JPH09241917A - Production of discontinuous fibrillated fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a discontinuous fibrillated fiber by which the highly fibrillated discontinuous fibrillated fiber can be produced by operations at a low temperature under a low pressure and the discontinuous fibrillated fiber of especially a polymer having a relatively high glass transition temperature or a polymer undergoing the thermal deterioration can further be produced. SOLUTION: A polymer solution prepared by dissolving a high-molecular polymer having film-forming properties in a solvent is passed through a spinneret orifice and extruded into a mixing cell 5 and a coagulant fluid for the high- molecular polymer (preferably in a vapor-phase state) is simultaneously jetted into the mixing cell 5 so as to make the fluid flow in the discharging line direction of the polymer solution. The high-molecular polymer is coagulated in a shearing flow velocity in the mixing cell 5 and formed into a discontinuous fibrillated fiber, which is then extruded from the mixing cell 5 together with the solvent and coagulant fluid.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing discontinuous fibrillated fibers from a polymer solution prepared by dissolving a high molecular polymer in a solvent.

[0002]

2. Description of the Related Art Discontinuous fibril fibers, as represented by pulp, are preferably used as a raw material for obtaining a sheet-like material such as a yarn or a nonwoven fabric. In recent years, ultrafine fibers having a high surface area have been effectively used in fields such as air filters that require high filtration performance with low pressure loss. Further, the use of fibrillated fibers has been proposed to increase surface area and filtration efficiency.

A number of methods have been known so far for producing such discontinuous fibril fibers usefully used as materials such as nonwoven fabrics and papers. For example, in Japanese Examined Patent Publication No. 35-11851, when a polymer solution is discharged into a coagulation bath to precipitate and solidify the polymer, the polymer particles in the swollen state or the fibrous material in the swollen state are deformed by an appropriate shearing action. Alternatively, a method of obtaining a pulp-like material containing fibril fibers by beating has been proposed. As a method of shearing, it is disclosed that water is scraped or a stirrer having an angle on the rotating surface of the blade is stirred at high speed, or that the polymer solution and air are simultaneously discharged from a two-fluid nozzle into a coagulation bath. The resulting pulp is fibrous with a large number of tentacle-like protrusions with a minimum dimension not exceeding 10 microns,
It is a thin film-shaped or ribbon-shaped structure and is not sufficiently morphologically controlled as a fibrillar fiber structure.

A method for producing a continuous yarn (plexifilament) of innumerable fibril fibers is disclosed in JP-A-40-2.
It is well known that there are flash spinning methods disclosed in 8125 and JP-A-41-6215. In this spinning method, a crystalline polymer solution that is at a temperature higher than the normal boiling point of the solvent and is under a high vapor pressure range or higher is generated from an appropriately shaped orifice into a low pressure range. Causes the solvent to evaporate violently,
Moreover, a large number of the extruded polymers are torn to form continuous fibril fibers. Since this method requires instantaneous evaporation of the solvent, it is necessary to use a relatively low boiling point solvent such as benzene, toluene, cyclohexane, methylene chloride, etc. It is necessary to select a polymer which forms a uniform solution with a solvent and which is a non-solvent when the solvent is extruded into the low pressure region, and the fibrillar fiber composition obtained is limited. Moreover, this method cannot be said to be an industrially superior method such as the use of a low boiling point solvent and the maintenance of a high temperature and high pressure state. Furthermore, the obtained fiber is a continuous yarn and forms a discontinuous fibrillated fiber. Is a difficult method.

As a method for producing discontinuous fibers, Japanese Patent Publication No.
Improvement techniques for flash spinning have been proposed in JP-A-8-1416, JP-B-54-39500, and JP-A-6-207309. Japanese Examined Patent Publication No. 48-1416 discloses a method of obtaining a fibrillated fiber by extruding an aqueous dispersion solution obtained by dispersing a large amount of water in a molten polymer together with additional water into a fibrillated fiber. Dispersing in a polymer requires an extruder with a special structure, which is not easy. Japanese Patent Publication No. 54-39500 proposes to discontinue fibers by cutting a continuous fibril fiber obtained by rapidly releasing pressure of a two-phase liquid mixture of a molten polymer and a solvent by a steam flow to obtain discontinuous fibril fiber. It is a thing. Further, Japanese Patent Application Laid-Open No. 6-207309 discloses a method of bringing a flash-spun fiber into contact with an inert fluid and optimizing the volume flow rates of the inert fluid and the solvent vapor to discontinue. However, these methods still require operation under high pressure. As a method for reducing this high pressure, JP-A-51-19490
In addition, a solution of a thermoplastic polymer and a solvent is formed at a pressure lower than the critical co-dissolution pressure and a temperature lower than the critical co-dissolution temperature, and an emulsion containing the above solution as a dispersoid and water as a dispersion medium is compressed using a two-fluid nozzle. A method of spraying in a low pressure region together with a volatile gas has been proposed. Although under the low pressure of this method, it is necessary to maintain the emulsion under a pressure of about 10 to 20 atm.

As a method for producing a pulp-like material which does not require handling under high pressure, JP-A-61-2912 discloses a method in which an aromatic polyamide is dissolved in sulfolane and the solution is heated under a high-temperature gas under a condition of generating a shearing force. There has been proposed a method for producing a pulp-like substance, which is characterized in that it is dispersed using. A two-fluid nozzle is used for this method, and water is proposed as a high-temperature gas. However, the viscosity of the polymer solution that can be used is 10 cP to 10 ⁵ cP, which is lower than the viscosity of the polymer solution that is generally used for fiber solution spinning, and it cannot be said that it is a method that can be used for general-purpose polymers. . Further, the obtained substance is also a pulp-like substance, which is not suitable for a nonwoven fabric used for a filter application or the like.

Further, Japanese Patent Application Laid-Open No. 2-234909 proposes a method for producing a sub-denier fiber from a liquid-repellent liquid crystal polymer. This method involves extruding an optically anisotropic polymer solution into a chamber, introducing a pressurized gas into the chamber, and directing the gas in the chamber in the flow direction and around the flow while contacting it. Both the gas and the flow pass through the gap into the lower pressure zone and pass through it at a rate sufficient to break it into fibers and contact the split stream in the zone with the coagulating fluid. It is a thing. This method requires passing the high-viscosity polymer solution discharged from the extrusion port further into the gap, and the gap of the gap is easily clogged with the polymer solution, which is not an industrially superior method.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an industrially advantageous method for more highly fibrillated discontinuous fibrillated fibers. That is, it is possible to produce highly fibrillated discontinuous fibrillated fibers by operating at low temperature and low pressure, and further, a polymer having a relatively high glass transition temperature or a heat-denatured polymer which cannot be obtained by conventional techniques. The present invention provides a method for producing discontinuous fibrillated fibers of a high molecular weight polymer subjected to the above.

[0009]

The gist of the present invention is to extrude a polymer solution in which a polymer having a film-forming ability is dissolved in a solvent into a mixing cell through a spinneret orifice and simultaneously The combined coagulant fluid is jetted into the mixing cell so as to flow in the discharge line direction of the polymer solution, and the high molecular polymer is solidified in the mixing cell at a shear flow rate to form discontinuous fibrillated fibers. Then, the fibrillated fiber is extruded from a mixing cell together with a solvent and a coagulant fluid, which is a method for producing a discontinuous fibrillated fiber. In the present invention, more preferably, the problem of the present invention can be solved more effectively by using a gas phase fluid as the coagulant fluid.

"Discontinuous fibrillated fiber" as referred to in the present invention.
Is a submicron order (about 0.01 micron) to a micron order (2
It means a fiber having a structure in which a myriad of fine fibers each having a thickness of 0 micron) are branched and an aggregate thereof, and the length of the fiber is several micron (about It is in the range of 1 micron to a few centimeters (about 10 centimeters). These fibril fibers provide a suitable form for the production of nonwovens and synthetic papers by conventional methods.

The polymer having a film-forming ability which can be used in the present invention is not particularly limited as long as the polymer solution can be prepared by using an appropriate solvent. The state of the polymer solution includes a two-phase separation solution, a liquid crystal solution, a gel-like solution and the like, and represents a solution in a broad sense. Such high molecular weight polymers include cellulose, cellulose ester, polyacrylonitrile, polyolefin, polyvinyl chloride, polyurethane,
Examples thereof include homopolymers or copolymers such as polyester. In particular, a polymer having a relatively high glass transition temperature, a polymer which is susceptible to thermal denaturation, cellulose, cellulose acetate, polyacrylonitrile, polyvinyl chloride, etc. can be used more advantageously than conventional methods. The solvent that can be used is not particularly limited, and it is possible to use from low boiling point solvents to high boiling point solvents, and those having compatibility with water are particularly advantageous in effectively performing washing after fiber formation. It is also possible to use a mixture of two or more kinds of solvents, use a blended solution of two or more kinds of high molecular polymers, use together various additives, and add a coagulant in advance. The concentration, viscosity, and temperature of the high molecular weight polymer in the polymer solution can be appropriately set depending on the type of high molecular weight polymer used and the solvent, but it is generally used when spinning fibers by various solution spinning methods. The conditions can be used. The polymer solution can be easily prepared by a generally known method.

First, the case where cellulose is used as the high-molecular polymer having film-forming ability of the present invention will be described in detail below. The cellulose material used in the present invention can be selected from dissolving pulp, pulp floc, and the like. These pulps may contain hemicellulose, lignin and the like. Among these, it is preferable to use pulp having an α-cellulose content of 90% by weight or more.

The pulp used as the cellulosic material may be in the form of sheet or powder.
The sheet-like material may be made into a chip-like shape with a cutting machine such as a shredder. Further, the pulp may be pulverized into particles as long as the molecular weight of cellulose is not significantly reduced.

When cellulose is used as the high molecular weight polymer capable of forming a film, the solvent used in the present invention is N-methylmorpholine-N-oxide and N-methylmorpholine-N-oxide.
-Methylmorpholine-N-oxide A mixed solvent composed of a solvent (hereinafter referred to as a non-solvent) capable of being uniformly mixed and incapable of dissolving cellulose. here,
Water is preferably used as the non-solvent. In addition, as a solvent of cellulose, a mixed solvent of nitrodiene dioxide (N ₂ O ₄ ) / dimethylformamide (DMF), a mixed solvent of paraformaldehyde ((CH ₂ O) x) / dimethyl sulphoxide (DMSO), chloride A mixed solvent of lithium (LiCl) / dimethylacetamide (DMAC) and the like can also be used.

N-methylmorpholine-N in mixed solvent
-Oxide is used as a solvent that dissolves cellulose, but in some cases, Japanese Examined Patent Publication No. Sho 55-41691,
JP-B-55-46162 and JP-B-55-4169
3 (or corresponding US Pat. No. 4,211,574,
Other tertiary amine oxides described in Nos. 4142913 and 4144080) can be used in combination with N-methylmorpholine-N-oxide. In this case, N-methylmorpholine-N-is particularly preferable as the other tertiary amine oxide that can be used in combination.
It is a cyclic mono (N-methylamine-N-oxide) compound similar to oxide, and examples thereof include N-methylpiperidine-N-oxide and N-methylpyrrolidone-N-oxide.

The preferred non-solvent for cellulose used in the present invention is water, but a mixed solvent of water and an alcohol such as methanol, n-propanol, isopropanol or butanol may be used. Further, any aprotic organic solvent such as toluene, xylene, dimethylsulfoxide, dimethylformamide, dimethylacetamide and the like is used as a cellulose non-solvent if it does not chemically react with N-methylmorpholine-N-oxide or cellulose. be able to.

Further, a stabilizer can be added to the mixed solvent. Most preferred as such a stabilizer is propyl gallate, which is disclosed in JP-B-3-29819.
Other gallic acid esters described in US Pat. No. 4,426,228 (eg corresponding US Pat. No. 4,426,228), such as methyl gallate, ethyl gallate, isopropyl gallate, etc. may be used. In addition, glycerin aldehyde, L-ascorbic acid, isoascorbic acid, triose lectductone,
Also, a compound having a compound structure in which a double bond is adjacent to a carbonyl group such as reductic acid can be used as a stabilizer. Further, ethylenediaminetetraacetic acid and the like can also be used as a stabilizer of the cellulose molding solution of the present invention. Further, as the inorganic compound, calcium pyrophosphate, calcium chloride, ammonium chloride, etc. described in US Pat. No. 4,880,469 can be used as a stabilizer of the cellulose molding solution of the present invention.

In the present invention, the cellulose polymer solution can be prepared either continuously or batchwise. That is, the dissolution may be continuously adjusted using a screw type extruder or the like, or the batch dissolution may be adjusted using a tank type kneader equipped with a heating means and a reduced pressure deaeration means. The melting temperature of the cellulose composition is not particularly limited, but is 90 to 120.
It is preferably carried out in the range of about ° C. If the melting temperature is too high, the degree of polymerization may be lowered due to the decomposition of cellulose and the decomposition and coloring of the solvent may be remarkable, and if it is too low, the dissolution may be difficult.

The total concentration of the cellulose composition in the cellulose polymer solution of the present invention is preferably 30% by weight or less. Considering the moldability of the cellulose molding solution and the productivity of the molded product, the cellulose composition is The composition concentration is 6 to
It is preferably in the range of 25% by weight. Further, the content of N-methylmorpholine-N-oxide in the mixed solvent used for the cellulose forming solution, and the content of the solvent that is a non-solvent of cellulose and that can be mixed with N-methylmorpholine-N-oxide is: Preferred are 48 to 90% by weight and 5 to 22% by weight, respectively. When water is used as the non-solvent for cellulose, the proportion of water is set to a large value of 20 to 50% by weight in the step of adding the cellulose composition to the mixed solvent, and then the water is removed under reduced pressure heating. ,
It is preferable to adjust the proportion of water to 5 to 22% by weight.

Next, the case where cellulose ester is used as the high molecular polymer having film forming ability of the present invention will be described. The cellulose acetate used in the present invention may be cellulose triacetate having an acetylation degree of 56.2% to 62.5%, or cellulose diacetate having an acetylation degree of 48.8% to 56.2%.

As a solvent of cellulose acetate, a single solvent such as methylene chloride or acetone, or a mixed solvent of methylene chloride and methanol is used. To prepare a polymer solution of cellulose acetate, flakes of cellulose triacetate or cellulose diacetate are dissolved in a single solvent such as methylene chloride or acetone or a mixed solvent such as methylene chloride and methanol to adjust the solution concentration to 15 to
A spinning dope containing 30% by weight, preferably 18 to 27% by weight, is prepared.

When the film-forming high molecular weight polymer of the present invention is a polyacrylonitrile-based polymer, the acrylonitrile-based polymer is not particularly limited as long as it is a polymer that constitutes an ordinary acrylic fiber, As the monomer composition, those containing 50% by weight or more of acrylonitrile are preferably used.

As a copolymer component of acrylonitrile,
There is no particular limitation as long as it is a copolymerization monomer that constitutes a normal acrylic fiber, and examples thereof include the following monomers. That is, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate,
Acrylic esters represented by 2-ethylhexyl acrylate, 2-hydroxyl ethyl acrylate, hydroxypropyl acrylate, etc., methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate. , T-butyl methacrylate, n-hexyl methacrylate, cyclohexyl acrylate, lauryl acrylate,
Methacrylic acid esters represented by 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, diethylaminoethylethyl methacrylate, etc., acrylic acid, methacrylic acid, maleic acid, itaconic acid, acrylamide, N-methylol acrylamide, diacetone acrylamide, It is an unsaturated monomer such as styrene, vinyltoluene, vinyl acetate, vinyl chloride, vinylidene chloride, vinylidene bromide, vinyl fluoride and vinylidene fluoride. Further, for the purpose of improving dyeing, p-sulfophenyl methallyl ether, methallyl sulfonic acid, allyl sulfonic acid, styrene sulfonic acid, 2-acrylamide-
You may copolymerize 2-methyl propane sulfonic acid, these alkali metal salts, etc.

The molecular weight of the acrylonitrile polymer used in the present invention is not particularly limited, but a molecular weight of 100,000 or more and 1,000,000 or less is desirable. If the molecular weight is less than 100,000, the spinnability tends to decrease, and at the same time, the yarn quality of the raw yarn tends to deteriorate. If the molecular weight exceeds 1,000,000, the polymer concentration that gives the optimum viscosity of the spinning dope will be low, and the productivity will tend to be low.

The solvent used in the case of the acrylonitrile-based polymer is not particularly limited as long as it is a common solvent that dissolves each polymer of the acrylonitrile-based polymer and the acrylic resin-based polymer. Examples thereof include dimethylformamide, dimethylacetamide, dimethylsulfoxide, rhodanate, nitric acid and the like.

Polyester may also be used as the high molecular weight polymer of the present invention capable of forming a film. In this case, polyester having ethylene terephthalate as a main repeating unit is preferably used. This polyester is typically a polyester having terephthalic acid or an ester-forming derivative thereof as a dicarboxylic acid component and ethylene glycol or an ester-forming derivative thereof as a glycol component. Or a part of the glycol component may be replaced with another glycol component.

Other dicarboxylic acid components include isophthalic acid, monoalkali metal salts of 5-sulfoisophthalic acid,
Dicarboxylic acids such as naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, adipic acid, sebacic acid and 1,4-cyclohexanedicarboxylic acid or esters thereof, and p-oxybenzoic acid, p
And oxycarboxylic acids such as -β-oxyethoxybenzoic acid and esters thereof.

As other glycol components, 1,
4-butanediol, alkylene glycol having 2 to 10 carbon atoms, 1,4-cyclohexanedimethanol, neopentyl glycol, 1,4-bis (β-oxyethoxy) benzene, bisglycol ether of bisphenol A, polyalkylene glycol, etc. Is mentioned.

Further, within the range where the polyester is substantially linear, polycarboxylic acids such as trimellitic acid and pyromellitic acid, polyols such as pentaerythritol, trimethylolpropane and glycerin, monohydric polyalkylene oxide and phenyl. It does not matter even if a polymerization terminator such as acetic acid is used.

The polyester may be synthesized by any known method. For example, in the case of polyethylene terephthalate, terephthalic acid and ethylene glycol are directly esterified, a lower alkyl ester of terephthalic acid such as dimethyl terephthalate is transesterified with ethylene glycol, or terephthalic acid is ethylene oxide. To synthesize a glycol ester of terephthalic acid and / or a low polycondensate thereof, followed by polycondensation of the product by a conventional method. Further, in synthesizing the polyester in the present invention, a known catalyst,
An antioxidant, a coloring inhibitor, an ether bond by-product inhibitor, a flame retardant, and other additives may be appropriately used.

As a solvent when such a polyester is used, m-cresol, trifluoroacetic acid, O-
Examples include a single solvent such as chlorophenol, a mixed solvent such as trichlorophenol and phenol, and tetrachloroethane and phenol.

In the same manner, in addition to the above, as the high molecular weight polymer having film forming ability, polyolefin-based polymers such as polyethylene, polypropylene and their copolymers, polyvinyl chloride, polyvinyl fluoride and their co-polymers. Vinyl-based polymers such as coalesced can be used.

In this case, the solvent includes aliphatic hydrocarbons such as pentane, hexane, heptane and octane, alicyclic hydrocarbons such as cyclohexane, aromatic hydrocarbons such as benzene and toluene, chlorinated solvents such as methylene chloride, Alcohols, ketones, ethers, esters, and mixed solvents thereof can be used.

The polymer solution thus obtained is extruded into the mixing cell through the spinneret orifice by a pump or an extruder for extruding a highly viscous solution which is usually used in industry. The diameter of the spinneret orifice is generally suitable for spinning a polymer solution, and is appropriately set in the range of several tens of microns (20 microns) to several millimeters (2 mm). The shape of the die is not particularly limited, but it is also possible to eject from a circular orifice or to eject from a plurality of die to the mixing cell. At the same time as the polymer solution is extruded, the coagulant fluid of the polymer is jetted into the mixing cell so as to flow in the discharge line direction of the polymer solution. The coagulant fluid can be appropriately selected depending on the polymer to be used, but industrially water is predominantly used. Further, in order to obtain a sufficient shear flow velocity, it is more effective that the coagulant fluid is in the gas phase, that is, when the coagulant fluid is water, by utilizing steam, the fiber of the present invention can be obtained. A shear rate sufficient to obtain can easily be obtained.

In the present invention, in order to jet the coagulant fluid so as to flow in the discharge line direction of the polymer solution, the angle formed by the jet line direction of the coagulant fluid and the discharge line direction of the polymer solution is 0 degree or more, It is preferable to set the angle to be less than 90 degrees. When the angle between the ejection line direction of the coagulant fluid and the ejection line direction of the polymer solution is in the above range, the fibrillated fiber to be formed, the solvent of the high molecular polymer, and the mixed solution of the coagulant are immediately mixed. It is possible to discharge from the outlet. Furthermore, in order to improve the degree of fibrillation and give a suitable shape to the base fiber of the non-woven fabric used for filter applications, etc., the angle formed by the jet line direction of the coagulant fluid and the jet line direction of the polymer solution Should be set in the range of 20 to 80 degrees, and more preferably 30 to 70 degrees. By discharging both liquids within this range, the polymer solution and the coagulant fluid that are discharged into the mixing cell are sufficiently mixed, and the mixed solution of the polymer solution and the coagulant fluid immediately becomes a shear flow, and the mixing cell is discharged. By passing through it, it becomes possible to obtain fibers with advanced fibrillation. When the ejection line direction of the coagulant fluid and the ejection line direction of the polymer solution are parallel to each other, that is, when the angle between them is 0 degree, the polymer solution and the coagulant fluid are not sufficiently mixed, but they are sufficiently long. Although it is possible to form a partially fibrillated fiber by providing a mixing cell having a ridge, the fiber has an elliptic to a film-like cross section. Conversely, when the angle exceeds 90 degrees, the polymer solution and the coagulant fluid are sufficiently mixed, but the coagulated high-molecular polymer tends to clog the mixing cell.

The polymer solution and the coagulant fluid must be ejected and ejected so that they are sufficiently mixed. As described above, the angle between the ejection line direction of the polymer solution and the ejection line direction of the coagulant fluid is adjusted. In addition to the above, it is preferable to use a nozzle capable of contacting both the polymer solution discharge port and the coagulant fluid jet port. The coagulant fluid ejection port can be ejected from a circular-cylindrical slit or a plurality of capillaries, but it is preferable to have a slit structure in order to bring the coagulant fluid into uniform contact with the polymer solution. The thickness of the slit is not particularly limited, but can be set within a range of about several tens of microns (20 microns) to 1 millimeter. The amount of the coagulant fluid jetted out is advantageous from the industrial point of view when the coagulant fluid in the vapor phase preferably used in the present invention is used, and in this case, the slit thickness is in the vapor phase state. It is a factor that changes the flow rate of the coagulant fluid, and is rather set for the purpose of controlling the flow rate of the coagulant fluid in the gas phase in obtaining the discharge amount of the polymer solution and the desired discontinuous fibril fiber morphology. The angle between the ejection line of the coagulant fluid and the ejection line of the polymer solution is adjusted by adjusting the angle of the slit.

The coagulant fluid can be jetted from the circumference or inside of the polymer solution discharge line as long as it satisfies the requirements of the present invention. The polymer solution discharged into the mixing cell is mixed with the coagulant fluid in the mixing cell and coagulated by the coagulant. The coagulation in the present invention means the substitution of the coagulant with the minimum solvent that allows the fibrillar fiber to be formed from the polymer solution, and the coagulated fibrillated fiber also includes the gel state containing the solvent. . Thus, the coagulated high molecular weight polymer further coagulates in the mixing cell under a shear flow rate, and is shaped into discontinuous fibrillated fibers swollen with a coagulant or a solvent.

The term "mixing cell" as used in the present invention means a point where the polymer solution is solidified and sheared by mixing the polymer solution and the coagulant fluid, and specifically, the position where the polymer solution and the coagulant fluid are in contact with each other. Is a gap having a certain length (about 1 millimeter or more) provided in the lower part from. The length of the mixing cell depends on the discharge rate of the polymer solution and the discharge rate of the coagulant fluid,
It needs to be appropriately set according to the desired fibrillated fiber morphology, but the length and shearing are sufficient to ensure the time required for the high molecular polymer to be coagulated into a fiber morphology. It suffices that the length is sufficient to form branched fibril fibers, generally about 1 mm or more, preferably 10 mm or more, more preferably 30 mm.
mm or more. If the length of the mixing cell is increased, the average denier of the fiber obtained will be smaller, and the proportion of branched fibril fibers will also increase, but if it is made longer than necessary, clogging will easily occur due to the fibrillated fibers, and industrial Will be a problem. On the contrary, if the length of the mixing cell is shortened, the average denier of the fiber becomes large, and the number of branched fibrillated fibers also becomes small, which makes it unsuitable as a fiber for use in filters that utilize the excellent adsorption performance of fine fibril fibers. Will be enough. The size of the mixing cell is not particularly limited, but in order to prevent clogging due to the formed fibers, it is preferably 1 mmφ or more in the case of having a cylindrical shape, and 1 mm or more in the case of a rectangular slit. is necessary. In order to obtain the fiber of the present invention, as described later, it is necessary to secure a shear flow rate in the mixing cell, and the size of the mixing cell has an upper limit for obtaining the required shear flow rate.

The linear flow velocity of the coagulant fluid in the mixing cell is an important factor in obtaining the fibrillated fibers of the present invention. The linear flow velocity of the coagulant fluid changes depending on the jetting amount of the coagulant and the size of the mixing cell, but the flow velocity required for the present invention is 100 m / sec. More speed is required. 100 m / sec. In the following, not only is the degree of fibrillation of the formed fibers reduced, which is not preferable, but also clogging in the mixing cell is likely to occur, which is not industrially preferable. On the contrary, if the flow velocity is increased, the fibers are easily fibrillated, which is a suitable form as a fiber base material to be used for the nonwoven fabric used for filter applications, etc., but the flow rate of the coagulant is increased more than necessary to increase the flow velocity. Then, the load in the subsequent steps such as solvent recovery increases, which is not economical. It is also possible to reduce the cross-sectional area of the mixing cell to increase the flow velocity, but as described above, the extreme reduction of the cross-sectional area causes clogging, which is not preferable.

The jetting amount of the coagulant fluid has a role of imparting shear in the mixing cell and, at the same time, of coagulating the high-molecular polymer upon contact with the polymer solution. The appropriate amount of coagulation fluid for sufficient coagulation is the type of polymer, the degree of polymerization, the concentration of polymer in the polymer solution, the discharge amount of the polymer solution,
It is easily expected that the coagulant fluid used in the mixing cell may be changed depending on the type and temperature of the coagulant used. The flow rate of the coagulant fluid is set to ensure the linear flow velocity required to provide sufficient shear to the solution. As shown in the examples of the present invention, when a gas phase coagulant fluid is used as the coagulant fluid, the polymer / coagulant weight ratio is generally in the range of 50 to 400, but is not particularly limited. Absent.

The shape of the mixing cell may be any as long as it has a sufficient length as described above, and the fiber of the present invention can be obtained regardless of the shape of the cross section such as circular or rectangular.
As long as the requirements for the present invention are satisfied, it is possible to reduce the cross-sectional area toward the outlet of the mixing cell, or conversely to increase it, and further round the tip and widen the outlet. When the discharge amount of the polymer solution is changed while keeping the length of the mixing cell constant, the average denier of the fibrillar fibers obtained by increasing the discharge amount becomes thicker, and the number of branched fibril fibers decreases, while the fiber Become longer and longer. On the contrary, when the discharge amount is decreased, the average fiber denier is decreased and the ratio of fibrillated fibers is increased, while the fiber length is decreased. As described above, the average fiber denier and the degree of fibrillation are changed by adjusting the length of the mixing cell, the cross-sectional area, the discharge amount of the polymer solution, the polymer concentration of the polymer solution, and the ejection amount of the coagulant. It is possible to obtain various discontinuous fibrillated fibers.

The discontinuous fibrillated fibers formed in the mixing cell and the dispersion fluid of the solvent and the coagulant fluid are discharged from the mixing cell. The atmosphere to be discharged is the solvent and coagulant used in the fiber of the present invention. Depending on the post-treatment step such as washing and drying or the intended use, it can be appropriately selected, but generally in the gas phase or in the liquid. In many cases, the fibers of the present invention discharged from the mixing cell are in a swollen state due to the solvent, and when directly laminated, the fibril fibers formed in the mixing cell may be fused to each other, impairing the quality of the fibers. For this reason, it is preferable to discharge into the liquid, more preferably into the mixed liquid of the solvent of the polymer and the coagulant in order to complete the coagulation of the fibers in the swollen state and to efficiently perform the post-treatment such as washing. Thus, the fiber of the present invention can be predominantly produced. The dispersion solution of the discontinuous fibrillated fibers thus obtained is extruded from the mixing cell, and the discontinuous fibrillated fibers that have been wet by the washing can be further dried to obtain an aggregate of the discontinuous fibrillated fibers. ,
Further, depending on the polymer, the fiber structure may be fixed by a heat treatment step or the like, if necessary.

[0043]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a general nozzle used in the present invention, but the nozzle shape is not limited as long as it satisfies the requirements of the present invention. For example, a plurality of polymer solution outlets may be provided, or a nozzle in which a plurality of units in which the polymer solution outlets and the coagulant fluid outlets are in a one-to-one correspondence with one mixing cell are used. It is possible to achieve high productivity as long as the requirements of the present invention are satisfied.

1 is a flow path of the polymer solution, 2 is a discharge port of the polymer solution, 3 is an inlet of the coagulant fluid, 4 is a slit of the coagulation fluid, 5 is a mixing cell, and 6 is an outlet of the mixing cell. Show. The line indicates the discharge line direction of the polymer solution, the line indicates the jet line direction of the coagulant fluid, and the angle indicates the angle between them.
FIG. 2 shows a nozzle used in the present invention when the discharge line direction of the polymer solution and the jet line direction of the coagulant fluid are in the same direction, that is, when the angle is 0 degree. There is. FIG. 3 shows a commonly used two-fluid nozzle, which cannot be used in the present invention because of the absence of the mixing cell 5, which is essential in the present invention. Next, the manufacturing method of the present invention will be further described with reference to FIG.

The high molecular weight polymer and the solvent are mixed and dissolved by a mixer or the like. Next, the obtained solution is extruded under nitrogen pressure and a fixed amount is supplied to the nozzle portion shown in FIG. 1 using a gear pump. After passing through the flow path 1 of the polymer solution supplied to the nozzle portion, the polymer solution is extruded from the discharge port 2 into the mixing cell 5.
Further, at the same time when the polymer solution is supplied, the coagulant fluid is supplied from the inflow port 3. The supplied coagulant fluid is slit 4
To the mixing cell 5 and mixed with the polymer solution. In the mixing cell, the high molecular weight polymer solidifies under shear fluid,
The fibers become discontinuous fibrillated fibers and are discharged from the outlet 6. The discontinuous fibril fiber thus obtained is discharged into the gas phase or the liquid phase, and the fiber of the present invention can be obtained by removing the solvent by a known method.

The method for producing discontinuous fibril fibers according to the present invention is carried out after the washing step or at the same time by continuously attaching a known sheet shaping device, shaping the sheet and then drying the sheet by a known method. It can be formed into paper. The recovery of the solvent used can also be achieved by adopting a known method.

[0047]

EXAMPLES The present invention will now be described by way of examples. Example 1 2000 g of N-methylmorpholine N-oxide (manufactured by San Techno Chemical Co.) containing 117 g of cellulose (dissolving pulp V-60 manufactured by P & G Cellulose Co., Ltd.) and about 41% by weight of water and 15 g of propyl gallate.
A mixer with a vacuum degassing device manufactured by Kodaira Seisakusho (ACM-
Type 5) and mix under heating under reduced pressure for about 2 hours 6
48 g of water was dehydrated to prepare a uniform solution of cellulose.
The kettle temperature was maintained at 100 ° C during the melting operation. Next, while keeping the obtained solution at 100 ° C., the solution was extruded under a nitrogen pressure of 1.5 kg / cm ² and was quantitatively supplied to the nozzle portion shown in FIG. 1 using a gear pump. The discharge rate of the cellulose solution was defined by the rotation speed of the gear pump. Steam was used as the coagulant fluid, and the amount of steam supplied was determined by regulating the supply pressure with a pressure reducing valve. The amount of steam was measured by changing the supply pressure from the nozzle shown in FIG. 1 and injecting only steam into water, and determining the weight increment per unit time. The diameter of the cellulose solution discharge port 2 is 0.2 mm, the diameter of the mixing cell part 5 is 2 mm, the length is 54 mm, the coagulant fluid slit opening is 390 μm, and the polymer solution discharge line and the vapor discharge line are The amount of cellulose solution supplied was 6.0 using a nozzle manufactured so that the angle formed by
It was jetted into water at a temperature of 30 ° C. at a flow rate of ml / min and a steam supply pressure of 1.5 kg / cm ² . The steam consumption at this time was 87 g / min in terms of water, and the linear flow velocity of steam in the mixing cell was calculated to be about 800 m / sec. It became.
Cellulose fibers floating in the coagulation liquid were collected, further washed in boiling water for 1 hour or more, and air-dried at room temperature.
The morphology of the side surface of the obtained cellulose fiber was observed using a scanning electron microscope. Furthermore, a projection stereo microscope (profile projector V-
12) was used to observe the morphology in the longitudinal direction of the fiber. The obtained cellulose shaped body is an aggregate of discontinuous fibrillated fibers and has a diameter of about 0.1 μm to 50 μm.
The fiber had a wide distribution in the range of about μm, and the fiber length had a wide distribution of about 5 mm to about 5 cm. In addition, the fiber has a branched structure,
A structure in which fine fibers of several μm or less are branched from the fiber side surface of m was observed. A photograph of the obtained cellulose fiber is shown in FIG.

Example 2 A cellulose solution was prepared in the same manner as in Example 1, and the cellulose was shaped using the nozzle shown in FIG. Supply the amount of cellulose solution to 3.0
(Example 2-1), 12.0 ml / min (Example 2-
2), the composition of the nozzle and the steam supply amount are the same as those in the first embodiment.
The same conditions were set. Electron micrographs of the obtained cellulose fibers are shown in FIGS. 5 and 6. When the discharge rate was reduced, the fibers became thinner on average, and fibrillation proceeded, but the fiber length became shorter. On the contrary, when the discharge amount is increased, the average fiber diameter is increased and the degree of fibrillation is also decreased. By changing the discharge flow rate, changes in average fiber diameter and fibril shape were observed.

Example 3 A cellulose solution was prepared in the same manner as in Example 1, and the cellulose was shaped using the nozzle shown in FIG. Table 2 shows the observation results of the morphology of the obtained cellulose fiber when the length of the mixing cell 5 was changed to 14 mm (Example 3-1) and 104 mm (Example 3-2). The supply amount of the cellulose solution and the supply amount of steam were set to the same conditions as in Example 1. It is observed that as the length of the mixing cell is lengthened, the fibers become thinner and branched fibrils develop. Electron micrographs of the obtained fibers are shown in FIGS. 7 and 8.

Example 4 A cellulose solution was prepared in the same manner as in Example 1, and the nozzle shown in FIG. 1 was used in which the length of the mixing cell was 1.5 mm and the slit opening of the coagulant fluid was 250 μm. I was there. Cellulose solution was added at 6 g / min. And steam was used as the coagulant fluid, and the steam supply pressure was maintained at 1.5 kg / cm ² . When the vapor flow rate was measured in the same manner as in Example 1, it was 70 g / min. Met. When the flow velocity of the vapor in the mixing cell in this case is calculated, it becomes about 630 m / sec. When the morphology of the obtained cellulose fiber was observed, the fiber diameter was large, and only a partially fibrillated fiber was observed. An electron micrograph of the obtained fiber is shown in FIG.

Example 5 Cellulose fibers were shaped in the same manner as in Example 1 except that the cellulose solution was prepared in the same manner as in Example 1 and the diameter of the mixing cell was 4 mmφ. When the amount of steam used at this time was measured by the same method as in Example 1, it was 85 g / min. Met. Approximately 190 m /
sec. The morphology of the obtained cellulose fiber was observed, and it was found that a fiber having a morphology similar to that of Example 1 was obtained. An electron micrograph of the obtained fiber is shown in FIG.

Example 6 Using the polymer solution used in Example 1, from the polymer solution discharge port of the nozzle shown in FIG.
A capillary with a diameter of 0.2 mm is extended by 1.5 mm so that the discharge line of the polymer solution and the discharge line of the coagulant fluid are parallel to each other, and a mixing cell with a diameter of 2 mmφ and a length of 13 mm is provided in FIG. Spinning was performed under the same conditions as in Example 1 except that a nozzle having the structure shown was used. The shaped product obtained from the outlet of the polymer solution had some fibrillated fibers, but the cross-sectional shape of the fiber was elliptic to film-like. An electron micrograph of the fiber is shown in FIG.

[Comparative Example 1] The same as Example 1 except that the polymer solution used in Example 1 was used and the nozzle having the structure shown in FIG. 3 from which the mixing cell portion of the nozzle shown in FIG. 2 was removed was used. Spinning was performed under various conditions. The obtained shaped body was a fiber or film having an oval cross section without branching. An electron micrograph of the fiber is shown in FIG.

[Example 7] 230 g of cellulose diacetate (MBH manufactured by Daisei Chemical Industry Co., Ltd.), 2000 g of N-methylmorpholine N-oxide containing about 41% by weight of water and 15 g of propyl gallate were used as in Example 1. While mixing using the same apparatus, 700 g of water was dehydrated to prepare a solution of cellulose acetate. Next, while keeping the obtained solution at 100 ° C., 1.5 kg / cm ²
Extruded under nitrogen pressure of No. 4, and fed to a nozzle similar to that of Example 1 using a gear pump at 4.5 g / min. It was supplied at a constant rate. Further, in the same manner as in Example 1, the pressure was maintained at 1.5 g / cm ² by the pressure reducing valve and the mixture was supplied to the mixing cell. When the supply flow rate of steam was measured by the same method as in Example 1, it was 70 g /
min. Met. It was discharged into a coagulating liquid composed of water in the same manner as in Example 1, the floating diacetate cellulose fibers were collected, thoroughly washed and dried. The obtained fiber had a structure in which finely branched fibers were branched in the same manner as the cellulose shaped body of Example 1, and the length was about 1 to 2 cm.

Example 8 115 g of cellulose used in Example 1 and cellulose diacetate 1 used in Example 4
While mixing 15 g of 2000 g of N-methylmorpholine N-oxide containing about 41% by weight of water and 15 g of propyl gallate using the same apparatus as in Example 1, 7
00 g of water was dehydrated to prepare a mixed solution of cellulose and cellulose diacetate. Spinning was performed under the same conditions as in Example 4 to obtain a fibrillated fiber assembly. The obtained fiber had a thickness of several μm to several tens of μm, and had a structure in which fibril fibers of submicron to 1 μm were branched.

[Example 9] Cellulose diacetate (MBH manufactured by Daicel Chemical Industries, Ltd.) 230 g was added to acetone 77.
It was dissolved in 0 g to prepare a 23 wt% cellulose diacetate acetone solution. While maintaining the solution obtained by using the same nozzle as in Example 1 at 40 ° C., 4.5 ml / m 2
in. Supply steam pressure at the same time as 1 kg /
It was kept at cm ² and steam was ejected into the mixing cell. The flow rate of steam was measured by the same method as in Example 1 and found to be 73 g / m.
It was in. The obtained fiber was washed with water, treated with boiling water, dried with hot air at 80 ° C., and then the fiber morphology was observed by the same method as in Example 1. The obtained fiber was an aggregate of fibril fibers having a thickness of sub μm to 10 μm and a length of several tens μm to several hundreds μm.

Comparative Example 2 While keeping the diacetate-acetone solution prepared in the same manner as in Example 9 at 40 ° C.,
3.6 g / min. Two-fluid nozzle (SPRAYING SY
2.0k from STEMS CO. Setup No. E25A)
It was blown into water at 30 ° C. with steam having a g / cm ² gauge pressure. When the obtained fiber was treated in the same manner as in Example 9 and observed for its morphology, it was a thin film-like aggregate.

[Comparative Example 3] Using an acetate-acetone solution prepared in the same manner as in Example 9, spinning was performed from the nozzle used in Example 1 together with pressurized air having a gauge pressure of 2 kg / cm ² instead of steam. However, the lumpy polymer was only intermittently discharged from the mixing cell, and no fibrillar fiber was obtained.

[Example 10] Acrylonitrile was used as a medium in which ammonium persulfate and sodium sulfite were used as polymerization catalysts for polymerization, followed by washing and drying to obtain a non-viscosity of 0.18.
(0.1g / 100cc DMF solution, measured at 25 ° C)
A polymer containing 100% by weight of acrylonitrile was obtained. 200 g of the obtained polymer was dissolved in 800 g of DMF. Using the same nozzle as in Example 1, this polymer solution was kept at 80 ° C. and the flow rate was 5.2 ml / min. The mixture was discharged into the mixing cell at a speed of. Steam was used as the coagulating fluid, and the supply steam pressure was kept at 1.5 kg / cm ² and jetted into the mixing cell. The vapor flow rate was measured by the same method as in Example 1,
80 g / min. Met. After the obtained fibers were washed and dried, the morphology of the fibers was observed. The obtained fiber was an aggregate of fibril fibers having a thickness of sub μm to 10 μm and a length of several tens μm to several hundreds μm.

[0060]

INDUSTRIAL APPLICABILITY The present invention can efficiently produce an aggregate of fibrillated fibers from a polymer solution having a film-forming ability, and the thus obtained fibrillated fibers and a nonwoven fabric composed of the fibrillated fibers. Sheet-like materials such as the above can be effectively used as fibrillated fibers having a high surface area in fields requiring low pressure loss and high filtration performance, such as air filters. According to the production method of the present invention, by operating the fibrillated fiber at a low temperature and a low pressure, it is possible to produce a highly fibrillated discontinuous fibrillated fiber, which is relatively impossible in the prior art. It is possible to stably produce a discontinuous fibrillated fiber of a high molecular polymer having a high glass transition temperature or a high molecular polymer that undergoes thermal modification, and its industrial significance is great.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a nozzle used in the present invention.

FIG. 2 is a sectional view showing another example of a nozzle used in the present invention.

FIG. 3 is a sectional view of a nozzle used in a comparative example of the present invention.

FIG. 4 is an electron micrograph (× 200) showing an example of the morphology of the discontinuous fibrillated fiber obtained in Example 1 of the present invention.
It is.

FIG. 5 is an electron micrograph (× 200) showing an example of the morphology of the discontinuous fibrillated fiber obtained in Example 2 of the present invention.
It is.

FIG. 6 is an electron micrograph (200) showing another example of the morphology of the discontinuous fibrillated fiber obtained in Example 2 of the present invention.
Times).

FIG. 7 is an electron micrograph (× 200) showing an example of the morphology of the discontinuous fibrillated fiber obtained in Example 3 of the present invention.
It is.

FIG. 8 is an electron micrograph (200) showing another example of the morphology of the discontinuous fibrillated fiber obtained in Example 3 of the present invention.
Times).

FIG. 9 is an electron micrograph (× 200) showing an example of the morphology of the discontinuous fibrillated fiber obtained in Example 4 of the present invention.
It is.

FIG. 10 is an electron micrograph (200 showing an example of the morphology of the discontinuous fibrillated fiber obtained in Example 5 of the present invention.
Times).

FIG. 11 is an electron micrograph (200 showing an example of the morphology of the discontinuous fibrillated fibers obtained in Example 6 of the present invention.
Times).

FIG. 12 is an electron micrograph (× 200) showing the morphology of the fibers obtained in Comparative Example 1.

[Explanation of symbols]

 1: Flow path of polymer solution 2: Discharge port of polymer solution 3: Inflow port of coagulant fluid 4: Slit of coagulant fluid 5: Mixing cell 6: Outlet of mixing cell: Discharge line of polymer solution: Coagulation Spray line of agent fluid: Angle formed by

Claims (3)

[Claims] 1. A polymer solution prepared by dissolving a polymer capable of forming a film in a solvent is extruded into a mixing cell through a spinneret orifice, and at the same time, a coagulant fluid of the polymer is added to the polymer solution. It is jetted into the mixing cell so as to flow in the discharge line direction, the high molecular polymer is coagulated in the mixing cell at a shear flow rate to form discontinuous fibrillated fibers, and the fibrillated fibers are coagulated with the solvent and coagulation. A method for producing discontinuous fibrillated fibers, which comprises extruding from a mixing cell together with an agent fluid. 2. The method for producing discontinuous fibrillated fibers according to claim 1, wherein the coagulant fluid is in the gas phase. 3. The method for producing discontinuous fibrillated fibers according to claim 1, wherein a mixed fluid of the formed fibrillated fibers and a solvent and a coagulant fluid is discharged into the coagulant.