KR19980701273A - MANUFACTURE OF EXTRUDED ATRICLES - Google Patents

Abstract

This invention extrudes the lyocell extrudates by extruding a cellulose solution in tertiary amine N-oxide into a coagulation bath (5) via an air gap (3) through which air is supplied and discharged using a mold (2). In manufacturing, the air gap 3 comprises a first zone adjacent the surface 2a of the mold 2 and a second zone 12 away from the surface 2a of the mold 2 and the first zone 9. ), The water content of the air to be supplied to the second zone 12 is maintained at a lower value than the water content of the air supplied to the second zone 12. According to the present invention the spinning property is improved and the fibrillation tendency of the lyocell fibers produced is improved.

Description

Extruded Manufacturing Method

U.S. Patent No. 4,261,943 cited in this invention discloses a solution of cellulose in an aqueous NMMO solvent into a 5-30 cm long air gap using a spinneret to form filaments and pass the resulting filaments into a coagulation bath. A solvent spinning method for producing cell fibers is described. The patent also describes a solvent-spinning method for coating filaments immediately after spinning in an air gap with a cellulose nonsolvent such as water. This process is known to reduce the tendency of the filaments to fuse together in the air gap.

WO-A-93 / 19230 describes a solvent-spinning process that allows the filaments in the air gap to be cooled by bringing them into contact with the cooling airflow before being introduced into the coagulation bath. In this case the temperature of the dope may be 90-110 ℃, the temperature of the cooling air may be -5 ℃ to +5 ℃, the length of the air gap may be 60-145mm.

The present invention relates to a method for producing a cellulose extrudates product by extruding a cellulose solution in tertiary amine N-oxide into a coagulation bath using a mold.

It is already known that dissolution of cellulose in tertiary amine N-oxides (hereinafter referred to as amine oxides for the sake of convenience) forms a solution or dope that can be extruded through a mold into a coagulation bath to form moldings such as fibers or films. . Generally, the dope contains a small amount of water, and the coagulation bath usually consists of an aqueous bath. The solidified product is washed with water to remove residual amine oxides. This process is one example of a solvent spinning process wherein the fibers produced by this process are called solvent-spun cellulose fibers or lyocell fibers. Examples of suitable amineoxide solvents are N-methylmorpholine N-oxides (NMMO).

The accompanying drawings are schematic views showing the arrangement of the apparatus used to practice the method of the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings.

According to the figure, the cellulose solution in the aqueous amine oxide is fed to the spinneret 2 using a gear pump 1. The dope comprises, for example, 5-25% by weight of cellulose, 70-85% by weight of NMMO and 5-15% by weight of water, and the temperature of the dope may be 80-150 ° C. The dope is extruded through the spinneret of the spinneret 2 into the air gap 3 maintained at a lower temperature than the dope to form a bundle of filaments 4. The filaments 4 are passed through an aqueous coagulation bath 5 and then through a roller 6 to flush, dry and other conventional processing steps. The surface speed of the roller 6 became faster than the speed of the dope exiting the spinneret of the spinneret 2 so that the filaments 4 were drawn. Stretching of the filaments mostly takes place in the air gap 3.

The primary supply of air is blown from the blowing nozzle 7 into the air gap of the first zone 9 adjacent to the spinneret 2 so that the air crosses the direction of movement of the filament 4, and to the suction nozzle 8; It is made to be discharged from the air gap (3). The nozzles 7, 8 are designed such that this process is operated to maintain the first zone 9 adjacent to the surface 2a of the spinneret 2 at the required values of ambient temperature and humidity. The secondary supply of air is blown from the blow nozzle 10 into the air gap 3 of the second zone 12 away from the spinneret 2 so as to be discharged by the suction nozzle 11. The nozzles 10, 11 were installed so that this process would maintain the required temperature and humidity in the second zone 12 located between the first zone 9 and the coagulation bath 5. The nozzles 7, 11 are formed long enough to supply air across the entire bundle of filaments 4. The water content of the air supplied from the blowing nozzle 7 is less than the water content of the air supplied from the blowing nozzle 10. The temperature of the two supplied air can be the same or different.

Although in the figure two air is supplied with different air into the air gap, it is also within the scope of the present invention to supply air with three or more different air into different zones of the air gap.

Fibrillation tendency of lyocell fibers can be measured by the following test method.

Test Method 1 (Sand Test)

A fiber skein comprising 100 to 200 filaments is cut into 5 mm lengths. The short fibers are placed in a 20 ml glass jar containing 4 g of fine glass beads, sealed and shaken for 20 minutes at 2800 cycles per minute in a swat flask shaker.

Several fibers are placed on a microscope slide. The fibrillation index (C _f ) is calculated from the micrographs of the fibrillated fibers. The total length f of the fibrils attached to the fiber length L is measured. The fibrillation index is calculated by the following formula.

(formula)

C _f = ∑f / L

This can be done manually or by image analysis. Separately, a set of micrographs can be prepared for comparison and the fibrillation index can be evaluated against the sample micrograph. Experienced fiber technicians may find this comparison method more convenient for fibrillation evaluation. In practice it is impossible to see a large number of fibrils, so it is impossible to measure a fibrillation index of 30 or more. Data is measured at 5 mm long fiber centers and ends. Experience has shown that the evaluation results for the fiber ends are most relevant to the fabric's performance, which is the number cited in the examples as C _f (TM1).

Test Method 2 (Refining and Dyeing)

The following method was used to evaluate the fibrillation index (F.I.). Fiber samples were arranged in increasing order of fibrillation degree. The standard length of the fiber in each sample is measured and the number of fibrils (hair brushed hair extending from the fiber body) appeared over the standard length. The length of each napping is measured and an individual value is given to each fiber by multiplying the number of fibrils by the average length of each fibril. The fiber with the highest arbitrary value is recognized as the most fibrillated fiber and given an arbitrary fibrillation index of 10. A fibrillation index zero (0) is given to a fiber that is not fibrillated at all, and the remaining fibers are between 0 and 10 depending on the degree of fibrillation, based on an arbitrary value measured using a microscope. To give.

The fibers measured by the method described above are used on a standard grade scale. To determine the fibrillation index for other fiber samples, five or ten fiber samples are compared with the standard scale fibers described above under a microscope. To determine the fibrillation index for the sample to be evaluated, the visually determined values for each fiber sample are averaged. It was found that the method of visual determination and averaging showed several times faster evaluation time than the direct measurement method, and the results of the fiber grade evaluation by skilled fiber technicians showed almost identical results.

The fibrillation index of a fabric can be estimated from the fibers taken from the surface of the fabric. Plain or knitted fabrics with an F.I. of 2.0 or greater than 2.5 have an unseen appearance.

Cut 1.7 dtex of lyocell fiber tow into 30mm staple fiber and spun with 20 tex yarn. The prepared yarn was knitted, refined, and then dyed in dark blue with 80 mm width. The knitted fabrics were washed at a temperature of 40 ° C. in a domestic washing machine and dried in a domestic tumble dryer. The fibrillation index is evaluated on the fibers taken from the surface of the dry fibers after refining and washing and after one or several washing and tumbling (W / T).

Test Method 3 (Measurement of viscosity and D.P of cuprammonium solution

This test is based on the TAPPI standard T206 os-63. Cellulose was dissolved in cuprammonium hydroxide solution (Sherry Institute standard solution) containing 15 ± 0.1 g / l copper and 200 ± 5 g / l ammonia and 0.5 g / l nitric acid. Solution of about 0.1%). The flow time of the solution passing through the sherry viscometer is measured, and the viscosity is calculated according to the standard method from this measurement. The viscosity average D.P. is determined by the following formula.

(formula)

D.P. = 412.4285 ln [100 (t-k / t) / n.C] -348

Where t is the flow time in seconds, k is the gravity constant, C is the tube constant, and n is the water density (0.9982 at 20 ° C) expressed in g / l at the test temperature.

In the following Examples, parts and ratios refer to parts by weight and parts by weight unless otherwise specified.

(Example)

Example 1

A spinning dope comprising woodpulp cellulose, NMMO 74-80% and water 7.5-12.6%, having various contents and degree of polymerization (D.P.) as described in Table 1 below is prepared. This spinning dope was solidified at 25 ° C. containing 25% NMMO and 75% water through an air gap of the length shown in Table 1 using a spinneret (head temperature 115 ° C.) having 95 spin holes of 80 micron diameter. Extruded into the bath to produce lyocell fibers. Air is supplied transversely to cross the filaments extruded from the top and bottom. The lateral blow height of the upper first zone was about 4 mm and the blower of the lower second zone was blown directly through the blower tube with a portable electric blower. When supplying the lower blower air stream to the first zone, a small amount of low pressure water vapor is mixed into the air flowing into the inlet of the blower pipe, thereby increasing the water content of the blower air stream to increase the relative humidity of the incoming air. The fiber passed through the coagulation bath was washed with water to remove NMMO and dried. Test Method 1 was then used to evaluate the fibrillation trend. Fiber samples were cut to make staple fibers and yarns spun. Yarn quality was visually rated from Grade 1 (very poor) to Grade 5 (very good). The experimental conditions and the results are shown in Table 1.

Table 1a

Cellulose (%) Cellulose D.P. Yarn quality C _f (TM1) filament adhesion

Spinning speed 60 m / min, air gap 20 mm, upper (first zone) blowing air 20 ° C / 0% R.H.

Lower (Second Zone) Blowing Air 20 ° C / 40% R.H.

15 850 4 5.5 None

15 630 5 6.5 None

15 472 5 9.4 None

12.5 630 4 5.9 None

10 850 4 5.3 None

Spinning speed 30 m / min, air gap 75 mm, upper (first zone) blowing air 20 ° C./0% R.H., lower (second zone) blowing air 20 ° C./40% R.H.

15 850 4 6.6 None

15 630 5 4.9 None

15 472 4 3.3 Some

12.5 630 3 4.1 Some

10 850 4 4.2 None

Spinning speed 30 m / min, air gap 150 mm, upper (first zone) blowing air 20 ° C./40% R.H., lower (second zone) blowing air 30 ° C./60% R.H.

15 850 3 3.2 Some

15 630 3 0.0 Slightly

15 472 2 0.1 Yes

12.5 630 1 0.0 Yes

10 850 1 2.5 Yes

Spinning speed 10 m / min, air gap 150 mm, upper (first zone) blowing air 20 ° C./0% R.H., lower (second zone) blowing air 20 ° C./40% R.H.

15 850 4 3.8 some

15 630 2 1.3 Severe

15 472 2 0.0 Slight

12.5 630 1 0.7 Yes

10 850 1 3.5 Yes

Table 1b

Cellulose (%) Cellulose D.P. Yarn quality C _f (TM1) filament adhesion

Spinning speed 10 m / min, air gap 75 mm, upper (first zone) blowing air 20 ° C / 40% R.H., lower (second zone) blowing air 30 ° C / 60% R.H.

15 850 4 0.0 None

15 630 3 1.5 Micro

15 472 2 0.0 Yes

12.5 630 1 2.1 Yes

10 850 1 4.8 Yes

Example 2

The method of Example 1 was repeated with dope containing 15.2% woodpulp cellulose (D.P.), 75% NMMO and 9.8% water. The prepared fibers were evaluated for fibrillation tendency using Test Methods 1 and 2. Test conditions and results are listed in Table 2.

Table 2

Air ℃ / RH% Quality C _f (TM1) Filament Adhesion FI (TM2)

Top bottom Refinement / Dyeing 1W / T

Radiation Speed 60m / min, Air Gap 20mm

-20/40 5 11.0 None 4.7 5.5

-30/60 5 9.0 none 4.7 6.0

Spinning speed 30m / min, air gap 150mm

-30/60 3.0 0.1 Yes 1.7 4.1

20/40 30/60 2.7 1.7 Yes 1.9 1.9

Radiation Speed 10m / min, Air Gap 75mm

-30/60 3.3 3.6 Some 2.5 3.5

60/40 30/60 4.0 0.7 None 1.0 2.0

Radiation Speed 10m / min, Air Gap 150mm

-20/40 1.3 1.2 Severe-

20/0 20/40 2.0 3.1 Yes 2.7 5.2

Experiments with a 20 mm air gap were made at a spinneret temperature of 110 ° C. Experimental results were averaged with only slight differences as the spinneret temperature at 90, 100 and 110 ° C. for longer air gaps.

Example 3

The method of Example 1 was repeated, but the temperature and relative humidity of the upper supply air were 20 ° C. and 40%, respectively, and the temperature and relative humidity of the lower supply air were 30 ° C. and 60%. The experimental conditions and the results are shown in Table 3.

Table 3a

Cellulose D.P. Cellulose% Spinning speed m / min Air gap mm Air speed m / sec Tow tension Radiation stability C _f 630 15 10 20 2 44 Great 3.8 630 15 10 20 8 53 Great 1.9 630 15 10 40 2 25 Bad 0.0 630 15 10 40 8 52 Great 0.0 630 15 10 80 2 45 Great 0.0 630 15 20 20 2 100 Great 7.1 630 15 20 20 8 165 Great 6.4 630 15 20 40 2 80 Bad 5.8 630 15 20 40 8 148 Great 3.0 630 15 20 80 2 69 usually 2.1 630 15 40 20 2 120 Excellent 10.6 630 15 40 20 8 150 Excellent 9.5 630 15 40 40 2 150 Excellent 6.2 630 15 40 40 8 225 Excellent 6.0 630 15 40 80 2 126 Great 5.4 850 13 10 20 2 57 Excellent 5.1 850 13 10 20 8 84 Excellent 3.0 850 13 10 40 2 65 usually 2.2 850 13 10 40 8 151 Great 0.2 850 13 20 20 2 110 Excellent 5.5 850 13 20 20 8 117 Excellent 1.0 850 13 20 40 2 90 Great 4.5 850 13 20 40 8 256 Great 6.0 850 13 40 20 2 140 Excellent 8.9 850 13 40 20 8 170 Excellent 6.8 850 13 40 40 2 130 Great 7.1 850 13 40 40 8 340 Great 6.0

Table 3b

Cellulose D.P. Cellulose% Spinning speed m / min Air gap mm Air speed m / sec Tow tension Radiation stability C _f 850 13 40 80 2 110 usually 5.4 850 15 10 20 2 240 Excellent 2.7 850 15 10 20 8 650 Great 1.4 850 15 10 40 2 250 Excellent 0.0 850 15 10 40 8 920 Bad 1.3 850 15 10 80 2 220 Great 0.6 850 15 10 160 2 310 usually 0.0 850 15 20 20 2 300 Excellent 5.8 850 15 20 20 8 900 Bad 6.0 850 15 20 40 2 220 Excellent 2.4 850 15 20 40 8 900 Bad 2.0 850 15 20 80 2 220 Excellent 0.2 850 15 20 80 8 280 Great 0.2 850 15 40 20 2 460 Excellent 4.6 850 15 40 20 8 1000 Bad 5.8 850 15 40 40 2 290 Excellent 5.4 850 15 40 40 8 800 usually 5.0 850 15 40 80 2 210 Excellent 0.0

Tow tension is any value, with higher values meaning higher tensions. Some sticky filaments appeared at longer air gaps and higher air velocities.

Example 4

Spinning dope is made comprising 13% cellulose (average D.P. 800), 75% NMMO and 12% water. Using a spinneret formed at 83 ° C., 18,400 spinnerets having a diameter of 70 microns were spun into a coagulation bath containing 25% of NMMO and 75% of water through an air gap using a spinneret formed of three rows of 1 m in length. Prepare filament tow. Two air streams are blown in the transverse direction to cross the tow. The upper air is supplied at a flow rate of 12 m / sec using a 5 mm blow nozzle adjacent to the spinneret, and the lower air is installed at the lower part of the air gap. It is supplied at a flow rate of 9 m / sec using a 25 mm blowing nozzle. The supplied air is sucked and discharged at the same speed by using suction nozzles installed on the opposite side of each blowing nozzle. The relatively dry top feed air has a temperature of 20 ° C. and a relative humidity of 40% (dew point 6 ° C.), and the relatively wet bottom feed air has a temperature of 28 ° C. and a relative humidity of 78% (dew point 24 ° C.). The spinning properties and safety were excellent. When the upper air supply was discontinued, the radiation characteristics immediately deteriorated and the upper air had to be re-supplied quickly to prevent the tow from being cut in the coagulation bath (loss of radiation safety).

The present invention provides a method for producing a lyocell extrudates in which a cellulose solution in a tertiary amine N-oxide is extruded into an unheated bath through an air gap through which air is supplied and discharged using a mold. Lyocell extrusion, having an adjacent first zone and a second zone away from the surface of the mold, the moisture content of the air supplied to the first zone being maintained at a lower value than the water content of the air supplied to the second zone It consists of a method of preparing water.

The extruded lyocell product may be in the form of a film or in the form of filaments (including tow and continuous filament yarns that can be cut to make staple fibers). If the product is a filament, the mold is called a spinneret, The extrusion process is commonly called spinning.

The length between the mold and the coagulation bath is preferably in the range of 10 to 160 mm, but more preferably in the range of 15 to 100 mm, especially 20 to 60 mm. The gas in the above-mentioned air gap is preferably air, but other inert gases or gas mixtures such as nitrogen may also be used.

The two zones of the air gap may be the same length or may differ. For example, it may be desirable for the length of the first zone to be less than the length of the second zone, in which case the first zone is 3 to 10 mm long and the second zone is used to It's good to have it.

The cellulose solution (also called dope) is extruded downward through the air gap. Air is supplied and discharged into the air gap in the transverse direction of the dope extrudate passing through the air gap, ie in the horizontal direction when conventional extrusion techniques as described above are used. In such a lateral arrangement, the air flowing across the air gap can be called the lateral wind. The speed of the air supplied to the two zones of the air gap is preferably in the range from 1 to 20 m / sec, in particular from 2 to 10 m / sec. The feed rate of air should be high enough to maintain different air pressure conditions around the dope extrudates in the two zones of the air gap but not too high to interfere with the passage of the normal dope extrudate. In general, for long air gaps, too high an air supply speed can interfere with the flow path of the extrudate. The velocity of the air supplied to the first and second zones of the air gap may be the same or may be different. The appropriate air velocity can be determined by simple experiments to meet the appropriate conditions depending on the extrusion conditions.

Emission of air from either or both zones of the air gap can be achieved by suction. Air can be supplied to and discharged from the air gap using a suitably designed blower and suction nozzle. The first and second zones of the air gap require separate blowers. However, the suction nozzle may be one or more than two. A preferred example is that the nozzles of each blower are positioned opposite the suction nozzles of similar capacity. Such a configuration has the advantage that it is easy to control the air pressure conditions around the dope extrudates passing through the respective sections of the air gap. In particular, such a configuration can be advantageously used when the length of the first zone is shorter than the length of the second zone.

The temperature of the air supplied into the air gap may be in the range of ambient temperature, for example 0-40 ° C., in particular 20-30 ° C. The temperature of the dope fed to the mold is usually in the range of 80-125 ° C., so the air supplied into the air gap serves to cool the extrudate in the air gap. In conventional extrusion methods, the rate of withdrawing the extrudate from the coagulation bath is faster than the rate of extrusion of the dope through the mold. In the case of stretching for the purpose of improving mechanical properties, the speed difference may be set to have a function in the range of 2.5 to 25. In this case, stretching occurs in almost the entire area of the air gap. In some cases, the extrudate cooling in the air gap limits the zone where the stretching occurs so that the stretching occurs only in the air gap portion adjacent to the surface of the mold. The extrusion rate of the extrudate is preferably 5 to 10 m / min.

The water content of the air supplied to the second zone of the air gap is preferably made to be 1 to 30 g of water per kg of air, in particular about 10 to 20 g more than the water content of the air supplied to the first zone. The water content of the air supplied to the first zone of the air gap is preferably 0 to 20 g, in particular 0 to 10 g of water per kg of air, in which case the water content of air to the second zone is 5 to 30 g of water per kg of air. It is good.

In general, lyocell fibers tend to fibrillate when subjected to mechanical stress during high temperature wet processing during fabrication such as refining, bleaching and dyeing processes. When fibrillated, the long fibrils may be partially separated from the fiber surface, resulting in an undesirable hairy appearance on the individual fibers as well as the yarns and fabrics containing them. However, the fibers produced by the present invention show less tendency to fibrillate than the fibers produced by conventional spinning methods. During solvent-spinning, extrudates, particularly filamentous extrudate, are cut in the air gap. Cleavage of such extrudate results in a lack of spinning stability or poor radioactivity. Coarse radioactivity can be easily demonstrated by observing the cut filaments contained in the collected product, as well as by the interruption of radiation in the air gap or coagulation bath. It has been found that the method of the present invention exhibits better spinning stability in conventional methods, in particular in the spinning method of spinning through a long air gap. Although these effects are difficult to quantify, they can be easily confirmed by observation.

The average degree of polymerization (D.P) of cellulose in the dope state is generally in the range from 250 to 2000, but is preferably in the range from 500 to 2000, in particular from 750 to 1000. Good radioactivity can be obtained under a wide range of conditions when the cellulose polymerization degree is in the range of 750 to 1000. The degree of cellulose polymerization (D.P) can be measured simply by measuring the viscosity of a dilute cellulose solution in an aqueous metal / amine complex solvent, such as cuprammonium hydroxide solution. Suitable methods based on TAPPI Standard T206 are described in Test Method 3 below. Cellulose degree of polymerization is expressed as the number of anhydroglucose units per molecule. The degree of polymerization (D.P) measured by this method is the viscosity average D.P.

Claims (14)

A method of making a lyocell extrudates by extruding a cellulose solution in a tertiary amine N-oxide into a coagulation bath through an air gap through which air is supplied and discharged using a mold, wherein the air gap is adjacent to the mold surface. A method for producing lyocell extrudates, comprising a first zone and a second zone away from the mold surface, wherein the water content of the air supplied to the first zone is maintained at a lower value than the water content of the air supplied to the second zone. . Method according to claim 1, characterized in that the length of the air gap is in the range of 10 to 160 mm, in particular 20 to 60 mm. The method of claim 1 or 2, wherein the length of the first zone is less than the length of the second zone. 4. A method according to claim 3, wherein the length of the first zone is in the range of 3 to 10 mm. Method according to one of the preceding claims, characterized in that the flow rate of air supplied to the first and second zones is in the range of 1 to 20, in particular 2 to 10 m / sec. Method according to one of the preceding claims, characterized in that air is supplied into the first zone and the second zone in the transverse direction to cross the direction of movement of the extrudate through the air gap. Method according to one of the preceding claims, characterized in that air is supplied into the first zone and the second zone of the air gap by separate blowing nozzles for the two zones. 8. The method of claim 7, wherein the air is discharged from the air gap by a single suction nozzle positioned opposite the blowing nozzles. 8. A method according to claim 7, wherein the air is discharged from the air gap by separate intake nozzles of similar capacity as the blow nozzles located opposite each of the blow nozzles separated from each other. Method according to one of the preceding claims, characterized in that the water content of the air supplied to the second zone is 1 to 30, in particular 10 to 20 g, of water per kg of air than the sum of the air supplied to the first zone. . Method according to one of the preceding claims, characterized in that the water content of the air supplied to the first zone is in the range of 0 to 20 g, in particular 0 to 10 g of water per kg of air. Method according to one of the preceding claims, characterized in that the water content of the air supplied to the second zone is in the range of 5 to 30 g of water per kg of air. The method of any one of the preceding claims, wherein the average degree of polymerization of cellulose in solution is in the range of 750 to 1000. The method of claim 1, wherein the extrudate is in the form of a lyocell filament.