JPH101819A - Continuous production of net-like fiber by flash spinning - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for continuously producing a net-like fiber by a flash spinning, having a simple and safe process for preparing a high molecular polymer solution. SOLUTION: A net-like fiber consisting of a thermoplastic polymer is produced by a flash spinning method. In the method, a polymer is continuously charged to a melting zone while melting the polymer by a heated screw-type extruder, a solvent is continuously supplied to the melting zone while plugging the charging opening of the melting zone by the molten polymer continuously charged, both of the molten polymer and the solvent are mixed and dissolved by using a mechanical mixing zone following the screw in the screw-type extruder and a static mixing zone having statically mixing elements under pressure to form a polymer solution having 5-20wt.% polymer content, and the obtained polymer solution is continuously extruded from a nozzle installed in the discharging opening of the dissolving zone to a low pressure zone.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a highly spun fibrous reticulated filament-spun fiber comprising a thermoplastic polymer, and more particularly to a method for continuously and stably producing a flash-spun fiber. It relates to a manufacturing method.

[0002]

BACKGROUND OF THE INVENTION A method for obtaining continuous three-dimensional reticulated filaments is known as flash spinning technology. In this spinning method, a highly fibrillated three-dimensional reticulated filament is obtained by preparing a homogeneous solution of a polymer and a solvent at a high temperature and a high pressure and discharging the solution to a low pressure region.

[0003] In this spinning method, a solvent capable of dissolving a polymer at a high temperature and a high pressure and having a flash property and a relatively low boiling point is selected. In addition, these solvents do not have the ability to dissolve the polymer at normal temperature and normal pressure,
Dissolve the polymer only at high temperature and pressure. Therefore, the principle of flash spinning is to develop a network structure fiber by a change in the structure of the solution accompanying the transition from a homogeneous solution of high temperature and high pressure to a low pressure region, flashing of the solvent and solidification of the polymer. Therefore, in order to continuously and stably produce reticulated fibers, spinning from a homogeneous solution comprising a polymer and a solvent is essential.

As a process for obtaining a flash spun fiber, as disclosed in Japanese Patent Publication No. 42-19520, a method in which a polymer is heated, pressurized, melted and spun in a pressure vessel having a stirring device is a batch method. It is known. And as a method of continuously obtaining fibers, USP3
No. 227794 discloses various spinning processes. That is, after introducing a predetermined amount of the molten polymer and the solvent into the screw mixer, a method of spinning by dissolving in a dissolving tank having a stirring mechanism, making the polymer powder and the solvent into a slurry state, leading to a dissolving tank with a baffle, and dissolving. How to spin,
Alternatively, a method of dissolving a slurry with a slurry pump and piping and spinning the slurry is known.

[0005]

However, when a uniform solution of a polymer is prepared using these known techniques and flash spinning is performed to continuously produce a reticulated fiber, there are various problems. Has been found to be.
It is pointed out that when a known technique is used, it takes a long time to dissolve a polymer in a solvent. For this reason, in an autoclave-type stirring tank, strong shearing force required for dissolution does not work, and the dissolution time is increased by simply increasing the residence time, and as a result, a uniform polymer solution is obtained.
Therefore, it is premised that a large-capacity container is used, the residence time is inevitably increased, and the container has a large capacity and a sliding portion. Therefore, it is extremely difficult for the pressure in the container to exceed 200 kg / cm ² · G. .

When a swollen polymer is dissolved by laminar flow mixing using a pipeline, the only shearing force required for the dissolution is a flow velocity difference, which requires an extremely long pipeline, which increases the residence time. Leads to. Further, in the case of turbulent mixing, the polymer solution has a high viscosity of about 30 to 100 poise, so that an extremely high flow rate is required and a huge pump is required, which is practically difficult.

In any case, the solvent used for flash spinning must not dissolve the polymer at normal temperature and pressure, but must dissolve the polymer only at high pressure and high temperature. In flash spinning, high temperature and high pressure are essential, and therefore, in the prior art, the residence time necessarily increases, and conversely, high pressure is limited. If the polymer stays in the system at a high temperature for a long time, this immediately leads to deterioration of the polymer, and it is impossible to stably obtain a good reticulated fiber.

[0008] This difficulty is increasingly compounded as the polymer becomes higher molecular weight, and becomes practically insoluble above a certain molecular weight. This is because there is a strong demand for the use of a high molecular weight polymer in the production of reticulated fibers from flash spinning in consideration of the strength, toughness and various resistances of the product. Furthermore, since spinning is performed as a solution in flash spinning, it is possible to use a high molecular weight polymer which is difficult to spin in ordinary melt spinning. Rather, the usefulness of flash spinning can be fully demonstrated only when a high molecular weight polymer that is difficult to melt spin can be used.

[0009] However, in the conventionally known technique, the dissolution of the polymer becomes more difficult as the molecular weight becomes higher, and it is impossible to continuously and stably obtain a reticulated fiber having desirable properties utilizing the usefulness of flash spinning. It leads to the situation. The cause of such a situation is considered to be the affinity between the polymer and the solvent. That is, flash spinning is USP32
As shown in Japanese Patent No. 27794, this technique utilizes a structural change of a solution, a flushing force of a solvent, and solidification of a polymer by discharging a uniform solution of a high temperature and a high pressure by a decompression orifice and then discharging the solution from a spinning nozzle. The affinity between the solvent and the solvent has a very important meaning.
For this reason, the solvent used for flash spinning is selected so as not to dissolve the polymer at normal temperature and normal pressure and to form a uniform solution with the polymer at high temperature and high pressure. Therefore, it is clear that the polymer / solvent used for flash spinning is a system that does not dissolve unless the temperature and pressure are high, and that the dissolving power decreases as the degree of polymerization of the polymer increases.

In order to continuously obtain the desired properties and morphology of the reticulated fiber, it is essential to supply a homogeneous solution of a polymer / solvent together with appropriate spinning conditions. Particularly when a high molecular weight polymer is used, a technique different from the conventional technique is expected. Another major problem of the prior art is the stirring shaft of the mixing / dissolving tank. That is, according to the prior art, there is no other choice but to obtain a uniform polymer solution by a stirring tank driven by an external drive source or to obtain a target polymer solution by using a long pipeline and taking a long time. With regard to the latter, since there is no forced mixing, a substantially uniform solution of a polymer having a molecular weight that is practically high cannot be obtained.

Therefore, the former method using a stirring shaft is more practical, but since this method also includes a sliding portion in a device to be used, the pressure cannot be increased to a certain level or more.
There is also a problem that a special and expensive seal for the sliding portion is required. The polymer / solvent system that performs flash spinning forms a solution at high temperature and high pressure, and in order to effectively use the affinity between the polymer and the solvent, the higher the pressure, the higher the dissolution even at the same temperature. A polymer solution is obtained.

The same is true for the molecular weight of a polymer. The higher the molecular weight, the higher the pressure required for its dissolution. However, in the conventional method, it was not possible to obtain a high pressure enough to dissolve the high molecular weight polymer due to the problem of sealing of the sliding portion, and therefore, it was practically difficult to spin the high molecular weight polymer. Thus, from the viewpoint of preventing polymer deterioration,
Also, a spinning method suitable for a high-pressure process is strongly demanded from the viewpoint of using a high molecular weight polymer.

[0013]

Means for Solving the Problems In view of such problems, the present inventors have made intensive studies and arrived at the present invention. That is, the present invention relates to a method for producing a network fiber made of a thermoplastic polymer by a flash spinning method, in which a heated screw extruder is used to continuously supply a polymer to a polymer dissolving zone while melting it. The solvent is continuously added to the polymer dissolving zone while closing the inlet of the melted polymer with the continuously supplied molten polymer, and a static mixing element comprising a mechanical mixing area continuous with the screw in the screw extruder and a static mixing element. And a polymer solution having a polymer concentration of 5 to 20% by weight by mixing and dissolving the two under pressure using a static mixing region, and then polymerizing the polymer solution into a low pressure region through a nozzle provided at the outlet of the dissolution region. This is a continuous production method of a reticulated fiber by a flash spinning method characterized by continuously discharging.

[0014] Preferably, there is provided a continuous production method of a reticulated fiber in which all the solvent is added to the polymer dissolving zone immediately after being blocked with the molten polymer. More preferably, it is a continuous production method of a reticulated fiber in which the addition of the solvent to the polymer dissolving region is multi-stage, and each time the solvent is added, the solvent is mixed and dissolved with the polymer, so that the concentration of the polymer is gradually reduced. .

[0015] Furthermore, more preferably, the addition of the solvent to the polymer dissolving zone is multi-step, and at least the first of the solvent is added.
Mixing and dissolution are performed in a mechanical mixing region continuous to the screw in the screw extruder by the addition in the step, and mixing and dissolution in a static mixing region including a static mixing element by addition of at least one solvent after the second stage. A continuous production method of a reticulated fiber, wherein melting is performed.

The most important feature of the present invention is that the use of a screw extruder and a static mixing element makes it possible to easily and stably obtain a high-temperature, high-pressure uniform polymer solution useful for flash spinning. It is. As a result, it is possible to solve the problem of solution leakage at high pressure, easily dissolve the polymer, even if it has a high molecular weight, if the polymer can be easily set to high pressure and melt-supplied by a screw extruder.

That is, while using an extruder to block the entrance of the polymer dissolution zone with a molten polymer, the polymer and the solvent are separated by a large shear force under forced stirring in a region of mechanical mixing continuous with the screw of the extruder. By mixing, dissolving, and adding a static mixing area consisting of static mixing elements,
A stable solution for flash spinning was obtained quickly and without leakage of liquid from the sliding part even at high pressure. For this reason, dissolution occurs in an extremely short time, and the effect of remarkably preventing polymer deterioration can be exerted.

For the first time, high molecular weight polymers, in particular high molecular weight polymers which are susceptible to degradation in flash spinning, can be used. The terms used in the present invention will be briefly described. "Polymer dissolution zone" refers to a state in which the polymer is in a molten state, and a state in which the solvent and the polymer start to dissolve in a state in which the solvent and the polymer start to dissolve in a state in which the solvent and the polymer start to dissolve. Means an area that is in a mixed state.

The term "blocking" refers to a state in which the gap is filled with a molten polymer and contains no solvent, and no solvent can enter. "Mixing / dissolving" indicates a state in which the polymer and the solvent are mixed and both are being dissolved. "Mechanical mixing" refers to mixing that occurs when there is an element that forces liquid agitation and that element is driven by an external drive source.

"Static mixing" is mixing using a static mixing element, and means mixing in which the mixing element has no external driving source and has no sliding portion. The term “polymer solution” means a thermodynamically uniform one-phase liquid that does not contain a polymer as a pure component and a solvent. The contents of the present invention will be further described. In the present invention, a thermoplastic polymer is used as a polymer, and a screw extruder usually used in the production of fibers, films, and various other extruded products can be used as a continuous supply means.

That is, the screw extruder has a drive motor
It consists of a speed reducer, a hopper for supplying polymer, and a barrel for heating and melting the polymer. The barrel is equipped with a heater and can be heated. A screw is provided inside the barrel, and the screw is connected to a drive motor through a thrust bearing and a speed reducer. The screw can be divided into three main sections, a feed section, a compression section and a metering section, and the polymer is propelled towards the outlet while being preheated in the feed section. It melts while being compressed in the compression section and reaches the measuring section. The extruder used in the present invention includes:
A solvent injection port is provided in the measuring section where the polymer is completely melted, and a check valve is provided here. Via this valve it is connected to a high-pressure metering pump for the supply of the solvent. The solvent is pressed into the measuring section filled with the molten polymer coming from the screw supply section, and the polymer and the solvent are mixed and dissolved by the screw of the measuring section.

In the screw at the solvent injection part, it is preferable that the groove depth of the screw is slightly deeper than the front and rear groove depths in order to facilitate the addition of the solvent. By doing so, the pressure inside the barrel is lower than in the screw supply example,
Backflow and ejection of the solvent to the screw supply section can be prevented. The pressure of the mixing / solvent section can be freely changed by changing the size of the nozzle on the outlet side of the extruder.
Thereby, a pressure suitable for the type and molecular weight of the polymer can be obtained. Also, the residence time of the polymer in this portion can be freely changed by controlling the length of the screw. That is, pressure, temperature, mixing shear force and residence time can be freely set in order to optimize the polymer / solvent system in the mixing / dissolving area of the extruder, resulting in a uniform polymer solution. Can be easily and stably obtained.

The solvent / polymer of the flash spinning system is only dissolved at high pressure. Therefore, the preparation of the polymer solution necessarily requires a high-pressure vessel. In particular, a high pressure vessel under a temperature condition of up to 350 ° C. is required. Further, a high-pressure vessel with stirring is required. At this time, a difficult problem of sealing the movable shaft is encountered. High molecular weight in flash spinning system,
For example, high density polyethylene has a melt index (MI) of 4 or less (weight average molecular weight of 100,000 or more), and polypropylene has a melt flow rate (MFR) of 2 or less.
If it is attempted to use a molecular weight of 0 or less (weight average molecular weight of 150,000 or more), it is necessary to increase the pressure. If the pressure is not high, not only the molecular weight to be used is limited, but also a relatively low molecular weight requires a long time for dissolution, resulting in deterioration of the polymer.

The present inventors have developed a technique called liquid sealing with a molten polymer, and have solved this problem. More specifically, the space formed by the extruder barrel and the screw is filled with the polymer to prevent the ejection of the solvent gas. What is important in this case is that the space is filled with the molten polymer and is flowing toward the front of the screw, so that a pressure gradient is created.

The situation of this question will be described in more detail as follows. By Zeher Tadmor & Im Rich Klein of the United States
"Engineering Principles of Plasticating Extrudor"
(Published by Van Narstrand Reinhold Company)
As described in detail in 107 and p359-p400, operating conditions always produce a local maximum in the extruder. More specifically, when the screw is divided into a feed section, a compression section, and a metering section, a local maximum of pressure occurs before and after the starting point of the metering section after the polymer melts. After this maximum, the pressure gradually decreases. In particular, if the depth of the screw groove of the metering section is made deeper than the compression end point corresponding to the minimum groove depth of the compression section, the pressure usually drops, and the pressure is almost always required near the compression section end point. A maximum occurs. This pressure is used to seal the solvent.

Therefore, it is necessary to devise the dimensions of the screws used. That is, in order to complete the melting, the length of the supply section is made to be somewhat long. In most cases, the diameter of the extruder and the pitch of the screw screws are the same, and a preferred example of the screw dimensions will be described below in this example. The length of the supply section is at least 7 pitches, preferably at least 9 pitches.

The compression ratio of the screw is important for pressure formation. When the polymer is supplied in the form of pellets, the compression ratio is preferably 3.0 or more, and in the case of powder, it is preferably 4.0 or more.
Normally, the length of the compression portion is sufficient to be 5 pitches, but preferably 7 pitches or more. As for the end point of the compression section, a so-called mixing zone (mixing zone) may be provided near the start point of the measurement section. This part is short and it is better to give it a high dedication.

The form of the metering section is preferably long because a solvent supply port is provided in this section. That is, the pitch is 7 pitches or more, preferably 8 pitches or more. The solvent supply port is preferably provided at the third or fourth pitch after the start of the metering section. Of course, there may be a longer length. Further, in order to facilitate the introduction of the solvent, the diameter of the screw at the portion having the solvent introduction port is reduced. That is, it is better to increase the groove depth. The length of this portion is desirably at least two pitches including a decrease or increase in the screw diameter.

Further, the groove depth of the measuring section is about 1 mm to 3 mm when the extruder diameter is 35 mmφ, and 2 mm when the extruder diameter is 65 mmφ.
From 4mm, 90mmφ from 2.5mm to 4mm, 1
For 20 mmφ, it is preferably about 3 mm to 5 mm, and for 150 mmφ, about 3 mm to 6 mm. Further, with respect to the gap generated between the outer diameter of the screw and the extruder barrel diameter, usually 0.1 to 0.1
0.8 mm is adopted, and it is better to make the gap narrower as the diameter is smaller.

The operating conditions are determined by the screw having the above-mentioned dimensions, the temperature, the number of rotations of the screw, and the discharge rate. That is, the extrusion operation is started, and the conditions of the screw rotation speed and the discharge amount at which the solvent is not ejected from the hopper port are determined by a trial and error method at a predetermined temperature. As an example of the discharge temperature, 200 ° C to 280 ° C for polyethylene and 230 to 300 ° C for polypropylene are selected. At this time, the pressure at the maximum pressure point in the extruder is preferably at least 100 kg / cm ² · G. Even if the pressure is less than this, the operation cannot be performed, but the pressure may fluctuate due to the fluctuation of the discharge amount and the like, and the solvent may be ejected.

This method is for obtaining a reticulated fiber from flash spinning. After passing through this step, (1) immediately supply it to a spinning device, (2) introduce it into the next mixing device, and spin it. Steps such as supplying to the spinning device and (3) mixing with a new solvent in the next mixing device and supplying to the spinning device are selected.

In the step (1), it is necessary to increase the hold-up volume of the mixing section of the present invention in consideration of the residence time required for mixing. However, this is the simplest process and is suitable. Alternatively, the step (3) is more preferable. In the present invention, a high-temperature and high-pressure solution of a polymer and a solvent is discharged by flashing with a spinning device to obtain a reticulated fiber. As the flash discharge method, a conventionally known technique may be used, and it is preferable that the flash discharge is performed by using a spinning assembly including a reduced pressure orifice, a reduced pressure chamber, and a spinning nozzle. The shape and structure of these devices can be arbitrarily selected.

The polymer / solvent system used in the present invention is at room temperature.
It does not dissolve at normal pressure but dissolves only at high temperature and pressure.
Therefore, as a general feature, they belong to a system that is hardly soluble in each other, and do not easily melt even at high temperature and high pressure. For this reason, it is preferred to provide a continuous mechanical mixing zone on the extruder screw. That is, by increasing the contact area between the polymer and the solvent, the dissolving area is increased and the polymer is promptly dissolved. One way to do this is to provide a special mechanical mixing section on the same axis as the extruder. The term "special" refers to a structure which is different from the screw structure of the feed, compression and metering sections of the extruder screw and which aims at improving the mixing and stirring effect. For example, a structure called dalmage corresponds to this.

In the present invention, the drive system of the extruder is one, and the screw of the extruder has a melt supply section and a special mechanical mixing section of the solvent, and the solvent in the middle portion of the barrel is provided in the barrel. It has an injection part. This extruder is a special screw with a mixing function, or a special structure with a solvent injection port added to the tip of a normal screw consisting of feed, compression, and metering parts used in normal melt molding. A barrel having a suitable mechanical mixing section may be added, or may be uniquely designed for use in the present invention.

In this preferred invention, the operation of supplying the molten polymer by the rotation of the extruder screw and mechanically mixing with the solvent separately supplied by a metering pump or the like by a special structure is continued. proceed. The extruder and the structure have one drive system, and the sliding part may have the same structure as that of a normal extruder. Department does not reach.

There are various types of structures and shapes having a mixing function used for mixing the molten polymer and the solvent, and these can be used in the present invention. That is, a damaging structure, a notched multi-threaded screw structure, a damping structure, a multi-row bottle structure, and the like may be used, and a combination of these may be used. Pins may be provided and combined with the structure. Further, the rotating body and the barrel may be polygonal to achieve a kneader effect. These are selected according to the type of polymer used, the melt viscosity, the type and mixing ratio of the solvent, and the like.

In the present invention, in mixing and dissolving the polymer and the solvent, a static mixing region is used in addition to the mechanical mixing region. That is, the static mixing region is formed of a static mixing element, has a pipe-like shape having a mixing function, and has no sliding portion. The type of the static mixing element is not particularly limited, and may be a conventionally known type or an improved type thereof. Examples of known types include Kenix Static Mixer, Sulzer Mixer, Toray High Mixer, and the like.

Therefore, in addition to mixing and dissolving by a large shear force under forced stirring in the mechanical mixing zone, mixing and dissolving in the static mixing zone becomes possible. It also has the effect of eliminating spots such as temperature and density (concentration) that occur during transport and distribution in the polymer dissolving region up to. This effect is shown by the examples and reference examples described later.

In preparing the solution for flash spinning, the degree of uniformity of mixing and dissolving of the polymer and the solvent may be considered in consideration of the mechanical mixing region and the static mixing region, and each may be designed. It is. According to the present invention, a high molecular weight polymer can be easily dissolved in a solvent without deteriorating in a short time and without deterioration under a high pressure in a liquid-free process, and a more preferable reticulated fiber can be obtained stably and continuously. Can be

As a preferred invention, all the solvent is added to the polymer dissolving zone immediately after being blocked with the molten polymer,
There is a method of mixing and dissolving in the mechanical mixing region and the static mixing region. As a further preferred invention, there is a method in which the addition of a solvent to the polymer dissolving region is performed in multiple stages, and each time the solvent is added, the solvent is mixed and dissolved with the polymer so as to sequentially lower the polymer concentration.

As the most preferred invention, the addition of the solvent to the polymer dissolution zone is multi-stage, and the mixing and dissolution are performed in the mechanical mixing zone by the addition of the solvent in the first stage,
There is a method in which mixing and dissolution are performed in a static mixing region by adding at least one solvent after the step. Hereinafter, the invention in which these solvents are added in multiple stages will be described.

In the above-mentioned conventional technology, a required amount of a polymer and a solvent are mixed and dissolved at once to obtain a solution having a predetermined concentration. However, this method requires a considerably long time for mixing and dissolving, especially for dissolving, and it is difficult to obtain a uniform polymer solution. The present inventors have made various considerations on this problem, and have found that the polymer / solvent system used for flash spinning is more easily dissolved as the polymer concentration is higher. I found it. As a result, a more preferable method of the extruder dissolution method of the present invention has been invented.

That is, as an example, a high-density polyethylene / CFC-11 (trichlorofluoromethane) system will be described. As shown in the phase diagram of FIG. 1, a polymer concentration of 15 wt% is more soluble than 12 wt%. It turns out that it is easy. It was found that the higher the polymer concentration, the easier the dissolution. This graph shows that it has an LCST-type phase diagram in polymer solution theory, and the behavior is consistent with the results of the present inventors' studies (edited by the Society of Polymer Science, Polymer Experimental Science, Vol. 11, " See Polymer Solution “p189-204,
Published by Kyoritsu Shuppan).

Therefore, the effect of the present invention can be more and more exerted by sequentially adding a solvent to the molten polymer in multiple stages and dissolving it in multiple stages to gradually lower the polymer concentration. In the method of adding a solvent using a pump or the like in multiple stages of the present invention,
After each solvent addition, it is preferable to add a mixing operation of the polymer and the solvent. The multi-stage addition of the solvent in the present invention means the addition divided into two or more stages, and the first stage is where the polymer and the solvent are merged first, and there is no limitation as long as the stage is two or more stages.

The means for adding the solvent after the second stage is not particularly limited, but it is preferable to use a static mixing element. That is, these devices are recommended as devices having sufficient mixing capability and no sliding portion, and the above-described static mixing element forming the static mixing region is used. In the present invention, the polymer is preliminarily mixed with a part of the solvent in the early stage of mixing, the viscosity is reduced, and the affinity with the added solvent is also increased. Are small and a homogeneous solution is easily obtained. Therefore, the degree of freedom with respect to the shape and the number of stages of the static mixing element is large and can be appropriately selected.

The polymer used in the present invention is not limited to a thermoplastic polymer, but may be any polymer having a fiber-forming ability. For example, polyolefins such as high-density polyethylene and isotactic polypropylene, or copolymers and mixtures thereof, polyesters such as polyethylene terephthalate and polybutylene terephthalate, copolyesters containing 50% by mole or less of a copolymer component, and nylon 6, polyamides such as nylon 66, or copolymers or mixtures thereof. Further, polyacrylonitrile and a copolymer thereof may be used. These may contain additives such as stabilizers, lubricants, crystal nucleating agents, foam nucleating agents and pigments added for various purposes within a range usually used.

In the present invention, an arbitrary solvent is employed depending on the polymer used. That is, a known polymer / solvent combination for obtaining a reticulated fiber from flash spinning can be used. Examples of the solvent include halogenated hydrocarbons such as methylene chloride, trichlorofluoromethane, and trichlorotrifluoroethane, ethanol, methanol, and hexagon. Alcohols such as fluoroisopropanol, and water are used. And these may be mixtures.

An object of the present invention is to obtain a reticulated fiber from flash spinning, and the amount ratio of the polymer and the solvent in the present invention can be arbitrarily selected within the range of this purpose. From this viewpoint, the polymer concentration of the spinning solution for obtaining the reticulated fiber is preferably 5 to 20% by weight. Therefore, in the method of adding a solvent in multiple stages according to the present invention, the amount of the solvent necessary for achieving the final polymer concentration of the spinning solution is divided and injected into the continuously supplied polymer. I do. Since the addition is performed substantially in multiple stages, a solvent amount in the range of 1 to 99% of the total solvent amount may be added in multiple stages. In the first stage, it is preferable to add 1 to 90% of the solvent, more preferably 5 to 80%. Then, the necessary remaining solvent is added at a later stage, and it is also optional to add these in a further divided manner, and the dividing method may be arbitrarily selected.

In the present invention, the polymer and the solvent
The high-pressure solution is discharged by flash to obtain a reticulated fiber.
The flash discharge may be performed using a conventionally known technique, and is preferably performed by using a spout assembly including a reduced pressure orifice, a reduced pressure chamber, and a spinning nozzle. The shape and structure of these devices can be arbitrarily selected.

Next, a specific example will be described in detail. For example, regarding flash spinning of a system of high-density polyethylene and trichlorofluoromethane, the molecular weight of the polymer used is expressed by a melt index (MI), which is a measure of 10 (weight average molecular weight,
About 70,000 or less, preferably 1 (weight average molecular weight, about 150,000)
Hereinafter, 0.8 (weight average molecular weight, about 16
10,000) or less, 0.05 (weight average molecular weight, about 400,000)
Can be used up to

As a particularly preferable range, a melt index of 1.0 to 0.1 can be recommended. A particularly preferable range is 0.8 to 0.3 in melt index. This polymer is melted in an extruder at a temperature in the range of 200 ° C to 300 ° C. The heating temperature of the extruder needs to be set higher as the melt index decreases. The screw shape to be used may be a regular pitch structure in which the screw pitch and the screw diameter are commonly used,
For polymers of high molecular weight (small MI), the length of the feed section must be increased. In addition, a screw mixing zone may be provided at the end of the compression section and at the start of the metering section to easily and quickly perform melting to complete the melting.

When the melting is completed, the polymer enters a polymer dissolving zone. There is a solvent injection port in the polymer dissolving area, from which a solvent is injected. The injection pressure of the solvent is determined according to the pressure in the polymer dissolution zone. The pressure in the polymer dissolution zone is important for preparing a uniform polymer solution. Therefore, it is determined according to the molecular weight of the polymer. The pressure in the polymer dissolution zone is determined according to the molecular weight, and the solvent injection pressure is determined correspondingly. Therefore, the maximum withstand pressure is increased (for example, 500 kg / cm
^It is preferable to use a pump that delivers a constant volume regardless of pressure. An example of this is a plunger pump.

The solvent to be injected may or may not be heated, but a little heating is preferred because mixing and dissolving can be performed stably. For example, depending on the type of solvent, trichlorofluorocarbon can be used at 50 ° C to 20 ° C.
The temperature range is 0 ° C. A check valve for preventing polymer backflow may be provided at the solvent inlet. The check valve may be of a commonly used structure, but preferably has a structure that is easy to clean when the polymer is clogged. The valve may be further heated.

Next, regarding the pressure in the polymer dissolving zone, this zone starts from a point completely filled with the molten polymer, that is, a little before the inlet of the solvent, a few pitches before the screw pitch of the screw. It is the area from the beginning to the decompression chamber orifice. This pressure is as follows when the polymer is high density polyethylene. That is, if the polymer has a melt index (MI) of 5.0, 150 kg /
^{cm 2 · 350kg / cm 2 ·} G order of G, the polymer if 160~360kg / cm ² · G of about 1.2, if 0.8 polymer 170~400kg / cm ² · G, if 0.3 200 to 450 kg / cm ² · G, exceeding 0.3 and 0.03
Mixing and dissolving are sufficiently performed by applying a pressure of 250 to 500 kg / cm ² · G up to the order.

In general, not only high-density polyethylene but also a higher molecular weight of the polymer requires a higher pressure in the polymer dissolution zone. Therefore, including screw extruders,
The pressure resistance of each device such as a special mechanical mixing unit and static mixing unit must be sufficiently high. Generally, pressure resistance is 200-7.
Preferably, it is 50 kg / cm ² · G. Therefore, it is necessary to pay close attention to the seals at the flanges and at the detection ends of the pressure and temperature. A metal hollow O-ring type is easy to use as a seal for the flange portion. A metal contact type is convenient for the detection end seal.

In the sealing in the screw axis direction, fluid sealing is performed with a molten polymer. Therefore, at least at the screw pitch of the screw, the pressure at the position one pitch before must be higher than the pressure of the solvent injection section. For this reason, the space volume of the solvent injection section is preferably larger than the space volume of the portion on the extruder hopper side. In other words, it means to increase the groove depth. By this measure, the pressure immediately before the solvent injection port is higher than the pressure in the polymer dissolution zone.
Due to this pressure gradient, the solvent is completely sealed and does not flow backward or blow out to the hopper side.

At the solvent injection section, the polymer and the solvent merge,
Subsequently, it flows into a special mechanical mixing section. This portion forms the same axis as the screw shaft in a preferred form. Therefore, the rotation speed is the same as the screw rotation speed.
Burning, and this mechanical mixing section usually has no pumping capacity,
Mainly the mixing and stirring function. Therefore, the pumping capacity is borne by the screw extruder and the solvent pump. The pumping capacity of the screw extruder is in the screw metering section. Therefore, it is necessary to increase the length of this portion as the pressure in the polymer dissolution zone increases.

The temperature of the mechanical mixing section may be set lower than the temperature of the screw extruder. In particular, since the polymer / solvent system to be flash-spun is an LCST solution as described in the polymer solution theory as described above, it exhibits a low-temperature / high-pressure dissolution behavior, so that it is not necessary to raise the temperature of this portion more than necessary.
An appropriate temperature is also preferable from the viewpoint of preventing polymer deterioration. In the example of high-density polyethylene, it is 170-220 ° C,
More preferably, it is 180 to 200 ° C.

Although the length and form of the special mechanical mixing section are various as described above, it is preferable to increase the length in view of the mixing ability. The form is preferably a talmage type, a kneader type, or a barrier type. However, when this form is employed, particularly when the length is increased, the load increases and mechanical heat generation tends to increase. In order to suppress this heat generation, a part thereof may be changed to a pin type mixed structure.

In general, it is preferable that the larger the discharge amount and the higher the molecular weight of the polymer, the longer the length of this portion. When the solvent is added in multiple stages, the first stage is to add the solvent to the special mechanical mixing section. In this case, it is necessary to consider the distribution of the amount of the solvent added. Generally, as the molecular weight of the polymer increases, it is better to increase the amount of the first-stage solvent added. Unless a particularly serious obstacle occurs, it is preferable to add a solvent of an equal distribution system in order to make the solvent pump type used at each addition point the same.

In the high-molecular polyethylene / CFC-11 system, the amount added in the first stage is preferably set to 10 to 70% of the total amount. A gear pump may be provided after the special mechanical mixing section. The form of the gear pump may be the one usually used for extrusion molding. Of particular note is the gear pump shaft seal. The viscosity of the mixed polymer solution in this portion is about 30 to 500 poise, which is higher than that of a general fluid. Therefore, a normal ground seal can be used.

As a more preferable sealing method, a small amount of the solution may be leaked at the initial stage. This is because the polymer precipitates and fills the gap between the shafts due to the leakage, and the polymer functions as a lubricant. Further, by installing a gear pump, the pressure in the subsequent region can be further increased, and the degree of dissolution can be freely controlled. In particular, the pressure of the special mechanical mixing section can be freely controlled by the rotation speed of the gear pump. Therefore, by increasing the pressure in this portion, dissolution at a higher pressure can be performed, and dissolution can be accelerated. Since the setting of these pressures varies depending on the types and amounts of the polymer and the solvent, the optimum values may be set by a trial and error method.

Subsequently, the process reaches the second-stage static mixing section. Although a solvent injection port may or may not be provided before the second-stage static mixing section, it is more preferable to provide an injection port. It is important to design the structure of the solvent injection port so that the mixed polymer solution from the previous stage and the newly added solvent are uniformly distributed over the entire cross section of the pipe.

Because the static mixture is a laminar mixture, if the viscosity ratio of the fluids to be mixed is remarkably different, the concentrated addition of the solvent results in insufficient mixing, incomplete dissolution, and unfavorable results. give. For this reason, it is made to distribute uniformly over the entire cross section. For example, it is preferable to use a perforated plate to discharge the mixed polymer solution from the previous stage into a solvent as if it were "Somen", or to provide a number of solvent outlets in the cross section of the pipe.

The static mixing element requires at least 40 stages, so that even if the pressure loss per static mixing element is small, the pressure loss as a whole is considerable. Therefore, it is not necessary to collectively support each unit, collect all the stages, and collectively support at the outlet side. Unless such measures are taken, buckling may occur at the final stage. The temperature of the piping system including this static mixing element may be lower than that of the previous stage. Since the temperature of the polymer solution is determined in this portion, it is preferable to lower the temperature unless a trouble occurs. 160-200 ° C., preferably 170-200 ° C. in the case of high density polyethylene
180 ° C.

Of further note is the pressure of the polymer solution leaving the final mixing section. The pressure in this part directly affects the pressure in the decompression chamber and immediately affects the spinning state.
Significant fluctuations in pressure at the end of the last stage mixer indicate that the polymer is not yet completely dissolved in the solvent. Therefore, if the pressure fluctuation range is large, it is necessary to further increase the number of mixing stages or the number of solvent addition stages.

Generally, the pressure fluctuation width immediately after the final mixing stage and immediately after the decompression chamber is preferably 5 kg / cm ² · G or less, more preferably 3 kg / cm ² · G or less. A filter may be provided at the final stage of mixing and immediately before the hydraulic chamber. Although there are various types of this filter, a filter having a large filtration area and a small pressure loss is preferable. Generally, it is preferable to use a pleated or disk type surface filtration system.

Further, the piping system including the mixing area has a structure in which a stagnation portion is not generated as much as possible. If there is a blind spot that causes stagnation, a degraded polymer is generated, and the degraded material falls off and clogs the hole of the orifice. This has very negative consequences. Further, a narrow gap is not generated between the flange portion and the detection end including the extruder system. When the polymer solution enters this portion, stress corrosion occurs, cracks are generated, and the polymer solution may squirt out there. In order to prevent this corrosion, a material having high corrosion resistance may be used.

Subsequently, the process reaches the flash spinning section. This part consists of a decompression chamber orifice, a decompression chamber and a spout orifice. The shape, dimensions, and the like of this portion are the same as those of a conventionally known technique. However, the orifice size is determined in consideration of the pressure in the polymer dissolution zone and the pressure in the decompression chamber.
Furthermore, it is the vacuum chamber pressure and temperature that ultimately determine the spinning state. As for the pressure and temperature of this part, in the case of high-density polyethylene, 40 kg / cm ² · G to 1
50 kg / cm ² · G and 150-190 ° C. The optimum values of the temperature and pressure vary depending on the operating conditions, and are particularly affected by the polymer molecular weight. Basically, in some sense, the disadvantage of phase separation arises,
The conditions of the decompression chamber are determined in consideration of the operating conditions and the phase separation state. For this purpose, it is an essential requirement to measure the phase diagram of the polymer / solvent system.

In the above description, high-density polyethylene has been mainly described as an example, but the same can be said for polypropylene. That is, for polypropylene,
The melting point of the polymer is different from the former. Further, the pressure in the polymer dissolution zone is different. Further, the polymer is more likely to deteriorate.
If these points are set to be suitable for polypropylene, flash spinning can be performed in the same manner as high-density polyethylene.

The molecular weight used for polypropylene is determined by the melt flow rate (MF) measured at a temperature of 230 ° C. under a load of 2,160 g according to JIS-K7210.
R), 20 (weight average molecular weight, about 15
10,000) to 0.3 (weight average molecular weight, about 500,000).
More preferably, the melt flow rate is from 5 (weight average molecular weight, about 240,000) to 0.5 (weight average molecular weight, about 45
10,000).

For example, in the case of polypropylene / trichlorofluoromethane (CFC F-11), the polymer concentration is 5%.
More preferably, it is 8 to 15% by weight. The heating and melting temperatures are 250 to 300 ° C in the extruder section, 190 to 230 ° C in the special mechanical mixing section, and 180 in the static mixing section.
-220 ° C, 190-220 ° C in the decompression chamber, the pressure in the polymer dissolution zone is 150-300 kg / cm ² · G, and the pressure in the decompression chamber is 50-150 kg / cm ² · G.

Furthermore, flash spinning can be performed in the same manner as described above for general plastic polymers as well, as long as the inherent characteristics of the polymer such as the melting point are considered. Furthermore, when additives are added to each polymer / solvent system, the pressure and temperature change. The properties of these can be determined by measuring the phase diagram, and if this is taken into consideration, the same method can be used for the flash spinning by the above-described method.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 2 shows a flowchart for reference of the present invention, and FIG. 3 illustrates this or the inside of a screw extruder used in the present invention. That is, in FIG. 2, an extruder 11, a barrel 10, a solvent pump 13, and a spinning device 14 are provided. The polymer is melted in the extruder 11 and sent to the polymer dissolving zone closed by the molten polymer in the barrel 10. A solvent is sent from a separate solvent pump 13 into the polymer dissolving zone through a polymer check valve. The solvent and the polymer are mixed and dissolved by the rotating screw in the barrel to form a uniform polymer solution and sent to the spinning device. This spinning device has a decompression orifice, a decompression chamber and a spout orifice,
It consists of a heating device, in which the polymer solution is spun through a spout orifice to a low pressure region and becomes a continuous reticulated fiber.

Looking in a little more detail inside the extruder barrel,
As shown in FIG. 3, there is a screw 1 in the barrel, and this screw comprises a supply section 6, a compression section 5, and weighing sections 4, 3, 2. Looking more closely at the metering section, the metering section 4 is filled with the molten polymer coming from the compression section 5 and the solvent cannot flow back to the hopper opening 7.
In addition, the weighing section 3 has a larger groove depth than the front section 2 and the rear section 4, and therefore forms a minimal pressure portion in the weighing section. To this end, the solvent from the solvent inlet 8 is easily injected into the extruder barrel. The molten polymer coming from the metering front part 4 and the solvent coming from the inlet 8 are mixed and dissolved by the rotation of the screw in the metering rear part 2 and flow out from 10 as a polymer solution. The metering units 2, 3, and 4 are appropriately optimized depending on the polymer flow rate and the solvent flow rate.

FIGS. 4 and 5 show a preferred embodiment of the extruder used in the present invention. FIG. 4 shows the structure of an extruder used in the practice of the present invention and a special mixing structure (mixing mixer) coaxial with the screw. In this apparatus, the polymer is supplied from the polymer inlet 24 and is melted by the screw 21 by the rotation of the driving system 26, and is forwardly (rightward in the figure).
Extruded. On the other hand, a solvent is added from a solvent injection port 25 provided in the barrel 23, and a mixed structure (Dalmage type) is formed.
The two are mixed by 22 and reach the mixture outlet 27.

FIG. 5 is a structural view showing a case where mixed structures (Dalmage type and pin type) 22 ′ and 22 ″ having a shape different from FIG. 4 are provided. The resulting mixture is guided to a spinning device as it is, or after that, a solvent is further added and a mixing operation is performed, and the mixture is then guided to a spinning device to obtain a reticulated fiber.

The diameter of the extruder screw is selected according to the production amount of the reticulated fiber to be produced, and the diameter of the structure having the same shaft may be the same as or different from the screw diameter of the extruder. Further, in each case, the length of the structure is arbitrarily determined arbitrarily from the required mixing degree and the hold-up volume in consideration of the residence time. 6 and 7 are schematic flow sheets showing an embodiment of the present invention.
1 is an extruder, 10 is a barrel, 12 is a special mixing section on the same axis as this, 13 is a solvent pump, 14 is a spinning device, 1
Numeral 5 denotes a mixing section comprising a static mixing element.

FIG. 6 shows an example of multi-stage mixing, that is, the polymer is mixed and dissolved in the special mixing section 12 and further mixed and dissolved in the static mixing section 15. FIG. 7 shows a process in which a solvent is added in multiple stages and mixed and dissolved for the sake of convenience. That is, the solvent is added and mixed and dissolved in the first-stage mixing section 12 from the first-stage solvent pump 13, and further the solvent is added and mixed and dissolved in the second-stage mixing section 15 from the second-stage pump 13 to obtain a polymer having a predetermined polymer concentration. Obtain a polymer solution.

[0080]

EXAMPLES The present invention will be specifically described below with reference to examples. In addition, the filament strength in the example is a grasp length 5c.
m, and a tensile speed of 10 cm / min, and was measured on a filament sample twisted 4 times / cm. In accordance with the flow chart shown in Reference Example 1 2, (referred to as A ₁ method) The method using an extruder screw shown in FIG. 3 and law using an extruder screw and the special mixing structure shown in FIG. 5 (A
Flash spinning was carried out by the method ₂ ).

[0081] The extruder shown in Figure 2 is a barrel diameter 35 mm, screw used in A ₁ method will be described with reference to reference numerals of FIG. 3, the length of the feed section of the code 6 316 mm (9
Mountain), groove depth about 5mm, length of the compressed part with reference numeral 5 is 245mm
(7 mountains), the length of 140 mm (4
Mountain), groove depth 1.6 mm, length 70 of solvent-added part with reference numeral 3
It has dimensions of mm (two peaks), groove depth 3 mm, length 2 of the rear metering part (mixing / dissolving part) of 140 mm (four peaks), and groove depth 1.6 mm. A screen device was attached to the tip of the extruder, and a spinning device was attached via piping. Vacuum chamber orifice diameter of spinning device, 0.5mmφ, volume of vacuum chamber about 2c
c, spinneret orifice diameter 0.5 mmφ.

The supply of the solvent to the extruder was performed through the inlet 8 using a double plunger pump. High-density polyethylene having a melt index (MI) of 5.0 (weight average molecular weight, about 90,000) (Suntech J, manufactured by Asahi Kasei Corporation)
-240) and Freon-11 (trichlorofluoromethane, CCl ₃ F) using a polymer solution having a polymer concentration of 11% by weight. That is, the barrel temperature of the extruder is set to 23
At 0 ° C., the operation was performed at a screw rotation speed of 50 rpm at a polymer flow rate of 77 g / min and a solvent flow rate of 623 g / min. The heating temperature of the piping and the spinning device after the extruder tip was 175 ° C, and the heating temperature of the solvent was 100 ° C. At this time, the liquid temperature immediately before spinning was 175 ° C., and the most important pressure in the decompression chamber was about 40 kg / cm ² · G. The spinning state is extremely stable, and the pressure fluctuation range of the decompression chamber is 4 to
It was 5 kg / cm ² · G. The strength of the obtained reticulated fiber was 3.5 g / d.

The pressure at the extruder tip is about 200 kg / cm ²
-It was G, but no solvent leakage occurred from anywhere.
Although a hollow metal O-ring was used for sealing the flange portion, no solution leakage occurred. The discharge rate was further increased, and the polymer flow rate was 110 g / min, and the solvent flow rate was 890 g.
/ Min, the pressure fluctuation in the decompression chamber became extremely large, and the value exceeded 10 kg / cm ² · G, making stable spinning practically difficult.

[0084] then carried out the spinning of A ₂ method. The shape of the special mechanical mixing section used is modeled in FIG. Indicating the dimensions of each part, the screw dimensions are: position length / depth = 3
15mm / 5mm, compression part length / depth = 315mm / 5 → 16
mm, measurement part length / depth = 245 mm / 1.6 mm. The shape of the dalmage part is a polymorphic screw structure, the length is 210 m
m, the diameter is about 50 mmφ, the screw used is 16 threads, has a semicircular groove, the groove depth is 3.6 mm (maximum), and the helix angle is 35 ° to the right. Furthermore, the shape of the pin mixing section is a multi-row array of cylindrical pins, and has a length of 285 mm and a diameter of about 50 mm.
At φ, the pin arrangement is 8 × 17 rows. In this pin mixing part, pins of the same shape are planted in the same 8 rows and 17 rows on the barrel side as well as when the pins are planted on a shaft coaxial with the screw. A movable pin on the same axis moves to mix the polymer and the solvent. The gap between the barrel and the movable pin shaft is 7 mm.

[0085] was flash spun at exactly the same method and conditions as the A ₁ method. Even when the total discharge amount was 1000 g / min, that is, the flow rate of the polymer was 110 g / min and the flow rate of the solvent was 890 g / min, the spinning was extremely stable, and a reticulated fiber of 3.6 g / d was obtained.
At this time, the pressure in the decompression chamber was 55 kg / cm ² · G, and the pressure fluctuation range was 4 to 5 kg / cm ² · G. The pressure at the extruder tip was about 250 kg / cm ² · G, and no solvent leakage occurred from anywhere.

Example 1 Flash spinning was performed by the method (Method B) shown in FIG.
That through the next pipe screw extruder A ₂ method described in Reference Example 1, it was placed a mixed system consisting of static mixing elements which corresponds to the reference numeral 15 in FIG. 6. The static mixing element used is a mixer SMX type manufactured by Sulzer (nominal diameter 15 mmφ)
In the form, the metal strips are welded in a girder shape and they are 90 °
They are connected at different angles. This was used in 50 stages.

As the spinning method, high-density polyethylene having a melt index of 1.2 (weight average molecular weight, about 140,000) (Suntech B-161 manufactured by Asahi Kasei Corporation) and Freon-1
1 was used. The temperature of the screw extruder 230 ° C., the temperature of the special mixing section A ₂ method 20
The temperature of the pipe and the static mixing section was 175 ° C., and the polymer concentration was 11% by weight. Polymer flow rate 77g /
And the solvent flow rate was 623 g / min and the total discharge amount was 700 g / min. The liquid crystal just before spinning was 175 ° C., and the pressure in the decompression chamber was 70 kg / cm ² · G. The spinning state was extremely stable, and the pressure fluctuation in the decompression chamber was also ^{2 to 3} kg / cm ² · G. The strength of the obtained reticulated fiber was 3.8 g / d.

Example 2 Flash spinning was performed by the method (Method C) shown in FIG.
That is, according to the method described in Example 1, a solvent injection port was provided between the tip of the extruder unit and the static mixing unit 15 and connected to a double plunger pump. Therefore, the polymer dissolved in the extruder reaches the polymer dissolution zone. A solvent is added to this region from a plunger pump, and the polymer and the solvent are mixed in the special mixing section 12 to dissolve the polymer. Further, the mixed solution reaches the static mixing zone from the extruder tip. During this time, a solvent is further added. The polymer / solvent mixed solution reaches a static mixture, and is discharged from the spinneret as a completely uniform polymer solution for mixing and dissolving.

When the melt index is 0.8 (weight average
High density polyethylene (Asahi Kasei Corporation)
Polymer consisting of N-Tech S-160) and CFC-11
Spinning was performed using a polymer solution having a concentration of 11% by weight.
Extruder temperature 270 ° C, special mixing unit temperature 200 ° C, static
The temperature of the mixing section is 175 ° C and the temperature of the spinning section is 175 ° C.
Was. In addition, decompression chamber nozzle 0.5mmφ, decompression chamber volume about 2cc,
The spinning nozzle was 0.5 mmφ. The pressure in the special mixing section is 25
0kg / cm^Two・ G, pressure of static mixing section 200kg / cm ^Two・ G
Were mixed and dissolved. The liquid temperature immediately before spinning decreased to 175 ° C.
The pressure in the pressure chamber is 80kg / cm^Two-Extremely stable spinning at G
done. The pressure fluctuation range of the decompression chamber is 2-3 kg / cm^Two・ G
To obtain a reticulated fiber having a good fiber form and a strength of 4.5 g / d.
Was.

The polymer flow rate at this time was 77 g / min.
The solvent flow rate was 623 g / min, and the addition amount of the solvent immediately before the special mixing section on the first stage was 77 g / min.
Immediately before the second-stage static mixing section, the remaining solvent flow rate is 546 g.
/ Min was added. Therefore, the first stage has a polymer concentration of 50 wt%, and the second stage has a polymer concentration of 11 wt%. Example 3 and Reference Example 2 A ₁ , A ₂ , B, described in Reference Example 1, Examples 1 and 2,
Using the method C, flash spinning was performed using high-density polyethylene having different melt indices and trichlorofluoromethane (CFC F-11).

The dissolved state of the polymer reacts with the pressure fluctuation immediately before the spinning, in particular, the pressure fluctuation in the decompression chamber. That is, as the dissolution of the polymer was incomplete, the pressure fluctuation in the decompression chamber became larger, and finally the spinning became impossible. Further, even if spinning was possible, undissolved polymer would be discharged if the pressure fluctuation width was large, and the fibers were swelled and the strength was too low to be used.

Each method was compared using the pressure fluctuation width indicating the dissolution state, and the results are shown in Table 1. All polymers were high density polyethylene (made by Asahi Kasei Corporation). Solvent is CFC-
11 was used. The polymer concentration was 11% by weight, and the total discharge amount was 1000 g / min. The spinning conditions and apparatus used in Reference Example 1, Examples 1 and 2 were used.

As is evident from Table 1, the method A ₁
It is clearly shown that the more preferable spinning method is obtained by going to Method ₂ , and further to Method B and Method C.

[0094]

[Table 1]

The conditions and the like of an example of spinning by the C method using the prototype polymer (produced by Asahi Kasei Corporation, MI = 0.31, weight-average molecular weight of about 210,000) in this example will be described below. become. That is, the temperature of the extruder screw section was 300 ° C, the temperature of the special mixing section connected coaxially was 200 ° C, and the temperature of the piping and the static mixing section was 170 ° C. The pressure of the polymer melt zone, 250kg / cm ² · G in the special mixing section, 200kg / cm ² · G becomes in a static mixing unit, in order to control the pressure second section to, ahead of the special mixing unit A gear pump having an extrusion volume of 35 cc per rotation was installed.
This part was heated to 200 ° C. The pressure in the decompression chamber is 1
The pressure was 10 kg / cm ² · G, and the liquid temperature in the decompression chamber was 190 ° C.
The strength of the obtained reticulated fiber was 6.5 g / d.

Further, in any of the spinning examples, no leakage occurred from the flange portion or the like. Also, a small amount of polymer was positively leaked little by little from the rotating shaft of the gear pump for lubrication.

Example 4 and Comparative Example 1 The apparatus shown in Example 1 was used to spin a polypropylene which was easily deteriorated. That is, polypropylene K1014 (manufactured by Chisso Polypro, melt flow rate MFR = 3.5, weight average molecular weight = about 280,000) and K1011 (manufactured by Chisso Polypro, MFR = 0.7, weight average molecular weight = about 40)
) And spun with a trichlorofluoromethane solution having a polymer concentration of 9% by weight. The solution temperature at this time is 205 ° C
And the screw speed was 95 rpm. Thereby, a reticulated fiber having a good shape was obtained.

As Comparative Example 1, the same polypropylene solution was spun in a volume of 550 cc using an autoclave equipped with a stirrer. The liquid pressure chamber orifice, the decompression chamber, and the spinneret orifice were spun using the same ones as used in the extruder method. At this time, the rotation speed of the stirrer was 300 rpm, and it took 60 minutes to dissolve.
Further, the liquid temperature was 210 ° C. In contrast, the extruder took 7 to 8 minutes. Reticulated fibers were also obtained by the autoclave spinning method.

As a result of measuring the molecular weight of the fibers by the extruder method and the autoclave method by MFR, the values shown in Table 2 were obtained.

[0100]

[Table 2]

It can be seen that the present invention has significantly less polymer degradation than the autoclave method.

Example 5 Reticulated fibers made of high-density polyethylene were obtained by the process shown in FIG. Melt index (MI) is 0.
35 (weight average molecular weight, about 210,000) chips of high density polyethylene (Suntech HD: B871 manufactured by Asahi Kasei Kogyo Co., Ltd.) are continuously melt-extruded by an extruder, and trichlorofluoromethane as a solvent is added by a metering pump. And mixed in a special mixing section coaxial with the extruder. The structure of the extruder and the mixing section used at this time is as shown in FIG. 5, and the screw has a screw section, a dalmage section, and a pin section.
m, 250 mm, and the corresponding barrel ID is 3
They were 5 mmφ, 50 mmφ, and 50 mmφ. Then, a solvent inlet was provided in a barrel in front of the dalmage portion.

The amount of the polymer supplied at a screw rotation speed of 46 rpm was 74 g / min, and the amount of the solvent injected into the mixer was 240 g / min. This mixture was introduced into the static mixing section together with 360 g / min of the added solvent,
A solution having a predetermined polymer concentration was obtained. At this time, as a static mixing element, a mixer SMX manufactured by Sulzer (nominal diameter 15
mm) with 50 steps.

When spinning this liquid, 0.5 mmφ
(L / D = 10) decompression orifice, about 2cc decompression chamber,
A spinneret assembly comprising a spinning nozzle of 0.5 mmφ (L / D = 1) was used. The discharge state is extremely stable,
The tensile strength of the obtained reticulated fiber was 5.9 g / d.

Example 6 An example is shown in which the same operation as in Example 5 was performed on polypropylene. Melt flow rate (MFR) 0.7
Polypropylene (weight average molecular weight, about 400,000) (K1011 manufactured by Chisso Corporation) was used, and trichlorofluoromethane was used as a solvent.

In this case, the structures of the extruder and the special mixing section were as shown in FIG. That is, it has a screw part and a special mixing part (Dalmage) part, each length is 700 mm, 300 mm, and the inner diameter of the barrel is 35 mm each
φ. In this example, a static mixing element having a 40-stage Toray high mixer (nominal diameter: 25 mm) was used.

By the same operation as in Example 5, 90 g of polymer was obtained.
/ Min and the solvent (300 g / min) were mixed with a coaxial mixer with the extruder (screw rotation speed: 56 rpm), and the solvent was further added to 600 g.
/ Min and mixed with a static mixer. Then, it was spun from the same spinning device used in Example 5 to obtain a reticulated fiber. The state of discharge was extremely stable, and a continuous network fiber having a strength of 3.8 g / d and a uniform fibrillation form was obtained.

Table 3 shows the concentration and pressure conditions of each part in this example.

[0109]

[Table 3]

Examples 7 to 10 Table 4 shows the results of spinning under the operating conditions of Example 6 while keeping the total amount of solvent constant and varying the addition ratio.

[0111]

[Table 4]

Example 11 In the process shown in FIG. 6, the polymer / solvent system was the same as in Example 6. In this case, the structure of the extruder and the special mixing section was as shown in FIG. That is, it has a screw part, a dull mage part, and a pin part, each of which has a length of 7
The diameters of the barrels were 00 mm, 210 mm, and 250 mm, and the corresponding inner diameters of the barrels were 35 mm, 50 mm, and 50 mm.

As a static mixing element, 50 stages of a mixer SMX type (nominal diameter 15 mm) manufactured by Sulzer and 20 stages of a high mixer (nominal diameter 25 mm) manufactured by Toray were added, and the spinning apparatus was the same as in Example 2. Was used. In this case, when the operation was performed at a polymer injection rate of 900 g / min into the mixer coaxial with the extruder screw at 90 g / min of the polymer, the discharge state was stable with a pressure fluctuation range of 1-2 kg / cd in the decompression chamber. The form of the yarn was almost uniform, and the strength was 3.1 g / d. Table 5 shows the temperature and pressure conditions of each part at this time.

[0114]

[Table 5]

Comparative Example 2 Under the conditions of Example 11, only the mixer having the same shaft as the extrusion screw of the present invention was replaced with a conventionally known independently driven screw mixer to carry out the process shown in FIG. 35mm
The molten polymer was introduced into the screw mixer using an extruder of φ, while the entire amount of the solvent was introduced into the screw mixer. This screw mixer was a uniaxial kneading mixer having two inlets, having a projection on the barrel side of 35 mmφ and having a notch in the screw flight. The same static mixer and spinning device as in Example 7 were used, but in this example, leakage from the gland of the screw mixer occurred, and spinning was impossible.

[0116]

By adopting the spinning method and process shown in the present invention, it is possible to produce flash-spun high-strength reticulated fibers very safely. In other words, spinning using a high molecular weight polymer becomes possible, solution preparation at high pressure becomes possible, downsizing of equipment, elimination of process troubles due to leakage from the stirring seal section, stabilization of spinning system pressure, etc. A big effect is brought.

Since the mixing efficiency is increased and the dissolution at a high pressure becomes possible, the residence time may be short, and
Deterioration of the polymer and decomposition of the solvent are suppressed, and this also has the effect of stabilizing the product and reducing the cost of collecting the solvent. The obtained reticulated fiber can be developed for various uses by making it into a nonwoven fabric by utilizing its excellent strength, whiteness, reticulated structure and high specific surface area, or by using the fiber as it is.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram showing high density polyethylene (MI = 1, 2;
It is a phase diagram of a polymer solution from weight average molecular weight 140,000 and Asahi Kasei Suntech B-161 and trichlorofluoromethane.

FIG. 2 shows a flow sheet of a reference method.

FIG. 3 is a schematic diagram showing one example of a screw and a special mixing structure of an extruder used in the present invention.

FIG. 4 is a schematic view showing another example of a screw and a special mixing structure of an extruder used in the present invention.

FIG. 5 is a schematic diagram showing still another example of the screw and special mixing structure of the extruder used in the present invention.

FIG. 6 is a flow sheet of a flash spinning method according to one embodiment of the present invention.

FIG. 7 is a flow sheet of a flash spinning method according to another embodiment of the present invention.

FIG. 8 shows a flash-spinning flow sheet using a conventional screw mixer for comparison with the present invention.

[Description of Signs] 1,21: Screws 2, 3, 4: Metering unit 5: Compression unit 6: Supply unit 7, 24: Input port of hopper 8, 25: Solvent inlet 10, 27: Polymer mixture liquid outlet 22,22 ', 22 "... mixed structure

Claims (4)

[Claims] In a method for producing a network fiber made of a thermoplastic polymer by a flash spinning method, a polymer is continuously supplied to a polymer dissolution zone while being melted by using a heated screw extruder. The solvent is continuously added to the polymer dissolution zone while closing the inlet of the melted polymer supplied continuously, and a static mixing element comprising a mechanical mixing area continuous with the screw in the screw extruder and a static mixing element. And a polymer solution having a polymer concentration of 5 to 20% by weight is produced by mixing and dissolving the two under pressure using a static mixing region, and the polymer solution is reduced to a low pressure region through a nozzle provided at the outlet of the dissolution region. A continuous production method of reticulated fibers by a flash spinning method, wherein the fibers are continuously discharged. 2. The method for continuously producing reticulated fibers according to claim 1, wherein all the solvent is added to the polymer dissolving zone immediately after being blocked with the molten polymer. 3. The addition of a solvent to the polymer dissolving zone is multi-step, and each time the solvent is added, the solvent is mixed and dissolved with the polymer.
2. The method for continuously producing reticulated fibers according to claim 1, wherein the concentration of the polymer is sequentially reduced. 4. The method according to claim 1, wherein the addition of the solvent to the polymer dissolution zone is performed in multiple stages, and mixing and dissolution are performed in at least the first stage of addition of the solvent in a mechanical mixing region continuous with the screw in the screw extruder. Mixing in the static mixing region consisting of the static mixing element by adding at least one solvent after the second stage
4. The method for continuously producing reticulated fibers according to claim 1, wherein melting is performed.