WO1998038373A1

WO1998038373A1 - Method for producing a reinforced fiber composite

Info

Publication number: WO1998038373A1
Application number: PCT/AT1998/000040
Authority: WO
Inventors: Hartmut Rüf; Heinrich Firgo; Siegfried Ambrosch; Christian Schlossnikl; Raimund Jurkovic
Original assignee: Lenzing Aktiengesellschaft
Priority date: 1997-02-25
Filing date: 1998-02-25
Publication date: 1998-09-03
Also published as: EP0901533A1; AT404368B; NO984883D0; NO310205B1; ATE196329T1; ES2152745T3; CN1105798C; CA2251728A1; AU6200198A; ID20258A; JP2000509771A; NO984883L; ATA31997A; EP0901533B1; CN1224474A; BR9805914A; DE59800265D1; AU727252B2

Abstract

The invention relates to a method for producing a reinforced fiber composite which contains cellulosic fibers, the cellulose being present in the crystalline structure cellulose II, by bringing said fiber composite into contact with an aqueous solution of N-methylmorpholin-N-oxide (NMMO) at an elevated temperature and subsequently washing said fiber composite. Said method is characterized in that the fiber composite is brought into contact with the aqueous solution in such a way that the reationship -947 + 0.30xlog(10)t + 0.046xT - 3.53xC + 645xlog(10)C where t is the time in minutes during which the fiber composite is kept in contact with the aqueous NMMO solution, T is the temperature of the aqueous NMMO solution in °C and C is the concentration of the NMMO in % mass in relation to the aqueous NMMO solution, gives a figure in the region of 0.30 and 1.70 on the condition that the temperature T is less than 130 °C and the concentration C lies in the region of 70 to 84 % mass.

Description

Process for producing a consolidated fiber composite

The present invention relates to a method for producing a solidified fiber composite, which contains cellulosic fibers, the cellulose being present in the cellulose II crystal structure, by contacting the fiber composite with an aqueous solution of N-methylmorpholine-N-oxide (NMMO) at elevated temperature and then washing the fiber composite.

For the purposes of the present description and the present claims, the term "fiber composite" is intended to denote any type of fabric, fleece or scrim.

As an alternative to the viscose process, a number of processes have been described in recent years in which cellulose is dissolved in an organic solvent, a combination of an organic solvent with an inorganic salt or in aqueous salt solutions without the formation of a derivative. Cellulose fibers made from such solutions were given the generic name Lyocell by BISFA (The International Bureau for the Standardization of man made Fibers). BISFA defines a cellulose fiber as Lyocell, which is obtained from an organic solvent by a spinning process. BISFA understands "organic solvent" as a mixture of an organic chemical and water.

To date, however, only a single process for the production of a cellulose fiber of the Lyocell type has prevailed until industrial implementation, namely the amine oxide process. In this process, N-methylmorpholine-N-oxide (NMMO) is preferably used as the solvent. For the purposes of the present description, the abbreviation "NMMO" is used for the term "tertiary amine oxides" used, NMMO additionally stands for the N-methylmorpholine-N-oxide which is preferably used today.

Tertiary amine oxides have long been known as alternative solvents for cellulose. From US Pat. No. 2,179,181 it is known, for example, that tertiary amine oxides can dissolve high-quality chemical pulp without derivatization and that cellulosic shaped bodies such as fibers can be obtained from these solutions by precipitation. US Pat. Nos. 3,447,939, 3,447,956 and 3,508,941 describe further processes for the preparation of cellulosic solutions, cyclic amine oxides preferably being used as solvents. In all of these processes, cellulose is physically dissolved at an elevated temperature.

EP-A-0 356 419 by the applicant describes a process which is preferably carried out in a thin-film treatment apparatus in which a suspension of the comminuted pulp in an aqueous tertiary amine oxide, spread out in the form of a thin layer, is transported over a heating surface , the surface of this thin layer being subjected to a vacuum. When the suspension is transported over the heating surface, water is evaporated off and the cellulose can be brought into solution, so that a spinnable cellulose solution is discharged from the thin-film treatment apparatus.

A method and an apparatus for spinning cellulose solutions are known, for example, from WO 93/19230 by the applicant. The spinning solution is spun in a warm state and the filaments obtained are introduced into a precipitation bath to precipitate the cellulose contained, the filaments being cooled before being introduced into the precipitation bath. The cooling is carried out immediately after molding and preferably consists of blowing the cellulosic molding horizontally with air. German Patent No. 902 427 describes the consolidation of a nonwoven made of cellulose fibers by means of a lye bath which contains 5 to 15% NaOH. The cellulose fibers are swollen with the lye bath, causing a consolidation.

From WO 95/07386 by the applicant a process for the production of paper is known, in which an aqueous suspension of shredded cellulosic material is treated mechanically and then one

Sheet formation process is subjected, wherein the suspension contains a tertiary amine oxide. This process allows the production of high strength paper.

A method for solidifying a fibrous material is known from US-A-3,447,956. The solidification is carried out by impregnating the fibrous material with an amine oxide and heating it to a temperature at which the amine oxide can solidify the fibrous material. Woven and nonwovens, which are natural cellulosic fibers, such as e.g. Pulp, cotton, linen, but also synthetic fibers, e.g. Include rayon (viscose fibers), suggested. The treatment of paper with the amine oxide is particularly preferred. NMMO is apparently used as a monohydrate in molten or liquid form or in solution with a volatile, evaporable solvent.

From WO 96/37653 fiber composites are known which are provided with a cellulosic coating, impregnation or covering. These fiber composites are produced by coating the fiber composite on one side with a solution of cellulose in an aqueous NMMO, after which the layer is coagulated in a water bath.

The US-A-4,196,282 describes the three-component system MMO / H ₂ 0 / cellulose and the so-called "release window", that is Conditions under which the cellulose dissolves in the aqueous NMMO.

It is also known that cellulose fibers can be swollen with NMMO (Chancy et al., "Swelling and Dissolution of Cellulose in Amine Oxide / Water Systems"; J.App. Pol. Sei: Appl. Pol. Symp. 37, 239-259 (1983)).

The object of the invention is to provide a method of the type mentioned at the outset in which a fiber composite can be solidified without complex evaporation of a volatile solvent or without the need to use an NMMO monohydrate or to produce it by evaporation.

The process according to the invention for producing a consolidated fiber composite, which contains cellulosic fibers, the cellulose being present in the cellulose II crystal structure, by contacting the fiber composite with an aqueous solution of N-methylmorpholine-N-oxide (NMMO) at elevated temperature and then washing the Fiber composite, is characterized in that the contacting is carried out so that the relationship

-947 + 0.30xlog _{/ 1 (} ., T + 0.046xT - 3.53xC + 645xlog, _{1 (} ..C

in which t means the time in minutes that the fiber composite is contacted with the aqueous NMMO solution, T means the temperature of the aqueous NMMO solution in ° C, and C the concentration of the NMMO in mass%, based on the aqueous NMMO Solution means a number in the range from 0.30 and 1.70, preferably in the range from 0.5 to 1.5, and particularly preferably in the range from 0.8 to 1.2, with the proviso that that the temperature T is less than 130 ° C and the concentration C is in the range of 70 to 84 mass%. The invention is based on the knowledge that the three parameters mentioned, that is to say the concentration of the NMMO solution, its temperature and the impregnation time, are apparently essential and sufficient for the strengthening of a composite, for example a nonwoven, of cellulose fibers, and that they are also chosen in this way the above relationship must be satisfied. If, on the other hand, these parameters are chosen so that the relationship is less than 0.30, the bond cannot be strengthened. On the other hand, if the parameters are chosen so that the relationship gives a value above 1.70, then a dissolution of the fiber composite in the NMMO solution is observed.

In the process according to the invention, the temperature T is preferably less than 100 ° C.

A special embodiment of the method according to the invention is characterized in that the fiber composite is pressed before washing. The pressing can be carried out in a simple manner e.g. be made so that the fleece is guided between two rollers that exert pressure on the fiber composite.

In the process according to the invention, the use of a fiber composite has proven particularly useful, the fibers of which have been produced at least in part by the amine oxide process or the viscose process.

The invention is described in more detail with the following examples.

General working instructions

Weakly needled viscose nonwovens, each measuring 12 x 16 cm and with a basis weight of approximately 70 g / cm ² , were immersed in an aqueous NMMO solution between two sieves and left to impregnate, after which the impregnated Nonwovens were pressed using a laboratory press (pressing pressure: Ξ bar; corresponding to a line pressure of 12.6 N / mm with a fleece width of 12 cm). The pressed nonwovens were then washed with tap water for 15 minutes.

Examples

According to the above general working procedure, several tests were carried out, the parameters to be set according to the invention, namely the concentration of the respective NMMO solution (in mass% NMMO, based on the total mass of the solution), its temperature (in ° C.) and the impregnation time (in Minutes) were selected as indicated in Table 1 below. All of the examples meet the relationship given above. The value resulting from the parameters is also given in the table.

Table 1

Eg NMMO concentration temperature time value

1 84.0 80 0.08 0.95

2 82.0 80 0.08 1.30

3 82.0 70 0.17 0.94

4 80.6 70 0.50 1.20

5 80.6 80 0.08 1.42

6 80.6 80 0.50 1.66

7 78.2 70 1.00 1.29

8 76.2 70 0.50 1.00

9 76.2 80 0.17 1.32

10 73.9 70 4.00 0.81

11 74.2 80 0.50 1.07

12 74.2 90 0.17 1.39

13 71.9 90 2.00 1.02

14 71.9 100 0.17 1.16

15 70.0 100 0.50 0.49 Examples 1 to 15 are according to the invention, since the values resulting from the above-mentioned relationship with the NMMO concentration, the temperature and the impregnation time are in the range specified according to the invention. All of the nonwovens proved to be consolidated after the treatment according to the invention.

Similar good results could be obtained with a non-woven fabric which consisted of fibers which had been produced by the amine oxide process.

Comparative Examples

For comparison, further tests were carried out in accordance with the general working instructions, but the parameters were chosen such that the relationship was not fulfilled. These examples are given in Table 2.

Table 2

Eg NMMO concentration temperature time value

16 82.0 90 0.17 1.86

17 80.6 80 1.00 1.75

18 80.6 90 0.08 1.88

19 78.2 80 2.00 1.84

20 78.2 90 0.08 1.88

21 76.2 90 0.50 1.92

22 76.2 100 0.08 2.14

23 74.2 100 0.08 1.75

24 72.2 70 4.00 0.29

25 72.2 120 4.00 2.59

26 70.0 80 12.0 -0.10

27 70.0 90 2.00 0.21

28 70.0 100 0.08 0.25

In the case of Examples 16 to 23 and 25, the parameters of which give a value greater than 1.70, the fleece dissolved in the NMMO solution. In the case of Examples 24 and 26 to 28, the parameters of which give a value of less than 0.30, it was not possible to achieve nonwoven bonding.

Claims

Claims:

Process for the production of a consolidated fiber composite, which contains cellulosic fibers, the cellulose being present in the cellulose II crystal structure, by contacting the fiber composite with an aqueous solution of N-methylmorpholine-N-oxide (NMMO) at elevated temperature and subsequent washing of the fiber composite,

characterized in that

contacting is carried out so that the relationship

-947 + 0.30xlog, ₁₀ , t + 0.046xT - 3.53xC + 645xlog _{/ 1Q} .C

in which t means the time in minutes that the fiber composite is contacted with the aqueous NMMO solution, T means the temperature of the aqueous NMMO solution in ° C., and C the concentration of the NMMO in mass%, based on the aqueous NMMO Solution means a number in the range of 0.30 and 1.70, with the proviso that the temperature T is less than 130 ° C and the concentration C is in the range of 70 to 84% by mass.

2. The method according to claim 1, characterized in that the parameters t, T and C are chosen so that the relationship gives a number in the range from 0.5 to 1.5.

Method according to Claim 2, characterized in that the parameters t, T and C are chosen so that the relationship gives a number in the range from 0.8 to 1.2.

4. The method according to any one of claims 1 to 3, characterized in that the temperature T is less than 100 ° C.

5. The method according to any one of claims 1 to 4, characterized in that the fiber composite is pressed before washing.

Method according to one of claims 1 to 5, characterized in that a fiber composite is used for consolidation, the fibers of which were at least partially produced by the amine oxide process.

Method according to one of claims 1 to 5, characterized in that a fiber composite is used for consolidation, the fibers of which were at least partially produced by the viscose process.