FI57792C - FRAME STATION FOR ACRYLIC NITRILE POLYMER GENETIC STRAENGPRESSING - Google Patents

Description

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Patent raeddelat (51) Kv.ik.3 / int.a.3 D 01 D 5/096 P88 / T1 »FINLAND —FINLAND (21) N * wmlt» lwmu.-F * wn «i * ej« nln * ( 22) HakmntapUvi - AMeknlngadag 01.02. lh (23) Primary Cloud — GIMgh «txU« 01.02-71 * (41) Tullut JulklMkd - ftlMtcfr «ntll | 06.08 to 7 ^

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Patent · och registerstyrelsan 'Arastan utlajd och utl.ikrHUn publicund 30. uo. συ ^ (32) (33) (31) Pyy ** · »/« toikuu * —B * ftrd pciont · * 05.02.73 02.03.73, 23.03.73, 10.0U.73, 05-07.73 USA (US) 329U79, 337506, 3UUU63, 3U9877, 376778 Proven-Styrkt (71) American Cyanamid Company, Wayne, New Jersey, USA (72) Harold Porosoff, Stamford, Connecticut, USA (7U) Oy Kolster Ab (5U) ) Method for the extrusion of finished acrylonitrile polymer fibers by extrusion - Förfarande for framställning av acrylonitrilepolymerfib-rer genom strängpressning

The present invention relates to a process for the production of acrylonitrile polymer fibers by extrusion so as to obtain products with different properties. In particular, this invention relates to an economical process for extruding a single-phase, water-fused acrylonitrile polymer melt into a solidification zone in which certain conditions are maintained to maximize burst elongation.

In general, shaped articles such as man-made fibers, filaments, films, etc., can be made from polymeric materials by melt-spinning, dry-spinning, or wet-spinning methods. In the "melt spinning method" to form artificial filaments, by melting, the liquefied polymer is extruded through holes or slits in the spinning nozzle to form an extrudate that coagulates upon cooling. Typically, polyamide, polyester and polyolefin fibers or films are made by melt spinning. In the "dry spinning method" to make artificial fibers, a polymer liquefied by dissolving in a volatile solvent is extruded through the holes of the spinning die 2,57792 to form an extrudate which is coagulated by evaporating the volatile solvent. Typically, cellulose acetate solutions in acetone, acrylonitrile polymer solutions in dimethylformamide, etc. are spun into fibers by dry spinning. In the "wet spinning method", to form artificial fibers, a polymer liquefied by dissolving in a solvent is extruded through holes or slits in a spinning nozzle to form a burst that is coagulated by removing the solvent in a liquid coagulating medium. When wet spinning the fibers of some polymers, such as solutions of acrylonitrile polymers in aqueous nitric acid, aqueous salt, or organic solvents, the solvent is removed by extracting it from the bite into an aqueous coagulant. In wet spinning of fibers or films from other polymers such as viscose (aqueous sodium hydroxide solution of cellulose xanthate), the solvent is removed by chemical reaction with an aqueous sulfuric acid coagulant.

For various reasons, it has been concluded that melt spinning methods are more advantageous than dry spinning or wet spinning methods whenever a choice is possible. Some of the reasons for this preference are (a) increased speed of the work process when cooling rather than solvent diffusion (evaporation or extraction) acts as a solidification mechanism, and (b) very high cross-sectional reduction ratios in spinning or achievable burst expansions large spinneret bearings required to avoid excessive extrusion support pressures when spinning a highly viscous polymer melt. Other reasons for prioritizing melt spinning methods are to avoid the need to wash the product free of residual solvent and to avoid solvent recovery from coagulation solutions or gases. However, because acrylonitrile polymers do not readily melt without molecular chain breakage, melt spinning methods have not been available for spinning acrylonitrile polymers, and the main focus has been on wet spinning and dry spinning methods to spin such polymers.

Hours of the desirability of melt-spinning methods have been attempted to find ways to liquefy acrylonitrile polymers so that they could be extruded and then solidified by cooling alone. Such Vale melt-spinning processes have used bound or partial solvents that could be used in conjunction with acrylonitrile polymers to form liquids at elevated temperatures, which liquids can solidify, after extrusion, by cooling alone. However, such products still had to be washed free of latent or partial solvent and solvent recovery systems were still required 3,57792, after which such Vale melt spinning methods still do not have all the advantages and desired properties of real melt spinning methods.

The acrylonitrile polymer can be formed into a single phase melt with a melting aid.

A melting aid is a substance which, when used at a pressure which prevents boiling at temperatures above its boiling point at normal pressure, is capable of lowering the melting point of an acrylonitrile polymer to a temperature lower than the cleavage temperature of the acrylonitrile polymer chain. Melting aids do not include substances normally considered as solvents for acrylonitrile polymers, such as dimethylformamide, dimethylacetamide, ethylene or propylene carbonate, dimethylsulfoxy, dimethylsulphonate, or highly concentrated aqueous solutions of lithium bromide, iodide salts, alkali metal perchlorates, etc., or other solvents such as those mentioned in U.S. Patent Nos. 2 lfco 921, 2 356 767, 2 fcoU 713-728, 2 6U8 6U8-9.

Based on a certain theoretical consideration, it has been found that substances are useful as melting aids. According to this theory, melting aids can be selected on the basis of certain thermodynamic properties, namely the solubility parameter, the strength of the hydrogen bond and the dipole moment. The solubility parameter of the substance, defined as the square root of the cohesion energy density, is preferably greater than about 8.7 for the acrylonitrile polymer melting aid. The density of cohesive energy is the bound heat of evaporation in calories per mole divided by the molar volume, or alternatively it is the bound heat of evaporation in calories per gram of the specific gravity of the liquid. The hydrogen bond strength for the acrylonitrile polymer melting aid is greater than 0 and preferably greater than about U. If the solubility parameter is closer to lower values, such as about 8.7 to about 11, then the hydrogen bond strength is preferably higher, i.e., greater than about 12. Dipole moment for acrylonitrile polymer for the thawing aid is greater than 0. Water is the only truly inexpensive thawing aid because it does not require the thawing aid to be washed out of the product and no recovery system is required.

Of the invention for the preparation of the method akryylinitriilipolymeerikuitujen the extrudate enamel is characterized in that the extruded product is cooled höyrynpainevyöhykkeessä molten state be stretched plastic state to the atmospheric pressure exceeding the vapor pressure of the pressure zone is maintained such that the water contained in the plastic extruded product evaporates substantially at the same rate as water diffuses inside the extruded product to the pinanlle and the extruded product surface zone remains moist, with minimal shell formation, and the extruded product is stretched in this plastic stretchable state while in the vapor pressure zone at a stretch ratio of 25-250.

According to a preferred embodiment of the present invention, the fibers are dried. o ...

at temperatures above 90 ° C, while essentially preventing water loss from the newly melt-spun fibers at all temperatures below 90 ° C prior to the drying step, thereby reducing the tendency to form cavities and microcavities in the fibers.

When melt-spinning organic polymers such as polyamides, polyesters and polyolefins and when wet-spinning or dry-spinning acrylonitrile polymers, filaments must be good fiber properties develop. Surprisingly and unexpectedly, the filaments spun by the process of the invention did not require a second stretching or post-drawing process step. Thus, the characteristic good fiber properties of acrylonitrile polymer fibers can be obtained by the method of the present invention simply by loosening such strands at an elevated temperature after extrusion stretching without the use of a second stretching or post-drawing step.

Acrylonitrile polymers that can be used in the process of the invention are polymers or blends of polymers that contain more than about 50% combined acrylonitrile. In addition to homopolyacrylonitrile, copolymers of acrylonitrile with one or more copolymerizable monoolefin monomers can be used. Such monomers include acrylic, alpha-chloroacrylic and methacrylic acids, methacrylates such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, methoxymethyl methacrylate, beta-chloroethyl methacrylate and the corresponding acrylic and alpha-chloroacrylic acrylates; vinyl bromide, vinyl chloride, vinyl fluoride, vinylidene bromide, vinylidene chloride, allyl chloride, 1-chloro-1-bromoethylene; methacrylonitrile; allyl alcohol; acrylamide and methacrylamide; alpha-chloroacrylamide or its mono-alkyl-substituted products: methyl vinyl ketone; vinyl carboxylates such as vinyl formate, vinyl acetate, vinyl chloroacetate, vinyl propionate, vinyl stearate and vinyl benzoate; N-vinyl imides such as N-vinylphthalimide and N-vinylsuccinimide; methylene-malonic acid esters; itaconic acid and itaconic acid esters; N-vi-carbazole; vinylfuran; alkyl vinyl ethers; vinylsulfonic acids such as vinylsulfonic acid, styrenesulfonic acid, methallylsulfonic acid, p-methallyloxybenzenesulfonic acid and their salts; ethylene alpha, beta-dicarboxylic acids or their anhydrides or derivatives such as diethyl citraconate, diethyl mesaconate; styrene, dibromostyrene; vinylnaphthalene; vinyl-substituted tertiary heterocyclic amines such as vinylpyridines and alkyl-substituted vinylpyridines, e.g., 2-vinylpyridine, U-vinylpyridine, 2-methyl-5-vinylpyridine, and the like; 1-vinylimidiazole and alkyl-substituted 5,57792 1-vinylimidiazoles such as 2-, U- or 5-methyl-1-vinylimidiazole, vinylpyrrolidone, vinylpiperidone and other copolymerizable monomer substances of monoolefins. Acrylonitrile polymers or polymer blends may contain varying amounts of one or more mixed monomers, such as a total of about 5, 10, 15, 20, 25, 30, or 10% mixed monomers based on the total acrylonitrile polymer combination, and may range in molecular weight from 10,000 200,000: when, for example, about 20,000; UOOOO; 50000; 60000; 70000; 85000; 100000; 130,000, etc. The amount and molecular weights of the mixed monomer may vary outside these ranges shown, as the performance of the present invention does not depend on these properties, although consideration of the properties of the products for their end use may show such variations.

Breaking of the molecular chain of the acrylonitrile polymer, which usually manifests itself.

goes as color fading occurs upon bringing the polymer to about To0-220 for the time normally required to liquefy and extrude the polymer. When the quality of the polymer in the product is not critical and some molecular chain cleavage is allowed, the single phase blend melt can be heated to higher temperatures, but it is generally preferred to work at lower temperatures to prevent molecular chain breakage.

The acrylonitrile polymer fibers are preferably as free of cavities and microcavities as possible, since the cavity-free fibers have better tensile strength and wear properties and better colorability. An advantage of the process of the invention is that acrylonitrile polymer fibers do not substantially form cavities or microcavities.

As mentioned above, a single phase acrylonitrile-water blend melt suitable for melt spinning contains from about 10% to about 35% water, depending on the composition of the acrylonitrile polymer and other variables. In the melt spinning process, the material from which the fibers are formed as it passes through the holes in the spinneret therefore contains about 10 to about 35% water · At some point during further processing, either immediately or later, this water must be evaporated to obtain dry acrylic trilymer fibers such as in the final product. , blankets, carpets, etc. "dry" fibers, as the term is used herein, are those that contain about the equilibrium moisture gain that they take upon exposure to environmental conditions or less moisture. For acrylonitrile-li-polymer fibers, this means that the dry fibers contain less than 5 56 hygroscopic moisture. It has been found that the formation of microcavities occurred during improper drying of the fibers.

When the resulting fibers were allowed to cool and partially or completely dry at moderate or low temperatures, this improper drying resulted in the formation of cavities and microcavities. Proper drying to reduce or prevent this requires that the resulting fibers be prevented from losing water before they are dried at an elevated temperature, i.e., above about 90 ° C.

One type of process combination, combined with suitable drying, involves drying the resulting fibers after leaving a hot, pressurized, vapor-containing solidification zone, passing them directly into and through a heated chamber where they dry in an environment maintained above about 100 ° C, and which may contains air with a temperature and pressure approximately equal to that of the steam in the solidification zone.

Another type of process sequence, combined with suitable drying, involves keeping the resulting fibers wet. Even if they are cooled to below about 90 ° C, until they are dried at an elevated temperature, i.e. above about 90 ° C. Illustrative of this series of processes is that the resulting fibers, after leaving the hot pressurized solidification zone, are cooled in a water bath and then reheated while still wet in a dryer operating above about 90 ° to dry the fibers. If the resulting fibers in this process series curl while still wet, before the preheating-drying step, the resulting curl can be very permanent, withstanding the curl without losing the textile carding process, etc., and even upon contact with hot water, such as in a dye bath.

A surprising phenomenon was observed during testing of this type of second process sequence. When the resulting fibers left the spinning nozzle and cooled to room temperature, the fiber turned white and opaque due to the formation of cavities and microcavities therein. When these white 57792 τ opaque fibers were heated on a hot plate at about 120 ° C, they became translucent due to redissolution of water in the polymer, causing the cavities and microcavities to disappear. When these translucent fibers were cooled to room temperature immediately after they became translucent, an opaque white appearance reappeared due to "precipitation" of water from the polymer to re-form the cavities and microcavities. This phenomenon can be repeated several times for heating / cooling. But once the fiber has lost enough water at an elevated temperature to dry, cooling the fiber results in a still translucent fiber that is free of cavities and micro-onte ---- parasites.

To find suitable conditions for a specific acrylonitrile polymer to prepare a single phase blend melt comprising mainly acrylonitrile polymer and water, a mixture of acrylonitrile polymer and water is prepared and heated under pressure to a temperature sufficient to cause the polymer to melt. If a single-phase mixed melt is prepared, the minimum temperature that causes fusion (temperature M) is taken into account. More detailed instructions on how to prepare a single-phase alloy melt are given in the following description of the determination of the phase diagram, which refers to Figure 2 of the accompanying drawings.

Determining the Phase Diagram In the practice of this invention, it is necessary to first determine the phase diagram to obtain the conditions required for the specific acrylonitrile polymer to be spun for extruding the "single phase blend melt" of the polymer. Referring to Figure 2, point A is first located, then the lines ABF and ACG are determined, after which the preferred portion ABC is determined to locate the conditions under which the improved shaped articles can be extruded.

To determine point A, a series of polymer samples are exposed to saturated steam in an autoclave for 5 minutes each. Each sample is treated at ascending temperatures. The melting point of the polymer in the saturated steam is the minimum temperature at which flow has occurred. The surface of the molten polymer appears glassy and the polymer particles are firmly bound together. This minimum temperature is the basis for the DAE line in Figure 2.

Once the melting line DAE is known, the minimum amount of water required for melting at this temperature is determined. This minimum water content and temperature is point A. At this point, all water is hydrogen bonded to the acrylonitrile polymer and free water as the second phase does not exist. A polymer sample, 8 57792 mixed with a known amount of water, is placed in a steel cell equipped with a glass window. The cell is closed to retain the pressure that develops as a result of the test. The cell is heated in an oil bath so that the sample can be monitored at all times. In separate tests, samples containing different water / polymer ratios are placed in a cell and heated to the temperature indicated by the DAE line. When excess water is present, two phases appear as the polymer melts. Samples with continuously progressing water concentrations are tested until a sample is obtained in which only one phase is visible, representing point A at this concentration. By further reducing the water / polymer ratio, melting does not occur at a temperature along the DAE line.

To determine the phase fusion range, it is necessary to determine the lines ABF and ACG as in Figure 2. This is done by placing polymer samples in a steel cell with a water content in one case about 5-10% more water than at concentration point A. Line ABF is determined by locating a point representing temperature and concentration the mixture of polymer and water with a smaller amount of water melts into one phase. The line ACG is obtained by locating the point where a biphasic mixture of polymer and water with a higher amount of water becomes single-phase after passing through a biphasic liquid state. Because physical mixing is difficult to achieve in a closed cell, obtaining this latter point may be time consuming.

After locating point A and lines ABF and ACG, draw line BC at a temperature about 30 ° C higher than point A. Thus, a preferred portion of the ABC single phase alloy melt zone is defined.

Generally, single phase blend melt combinations are located in the range of about 10 to about 35 # of water, corresponding to about 90-65% acrylonitrile polymer. If the single phase melt composition range for a particular acrylonitrile polymer / water extends over a wide range of combinations with useful low melting points (namely, below the polymer chain break temperature range), it is preferred to select a composition from the side of such a combination in accordance with the present invention. , where water volumes are lower.

Sometimes the amount of water can vary outside this range and still form a single phase mixture melt. More water can be used, e.g., by adding a third substance (such as a water-soluble polymer; a water-soluble polymer that forms a melt with water; a finely divided water-soluble solid; or a water-soluble liquid) that binds excess water, leaving the acrylonitrile polymer as a single-phase blend melt. This third substance must not significantly interfere with the formation of 9,57792 single-phase mixed melt with water. This third substance may be compatible with the acrylonitrile polymer and the finished products may be a homogeneous mixture or may contain the third substance as a permanent enclosure. The third substance may be incompatible, making the products easily fibrillable. This third substance can be easily removed, such as by washing with water or an organic liquid, leaving a porous structure. Such third substances include hygroscopic or water-soluble polymers such as polyvinyl alcohol, polyethylene glycol, polyacrylic oxide and its derivatives, polyacrylic acid, polyvinylpyrrolidone, polyelectrolytes, polyelectrolyte, proteins such as gelatin, casein, and fines. diatoms, kaolin clays and molecular sieves, and other water-binding agents such as anhydrides, such as acetic anhydride, and inorganic salts, such as anhydrous sodium sulfate, calcium chloride, sodium phosphate, and the like.

According to the present invention, a single-phase mixture of acrylonitrile polymer and water is extruded at a temperature (T 1) higher than its minimum melting temperature (M) but preferably not more than 30 ° C above this temperature, through a spinning die directly pressurized to solidification. the pressure, temperature, and combination conditions maintained therein. The conditions in the solidification zone that allow very large burst stretches are such that the composition profile in the resulting burst cross section remains relatively flat as it moves away from the spinneret surface, the relatively high concentration of melting aid remains in the resulting burst, 20 ° C die minimum melting temperature M. By "composition profile ... remains relatively constant" is meant that the concentration of acrylonitrile polymer near the surface of the resulting burst and the concentration of acrylonitrile polymer in the deep burst are approximately 10% and preferably not more than " not more than 5% difference in polymer concentration) in each simple cross-section of the resulting burr. As the cross-section of the resulting burr moves away from the spinneret during the cross-section reduction step during stretching in the solidification zone, the water content may of course change, but at least 70% of the water content of the single-phase mixed melt is present. In order to obtain these burst conditions in the pressurized solidification zone, the ambient conditions therein are preferably monitored and monitored. The absolute partial pressure of water vapor and preferably has 56-110% and even more preferably 80-100% of the absolute vapor pressure of water at the extrusion temperature Tf. The temperature T in the pressurized solidification zone is at least equal to the water saturation temperature at the vapor pressure equal to the partial pressure p in the solidification zone and may extend upwards to the temperature at which the main decomposition of the resulting burst occurs, although it is preferable to keep the temperature below. The total pressure P in the solidification zone must be at least equal to the partial pressure p but preferably should not exceed the partial pressure p by a factor of 25.

Even higher total pressures can be used but such are usually not desirable. The difference between the total pressure P and the partial pressure p, if any, comprises other fluids such as air, nitrogen, sulfur dioxide, etc. Preferably the total pressure P is equal to or not significantly above the partial pressure p and very little, if any, other fluids are present. As a result of the application of the above conditions in the solidification zone, there is an interface planecc.no of the amount of water evaporated from the resulting burst. The term "interfacial equilibrium" of evaporation means that the amount of water evaporated from the surface of the resulting burst is equal to or less than the amount of water that diffuses from the inside of the generated burst to its surface, resulting in a relatively uniform residence time in the solidification zone.

When the resulting burst is in the solidification zone, its cross-section is reduced by stretching, i.e. the burst is stretched with a stretch ratio of 25 to 250, preferably 35 to 150. The linear velocity through the spinneret is calculated by dividing the volume of extruded melt per unit time by the total cross-sectional area of all the holes in the spinneret. The elongation at break, i.e. the reduction ratio of the cross sections during stretching, is the linear speed at which the shaped articles pass in the traction device (such as traction wire or wire take-up rollers, whereby the circumferential speed of such a traction roll is taken as the linear velocity of the shaped article) divided by the linear velocity. The solidification belt for the zone space outside the temperature, pressure and composition conditions defined above does not achieve such very high burst elongations.

When the reduction of the cross-section by stretching, which takes place in the solidification zone, is performed in one step, it is also possible to achieve a small batch of the entire cross section in two steps, namely in the first step with a stretch ratio of 5 ~ 150, followed by a second step with a stretch ratio of about 1.1-30, or even higher. to give a reduction in overall cross-section in the solidification zone.

<11 57792

Since the filaments made by the process of this invention do not require a second stretching or post-drawing as opposed to other melt spinning processes for organic filaments and dry spinning or wet spinning processes for making acrylonitrile polymer filaments, the fibers from the solidification zone can be by any of the known methods for this purpose, such as conveying them over a heated feed roller to a slower rotating wire receiving roller or conveying them on a conveyor belt through an atmosphere of saturated pressurized steam.

For a more detailed and detailed explanation of the invention and its further advantages, reference is made to the accompanying description and examples of preferred embodiments shown in the accompanying drawings, in which: Figure 1 is a schematic drawing illustrating the process of the present invention for making continuous strands; acrylonitrile polymer / water system phase diagram.

Figure 1 shows in general an extruder 11 provided with a spinning nozzle 12 at its discharge opening and a pressurized solidification chamber 13 arranged to receive a burr from the spinning nozzle 12. As shown in the figure, the extruder 11 is shown as a piston-extruder in which the cylinder 15 is provided with a tightly fitted piston 16 which can be moved by means not shown in the figure to force the contents of the cylinder 15 through the spinneret 12 directly into the pressurized solidification chamber 15. 17 is heated to a suitable temperature by means of heating devices not shown in the figure, such as steam sheaths or electric heaters in the walls of the cylinder 15. The cylinder 15 is also provided with a thermometer 18 and a pressure gauge 19 for monitoring the temperature and pressure in the extruder 11 during melt spinning. Although the extruder 11 is shown as a piston extruder, other types of extruders can be used, such as screw extruders, gear pumps, etc., which are known for melt spinning of other organic polymers.

A spinning nozzle 12 is mounted in the discharge opening of the extruder 11. The spinning nozzle 12 may be provided with round or non-round holes for spinning strands or fibers or slots for spinning strips or films. The burr from the spinning nozzle 12, shown here as strands 21, goes directly to the pressurized solidification chamber 13, from which it is drawn, under tension, 12 57792 with rapidly rotating wire or wire receiving rollers 22, which give very high burst elongations of this method. the pressurized solidification chamber 13 is provided with an inlet 2h through which pressurized fluid can be introduced at an elevated temperature, an outlet 25 from which liquid can be removed as required, and a thermometer 26 and a pressure gauge 27 for monitoring temperature and pressure in the chamber 13 · which is described herein as a long thin slit which is only slightly wider than the diameter of the thread bundle 21 passing through it. Other pressure retaining devices may be used, illustrated by those described in U.S. Pat. in patents 2,708.8U3; 2,920,931 *; 2,932,183; 3.012.U27; 3.027.7 ^ 0; 3,037,369; 3.0U6.773; 3,066,006; 3,083,073; 3,118,151 *; 3.126.72U; 3,137,151 and 3,152,379, all of which relate generally to the continuous relaxation of acrylonitrile polymer filaments at elevated vapor pressures at elevated temperatures.

From the wire or wire take-up rollers 22, which may optionally be located inside or outside the pressurized chamber 13 as described, the strands 21 may be wound on the wire pack 30 by means of a suitable twisting device, not shown, or preferably the strands 21 may be loosened in a steam chamber 33 with elevated steam and elevated pressure. the temperature is allowed to come into contact with the strands 21 in a relaxed state where they are free to shrink, as described in U.S. Pat. patents. In the chamber 33, the strands 21 are fed through an inlet pressure lock (not shown) by means of feed rollers 35 to a conveyor belt 36 through which they pass through a steam chamber 33 to discharge rollers 37 which feed stress-free strands into an outlet pressure lock not shown in the figure. using a suitable rotating device not shown.

It is well known to combine various additives into shaped articles by adding such additives to the liquefied polymer prior to extrusion. These additives are normally used to modify the properties of shaped articles thus prepared or to improve spinnability. Such additives may be stabilizers, such as lightfastness enhancers, heat resistance enhancers, antioxidants, gas phase stabilizers, ultraviolet stabilizers, etc., pigments, dyes, brighteners, bleaching agents, flame retardants, flame retardants, flame retardants. builders, porosity enhancers, fibrillation enhancers, anti-staining agents, fillers, reinforcing agents, microcapsule encapsulants, latexes, etc. In the practice of this invention, small amounts (e.g., up to about 25) may be added. substances to a single-phase mixture melt before melt spinning, provided that (a) their particle size is small enough to allow unimpeded passage through the orifice or (b) their melting points are close to the minimum polymerization temperature ( M) or below in the presence of a melting aid or they are soluble in the melt melt. Such additives include polymers such as polyvinyl alcohol, polyvinyl chloride, polyacrylamide, polyacrylic acid, polyalkylene glycol ether, etc. The molecular weights of these polymers may be approx.

From 1,000 to over 100,000. Other useful additives include flame retardant haloalkyl phosphates, titanium dioxide pigments, cationic dyes, anionic dyes, dispersible dyes, silicic acid, aliphatic or aromatic halogen compounds, organic phosphorus compounds, such as antimony oxides. These additives do not normally affect the location of the single phase alloy melt region in the phase diagram, however, if some are used, the phase diagram should be redefined in their presence to ensure the boundaries of this region used in the melt spinning process.

Optionally, the process sequence described above may include additional steps such as second stretching or post-drawing, curling, re-stretching, washing, treatment with antiseptics, anti-staining agents, flame retardants, adhesion promoters, lubricants, etc., dyeing, chemical post-treatment to obtain product modifications such as are known to be obtained by these conventional steps. Some of these additional steps may be performed in the same physical structure as the solidification zone, if desired, albeit under ambient conditions that are outside those required in the solidification zone. Additional illustrative steps that may be performed in a similar physical structure to that of the solidification zone include second stretching or post-drawing, loosening, re-stretching, pressure dyeing, drying, etc. Usually, but not necessarily, such additional steps are performed at elevated pressure.

In Nfy, a plurality of single-phase mixture melts can be extruded simultaneously through a spinning die to form shaped mixed or multicomponent products, such as parallel, sheathed, dispersed, bi-, tri-, or multi-component fibers, using equipment known for this purpose. The single-phase blend melts used for this purpose may be of the same or a similar polymer, e.g. all acrylonitrile polymer, or may be of different polymers.

57792

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Single-phase blend melts may be incompatible to form fibers that easily split apart, or they may be compatible to remain permanently adhered to each other in shaped articles. In addition, hollow fibers can be made by extruding one of the phase alloy melts around the gaseous core. In all of these alternative embodiments, the extrusion takes place directly into a solidification zone with defined temperature, pressure, and composition conditions.

The present invention and its further advantages will be better understood from the following illustrative examples, which illustrate preferred embodiments thereof.

All parts and percentages are by weight unless otherwise indicated.

Example 1 This example first illustrates a method for determining a phase diagram for locating its single-phase mixed melt region. The example then illustrates the melt spinning of an acrylonitrile polymer in accordance with the invention and, for comparison, in accordance with a melt spinning process which is outside the scope of the invention.

The phase diagram depicted in Figure 2 for an acrylonitrile polymer / water system in which the acrylonitrile polymer was a polymer containing 89.3% acrylonitrile and 10.7% methyl methacrylate and having a molecular weight of about 58,000 was determined by the following series of tests.

A sample of 1 g of fully oven-dry acrylonitrile polymer was placed in an aluminum dish and autoclaved in saturated steam at 135 ° C for 5 minutes. The sample was removed and cooled. The polymer easily crumbled into a powder, had a opaque appearance, and no microscopically fused particles were observed. The procedure was repeated at 10 IU and 1 5 ° C with essentially the same results. The procedure was repeated at 150 ° C. This time the polymer did not crumble, appeared completely silage and had a glossy surface. When examined under a microscope, the sample had a uniform surface and no individual particles could be observed. The procedure was repeated again at 155, 160, and 165 ° C without any significant change to the 150 ° C sample, except that the yellowishness of the polymer had increased somewhat. The DAE line in Figure 2 was therefore drawn to 150 ° C.

A polymer / water mixture was prepared containing U0% polymer and 60% water. The mixture was placed in a sealed cell as described above and heated in an oil bath to 150 ° C for 10 minutes. The sample was found to be viewed through the window as two phases. The sample was cooled and removed from the cell. The two phases were found to be a fused polymer and free water.

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The procedure was repeated with polymer / water blends containing 60 JS, 70 JS, T5 and 80 & polymer with the remainder being water. In all cases, two phases were observed. When the procedure was repeated again using a mixture of 35% polymer and 15% water, only one phase was observed at 150 ° C and after cooling and sample removal only partial fusion of the polymer was observed despite the fact that only one phase was detected.

This test was repeated again using a polymer sample containing 82% polymer and 18% water. When heated to 150 ° C, only one phase was observed. After cooling and examination, it was found that complete polymer fusion or melting had taken place in the polymer. Point A in Figure 2 was not taken if the water content was about 18% and the polymer was 82% at 150 ° C. Of course, there may be a small area, perhaps between 17-19% water at 150 ° C, which means area A.

In any case, it is not as low as 15> i or as high as 20 # water for this particular polymer at 150 ° C.

Once point A, the minimum melting point of the single-phase mixed melt, was determined, the phase boundary lines ABF and ACG in Fig. 2 had to be determined next.

Sufficient water was added to the full oven dry polymer to form a mixture of 38% polymer and 12% water. When this was placed in a sealed cell and heated to 150 ° C, no fusion or phase separation was observed. In separate tests, the sample was heated to 155 ° C, 160 ° C, 165 ° C, and 170 ° C. The sample showed an increasing tendency to partially fuse with increasing temperature. However, complete melting or melting was not observed until the sample was heated to 170 ° C. In all cases, only one phase was observed. This set of tests locates the point on the line ABF at a site with 12% water and 83% polymer at 170 ° C. Additional points on the line ABF in Figure 2 can be determined - similarly using other configurations such as 85% polymer and 15% water.

The procedure was repeated using a polymer blend of 75% polymer and 25% water. At 150 ° C, two phases were observed. In separate tests, the sample was heated to 155, 160, 165, 170, 175 and 180 ° C. In all cases, two phases were observed. In each case, the polymer was fused or melted and a layer of excess free water was observed in each case. The procedure was repeated by heating the sample to 15 ° C. When the polymer fused, only one phase was observed and no excess free water was found. After cooling and examination, the sample was found to be completely fused or melted and no water was found in the visible cell. The dot on the line ACG was therefore located at 25% water and 75% polymer at 185 ° C. Additional points on the ACG line in Figure 2 can be determined in the same manner using 16 57792 other configurations, such as 22% water and J8% polymer.

After the phase diagram for the aqueous blends of this polymer was determined as shown in Figure 2, the following experimental melt spins were performed using essentially similar equipment as schematically shown in Figure 1.

To 15 g of dry polymer was added 3.3 g of water to give an acrylonitrile polymer / water mixture containing 18% water. The mixture was sealed in a can and mixed in a roller mill for 30 minutes to ensure complete mixing. The mixed mixture was then placed in a piston extruder 11 equipped with a spinneret 12 having a single hole with a diameter of 0.1 mm and a hole length of 3.3 mm. The hole opening was temporarily closed to prevent premature removal of moisture during the lifting phase .; Extruder 11 and spinneret, o. . . ... ....

12 was heated to 15 ** C under sufficient pressure to prevent water evaporation. The orifice of the spinneret was opened and a force of 5517 kN / m was applied to the piston to extrude 16 strands. In the first experiment, for comparison purposes, the solidification pressure chamber 13 was left open at atmospheric pressure so that the strands 21 were extruded to ambient temperature and pressure.

The pressure in the piston 16 was adjusted so that the flow rate of the single-phase mixed melt through the hole of the spinning nozzle was 0.1 U6 m per minute. The resulting fibers were recovered directly to the yarn package 30 (without the use of guide rollers 22) by a rotary twister. After start-up, the speed of the rotating rotary device was gradually increased until the maximum, determined from continuous thread breakage, was reached. The maximum recovery rate achieved was 1.16 m per minute in terms of cross sections when stretched or with a burst stretch ratio of 1.16 / 0, UU6 or 2.6 (260% burst elongation).

In another experiment according to the invention, the pressurized solidification chamber 13 was closed and the saturated steam was passed through the inlet 2h until a pressure of 262 kPa was reached, which corresponds to a temperature of 10 ° C. This temperature was. | o ..... .

about 14 ° C below the melting temperature of the single-phase mixed melt in the extruder and about 10 ° C below the minimum melting temperature of this melt of 150 ° C.

Under these conditions, which were otherwise a replica of the first experiment, the maximum recovery rate achieved was 38 m per minute in terms of cross-sections when stretched or with a burst stretch ratio of 85 (8.500% burst elongation). A batch of the fiber thus prepared, having a denier of 15 per strand, was collected and exposed to saturated steam under pressure at 127 ° C in a relaxed, shrinkable state in an autoclave. Denieri increased to 19.5, indicating that about 23 shrinkages had been achieved. The properties of the loosened fiber were: Direct strength 3.5 g / denier

Straight elongation 1 * 3.0%

Loop strength 1.98 β / denler

Loop elongation 19.0%

Initial modulus 58.0 g / denier

Example 2 This example illustrates the use of the invention for melt spinning of acrylonitrile polymer filaments having a finer denier than in Example 1.

The second experiment of Example 1 was repeated, concluding that the flow rate of the single-phase mixed melt through the hole of the spinneret was 0.792 meters per minute and the saturated steam pressure in the solidification chamber 13 was increased to 33® kPai, corresponding to a temperature of l7 ° C. This temperature was about 7 ° C lower than the extruder temperature and about 3 ° C lower than the melting temperature of the single phase alloy melt for this combination 150 ° C. The maximum recovery rate achieved under these conditions was 89 meters per minute for cross sections when stretched or with a burst stretch ratio of 112 (£ 11,200 burst elongation). The resulting denier of the filaments was 6.1 *, thus indicating that a wider denier range is possible with a single spinneret hole size. . In the practice of this invention, using different sizes of spinneret orifice sizes, acrylonitrile polymer fibers with denier ranging from 0.5 to 80, and even higher, can be made if desired.

Comparative Example A

The first experiment of Example 1 was repeated except that a strip heater was installed along the entire length of the solidification chamber 13. When the chamber 13 opened directly to the outside air and the strip heater gave the chamber 13 an air temperature of about 150 ° C, which closely resembled the conditions used for conventional melt spinning of other organic fibers to obtain large cross-sectional ratios during stretching or to obtain high burst stretch ratios. completely filled with bubbles resembling stretched foam. The maximum burst stretch ratio obtained was not higher than in the first experiment of Example 1 (no heating, no pressurized steam) and was even lower due to the breakdown of this highly heterogeneous material. This showed that the elevated temperature without a pressurized smelting aid environment could not give the very high burst elongations of this invention but instead give a contaminated product.

18 57792

Comparative Example B

The second experiment of Example 1 was repeated except that nitrogen was used at ambient temperature instead of steam in the pressurized chamber 13. When the nitrogen pressure was raised to 56 psi, when the linear velocity of the single phase melt through the spinneret hole was 0.63 m / min, the maximum recovery rate obtained for uneven strands that could be achieved at 2.9 m / min in cross-sections at stretch or with a burst stretch ratio of U.6 (U60% burst elongation), slightly higher than the burst ratio obtained at ambient temperature and pressure (first experiment of Example 1), but nowhere In this case, the very high burst stretch ratios achieved by this invention (second experiment of Example 1 and Example 2). This showed that the elevated pressure without the melting aid environment at the elevated temperature could not give the very high burst stretch ratios of the present invention.

Example 3

Example ϋ was repeated using the strip heater described in Example A to heat the pressurized nitrogen at 386 kPat in chamber 13 to various temperatures. After raising the ambient temperature to 10 ° C, the maximum cross-sectional ratio achieved was stretched from about 6 to about 10.1 (1.010% elongation) without stretching the bubbles of Example A. Sub-heating to 150 ° C did not result in an increase in the achievable cross-sectional ratio during stretching. Heating above 150 ° C caused the fiber to melt, resulting in discontinuity and rupture of the fiber. This showed that the elevated temperature and the elevated temperature without the smelting aid environment, while providing some improvement in the cross-sectional ratio during stretching, were not yet able to give the very high burst stretch ratios achievable with this invention.

Comparative Example C

To 15 g of a dry polymer with 89.3% acrylonitrile and 10.7% methyl methacrylate and a molecular weight of about 58,000 was added 3.3 g of water to give an acrylonitrile polymer / water mixture containing 18% water. . The mixture was sealed in a can and mixed in a roller mill for 30 minutes to ensure complete mixing. The mixed mixture was then placed in a piston-extruder equipped with a spinning nozzle in its discharge orifice with a single hole with a diameter of 0 * 4 ns »and a length of 2.3.

The opening of the hole was temporarily closed to prevent premature loss of moisture during the lifting phase. The extruder and spinneret were heated to 19,57792 15 ° C under sufficient pressure to prevent water evaporation, thereby converting the acrylonitrile polymer / water mixture to a single phase melt.

The orifice of the spinneret was opened and a force of 5517 kN / m was applied to the piston of the piston extruder to extrude the thread through the hole. The pressure in the piston was then adjusted so that the flow rate of the single-phase mixed melt through the hole of the spinning nozzle was 0.1 + 6 meters per minute. The resulting filaments, after passing through and cooling in ambient air from a spinning nozzle to a wire spooler, were collected in a yarn package at a slightly achievable burst elongation ratio, about 2.6, and allowed to dry at room temperature. These strands were opaque, white and very shiny. In microscopic studies, they were found to contain many cavities and microcavities.

Comparative Example D

The procedure of Comparative Example C was repeated, it would be concluded that the resulting filaments were extruded through the hole of the spinning nozzle directly into a pressurized chamber containing steam at a pressure of 262 IPa and a temperature of 1 ° C. The resulting filaments, after passing through a pressurized steam zone, were assembled into a yarn package by a wire twisting device with a burst elongation slightly below the maximum burst elongation ratio achievable, about 85 °. These strands were then loosened to a space where they could shrink freely in an autoclave with pressurized steam from 127 ° C. These strands were also opaque, white, and very shiny. When examined under a microscope, they were found to contain many cavities and microcavities. However, they had physical properties that were acceptable for use in textile fibers.

Comparative Example E

The strands of Comparative Example C, after being dried at ambient conditions, were heated in an oven in an attempt to cause the cavities and microcavities to disappear. No changes in appearance were observed. Relaxation under pressure O ... · · · After heating in a steam oven at 127 ° C, the appearance of these strands also did not change.

Example k

By repeating the procedure of Comparative Example D, except that the fibers, as they leave the vapor pressure chamber, pass through a second pressurized chamber containing air or nitrogen at 262 kPa and 10 ° C and where they are dried, are obtained according to the present invention. filaments, 20 57792 having no cavity or microcavities and which are translucent and have a similar gloss to commercially available acrylic fibers. This illuminates the drying of the freshly spun acrylonitrile polymer while it is still spinning hot before allowing it to cool below about 90 ° C.

Example 5 According to this example, the procedure of Comparative Example B is modified to produce fibers having a durable curl of the textile process. In a pressurized chamber containing steam at a pressure of 262 kPa and a temperature of 1 U0 ° C, a first set of wire receiving tubes are placed to stretch the resulting strands as they burst through the orifices of the spinning nozzle to give them a burst stretch ratio of about 75 »and a second set of wire receiving rotating at a lower speed and designed to remove tension from the strands. From the second set of wire receiving rollers, the strands are fed to a sealing sleeve, which acts as a pressure lock in the wall of the pressure chamber. The fibers curled in the straw compactor are suddenly cooled with cold water. After leaving the curler, the strands are kept wet until they are dried in an oven at 110 ° C. The filaments thus prepared according to the invention are translucent, free of cavities and microcavities and have a good gloss.

Example 6 This example illustrates the melt spinning of acrylonitrile polymer fibers in accordance with the process of this invention using other melting aids.

Using the same equipment as in Examples 1 and 2, the acrylonitrile polymer of Example 1 can be spun into filaments under the following conditions: A. A single phase melt of acrylonitrile polymer and methanol (ca. 75% acrylonitrile polymer and ca. 25% methanol). At C, can be extruded through a hole in a spinneret at a flow rate of 0.792 meters per minute directly into a solidification zone with a methanol vapor atmosphere of 11 + 8 ° C and a pressure of 1131 kPa to give strands which can be given a 100-fold cross-section.

B. A single-phase mixed melt of acrylonitrile polymer and acetonitrile (ca. 80% acrylonitrile polymer and ca. 20% acetonitrile) at 155 ° C can be extruded at a rate of 0.792 m per minute directly into a solidification zone with an acetone zone of an atmosphere with a temperature of 10 ° C and a pressure of U55 kPa to give strands which can be stretched at least 100-fold.

C. A single-phase mixed melt of acrylonitrile polymer and dilute aqueous sodium thiocyanate solution (ca. 75% acrylonitrile polymer, 21 57792 ca. 19% water and ca. 6% sodium thiocyanate - such aqueous sodium thiocyanate solution is named is one which does not normally dissolve the acrylonitrile polymer and is sufficiently dilute to be used as a coagulant in wet spinning of acrylonitrile polymers) at 1 ° C, can be extruded at a rate of 0.792 m / min directly at a solidification zone containing a solidification zone. C and a pressure of 262 kPa, to give strands which can be stretched at least 100-fold.

D. A single-phase mixed melt of acrylonitrile polymer and acetic acid (about 77% acrylonitrile polymer and about 23% acetic acid) at 155 ° C can be extruded at a rate of 0.792 m / min directly into an acetic acid vapor atmosphere. temperature IU5 C and pressure 117 kPa, to give strands that can be stretched 100-fold even.