CA1098667A - Hygroscopic fibers and filaments - Google Patents

Abstract

ABSTRACT
The wearing comfort of textiles produced from synthetic fibers which are normally hydrophobic, e.g.,polyacrylonitrile, is improved by modifications in the spinning process whereby hygroscopic fibers having a sheath/core structure and a microporous core are obtained, which fibers are capable of absorbing considerably more water than conventionally dry spun fibers of the same synthetic polymer not having a sheath/core structure.
Several suitable dry spinning processes for producing the improved fibers are disclosed.

Description

Textile materials used for the pro~uction of clothing should pro-vide good wearing comfort and must also possess, a number of other desirable properties. To achieve wearing comfort it is necessary that the human body be kept warm when inactive and when ackive that the heat and humidity gener-ated, in gaseous and in liquid form, be permitted to escape from the body.
It is specifically desirable to maintain a dry atmosphere near the body sur-face. Synthetic polymers provide many desirable textile properties but are generally deficient as to the comfort qualities required for clothing. It has now been found that outstanding wearing comfort can be achieved with a textile fiber prepared from a synthetic polymer by changing its physical properties during spin~ing to provide a fiber with a minimum water retention capacity and a minimum porosity, wherein the polymer from which the fiber is produced es-sentially does not swell when the fiber pieks up water.
The present invention relates to fibers and filaments of filament-forming synthekic polymers~ whieh have exeellent hygroscopic properties and which give good wearing comfort when fashioned into articles of clothing.
The hygroscopic properties and wearing comfort are primarily due to the physical makeup of the fibers which have a sheath/core structure, a porosity of at least 10%, a water retention capacity of at least 10%, and a fiber swelling which is lower than the water retention capacity~
~hus this invention provides a hygroscopic or hydrophilic filament - or Mber of a fiber-forming synthetic polymer having a water permeable sheath and a microporous core in whieh both the sheath and the eore contain voids, the voids in the core forming an inter-eonnected system open to liquids through voids in the sheath and ln which the average size of the voids O
the core is at most 10,000 A and is significantly larger than the size of the voids in the sheath; a water retention capacity of at least 10%, a porosity of at least 10%; and a fiber-swellability of at most 10% which is lower than the water retention eapaeity.
The polymers used for the production of the filaments and fibers aeeording to the invention are espeeially those whieh normally would be :

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hydrophobic polymers, for example, polyamides, especially aro~atic polyamides,polyesters, polyvinyl halides, but preferably acrylonitrile polymers which contain at least 40% by weight and more preferably at ]east 85% by weight of acrylonitrile units.

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i7 The term "sheath/core struc~ure" as used herein is understood to refer to a structure which when observed in a stereo scan electron microscope, exhibits a distinct difference between the outer surface (sheath) and the inner portion of the cross-section ~core) as compared to fiber samples pre-pared by conventional methods which are substantially uniform in cross-section. Specifically, the fibers of this invention contain voids and -the voids observed in the core on the average are significantly larger than those in the sheath. Particularly, in one embodiment the sheath appears to be com-p act, which means it contains essentially no voids having a diameter larger than 300A.
The thickness of the sheath is determined as the distance between the outer surface and that point where the said difference in struc-ture is observed (when perpendicularly going from the outside to the middle of the fiber). The proportion of the sheath of the cross-section area of the fibers and filaments according to this invention amoun~s to 5-80% and preferably of from lO to 50%.
According to one embodiment of this invention, the fibers and filaments exhibit an average ~oid diameter of at most 10,000 A, preferably of at most ~,000 A and most preferably of at most Z,000 A. The voids in the core form aninterconnected system (essentially no isolated voids) which is open to liquids, e.g., water, even through the sheath. Indeed, it is essen-; tial for the fibers and filaments according to this invention that the liquid pick-up not only occurs through the fiber ends bu~ also through channels in -. -the sheath.
The swellability of the fibers and filaments according to this ; invention preferably is significantly lower than the water retention capacity.
The swellability, for example, should not exceed about 3% if the water retention capacity is about 10%. Even if the water retention capacity is higher, for example, 50-100%, the swellability should not exceed about 10%.
An acrylonitrile copolymer consisting of 90% of acrylonitrile, 5.5% of methyl : :
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136~7 acrylate and 0.5% of sodium methallyl sulfonate shows a swellability Q of

2.5%. Of course, the swellability depends on the chemical composition of the polymers. According to this invention, only those polymers having a swell-ability of at most 10% are used.
The porosity of the fibers and filaments according to this inven-tion is at least 10% and preferably at least 17%. The water retention capacity preferably is more than 20%.
(A) The fibers and filaments according to this invention can be pro-duced, as indicated above, by modifying a spinning process which is known per se, preferably a dry-spinning process. In this process a solution is spun which contains in addition to the polymer and the spinning solvent as is conventional, from 5 to 50% by weight based on solvent and polymer solid of a substance which is essentially a non-solvent for the polymer and which is readily miscible with the solvent and with water or another liquid which is suitable as a washing liquid for the filaments. Care is taken that the non-solvent Is not vaporized to any substantial extent during the spinning pro-cess. Thereafter, the non-solvent is washed out of the fibers.
If acrylonitrile polymers are used, the hydrophllicity even can be enhanced by using copolymers having hydrophllic groups. Suitable compounds are acrylic acid, methacrylic acid, methallyl sulfonic acid and its salts as well as acrylic acid amides.
As spinning solvent especially suitable, are those which are well-known in the dry-spinning technique such as dimethyl acetamide, dimethyl sulfoxide, N-methyl pyrrolidone, and dimethyl formamide (DMF). Dimethyl form-amide (DMF) is preferred.
The substance added to the spinning solution must be mlscible - with the solvent and with water or another liquid being suitable as a washing liquid for the filaments, preferably miscible at any ratio, and it must be a non-solvent for the polymer in a practical sense whlch means that the polymer is insoluble or is soluble in said substanee at most in a minor amount.

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Suitable substances are mono or polysubstituted alkyl ethers and esters of polyvalent alcohols, such as diethylene glycol mono- or dimethyl ether, or the appropriate ethyl or butyl ethers, diethylene glycol, triethy-lene glycol, tripropylene glycol, triethylene glycol diacetateg tetraethylene glycol, tetraethylene glycol methylether, glycol ether acetates, such as butyl glycol acetates. Also suitable, are high-boiling alcohols such as 2-ethyl cyclohexanol, esters, ketones and mixtures thereof. Preferably, gly-cerin and tetraethylene glycol are used. Solid substances such as sugars or solid polyvalent alcohols are suitable as well.
It is further advantageous to use substances that do not form azeotropic mixtures with the spinning solvent so that they can be regained to a large extent by fractional distillation as in the case of ~MF/glycerin or DMF/diethylene glycol mixtures.
Those substances are added to the spinning solution in an amount -of 5-5Q%, preferably 10-20% by weight, based on solvent and polymer solids.
The upper limit thereby in practice is governed by the spinnability of the resulting solution. The higher the percentage-by-weight ratio of the added substance is the higher the porosity of the core in the fibers can be and accordingly the higher is the water retention capacity of fibers produced from such spinning solutions.
To obtain the fibers and filaments according to this invention having a favorably high porosit~ the spinning conditions are selected in such a way that as little as possibIe of the added substance is vaporized or car-ried out with the sol~ent in the spinning tube during the dry-spinning process.
For this purpose it :is desirable that the temperature of the spinning tube be as low as possible and o~ly a little above the boiling point of the spinning solvent, and that short spinning tubes and high spinning speeds be used to ensure short residence times of the filaments in the spinning tube.
For these reasons the temperature of the spinning tube should be at most S~C
above, preferably from 5 to 30C, above the boiling point of the spinning

- 4 -solvent used. T~rough these conditions the essential amount (normally about ~0%) of said substance remains in the ereshly spun filaments or the bundles of filaments, respectively. Then, later during the after-treatment of the filaments said substance is removed by washing it out and the Eilaments are made up in a conventional manner to yield filaments or fibers ready Eor use.
The wash-out step may be conducted at a temperature up to 100C.
The residence time of the filament in con-tact with the washing liqu-id should he at least 10 seconds to ensure a proper wash out.
It has been found to be advantageous to ]ceep the filaments only under low tension or to allow only a low shrinkage, respectivelv, during the wash out. This ensures an optimum wash-out.
Further after-treatment of the filaments or s~rands is conducted in a conventional manner such as treating them with an oil, crimping, drying and optionally cutting it.
The drying has a further influence on water take-up. Therefore, the drying conditions should be as mild as possible. A drying temperature of at most 160C, preferably oE from 110 to 1~0C and short residence times of ~ the filaments in the dryer of as short as 2-3 minutes yield sheath/core fibers ; or filaments with high porosity and a high water retention capacity.
(B) In an alternative process for preparing the fibers of this inven-tion and which forms part of the present invention water is added to a con-ventional dry-spinning solution in an amount of from 2 to 25% by weight, based on the total mixture. rn this case the mixture, before it is spun, is heated to at least a temperature at which a clear solution results. The solution is then spun at a te~perature which is above the gel polnt of said solution into a spinning tube. In this spinnlng process: where the ratio of polymer:
water i5 less than 4:1 the temperatures of the spinning tube and the air therein are preferably no higher than the temperaturq of the spinning solu-tion. ~fiere the ratio of polymer:water is ~:1 or more it is a~vantageous that the temperature of the spinning tube and the spinning air be above the _ 5 _ ~`" ,`
~, temperature of the spinning solu-tion~
~ lus, accordin~ to a feature of the present invention there is provided a process for the production of hyclrophîlic filaments and fibres from filament-forming synthetic polymers by spinning a solution which, in addition to a suitable solvent, also contains a substance which is essentially a non-solvent for the polymer and which is readily miscible with the spinning solventJ by the technique of dry spinning, wherein from 2 to 25 % by weight of water, based on the mixture as a whole, are added to the spinning solution, the resulting mixture is heated to a temperature which a-t least corresponds to the temperature at which a clear solution is formed, and the spinning solution thus obtained is spun at at least that temperature.
Acrylonitrile polymers containing at least 50 % by weight and preferably at least 85 % by weight of acrylonitrile units are preferably spun by this process according to the invention.
To prepare the spinning solution the spinning solvent preferably dimethyl formamide, is mixed with water and the polymer. In this connection, it has proved to be advantageous initially to mix the spinning solvent with the water and then to introduce the polymer solids into the resulting mixture with stirring. If the reverse procedure is adopted, i.e. if the polymer is initially mixed with the spinning solvent and the ~ater subsequently introduc-ed, agglomeration can occur.
~y mixing the constituents of the spinning solution in the pre-ferred manner described above, a suspension is initially obtained at around room temperature. ~his suspension is then heated to at least the temperature at which a clear solution is formed. The level of this temperature is large-; ly dependent upon the composition of the spinning solution, i.e. upon its solids content, its water content and its solvent content. The minimum necessary temperature may readily be determined in each case by a preliminary test. The spinning solution is then kept at the necessary temperature for at least one minu~e and preferably for 3 to 15 minutes in order to produce a ::

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clear solution free from so-called "jellyfish" from the suspension. I-lowever, the residence times at this temperature should not be much more than 15 minutes, particularly in cases where, due to the composition of the spinning solution, the minim~lm necessary temperature is already relatively high, for example between 130 and 150C, because o-therwise the natural colour of the solution deteriorates and yellow-coloured filaments and fibres are obtained.
After this heat treatment, the spinning solution is preferably filtered and immediately delivered to the spinneret.
If, once a clear solution has been obtained, this solution is allowed to cool again, it gels at a certain temperature and, as a result, can no longer be sp~m. Accordingly, it is important to ensure that, once it has been produced, the clear solution does not fall below the temperature at which it gels. This gelation temperature is below the above-mentioned minimum tem-perature at which a clear solution is obtained. At low solution temperatures, for example below 100C, the temperature difference between the gel point of the solution and the solution temperature is initially greater than at relatively high solution temperatures, for;example above 130C (see Table 1).
As already mentioned, the minimum necessary temperature for obtaining a clear solution is dependent upon the composition of the original suspension. Thus, for a composition of, for example~ 20 % by weight of acrylonitrile polymer, 5 % by weight of water and 75 % by weight of spinning solvent, a minimum temperature of around 80C is necessary for obtaining a spinnable solution. If the water content is increased to 20 % for the same polymer solids content of 20 %, a clear solution is formed at around 130~C.
The quantity of water which may be used decreases ~ith increasing polymer solids. For example, it is still possible in accordance with this aspect of the invention to sp m a spinning solution of 45 % by weight of acrylonitrile polymer solids with 2 to 6 % by welght of water and 49 to 53 % by weight of spinning solvent. In this case, the spinning solution has a temperature of at ,east ~20C, preerably from 130 to 150C~ and gels at temperatures below ' . . . .
. : . . , about 100C. On the other hand, the solids concentration of the spinning , solution mayJ of course, also be reduced to below 20 % by weight by increasing the water content accordingly.
In this process according to the invention, the concentrations of polymer solids in the spinning solution are of the order of about 20 to 30 %
by weight, depending upon the K-value of the polymer which is preferably in the range of from 80 to 95.
The higher the solids con~ent of the spinning solution, the smaller the amount of water added and the greater the i~r~s~-~ t~e viscosity of the spinning solution. With a solids concentration of 45 % by weight in the spinning solution, it is no longer possible to increase the water content to beyond 6 % by weight because ~ith a water content of 10 % by weight, for example, it is only possible to obtain a thick paste, On the other hand, the filaments produced from these spinning solutions no longer show adequate hydrophilic properties when the spinning solution has very low water contents of, for example, below 2 % by weight, so that the upper llmit to the polymer solids content to the spinning solution preferably amounts to aro~md 45 % by weight. Conversely, the solids content of the spinning solution should pre-ferably also not fall to dis~ n~ below about 20 % by weight if the spin- -ning solution is to solidify adequately in the spinning duct.
~ithin the above-mentioned limits, however, the composition of -` ~ the spinning solution may be varied as required.
The spinning solution is spun by a standard dry spînning process.
The spinning conditions, i.e. in particular the duct temperature and air temperature, are adapted ~o the composition of the spinning solution and to the required hydrophilic properties of the spun filaments and fibres.
In thqs process according to the invention, the duct temperature and air temperature are adjusted with particular preference in such a way that they are lower than or at most equal to the temperature of the spinning solution.

~ ., 6~7 The duct and air temperatures required Eor this process according to the invention are variable within wide limits. They may be adjusted to between room temperature and about 220C, depending upon the ~omposition of the spinning solution where dimethyl formamide is used as the solvent. In general, the duct and air temperatures are governed by the gel point o the spinning solution. The lower the gel point of the spinning solution, the lower the duct and air temperatures selected may be. If the duct and air tem-peratures are higher than the temperature of the spinning solution, it is still possible in individual cases to produce fibres with hydrophilic properties, although in their case the degree of hydrophilicity is lower. The more the duct and air temperatures differ from the temperature of the spinning solution in the upward direction, the greater the incidence of d;sturbances during spinning in the form of breakages caused by suddenly evaporating water. This is particularly the case when the temperature of the spinning solution is below 100C and the duct and air temperatures are considerably above 100C.
In selecting the duct and air temperatures, it is always import~
ant to ensure that the spinning solution gels or solidifies in the spinning duct. In the case of the above-mentioned spinning solution of 20 % by weight of acrylonitrile polymer9 5 % by weigh* of water and 75 % by weight of spin-ning solvent, excellent spinning can be obtained at duct and air temperatures of~ for example, 40 C for a temperature of the spinning solution of 80C. If the spinning solution consists, for example, o 20 % by weight of polymer solids, 20 % by weight of water and 60 % by weight of dimethyl formamide, duct and air temperature of around 100C, preferably from 20 to 50C, is eminently suitable for a temperature of ~he spinning solution of 130C.
Accordingly, in order to obtain adequate hydrophilic properties, it is preferred that the temperatures of the duct and the air in the spinning duct are below the temperature of the spinning solution.
In a few special cases, for example where the spinning solution has a low water content and a relatively low polymer solids content9 it can ~: ~ - - , : - -~L~$~ 67 happen that a solution of the type in question does not gel, even at room temperature, as is the case for example with a solution of 2.5 ~ by weight of water, 20 % by weight of acrylonitrile polymer and 77.5 % of dimethyl form- -amide. A solution such as this can only be spun, i.e. solidified in the spinning duct, by applying high duct and air temperatures, in the present case for example 150C. ~lowever, due to the simultaneous evaporation of water and spinning solvent in the duct, the filaments produced in a case such as this do not show good hydrophilic properties.
The filaments obtained by the process according to the invention are aftertreated in the usual way, i.e. washed and drawn, or vice versa~
finished, dried and, optionally, crimped and cut into staple fibres.
Microporous filaments and fibres with a core-jacket structure and a water retention capacity of 10 % and more are obtained by this process according to the invention.
In a second alternative process forming part of this invention for production of the fibers and filaments according to the invention, a con-ventional spinning solution is dry-spun and the filaments are contacted with steam or the vapor of another liquid capable of solidifying or coagulating the filaments immediately ater the spinning solution has left the spinning orifice but before solidification or coagulation of the filaments is completed.
The filaments are then washed with a liquid miscible with the spinning solvent, preferably water, to remove residual spinning solvent under conditions similar to those described in the first process.
Thus according to a feature of this invention there is provided a method for producing hydrophilic or hygroscopic filaments and fibres, from filament-forming synthetic polymers, by spinning a polymer solution by a dry-spinning process, characteri~ed in that as soon as they emerge from the spinneret, but at the latest before solidification of the filament is com-pleted, the filaments are brought into contact with water vapour or with the vapour of some other liquid which coagulates the said filaments.

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In the method according to the invention, polymers which are not normally hydrophilic, preferably acrylonitrile polymers, are spun, special preference being given to those containing~ at least 50 % by weight, more particularly at least 85 % by weight, of acrylonitrile units.
The method according to the invention may also be used Eor pro-ducing bicomponent or modacryl fibres, fibres made from homopolymers7 spin-dyed fibres, or also fibres from polymer blends, e.g. from mixtures of acrylonitrile polymers and polycarbonates. According to the invention, it is also possible to use linear, aromatic polyamides, such as the polyamide from m-phenyldiamine and isophthalic acid, or those which may possibly have hetero-cyclic ring systems, for example benzimidazoles, oxazoles, or thiazoles, and which can be produced by dry-spinning from a spinning solution containing a solvent which is evaporated out.
Other suitable compounds are polymers having melting points of over 300C which, as a rule, can no longer be spun from the melt and which are produced by a solvent-spinning me~hod, e.g. by dry-spinning.
This spinning process, in principle, is a conventional dry-spinning process, preferably using strongly polar organic solvents such as dimethyl formamide (DMF), dimethylacetamide or dimethyl sulfoxide. However, it is also possible to spin a solution of polymer, solvent and non-solvent e.g. water, polyvalent alcohols and glycols which can be mixed with the spin-ning solvent, as described above, according to this method.
Besides steam, vapors of liquids or substances which are non-solvents for the polymer used are suitable in the foregoing process. In the case of acrylonitrile these are, e.g., mono- or polysubstituted alkyl esters or ethers or polyvalent alcohols, such as diethylene glycol, triethylene glycol, tripropylene glycol, triethylene glycol diacetate, tetraethylene gly-col and glyc:ol ether acetates. Further suitable substances are alcohols like 2-ethyl cyclohexanol, glycerin, esters or ketones or mixtures thereof, for example, mixtures of ethylene glycol acetates. Besides water, those sub-stances which are easily vaporized and which have a low flammability, such as methylene chloride or carbon tetrachloride, are preferred.
Depending on the point at which steam or other suitable vapor is blo~ into the spinning tube and on the intensity and depending on the thermal conditions in the spinning tube it is possible to influence the cross-section, the width of the sheath and the hydrophilicity of the filaments. It has been found that core-shell filaments of a circular cross-section and a thin sheath of at most 25% of the total cross-sectional surface area and an extremely high water-retention capacity of about 60% and more is obtained if the spinning is conducted with low temperatures of the spinning tube of at most 140~C, preferably of from 20 to 120C. (5ee Table 1, Nos. 1 to 3).
If the spinning tube temperatures are higher, preferably above 160C, sheath/core structured filaments are obtained having an oval to trilobal shaped cross-section and having water retention capacities of from 20 to 60 % and the sheath comprises up to about 60 % o-f the total cross-sectional surface area.
; The width of the sheath can also be controlled by varying the ratio of air to vapour e.g. steam. Thus large amounts-of vapour and relative-ly small amounts of air tend to produce filaments with a large sheath width, which may amount to as much as 75 to 8a % of the total cross-sectional area of the fiber. (See Table 1, No. 211, C~n~ersely, if t~e amolmt of vapour ; e.g. steam i5 small in relation to air used, sheath!core ilaments are obtain-ed having only a small sheath and a low water retention capacity, and approach the form of the fil~ment usually obtained by a dry spinning process. ~See Table 1, Nos. 5 and 61.
The cross-sectional structure of the core-sheath filaments was ; determined b~ means of the electron microscope. In order to determine the core and sheath area of the filaments, so~e 100 fiber cross sections were evaluated, by quantitative analysis with a Leitz "Classimat" photo-analyzer.
In the rnethod according to the invention, the vapour is prefer-~ .
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ably injected above the spinneret in the direction of the flow o air and of the removal of the f;lament. It is also possible, however, to inject the vapour at right angles to the filament and below the spinneret) as long as no strong turbulence is caused thereby.
In order to avoid undue condensation of water vapour and solvent mixtures within the spinning tube it has been found that the optimum tempera-ture in the spinning tube should be more than 100C, preferably between 105 to 140C, and that the length of the spinning tube/be as short as possible, for example, about 1 meter. As already indicated, the width of the shell surface and the porosity may be governed by the intensity of the vapour in-jection, i.e. this makes it easy to establish the kind of matt finish and dyeing ability of the spun filaments required for subsequent use.
In principle, the non-solvent vapours, preferably water vapour or saturated vapour~ may be allowed to act as long as the filament material is not completely solidified.
The method according to the invention may therefore also be applied with advantage by allowing the vapour to act through a nozzle or tube as soon as the group of filaments has left the spinning tube. This also 7~; /q f ~ e n J~s produces hydrophilic, porous core-sheath ~b~r~.
With the method according to the invention, it is preferable to inject mixtures of vapour and air into the spinning tube, since these may be controlled by the temperature in such a manner as to ensure that there is no appreciable condensation in the said spinning tube. Spinning in a pure vapour atmosphere produces filaments with an extremely matt finish, whereas highly hydrophilic, lustrous surfaces can also be produced with mixtures of vapour and air. However, it is impossible to achieve the purposes of the invention with superheated steam.
The amounts of vapour and air required are naturally governed by the dimensions of the tube and by the relevant method parameters such as 3n spinning velocity, spinning temperature, tube temperature, solvent concentra-. .

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tionJ etc., and b~ the desired filament properties. 'S'hese conditions can be matched with each other in indlvidual cases ~y suita~le preliminary tests.
T~e following results were o~taIned with a spinning tube 600 cm in length and 30 cm in diameter.
I`f the volume of air is reduced, during spinning, below a criti-cal value, the volume o gas present at low amounts of vapour is so small that it is no longer possible to spin the polymer solution. The lower limit at which spinning can be carried out is about 2 cm3 of air per hour per kg of material spun and a minimum vapour volume of 1 kg per hour per kg of spun material ~See Table 1, No. 22~.
The minimum volume of injected water vapour required to produce ; core-sheath fibres that are still hydrophilic is about 1 kg per kg of material spun at a tube temperature of 20C, when using a normal polyacrylonitrile spinning solution at a concentration of 30%.
~owever, if use is made of a mixture of polymer, spinning solvent, and non-solvent, the volume of vapour required is only 0.1 kg per kg of material spun, and this increases quite considerably the water-retention abil-ity of such core sheath fibres Csee Example III, b and c~.
If higher tube temperatures are used, especially above 160C, a larger volume of vapour is required, preferably about 10 kg of vapour per hour per kg of material spun.
If the vapour is initially applied to the filaments externally of the spinning tube, for example through a nozzle, 5 k~ of vapour per hour per kg of material spun are usually enough to produce hydrophilic porous core-sheath filaments.
In order to obta~n the minimum porosity of at least 10%, the non-solvent (~n the process described first process ~A~ ~s added to the spinning solution in an amount of at least la% based on the polymer solids, care being taken of the non-solvent i5 not sign~ficantly evaporated in the spinning tube and that the filaments are treated under mild thermal conditions so that ~ - 14 -6~7 the voids will not collapse when producing the fibers. The water retention capacity is at least 10% if the porosity is at least 10%.
The selection of the polymers is such that the swellability does not exceed 10%. ~is ensures that the water retention capacity is not pri-marily due to the chemical constitution of the polymer but to the porous structure of the fiber prepared from the polymer.
As previously indicated, fibers and filaments according to the present invention preferably have an average void diameter of at most 10,000 A. The size of the pores can be influenced by the spinning and after-treatment conditions. In the first described process involving the addition of a non-solvent an average void size of about 4,000 A is obtained when high-boiling non-solvents like glycerin or tetraethylene glycol are added and the temperature of the spinning tube is about 180C and the spinning air has a temperature of about 350C.
Smaller pores can be obtained when both temperatures are decreas-ed. Hence, an average pore-diameter of about 2,000 A can be achieved if the said temperatures are below the boiling point of the spinning solvent used.
B~ the processes described above fibers are produced having pores in the core which are connected to each other like a canal system. ~t the same time a sheath structure is produced which is capable of penetration by water which is then picked up by the core.
Besides the methods described above the width of the sheath can be influenced by the ratio of polymer solids to amount of non-solvent. The higher the ratio of polymer solids to non-solvent the larger the width of the sheath will be. Thus, a desired width of the sheath can easily be achieved by simple tests.
As ~rt is well-known, synthetic fibers or yarns or textile articles thereof have a wet feeling after being contacted or contaminated with a low amount of water. For example, a commercial acrylonitrile fiber feels wet after moistening with 5% or more water. On the other hand, the fibers and .. : , :

filaments according to a preferred feature oE the present invention are pro-duced so that they exhibit a higher wet-feel limit of at least 6%. It is obvious that this minimum value depends On the chemical composition of the spun polymer. When an acrylonitrile polymer has been spun according to this embodiment of the invention the wet-feel limit is found to be about 10% or more.
The wet-feel limit can be influenced by ~he porosity which itself is governed as described above. If, for example, the water retention capacity is more than 12% then the wet-feel limit is increased to more than 10%. If the water retention capacity is increased to more than 20%J then the wet-feel limit increases to more than 15%~ These figures are particularly related to fibers of acrylonitrile polymers.
It is important to comfort that the perspiration caused by sudden activity of the wearer be rapidly picked up by the pores of the fibers of the textile. Hence, according to a preferred embodiment of this invention a suf-ficient pick-up is achieved if the pore-volume of the fibers fills within 5 minutes to at least 20%, preferably to at least 30%. Accordingly, these pre-ferred fibers and filaments are very suitable for the production of clothes giving an outstanding wearing comfort to the wearer.
~ith respect to the wearing comfort it is of further importance that the fibers in a yarn can rapidly carry away the humidity. For this pur-pose textiles prepared from fibers of circular cross-sections are especially suitable. Round cross-sections can be produced as already described above.
If the activity of the human body is low, such as in the case of light work, only llttle humidity in liquid form results. In those cases it iS advantageous if the textile also absorbs water vapor and thereby causes a dry atmosphere near the skin of the wearer.
It has been found in wear tests and ergometer tests that the degree of humldity a~sorption in one def1nite point of the sorption-isothermal line is not as important as the differences of the water absorption capaci~y '' ~ ' ' ' : " , . .
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at different relative humidities. For example, the water absorption capacity at say 65% r.h. is not as significant as the cornparison of water absorption capacity at 65% and 95% relative humidity, respectively. Pre~erably, this difference should be more than 2% to result in wearing comfort. More prefer-ably, the difference should be at least 5%.
According to another preferred feature of the invention the fibers and filaments exhibit outstanding behaviour under the criteria describ-ed above because they have a water absorption and desorption capacity of more than 1%, if they are intermittently exposed to 65% r.h. and 95% r.h., respec-tively, at 20C, the humidity being changed every 20 minutes. Such a rapid pick-up of humidity is especially useful when the activity oE the human body rapidly changes.
The degree of the water absorption is particularly influenced by the size of the pores and/or by additives to the fibers. This water absorp-tion capacity can be increased by the generation of small and medium voids having an average diameter of at most 1,000 A and can also be increased by the copolymerization of hydrophilic comonomers or addition of hydrophilic addi-- tives. Such additives can be incorporated during the manufacture of the fibers or during an after-treatment step.
A difference in the water absorption capacity ~FA value) of more than 3% is obtained if the portion of the pore-volume of the pores having a pore-diameter of less than 500 A is at least 30 mm3/g of the fibers.
The void stlucture of the fibers and filaments according to this invention is also advantageous for the drying of the fibers because this structure promotes a rapid vaporization of the humidity as well. Thus,a heat-trap is prevented if the activity of the body is high.
The fibers and filaments according to this invention possess, by virtue of their porous sheath/core structure, a high capacity to imbibe water, without essential swelling, high humidi~y transport velocity, a high wet-eel limit and a high water absorption capacity. Furthermore, they have .~ .

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a low density which results from porous structure.
Through the cumulation of these advantageous and desirable pro-perties in a single fiber, the fiber is highly suitable for conversion to textile articles~ particularly clotlles, which give a very good wearing-comfort.
The physical parameters mentioned in the above description have been determined as follows. These methods relate to dyed or blind-dye fibers, respectively, which have been deliberated from preparation and to yarns or textile articles made thereof.
Measurements (methods) ~ . . .
Mercur~ density (g Hg) After a sample has been heated at 50C under vacuum (10 2 mbar) the mercury density (average apparent density) is determined by volume measure-ments in mercury at a super atmospheric pressure of lO bar.
Helium de-nsitY ~ Hel After heating the sample at 50C under vacuum (10 2 mbar) the helium density ("true density") is determined by volume measurement in a helium atmosphere in a gas comparison pyknometer.
Definition of the porosity ~P) P ~ [l - ~g Hg/~ He)] . 100%
Flotation density ~g F) Several dry sk~ins of fibers were weighted exactly ~with an exactness of 0.1 mg) ~ml) and submerged in water ~density ~ H20). After 5 minutes the weight of the skeins in water of 20C is determined ~m2), the flotation density ~after 5 minutes) yield to F = 1 ~ 2 m - m Definition of the sheath/core structure Samples which have been prepared by usual techniques ~freeze-break, ion-etching and gold vapor deposition) exhibit a sheath/core structure ~ : ' 3G~

in a stereo scan electron microscope whicll is characteri~ed in that the voids recognizable in the core on the average are evidently larger -than the voids in the sheath. Particularly the sheath can appear compact, i.e., has essen-tially no voids with a diameter of more than 300 A. The thickness or width of the sheath is determined as the distance between the outer surface and that point where the just described difference in structure is observed (when perpendicularly going from the outside to the middle of the fiber).
Water retention capacity (WR) The water retention capacity is determined in analogy to DIN
53814 ~as described in Melliand Textilberichte 4, 1973, page 350). The fiber samples are submerged in water for 2 hours. The water contains 0.1% wetting agent. Thereafter the fibers are centrifuged with an acceleration of 10~000 m/sec2 for 10 minutes and the amount of water retained in the fibers is gravimetrically determined. To determine the dry weight of the fibers they are dried at 105~C until the humidity is constant. The water retention capa-city in percent by weight is mf . - . mt WR mtr 100 mf = weight of the wet fibers mtr = weight of the dry fibers Average pore diameter ~d) The average pore diameter d is determined from the porosity P
and the inner surface 0 according to the l-point-BET-method with nitrogen starting pressure~ gauge; sorption temperature: liquid nitrogen boiling point) d p m2/g 1 g/cm3 _ = 4 . 10 3 2 nm 100%-P o (~le/g/cm ) Furthe-r electron-microscopic pictures of contrasting thin-cuts and stereo-scan electronic microscope pictures of break-surfaces have been evaluated for the determination of the pore structure. The values determined - - ' ,- , . ' . ' ' ' ' ' ' " ', ' optically normally are greater than the value d.
Wet-feel limit (~'FG~
A series of samples of the same kind were moistened evenly with water and then diE:Eerently hurled off and weighed. At least 5 test persons had then to determine which fibers already felt wet. If the majority of the test people testified so, the wet--Eeel limit was passed over. As a control, the fibers were again weighed and the water content was determined by drying.
The wet-feel limit is the minimum water content which just induces a wet feel.
Moisture absorption capacity ~FA) After drying at 50C/0.1 Torr under nitrogen up to weight con-stancy the dry weight of a sample i5 determined on a vacuum balance (exactness Q.2 mg). ~hile intermittently blowing in and sucking off water vapor (20C) a water vapor pressure is adjusted which corresponds to 65% relative humidity.
~hen the samples had a constant weight ~he weight gain ~as determined:

FA _ f tr 100%
mtr mf = weight of the wet fiber mtr = weight of the dry fiber - Thereafter analogous measurements were made at hlgher relative humidities.
Degree of pore-fill with water (F) The pore-fill is determined by comparison of the mercury density ~H with the flotation density gF in water after 5 minutes submerging wherein the flotation density i5 determined gravimetrically.

F = 1- He~PF) (PH /~H ) - 1 ~FA value The QFA-value is calculated as the difference between moisture absorption at 95% r.h. and 65% r.h. each measured in the equilibrium state as described above.
- 2a-; ~...~
.. . -Kinetic ~FA-value The k;netic AFA-value is determined by measuring the rnoisture absoIption and desorption at 20C, periodically changing ~he relative humid-ity to 65% and 95% every 20 minutes.
Polymer swelling ~Q) The moisture absorption of non-porous polymer (fibers) is deter-mined from 0 up to 95% r.h. and is extrapolated to 100% (FA 100). The in-crease in weight corresponds to the polymer swelling Q (%) = FAloo 3He/l g/cm Q of copolymers with hydrophilic comonomers can be different from the ~rue swelling. Nevertheless Q is used for characterizing the swellability.
Permeability'of_the sheath for water The water retention capacity is determined with the following modifications: the dry filaments were submerged in water in the form of a U
without the ends being in the water. In this way the water pick-up occurs only through the sheath. Thereafter it proceeded as described under "water retention capacity". The sheath is permeable or penetratable if after a moistening in 5 minutes the water retention capacity is at leas-t 20% of -the ~riginal water retention capacity WR.

~ 20 '-Determination of the'continuous character of the canal ~ore system ::
For this purpose the porous sheath/core fibers are prepared as follows: in several baths the water within the pores of the fibers is ex-c~anged against an intermedium and this intermedium is substituted in a follow-ing concentration series by the real compound to be embedded, an epoxy resin.
The water pick-up, the dehydrogenation and embedding of the resin is conduc-,' ted under vacuum to avoid occIusion of gas and to so achieve an optimized fill ~' of the voids. The fibers containing the resin are then cut in a cryomicrotom at a temperature of -100C and the thin-cuts are contrasted.
In the transmission-electron microscope pic~ures the resin in the pores and surrounding the fibers appears darker than the fiber matrix and ~ .

characterizes the permeability of the pore sys-tem for liquids of the core and the sheath as well. In the attached figures Figure 1 shows the dependency of the moisture absorption in percent by weight of a fiber according to the invention (prepared according to Example IV, curve a) on the relative humidity in percent compared with a commercially available acrylic fiber (curve b).
Figure 2 shows the same fibers as in Figure 1 with respect to their kinetic sorption o-f water vapor when periodically changing the relative humidity (65% and 95% r.h.~ at 2QC (kinetic aFA value~.
EXA~PLES
Example I
19.9 kg of DMF were mixed while stirring with 4.8 kg of glycerol in a vessel. Thereafter 5.1 kg of an acrylonitrile copolymer of 93.6% of acrylonitrile, 5.7% of methyl acrylate and 0.7% of sodium methallyl sulphon-ate were added while stirring. The resulting mixture was stirred for 1 hour at 80C, filtered and the completed spinning solution dry spun from a 180 bore spinneret in a spinning duct by methods known in the art.
; The duct temperature was 160C. The viscosity of the spinning solution, which had a solids concentration of 17% and a glycerol content of 15.7% b~ weight, based en D~F ~ polymer powd0r, amounted to 85 ball drop seconds. For determining viscosity by the ball drop method, see K. Jost, Rheologica Acta, ~ol. 1, No 2-3 (1~58~, page 303. The spun material with a denier of 1700 d*ex was collected on ~ebbins and then doubled into a sliver ~ith an overall denier of 102,0aQ dtex. Ater lea~ing the spinning duct, the sliver s*ill contained 1~.1% by weight of glycerol.
The glycerol content of the sliver was determined by gas chromato-graphic analysis. The tow was then drawn in a ratio of 1:3.6 in boiling - water, washed for 3 minutes under slight tension in boiling water containing an antistatic preparation. This was followed by drying in a screen drum dryer at a maximum temperature ef 130C with a permitted shrinkage of 20%
after which the tow was cut into fibers with a staple length of 60 mm.

. .
- 22 ~

:~

i7 After leaving the duct the fibers sllowed a marked sheath/core structure in a stress-scan electron microscope (magnification 780-3800) and irregular, mostly trilobal cross-sections.
The individual fibers with a final denier of 3.3 dtex had a helium density of 1.17 g/cm3, a mercury density of 0.862 g/cm3. and a water retention capacity of 32.8%. The porosity was 26.4%, the inner surface was 9.7 m2/g and the average pore diameter was 106 nm.
The jacket surface had a width of approximately 4 ~m. In order to determine the core and jacket area of the fibers, more than 100 fibers cross-sections were evaluated by quantitative analysis with a Leitz "Classimat"
image analyzer. On average 32% of the cross-sectional area was occupied by the width of the jacket. The wet-feel limit was about 24%, and the pore-fill in water after 5 minutes was 71%. The moisture absorption at 95% r.h. and 20C was 12%, the ~FA value was 6.8% and the kinetic ~FA value was 2.0%. The fibers can be dyed deeply throughout with a blue dye corresponding to the formula C~13 C~1~3 C2H5 - NH - ~ C

OH
_ _ 2 The extinction ~alue amounted to 1.39 for 100 mg of fiber per 100 ml of DMF
C570 m~, 1 cm cuvette).
Yarns with a count of 3611 were spun from the fibers with a final denier of 3.3 dtex, and made up into pieces of knitting. The pieces, ; some of which were left white and others dyed blue, were found to ha~e a ~ater retention capacity of 3~.3%.
Example II
10.4 kg of DMF were mixed while stirring with 2.15 kg glycerol in a vessel. Thereafter 2.85 kg of an acrylonitrile copolymer of 90% acrylo-,, . -nitrile, 5% of acryl~mide and 5% of N-methoxymethylacrylamide were added while stirring. The resulting mixture was stirred for one hour, filtered, and the ^ - 23 -- - , - , -, .

completed spinning solution spun as described in Example I, The viscosity of the spinning solution which had a solids content of 15% by weight and a glycerol content of 14.5% based on DMF and polymer solids was 69 ball drop seconds. The spun material of a denier of 1700 dtex was again doubled into a sliver an~ then treated as described in Example I.
The fibers again had an irregular cross-section generally tri-lobal shaped and a marked sheath/core structure.
~- The individual fibers with a final denier of 3.2 dtex were deter-mined to have the ~ollowing physical properties:
heli~ density 1.19 g/cm3 mercury density 0.857 g/cm3 porosity 28.0%
water retention capacity34.9%
inner surface 7.6 m2/g average pore diameter 145 nm sheath surface 35%
wet_feel limit 25%
- pore-fill (after 5 min.) 64%
moisture absorption (95% r.h.~ 11%
~FA value 5O7%
kinetic ~FA value 1.5%
Example III
60 kg DMF were mixed with 17.5 kg of glycerol in a vessel while stirring. Thereafter 22.5 kg of the copolymer of Example I were a~ded while stirring and stirring was continued :~or one hour at 80C. Then~ after filter-ing the solution was conventionally dry spun through a 496-bore spinneret.
. ~
The temperature of the spinning duct was 180C, the viscosity of the solution having a solids content of 22.5% and a glycerol content of 17.5%
was 85 ball drop seconds.
The spun material wi~h a denier of 6850 dtex was collected and 2~ _ .

doubled into a tow. The tow was then stretched in a ratio of 1:3.6 in boiling water, then washed in boiling water for 3 minutes under slight tension and finished with an antistatic preparation. This was ~ollowed by drying in a screen drum dryer at a temperature of 100C with a permitted shrinkage of 10%
after which the tow was cut into fibers with astaple length of 60 mm.
The individual fibers with a final denier of 1.9 dtex were deter-mined to have the following properties:
helium density 1.18 g/cm3 mercury density 0.918 g/cm porosity 18.8%
water retention capacity 25%
inner surface 3.9 m2/g average diameter 170 nm - sheath surface 21%
wet-feel limit 19%
pore-fill (20 minutes) 78%
moisture absorption ~95% r.h.) 4.9%
- ~FA ~alue 3.1%
kinetic ~FA value 1.2%
The fibers had a tensile strength of 2.3 p/dtex and an elonga-tion at break of 46%. The relative loop tensile strength was 61% and the relative loop elongation at brea~ 30%. The fibers were then made up to yarns ; of Nm 36/l from which textile articles li~e T-shirts and socks were manu-factured. These articles had excellent wearing comfort properties. The above ~ values of the physical properties were reproduced when measuring the textile ; articles.
Knitting fabrics of the same construction were made from 1) wool, 2) cotton, 3) commercially available acrylic fibers, and 4) fibers according to this Example and the climbup speed was measured according to DIN 53924. After 9 minutes the values were determined as follows:

: :

Ei6~7 0 cm 2) 11 cm 3) 3.5 cm 4~ 9 cm The same fabrics then were subjected to drying tests. All having the same starting moisture of 150 g water/m2 the following drying times were found:
1~ and 2) more than 120 minutes 3) 60 minutes 4) 65 minutes The residual moisture was 5% in each case.
Example IV
52 kg of D~F were mixed with 12 kg of tetraethylene glycol in a vessel while stirring. Then 36 kg of the copolymer of Example I were added while stirring at room temperature. Thereafter the suspension was heated to 135C, filtered and spun. The period from heating to spinning was S minutes.
The spinning solution was spun through a 72 bore spinneret in a spinning duct of 30C, the spinning air temperature was 40C. The amount of spinning air was 40 m3 per hour. The spun material was collected on bobbins and then doubled into a tow of a total denier of 1,708,000 dtex. This tow was then stretched in boiling water in a ratio of 1:4.0, washed, provided with antistatic preparation and dried while being permitted a shrinkage of 20%.
The tow was crimped and cut to fibers of 100 mm length. The individual fibers had a final denier of 11 dtex and had a marked sheath/core structure.
The following physical properties were found:
; helium density 1~9 g/cm mercury density 0.834 g/cm3 porosity 3Q.8%
water retention capacity 38%
inner sur~`ace 56.2 m /g average pore-diameter 25 nm .

, .
,,, :

:

sheath surface 5%
yore-fill (after 5 minutes) 40%
moisture absorption (95% r.h.) 12.3% (see Pigure 1) ~FA value 10.8% (see Figure 1) kine~ic ~FA value 1.9% (see Figure 2) permeabili~y of sheath =
~YR after S minutes 15%
Example V
The polymer of Example I having a K-value of 81 was dissolved in DMF at 80C. The filtered spinning solution which had a final concentration of about 30% by weight of polymer was dry-spun through a 180 bore spinneret.
From above the splnneret 25 kg of saturated steam per hour and 10 m3 air of 150C per hour were blown into the spinning duct which had a length of 600 cm and an internal diameter of 30 cm. The temperature of the duct was 140C

5.8 kg of steam were used per kg of spun material. The DMF content of the as-spun filaments was about 59%. The filaments of a total denier of 2400 dtex were collected on bobbins and then doubled into a tow of a denier of 684,000.
This tow was stretched in boiling water at a ratio of 1:4.0, washed, provided ~ with antistatic preparation, ~ed at 120C while permitting a 20% shrinkage crimped and cut into fibers of a staple length of 60 mm.
l~e individual fibers of a final denier of 3.3 dtex showed the following physical properties:
helium density 1.19 g/cm3 ; mercury density 0.615 g/cm3 porosity 48.3%
water retention capacity 63%
nner surface 19.2 m2/g average pore dlameter 46 nm sheath area 45%
wet-feel limit 38%
"': ' : ~ ', : ' .: . ', ', ' . -' . ' ~ . ~ .

pore-fill (5 minutes) 33%
moisture absorption (95% r.h.)8.3%
~FA value 6.9%
kinetic QFA value 1.7%
permeability of sheath =
WR after 5 minutes 26%
Example VI
The polymer of Example V was dissolved as described in Example V
and spun The amount of steam was 2.8 kg per kg of spun material, the air was 10 m /hour at a temperature of 150C. The duct temperature was 160C.
The filaments were further treated as in Example V. The final denier was 3.3 dtex and the cross-section was dumb-bell shaped.
Physical properties:
sheath area 70%
water retention 12%
fiber density 1.05 g/cm3 porosity 11.8%
inner surface 1.9 m2/g average pore diameter 199 nm wet-feel limit 7%
Example VII
An acrylonitrile copolymer consisting of 93.5% of acrylonitrile~
5.7% of acrylic-acid methyl ester, and 0.7% of sodium methallylsulphonate, ~; ~; with a K value of 81, was dissolved in dimethyl formamide (DMF) at 80C. The filtered spinning solution~ with a final concentration of about 30%, was spun dr~ from a 180-nozzle~spinneret. 25 kg/hr of saturated vapour and 10 cbm/hour of air at 150C were injected into the spinning tube (600 cm in length, 30 cm in diameter), above the nozzle. The tube temperature was 140C. About 5.8 kg of vapour per kg of material spun were used. The DMF content of the ilaments was 59% of the polymer solid. T~e filaments~ with a total titer -of 2400~dtex were collected on bobbins and combined ~o form a 684'00 dtex cable. The fiber cable was then stretched in a 1:4.0 ratio in boiling water, it was washed, and antistatic preparation was applied it was dried at 120C
leaving a 20% contraction, it was crimped, and it was then cut into staple fibers 60 mm in length. The individual fibers had a final titer of 3.3 dtex and a water-retention ability of 63% according to German Industrial Standard 53814. The fibers had a pronounced core-sheath structure and an oval cross-section. The flat portion of the sheath amounted to about 45% of the total cross-sectional area.
Table I which follows, shows additional examples. As described in 10 Example 1, the spinning solutions were spun into core sheath fibers having a final titer of 3.3 dtex and were then after-treated. The volumes of vapour and air, and the temperature of the air and the tube, were varied during the spinning process. The solid used was the polymer described above.

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As may be gathered from the Table, there are distinct relationships between the cross-sectional shape~ the width of the sheath, the water-retention ability and the appearance of the porous core-sheath fibres.
Matt fibers, highly hydrophilic, usually ]laving circular cross-sections and a thin sheath area less than 30% of the total cross-sectional area, are obtained with tube temperatures of less than 140C, preEerably be-tween 20 and 120C (Nos. 1 to 3). As tube temperatures increase, the water-retention ability drops off sharply and the filaments become lustrous. At about 160C they change to the dumb-bell shape (Nos. 4 to 6).
Matt filamentsJ mostly of round cross-section but having wider sheaths, from about 40% of the total cross-sectional area, result from less air, lower air temperatures (Nos. 12 and 7), more vapour - from about 5 kg of vapour per kg of material spun (Nos. 19 to 21), and when spinning is carried out in an atmosphere of pure vapour (No. 11).
Lustrous fibers, having water-retention values in excess of 10%, are obtained preferably at tube temperatures above 120C (Nos. 4 and 5), at air temperatures above 100C (Nos. 8 to 10), at more than 5 cbm of air per hour, preferably above lO cbm ~Nos. 13 and-14), and at less than 5 kg of vapour per kg of material spun (Nos. 17 and l~).
As shown by Examples 15 and 16 in Table I, with less than 1 kg of vapour per kg of material spun, the fibers are no longer sufficiently hydro-philic, and they possess the dumb-bell shape typical of the dry-spinning process.
Example VIII
64 kg of dimethyl formamide were mixed with 4 kg of water in a vessel at room temperature. 32 kg of an acrylonitrile copolymer, of the chemical composition given in Example VII, were then stirred in. The sus-pension, with a solid-polymer content of 32% by weight, was fed by a gear-pump to a heating device and was heated to 130C, the period of residence in the said heating device being 3 minutes~ The spinning solution was then filtered and fed directly to a 380-nozzle spinneret. 10 kg/hour of saturated vapour and 40 cbm/hour of air at 120C were injected into the spinning tube above the spinneret. The temperature of the tube was 140C. About l.75 kg of vapour were used per kg of material spun. The DMF content of the filaments was 51% of the polymer solid~ The filaments~ having an overall titer of 3800 dtex, were collected on bobbins, combined into a 478'000 dtex cable and pro-cessed, as described in ~xample VlI, into fibers having a final titer of 3.3 dtex. The water-retention ability of the fibers was 33%. They had a pro-nounced core-sheath structure, with a bean-like to trilobal cross-sectional shape. The flat portion of the sheath amounted to 15% of the total cross-sectional area.
Example IX
a) 60 kg of DMF were mixed with 10 kg of glycerine in a vessel at room temperature. 30 kg of an acrylonitrile copolymer, of the chemical com-position given in Example VII, were then stirred in.
The suspension was dissolved as described in Example VII, filtered, and was spun from a 380-nozzle spinneret under similar vapour and air condi-- tions. About 1.9 kg of vapour were used per kg of material spun. The DMF
content of the filaments amounted to 54% of the polymer solid. The filaments, of a total titer of 3569 dtex, were again combined into a cable and were processed, as described in Example VII, into fibers having a final titer of 3.3 dtex. The fibers had a water-retention ability of 74%. They had a pro-nounced core-sheath structure of oval to bean-shaped cross-section. The flat portion of the sheath amounted to about 20% of the total cross-sectional area.
b) 0.1 kg of vapour per kg of material spun was blo~n into the tube, in the direc~ion of spinning, onto a portion of the spinning solution, after the exit from the spinneret. The filaments, having an overall titer to 3560 dtex, were processed into fibers with a final titer of 3.3 dtex, again in a similar manner. The fibers had a water-retention ability of 36%.
Example X
.
60 kg of DMF were mixed with 5 kg of tripropylene glycol in a , .
.

vessel at room temperature. 35 kg of an acrylonitrile copolymer, of the chemical composition given in Example VII, were then stirred in and, as des-cribed in Example VII, dissolved, filtered and spun dry f~om a 72-nozzle spinneret. 12 kg/hour of methylene-chloride vapour and 10 cbm/hour of air at ~0C were injected into the spinning tube above the spinneret. The temperature of the tube was 24C. About 6.2 kg of methylene-chloride vapour were consumed per kg of material spun. The DMF content of the ilaments was 76% of the polymer solid. The filaments, of an overall titer of 1620 dtex, were again collected on bobbins, combined and, as described in Example VII, processed into fibers having a final titer of 6.7 dtex. lhe fibers had a water-retention abili-ty of 102%. They had a pronounced core-sheath structure of circular cross-sectional shape. The flat portion of the sheath amounted to about 5% of the total cross-sectional area.
Example XI
; The spinning solution from an acrylonitrile copolymer of the same composition and concentration as that described in Example VII was spun dry from a 180-noæzle spinneret. 20 cbm/hour of air at 50~C were injected. The tube temperature was 120~C. The D~F content of the filaments was 41% of the polymer solid. Immediately after leaving the spinning tube, the filaments, having an overall titer of 2400 dtex, were sprayed with 60 kg of saturated vapour per hour from a nozzle, in the direction of spinning, the said nozzle being accommodated in a box having a condensate drain. About 13.9 kg of vapour per kg of material spun were consumed. The filaments were then wound, combined into a cable having an overall titer of 6~8'000 dtex, and were then processed, as described in Example VII, into fibers having a final titer of 3.3 dtex. The fibers had a water-retention ability of 34%. They had a core-sheath structure, with a bean-like to oval cross-sectional shape. The flat portlon of the sheath amounted to about 20% of the total cross-sectional area.
Example XII
a) The spinning solution of an acryloni~rile copolymer of the same :

6~

composition and concentration as that described in Example VIII was spun dry from a 380-nozzle spinneret. 10 kg/hour of saturated vapour, but no air, was injected into the spinning tllbe above the spinneret. The tube temperature was 8SC. About 1.75 kg of vapour were consumed per kg of material spun.
The DMF content of the filaments was 46% of the polymer solid. The filaments, of an overall titer of 3800 dtex, were collected on bobbins, combined into a cable, and processed, as described in Example VII, into fibers having a final titer of 3.3 dtex. The water-retention ability of the filaments was 119%.
The filaments again had a core-sheath structure and an oval to round cross-sectional shape. The 1at portion of the sheath amounted to about 30% of the total cross-sectional area. The fibers had a very matt finish.
b) A spinning solution of the same composition and concentration was spun in the same way, but instead of 10 kg/hour, 37 kg/hour of saturated vapour were injected into the tube above the spinneret. 6.5 kg of vapour were consumed for each kg of material spun. The DMF content of the filaments was 70% of the polymer solid. The filaments were processed in the same way into fibers having a final titer of 3.3 dtex. The water-retention ability of the - fibers was 131%. The fibers again had a core-sheath structure and had a very matt finish and an oval to round cross-sectional shape. The flat portion of the sheathamounted to about 50% of the total cross-sectional area.
Example XIII
5.3 kg of an acrylonitrile copolymer consisting of 93.6% of acrylo-nitrile, 5.7% of acrylic-acid methyl ester, and 0.7% of sodiu~ methallyl sulphonate were dissolved at 90C in 13.6 kg of DMF. In addition to this, 5.3 kg of a polymer mix consisting of 4.5 kg of acrylonitrile homopolymer and 0.8 kg of an acrylonitrile copolymer consisting of 91% of acrylonitrile, 5.6%
of acrylic-acid methyl ester, and 3.4% of sodium methallyl sulphonate were dissolved ln 16.3 kg of DMF at 100C. Both solutions were fed, in a 1:1 ratio, to a bifilar nozzle and were spun side by side. 10 kg/hour o~ saturated vapour and 10 cbm/hour of air at 150C were injected into the spinning tube . . . -above the nozzle. The tube temperature was 140~C. About 2.4 kg of vapour were consumed per kg of spun material. The filaments were combined into a cable, were stretched in a 1:3,6 ratio in boiling water, were washed, prepared, dried under tension at 110C, crimped, cut, and fixed for 1.5 minutes in steam. The individual titer of the fibers was 3.3 dtex and the water-retention ability was 54%. They had a pronounced core-sheath structure and a mushroom-shaped cross-section. The flat portion of the sheath amounted to about 50% of the total cross-sectional area. The fibers had about 11 crimps per cm and a crimp contraction of 10.2%. The crimp was permanent and remained almost unchanged during a water treatment up to the boiling temperature.
Example XIV
a) A portion of the spinning solution from Example XII was spun at a tube temperature of 200C, instead of 88C, under otherwise similar con-ditions and was processed into fibers having a final titer of 3.3 dtexO The fibers had a water retention ability of 24%. Again they had a core -sheath structure with a trilobal to T-shaped cross--section. The flat portion of the sheath amounted to less than 5% of the total cross-sectional area.
- b) Spinning at a tube temperature of 140C, ~mder otherwise similar conditions, produced core-sheath fibers of oval to trilobal cross-section. The flat portion of the sheath amounted ~o about 30% of the total cross-sectional area, and the water-retention ability of the fibers amounted to 49%.

~ ~.
.
~ .

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Claims (9)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A hygroscopic or hydrophilic filament or fiber of a fiber-forming synthetic polymer having a water permeable sheath and a microporous core in which both the sheath and the core contain voids, the voids in the core forming an inter-connected system open to liquids through voids in the sheath and in which the average size of the voids in the core is at most 10,000 A and is significantly larger than the size of the voids in the sheath;
a water retention capacity of at least 10%; a porosity of at least 10%; and a fiber-swellability of at most 10% which is lower than the water retention capacity.

2. The filament or fiber of claim 1 which is dry-spun.

3. The filament or fiber of claim 1 wherein the proportion of the sheath of the cross-section area is from 5 to 80%.

4. The filament or fiber of claim 1 having a wet-feel limit of at least 6%.

5. The filament or fiber of claim 1 having an equilibrium moisture pick-up of more than 5% at 95% r.h. at 20°C.

6. The filament or fiber of claim 1 having a difference in the mois-ture pick-up between 65% and 95% r.h. at 20°C of at least 2%.

7. The filament or fiber of claim 1 haying a moisture absorption or desorption, respectively, of at least 1% if the relative humidity at 20°C
is changed from 65% r.h. to 95% r.h. every 20 minutes and vice versa.

8. The filament or fiber of claim 1 comprising an acrylonitrile polymer of at least 40% of acrylonitrile units having a porosity of at least 17%, a water retention capacity of at least 20%, a mercury density of at most 1.0 g/cm and a wet-feel limit of at least 10%.

9. The filament or fiber of claim 1 having an average diameter of the voids in the core of at most 4,000 ?.