DK147767B - PROCEDURE FOR PREPARING ACRYLONITRIL POLYMER FIBER BY EXTRADING A HOMOGENEOUS SINGLE PHASE POLYMER AND WATER MELT - Google Patents

Description

i o 147767

The present invention relates to a process for preparing acylonitrile polymer fiber by extruding a homogeneous single phase melt of acrylonitrile polymer and water at a temperature above the boiling point at 5 atmospheric pressure and at a pressure where water is kept in liquid state through a spinning nozzle. a vapor-containing solidification zone.

From the specification of LU Patent No. 66 301, it is known to melt spin an acrylonitrile polymer containing 10 a smaller amount of water selected so that over 45% of the nitrilo groups in the polymer are hydrated or 80% of the coupled nitrilo groups are hydrated. The required hydration temperature is determined by rather complicated assays such as thermodifferential analysis or measurement of 15 laser Raman spectra. The polymeric material in question is usually a copolymer containing at least 85% acrylonitrile units. In this known method, special aim is made to produce filaments with a special sheath / core structure by extruding a homogeneous single-phase material 20 through a multi-hole nozzle and into an atmosphere which may be pressurized and may contain water vapor, as well as may contain air or a mixture of water and air. In particular, the aim is to provide different dyeing properties of the sheath 25 and the core and to obtain filaments with a silky diffuse sheen while obtaining a type of effect yarn.

To achieve this diffuse luster, it is worked so that the core portion of the filaments contains a large proportion of micro-cavities, and so that the sheath exhibits streaking, in particular at the subsequent stretching step and subsequent boiling in water, and possibly also relaxation at heating to just under 200 ° in air. According to the embodiments, stretching is in a ratio of 2-8 times, which occurs in a separate step after the spinning operation itself. At the melt spinning, decrease

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2 147767 the newly formed multifilament yarns by direct winding without stretching. It will be seen that the length and depth of the aforementioned stripes which occur in the jacket at the separate stretching stage appear to be increased (though not consistently or consistently) with increasing stretching degree. Whether stretching (in a stretching ratio of 6 times) at the separate stretching step after spinning is performed in an atmosphere of air and water vapor at 64 ° C (Example 8) or in an atmosphere of air and water vapor at 140 ° C (Example 10), 10, the stretched filaments still show the desired micro-cavities in the core portion as well as streaking on the sheath, precisely as intended by the known prior art method, which deals primarily with matters of importance for the degree of hydration of the melt in order to provide a homogeneous melt at a temperature where there is no significant degradation of the polymer but does not contain any actual explanation of how the variations in the atmosphere of the spinning chamber such as variation of pressure, temperature and water vapor content affect the properties of the filaments produced. o Ensure the desired streaking and dyeing ability.

The present invention, on the other hand, is particularly directed to carrying out the method in a particularly rational manner, so that the newly formed filaments are stretched in direct connection to the spinning, ie. while subtracting from the nozzle. It has been found hereby that a surprisingly high stretching ratio can be obtained during orientation, while at the same time saving a great deal of energy 30 by doing the stretching on the still warm but solidified melt. Furthermore, particular aspects of the invention are concerned with drying the newly formed fibers under specific conditions to provide a special balance for the evaporation of water vapor. The purpose of this is to minimize skin formation on the fibers produced, precisely wanting to avoid the above-mentioned sheath / core structure, and on the contrary desiring to form dried fibers which are completely free of micro cavities and on the contrary appear completely clear and achieving full strength without the need to subject them to a separate post-stretching step.

Accordingly, the process according to the invention is characterized in that the solidification zone contains saturated water vapor and is kept at a temperature below the melting point of the polymer / water composition, but not more than 20 ° C below this melting point and that the resulting extrudate is stretched at a stretching ratio of at least 25 times with respect to the linear velocity of the melt through the spinning nozzle while the extrudate is still in the solidification zone.

In a preferred embodiment of the process, the acrylonitrile polymer is melt-spun according to the present invention as a single-phase melt of acrylonitrile and water at a temperature Tf which is above the melting temperature of M and above 100 ° C (boiling water at atmospheric pressure). by extruding the melt through a spinning nozzle directly into a solidification zone maintained under water vapor pressure, maintaining the following conditions: (a) the water vapor partial pressure is between 56% and 110% of water vapor pressure at temperature T 2, (b) temperature T is at least 25 as large as the saturation temperature of water at an equal vapor pressure as the partial pressure p, and (c) the total pressure P is at least as large as the partial pressure p, and the newly obtained extrudate is stretched to a tensile ratio of 25 to 250. in the pressurized solidification zone.

In a preferred embodiment of the method according to the invention, the fibers are dried at a temperature above 90 ° C, since water losses from the freshly melt-spun fibers are substantially prevented at temperatures below ca. 90 ° C until drying is complete. This minimizes the 3g tendency for cavities and micro cavities to form in such fibers.

4 o U7767

In the prior art melt spinning of organic polymers such as polyamides, polyesters and polyolefins, and in the known wet spinning or dry spinning of acrylonitrile polymers, the filaments should be extruded and extruded after spinning, e.g. by passing a jet nozzle where they are shredded by the current of e.g. air or water, is subjected to a secondary stretch or stretch to orient the polymer molecules followed by a relaxation step during heating to facilitate or release internal stresses so as to develop the desired good fiber properties. It is therefore quite surprising and unexpected when it has now been found in the present invention that the filaments made by the process of the invention need not be subjected to such a secondary stretching or stretching step. Thus, the characteristic good fiber properties of acrylonitrile polymer fibers can be obtained by the method of the invention merely by relaxing such fibers at elevated temperature. That is, when they are pulled from the spinning nozzle, they are already subjected to a very strong stretch, so that a secondary stretching or stretching step can be completely omitted.

The acrylonitrile polymers which can be used in the process of the invention are polymer or polymer blends containing over 50 mol% acrylonitrile units. In addition to homopolyacrylonitrile, copolymers of acrylonitrile with one or more copolymerizable monoolefinic monomers can be used. Such monomers include acrylic acid, α-chloroacrylic acid and methacrylic acid, the methacrylates such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, methoxymethyl methacrylate, β-chloroethyl methacrylate, and the corresponding esters of acrylic acid and vinyl chloride, bromide, vinylidene chloride, allyl chloride, 1-chloro-1-bromethylene, methacrylonitrile, allyl alcohol, acrylamide and methacrylamide, α-chloroacrylamide or monoalkyl substituted products thereof, methyl vinyl ketone, vinyl carboxylate, vinyl carboxylate vinyl acetate, vinyl chloroacetate, vinyl propionate, vinyl stearate and vinyl benzoate, N-vinylimides such as N-vinylphthalimide and N-vinylsuccinimide, methylene malonic acid esters, itaconic acid and itaconic acid esters, N-vinylcarbazole, vinyl furanol p-methallyloxybenzenesulfonic acid and their salts, ethylene-α, β-dicarboxylic acids or their anhydr ids or derivatives such as diethyl citraconate, diethyl mesaconate, styrene, dibromo styrene, vinyl naphthalene, vinyl substituted tertiary heterocyclic amines such as the vinyl pyridines and alkyl substituted vinyl pyridines, e.g. 2 - vinylpyridine, 4-vinylpyridine, 2-methyl-5-vinylpyridine and the like, 1-vinylimidazole and alkyl-substituted 1-vinylimidazoles such as 2-, 4- or 5-methyl-1-vinylimidazole, vinylpyrrolidone, vinylpiperidone and other monoolefinic copolymerizable monomeric materials. Acrylonitrile polymers or polymer blends may contain varying amounts of units of one or more comonomers, e.g. total approx. 5, 10, 15, 20, 20 25, 30 or 40 mol% of comonomer, based on the total copolymer material, and may have molecular weights in the range of 10,000 to 200,000 e.g. ca. 20,000, 40,000, 50,000, 60,000, 70,000, 85,000, 100,000 or 130,000.

The degradation range of the acrylonitrile polymer refers to the temperature range within which acrylonitrile polymers suffer degradation, which usually results from discoloration at such temperatures in the normal time to melt and extrude the polymeric material. Usually, this degradation region begins at about 180 ° C to approx. 220 ° C, depending on the polymer composition, etc. and extending upwardly therefrom. Where the quality of the polymer in the product is not critical and where some polymer degradation can be tolerated, the single-phase melt can be heated to temperatures all the way into the degradation region, but generally lower temperatures are preferred to avoid degradation. Most often, one wishes that 147767

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The 6 fibers were as free of voids and micro voids as possible, namely to ensure better tensile strength and higher wear resistance and better colorability of the denser fibers which are void free. These advantages are precisely achieved by the present invention by which the acrylonitrile polymer fibers are melt spun to prevent the development of voids or micro voids.

The single phase melt of acrylonitrile polymer and water for melt spinning contains somewhere between approx. 10% and approx. 35% water, which depends on the acrylic polymer composition and other variables. These approx. 10 to approx. 35% water must be evaporated, either immediately or later, to produce the dry acrylonitrile polymer fibers found in the finished products such as fabrics, especially apparel, rugs, carpets, etc. As used herein, "dry" fibers are such as containing approximately the equilibrium moisture the fibers assume after being exposed to ambient conditions of inferior moisture content.

For acrylonitrile polymer fibers, this means that the dry fibers contain less than the approx. 5% retained moisture. The formation of micro cavities in the fibers results from improper drying of the 20 newly spun fibers. Allowing these fibers to cool and dry completely or partially at moderate or low temperatures has shown that voids and micro cavities have been formed. Proper drying to minimize or prevent this phenomenon requires that the newly formed fibers are prevented from losing water until they are dried at elevated temperature, ie. over approx. 90 ° C.

In the process of the present invention, drying of the newly formed fibers is carried out immediately after spinning into a hot water vapor-containing solidification zone under pressure, passing directly into and through a heated chamber in which they are dried in an environment which is maintained over ca. 100 ° C, where the heated chamber can contain air at approx. the same temperature and pressure as the water vapor in the solidification zone.

In another way of proper drying, the newly formed fibers are kept wet (if cooled to below 90 ° C) until they can be dried above 90 ° C. By way of illustration of this feature,

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A process in which the newly formed fibers, after leaving a hot solidification zone under pressure, is cooled in a water bath and then reheated, while still wet, in a dryer operating so that the fibers are dried above 5 90 ° C. In this process sequence, ripple of the newly formed fibers occurs while still wet, but before the initial drying step. The ripple thus obtained is usually very stable and will withstand, among other things, straightening during subsequent textile treatment on e.g. curds, etc., even if exposed to hot water, e.g. in a color bath.

During tests associated with this second type of method, a surprising phenomenon is observed.

When the newly formed fibers, after leaving the spinning nozzle, are cooled to room temperature, the fiber becomes white and matte opaque due to the formation of voids and micro voids therein.

When these white translucent but matte fibers are heated on a hot plate to approx. 120 ° C, they become transparent due to the redissolution of the water in the polymer as the voids and micro-voids disappear. When these transparent fibers are cooled to room temperature immediately after becoming transparent, the white matte translucency reappears due to the water "precipitating" from the polymer and restoring the cavities and microspheres. This phenomenon can be repeated with several heating cooling cycles. However, once the fibers have lost enough water at elevated temperature to make them dry, cooling of the fiber still leads to a transparent fiber which is free of voids and micro cavities.

To determine the working conditions of a specific acrylonitrile polymer, a mixture of the acrylonitrile polymer and water is prepared which is heated under pressure to a sufficient temperature to effect melting. If a single phase melt is produced, the minimum temperature required to induce melting (temperature Μ) is found. Reference is also made to the usual determination of phase diagrams, cf. also FIG. 2 with accompanying text below.

147787 8 o

A series of polymer samples are subjected to saturated water vapor in an autoclave every 5 minutes at rising temperatures. The melting point of the polymer in saturated water vapor is the minimum temperature at which flow occurs. The molten polymer surface looks glassy and polymer particles bond strongly. This minimum temperature is given by line AE, as shown in FIG. 2, which graphically shows the melting point as a function of the water content.

Once the melting line AE is known, the minimum water content necessary for fusion at this temperature is determined. This minimum water content and temperature together constitute point A. At this point, all water is hydrogen bonded to the acrylonitrile polymer, and no free water exists as a secondary phase. A sample of the polymer blended with a known amount of water is placed in a steel cell equipped with a glass window. The cell is sealed to maintain the pressure generated by the sample. The cell is heated in an oil bath so that the sample can be observed at any time. In a series of separate tests, samples containing different water-polymer ratios are placed in the cell and heated to the temperature indicated by line AE. When excess water is present, two phases are visible as the polymer melts. Samples with progressively lower water content are tested until a sample is obtained, where only one phase is visible, giving the point A at this concentration. Upon further reducing the ratio of water to polymer, melting will not occur along the line represented by line AE.

In order to determine the melting range of the phase diagram, it is necessary to ascertain the lines ABF and ACG as shown in FIG. 2. This is done by placing samples of polymer in the steel cell whose water content is in one case 5 to 10% above the water content at the concentration at point A. The line ABF is determined by locating the point representing the temperature and temperature. -

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9, 147767 center at which the mixture of polymer and water with lower volume of water melts into a single phase. The line ACG is found by locating the point at which the two-phase mixture of polymer and water with greater amount of water passes into a single phase after passing through a two-phase liquid state. Since physical mixing is difficult to achieve in the sealed cell, this point can be quite time consuming to arrive.

After locating the point A and the lines ABF and ACG, the line BC is drawn at a temperature approx. 30 ° C above the temperature at point A. The area ABC below the dashed line BC defines the operable single-phase melting region, with temperatures above this decomposing.

Generally, the single-phase melt compositions will be somewhere in the range of between about 10% and approx. 35% water with corresponding 90% to approx. 65% acrylonitrile polyureas. If the single-phase melt composition of a specific acrylonitrile polymer / water mixture is found to have useful low melting points (namely, well below the polymer decomposition temperature range) within a wide range, the method of the invention in particular uses the compositions within such range which represent the lowest amounts. water, especially the lower half of the interval.

Occasionally, the amount of water may vary outside this range, forming a single-phase melt. Eg. more water may be used if a third material is added (such as a water-soluble polymer, a hydrophilic polymer which together with the water forms a melt, a finely divided hydrophilic solid or a hydrophilic liquid) which binds excess water, so that the acrylonitrile polymer occurs in single-phase melt. This third material must not interfere substantially in the formation of a single-phase melt with the water. This third material may be compatible with the acrylonitrile polymer, and the products produced may be a uniform mixture, or the third material may form as permanent embeds therein. This third material may be incompatible, which makes the product easily fibrillable. This material can be easily removed, e.g. by washing with water or organic liquid, leaving a porous structure. Such third materials include hygroscopic or water-soluble polymers such as polyvinyl alcohol, polyethylene glycol, polyacrylamide and derivatives thereof, polyacrylic acid, polyvinylpyrrolidone, polyelectrolytes, proteins such as gelatin, casein and finely divided hydroscopic solids such as silica gel, starch, aluminum chloride, aluminum chloride, aluminum chloride, diatomaceous earths, kaolin clays and molecular sieves and other water-binding agents such as anhydrides, e.g. acetic anhydride, and inorganic salts such as anhydrous sodium sulfate, calcium chloride, sodium phosphate, etc.

According to the present invention, a single phase melt of the acrylonitrile polymer and water is extruded at a temperature (T +) above the minimum fusion temperature (M) of the composition, but preferably not more than 30 ° C above such temperature, through a spinning nozzle directly into a pressurized solidification zone. wherein a certain pressure, a certain temperature and certain composition conditions are maintained. These conditions in the solidification zone, which allow very high stretching ratios and velocities in the jet nozzle, are such that the profile of the composition taken across the cross section of the newly formed extruder remains relatively flat as it moves away from the surface of the nozzle, maintaining a relatively high concentration of melting aid (water) in the newly formed extrudate, and the temperature of the newly formed extrudate is brought down below the extrusion temperature upon cooling, but not more than ca.

35 "below the minimum fusion temperature M." The profile of the composition ... remains relatively flat "means that the concentration of acrylonitrile polymer near the surface of the newly formed extrudate and the concentration of acrylonitrile polymer deep within the newly formed extrudate is no. 5 resembles the same (e.g., no more than about 10% and preferably no more than about 5% different in absolute polymer concentration) for any single cross-section taken in the newly formed extrudate. Of course, the water concentration can be changed in the cross-section of the newly formed extrudate as it moves away from the spinning nozzle by pulling the spun filament through the solidification zone; however, at least 70% of the water concentration in the single-phase fusion melt will still be present. In order to achieve these extrudate conditions in the solidification zone, which are kept under pressure, the ambient conditions therein are preferably controlled, these being observed as follows. The absolute partial pressure p for water vapor therein is preferably 56 to 110% and most preferably between 80 and 100% of water vapor pressure at the extrusion temperature Tf. The temperature T in the stretching zone under pressure is at least as high as the boiling point of water at a vapor pressure equal to the partial pressure of the solidification zone and can go up to a temperature at which substantial degradation of the newly formed extrudate occurs, although it is preferred to maintain the temperature. T near the lower end of the specified 25. The total pressure P in the solidification zone must be at least equal to the partial pressure p, but should preferably not exceed 25 times this partial pressure p. Even higher total pressure can be used; but such are usually undesirable. The value by which the total pressure P exceeds the partial pressure p, if any, derives from other fluids such as air, nitrogen, sulfur dioxide, etc. Preferably, the total pressure P is equal to or does not significantly exceed the partial pressure p, and most preferably there is very little if any other gas or liquid at all. Application of the above conditions in solidification

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The evaporation zone provides boundary control with the evaporation rate of the water from the newly formed extrudate. The term "boundary control" of the evaporation means that the rate of evaporation of water from the surface of the newly formed extrudate is at most equal to the rate of diffusion of water in the newly formed extrudate to its surface, and as a consequence the composition is taken across the newly formed extrudate. cross section relatively uniform while within the solidification zone.

While the newly formed extrudate is in this solidification zone, a downward stretch is transmitted by passing through a jet nozzle to a tensile ratio of 25 and up to 250, but preferably from 35 to 150. The linear velocity through the spinning nozzle is calculated on the computer by 15 divide the volume per time unit of the melt, which is extruded with the total cross-sectional area of all the openings in the spinning nozzle. The tensile ratio of the spun filament bundle is the linear velocity when passing a pulling member (such as a driven cylinder or wire feed roller whose peripheral velocity is set equal to the linear velocity of the filament bundle) divided by the linear velocity through the spinning nozzle.

Outside of the above defined ranges of temperature, pressure and composition conditions for the solidification zone environment, such extremely high tensile rates and tensile ratios for the spun bundle are not obtained. Although this high ratio between spin speed and pull-off speed can only be achieved in the solidification zone ie. however, in a single step, it is also possible to achieve a desired total stretch ratio in two stages, namely a first stage or step with a stretch ratio of 5 to 150 followed by a second stage or step with a stretch ratio of approx. 1.1 to 30 or even more to produce the total value of the spin-to-pull ratio ratio from the solidification zone.

Since filaments made by the method of the invention do not require any secondary stretching or retention.

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In contrast to what is usual in the melt spinning of other organic filaments and dry spinning or wet spinning methods for preparing acrylonitrile polymer fibers, the filaments coming from the solidification zone can be collected directly or can be relaxed in a state where they can freely shrink, by any of the known methods of carrying out any such, e.g. by passing them over a heated feed roller to a wire feed roller which moves long-summers, or by passing them on a conveyor belt through an atmosphere of saturated water vapor under pressure.

For further and more detailed explanation of the invention and the advantages thereof, the following more detailed description and the examples which illustrate preferred embodiments of the drawings, wherein FIG. 1 shows a schematic illustration of a plant for carrying out the method according to the invention in the manufacture of filaments; and FIG. 2 shows a phase diagram of the system of FIG. 1 spun acrylonitrile polymer water system.

In FIG. 1, an extrusion apparatus 11 is provided generally provided with a spinning nozzle 12, at whose output end is a pressurized solidification chamber 13 adapted to receive the extrudate emerging from the spinning nozzle 12. The extrusion apparatus 11 is shown here as a piston extrusion apparatus. wherein a cylinder 15 is provided with a narrowly adapted piston 16 which can be moved by means not shown, forcing the contents of the cylinder 15 down through the spinning nozzle 12 and directly into the solidification chamber 13. With the cylinder 15, a single phase melt is heated. 17 to the desired temperature by means of heating elements not shown, such as vapor hoods or electric heaters mounted in the wall of the cylinder 15, 35 also provided with a thermometer 18 and a pressure gauge 14, which controls the temperature and pressure inside the extrusion apparatus. 11 relieves the melt / spin operation. Although the extruder 11 is shown here as a piston extruder, it is clear that other types of extruder such as worm extruders, gear pumps, etc., well known for melt spinning other organic polymers can be used.

At the exit of the extrusion apparatus 11 is mounted a spinning nozzle 12, which may be provided with circular 10 or elongated openings for spinning round or flat filaments. The extrudate emerging from the spinning nozzle 12 is shown here as filaments 21 which run directly into the pressure-drying chamber 13, from which the bundle is taken off and stretched under tension by a fast-rotating cylinder or wire feed roller 22 which provides the extremely high bundle draw ratios and speeds that are possible in the process of the invention. The pressure drying chamber 13 is provided with an inlet 24 through which steam and possibly air under pressure and at elevated temperature can be allowed access, as well as an outlet 25 from which liquid can be removed as required, and a thermometer 26 and a pressure gauge 27 for control. of the temperature and pressure inside the chamber 13. Furthermore, at its exit, the chamber 13 is provided with a pressure-tight closure 28, illustrated here 25 as a long thin slit which is only slightly larger than the diameter of the filament bundle 21 passing through the. Other pressure sealing means may be used, e.g. as illustrated in more detail in the description for e.g. U.S. Patent No. 2,708,843, No. 2,920,934, No. 2,932,183, No. 3,012,427, No.

30 3,027,740, No. 3,037,369, No. 3,046,773, No. 3,066,006, No.

No. 3,083,073, No. 3,118,154, No. 3,126,724, No. 3,127,151, and 3,152,379, which relate to the continuous relaxation of filaments of acrylonitrile polymers under superatmospheric water vapor pressure at elevated temperatures.

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From the cylinder or wire feed roller 22, which may be optionally disposed within the pressure chamber 13 or outside thereof as illustrated herein, the filaments 21 may be wound onto a yarn wrench 30 by means of a suitable winding means not shown here, or preferably the filaments 21 may be tensioned in a water vapor chamber 33 in which water vapor under superatmospheric pressure and elevated temperature is allowed to come into contact with the filaments 21 which are kept in a relaxed state where they can freely shrink. This is known in the art, and is further described in e.g. the above series of United States patents. In the water vapor chamber 33, the filaments 21 are fed through an inlet pressure seal not shown either, and by means of input rollers 35 they are conveyed on a conveyor belt 36, 15 through which they are passed through the water vapor chamber 33 to discharge rollers 37 which feed the relaxed filaments through a discharge pressure seal. also not shown, from the water vapor chamber 33 for winding on a yarn wrench 40 by means of a suitable winding means not shown as well.

It is well known to incorporate various additives into polymer melts prior to extrusion to modify the properties of the filaments made or improve their spinning ability. Such additives may be stabilizers such as light stabilizers, heat stabilizers, antioxidants, gas phase stabilizers, ultraviolet light stabilizers, etc., pigments, dyes, brightening or brightening agents, flame retardants, antibacterial agents, antifouling agents, or reducing or enhancing change, antistatic agents, materials for imparting spinning mass active sites for attaching or bonding dyes, porosity inducing agents, fibrillation enhancers, antifouling agents, fillers, reinforcing agents,

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In the practice of the present invention, smaller amounts (e.g., up to about 25%) of such materials may incorporate into the single-phase melt prior to melt spinning, provided that (a) have particle sizes small enough to allow them to pass freely through the extrusion openings, or (b) have melting points near or below the minimum fusion temperature (M) of the polymer in the presence of melt-promoting agent or soluble in the melt. Among such additives are polymers such as polyvinyl alcohol, polyvinyl chloride, polyacrylamide, polyacrylic acid, polyalkylene glycol ether, etc. These polymers can have molecular weights ranging from approx. 1000 to approx. 100,000. Other additives which may be used herein include haloalkyl sulfate 15 as a flame retardant, titanium dioxide as pigment, cationic dyes, anionic dyes, dispersant dyes, silica, aliphatic or aromatic halogen compounds, organic phosphorus compounds, antimony oxides, etc. skilled in the art. These additives do not normally affect the single-phase melting region of the phase diagram; however, if used, the phase diagram should be re-determined while present so as to ensure the boundaries of the area actually used in melt spinning. Optionally, the process sequence as described above may include additional steps such as a secondary stretch or post stretch, ripple, retraction, washing, treatment with antistatic agents, antifouling agents, fire retardants, adhesive inhibitors, lubricants, etc., staining, treatment with crosslinking agents, stacking and the like. for making known modifications. Some of such additional steps may, if desired, be performed within the same physical structure as the solidification zone; but under ambient conditions that are outside those required in the solidification zone. Illustrative of such additional steps, which may be accomplished within the solidification zone, may e.g. be secondary stretching or post stretching, relaxation, re-stretching, printing dyeing, drying, etc. Usually, but not necessarily, such additional steps will be performed under increased pressure.

Multiple single-phase melts can be extruded at the same time through the spinning nozzle to produce multi-component fibers spun sideways, core and sheath fibers or randomly constructed fibers, bicomponent fibers, tricomponent fibers or multicomponent fibers, all using known apparatus for such purposes. The single phase melts used for this purpose may be the same polymer or similar acrylonitrile polymer. The melts may contain incompatible components to form split fibers, or they may remain permanently bonded. In addition, hollow fibers, but of solid wall, can be made by extrusion of a jacket from single-phase melt around a gaseous core. In all these alternative embodiments, the extrusion takes place directly into a solidification zone 20 with the above defined conditions of temperature, pressure and composition.

The process according to the invention and the associated additional advantages will be more clearly understood by reviewing the following illustrative examples showing some preferred embodiments. All percentages and percentages are by weight, unless otherwise stated.

Example 1 First, a phase diagram is determined for locating the 30 single-phase melting region. Next, melt spinning of acrylonitrile polymer is performed by the process of the invention, and by comparison, what happens when going outside the scope of the present invention.

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Determination of phase diagram

The FIG. 2 illustrates the phase diagram of an acrylonitrile polymer / water system in which the acrylonitrile polymer is a polymer of 89.3% acrylonitrile and 10.7% methyl methacrylate 5 having a molecular weight of approx. 58,000, is determined by the following series of tests.

A crisp sample of 1 g of the acrylonitrile polymer is placed in an aluminum dish and autoclaved in saturated water vapor at 135 ° C for 5 minutes. Samples are taken and cooled.

The polymer lightly crumbles into powder, has a dull or sad appearance and when viewed under a microscope no fused particles are observed. The process is repeated at 140 ° C and 145 ° C with practically the same result. The process is repeated again at 150 ° C. This time the sample will not crumble, it looks completely fused and has a shiny glossy surface. Under a microscope, this sample has a continuous surface and no individual particles are observed. The process is repeated again at 155 ° C, 160 ° C and 165 ° C, with no visible change from the appearance known in the 150 ° C sample, except for a slightly increased yellow in the polymer. The line AE of FIG. 2 is therefore determined to be at 150 ° C.

A polymer / water mixture of 40% polymer and 60% water is prepared. The mixture is placed in a sealed cell as described above and heated in an oil bath to 150 ° C for 10 minutes. The test is observed through the window as being made up of two stages.

The sample is cooled and taken from the cell. The two phases are found to be fused polymer and free water. This procedure is repeated for mixtures of polymer and water consisting of 60%, 70%, 75% respectively. 80% polymer, the remainder being water. In each case, two phases are observed. When the sample is repeated again, but now using a mixture of 85% polymer and only 15% water, only one phase can be detected at 150 ° C, and after cooling and removal.

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of the sample, only partial fusion of the polymer is observed, even though only one phase is detected. This sample is repeated again, but now using a polymer sample containing 82% polymer and 18% water. When heated to 5 to 150 ° C, only one phase is observed. Upon cooling and examination, it appears that the polymer has undergone complete fusion or fusion. The point A in FIG. 2 is therefore found to be located at approx. 18% water and 82% polymer at a temperature of 150 ° C. Of course, there may be a small range of perhaps 17% to 19% water at 150 ° C, which collectively represents the "point" A. In no case, however, as little as 15% or as much as 20% water has been found to apply to this particular polymer at 150 ° C to obtain the desired single phase fusion.

After the minimum melting point of the single phase melt has thus been ascertained as the above point A, it is then necessary to ascertain the phase boundary lines ABF and ACG in FIG. 2nd

Sufficient water is added to the crisp 20 polymer powder to form a mixture of 88% polymer and 12% water. This sample is placed in the sealed cell and heated to 150 ° C. Hereby no merger and / or no phase separation is found. In separate tests, the sample is heated to 155 ° C, 160 ° C, 25 165 ° C and 170 ° C. There is an increasing tendency for the sample to partially fuse with increasing temperature. However, complete fusion is not detected until the sample is heated to 170 ° C. In all cases, only one phase is observed. This series of tests locates a point on the 30 line ABF at 12% water and 88% polymer located at a temperature of 170 ° C.

Additional points on the line ABF in FIG. 2 can be determined similarly using other compositions such as 85% polymer and 15% water.

35 0 20 147767

The same procedure is repeated using a polymer blend of 75% polymer and 25% water. Two phases are observed at 150 ° C. In the separate tests, the sample is heated to 155 ° C, 160 ° C, 165 ° C, 170 ° C, 175 ° C and 180 ° C. In all cases, two phases are observed. In each case, the polymer is fused and in each case the layer of excess free water is found. The procedure is repeated by heating the sample to a temperature of 185 ° C. As the polymer is fused, only one phase is observed, and no excess free water can be detected. After cooling and examination, the sample is found to be completely fused and no water is found in the sample cell. A point on the line ACG is therefore determined as located at 25% water and 75% polymer and a temperature of 185 ° C. Additional points on the line ACG in FIG. 2 can be determined similarly using other compositions such as 22% water and 78% polymer.

Melt Spinning 20 After the phase diagram is determined for mixtures of this polymer with water as shown in FIG. 2, the following experimental melt spins are made using an apparatus substantially as schematically illustrated in FIG. 1: 25 To 15 g of dry polymer is added 3.3 g of water to provide an acrylonitrile polymer-water mixture containing 18% water. The mixture is sealed in a jar and mixed on a rolling mill for 30 minutes to ensure complete mixing. This mixture is then placed in a piston extrusion apparatus 11 equipped with a single orifice spin nozzle 12 having a diameter of 0.40 mm and an orifice length of 3.25 mm. The orifice opening is temporarily sealed to prevent premature moisture loss during commissioning. The extrusion apparatus 11 and the spinning nozzle 12 are heated to 154 ° C under sufficient pressure to prevent

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21 147767 water evaporation. The opening of the spinning nozzle is opened and a force of 56 kg per m. cm is applied by means of the plunger 16 to extrude a filament. In a first test conducted for comparative purposes, the pressure-drying chamber 13 is left open to the atmosphere, so that the filaments 21 are extruded into a range of ambient temperature and pressure. The pressure on piston 16 is adjusted such that the flow rate of the single-phase fusion melt through the orifice of the spinning nozzle is 0.846 m / s. minute. The resulting filaments are received directly on the yarn wrench or winder 30 (without using the feed roller 22) on a rotary reel apparatus. After start-up, the spin speed of the rewinding apparatus gradually increases until a maximum determined by continued filament rupture is reached. The 15 maximum deceleration velocity thus obtained is 1.16 m per second. per minute for a spin-to-take-off or bundle draw ratio of 1.16 / 0.846 2.6x (i.e.

Bundle strength of 260%). .

In another experiment representing the method of the invention, the pressure-drying chamber 13 is sealed and saturated water vapor is introduced through the inlet 24 until a pressure of 2.67 ato corresponding to a temperature of 140 ° C is achieved. This temperature is approx. 14 ° C lower than the temperature of the single-phase fusion melt in the extruder and approx. 10 ° lower than the minimum melting temperature of 150 ° C for this melt. Under these conditions, which is otherwise a repetition of the first attempt, a maximum removal rate of 38 m per head is obtained. per minute for a spin / take off ratio or a bundle draw ratio of 30 85x (ie 8500% bundle stretch). An amount of fiber thus produced is collected with one denier per filament of 15, and the fiber is subjected to saturated water vapor at a pressure of 127 ° C in autoclave and relaxed state which allows free shrinkage. The denier of the fiber is thereby increased to 19.5, which is 35

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22 147767 ket indicates that a shrinkage of approx. 23% have occurred.

The physical properties of this relaxed fiber are as follows:

Rectangular tensile strength 3.5 g / denier

Rectangular elongation at break 43.0% 5 Loop tensile strength 1.98 g / denier Loop break elongation 19.0%

Starting module 58.0 g / denier

Example 2 This example illustrates the application of the present invention to melt spinning of finer denier acrylonitrile polymer filaments than in Example 1.

The second experiment in Example 1 is repeated except that the flow rate of single phase fusion 15 melting through the orifice or opening of the spinning nozzle is 0.792 m / s. and the pressure of the saturated water vapor in the solidification chamber 13 is increased to 3.45 ato corresponding to a temperature of 147 ° C. This temperature is approx. 7 ° C below the temperature of the extruder and approx. 3 ° C below the single-phase fusion melt's minimum melting temperature at 150 ° C

for this composition. Under these conditions, the maximum take-off speed or winding speed is 89 m per second. per minute for a spin / take off ratio or a bundle draw ratio of 112x (ie 11,200% * s bundle distance). The denier of the resulting filaments is 6.4, thus illustrating that a larger denier range is achievable by means of a single size spinning nozzle opening.

In the process of the invention, using different sizes of the spinneret orifices 30, acrylonitrile polymer fibers with denier can be prepared at least between 0.5 and 80 or, if desired, even higher.

Comparative Example A

The first experiment of Example 1 is repeated except that a heat strip is installed along the solidification strip.

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23 to the full length thereof. As the chamber 13 is deaerated to the atmosphere and the heat strip is adjusted to provide an air temperature in the chamber 13 of 150 ° C, which closely mimics the conditions used in conventional melt spinning of other organic fibers to achieve high spin removal or high bonding ratios. , there is obtained a filament-like material that appears to be completely filled with bubbles to resemble a long foam strip. The 10 maximum bottom draw ratio obtained hereby is no higher than in the first experiment of Example 1 (no heat, no water vapor under pressure) and it is frequently necessary to lower the extraction rate due to breakage of this highly disparate material. This demonstrates that elevated temperature without the use of pressurized melt-promoting environment is not capable of providing the extremely high bundle tensile ratios which can be adhered to by the method of the invention, but instead produces a degraded or at least greatly degraded 20 product.

Comparative Example B

The second experiment in Example 1 is repeated except that nitrogen is used below ambient temperature 25 instead of water vapor in pressure chamber 13. As the nitrogen pressure is increased to 3.94 ato, maintaining a linear rate of the single phase melt through the orifice nozzle of 0.634 m per per minute, the maximum winding speed of the uniform filaments produced, thereby obtainable, is 2.9 m per minute. minute, ie a spin / pull ratio or a bundle draw ratio of 4.6x (i.e., a bundle draw ratio of 460%), which is only slightly higher than the bundle draw ratio obtained at ambient temperature and tensile pressure (first attempt in Example 1), but as in nothing cases approach the extremely high bundles-

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Tensile ratios obtained by the method of the invention (second experiment in Example 1 and Example 2). This demonstrates that increased pressure and elevated temperature in inert atmosphere are not capable of providing the extremely high bundle tension ratios that the present invention enables.

Comparative Example C

Example B is repeated using the strip heater described in Example 10 to heat the nitrogen at various temperatures under a pressure of 3.94 ato. As the temperature of the nitrogen environment is increased to 140 ° C, the maximum spin-off ratio thus obtained is raised from approx. 4.6 to 15 approx. 10.1 (a bundle tensile ratio of 1010%) without the formation of bubbles as in Example A. Continued heating to 150 ° C does not result in any increase in the achievable spin / decay ratio. Heating to above 150 ° C causes filament melting, resulting in fiber discontinuities and fractures. This demonstrates that elevated temperature as well as elevated temperature without the aid of the melt environment, although these measures provide some improvement in the melt / decay ratio, are still unable to provide the extremely high bundle tensile ratios attainable according to the present invention. The present invention.

Comparative Example D

For 15 g of dry polymer made up of 89.3% acrylonitrile and 10.7% methyl methacrylate having a molecular weight of approx. 58,000 are added 3.3 g of water to provide an acrylonitrile polymer / water mixture containing 18% water. The mixture is sealed in a jar and mixed on a rolling mill for 30 minutes to ensure complete mixing. The mixture thus treated is then placed in a piston extrusion apparatus which at its exit end is pre-molded.

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25 147767 the sight with a spinning nozzle having a single aperture with a diameter of 0.40 mm and an orifice length of 3.25 mm. The orifice opening is temporarily sealed to prevent moisture loss prematurely during commissioning. The extrusion apparatus and the spinning nozzle are heated to 154 ° C under sufficient pressure to prevent water evaporation, thereby converting the acrylonitrile polymer / water mixture into a single phase fusion fusion. The opening of the spinning nozzle is opened and the plunger is actuated to apply a pressure of 56 kg / cm by means of the plunger to extrude a filament through the opening. The pressure on the piston is then adjusted so that the flow of single phase fusion melt through the orifice of the spinning nozzle becomes 0.446 m / s. minute. The resulting filaments pass through and cool in ambient air from the spinning nozzle to the yarn winding apparatus and are collected on a yarn wrench having a bottom stretch of slightly below the maximum achievable bottom tension ratio of approx. 2.6 and allowed to dry at room temperature. These filaments are opaque, white and have strong luster. Upon microscopic examination, they are found to contain many voids and microwaves.

Example 3

The procedure of Comparative Example C is repeated except that the newly formed filaments extruded through the orifice of the spinning nozzle enter directly into a pressure chamber containing water vapor at a pressure of 2.67 ato and a temperature of 140 ° C. The resultant filaments are collected after passing through the water vapor pressure zone 30 on a yarn winding on a yarn winding apparatus at a bundle draw ratio which is slightly below the maximum obtainable bundle draw ratio of approx. 85x. These filaments are then relaxed in a state that allows free shrinkage in autoclave in water vapor under a pressure of 127 ° C. These filaments are also opaque, white and of high gloss. By

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26 147767 microscopic examination they found to contain many voids and micro voids. However, they have physical properties that make them acceptable for use as textile fibers.

Comparative Example E

The filaments of Comparative Example D are dried under ambient conditions and then heated in an oven in an attempt to make the voids and microspheres disappear. There is no change in their appearance.

10 Relaxation in water vapor under pressure at 127 ° C after heating in the furnace also does not change the appearance of these filaments.

Example 4 The procedure of Example 3 is repeated except that the filaments pass directly as they leave the water vapor pressure chamber through another pressure chamber containing air or nitrogen at 2.67 ato and 140 ° C, where they are dried, and according to the present invention -20 voids and micro voids free are transparent and exhibit similar change to commercially available acrylic fibers. This illustrates drying of the freshly spun acrylonitrile polymer while still warm from the spinning, prior to cooling to below ca. 90 ° C is allowed.

Example 5 In the present example, the method of Comparative Example B is modified to produce fibers having a ripple which is stable to textile processing. Inside the pressure chamber containing water vapor at a pressure of 2.67 ato and a temperature of 140 ° C, there is now placed a first set of thread feed rollers which serve to stretch the newly formed filaments emerging from the orifices of the spinning nozzle. a beam tension ratio of approx. 75x. Another set of wire feed rollers rotating at lower speeds serves to relax the filaments. From the second set of wire feed rollers, the filaments are fed to a crimping apparatus with 5 tuning box serving as pressure sealing in a wall of the pressure chamber. Inside the crusher's crate box, the rippled filaments are quenched with cold water. After the filaments have emerged from the crusher, they are stored wet until dried in an oven at 110 ° C. The filaments thus produced by the process of the invention are transparent, void-free and micro-void-free, and exhibit rapid change.

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28 147767

Comparison with technique known from LU patent specification no.

66,301 Examples 8 and 10.

A mixture of a copolymer of acrylonitrile / methyl-acrylate / sodium styrene sulfonate in the ratio 93.63 / 6 / 0.37 5 having a viscosity of 1.0 and water (100/25 by weight) is prepared by spraying the finely ground copolymer with water of an open tray and place the mixture in a container which is sealed and shaken for 12 hours. Thereby, an apparently dry powder is obtained, which is fed to a bipolar 10 extruder with 5 zones for sequential feeding, melting and extrusion, the highest temperature being 177 ° C and 2 the molten mass at a pressure of 49 kg / cm. multi-hole spinning nozzle with 39 holes measuring 0.25 mm in length and 0.18 mm in diameter and held at 175 ° C.

The filaments emerging from the spinning nozzle are passed through a spinning chamber with a mixture of air and water vapor at a pressure of 1.4 kg / cm 2 and a temperature of 64 ° C, thereby forming a yarn which is directly collected on a coil at a speed of 68 m / min. In a subsequent independent stretching step, the yarn is unwound from the bobbin and passed 2 through a saturated water vapor tube at a pressure of 1.4 kg / cm under a stretch of 6 times its length in a freshly spun condition, wound up at a rate of 137 m / min. The yarn is then boiled with water. Its filament tensile strength is 3.0 g / denier, its elongation at break is 20%, and its modulus is 68 mg / denier. The denier value of the filament is 11.8. By microscopic examination of a filament cross section, it is found that the filament is constructed with a sheath / spoon, the thickness of the spoon being 28% of the radius of the filament, while the remainder is the core containing a large number of cavities. The mean density of the filament is 1.083 g / cm.

Upon microscopic examination of the filament surface, deep longitudinal stripes are found. When tested in a dye bath (40 second immersion at a bath temperature of 82 ° C), clear effect is observed, the filament core differs sharply from the vagina by staining clearly darker.

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29 147767

At a magnification of approx. 16,000 times a series of cavities with a diameter of approx. 0.2 µm, and in the electron scanning microscope a maximum strip length of approx. 260; am and a minimum strip length of approx. 40; rm, with the average stripe depth determined by optical photomicroscopy being approx. 1.3, um corresponding to approx. 6% of filament radius.

The above procedure is repeated except that the air / water vapor chamber is now kept at 140 ° C. Here, too, stretching is performed 6 times in a separate step, whereby 10 are obtained yarns whose filaments have a denier of 9.88. Again, the same core / sheath structure is found with a maximum strip length of approx. 200 µm and a minimum strip length of approx. 30 pm. The longitudinal cavities in the core measure approx. 280; about and the shortest approx. 12; im.

15 It is apparent from the disclosures in LU Patent Specification No. 66,301 Examples 8 and 10 that regardless of whether this known method of spinning a water / acrylonitrile copolymer mixture with removal through an air / vapor chamber is carried out at 64 ° C or At 140 ° C, 20 micro-cavities occur at the core-sheath boundary, and at the subsequent separate stretching step (of the order of 4-6 times), clear streaking is desired, which is precisely desired according to the above-mentioned LU patent for the manufacture of power yarns.