BE512778A - - Google Patents

Description

       

   <Desc / Clms Page number 1>
 



  PROCESS FOR THE MANUFACTURING OF FIBERS IN POLYMERS-ACRYLONITRILE AND
PRODUCT OBTAINED BY THIS PROCESS.



   The present invention relates to the process for spinning acrylonitrile polymers containing at least 85% acrylonitrile by weight and more particularly to the preparation of elastic threads and fibers from molten plasticized polymers,
Polyacrylonitrile and acrylonitrile copolymers in which at least 85% by weight of the polymer is acrylonitrile have been known for some time. They possess desirable physical and chemical qualities, including strength and insolubility in common solvents, such as water, methyl or ethyl alcohol, acetone, ethyl ether, ethyl acetate, hydrocarbon solvents, chlorinated hydrocarbons, etc., and are insensitive to these solvents.

   The high molecular weight polymers required for the manufacture of articles of defined shape having excellent physical qualities can be used in solutions up to 25% in concentration in spinning operations carried out dry or not. . In the case of yarn preparations, the spinning speeds are limited by the evaporation rate of the. solvent in the case of dry spinning and by the coagulation rate of the polymer in the spinning in a suitable bath The formation of articles by melt extrusion processes is however extremely difficult because the polyacrylonitrile (PNA) containing at least 85% by weight of acrylonitrile cannot be melted without decomposition.



   The processes using the extrusion of the molten material known before this invention required the two separate operations, that of spinning followed by that of drawing, and the solvent-free fibers in the state they were immediately after spinning were little. solid and were not suitable for use as a textile material except for special purposes until they had been stretched. The tenacity of the yarn after spinning was 0.5 to 0.8 gpd at elongations up to 10%. By elongation during which the orientation takes place according to

 <Desc / Clms Page number 2>

 the main axis yields usable fibers with a tenacity of up to 4 to 6 gpd.

   On the other hand, yarns which do not substantially contain solvents produced according to the present process can be used directly.



   It is evident that the development of a process which utilizes the extrusion of the molten material and enables the production of usable yarns as such after spinning would constitute a considerable economic advance. Eliminating the need for drawing after the normal spinning operation would result in a considerable saving in both labor and equipment and would lead to a substantial increase in production. In addition, for a given production capacity, less space would be necessary since it would be possible to eliminate the space currently used for drawing the wire.



     A great effort has been made in the research to discover and develop a satisfactory substitute for natural wool. Various synthetic fibers have been subjected to various treatments, both mechanical and chemical, in an attempt to modify their properties in such a way that they can replace wool.



  The possibility of using equipment for producing fibran and waving it, as well as various chemical or thermal processes relating to the treatment of synthetic fibers, has been discussed at length, trying to obtain the characteristics which are normally present. those of natural wool. However, in no case has it been possible to regard such synthetic products as wool-like products, except from the point of view of their external appearance. A great and new field of use would open up for synthetic fiber which could be transformed by weaving into a fabric having the feel, elasticity, non-wrinkling ability, consistency, warmth and others. properties which are normally those of finely woven woolen fabrics.



   The present invention aims, among other things, to provide a process for converting the normally infusible acrylonitrile polymers into fibers and threads which are solid as they are after spinning and do not require drawing after spinning. The invention also aims to provide a process for the high speed spinning of the fibers of acrylonitrile polymers of textile denier and to provide yarns which have the ability to wave spontaneously, providing a product having the feel. the elasticity and the ability not to wrinkle characteristic of fine wool. Another aim of the invention is to transform the yarn obtained by spinning and which does not have the characteristics of wool into a material comparable to wool.



  Other characteristics will result from the description which follows.



   The objects of the invention are achieved by extrusion through an orifice. of suitable shape and opening into an inert material of a mixture of an acrylonitrile polymer comprising at least 85% by weight of acrylonitrile and from 30 to 60% of a plasticizer of the acrylonitrile polymer, the material extruded being cooled to solidification as fibers, which are thinned by winding or entraining the solidified fibers in the direction of the next station at a rate which, measured after the fibers have been completely solidified, is equal at least 30 times the ejection speed. The mixtures are extruded in air at room temperature and solidification takes place rapidly as the filaments are drawn away from the die at the desired speed and then washed to remove plasticizers.

   The fibers and yarns of high strength obtained by spinning are relaxed in this state and allowed to shrink at a temperature between about 90 ° C and about 200 ° C.



  The material obtained undulates spontaneously and exhibits the characteristic elasticity of fine wool.



   In preparing the elastic threads which can be used according to the invention, the following general process is used. The polymer is mixed with a suitable plasticizer, for example in a Banbury mixer, or dough mixer, so as to obtain a mixture of the desired solid concentration, i.e. between 40 and 70% by weight of polymer. This mixture which

 <Desc / Clms Page number 3>

 constitutes a solid at room temperature is melted and is pumped with the aid of a metering pump of the type commonly used in the textile industry of synthetics through a filter and dies from which it dissolves. - mouth in air which is also at room temperature.

   The extruded filaments cool and solidify by passage in air and are taken up after solidification by a device which drives them at a speed equal to at least 30 times that of ejection. The spinning speed, that is, the speed of the yarn at a point where complete solidification has already taken place, when no further reduction in denier is observed; must be greater than 914 m per minute and can reach 6400 m per minute and more. Obviously, the speed of a stream of extruded polymer will not be the same while it is in a fluid or semi-fluid state as at the point where it is coiled or driven. The ratio of the winding speed to the ejection speed will hereinafter be called the spin-draw ratio.

   It can be calculated from the equality R = VdA, equality in which R is equal to the spin-draw ratio, V is the speed of solid filaments in centimeters per minute, d is the density of the molten mixture in grams per cm3, A is the area of the die hole in cm2, 1 is the extrusion speed in grams per minute through the die hole.



   The filament drive device may include a high speed wheel, a nip roller or roller, an air jet, or the like. Under the impulse imparted by the driving device the filaments elongate in the interval between the spinneret and the point of complete solidification. The inertia of the material and the resistance of the surrounding air seem to cause sufficient traction on the filaments to cause orientation of the polymer molecules in the solidification zone.

   In this area it can be seen that the filaments accelerate their speed and become stretched fibers which move at high speed in the direction of their length. The phenomenon can further be detected by observing the air entrained with the filaments from from the area where solidification begins. It is the orientation which occurs at this point which explains some of the useful properties of the elastic yarn spun according to the process of the invention.



   When the polymer-based mixture is extruded in air at room temperature, the resulting filaments are allowed to move for at least 50 to 75 cm before reaching the driving device in order to ensure their complete solidification. . When this distance is less than 50 cm, the molten filaments can be obtained with a normal spinning process in all other respects because the cooling time is insufficient.

   This distance can be shortened and higher speeds achieved by carefully blowing air over the filaments just below the die,
In the preparation of the fibranne, the filaments coming from the spinneret are fed to a high-speed cutting device after which the fibranne is extracted to remove the solvent therefrom and heated to a temperature between about 90 and about 1000 ° C. relaxed state.



   All of the fibers and yarns prepared according to the present invention have the ability to wave spontaneously. This term is applied here to the kind of corrugation which appears in the fibers obtained by the process of the invention when the fibers are released after being heated to a high temperature under low tension or without tension and it is to be distinguished this undulation from that obtained by mechanical means.



   In general, spontaneous crimping is observed when the yarns and fibers are heated to about 100 ° C within the larger area mentioned above, that is, between 190 and 200 ° C. allows the filaments to shrink until the fibers begin to undulate spontaneously and usually to as great an extent as possible. This usually happens very quickly.



   Means suitable for heating in the process phase.

 <Desc / Clms Page number 4>

 where the ripple is obtained include hot air, hot or boiling water, saturated or superheated steam and various hot solutions which exert a mild plasticizing action on the filaments. This heat treatment also stabilizes the yarn and increases the degree of crystallization while reducing residual shrinkage. In the preparation of fibranne, the yarn loaded with solvent coming from the cutting device is caused to give up its solvent and is then released at a temperature between 90 C and 200 C, or else the extraction of the solvent and the release can take place simul. - temporarily, for example in hot water.



   The yarns and fibers prepared according to the invention, besides resembling wool because of their corrugation, possess the property of wool which is perhaps the most difficult to reproduce, namely its elasticity. It is not easily quantitatively measurable, - but it can be defined to a large extent by three important parameters; the initial tensile modulus, the recovery after tension, and the strain ratio.



   The "initial tensile modulus" represented by the symbol Mi is defined by the slope of the first substantially straight portion of the stress-strain curve of the material with a funicular structure obtained by taking the tension on the y-axis and the elongation on the x-axis, when the material is stretched at a rate of 10% per minute under normal temperature and humidity conditions (21 ° C. and 60% RH). Almost always this first substantially straight portion of the curve is also that of which the slope is the most pronounced. The values used here are expressed in KGs per mm2 for 100% elongation.



   The initial tensile modulus Mi is a measure of resistance to extension and bending. The effects of the filament's own modulus are felt in a fabric when it is folded or crumpled in the hand or otherwise manipulated. If the coefficient is too low the fabric is "like rubber" or "soft"; if it is too strong, the fabric is stiff or stiff. When this coefficient has a suitable value, a soft fabric is obtained. Attempts have been made to compensate for the effects resulting from the fact that the coefficient of a given fabric is outside the limits specific to wool by a suitable adjustment of the diameter of the filament.

   However, whenever one deviates from the usual dimensions of the diameter of the wool filaments, this has resulted in a deleterious effect on properties such as flexibility or the ability to return to the original shape after folding. The properties of the filaments are almost exclusively dependent on the resistance of the fabric to folding, the initial modulus and the diameter, and the range of suitable diameters appears to be limited to those characteristic of wool. Fabrics having a wool-like feel are obtained when the fibers have an initial modulus within the range of wool moduli.



   "Tensile recovery" (TR) is defined as the extent to which the wire returns to its original length after extension, a stress-strain curve being used to determine recovery after tension under test conditions. The test consists of stretching a funicular structure at a constant rate of 10% per minute. A sample is maintained at the maximum desired elongation for 30 seconds, for example by employing a time switch. This sample is then allowed to retract at the same rate at which it was stretched. The same sample is extended by 1.3 and 5% for each determination. The elongation during stretching and recovery during retraction are measured along the axis of the elongation.

   The "recovery after pull" is then the ratio of the length to which the wire returns and that to which it had been stretched. This test is carried out under the standard conditions of 60% R.H. and 21 C.



   It is well known that resistance to creasing and creasing and the ability to return to a smooth state after each crease formation, which is unavoidable, are highly desirable characteristics in fabrics intended for the manufacture of clothing. clothing. The "re-

 <Desc / Clms Page number 5>

   cuperation after trection "is to a large extent linked to the existence of these qualities.



   "Pull recovery !! after 1% elongation is the ability of the tissue to return to its original appearance after moderate wrinkling and, as might be expected," pull recovery. "after more considerable elongations corresponds to the capacity of the fabric to return to its initial state after a more thorough wrinkling involving the formation of very pronounced folds. In this case the words" resistance to "can be substituted for the words" recovery after " "since the resistance to creasing or creasing corresponds to a very rapid and very complete return to the initial state after creasing or crumpling, when the force which causes them has disappeared.



   The "strain ratio" (GR) is related to the shape of the stress-strain curve and is a measure of strain as a function of elongation. Deformation is defined as the elongation divided by the force in kg / mm2. Hook systems for which the stress-strain curve is a straight line have equal strain for all lengthenings; for such systems the change in cough or strain ratio is zero. On the other hand, one of the most important qualities of wool is its tendency towards higher deformation rates as it is progressively deformed. It is this property that makes wool feel both soft and firm.

   This property is measured by determining the average rate at which the rate of deformation changes in the zone of elongations between 5 and 10% and is calculated by the following formula
CR = 1/5 (10 / tension for an elongation of 10% -5 / tension for an elongation of 5%)
The tension-deformation curve of wool has two distinctly different regions consisting on the one hand of an initial portion in which the resistance to deformation is relatively high and on the other hand of a subsequent portion in which the resistance decreases steadily. 'an important way. It is for this reason that a woolen fabric which is firm and elastic to the touch becomes soft and soft when it has been crushed several times in the hand.

   Among natural fibers this double behavior is only found in wool fibers and other animal hair (and not in silk, cotton, etc.) and it constitutes one of the most interesting and most interesting characteristics. most valuable wool.



   Using the methods of measuring wool elasticity just described, it has been found that the above three parameters of the best outer garment wools are within the following limits.
Mi = 110 to 550 kg / mm2
CR = 0.05 to 0.17 TR = 55% and more for elongations of 3%.



   The process according to the invention makes it possible to obtain synthetic threads and fibers which have the elasticity of wool within the above limits. In addition, these synthetic fibers have the desired elasticity along the length of the fiber. This is achieved by the invention because the filaments undergo uniform treatment along their entire length during their formation and subsequent processing.



   The production of corrugations also reduces toughness and initial tensile modulus (Mi) and increases the strain ratio (CR). The effect exerted on the value of Mi becomes important at high spinning speeds. Frequently yarns spun at speeds in the region of 4570 m / m will initially have values of Mi which exceed the desired limits. However, after the spontaneous undulation operation, the value of Mi decreases sufficiently to be included within these limits.



  This reduction in the value of Mi can be accentuated by creating

 <Desc / Clms Page number 6>

 more pronounced loosening effects than those normally used, for example by resorting to the treatment with value, glycol, glycerine or mineral oil at 160 -200 C and / or by prolonging the treatment longer.



   The process according to the invention will be better understood by referring to the examples which follow. These examples are in no way limiting.



  The proportions and percentages are expressed by weight unless otherwise indicated.



     EXAMPLE 1 ,,
Fifty three parts of a copolymer containing 95% by weight of acrylonitrile and 5% by weight of 2-vinyl-pyridine (intrinsic viscosity 1; 45) and 47 parts of N-acetyl-morpholine are mixed to form a wet powder, then kneaded in a Banbury mixer for fifteen minutes at low speed, circulating in the mixer chamber water at 30 C. The mixture turns during the first minute into a resinous mass, similar to kneaded rubber and its temperature. * rises to about 100 ° C at the end of this cycle due to the heat given off during mixing of the mixture.

   The rubbery consistency mixture is then withdrawn from the mixer and placed in a spinning cylinder under pressure equipped with a cylinder and a piston in order to be able to apply pressure to the mixture and to an external heater controlled by thermostat. . A stainless steel die with a 0.25 mm hole, controlled by an independent thermostat, is fixed in the lower portion of the cylinder. With a temperature of 130 G in the cylinder, 16,800 at the die and a pressure of 105 kg / cm2 exerted on the mass and giving a flow rate of 1.8 grams ¯ per minute, the wire is pulled by a air jet vacuum cleaner at a speed of 2742 m. per minute and picked up on a sieve.

   The yarn is subjected in the relaxed state overnight to washing with running water, cold and gentle, then centrifuged and dried for one hour at 125 G. It is then boiled in a solution of aqueous soap at 0. 1%, rinsed in water and dried in a relaxed state at 55 C. The final dry denier is 4.4 and the yarn has a tenacity of 1.6 grams per denier for elongation. breakage of 28%. Its elasticity corresponds to an initial modulus of 441 kg / mm2, a deformation ratio of 0.077 and a tensile recovery of 73% at an elongation of 3%.



     EXAMPLE II. -
The results of a series of experiments are summarized in the attached table. The first column of the table indicates the polymer used, the polyacrylonitrile being the homopolymer of acrylonitrile; the copolymer A denotes a copolymer containing 95% acrylonitrile and 5% 2-vinyl-pyridine; copolymer B denotes a copolymer containing 97% acrylonitrile and 3% methacrylic acid; copolymer C denotes a copolymer containing 95% acrylonitrile and 5% methyl acrylate; Copolymer D denotes a copolymer containing 96.8% acrylonitrile and 3.2% styrene; copolymer E indicates a copolymer containing 96.8-% acrylonitrile and 3.2% methacrylonitrile;

   copolymer F denotes a copolymer containing 95% acrylonitrile and 5% methyl methacrylate. The intrinsic viscosities were obtained from dilute solutions of polymers in dimethylformamide.

 <Desc / Clms Page number 7>

 



  . TABLE I -
 EMI7.1
 
<tb> Polymer-
<tb>
 
 EMI7.2
 re or G o- 1 2 3 4 5 6 7 8 9 10 11; 12: 13 14 polymer .A1TP 1.05 mM3 52 10 / 0.25 1.00 1251 72 503.8 1.20 13, 3491 0 , 073 60 Il 1.05 EC 58 10 / 0.25 1.00 1902 115 3o 2.7 1.35 15.0 451 0.067 63 1.05 EC 65 10 / 0.25 0.95 4.61 89 30 3, 9 1, 21 18.2 400 0.075: 65 "0.77 DMF 54 5 / 0.25 0.60 5299 158 45 2.2 1.91 15.3 455-0.064! 62 A 1.05 TMS 54 7 / 0.36 5.00 1902 46.5 30 25, C: 05 28.0 236 oil 70 z00 'IM3 58 5 / 0.25 3.00 6399 123 2.9 1.80 20.2 451 0.056: 62 Il 1.05 TMS 58 40 / 0.25 0.67 1737 149 50 2.5 l, 51 34.0 338 0.100 67 B 0.90 IMS 58 3 / 0.25 3.10 3657 68 50 5.2 1, 42 32.0 410 0.071: 64 C 1.03 'IM3 58 3 / 0.25 1.93 3930 121 50 3.0 1553 32.7 381 D 0.96 ES 58 5 / 0.25 0.98 2193 135 50 2.7 1.49 35.1 321 E 0, 97 7MS 53 5 / 0.25 0, 90 1278 94 50 3, 9 0, 99 31, 2 287 F 1.08 FMS 58 3 / 0.25 1 , 33 2376 108 50 3.4 1.37 30;

  ? 363 1. - Intrinsic viscosity 2, - Plasticizer 3. -% polymer
4.- Die holes / dimensions in millimeters
5. - Flow rate gram / minute / hole
6. - Spinning speed meters / minute.



   7. - Extension report
8. - Extraction temperature in degrees C
9. - Denier / filament
10.- Tenacity grams / denier 11.-% Elongation at break
12.- Initial tensile modulus (kg / mm2)
13.- Deformation report
14.- Recovery after traction
Three different plasticizers were used; TMS denotes cyclic tetramethylene sulfone; EC stands for cyclic-carbonate '
 EMI7.3
 ethylene; DMF symbolizes N., N-dimethylformamide. Several dies having from three to forty holes are used, the diameter generally being 0.25 mm. The flow rate is recorded in grams of mix per hole per minute. The spinning speed or gathering point is represented in meters per minute.

   The extension ratio (or spin-draw ratio) was calculated from the equality R = Vd A defined more
W high. The density of the acrylonitrile polymers used in these experiments was 1.14 (g / cm3).



   While the polymer is agitated in the paste mixer, the plasticizer is introduced into the mixer as a fine dust. The premix thus obtained is constituted by a coarse-grained powder. ,, slightly moist. A standard Royle plastic extruder with a metering screw is used to convert the powdered premix into a resinous mass and to meter the flow of the mass through the sand filter to the die. . The rear portion of the extruder is kept substantially at normal indoor temperature to prevent the premix from prematurely agglutinating, which

 <Desc / Clms Page number 8>

 would make feeding difficult. The front portion of the extruder is heated to approximately 155 C.

   An adapter containing the filters and the die is attached to the front of the extruder and is maintained at spinning temperature, i.e. 190 C. The filter consists of a top layer of 12.5 mm of sand corresponding to 60 to 80 mesh sieves and a lower layer of 12.5 mm of sand corresponding to 100 to 150 mesh sieves (American standards). -
The premix thus obtained is fed into the hopper of the extruder. With the screw rotating at about ten revolutions per minute, the premix is made into a paste and delivered under a pressure of about 562 kg / cm 2 to the die. The extruded filaments are passed through a jet of air which accelerates their movement to the desired speed. A flying knife is used to cut the fibranne to 75mm in length.

   This is collected in a basket and transported as a load to a bath intended for. extract the water. As indicated in the attached table, the extraction temperatures range from room temperature to that of 50 ° C., the extraction lasting one hour. Following the extraction, the fibran is boiled in water for one hour; during boiling it spontaneously takes on ripple.



   The results collated in the table above show that the process according to the invention is applicable both to homopolymers and to copolymers of acrylonitrile with other polymerizable ethylenically unsaturated monomers in a whole range of compositions with various plasticizers for polymers. The spinning conditions of the gummy mass supplied and a wire speed resulting in aspect ratios greater than 30 cover a wide area. The elasticity properties of the products obtained are well included in the range of those of the finished wool. The tensile strength of these products is generally higher for a high rate of spinning elongation.



   Although US Patents Nos. 2,404,714 to 2,404,722 of November 4, 1944, 2,404,723 of November 10, 1944, 2,404,724 to 2,404,726 of November 18, 1944 and 2,404,727 of December 14, 1944 indicate that the solvents of the polymers of polyacrylonitrile and d Acrylonitrile containing at least 85% by weight of acrylonitrile constitute plasticizers for these polymers, it is not indicated there, nor elsewhere either, that the spinning of these bodies in the molten state is possible.

   The polymers used according to the invention have such a high melting point and are so poorly fluid that the spinning of these polymers in the molten state has long been considered impossible and attempts to extrude polymers containing at least 85% d Acrylonitrile through very small orifices of a die had heretofore failed.



   Further, a solution of a polymer of the type used in the present invention in a solvent has different properties from those of a comparable solution of the same polymer in a different type of solvent. When solutions of polyacrylonitrile, in dimethylformamide on the one hand and in ethylene cyclic carbonate on the other hand, are compared from the point of view of their usefulness with regard to spinning, at about 100 C (as for example for wet spinning in a hot dilute aqueous bath) it has been found that a much lower polymer concentration must be used in a solution of ethylene cyclic carbonate than in a solution of dimethylformamide. While a content of 22% polymer is suitable for example in the case of the latter solvent,

   Only 13%, for example, should be used in the case of the first to obtain a solution of equal viscosity. This difference remains in the melts of this invention.



  Dimethylformamide is a more effective plasticizer than ethylene carbonate and the dimethylformamide-polymer mixture should contain a much greater percentage of polymer than the ethylene carbonate-polymer mixture of the same viscosity. The stability of the polymers as well as the change in the properties of the solution did not predict the achievement of proper fluidity of the polymer-plasticizer blends which are solid at ordinary temperatures. It is truly surprising that all of the blends of this invention can be melt spun in the same

 <Desc / Clms Page number 9>

 terms and conditions.



   For this melt spinning process, the concentration of solids in the spinning paste can be of the order of 40 to 70% by weight.



  Blends with higher solids concentrations, i.e. more than 70% acrylonitrile polymer, have been spun, but high speed spinning is done with concentrations below 70%.



  It is also difficult to obtain the homogeneity necessary to obtain satisfactory spinning using a more concentrated mixture. While the blends having a polymer content reduced to 40% have been spun by the process according to the invention, there is little advantage in using larger amounts of plasticizers. In fact, when the polymer concentration is less than 45% by weight, the filaments tend to become tacky and stick together unless they are coated with talc prior to assembly. Hence the preferred polymer concentration of the spinning paste is between 50 to 58%.



   The filaments prepared according to the process of the invention adapt well to the shape of the hole in the die. Thus, round filaments are obtained with ordinary circular hole dies. This contrasts with the results obtained when the same die is used for the wet spinning or the dry spinning of an acrylonitrile polymer solution. Dry spinning generally produces filaments which are "dog bone shaped" in section, while wet spinning filaments are generally crenellated. Filament friction can be obtained by producing filaments which are not round in section, using dies with non-circular holes.

   For example, filaments are obtained by spinning the spinning paste used according to the invention through a die having five cruciform holes (cross 0.8 mm wide, arm thickness 0.076 mm), The die behaves very well at speeds equal to those used with round hole dies, the filaments not sticking to the edges and filaments are obtained which give a star in cross section. When these filaments are treated as a fibran they are significantly rougher compared to the round filaments which are smooth.



   It is preferable to heat the spinning dough to temperatures between 100 and 150 C before it reaches the die. To obtain the best spinning the die should be maintained at a temperature of 140-205 C and preferably at 180-190 C. Pressure should be used to bring the polymer in solution to the metering pump. For example, an attempt has been made to spin a 45% polymer paste with standard wire equipment using a heated grid to melt the material ahead of the pump. However, the material would not flow by gravity through a heated grid even if it were held at 155 ° C for two hours. Higher temperature would produce rapid darkening.

   The pastes of the invention have "non-Newtonian winding" characteristics and flow easily only under considerable shear. The pressures required for the supply of spinning paste depend essentially on the filter. Pressures of 3.5 kg / cm2 and up to 775 kg / cm2 can be used to achieve good spinning depending on the filtering efficiency desired. When using a coarse sand filter, only very low pressures are needed, eg less than 3.5 kg / cm2. The melt has to be filtered and the pressure required for the spinning must of course be adjusted to obtain the desired flow rate.



   Well homogenized mixtures are used to obtain good spinning. Any conventional mixing technique can be used; for example, it is possible to mix for about 15 to 30 minutes, using equipment such as the Banbury mixer at temperatures between 30 and 100 C. When using poorly soluble acrylonitrile polymers containing at least 85% by weight of acrylonitrile, the shorter-lasting blends do not give the desired homogeneity to achieve good, rapid spinning. On the other hand, if the mixing lasts longer than an hour it leads to excessive decomposition and undesirable coloring. The process described in the example

 <Desc / Clms Page number 10>

 ple II gives full satisfaction.

   On the other hand, it is possible to produce highly concentrated mixtures of high molecular weight acrylonitrile in the plasticizer by polymerizing the acrylonitrile monomer in a dispersion of the plasticizer. Intimate polymer-plasticizer blends are obtained directly. This polymerization process eliminates the need for mixing and avoids the decomposition and discoloration which accompanies mixing.



   Among the many plasticizers which can be used to obtain the solid mixtures according to the invention, intended to be subsequently spun in the molten state, there may be mentioned the following substances: N-acetyl morpholine; cyclic ethylene carbonate; cyclic tetramethylene sulfone; N, N-dimethylformamide; N, N-dimethylacetamide; N-methyl-N-cyanoethylformamide, ethylene sulfite, N, N-dimethyl hydroxyacetamide; N, N-dimethylmethoxyacetamide; N-formylhexamethylene imine; p-phenylene diamine; m and p-nitro-phenol, succinitrile, glyconitrile; succinic anhydride; diglycolic anhydride;

   N, N'-diformylpiperazine, and all substances described as solvents in United States Patents 2,404,714 to 2,404. 727 inclusive, cited above, and any mixture of the aforesaid substances.



   Mixtures of all of the plasticizers of this invention can be used; for example, mixtures of butyrolactone and ethylene carbonate have been used in the preparation of the dough according to the invention.



   The term “acrylonitrile polymer containing at least 85%: by weight of acrylonitrile” is understood to mean the polyacrylonitrile homopolymer and the acrylonitrile copolymers in which at least 85% by weight are derived from acrylonitrile.



  In the copolymers, the remaining 15% is derived from monomers which can be copolymerized with acrylonitrile. The latter are generally ethylenically unsaturated monomers such as the following substances: styrene,; methyl-vinyl-ketone, esters of metacrylic and acrylic acids, halides of vinyl and vinylidene, such as vinyl chloride , vinyl fluoride, vinylidene chloride, vinylidene fluoride, vinylidene chlorofluoride, vinylidene cyanide, butadiene, vinyl-pyridine-acrylamide, and N-mono and di-substituted acrylic amides. The polymers can be prepared by one of the well known polymerization methods such as those described in US Patents Nos.

   2,436,926 of February 2, 1945, 2,486,241 of September 17, 1945, 2,491,471 of February 25, 1948 and 2,546,238 of February 18, 1948. Monomers are added during the polymerization as reagents and in this invention one can use two or three component copolymers and even more. Also, non-acrylonitrile monomers can be polymerized separately and mixed with the polyacrylonitriles. In both cases the amount of modifier in the final polymer product should not exceed 15% by weight.



   Of course, it is recognized that the conditions of temperature, concentration, pressure, etc., will vary somewhat depending on the plasticizer and the polymers used, but generally the conditions used are substantially the same. The concentration of solid in the mixture is between 40 to 70% of the mixture. The temperatures used are between 140 and 23CPC approximately. Spinning is best done at temperatures below 200 ° C and temperatures of around 180 ° C to 190 ° C are generally used. In any case, it is best to prepare the mixture as quickly as possible and at as low a temperature. as possible to avoid decomposition and discoloration.

   In all cases the extruded mixture is allowed to solidify quickly without appreciable removal of solvent. The extrusion is generally carried out in an inert atmosphere, such as air at a generally low temperature, for example room temperature. Of course, higher or lower temperatures can be used, but this provides no advantage in this invention. The filaments are then washed and heated while allowed to shrink freely, at about 90 ° C to 20CPC for a short time.



   Mixing can be done in about half an hour in a

 <Desc / Clms Page number 11>

 Banbury mixer at temperatures between about 6000 and -8000 -, approx. When using the process according to the invention, the intrinsic viscosity and the molecular weights of the polymers decrease considerably. If high molecular weight polymers (50,000 or more) are used, this reduction helps spinning.

   If the molecular weight is lower the mixtures can be prepared by pouring the polymers into a mixing chamber containing the polymer at room temperature. The mixture is then passed to the die by means of a device. screw extrusion heated to 100-130 ° C. and a very small reduction in molecular weight and viscosity takes place. According to the invention, the viscosity of the mixture is preferably between about 1,000 and about 4,000 poise, at a spinning temperature of about 180 ° C. The molecular weights of the polymers are between about 20,000 and about 50,000 and the intrinsic viscosity calculated according to the Staudinger process is between about 0.5 and 1.6.



   As long as the spin-to-odd ratio, as defined above, is kept at 30 or above, the spinning speed can vary within wide limits, depending on the exact characteristics one wishes to give to the yarns obtained. In general, the minimum speed to obtain a product which resembles wool and has a tenacity of at least 1 gr. per denier will be 914 m per minute. Higher spinning speeds result in yarn having greater tenacity and lower shrinkage and speeds up to $ .400 m / min have been achieved. Fibers which have the appearance and elasticity of wool after relaxation in hot water or hot air are obtained at all spinning speeds from 914 m / min and above.

   One critical characteristic is the spin-draw ratio. If this ratio is less than 30, the products obtained do not have the desired strength and elasticity.



   The spinning speeds essential to this process can be achieved in several ways. A driven spool, a high speed bobbin and an air jet can be used as tensioning and driving devices in which the yarn combined with other yarns to form a cable can be drawn directly to a cable. fibranne cutting device or the corrugating device without intermediate winding.



   The plasticizer can be drained from the resulting yarn by coating it with a solvent which dissolves this plasticizer without dissolving the yarn. Water is generally preferred for extracting the plasticizer for economic reasons, but other substances such as acetone, alcohol, ether, chlorinated hydrocarbons, etc. can be used. Sometimes it is advantageous to give the finish a certain finish. yarns or fibranne during their extraction process by incorporating a small amount of finishing products in the extraction liquor. The final properties are hardly affected by the extraction temperature, as long as this is less than about 80 ° C.

   Temperatures above 80 ° C generally produce a yarn with lower tenacity, a lower initial modulus, and a slightly higher strain ratio. Although these yarns are usable and have the properties of wool, the higher temperatures are not used.



  In general, the extraction is carried out with water at 50 ° C., since this makes it possible to have a yarn having better qualities and because the process is less expensive.



   The fibers prepared by this process can be caused to wave spontaneously by treatment in the relaxed state in water at 90 ° C. to about 100 ° C., or in air heated from about 95 ° C. to 200 ° C. about. Fibers which shrink by 15-30% wave well when supported on a continuous surface, for example on a moving belt in an oven.

   The preferred method of corrugation is to support the fibers by a current of air heated to a temperature of 95 to 200 C. This method of corrugation is highly efficient and fast and enables satisfactory corrugation within seconds. fibers having shrinkages which can go down to 3% and on the other hand reach

 <Desc / Clms Page number 12>

 30% and more. A convenient method is to blow the fibranne through a pneumatic tube supplied with hot air at a temperature of about 150 C.



  Another convenient method is to expose the fibers to a shower of hot water for a few seconds.



   The fibers prepared by this process not only reproduce the appearance of fine wool fibers, but also have their important characteristics in terms of initial tensile modulus, tensile recovery and strain ratio, --This enables a wool-like fabric to be produced with the aid of these fibers, such a fabric being elastic and firm to the touch, and yet soft and soft when it has been strongly crumpled in the hand. These fibers and yarns made of a material based on acrylonitrile polymer have moreover a strength and a resistance to wear superior to those of wool fibers and are not attacked by moths.



   The fabrics obtained with these fibers are pleasant, resist crumpling, drape well and keep the folds that are imprinted on them well.



  They are remarkably insensitive to water and to changes in humidity. The uses to which they lend themselves once transformed into fabric outnumber those of wool. They are suitable for use, in particular in the form of staple fibers, for felts of various types, including felts used by manufacturers of paper, rugs, men's and women's clothing, bathing suits, sweaters, yarn. to knit, as a chain as soon as you use toiletries, etc ...



   Particularly noteworthy are the costume fabrics made from the fiber staple according to the invention. They are equivalent to the best of the best woolen fabrics from the standpoint of wrinkle resistance, the ability to revert to the prior condition after crumpling and preservation of wrinkles obtained with an iron. The pants can be cleaned by washing in an automatic washer after which they are hung up to be dried; they do not shrink appreciably, retain their original folds and do not require ironing.



   This invention provides a highly useful and economical process for the preparation of fibers and yarns from acrylonitrile polymers, such yarns possessing highly desirable physical qualities and of great commercial value. Unlike dry spinning techniques, the process according to the invention results in a reduced expenditure of solvent and does not require a heated cell: the investments are lower; yield is increased and handling reduced. Subsequent hot stretch orientation is eliminated. The same advantages exist compared to wet spinning techniques. The speeds are greater and the costs are reduced if the plasticizers are used in relatively small amounts and the coagulation bath is not required.

   Low denier yarns can be spun at very high speeds by extruding the viscous or plasticized mass through dies under relatively high pressure. Further, the process is particularly suitable for the preparation of filaments having sections of particular shape, since the filaments take the shape of the orifice better than in dry spinning or wet spinning, using orifices having this kind of shape. In fact the conformation is better than that obtained in the spinning of unplasticized melts as is the case with "nylon". The process also allows the use of high boiling point plasticizers which are solvents but are not particularly useful for dry spinning because of their high boiling point.



   The foregoing description shows that the invention provides a very rapid direct process for the spinning of acrylonitrile polymers under conditions such that the fibers and threads spontaneously undulate so as to give the desired elastic structure. The process achieves this result without the need for subsequent stretching. The fibers and yarns can pass directly from the spinning to the washing and the operation which causes the crimping to form in one continuous operation highly useful fibers and yarns.

 <Desc / Clms Page number 13>




    

Claims (1)

Of course, the invention is not limited to the embodiments described which have only been given by way of example. ABSTRACT. The main objects of the invention are: 1 -. A process for spinning acrylonitrile polymers, remarkable in particular by the following characteristics considered separately or in combinations: a) an aerylonitrile polymer of which at least 85% by weight is derived from acrylonitrile is mixed with a plasticizer of this polymer to produce a mass containing about 30% to 60% of this plasticizer, this mixture is extruded by application of heat and pressure, through an orifice having a defined shape, in an inert atmosphere, the extruded material is cooled and this material is pulled away from this orifice at a speed equal to at least 30 times that of the extrusion; b) the solidified material is washed to remove the plasticizer; c) the speed at which said material is removed from said orifice is at least 914 m / minute; d) this speed is between 914 and 6400 m / minute; e) the extrusion takes place at a temperature of 140 to 230 C and under a pressure of 3.5 to 775 kg / cm2; f) the solidified material is relaxed and shrinks freely at a temperature of about 90 to 200 C; g) the polymer used is entirely polyacrylonitrile; h) the polymer used is a copolymer of acrylonitrile and a vinylpyridine; i) the polymer used is a copolymer of acrylonitrile and methacrylic acid; j) the plasticizer used is cyclic tetramethylenesulfone; k) the plasticizer used is N, N-dimethylformamide; 1) the product obtained is allowed to relax and shrink in a medium comprising air; m) the product obtained is allowed to relax and shrink in a medium comprising water; 2. - Fibers and yarns obtained by the above process and fabrics and other products made with these yarns.