JPH0641811A - Production of polyolefinic three-dimensional fiber - Google Patents

Abstract

PURPOSE:To produce polyolefinic reticular fiber, excellent in strength and opening properties and suitable for producing a flash spun nonwoven fabric sheet by using a noncombustible halogenated hydrocarbon having remarkably low ability to destroy the ozonosphere. CONSTITUTION:The objective method for producing polyolefinic three- dimensional fiber is characterized by using a mixed solvent composed of a good solvent selected from the group consisting of trichloroethylene, tetrachloroethylene, fluorotrichloroethylene and 1,1,2-trichloro-3,3,3- trifluoroethylene and a cosolvent, selecting the cosolvent from the group consisting of carbon dioxide, sulfur hexafluoride, chlorodifluoromethane and 1,1,1,2-tetrafluoroethane for a polyolefinic solution and regulating the weight ratio of the polyolefin to the solvent in the polyolefinic solution to 5-25wt.% in a method for producing the fibrillated polyolefinic three-dimensional fiber by passing the polyolefinic solution prepared at a high temperature under a high pressure through a vacuum orifice, a vacuum chamber and a spinneret and releasing the resultant solution to a zone at ordinary temperature under atmospheric pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyolefin three-dimensional fiber using a solvent which is nonflammable and can be used very safely. Further, the present invention relates to a method for producing a three-dimensional fiber of polyolefin excellent in strength and fiber opening property, which is used for a nonwoven fabric sheet by using a solvent having a low ozone depleting ability.

[0002]

2. Description of the Related Art A method for producing a three-dimensional fiber of polyolefin is
It is known as a flash spinning method. In this flash spinning method, polyolefin is added to an organic solvent which can be said to be a liquefied gas, a polyolefin solution is prepared under high temperature and high pressure, and then the pressure of the solution is once lowered through a decompression orifice to cause phase separation, resulting in opacity. This is a method in which the solution is further jetted through a spinneret into an atmosphere at room temperature and normal pressure to form a three-dimensional fiber, which is a well-known spinning method.

For example, this spinning method is described in US Pat.
81519 (1963), U.S. Pat. No. 3,227.
794 (1966), U.S. Pat. No. 322778.
4 (1966), U.S. Pat. No. 3,467,744 (1969), U.S. Pat. No. 3,564,088 (1971), U.S. Pat. No. 3,756,411 (1973), European Patent Application Publication No. 285670A1 (1988), European Patent Application Publication No. 321567.
A1 specification (1989), European Patent Application Publication No. 357.
364A2 Specification (1990), Japanese Examined Patent Publication No. 40-281
No. 25, Japanese Patent Publication No. 42-19520, Japanese Patent Laid-Open No. Sho 6
It is described in JP-A-2-33816, JP-A-63-50512, and the like.

Fibers obtained by this flash spinning include short fibrous substances and continuous three-dimensional fibrous substances,
The former is used as synthetic pulp, and the latter is intended for three-dimensional fibers to be a non-woven sheet. This non-woven sheet is generally called synthetic paper,
The main feature of the product is that it is highly water resistant, strong, light and non-fluffy.

This is highly evaluated in the world, and this non-woven fabric sheet includes an air mail envelope, a floppy disk sleeve, an oxygen absorber bag, a desiccant bag, a medical sterilization bag, a building heat insulation dew condensation prevention cloth, a reactor power generation work clothes. It is applied to asbestos work clothes and safety protection work clothes. In order to manufacture a product having these characteristics, a three-dimensional fiber having high strength and well opened is essential. This is because a dense, breathable and uniform sheet cannot be obtained without such fibers.

As a product of such a non-woven sheet,
The trademark Tyvek manufactured by DuPont, USA and the trademark Luxer manufactured by the present applicant are already commercially available. By the way, the solvent of the polymer used in the flash spinning method is required to have the following properties, which is already known in US Pat. No. 30,815,19 (1963) and the like. That is, the boiling point of the solvent is at least 25 ° C. lower than the melting point of the polymer used, the solvent is inert to the polymer under spinning conditions, and the temperature and pressure are suitable for preparing the polymer solution. Is a good solvent, a polymer that dissolves only 1% or less of a polymer at a boiling point of the solvent or less, a solvent that can form a phase consisting of almost a polymer by phase separation immediately during spinning, and the separation thereof. It is a solvent that hardly remains in the polymer phase.

Specific examples of the solvent include aromatic hydrocarbons such as benzene and toluene, aliphatic hydrocarbons such as butane, pentane, hexane, heptane and octane, and their isomers, homologues and fats such as cyclohexane. Aromatic hydrocarbons, unsaturated hydrocarbons, halogenated hydrocarbons such as methylene chloride, carbon tetrachloride, chloroform, ethyl chloride and methyl chloride, alcohols such as ethanol, methanol and hexafluoroisopropanol, esters, ethers, ketones, Chlorinated fluorinated aliphatic hydrocarbons such as nitrile, amide, trichlorofluoromethane, 1,1,2-trichloro-1,2,2-trifluoroethane, sulfur dioxide, carbon disulfide, nitromethane, water and the above various Liquid mixtures and the like are known.

The optimum solvent is appropriately selected from these solvents in consideration of various conditions of the spinning method and the kind of the polymer. In particular, as a solvent for the flash spinning method of polyolefin, it has excellent polymer solubility and spinnability, and is also nonflammable and nontoxic trichlorofluoromethane, 1,1,2-trichloro-1,2,2. -Trifluoroethane is preferred. In particular, trichlorofluoromethane is the most excellent solvent.

In flash spinning, the solvent must be at least low toxic and flame-retardant in order to eject the polymer solution under high temperature and high pressure into the atmosphere for gasification. In addition, it is required that the solvent has a low boiling point, is not thermally decomposed even at a high temperature, and is lipophilic enough to dissolve the polyolefin. The best solvent satisfying such conditions is the above-mentioned trichlorofluoromethane, and at present, no solvent surpassing this is found.

A large number of hydrocarbons or halogenated hydrocarbons have been disclosed as solvents for flash spinning. In flash spinning, the solvent is gasified and separated from the polymer, and the gasified solvent is recovered and liquefied by an operation such as cooling and compression. Therefore, flash spinning is performed in a vast enclosed space. This is because otherwise the gasified solvent cannot be recovered. The size of the closed space is, for example, 2000 m ³ .

Further, usually, a corona discharge device or a high-voltage static eliminator is built in this closed space and can serve as an ignition source for combustible gas. Therefore, to fill such a huge space with combustible gas is a fire,
Since the possibility of explosion and the like is extremely increased, it is extremely dangerous, and flammable gas cannot be practically used as a solvent.

Recently, it has been discovered that all halogenated hydrocarbons in which all hydrogens are replaced by chlorine and fluorine have extremely high ozone depletion ability as specific CFCs (also referred to as chlorofluorocarbons or CFCs). From the standpoint of protection, production was banned by the year 2000. Naturally, the production of specific fluorocarbons such as trichlorofluoromethane and 1,1,2-trichloro-1,2,2-trifluoroethane is also prohibited and cannot be obtained. Therefore, trichlorofluoromethane cannot be used as a solvent for the flash spinning method of polyolefin.

Against this background, there has already been proposed a flash spinning method using a new solvent without using trichlorofluoromethane which is a specific flon. That is, US Pat. No. 5,032,326 (1991),
European Patent Application Publication No. 0357381A2 (19
89), JP-A-2-139408, methylene chloride and alternative fluorocarbons such as chlorofluoromethane, 1,
A flash spinning method using a mixed solvent of 1,1,2-tetrafluoroethane, 1,1-difluoroethane, 1,1,1,2-tetrafluoro-2-chloroethane, 1-chloro-1,1-difluoroethane, etc. It is disclosed.

US Pat. No. 5,081,177 (1992) and US Pat. No. 5,023,025 (1)
991), EP-A-0361684A1 (1990), and JP-A-2-160909, 1,1-dichloro-2,2,2-trifluoroethane, 1,2-dichloro-1, 2,2-trifluoroethane, 1,1-dichloro-2,2-difluoroethane, 1,
A spinning method using 2-dichloro-1,1-difluoroethane, 1,1-dichloro-1-fluoroethane, or the like is further described in European Patent Application Publication No. 0407953A2 (1991) with respect to polypropylene. A method of spinning using 1-dichloro-2,2,2-trifluoroethane, 1,2-dichloro-1,2,2-trifluoroethane, and further, European Patent Application Publication No. 357364A2.
The specification (1990) and Japanese Patent Laid-Open No. 3-76809 propose a spinning method using methylene chloride and carbon dioxide.

[0015] Also, European Patent Application Publication No. 0414498.
A2 specification (1991) and JP-A-3-152209 propose a method using a mixed solvent system of water-containing organic solvents. Further, European Patent No. 431801 (1991) proposes a spinning method using carbon dioxide and water. However, all of these already proposed flash spinning methods have problems when spinning with polyolefins.

For example, a mixed solvent of methylene chloride and CFC substitute proposed by US Pat. No. 5,032,326 (1991) has a problem in view of characteristics required for the solvent during spinning. , The heat of vaporization of methylene chloride is 78.
7 cal / g, trichlorofluoromethane 43.5
It is much larger than cal / g. This means that when methylene chloride is used as the solvent, the flash-spun fibers are easily wetted by the residual solvent.
Moisture fibers have a commercial value because they tend to stick around and wrap around the rollers used to harden the fibers into a sheet structure, as pointed out in JP-A-3-76809. Non-woven sheet cannot be used and cannot be produced commercially.

Therefore, when methylene chloride is used as a solvent, a gas having a low boiling point is allowed to coexist to promote the evaporation of methylene chloride remaining in the fiber after spinning, and at the same time, the polymer concentration of the spinning solution is adjusted in advance. It is necessary to raise it. Increasing the polymer concentration is effective in increasing the coagulation heat generation amount of the polymer when flushing the polymer solution and utilizing the heat to accelerate the drying of the spun fiber.

In this case, if either the use of the low boiling point gas or the increase of the polymer concentration is lacking, a wet fiber will result. However, when the polymer concentration of the spinning solution is increased, the spread state of the obtained spun fiber is deteriorated, and the quality of the sheet-shaped product tends to be deteriorated. Therefore, it is understood that methylene chloride cannot be used from the viewpoint of such spinnability.

There is also a problem with the proposal using alternative CFCs such as US Pat. No. 5,081,177 (1992). It is known that 1,1-dichloro-2,2,2-trifluoroethane and its isomers have an ozone depleting ability at a low level, and may be regulated as an ozone depleting substance in the near future. high. Therefore, such a solvent cannot be a substitute solvent for trichlorofluoromethane that can be used forever.

Further, since these CFC substitutes are poor solvents for high-density polyethylene, which is a typical example of polyolefin, there is another problem that high-density polyethylene cannot be dissolved when used alone. Therefore, in order to improve the solubility, a technique of using hydrocarbon, methylene chloride or the like as a cosolvent has been disclosed at the same time. However,
Even if hydrocarbons and methylene chloride coexist, since the ratio of CFC substitutes in the solvent is still high at 50% or more, the influence of these CFC substitutes on the poor solvent of high-density polyethylene remains strong. However, there is a problem that it is difficult to dissolve high-density polyethylene and the dissolution rate is slow. Similarly, 1,1-dichloro-2,2-difluoroethane and its isomers also have problems in ozone layer depleting ability and solubility of high-density polyethylene. on the other hand,
1,1-dichloro-1-fluoroethane and its isomers are
Even when used alone, it dissolves high density polyethylene and gives good quality yarn.

However, these solvents are very likely to be thermally decomposable, and even if they are rapidly dissolved by an extruder, a large amount of hydrogen chloride or hydrogen fluoride is released and thermally decomposed to easily generate a halogenated oligomer. . These decomposed products cause serious problems such as coloring the product and corroding the spinning device. Furthermore, regarding 1,1-dichloro-1-fluoroethane, this solvent has a higher ozone depletion capacity of about 1/10 that of trichlorofluoromethane,
There is also a problem of having a high ozone depleting ability. Therefore, 1,1-dichloro-1-fluoroethane and its isomers cannot be used as a flash spinning solvent because they are easily decomposed by heat and have a high ozone depleting ability.

The technique proposed in EP-A-357364A2 (1990) cannot be used for the reasons already mentioned because it uses methylene chloride as a solvent. In addition, European Patent No. 431801 (199
The method of flash spinning using carbon dioxide and water as a solvent proposed in 1) can be applied to a specific polyolefin having vinyl alcohol, which is rich in hydrophilicity, as a copolymerization component. However, this solvent is common polyethylene,
Due to their poor ability to dissolve polypropylene, it is almost impossible to obtain fibers with desirable physical properties. Moreover, in this method, it is necessary to use a surfactant substantially in combination, which not only complicates the process, but also causes a problem that the surfactant remains in the obtained fiber and practical properties are deteriorated. There is.

Furthermore, European Patent Application Publication No. 04144
Proposals using mixed systems of water-containing organic solvents such as 98A2 (1991) cannot be used because the solvent used has high flammability. From the above, it is clear that the trichlorofluoromethane alternative solvents for flash spinning that have been proposed so far all have unsolved problems, and they are still sufficiently satisfactory to substitute trichlorofluoromethane. No possible solvent has been proposed.

[0024]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a three-dimensional fiber using a sufficiently satisfactory solvent which can substitute for trichlorofluoromethane. That is, it is an object of the present invention to provide a method for producing a three-dimensional fiber using a solvent which is excellent as a solvent for flash spinning of polyolefin, which is hard to burn and has a low ozone depletion ability. Furthermore, an object of the present invention is to provide a method for flash spinning a polyolefin by using this solvent to obtain a three-dimensional fiber having high strength and excellent openability.

[0025]

In order to achieve the above-mentioned object, the present inventors have conducted a great deal of research on solvent screening to find a fiber comparable to or superior to a polyolefin three-dimensional fiber by a conventional flash spinning method. Through trial and error, it was possible to reach the present invention as a result of trial and error on how to obtain a fiber having the following performance.

That is, according to the present invention, a polyolefin solution prepared at high temperature and high pressure is passed through a decompression orifice, a decompression chamber and a spinneret and discharged into a room temperature and pressure range to produce a three-dimensional fiber of fibrillated polyolefin. In the method described above, trichloroethylene, tetrachloroethylene, fluorotrichloroethylene, 1,1,2-trichloro-3,
Using a mixed solvent consisting of a good solvent selected from the group consisting of 3,3-trifluoroethylene and a cosolvent, the cosolvent is carbon dioxide, sulfur hexafluoride, chlorodifluoromethane, 1,
A process for producing a polyolefin three-dimensional fiber, which is selected from the group consisting of 1,1,2-tetrafluoroethane, wherein the weight ratio of the solvent to the polyolefin is 5 to 25%,
Is.

According to this method, the present inventors have developed a three-dimensional polyolefin having a markedly high strength and a good openability, which is different from the conventionally known improvement method, even though the solvent has a small ozone depleting ability. The fiber could be obtained. As described above, the solvent used for flash spinning is premised on being an organic solvent that becomes a gas at normal temperature and pressure. That is, the polyolefin is melted under high temperature and high pressure, and then the pressure is once lowered to change the phase from a transparent liquid to an opaque liquid, and then the opaque polymer solution is blown out through a spinneret into an atmosphere at normal temperature and normal pressure. At this time, the organic solvent is gasified to form a supersonic gas jet. The polymer is solidified and stretched by this gas jet, and becomes a three-dimensional fiber having high strength.

Therefore, the properties to be possessed as the flash spinning solvent have been disclosed as described above, but the details are as follows. At normal temperature and pressure, the polymer does not dissolve at all, but at temperatures above the melting point of the polymer and at high pressures far above atmospheric pressure, the polymer is dissolved. Phase change from a transparent liquid to an opaque liquid at a temperature above the melting point of the polymer and at which thermal degradation does not occur, especially in the case of flash spinning, LCS referred to as polymer solution theory
T (Lo wer Cr itical So lution Te mperature, the lower critical solution temperature) is preferably in the polymer solution with type phase diagram, it is preferable that flash spinning solvent also has an LCST type phase diagram. Moreover, it is preferable to have an LCST type phase diagram, and moreover, the phase change should occur instantaneously. This property is important because flash spinning causes a phase change from transparent to opaque under pressure.

At the moment of leaving the spinneret, it must be gasified. This means that it must have a boiling point near normal temperature and normal pressure. That is, it must be a low boiling organic solvent. The change before and after the spinneret is almost isentropic change. Therefore, the spinneret outlet spontaneously becomes a liquid / gas mixture. As it is, it becomes a wet three-dimensional fiber and cannot be used. However, since the polymer has heat, this amount of heat gasifies the liquid to form a dry three-dimensional fiber. This means that the heat of vaporization of the organic solvent must be appropriate.

The organic solvent must have good thermal stability as it is exposed to temperatures above the melting point of the polymer. It must be non-combustible or flame-retardant because there is electrical equipment that fills a large-capacity enclosed space and is an ignition source in the enclosed space. The gas that fills the enclosed space is often touched by humans, so it must be non-toxic.

Since the flash spinning apparatus as a whole becomes a high-pressure apparatus, it must be a solvent having low corrosiveness. It must have a low ozone depletion capacity. Particularly important are low boiling point, LCST type polymer solution, thermal stability, low flammability, and low ozone depletion ability.

The present inventors have found that a flash spinning solvent satisfying the following five conditions: low boiling point, LCST type polymer solution, thermal stability, low flammability and low ozone depleting ability,
Very many experiments were conducted. As a result, a mixed solvent consisting of a good solvent and a cosolvent selected from the group consisting of trichloroethylene, tetrachloroethylene, fluorotrichloroethylene, 1,1,2-trichloro-3,3,3-trifluoroethylene completely satisfies the above 5 conditions. , Or found to meet almost completely.

Hereinafter, the reason why the solvent and the solution used in the present invention satisfy the above-mentioned 5 conditions particularly required for flash spinning, the characteristics, the preferable composition range and the like will be described. In addition,
In the following description, chlorodifluoromethane refers to HCF
C-22,1,1,1,2-tetrafluoroethane is H
It is abbreviated as FC-134a. Boiling point The boiling point is preferably 60 ° C. or lower, and more preferably 50 ° C. or lower, as long as it is gasified at room temperature and atmospheric pressure. This boiling point is a function of the solvent composition in the mixed solvent and can be freely adjusted. The boiling point of trichlorethylene is 87.
1 ℃, the boiling point of tetrachloroethylene is 121.1 ℃,
Fluorotrichlorethylene is 71.0 ℃, 1,1,2
-The boiling point of trichloro-3,3,3-trifluoroethylene is 88.1 ° C. However, since the boiling points of the other three alternative CFCs are all -10 ° C or lower, the mixed solvent of the present invention can be adjusted to a desired boiling point of 60 ° C or lower by changing the mixing ratio of these solvents.

Cloud Point Curve The solvent used in the present invention becomes an LCST type polymer solution when polyolefin is dissolved therein. As described above, the basic principle of flash spinning is that the polymer solution at high temperature and high pressure is decompressed to be phase-separated into an opaque liquid composed of at least two phases of the polymer and the solvent, and then spun. Therefore, the cloud point temperature and pressure that can be determined by changing from a transparent liquid to an opaque liquid are extremely important.

This cloud point is also the point at which phase separation occurs. The cloud point is indicated by the temperature and pressure at the point where the liquid changes from transparent to opaque. In polymer chemistry, a diagram in which this cloud point is plotted on temperature and pressure coordinates is called a cloud point curve. The suitability of the solvent for flash spinning can be judged from the position of the cloud point curve on the temperature / pressure coordinate plane. To show flash spinnability specifically, the cloud point pressure is about 100 to 400 k at around 200 ° C. when high density polyethylene is used.
It should be in the range of g / cm ³ .

Trichloroethylene, tetrachloroethylene, fluorotrichloroethylene, and 1,1,2-trichloro-3,3,3-trifluoroethylene are all excellent polyolefin good solvents under high temperature and high pressure, and are suitable for ordinary flash spinning. Under the conditions, only a perfectly homogeneous solution is produced and no phase separation occurs. on the other hand,
Carbon dioxide, sulfur hexafluoride, HCFC-22, HFC-
Under normal flash spinning conditions, 134a is
The polymer cannot be dissolved. That is, these liquefied gases are completely poor solvents.

Therefore, trichloroethylene, tetrachloroethylene, fluorotrichloroethylene, 1,1,2-
By using a good solvent selected from the group consisting of trichloro-3,3,3-trifluoroethylene and a cosolvent that is four liquefied gases as a mixed solvent, a cloud point curve is provided at a position suitable for flash spinning. I was able to come. Considering the applied pressure, the preferable mixing ratio of the cosolvent is generally 5 to 40% by weight. It is particularly preferably 5 to 35% by weight, and even more preferably 10 to 35% by weight.

FIG. 1 shows an example of a cloud point curve. The cloud point curve A in FIG. 1 shows the cloud point when trichlorethylene / carbon dioxide (80/20 wt%) is used, and the cloud point curve B shows the cloud point when trichlorethylene / HFC-134a (75/25 wt%) is used. . The upper region of each cloud point curve is a one-phase region, and the lower region is a two-phase region. The polymer has a density of 0.97 g / cm ³ and a weight average molecular weight of 1020.
It is a high density polyethylene of 00 (dispersion degree 6.14) and has a polymer concentration of 18% by volume.

Thermal Stability The solvent used in the present invention has thermal stability enough to withstand use under the conditions of flash spinning, and does not substantially cause any decomposition reaction. Flammability All the solvents used in the present invention are substantially nonflammable,
Can be used without problems.

Ozone-depleting ability It is OH that determines the life of halogen compounds in the atmosphere.
It is an active chemical species called a radical. It is produced by the reaction of oxygen and organic matter under the ultraviolet light from the sun.
Since the good solvents used in the present invention each have a double bond, it is difficult for them to react with OH radicals and remain in the atmosphere, and their atmospheric life is extremely short. Therefore, the good solvent used in the present invention has no substantial ozone depletion ability.

On the other hand, carbon dioxide, sulfur hexafluoride, HFC
Since all of -134a are non-Freon, these three cosolvents have no ozone depleting ability. HCF
C-22 (Ozone depletion capacity ODP is 0.05)
Ozone depleting ability OD because it is a CFC containing hydrogen atoms
P is much smaller than the specific CFC. However,
HCFC-22 may be subject to regulation in the near future.

From the above-mentioned limitations, consideration, and experimental results, the preferable mixing ratio of the CFC substitute is generally 5 to 40% by weight. Particularly preferably, 5 to 3
It is 5% by weight, and more preferably 10 to 35% by weight. Since the method of the present invention is substantially composed of a solvent having no ozone depleting ability except for HCFC-22, it can be used forever without any problem. To date, flash spinning solvents using alternative CFCs with low ozone depletion potential have been disclosed, but these solvents all have ozone depletion potential, albeit at low levels. . Today, as regulations on CFCs are increasing day by day, they have no ozone depleting ability,
Moreover, it is clear how important and excellent the present invention is to provide a nonflammable solvent.

The three-dimensional fiber spun using the flash spinning solvent of the present invention determined as described above has excellent openability and high strength without getting wet, and can be a good nonwoven sheet. It was a thing. The weight ratio of the flash spinning solvent and the polyolefin used in the present invention is 5 to 5.
It is 25% by weight. In this range, excellent openability,
In addition, polyolefin three-dimensional fibers having high strength can be easily manufactured. If it is 5% by weight or less, it becomes a pulp-like or low-strength fiber, and if it is 25% by weight or more, the fiber openability becomes low, which is not preferable in any case. More preferably, it is 10 to 20% by weight.

As the polyolefin, polyethylene,
Examples include polypropylene and polymethylpentene-1. The polyethylene is most preferably high-density polyethylene, and the density is 0.94 g / cm ³ or more. Further, the copolymerization component is preferably 15% by weight or less and maintains the above-mentioned density. The polypropylene preferably contains about 85% by weight or more of isotactic polypropylene, and may contain about 15% by weight or less of other polypropylene or a copolymerization component such as ethylene or butene. Further, a polymer additive, a light stabilizer, a lubricant, a nucleating agent, a cross-linking agent, a plasticizer, a filler and the like which are generally known may be contained in the polymer.

The apparatus used in the present invention may be equipped with a dissolution adjusting device, a decompression orifice, a decompression chamber, and a spinning device including a spinneret. Before that, there are a device for opening and dispersing the three-dimensional fibers, a moving conveyor device for forming the opened and dispersed three-dimensional fibers into a sheet, and a winder for winding the resulting sheet. The sheet forming unit is housed in a closed box, and the solvent gas in the box is collected. The solution adjusting device may be an autoclave device or an extruder. Alternatively, a conventionally known device can be used.

[0046]

The contents of the present invention will be described with reference to the following examples. In addition, the openness evaluation scale is that the number of free fibrils is 300 or more, the number is 100 to 300, and the number x is 100 or less. The measurement method of the number of free fibrils was performed as follows. The three-dimensional reticulated fiber is
It has a structure in which a large number of delicate single fibers (single yarn) are connected in a net. The larger the number of individual fibers in the same denier is, the better the three-dimensional reticulated fibers are. The number of free fibrils is about 25m from the tip of the spinneret.
The measurement is performed using fibers in an opened state obtained by colliding a gas jet spun on a copper plate tilted at an angle of about 25 ° at a position of m with the fibers contained. Gently sandwich the sampled open fibers between the glass plates and move the optical microscope with an objective lens of 1.6 times and an eyepiece lens of 10 times in the fiber width direction, and each single fiber in the field of view. Is counted and converted into 100 denier to obtain the number of free fibrils.

[0047]

Example 1 81.7 g of high-density polyethylene having a melt index of 0.78 and 481 g of a mixed solvent of trichlorethylene / carbon dioxide (75/25% by weight) were charged into an autoclave to prepare a propeller (polymer concentration: 14.5% by weight). The autoclave was heated while rotating the mold stirrer to dissolve the high density polyethylene. The solution was further heated and the solution pressure was increased to completely dissolve the polymer.

After the dissolution, the solution pressure is 300 kg / cm ²
The solution was discharged from the discharge nozzle in the lower part of the autoclave so as not to exceed the pressure of 200 to 300 kg / cm ² . When the temperature of the solution reached 200 ° C, the solution was discharged, and the pressure applied during spinning was 230 kg / cm ²
After making the pressure 10 kg / cm ² lower than that, the solution temperature was adjusted to a predetermined 200 ° C., the nitrogen gas introduction valve at the upper part of the autoclave was opened, and the pressure of 230 kg / cm ² was applied.
I quickly opened the drain valve at the bottom of the autoclave.

Then, the solution was put under a reduced pressure orifice (having a diameter of 0.
65 mm, length 5 mm) and a decompression chamber (diameter 8
mm, length 40 mm), spinneret (introduction angle from the decompression chamber to the nozzle is 60 °, nozzle diameter is 0.5 mm,
Length is 0.5mm, 3.3m outside the center of the nozzle
It has a circular groove with mφ and a depth of 3 mm. ),
Released into the atmosphere. Approximately 2 fibers are opened from the spinneret
It was made by applying it to a vinyl chloride plate inclined at about 45 ° at a position apart from 0 to 40 mm. The opened fiber was received by a 10-mesh wire net and collected.

The obtained fiber has a fineness of 9 in an unopened state.
4d, tensile strength 5.4g / d, tensile elongation 3
2%, specific surface area of 35 m ² / g, fineness of 96 when opened
d, tensile strength is 5.5 g / d, tensile elongation is 32
%, The fiber width was 3.5 to 6 cm, and it was a good three-dimensional reticulated fiber.

[0051]

Comparative Example 1 Fibers were produced by repeating the same conditions as in Example 1 except that trichlorofluoromethane was used as the solvent and the polymer concentration was 12.5% by weight. The obtained fiber has a fineness of 99d and a tensile strength of 5.4 in an unopened state.
g / d, tensile elongation 27%, specific surface area 21.2m
It was ² / g.

[0052]

Example 2 A three-dimensional reticulated fiber was produced with the polymer, the polymer concentration, the spinning apparatus and the like being fixed under the same conditions as in Example 1 except that only the solvent composition was changed. When the weight ratio of trichlorethylene / carbon dioxide is 90/10, the strength is 4.3 g / d, and when it is 80/20, the strength is 5.7 g /
At d and 70/30, a three-dimensional reticulated fiber having a strength of 5.3 g / d was obtained. All of these three-dimensional reticulated fibers showed good openability.

[0053]

Example 3 A three-dimensional reticulated fiber was produced with the polymer, solvent composition, spinning device and the like fixed under the same conditions as in Example 1 except that only the polymer concentration was changed. When the polymer concentration is 7.2% by weight, the strength is 3.2 g / d, 20.5.
When the weight percentage was 3, a three-dimensional reticulated fiber having a strength of 4.8 g / d was obtained. All of these three-dimensional reticulated fibers showed good openability.

[0054]

Examples 4 to 6 The same conditions as in Example 1 except that the cosolvent of Example 1, carbon dioxide, was changed to another cosolvent,
A spinning experiment was conducted using a spinning device. Table 1 shows the spinning results. The obtained fiber was a good three-dimensional reticulated fiber having excellent openability and high strength.

[0055]

[Table 1]

[0056]

[Examples 7 to 9] (A) Tetrachlorethylene, (B) Fluorotrichloroethylene, (C) 1,1,2-Trichloro-
A spinning experiment was conducted under the same conditions as in Example 1 except that the good solvent for 3,3,3-trifluoroethylene was changed to carbon dioxide as a cosolvent, the spinning apparatus and the like. Table 2 shows the spinning results.

[0057]

[Table 2]

[0058]

The manufacturing method of the present invention is equivalent to the case of using trichlorofluoromethane without destroying the ozone layer,
Alternatively, it is possible to obtain a socially useful three-dimensional fiber having higher strength and openability. The production method of the present invention is, as compared with the conventionally known flash spinning method using a solvent that can substitute trichlorofluoromethane, is remarkably excellent in openability, and also has three-dimensional fibers of a high-strength polyolefin.
It can always maintain stable productivity and can be easily manufactured. This industrial significance is of great value.

[Brief description of drawings]

FIG. 1 shows an example of a cloud point curve of a polymer solution of the present invention.

[Explanation of symbols]

A trichlorethylene / carbon dioxide (80/20 wt%) B trichlorethylene / HFC-134a (75 /
25% by weight)

Claims (1)

[Claims] 1. A method for producing a three-dimensional fiber of fibrillated polyolefin by allowing a polyolefin solution prepared at high temperature and high pressure to pass through a decompression orifice, a decompression chamber and a spinneret and releasing into a room temperature and pressure region. Using a mixed solvent consisting of a good solvent selected from the group consisting of trichloroethylene, tetrachloroethylene, fluorotrichloroethylene, 1,1,2-trichloro-3,3,3-trifluoroethylene and a cosolvent, the cosolvent is carbon dioxide, hexafluoroethylene. Polyolefin three-dimensional fiber selected from the group consisting of sulfur fluoride, chlorodifluoromethane and 1,1,1,2-tetrafluoroethane, wherein the weight ratio of the solvent to the polyolefin is 5 to 25%. Manufacturing method.