viscose process.

It is therefore an object of the invention to provide a solution, such as with the NMMNO method flexible cellulose fibers of the type mentioned can be produced.

An additional object of the invention is that this to be proposed on the Process based on the NMMNO process with regard to the range of variation textile-physical parameters about changes in manufacturing conditions allows great scope.

According to the invention, these tasks with respect to the flexible cellulose fibers mentioned Kind with a flexible cellulose fiber, as shown in claim 1, and on the process side with a method according to one or more of claims 2 to 13 solved.

The tasks on the cellulose fiber side are solved with a flexible cellulose fiber with a reduced module and a reduced degree of NMR order, especially for textile use, which is achieved by pressing solutions of cellulose in water-containing NMMNO (N-methylmorpholine-N-oxide) through spinnerets over an air gap in an NMMNO-containing aqueous and / or alcoholic precipitation bath, as well as by conventional rinsing, post-treatment and drying with strengths between 15 and 50 cN / tex. According to the invention, these flexible cellulose fibers which can be produced in this way are characterized in that they have an initial modulus of less than 1500 cN / tex and in the high-resolution ¹³ C-NMR solid-state spectrum the ratio of the heights of the lines at 88 ppm and 85 ppm (C-4 range ) above the spectrum baseline is ≤ 1.

These flexible cellulose fibers according to the invention according to claim 1 with reduced The module and the reduced degree of NMR ordering are process-side by pressing one Solution of cellulose in water-containing NMMNO through a spinneret over an air gap in an NMMNO-containing, aqueous and / or alcoholic precipitation bath and then conventional washing, post-treatment and drying.

It was surprisingly found that, despite the large number, the state of the art Technology of proposed additives is possible according to the invention, the initial module and the NMR order of the cellulose fibers precipitated from cellulose NMMNO water spinning solutions then drastically lower when both the cellulose spinning solution hydrophilic, low molecular weight, organic, soluble in the polymer solution Additives can be added. Amines and amides are suitable as additives for this or other substances containing amino groups, which is one of the nitrogen groups have a neighboring oxygen-containing group. The concentration of additives in the spinning solution, based on the cellulose content of the solution, should be at least 1% by mass, amount to a maximum of 200% by mass. In contrast, a proportion of the additives in the precipitation bath is at least 0.1 mass% and at most 20 mass%, based on the amount of Total fall bath, cheap.

Additives are preferably used in which the oxygen-containing group is a Is carbonyl group. Advantageously, e.g. Urea, caprolactam, Aminopropanol and / or aminocarboxylic acid used. In the case of simultaneous use Several additives can be used as individual components or as Introduce mixture.

Whether it is more advantageous to use the additives as individual components or as a mixture is determined by the specific application.

Surprisingly, it was also found that the desired effect is greatest is when the additive (s) added to the precipitation bath is added to the one or more in the spinning solution contained additive (s). That means the best results were when the additive or additive mixture dissolved in the precipitation bath next to the NMMNO or the additives dissolved in the precipitation bath are the same as those present in the spinning solution are.

The concentration of the additives in the spinning solution, based on the The cellulose content of the solution should be at least 10% by mass and at most 100% by mass. So it is advantageous here, for example, if the concentration of the additives in the spinning solution, based on the cellulose content of the solution at least 4% by mass, at most 75% by mass, preferably at least 10% by mass, at most 50% by mass. Against it in the precipitation bath a proportion of the additives of at least 1% by mass and at most 10% by mass, based on the amount of total precipitation bath preferred.

Furthermore, it was found that the desired effect also occurs when the water in the precipitation bath partially or completely, preferably completely, by alcohols, in particular is replaced by isopropanol or amyl alcohol, the additives up to their maximum Saturation concentration can be contained in the precipitation bath.

The fibers spun in a conventional manner from a nozzle through an air gap into the precipitation bath and aftertreated and dried in the usual way have an initial modulus derived in a known manner from the force / elongation diagram of well below 1500 cN / tex, preferably even below 1200 cN / tex, and / or an NMR order of magnitude of ≤ 1 characterized by the height ratio in the maximum of the lines at 88 ppm and 85 ppm above the baseline of the high-resolution ¹³ C-NMR solid-state spectrum in the C-4 range.

With the cellulose fibers of the type mentioned and the invention Processes according to the invention for their production could overcome all the disadvantages of State of the art eliminated and the tasks set.

The invention is illustrated by the examples listed below.

Example 1 (comparative example according to the prior art):

A spinning solution of 9.5% cellulose in NMMNO monohydrate with 0.1% by mass, based on cellulose, propyl gallate as stabilizing agent was spun in a laboratory extruder with a 20-hole nozzle at a temperature of 90 ° C., being the spinning bath (Precipitation bath) a 10% solution of NMMNO in water was used. The fiber has the following parameters: Titer: 4.1 tex Tensile strength, dry: 34.3 cN / tex wet: 23.2 cN / tex Elongation at break, dry: 5.1% wet: 8.1% Initial module, dry: 2117 cN / tex wet: 311 cN / tex

The ratio of the heights of the NMR lines at 88 and 85 ppm is 1.35.

Example 2 (comparative example )

As example 1 with an addition of 25% urea, based on the cellulose content, in the spinning solution. The fiber has the following parameters: Titer: 4.1 tex Tensile strength, dry: 35.6 cN / tex wet: 10.5 cN / tex Elongation at break, dry: 10.0% wet: 18.1% Initial module, dry: 1922 cN / tex wet: 131 cN / tex

The ratio of the heights of the NMR lines at 88 and 85 ppm is 1.0.

Example 3

As in Example 2 using a precipitation bath consisting of a 6% aqueous urea solution. The fiber has the following parameters: Titer: 4.1 tex Tensile strength, dry: 33.1 cN / tex wet: 12.2 cN / tex Elongation at break, dry: 11.5% wet: 17.0% Initial module, dry: 1430 cN / tex wet: 120 cN / tex

The ratio of the heights of the NMR lines at 88 and 85 ppm is 1.0.

Example 4

As example 2 using a precipitation bath consisting of a 10% aqueous urea solution. The fiber has the following parameters: Titer: 4.0 tex Tensile strength, dry: 28.0 cN / tex wet: 13.2 cN / tex Elongation at break, dry: 13.9% wet: 19.9% Initial module, dry: 446 cN / tex wet: 126 cN / tex

The ratio of the heights of the NMR lines at 88 and 85 ppm is 0.96.

Example 5

As example 1 with an addition of 15% urea, based on the cellulose content, in the spinning solution and using a precipitation bath (spinning bath) consisting of a 10% urea solution. The fiber has the following parameters: Titer: 4.0 tex Tensile strength, dry: 31.0 cN / tex wet: 10.9 cN / tex Elongation at break, dry: 12.3% wet: 18.4% Initial module, dry: 1255 cN / tex wet: 110 cN / tex

The ratio of the heights of the NMR lines at 88 and 85 ppm is 0.98.

Example 6

As example 1 with an addition of 25% caprolactam, based on the cellulose content, but additionally in the spinning solution using a spinning bath (precipitation bath) consisting of a 10% aqueous caprolactam solution. The fiber has the following parameters: Titer: 4.0 tex Tensile strength, dry: 31.0 cN / tex wet: 10.9 cN / tex Elongation at break, dry: 12.3% wet: 18.4% Initial module, dry: 1255 cN / tex wet: 110 cN / tex

The ratio of the heights of the NMR lines at 88 and 85 ppm is 0.95.

Example 7 (comparative example )

As example 1 with an addition of 25% aminocaproic acid, based on the cellulose content, in the spinning solution. The fiber has the following parameters: Titer: 4.2 tex Tensile strength, dry: 25.4 cN / tex wet: 10.1 cN / tex Elongation at break, dry: 7.1% wet: 11.9% Initial module, dry: 1580 cN / tex wet: 278 cN / tex

The ratio of the heights of the NMR lines at 88 and 85 ppm is 0.98.

Example 8

As example 7, but additionally using a spinning bath (precipitation bath) consisting of a 10% aqueous aminocaproic acid solution. The fiber has the following parameters: Titer: 3.9 tex Tensile strength, dry: 18.3 cN / tex wet: 5.7 cN / tex Elongation at break, dry: 6.1% wet: 23.4% Initial module, dry: 760 cN / tex wet: 63 cN / tex

The ratio of the heights of the NMR lines at 88 and 85 ppm is 0.96.

Claims (13)

1. Flexible cellulose fibres with reduced modulus and diminished NMR degree of order, especially, for use in textiles, which are obtained by expressing solutions of the cellulose in aqueous N-methyl-morpholine-N-oxide (NMMNO) through spinning nozzles over an air path into an aqueous and/or alcoholic spinning bath, as well as by conventional rinsing, post-treatment and drying, with tear strengths between 15 and 50 cN/tex, characterized in that they have an initial modulus in the dry state of less than 1500 cN/tex and in that the ratio of the heights of the lines at 88 ppm and 85 ppm (C-4 region) above the spectrum base line is ≤ 1 in the highly resolved ¹³C-NMR solid body spectrum.
2. A method of producing flexible cellulose fibres with reduced modulus and diminished NMR degree of order, according to claim 1, by expressing a solution of cellulose in aqueous NMMNO through a spinning nozzle over an air path into an aqueous and/or alcoholic spinning bath containing NMMNO and following washing, post-treatment and drying in conventional manner, characterized in that hydrophilic, low molecular, organic additives soluble in the polymer solution are added to both the spinning solution of the cellulose and to the spinning bath, in that the additives represent amines, amides or other substances containing amino groups, in which the nitrogen-containing grouping is adjacent to a group containing oxygen, in that the concentration of the additive in the spinning solution, referred to the cellulose component of the spinning solution, corresponds to at least 1% by mass and at most 200% by mass, and in that the mass proportion of the additive in the spinning bath amounts to at least 0.1% by mass and at most 20% by mass.
3. A method according to claim 2, charactenzed in that the groups containing oxygen are carbonyl groups.
4. A method according to claim 2 or 3, characterized in that urea, caprolactam and/or aminohexanoic acid are used as the additive.
5. A method according to claim 2 or 3, characterized in that amino-propanol is used as the additive.
6. A method according to one or more of claims 2 to 5, characterized in that the additives are used as a mixture thereof when several additives are employed.
7. A method according to one or more of claims 2 to 5, characterized in that the additives are used as individual components, even when several additives are employed.
8. A method according to one or more of claims 2 to 7, characterized in that the additive(s) added to the spinning bath correspond to the additive(s) added to the spinning solution.
9. A method according to claim 2, characterized in that the amounts in which the additives are added to the spinning solution correspond to a concentration of the additives in the spinning solution, referred to the cellulose component of the spinning solution, of at least 10% by mass and at most 100% by mass.
10. A method according to claim 2, characterized in that the mass proportion of the additive in the spinning bath amounts to at least 1% by mass and at most 10% by mass.
11. A method according to one or more of claims 2 to 10, characterized in that the water in the spinning bath is partially or wholly replaced by alcohols.
12. A method according to claim 11, characterized in that the water in the spinning bath is replaced completely by alcohols.
13. A method according to claim 11 or 12, characterized in that isopropanol and/or amyl alcohol are used as alcohols.