US2703270A - Production by spinning of cellulose hydrate filaments - Google Patents

Description

United States Patent PRODUCTION BY SPINNING OF CELLULOSE HYDRATE FILAMENTS Martin Studer and Louis Willimann, Emmenbrucke, near Lucerne, Switzerland, assiguors to Societe de la Viscose Suisse, Emmeubrucke, near Lucerne, Switzerland, :1 Swiss body corporate.

No Drawing. Application July 28, 1952, Serial No. 301,364

Claims priority, application Great Britain July 31, 1951 Claims. (CI. 18-54) The present invention relates to a spinning process for the production of filaments of all kinds from viscous solutions which are characterised by a highly oriented crystalline structure and in consequence a high tensile strength, and to the filaments so obtained. The term filaments as used herein is to be understood to. cover multiple and single filaments, fibres, small ribbons and foils.

It is possible to produce viscose filaments having a relatively high stretching capacity and tensile strength up to about 3.5 g./den. in the dry condition and about 2.0 g./den. in the wet condition. This is frequently achieved by softening and simultaneously stretching the freshlyspun thread in one or more baths at temperatures which may be, for example, higher than 70 C. Other processes employ spinning baths which either have a high content of, zinc sulphate or have, a minimal coagulating action on the viscose solution. The object of all these processes is to make it possible to subject the thread to a high degree of stretching during the spinning, operation itself or immediately after that operation. However, there is 111 practice a limit. to the amount of stretch that can. be eftected since the filaments, due to frequent breakage, cannot be stretched beyond a critical tension without damage or loss of quality. By increasing the stretch eifected during spinning, an improvement in the crystalline structure and the orientation of the macromolecules can be efiected but it has not hitherto been possible with any viscose process, because of frequent interruptions due to br'eakages, to exceed a stretch of about 150%. On the other hand, filaments of. cellulose acetate can be stretched and simultaneously saponified to cellulose to yield filaments of well developed. crystalline structure and good orientation. It is possible that av stretching action with simultaneous saponifica-tion of ester groups assists the crystallization of the cellulose and the orientation of the micelles or crystallites.

According to the present invention a processv for the production of filaments of high stretching capacity and high tensile strength comprises spinning through spinnerets a viscose of gamma number above 60 in such a manner that the degree ofpolymerisation of the filament is above 300 into a spinning bath of low electrolyte content and stretchingthe filaments continuously with their formation, the spinning being effected at room temperature and the stretching of the filaments being effected so that the speed of travel of the filaments afiter such stretching is not greater than 12 metres/ minute.

The gamma number is the number of mols of CS2 combined per glucose radical multiplied by 100. Viscose solutions of gamma number above 60 may have a cellulose content of about 4 to 11% by weight and a caustic soda con-tent of about 3 to 12% by weight, that is to say, they are of normal composition. Wood pulp or linters or othervcellulose products employed in the viscose industry are used as cellulose-containing starting materials. The production of the viscose solutions is eifected in the usual manner. Cellulose xanthate containing cellulose of high molecular weight is particularly useful and is obtained by treating a material containing cellulose of high molecular weight with caustic soda and omitting the ripening of the alkali cellulose. The average degrees of polymerisation of the cellulose hydrate regenerated from the alkali cellulose or the viscose are, in accordance with this invention, above 300. 7

These viscose solutions are spun into baths which have a weak coagulating action, a low sulphuric acid content and a relatively low electrolyte content and which are operated at room temperature, by which is meant about 10 to 25 C. The sodium sulphate concentration is preferably kept below 100 g./lt. Such metal salts as Zinc sulphate, iron sulphate, aluminium. sulphate and magnesium sulphate which tend to reduce the stretchability of the filament are avoided. The sulphuric acid concentr ation is preferably 1 0 to 40 g./lt. Substances such as lau'ryl pyridium chloride or sulphate, which facilitate spinning may be added to the spinning bath. Whenv viscose solutions having relatively high gamma numbers are spun into such baths, filaments are produced. which are clearly different from those which are spun from the so-called Miiller baths (containing 10-14% H2804 20-25% NazSOr, 0.5-2.0% ZnSO4; operated at temperatures 4050 C.). The products have an almost circular cross-section and although this is not specific solely for the conditions of the, present process, there is no indication in the present products of the so-called double layer that can easily be observed, using, the phase-contrast microscope, in viscose fibre cross-sections made. with Miiller baths and subsequently coloured. On the other hand very small dots are revealed by microscopic examination of the fibre cross-section and these probably correspond to micropores. The filaments obtained may be stretched, in, accordance with the invention by more than 1.50% and preferably. 200% to 400% if individual filaments of less. than 10 denier are required. For the production. of single filaments, or small ribbons or the like above 10 denier, the stretch must be reduced.

It has surprisingly been found, and this is a characteristic feature of the present invention, that these high speed is employed. The speed of the filaments after the, stretching operation is, less than 12 metres per minute and preferably 4 to 7 metres per minute. For a stretch of 200-400% at 4 to 7 metres per minute final speed it is necessary on the one hand to make the distance between the spinneret and the point where the stretch is initiated as. small as possible and, on the other hand, to establish arninimum period of 3 seconds during which the thread is. subjected to tension. The necessity for these stretching conditions may perhaps be explained on the. theory that the high degree of stretch is only possible and elfective when the filament to bestretched has a relatively high concentration of Xant-hate groups and that the stretching tension must be elfective while a relatively large part of these Xanthate. groups is. being split off. The distance between, the spinneret andthe place where the stretching is initiated may be adjusted, within the abovedescribed limits according to the gamma number of the viscose solution at the composition. and temperature of the spinning bath. In this connection, the lower the concentration of the ester groups at the point where the stretching commences, the

shorter the aforesaid distance needs to be, and vice The stretching may be effected in any suitable man.-

ner, within the limits described above as essential to the process of the present lnvention. For example the filament can be stretched by friction by means of tubular rods or between driven rolls or pairs of rolls rotating at different peripheral speeds or by a combination of both systems. During the stretching the filament can move forward partially or wholly in the spinning bath or partially or wholly in the air.

spinneret and according tothe.

An advantageous methods.

is that in which stretching is effected during the air path. The filament can be drawn off vertically or horizontally through the spinning bath from the spinneret, or at any intermediate angle. The spinnerets are of the usual construction. Where multiple hole spinnerets are employed, they are so located that the gases formed during the spinning may readily escape. The stretched filaments are spooled in any suitable manner.

The following data give a picture of the importance of the spinning or stretching speed in accordance with the invention. Using one and the same viscose solution and always the same bath composition a multiple filament of 300 denier was spun with different degrees of stretch.

In the experiments indicated in the following tables, a sulphite pulp with 89% a-cellulose content was employed. The viscose solution was adjusted to 6.1% cellulose and 7.7 caustic soda content. Its gamma number at the moment of spinning was 75. The cellulose regenerated from the viscose solution had a degree of polymerisation of 650. The spinning bath contained 20 g. sulphuric acid and g. sodium sulphate per litre. Its temperature was C. and the thread of 300/200 den. The holes of the spinneret had a diameter of 0.07 mm., the bath path was 10 cm. and the distance between the spinneret and the place where the stretching commenced was 40 cm. Stretching was carried out in air between two driven stretching rolls, the spacing of which was 120 cm. The threads were spooled with very slight tension on rollers and then washed free from acid, de-sulphurised, soaped and dried. The following measurements were made on the dried test pieces.

TABLE I Desired degree of Breaking strength, in g./den.

Elongation at rupture, in

Speed of the thread after the percent second Stretching roll, in

m'lmul strgich,

percent wet dry wet 1 Maximum possible stretch for continuous spinning.

TABLE II Speed of the thread after the second stretching roll, in m./min.

Desired degree of stretch. in percent Breaking strength in g./den.

Elongation at rupture, percent Swelling in water of 20 C. in

percent of the dry weight Test No dry wet dry wet Maximum possible stretch for continuous spinning.

It is apparent from the results of Table I how the breaking strength and elongation at rupture of the filaments under the conditions characteristic of the invention increase with decreasing spinning speed when the stretch is constant. The result may be compared with the first line in which the spinning speed is m./min., with which however it was possible to obtain a maximum stretch of only 150%. In the other forms, a stretch of 240% does not in any way represent the maximum. The breaking characteristics of the filaments may be taken as a measure of the degree of organisation of the structure.

It is apparent from the results of Table II how, under the conditions characteristic of the invention, with a spinning speed of 3.14 m./min., an increase of the stretch to the maximum permissible amount acts favourably on the organisation of the filament structure. This satisfactory arrangement is apparent from the high breaking characteristics and also from the low swelling of the filament of Test B. The determination of the degree of swelling is carried out in the following manner: 0.5 g. of thread were cut into short fibres and placed for one hour in distilled water at 20 C. and then centrifuged at 20 C. in a centrifuge with diameter of 31 cm. for 20 minutes and at 3,000 R. P. M. Finally the water content was determined of'the' product of constant weight obtained by drying at 105 C. In addition, an X-ray diagram with CuK a-radiation was made on test piece B. A diagram was obtained with a large number of clearly perceptible reflections of the first, second, third and fourth layer lines. The intensity and length of the interferences show up a very high proportion of crystallised cellulose and a very high degree of orientation of the crystallites such as has not been known hitherto with viscose filaments.

The invention is illustrated by the following examples which however, are not to be regarded as limiting it in any way:

Example I A sulphite pulp with 89% content of a-cellulose is mercerised at 18 C. and then shredded at 0 C. The alkali cellulose is then immediately xanthogenated for 2 /2 hours with 60 parts CS2 to 100 parts a-cellulose and dissolved by stirring in four hours at a temperature of 5 C. After dissolving, the gamma number is 75. The viscose solution containing 6.1% a-cellulose and 7.7% NaOI-I is filtered, deaerated and spun with a gamma number of 70 and at a viscosity of 220 poises (measured at 20 C.).

A filament bundle of 10,500 den. with 7,000 individual filaments is spun from a spinneret, the holes of which have a diameter of 0.07 mm. The spinning bath contains 18 g. H2804, 90 g. NazSOr and 2.5 mg. lauryl pyridinium sulphate per litre. Its temperature is 20 C. and the bath path 10 cm. The distance between the spinneret and the point at which stretching commences is 30 cm. Stretching is carried out between driven rolls which are arranged at a distance of 120 cm. from one another. The degree of stretch is 300% and the spinning speed after stretching 5 m./min. The tension on the bundle with a stretch of 300% amounts to 0.78 g./den. The bundle is drawn off vertically from the spinning nozzle and then vertically towards the stretching members. The bundle produced in this manner is relieved of tension after the stretching and is continuously cut to 40 mm. staple lengths in the acid condition. The fibres are washed free from acid and salt in the usual manner, de-sulphurised, treated with an aqueous solution containing for example 5 g./litre cetyl alcohol sulphate and dried. The fibres have the following properties:

Breaking strength dry g./den 4.1 Breaking strengthwet g./den 3.76 Elongation at rupturedry per cent 12 Elongation at rupture-wet do 14 Swelling do 70 Degree of polymerisation 600 These fibres of 1.5 den. have an almost circular, nonserrated cross-section. In the phase-contrast microscope, no double layers in the cross-section are to be observed, but instead point-like dots are revealed. The fibres can be spun into yarns by the cotton process.

Example II The preparation of the viscose solution is carried out in the same manner as in Example 1.

The viscose solution is spun from a spinneret with 200 holes having a diameter of 0.07 mm. to form a thread of 300 den. into a spinning bath which contains 20 g. H2804 and 15 g. NazSO4 per litre and has a temperature of 18 C. The bath path is 3 cm. The distance between the spinneret and the point at which stretching commences is 23 cm. The thread is drawn vertically from the spinneret and stretched horizontally between two driven rolls which have a spacing of cm. The stretching amounts to 280% and the spinning speed after the stretching 4.7 m./min. The thread tension during the stretching is 0.9 g./den.

The thread is wound with light tension on to a roller and finished in the usual manner. After the drying, it is twisted on a ring spinning machine at turns per The percentage amount of the elastic elongation in the dry condition to the total elongation was determined on a Scott tester, maintaining a recuperation period of one minute after each loading:

Elastic elongation in percent of the total elongation :3 in

The dye-absorbing capacity of this thread has been compared with bleached cotton and with a commercial viscose thread of 120/80 den. with 97% swelling prepared by spinning into a Muller-type bath.

Dye solution 4.32 g./lit. solar blue GLN. Bath ratio 1:800.

Dyeing temperature 60 C.

Time 16 minutes.

The dye absorption in mg. per kg. thread or fibre respectively is 530:21 for the thread with 65% swelling spun in accordance with Example II, 300$ 12 for bleached cotton, 530:21 for viscose thread of 120/80 den. with 97% swelling.

Despite the low swelling capacity of thread spun in accordance with Example II, the dye absorption capacity is better than with bleached cotton and the same as with normal viscose fibre.

Example III The same viscose solution is used as in Example 1, except that 0.8% titanium dioxide per kg. a-cellulose are added to it.

A bundle of 19,500 den. comprised of 1300 individual filaments of den. is spun from the spinneret, the holes of which have a diameter of 0.12 mm. The spinneret is disposed in a bath which contains 60 g. H2804 and g. Na2SO4 per litre and which has an internal temperature of 22 C. The length of the bath is 30 cm. The bundle is drawn OE With an upward inclination of about 30. Directly above the bath, it is stretched by passing over and under 4 successive rods in such a manner that the braking action takes place. It is then conducted into a stretching device according to Example I. The stretching between driven rolls, which follows the stretching due to the braking action, is 150%. The final speed of the thread is 5 m./niin.

The bundle is then cut into staple lengths of 100 mm. The fibres are finished in a manner similar to that set out in Example I.

Properties:

Breaking strength-dry 2 g./ den. Breaking strength--wet 1.5 g./den. Elongation at rupture-dry 12%. Elongation at rupture-wet 15%. Cross-section Roundish with smooth edges.

Swelling 69% The relatively low swelling of this fibre indicates a wellorientated structure which is remarkable for relatively coarse fibres. These fibres can be used for carpet yarns.

Example IV Linters pulp is mercerised in the usual manner in 18% NaOI-I and squeezed out in order to produce an alkali cellulose containing about 31% a-cellulose and 15.5% NaOH. This alkali cellulose is shredded for 110 minutes at 0 C. and immediately xanthated with 65 parts CS2 per 100 parts a-cellulose. The xanthate is then dissolved in a beater device at 7 C. to form a viscose solution with 7.2% cellulose and 5.7% NaOH. The filtered and deaerated viscose arrives at the spinneret with a gamma number of 70. It then has a viscosity of 370 poises (measured at 20 C.). A thread of 1100/480 den. is spun, using spinnerets having holes with a diameter of 0.085 mm. The spinning bath contains 20 g. H2804 and 1 g. NazSOs per litre. It has a temperature of 20 C. The thread is drawn off vertically through the bath. The first driven stretching member is disposed in the spinning bath. The total length of the path of the thread in the bath is 45 cm., the distance between spinneret and the point where the 6 stretching commences is 5 cm. and the distance between the two driven stretching members is 120 cm. When the speed of the stretched thread is 3 m./min., the degree of stretching is 310%.

The finished thread, twisted with turns per metre, has the following properties: a

Breaking strength-dry g./den 5.1 Breaking strengthwet g./den 4.5 Elongation at rupture-dry per cent 7.3 Elongation at rupture-wet do.. 7.5

The thread can be used for tyre cords. We claim:

1. A process for the production of filaments of high organisation and high tensile strength having a degree of polymerisation above 300 which comprises extruding through spinnerets a viscose of gamma number above 60, the cellulose generated from said viscose having a degree of polymerisation above 300, into an aqueous spinning bath at room temperature containing only from 10-40 g./ litre of sulphuric acid and at most 100 g./ litre of sodium sulphate, and stretching the filaments about 240% continuously with their formation giving a final speed of 12 meters at most per minute, the filaments being maintained continuously under tension.

2. A process for the production of filaments of high organisation and high tensile strength having a degree of polymerisation above 300 which comprises extruding through spinnerets a viscose of gamma number above 60, the cellulose generated from said viscose having a degree of polymerisation above 300, into an aqueous spinning bath at room temperature containing only from 10-40 g./ litre of sulphuric acid and at most 100 g./ litre of sodium sulphate, and stretching the filaments continuously with their formation giving a final speed of 4 to 7 meters per minute, the filaments being maintained continuously under tension.

3. A process for the production of filaments of high organisation and high tensile strength having a degree of polymerisation above 300 which comprises extruding viscose at room temperature through spinnerets into an aqueous coagulating bath, the viscose having a gamma number above 60, generating cellulose having a degree of polymerisation above 300 and having a cellulose content of 4 to 11% by weight and a caustic soda content of 3 to 12% by weight, the aqueous coagulating bath containing only from 10-40 g./litre of sulphuric acid and at most 100 g./litre of sodium sulphate, stretching the filaments about 240% continuously with their formation giving a final speed of 12 meters at most per minute, the filaments being maintained continuously under tension.

4. A process for the production of filaments of high ganisation and high tensile strength having a degree of polymerisation above 300 which comprises extruding through spinnerets a viscose of gamma number above 60, the cellulose generated from the said viscose having a degree of polymerisation above 300, into an aqueous coagulating bath at room temperature containing only from 10 -40 g./litre of sulphuric acid and at most 100 g./litre of sodium sulphate, and stretching the filaments in the coagulating bath about 240% continuously with their formation, the filaments being maintained continuously under tension, the stretching of the filaments being initiated at a point not more than 60 cm. from the spinnerets and the final speed being not greater than 12 meters per minute.

5. A process for the production of filaments of high organisation and high tensile strength having a degree of polymerisation above 300 which comprises extruding through spinnerets a viscose of gamma number above 60, the cellulose generated from said viscose having a degree of polymerisation above 300, into an aqueous coagulating bath at room temperature containing only from 10-40 g./litre of sulphuric acid and at most 100 g./litre of sodium sulphate, and stretching the filaments about 240% during a period of 3 seconds at least continuously with their formation giving a final speed of 12 meters at most per minute, the filaments being maintained continuously under tension.

Underwood Dec. 24, 1946 Drisch et al. Aug. 26, 1952

Claims (1)

1. A PROCESS FOR THE PRODUCTION OF FILAMENTS OF HIGH ORGANISATION AND HIGH TENSILE STRENGHT HAVING A DEGREE OF POLYMERISATION ABOVE 300 WHICH COMPRISES EXTRUDING THROUGH SPINNERETS A VISCOSE OF GAMMA NUMBER ABOVE 60, THE CELLULOSE GENERATED FROM SAID VISCOSE HAVING A DEGREE OF POLYMERISATION ABOVE 300, INTO AN AQUEOUS SPINNING BATH AT ROOM TEMPERATURE CONTAINING ONLY FROM 10-40 G./LITRE OF SULPHURIC ACID AND AT MOST 100G./ LITRE OF SODIUM SULPHATE, AND STRETCHING THE FILAMENTS ABOUT 240% CONTINUOUSLY WITH THEIR FORMATION GIVING A FINAL SPEED OF 12 METERS AT MOST PER MINUTE, THE FILAMENTS BEING MAINTAINED CONTINUOUSLY UNDER TENSION.