KR920008998B1 - Process for the production of highly-oriented acrylic short fibers without spinning - Google Patents

Abstract

The method for producing highly-oriented fibrillar pulp-like staple fiber whose thickness 0.1-100 μm and length 0.1-100 mm comprises: making mixtures of acrylonitrile homopolymer or comonomer, composed of more than 70 wt.% acrylonitrile and less than 30 wt.% copolymerizable monomer and whose viscosity average mol.wt. is 10,000-60,000, and 5-100 wt.% water; heating above m.p. under the closed condition to make non-crystalline melts; cooling these melts below m.p. to make overly-cooled melts; extruding them under the condition of between m.p and solidifying point to make extrudates whose cross-section of fibrils has evenly-aligned feature, crystalline state and degree of orientation above 70 %; heat-drawing and beating.

Description

Method for producing unspun high orientation acrylic short fibers

FIG. 1A shows a typical melt endothermic peak and a solidification exothermic peak by differential scanning calorimetry (DSC) of an acrylonitrile polymer water content, wherein the molten quasicrystalline phase having molecular order between the melting temperature (Tm) and the solidification temperature (Tc) The temperature range OR can be formed.

FIG. 1b shows, as an example of FIG. 1a, a melt endothermic peak and a solidified exothermic peak of a water-containing water in which 20% of water is mixed with an acrylonitrile polymer containing 89.2% of acrylonitrile and 10.8% of methyl acrylate in weight ratio.

FIG. 2a shows a typical change of the melting temperature and the solidification temperature according to the water content in the water content of the acrylonitrile polymer, and shows a temperature range in which a molten quasi-crystalline phase having a molecular order similar to that of liquid crystal can be formed. have.

FIG. 2B shows a change in the melting temperature and the solidification temperature depending on the water content in the hydrate of the acrylonitrile polymer containing 89.2% acrylonitrile and 10.8% methyl acrylate in weight ratio as an example of FIG. 2A.

3 shows the change of the melting temperature and the solidification temperature according to the content of methyl acrylate, which is a copolymerization monomer, in the water of acrylonitrile polymer, and the acrylonitrile polymer is increased as the methyl acrylate content is increased in the acrylonitrile polymer. It shows that the melting temperature and the solidification temperature of the water are lowered.

Figure 4 shows the orientation of the extrudate according to the temperature of the melt when extruding the melt of the acrylonitrile polymer water content, the orientation degree is almost unoriented at about 50% in the temperature range to form an amorphous melt In the temperature range for forming the molten quasi-crystalline phase, it indicates that the orientation is also high molecular orientation of 80% or more.

Figure 5a is a structural model in which the acrylonitrile polymer chain forms a three-dimensional molecular order by interaction with water molecules when the semicrystalline phase of the acrylonitrile polymer hydrate is extruded in the molten state.

FIG. 5b shows structural models in which acrylonitrile polymer chains form a plate feed reel of linear chains when fibers are formed after extrusion solidification. The polymer chains extend in the direction of ＂C＂ at the arrow and ＂V＂ at the arrow. Weak van der Waals force in the direction and the hydrogen bonding force on the molten semi-crystalline phase in the ＂H＂ direction during the formation of the fiber shrinks as water escapes during fiber formation It is indicated that the dipole attraction between the nitrile groups acts in the ＂D＂ direction at the arrow instead of the hydrogen bonding force after formation.

FIG. 6 is a scanning electron microscope photograph of the cross section and the longitudinal section of the tape-like extrudate obtained by extruding the molten semi-crystalline phase and the fibers are formed. The cross-sectional fibrils are neatly stacked in the cross section with the space where the water escapes. In the cross-sectional structure and longitudinal section, each fibrils are separated into microfibrils again to form an internal structure forming a fiber.

FIG. 7 illustrates the cross-sectional and longitudinal cross-sectional structure of the tape-shaped extrudate of FIG. 6, wherein the plate-shaped fibrils are stacked in the cross-sectional structure and the longitudinal cross-sections of the tapered extrudate are arranged in the cross-section. It shows an internal structure composed of many microfibrils and indicates that fibrils and microfibrils can be easily separated into individual fibers.

FIG. 8 is an X-ray diffraction pattern photograph of the tape-like extrudate of FIG. 6, showing that the fibrous crystal structure and the highly oriented structure are formed.

FIG. 9 is a diffraction intensity curve scanned in the azimuth direction at the position of the main diffraction peak (2θ = 16.2 °) in the equator direction on the X-ray diffraction pattern of FIG. 8, and it can be seen that high molecular orientation is achieved.

FIG. 10 is a scanning electron microscope photograph of pulp-like short fibers obtained by cutting a heat-extruded tape-like extrudate to an appropriate length and beating it. Each fiber is composed of fibrils and microfibrils. It shows that it has many cracks and branches in irregular cross sections and sides.

The present invention relates to a process for producing new pulsed short fibers with high orientation without the usual spinning process using acrylonitrile polymer (hereinafter abbreviated as “PAN”).

PAN is known to have properties close to the straight chain because of the strong polarity of the side chain nitrile group, the molecular chains are irregularly twisted. See WR Krigbaum et al., Journal of Polymer Science, Vol. XLIII, 467-488, (1960). When a strong solvent such as dimethylformamide, dimethylacetamide, dimethylsulfoxide, or NaSC N aqueous solution, ZnCl ₂ aqueous solution or HNO ₃ aqueous solution is added to such a polymer, the natril groups are affinity with the solvent even at room temperature. As they bind, they separate from each other to form a fluid solution.

It is known a method for producing fibers by spinning a mixed solution of PAN and a solvent through the micropores of the spinneret using the properties of the PAN.

According to this method, when the solvent is removed after spinning the flowable solution, the PANs are solidified while forming a fiber, but the molecular chains inside the solids are bound to each other while forming an unoriented bundle. Therefore, the filament immediately after spinning has a fibrous shape, but since the inner molecular chains are not oriented at all, when the solvent is removed and dried, the PAN molecular chains in the spun fiber shape are aggregated again to form a powder state. Therefore, in order to have a complete fiber structure in terms of molecular composition, the filaments must be stretched at a high magnification of 5 to 30 times or more so that the molecular chains are aligned with the fiber axis. At this time, the PAN molecular chains that are agglomerated in an unoriented direction are unfolded and unfolded and arranged to form fibers having an extended chain crystal region. For this reason, in the conventional fiber manufacturing process, the stretching process becomes an indispensable core process, and only this process can form a substantial fiber structure in which most of the molecular chains are aligned with the fiber axis.

However, in the prior art using the solvent as described above, the extraction, recovery and purification of the solvent is not only expensive, but also has the disadvantage of causing environmental pollution by the solvent.

In order to alleviate these drawbacks, a method has been proposed in which a PAN is mixed with water to form a melt and spin-drawn the melt to produce fibers. For example, U. S. Patent No. 2,585, 444 prepares a molten fluid by heating a water containing 30% to 85% water by weight to PAN above a melting temperature, and from this, to produce a PAN fiber through melt spinning. It tells you that you can. U.S. Patent No. 3,896,204 and U.S. Patent No. 3,984,601 mix PAN with a weight ratio of about 20% to 30% of water to spin an amorphous melt obtained at a temperature from 170 ° C to 205 ° C and draw at least 5 times to prepare fibers. have. In U.S. Patent No. 3,991,153 and U.S. Patent No. 4,163,770, a filament injected by spinning a PAN water mixture of water having a weight ratio of 10% to 40% at or above the melting temperature, that is, above the temperature at which the melt forms an amorphous single phase Is stretched 25 to 150 times in a pressure chamber to produce fibers. However, the prior art as described above spins in the temperature range present as a disordered amorphous melt and therefore cannot produce fibers oriented with PAN molecular chains without highly stretching the filaments.

In addition, US Pat. No. 3,402,231, US Pat. No. 3,774,387, and US Pat. No. 3,873,508 add one or more times water to PAN to make a melt at a temperature of about 200 ° C. and spin the melt to produce fibers for pulp. However, because these patents use excess water to obtain the melt at high temperatures, the PAN / H ₂ O melt is not only disorderly amorphous, but the spun PAN filament from which it looks like is formed into fibers, It is just an unoriented continuous foam that has not achieved any orientation or fiber structure.

In the melt spinning technique of the conventional PAN water content as described above, in order to have a fiber structure, a fiber structure cannot be obtained unless it is stretched at a high magnification, for example, 5 to 30 times or more.

The present inventors have made intensive studies on the two-component system of PAN and water (hereinafter, abbreviated as “PAN / H ₂ O system”), and found the following surprising facts. That is, the PAN / H ₂ O system absorbs the heat of fusion at the melting temperature (Tm) and then forms an amorphous melt single phase, which does not crystallize to a certain temperature range (OR) even when cooled below the melting temperature again, and melts supercooled. The PAN crystallizes and returns to its original state when it is further cooled below the solidification temperature Tc while maintaining the state. However, when the PAN / H ₂ O melt is cooled in a supercooled state, unlike the amorphous high temperature melt, PAN and water participate together as a single phase to form a quasi-crystalline phase having a molecular order similar to that of a liquid crystal. Done. Such quasicrystalline phases are very easily molecularly oriented by extrusion as shown in FIG.

In the supercooled melt of such a molten quasi-crystalline phase, it is assumed that PAN molecular chains together with water molecules form a myriad of fine unit regular phases having a linear molecular order. Since the PAN molecular chains in the molten quasi-crystalline phase have the property of spontaneous orientation, given a slight directional shear force by mechanical extrusion operation, they form a highly oriented fiber structure very easily. That is, when the molten semi-crystalline phase is extruded, while the linear PAN molecular chains are laterally approached to each other, the contained water is automatically discharged out of the system to form a fiber structure, so that highly oriented fibers can be produced without a high magnification stretching process.

The pulp-like acrylic short fibers of polymer orientation produced by the method of the present invention are not only suitable as industrial materials such as asbestos replacement fibers, heat-resistant heat-resistant fibers, cement-reinforced fibers, but also as pulp for paper production.

Accordingly, it is an object of the present invention to provide a method for producing a new unspun high orientation acrylic short fibers having a high molecular orientation fiber structure without carrying out the spinning process or the stretching process of a high magnification of the prior art.

It is another object of the present invention to simplify the provision of complex pulp-like short fibers, such as a preparation process of spinning a PAN in a solvent, a spinning process, a solidification process, a solvent removal and recovery process, a stretching process, and a fibrillation process. It is to provide a method for producing pulp short fibers.

The above and other objects will become more apparent from the following detailed description.

According to the present invention, an airtight container which is composed of an acrylonitrile having a weight ratio of at least 70% and a monomer for copolymerization having a weight ratio of 30% or less and mixed with a water content of 5% to 100% by weight in a PAN having a viscosity average molecular weight of 10,000 to 600,000. Heated to form an amorphous PAN / H ₂ O melt, followed by cooling the amorphous melt to produce a molten semi-crystalline supercooled melt having a molecular order similar to liquid crystal between the melt temperature and the solidification temperature. Extruded through the extrusion hole of the standard to form a fiber structure, the water is automatically discharged and solidified to obtain a highly-oriented extrudates in which the plate-shaped fibrils are neatly stacked, and the extrudate is heat-treated to improve the orientation, then the appropriate length The pulp upper fibers are prepared by cutting and beating.

PAN in the present invention means an acrylonitrile homopolymer and a copolymer of acrylonitrile with one or more copolymerizable monomers. In the composition of the copolymer, acrylonitrile should occupy at least 70% by weight, and even more copolymerized monomers, should account for 30% or less by weight. More preferably, acrylonitrile occupies at least 85% by weight and copolymerizable monomers At most, the weight ratio should occupy less than 15%.

Examples of the copolymerizable monomer include methyl acrylate, methyl methacrylate, ethyl acrylate, chloroacrylic acid, ethyl methacrylate, acrylic acid, methacrylic acid, acrylamide, methacrylamide, butyl acrylate, methacrylonitrile and butyl methacryl. Latex, vinyl acetate, vinyl chloride, vinyl bromide, vinyl fluoride, vinylidene chloride, vinylidene bromide, allyl chloride, methyl vinyl ketone, vinyl formate, vinyl chloroacetate, vinyl propionate, styrene, Vinylstearate, vinylbenzoate, vinylpyrrolidone, vinylpiperidine, 4-vinylpyridine, 2-vinylpyridine, N-vinylphthalimide, N-vinylsuccinimide, methylmalonate, N-vinylcar Basezol, metal vinyl ether, itaconic acid, vinylsulfonic acid, styrenesulfonic acid, allylsulfonic acid, metalylsulfonic acid, vinylfuran, 2-methyl-5-vinylpyridine, vinylnaphthalene, Ethylene units such as taconic acid ester, chlorostyrene, vinyl sulfonate, styrene sulfonate, allyl sulfonate, metalyl sulfonate, vinylidene fluoride, 1-chloro-2-bromoethylene, alphamethylstyrene, ethylene and propylene And monomers for addition polymerization having a double bond.

The molecular weight of PAN is obtained by measuring absolute viscosity ([η]) using N, N-dimethylformamide as a solvent and obtaining the viscosity average molecular weight (Mv) from the following relationship (T. Shibukawa et al., Journal of Polymer Science, Part A-1, Vol. 6, 147-159, 1968).

[η] = 3.35 × 10 ^-4 Mv ^0.72

The absolute viscosity is measured at 30 ° C. by dissolving PAN in N, N-dimethylformamide. The molecular weight of the acrylonitrile polymer in the present invention has a value of 10,000 to 600,000 in terms of viscosity average molecular weight in terms of absolute viscosity, and more preferably 50,000 to 350,000.

When the phase change phenomenon according to the change of water content, temperature, and PAN component is measured by using a differential scanning calorimeter (DSC), it can be seen that there exists a temperature region for forming a molten quasi-crystalline phase such as FIGS. 1a and 2a. At this time, the two-component system of PAN and water produces a phase change at a temperature higher than the boiling point of water at normal pressure, so that the endothermic peak at the time of heating is increased by using a high-capacity pressure cap (Perkin-lmer Part 319-0128) which is completely sealed and can withstand high pressure. And a solidified exothermic peak upon cooling. As shown in FIG. 1A, the peak of the endothermic peak is represented by the melting temperature (Tm), the peak of the exothermic peak is represented by the solidification temperature (Tc), and the molten quasi-crystalline phase is formed by a temperature range (OR) between the melting temperature and the solidification temperature. It shows the area | region which becomes. In FIG. 2A, the temperature region in which the molten quasi-crystalline phase is formed in accordance with the change in the water content is shown in FIG. 3, and FIG. 3 is an example of the region change in accordance with the PAN component change. FIGS. 1b and 2b are examples of FIGS. 1a and 2a, respectively, where water of 20% by weight is mixed using PAN containing 89.2% of acrylonitrile and 10.8% of methacrylate by weight. And FIG. 2B shows a temperature range in which the molten quasi-crystalline phase is formed when the water content is changed from 5% to 50% by weight.

When the water containing the appropriate amount of water in PAN is placed in a pressure-resistant vessel and heated above the melting temperature, a natural vapor pressure is generated and the polymer is combined with water to form a PAN / H ₂ O melt. At this time, an inert gas such as nitrogen or argon may be injected to maintain the pressurized state, and the heating temperature is reached to the melting temperature Tm shown in FIG. The melt produced here is a disordered amorphous fluid.

The amorphous melt is cooled and maintained at a temperature between the melting temperature and the solidification temperature as shown in FIG. 2A to produce a supercooled melt of a molten semicrystalline phase having properties similar to those of liquid crystals. The molten quasi-crystalline phase is a kind of subcooled melt which exists at a temperature lower than the melting temperature but does not solidify and exists as a fluid, and is thought to form a regular phase having a disordered amorphous and molecular order.

This regular phase appears to be a parallel arrangement of linear PAN molecular chains due to the interaction of the PAN molecular chain and water, and has the spontaneous molecular orientation characteristics such as liquid crystal. That is, as shown in FIG. 4, the extrudate compressed at high temperature to produce an amorphous melt is obtained with almost no orientation of 50% of the orientation, whereas the extrudate obtained at lower temperature of the molten semi-crystalline phase has an orientation of 80% or more in the same extrusion operation. High orientation

The temperature range in which the molten quasi-crystalline phase with molecular order can be formed depends on the acrylonitrile content of PAN as shown in FIG. 3 or the water content as shown in FIG. 2A, and the melting temperature and solidification shown in FIG. It belongs to the region between temperatures. When producing the PAN / H ₂ O melt, the pressure applied to the pressure-resistant vessel may be a natural water vapor pressure depending on the temperature, or may be a pressure of about 1 to 50 atm. The content of water contained in the melt is preferably 5% to 100% by weight, more preferably between 10% and 50%.

In the disordered amorphous PAN / H ₂ O melt, the individual PAN molecular chains move more freely, so that the molecular chains are not lumped together irregularly and have no order between the molecules. When the amorphous melt cools and falls within an appropriate temperature range, the molecular chains of the PAN molecules and water are inhibited and restrained by the molecular forces of each other, and the molecular chains form a linear chain order and parallel to other surrounding molecular chains. Arranged to form a molten quasi-crystalline phase that maintains a mutual distance.

In this molten quasi-crystalline phase, since the PAN molecular chains maintain the order between the molecular chains, it is difficult for each molecular chain to act individually, but when the entire molecular chain forming a regular phase moves in a certain direction, as shown in FIG. It seems very easy to have a positive orientation structure. Therefore, it is very easy to solidify by arranging linear molecular chains in a constant direction as in FIG. 4B from a molten quasi-crystalline phase having molecular order, that is, to manufacture a fiber having a high molecular orientation. On the other hand, in the amorphous melt, since each PAN molecular chain is free to move, it cannot not only have order between molecular chains, but also the molecular chains themselves are crumpled and aggregated freely, making it impossible to arrange these molecular chains in a certain direction.

In the present invention, the molten quasi-crystalline supercooled melt has spontaneous molecular orientation characteristics as if it were a liquid crystal. Thus, even by simple extrusion by a piston type extruder, the PAN molecular chain forms a highly oriented fiber structure and the plate-shaped fibrils are neat. It is made of highly oriented extrudates of laminated cross-sectional structure. As the extruder, a screw extruder may be used in addition to the piston extruder, and the extruder may be freely used as a slit die, a tube die, an arc die, or the like. The thickness-to-length ratio of the extrusion port should be 1 or more, and the larger this ratio is, the more effective it is in obtaining high orientation. The extrusion temperature is the temperature range between the melting temperature and the solidification temperature of the corresponding PAN water. Extrusion conditions maintain the internal pressure at least above the self-generated water vapor pressure and extrude into the atmosphere at room temperature and atmospheric pressure at a discharge rate of 1 mm or more per second to wind the continuous extrudate at a linear velocity above the discharge rate. At this time, the ratio of the discharging speed to the reeling speed is one or more, and increasing this ratio is effective for improving the degree of orientation.

In addition, in order to produce a compact structure with improved mechanical properties, molten metal having a high specific gravity by passing through a vertical tube filled with a low melting point and a high specific gravity molten metal made of a molten alloy in conjunction with an extrusion hole It is also effective to suppress the space from which water escapes due to the pressure of. The length of the vertical tube is adjusted according to the required pressure, and the molten alloy filled in the vertical tube is for example Bi (50%) / Pb (31%) / Sn (19%), Bi (50%) / Pb An alloy having a melting point of less than 100 ° C. consisting of (24%) / Sn (14%) / Cd (12%) may be used.

Through the extrusion and solidification of the molten semi-crystalline phase as described above, a tape-like extrudate composed of bundles of fine fibers is continuously produced, which is a space in which plate-like fibrils are separated and removed from each other in a cross section, that is, a dehydration space, as shown in FIG. The fibrils are separated into microfibrils again in a cross-sectional structure and a longitudinal cross-sectional structure arranged in a uniform manner to form an internal fiber. Here, the plate-like fibrils are between 1 μm and 10 μm in thickness, and each plate-like fibrils are composed of microfibrils gathered between 0.01 μm and 1.0 μm thick. As a result of obtaining a diffraction pattern by X-ray diffraction using a tape-like extrudate, it can be seen that the plate-like fibrils and microfibrils have fibrous crystals and a highly oriented structure as shown in FIG. As shown in Fig. 3, the orientation value of the half width (OA) of the diffraction intensity scanned in the azimuth direction at the main diffraction peak position (2θ = 16.2 °) in the equator direction on the diffraction pattern is 70% or more.

In order to further improve the orientation, the continuous extrudate prepared as described above is subjected to heat treatment under a phosphorous state through a hot gas atmosphere maintained at a temperature of 100 ° C to 220 ° C or a high temperature roller to which a compressive force is applied. The hot gas atmosphere is made of a gas that hardly undergoes chemical reaction with PAN, such as water vapor, air, nitrogen, argon, and the like. More preferable heat processing temperature is 120-200 degreeC. An annealing effect of 5% to 100% with respect to the original length is shown during the heat treatment process, and an extruded product having improved mechanical strength and fibril is developed. As a result of analyzing the heat-treated continuous extrudate from the X-ray diffraction pattern in the same manner as before, the orientation was improved than before heat treatment, and the tensile strength and elastic modulus were also improved by heat treatment.

When the heat-treated continuous extrudate is cut and beated to an arbitrary length, pulp-like short fibers as shown in FIG. 10 are produced, and the size of the short fibers is variously obtained depending on the cutting length and the beating condition. The pulp-like short fibers produced are composed of plate-like fibrils and microfibrils having a highly oriented fiber structure, and generally have irregular long elliptical cross-sections and a large number of cracks and branches on the sides. The size of the short fibers is a distribution between 0.1 μm and 100 μm in thickness and between 0.1 mm and 100 mm in length. The individual fibers consist of plate-like fibrils between 1 μm and 10 μm thick and microfibrils between 0.01 μm and 1.0 μm thick. The microstructure of the pulsed short fibers is confirmed by an electron beam diffraction pattern by transmission electron microscopy (TEM), and exhibits fibrous crystals and highly oriented structures, such as those of high-electrode tape-like extrudates.

In the present invention, a high-oriented pulp-like acrylic short fiber is manufactured through a revolutionary simple process of mixing only a small amount of water as a eutectic in the PAN through melt extrusion and heat treatment, thereby significantly reducing manufacturing cost as compared to the conventional method. Pollution problems are automatically solved, and the short fibers themselves have a structural feature composed of highly oriented fibrils.

In terms of the performance of the fiber, it is excellent in physical properties due to its high molecular orientation, and is composed of a myriad of microfibrils, so that the surface area is very large and has an irregular cross-sectional structure, so that binding with other materials is extremely improved.

This fiber The pulp-like short fiber of this invention has the optimal conditions as a pulp material. In particular, since pulp-like short fibers can be produced at a very low price by a simple process, it can be used as a paper raw material instead of natural pulp. In addition, this pulp-like short fiber is composed of fine fibrils and has satisfactory characteristics as a pulp for paper because it has a large number of cracks and branches at irregular long oval cross sections and sides.

Hereinafter, the following examples are described in order to explain the method of manufacturing the present invention in more detail, but it should be noted that the present invention is not limited thereto.

Example 1

Acrylonitrile copolymer with a viscosity average molecular weight of 102,000 and a chemical composition of 92.8% acrylonitrile and 7.2% methyl acrylate in the cylinder of an extruder, which is composed of a cylinder, a piston and a slit die-type extruder, and is capable of sealing and heating insulation. The mixture of 100 g and 22 g of water was chopped and heated to 175 ° C. to be completely melted under pressure at 5 kg / cm 2, and then maintained at 148 ° C. to maintain the temperature again. Through a slit die having a thickness / width / length of 0.25 mm / 20 mm / 3 mm in a normal temperature and atmospheric atmosphere to wind the continuous extrudate on tape at a speed of 2 m per minute. When the structure of the produced extrudate was observed with a scanning electron microscope, a cross-sectional structure in which plate-shaped fibrils having a thickness of 1 μm to 10 μm were stacked neatly with a dehydration space interposed therebetween and a thickness of 0.01 μm to 1.0 μm with numerous fibrils. It has an internal structure that is separated into microfibrils in between. X-ray analysis showed that the tapered extrudate had fibrous crystals and had a molecular orientation of 89%. The continuous extruded tape was thinly separated in the longitudinal direction to make long fibers, and the mechanical properties thereof were measured. As a result, tensile strength of 4.5 g / day, elongation 11%, and tensile modulus of elasticity 67 g / denier were shown. This tape-like continuous extrudate is maintained at 150 ° C. and subjected to a 30% stretch heat treatment by passing under tension between rollers subjected to compression. X-ray analysis showed that the stretch heat treated tape-like extrudate had fibrous crystals and had a molecular orientation of 91%. The stretch-treated continuous extruded tape was thinly divided in the longitudinal direction to make long fibers, and the mechanical properties thereof were measured. As a result, tensile strength of 5.7 g / denier, elongation 10%, and tensile elastic modulus 86 g / denier were shown.

The continuous heat-treated tape-like compressed product is cut into 20 mm lengths and beaten with a beater to prepare pulp-like short fibers. The prepared short fibers have a thickness distribution of 0.1 μm to 20 μm and a length distribution of 1 mm to 20 mm.

Example 2

In a cylinder of an extruder composed of a cylinder, a piston, and a slit die-type extruder, and a sealed and heated insulation, a mixture of 100 g of acrylonitrile homopolymer having a viscosity average molecular weight of 93,000 and 30 g of water was compacted and pressed at 5 kg / ㎠ Heat up to 205 ° C to melt completely, and then keep the temperature down to 178 ° C, then operate the piston to apply a pressure of 70kg / cm 2 through a slit die with a thickness / width / length of 0.35mm / 20mm / 4mm It is extruded in a normal-temperature atmospheric pressure atmosphere, and the continuous tape-shaped extrudate is wound at a speed of 1.5 m per minute. This continuous extrudate is maintained at 170 ° C. and is subjected to 25% stretch heat treatment by passing under tension between the rollers under compression. X-ray analysis showed that the stretch heat treated tape-like extrudate had fibrous crystals and showed a molecular orientation of 90%. The stretch-treated continuous extruded tape was thinly divided in the longitudinal direction to make long fibers, and the mechanical properties thereof were measured. As a result, tensile strength was 6.0 g / denier, elongation 9%, and tensile modulus 93 g / denier, respectively.

The stretched heat treated tape-like continuous compact was cut into a length of 15 mm and beaten with a beater to prepare pulp-like short fibers. The prepared short fibers have a thickness distribution of 0.1 μm to 20 μm and a length distribution of 1 mm to 15 mm.

Example 3

Acrylonitrile copolymer with a viscosity average molecular weight of 178,000 and a chemical composition of 94.2% acrylonitrile and 5.8% methylacrylate in the cylinder of the extruder, which is composed of a cylinder, a piston and a slit die-type extruder, and is capable of sealing and heating. The mixture was mixed with 100 g and 25 g of water, and the mixture was heated to 180 ° C. under a pressure of 5 kg / cm 2 and completely melted. Then, the temperature was lowered to 155 ° C. and the piston was operated to maintain a pressure of 60 kg / cm 2. Hanging extruded through a slit die having a thickness / width / length of 0.25 mm / 20 mm / 3 mm to wind the continuous extrudate on tape at a speed of 2 m per minute. This continuous extrudate is maintained at 160 ° C. and is subjected to 25% stretch heat treatment by passing under tension between rollers subjected to compression. X-ray analysis showed that the stretch heat treated tape-like extrudate had fibrous crystals and had a molecular orientation of 91%. The extruded tape was thinly separated in the longitudinal direction to make long fibers, and the mechanical properties thereof were measured. As a result, tensile strength of 6.1 g / denier, elongation 10%, and tensile modulus of 97 g / denier were shown.

The stretch heat treated tape-like continuous extrudate is cut to a length of 20 mm and beaten with a beater to produce pulp-like short fibers. The prepared short fibers have a thickness distribution of 0.1 μm to 20 μm and a length distribution of 1 mm to 20 mm.

Example 4

Acrylonitrile copolymer with a viscosity average molecular weight of 215,000 and a chemical composition of 88.6% acrylonitrile and 11.4% methylacrylate in the cylinder of an extruder, which is composed of a cylinder, a piston and a slit die-type extruder, and is sealed and heated. The mixture of 100g and 25g of water was chopped and heated to 175 ° C and completely melted under pressure of 5kg / cm 2, and then maintained at 145 ° C again to maintain a temperature of 70kg / cm 2. Hanging extruded through a slit die with a thickness / width / length of 0.40 mm / 20 mm / 4 mm to wind the continuous extrudate on tape at a speed of 1 meter per minute. This continuous extrudate is maintained at 140 ° C. and is subjected to 35% elongation heat treatment by passing under tension between the rollers under compression. X-ray analysis showed that the stretch heat treated tape-like extrudates had fibrous crystals and had a molecular orientation of 89%. The stretched heat treated continuous extruded tape was thinly divided in the longitudinal direction to make long fibers, and the mechanical properties thereof were measured. As a result, tensile strength of 6.3 g / denier, elongation 10%, and tensile modulus of 84 g / denier were shown.

The continuous heat-treated tape-like compressed product was cut into 10 mm lengths and beaten with a beater to prepare pulp-like short fibers. The prepared short fibers have a thickness distribution of 0.1 μm to 30 μm and a length distribution of 1 mm to 10 mm.

Example 5

100 g of acrylonitrile copolymer having a viscosity average molecular weight of 97,000 and a chemical composition of 94.8% acrylonitrile and 5.2% vinyl acetate in the cylinder of the extruder, which is composed of a cylinder, a piston and a slit die extruder, and is sealed and heated. The mixture of 26 g of water and 26 g of water was chopped and heated to 180 ° C. under a pressurized condition of 5 kg / cm 2 to be completely melted. Then, the temperature was lowered to 155 ° C., and the piston was operated to apply a pressure of 65 kg / cm 2. The continuous extrudate on tape is wound at a speed of 1.8 m per minute by extrusion through a slit die having a thickness / width / length of 0.30 mm / 15 mm / 4 mm. This continuous extrudate is maintained at 160 ° C. and subjected to a 27% stretch heat treatment by passing under tension between the rollers under compression. X-ray analysis showed that the stretch heat treated tape-like extrudate had fibrous crystals and showed a molecular orientation of 90%. The stretched heat treated continuous extruded tape was thinly divided in the longitudinal direction to make long fibers, and the mechanical properties thereof were measured. As a result, tensile strength of 5.8 g / denier, elongation 10%, and tensile modulus of 88 g / denier were shown.

The stretch heat treated tape-like continuous extrudate is cut to a length of 10 mm and beaten with a beater to prepare pulp short fibers. The prepared short fibers have a thickness distribution of 0.1 μm to 30 μm and a length distribution of 1 mm to 10 mm.

Example 6

100 g of acrylonitrile copolymer having a viscosity average molecular weight of 176,000 and a chemical composition of 83.8% acrylonitrile and 16.2% vinyl acetate, in the cylinder of the extruder, which is composed of a cylinder, a piston and a slit die extruder, and is sealed and heated insulated. The mixture was mixed with 20 g of water and squeezed and heated to 165 ° C. while fully pressurized at 5 kg / cm 2, and maintained at 135 ° C. again. Then, the piston was operated to apply a pressure of 55 kg / cm 2. The continuous extrudate on tape is wound at a speed of 2.4 m per minute by extrusion through a slit die having a thickness / width / length of 0.25 mm / 20 mm / 3 mm. This continuous extrudate is maintained at 140 ° C. and is subjected to a 43% stretch heat treatment by passing under tension between the rollers under compression. X-ray analysis showed that the stretch heat treated tape-like extrudate had fibrous crystals and had a molecular orientation of 86%. The stretch-treated heat-extruded continuous extruded tape was thinly divided in the longitudinal direction to make long fibers, and the mechanical properties thereof were measured. As a result, tensile strength of 5.3 g / denier, elongation 12%, and tensile modulus of 72 g / denier were shown.

The stretch heat treated tape-like continuous extrudate is cut to a length of 15 mm and beaten with a beater to prepare pulp short fibers. The prepared short fibers have a thickness distribution of 0.1 μm to 40 μm and a length distribution of 1 mm to 15 mm.

Example 7

100 g of acrylonitrile copolymer having a viscosity average molecular weight of 126,000 and a chemical composition of 89.5% acrylonitrile and 10.5% styrene in the cylinder of the extruder, which is composed of a cylinder, a piston and a slit die-type extruder The mixture was mixed with 21 g of water and squeezed at 5kg / cm 2 and heated to 170 ° C to completely melt it.Then, the temperature was lowered to 142 ° C, and the piston was operated to apply a pressure of 55kg / cm 2. Extrude through a slit die with a width / length of 0.3 mm / 20 mm / 4 mm to wind the continuous extrudate on tape at a speed of 2 m per minute. This continuous extrudate is maintained at 155 ° C. and is subjected to 30% stretch heat treatment by passing under tension between the rollers under compression. X-ray analysis showed that the stretch heat treated tape-like extrudate had fibrous crystals and had a molecular orientation of 87%. The continuous extruded tape was thinly divided in the longitudinal direction to make long fibers, and the mechanical properties thereof were measured. As a result, tensile strength of 4.8 g / denier, elongation 12%, and tensile elastic modulus 82 g / denier were shown.

Example 8

Acrylonitrile copolymer with a viscosity average molecular weight of 112,000 and a chemical composition of 87.1% acrylonitrile and 12.9% methylacrylate in the cylinder of an extruder, which is composed of a cylinder, a piston and a slit die extruder and is capable of sealing and heating insulation. The mixture of 100 g and 18 g of water was chopped and heated to 170 ° C. under a pressure of 5 kg / cm 2 and completely melted. Then, the temperature was lowered to 140 ° C. and the piston was operated to maintain a pressure of 50 kg / cm 2. The tape-like continuous extrudate is wound at a speed of 2 m per minute by extrusion through a slit die having a thickness / width / length of 0.20 mm / 20 mm / 3 mm into a normal temperature atmospheric atmosphere. This continuous extrudate is maintained at 145 ° C. and is subjected to a 40% stretch heat treatment by passing under tension between the rollers under compression. X-ray analysis showed that the stretch heat treated tape-like extrudate had fibrous crystals and showed a molecular orientation of 90%. The stretched heat-treated continuous extruded tape was thinly divided in the longitudinal direction to make long fibers, and the mechanical properties thereof were measured. As a result, tensile strength of 6.3 g / denier, elongation 10%, and tensile elastic modulus 83 g / denier were shown.

Example 9

For comparative experiments, a mixture of 22 g of water and 100 g of acrylonitrile copolymer having a viscosity average molecular weight of 102,000 and a chemical composition of 92.8% acrylonitrile and 7.2% methyl acrylate in the same extruder cylinder as in Example 1 And squeezed at 5kg / ㎠ and melted completely by heating to 175 ℃, then operating the piston as it is, and applying pressure of 60kg / ㎠, through a slit die having a thickness / width / length of 0.25mm / 20mm / 3mm. Extrusion to ambient temperature and atmospheric pressure results in continuous foam extrudate with high foaming. This foam showed no orientation at all in the X-ray rotation pattern, and pulp-like short fibers could not be produced.

Example 10

For comparative experiments, a mixture of 22 g of water and 100 g of acrylonitrile copolymer having a viscosity average molecular weight of 102,000 and a chemical composition of 92.8% acrylonitrile and 7.2% methyl acrylate in the same extruder cylinder as in Example 1 And squeezed at 5kg / ㎠ and melted completely by heating to 175 ℃, and then operating the piston as it is, applying a pressure of 30kg / ㎠, through a slit die having a thickness / width / length of 0.25mm / 20mm / 3mm. Extrusion into a pressure chamber at room temperature of 2 kg / cm 2 wound the continuous extrudate on tape at a rate of 5 m per minute. X-ray analysis shows that the tape-like extrudate shows a degree of orientation of 56%, but this does not produce pulp-like short fibers.

Claims (14)

A mixture of acrylonitrile homopolymer or copolymer having a viscosity average molecular weight of 10,000 to 600,000 and having a weight average of 70% or more and acrylonitrile of 70% or more, and mixing water of 5% to 100% by weight The mixture is heated under the seal to above the melting temperature to form an amorphous melt, which is cooled below the melting temperature to obtain a supercooled melt phase, which is then extruded through a straight extrusion port into the external environment at a temperature between the melting temperature and the solidification temperature Obtained extrudate exhibiting a fibrous crystal structure and orientation of 70% or more in an x-ray diffraction pattern having a cross-sectional structure in which plate-like fibrils formed by solidification while being automatically removed by water are arranged in an x-ray diffraction pattern. Tensile forces are applied between the maintained hot gas atmosphere or between the hot compression rollers. After stretching and heat-treating in a state, it is characterized by mechanically beating the pulp-like short fibers of the highly oriented fibril structure having a distribution between 0.1 μm and 100 μm in thickness and a distribution between 0.1 mm and 100 mm in length. How to manufacture. The method of claim 1, wherein the highly oriented fibrillated structure is formed of microfibrils between 0.01 μm and 1.0 μm thick and plate-like fibrils between 1 μm and 10 μm thick, and exhibits a fibrous crystal structure and orientation of 70% or more. A method for producing pulp-like short fibers. The method for producing pulp-like short fibers according to claim 1, wherein the plate-like fibrils have a thickness of between 1 μm and 10 μm, which in turn consist of a number of microfibrils between 0.01 μm and 1.0 μm thick. The method for producing pulp-like short fibers according to claim 1, wherein the stretching heat treatment is performed between 120 ° C and 200 ° C. The method for producing pulp-like short fibers according to claim 1, wherein the stretching heat treatment involves stretching of 5% to 100%. The method for producing pulp-like short fibers according to claim 1, wherein the hot gas atmosphere is made of a gas which hardly undergoes chemical reaction with an acrylonitrile polymer such as water vapor, air, nitrogen, argon, and the like. The pressure of 5 atm or less according to claim 1, wherein the external environment is less than 100 ° C., a gas of 5 atm or less, or a natural vapor pressure atmosphere of 100 to 150 ° C., or a vertical tube filled with a molten alloy having a melting point of less than 100 ° C. A method for producing pulp-like short fibers, which is in an applied state. The method for producing pulp-like short fibers according to claim 1 or 7, wherein the external environment is at room temperature, atmospheric pressure, and air atmosphere. The method for producing pulp-like short fibers according to claim 1, wherein the supercooled melt phase is formed between the melting temperature and the solidification temperature of the polymer water content. The method of claim 1, wherein the mixture comprises between 10% and 50% water by weight relative to the polymer. The method for producing pulp-like short fibers according to claim 1, wherein the amorphous melt is made in a temperature range of not less than the melting temperature of the polymer water to 220 ° C. The acrylonitrile homopolymer or airborne copolymer of claim 1, wherein the microfibrils and the plate-like fibrils are composed of acrylonitrile having a weight ratio of 70% or more and copolymerizable monomers of 30% or less, and have a viscosity average molecular weight of 10,000 to 600,000. Method for producing pulp-like short fibers, characterized in that composed of coalescence. The method for producing pulp-like short fibers according to claim 1 or 12, wherein the viscosity average molecular weight of the acrylonitrile homopolymer and copolymer is between 50,000 and 350,000. The method for producing pulp-like short fibers according to claim 1 or 12, wherein the acrylonitrile homopolymer and the copolymer are composed of acrylonitrile with a weight ratio of 85% or more and a copolymerizable monomer with a weight ratio of 15% or less.

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