SK280035B6 - Process for producing shaped articles from cellulose - Google Patents

Abstract

A process for producing shaped articles from cellulose wherein a cellulosic amine oxide solution is pressed through a nozzle, then it is passed through an air slit, then it is subjected to coagulation in a precipitation bath and finally said solution is extracted therefrom. According to the invention, the ratio of discharge rate-to-hole emergence rate ranges from 0.5 to 0.9. The cellulosic article is thereafter coagulated in the precipitating bath and is oriented. The orientation is processed by stretching or deep-drawing.

Description

Technical field

The present invention relates to a process for the manufacture of shaped articles from cellulose, in which the cellulose solution is extruded through a nozzle or slot, then passed through an air slot and finally coagulated in a precipitation bath.

BACKGROUND OF THE INVENTION

It is known that fibers with good user properties are obtained from high molecular weight polymers only when a "fibrous structure" can be obtained (Ullmann, 5th edition, Vol. A10 456). Among other things, it is necessary to orient the microoriented region in polymers, such as fibrids, in the fiber. This orientation is given by the method of manufacture and is based on physical or physico-chemical processes. In many cases, this orientation is caused by debt.

In which section of the process and under what conditions this stretching is performed is critical to the fiber properties obtained. In melt spinning, the fibers are elongated in a warm plastic state while the molecules are still movable. Soluble polymers can be spun dry or wet. In the dry spinning, drawing is carried out while the solvent leaks or evaporates; the fibers extruded into the shrink bath extend during coagulation. Methods of this kind are known and are widely described. In all cases, however, it is important that the transition from the liquid state (regardless of whether the melt or solution) to the solid state occurs so that the orientation of the polymer chains or the polymer chain clusters (so-called fibrides, fibrils) 1, etc.).

In order to prevent the solvent from evaporating sharply from the fiber during dry spinning, there are several possibilities.

The problem of rapid coagulation of a polymer in wet spinning (such as in the case of cellulose amine oxide solutions) has hitherto been solved only by a combination of dry and wet spinning.

Thus, it is known that polymer solutions are introduced into the coagulation environment through an air gap. EPA-295 6762 describes the manufacture of aramid fibers which are introduced into a non-coagulating environment through an air gap, lengthened and finally coagulated

The subject of DD 218 121 is the spinning of cellulose in amine oxides through an air gap, and measures are provided to prevent sticking.

According to U.S. Pat. No. 4,501,886, the cellulose triacetate solution is spun by means of an air gap.

U.S. Pat. No. 3,414,645 also describes the preparation of aromatic polyamides from solutions in a combination of dry and wet spinning.

In all of these methods, some orientation is achieved in the air gap, since by itself allowing the viscous solution to flow through a small opening downwards, it forces the solution particles to be oriented by orientation. This orientation can be further increased by the force of gravity when the extrusion rate of the polymer solution and the withdrawal rate of the fiber are adjusted to achieve elongation.

A method of this kind is described in AT Patent 387,792 (or its equivalent U.S. Patents 4,246,221 and 4,416,698). The solution of cellulose in NMMO (NMMO = N-methylmorpholine-N-oxide) and water is faced, elongated in the air gap and finally allowed to precipitate. Debt shall be made at a debt ratio of at least 3.

The disadvantage of this method is that it is not possible to change the properties of the shaped body. It is necessary to minimize the spinning-to-draw ratio in order to obtain corresponding textile properties. With a very low elongation, only the most limited textile properties of the fiber can be achieved, that is to say, for example, in the manufacture of the fiber, minimum processability (i.e. the product of fiber strength and fiber retention) is achieved. Another drawback is that the effect of the so-called dissipation / exit rate resonance (cf. Navard, Hauding, "Spinning of a Cellulose N-methylmorpholine-N-oxide solution", Polymer Process Engineerign, 3/3), 291 (1985), uneven fiber diameters, the larger the spinning / elongation ratio. Finally, it is also disadvantageous that the forming can practically take place only in the air gap. Post-forming can only be achieved with a very technical challenge. This naturally limits the band width of a possible product. It would be desirable to further influence the properties of the product, thereby making the process considerably more flexible.

It is an object of the present invention to overcome these drawbacks.

SUMMARY OF THE INVENTION

This object is achieved by the method according to the invention, in which the cellulose amine oxide solution is extruded through a nozzle, then passed through an air gap and finally coagulated in a precipitation bath, wherein the ratio of the rate of withdrawal from the precipitation bath to the exit speed of the nozzle it is between 0.5 to 0.9 and the shaped cellulose body is then coagulated in a precipitation bath while orienting.

The shaped cellulosic body is further oriented by elongation or deep drawing.

Thus, according to the invention, the rate of withdrawal is less (or at most equal to) the rate of exit of the spinning material from the aperture, so that no stretching can occur; thus, the cellulose remains in a relatively undirected state until coagulation in the precipitation bath. This is advantageous because there is a greater possibility of later influencing the properties. Due to the lack of orientation, the coagulated (precipitated) cellulose has an elasticity that resembles almost the elasticity of the rubber. According to the invention, this cellulose can now be drawn or deep drawn to obtain the desired properties; this also guarantees the required flexibility.

A further advantage is that, due to the fact that there is no longer elongation, the air gap can be formed almost arbitrarily short, so that even if the spinnerets have a very high hole density, there is no danger of the adjacent fibers sticking together. Since, in large-scale production, productivity can be decisively increased by increasing the hole density, this is also an essential advantage of the present invention.

The invention is illustrated by the following examples.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

Fiber production at a ratio of removal rate to exit rate of less than 1 (comparative experiment),% cellulosic NMMO solution (pulp of 10% water type, 77% NMMO, 0.1% oxalic acid stabilizer) was passed through a 100-hole nozzle (rpm diameter of raft 130 pm). The removal rate was 16.5 g / min; the resulting removal rate was 10.35 m / min. 100 fibers were passed through an 8 mm long air gap and then at a speed of 6 m / min. 15 cm spinning bath (temperature: 2 ° C, NMMO concentration: 5%) The ratio of withdrawal rate to exit rate was thus 0.58.

The resulting fiber had an elongation strength of 11.8 cN / tex at 77.5%. The elongation value is extremely large; this demonstrates that the cellulose is in a relatively disordered state.

Example 8

Orientation of fibers after coagulation in air

This experiment was carried out as in Example 1. In this case, however, the fibers were wound onto a galette at a speed of 6 m / min after passing through the spin bath, i.e. after coagulation. and the fiber bundle (fiber skein) was passed through the second roller at a speed of 13 m / min. The orientation was therefore 117%. (In the present invention, fiber orientation in% is understood to be finite length - initial length, initial length.

The resulting fibers had a tensile strength of 22.4 cN / tex at an elongation of 15.3%.

Example 3

Fiber orientation after coagulation in water

In this experiment, the fibers were again passed as in Example 1 through a spin bath at a speed of 6 m / min. (drain rate) exit rate: 0.58 (and then 60 cm long orientation water bath) temperature: 77 ° C. The second galet was propelled at two different speeds. The fibers obtained had the following properties:

IN (M / min.) orientation (%) titer (Dtex) strength cond. (CN / tex) stretch cond. (%) 14 133 32.4 19.7 17.5 21 250 10.3 22.3 9.2

Example 4

Production of the fiber at a ratio of discharge rate to exit rate greater than 1 (comparative experiment)% cellulosic NMMO solution (pulp type 10% water, 77% NMMO, 0.1% oxalic acid stabilizer) was extruded through a 100-hole nozzle ( hole diameter 70 µm). The delivery rate was 5.1 g / min, which corresponds to an exit speed of 11.1 m / min. The drainage rate of the first pallet was 33.3 m / min, i.e. the ratio of drainage rate to exit rate was 3.0. At a rate of galette 1, the fibers were passed through a spin bath having a temperature of 33 ° C and a concentration of NMMO of 10%. The terminating orientation bath had a temperature of 79 ° C and an NMMO concentration of 9%. The second galet after the orientation bath had a drain rate of 46.9 m / min, i.e. the orientation was 41%.

The textile properties of the obtained fibers were: Titer: 3.5 dtex

Strength conditioned: 25 cN / tex Stretch conditioned: 8.8%

The fibers can still be oriented at a ratio of the withdrawal rate to the exit rate of the aperture greater than 1, but not to the same extent as documented in Examples 2 to 4.

Example 5

Foil Production The NMMO cellulose solution (pulp type 12% water, 79% NMMO, 0.1% oxalic acid stabilizer) was extruded through a slit nozzle (slit: 50 µm, length: 30 mm). The removal rate was 21.3 g / min, which corresponds to an exit rate of 11.7 m / min. The extruded solution was discharged through a 7 mm long air gap and then a 15 cm spinning bath (temperature 34 ° C; NMMO concentration: 20%) using a first galette at a rate of 6 m / min. The ratio of withdrawal rate to output rate was thus 0.51. In this same step, the film was passed through an 80 cm long orientation bath (temperature: 90 ° C; concentration: 20%) and oriented with a second galette (speed: 11 m / min). The orientation was thus 83%. The properties of the washed and dried film were: thickness: 10 µm; strength 200 n / mm ² , elongation 6.5%.

Example 6

Production of shaped cellulose body

A film was made as in Example 5 but not oriented, that is, the film was removed on the first galette. In the undirected state, it was deep drawn, washed and dried with a 3 mm glass rod to obtain a stable shaped body.

Example 7% sulfite cellulose solution was spun by means of a nozzle with a 130 µm orifice. The ratio was 0.86, the elongation in the second bath was 56%. Spin bath temperature 72 ° C. The following textile data was obtained: Cond. 23.3 cN / tex, cond. 13.4%.

Claims (2)

PATENT CLAIMS A process for producing shaped cellulosic bodies in which a cellulosic amine oxide solution is passed through a nozzle, then passed through an air gap and finally coagulated in a precipitation bath and drained therefrom, characterized in that the ratio of removal rate from the precipitation bath to the exit rate of the nozzle is between 0.5 to 0.9, and the shaped cellulose body is then coagulated in a precipitation bath while orienting. Method according to claim 1, characterized in that the shaped cellulosic body is further oriented by elongation or deep drawing.