JP2848718B2 - Manufacturing method of three-dimensional reticulated fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a process for producing three-dimensional polyolefin reticulated fibers using an improved flash spinning process. Furthermore, by using a solvent having an extremely low ability to destroy the ozone layer surrounding the earth, extremely high quality polyolefin three-dimensional reticulated fibers can be obtained.
It relates to an improved flash spinning method. Further, the present invention relates to a production method for obtaining a polyolefin three-dimensional network fiber having excellent strength and openability, which can be used for a nonwoven fabric sheet, by using a halogenated hydrocarbon having reduced ozone destruction ability.

[0002] In other words, an improved polyolefin three-dimensional reticulated fiber of extremely high quality can be obtained by using a solvent that inherits the excellent performance of non-flammability and non-toxicity of a specific fluorocarbon while significantly reducing the ozone depleting ability. Flash spinning method.

[0003]

2. Description of the Related Art A method for producing a three-dimensional reticulated fiber of a polyolefin is a flash spinning method. In this flash spinning method, a polyolefin is added to an organic solvent also referred to as a liquefied gas, the polyolefin solution is adjusted under high temperature and high pressure, and then the pressure of the solution is once reduced through a reduced pressure orifice to cause phase separation, thereby forming an opaque solution. This is a well-known spinning method in which the solution is further jetted through a spinneret into an atmosphere under normal temperature and normal pressure to form a three-dimensional network fiber.

[0004] That is, known techniques relating to the flash spinning method include those disclosed in USP 3,081,519, USP 3,227,794, and US Pat.
P3,227,784, USP3,467,744, USP3,564,088, USP3,756,441, EP-285670A1, EP-321567
A1 report, EP-357364A2 report, JP40-28125 report, JP42
-19520, JP-A-62-33816, JP-A-63-50512 and the like.

[0005] As the fiber obtained by the flash spinning method, polyolefin fiber is famous, and practically used fiber is almost limited to polyolefin fiber.
One use of this fiber is in synthetic pulp as a fibrid (short fibrous material), and another is used in a nonwoven sheet as a continuous three-dimensional network fiber like filaments.

[0006] The product produced by the process to which the present invention is directed is a three-dimensional reticulated fiber to be a nonwoven sheet. This non-woven fabric sheet is a so-called synthetic paper, and is a product that has water resistance, is strong, light, and does not lint. This is highly valued in the world,
Shows excellent practicality in airmail envelopes, floppy disk sleeves, oxygen absorber bags, desiccant bags, medical sterilization bags, building insulation dew condensation prevention cloth, reactor power generation work clothes, asbestos work clothes, etc., and social safety.・ It is said that it can contribute to the improvement of welfare.

[0007] In order to provide a product that satisfies the demands of society, a three-dimensional reticulated fiber that is high in strength and well opened is essential. This is because a dense and air-permeable uniform sheet cannot be obtained unless such fibers are used.

The present invention is also for responding to such a social demand. Specific products obtained from such three-dimensional network fibers include Tyvek (T.
yvek) and Luxer made by the applicant.

[0009] By the way, USP 3,081,519 includes solvents used in the flash spinning method for producing useful fibers as described above.
The following requirements are required as described in the bulletin. That is, the boiling point is at least 25 points higher than the melting point of the polymer used.
℃ low, inactive to the polymer during spinning, at a temperature and pressure suitable for adjusting the spinning solution, a solvent for the polymer, below the boiling point of the solvent, the polymer Dissolves less than 1%,
Phase separation immediately upon spinning to form a phase consisting essentially of a polymer, the polymer phase being substantially solvent-free.

Specific examples of the solvent include aromatic hydrocarbons such as benzene and toluene, aliphatic hydrocarbons such as butane, pentane, hexane, heptane and octane, and isomers and homologs thereof, and alicyclics such as cyclohexane. Group hydrocarbons, or unsaturated hydrocarbons, methylene chloride, carbon tetrachloride, chloroform, ethyl chloride, halogenated hydrocarbons such as methyl chloride, ethanol, methanol, alcohols such as hexafluoroisopropanol, esters, ethers, ketones, nitriles, Amido, trifluorochloromethane, fluorinated chlorinated aliphatic hydrocarbons such as 1,1,2-trichloro-1,2,2-trifluoroethane, sulfur dioxide, carbon disulfide, nitromethane, water and various liquid mixtures described above Etc. are known.

The most suitable solvent is selected from these solvents according to the spinning method used and the polymer used. In particular, as a method for spinning a polyolefin, a spinning method using a non-flammable, non-toxic trichlorofluoromethane, 1,1,2-trichloro-1,2,2-trifluoroethane, or the like, which is excellent in polymer solubility and spinnability. It is suitable. It is widely known that spinning methods using trichlorofluoromethane are among the best.

As described above, a large number of hydrocarbons or halogenated hydrocarbons are known as flash spinning solvents. However, in the case of flash spinning, the solvent must be gasified. Further, it is necessary to recover by an operation such as cooling and compression. Therefore, the conversion of the three-dimensional network fiber into a nonwoven fabric is performed in a large closed space. Otherwise, gas cannot be recovered. The size of the enclosed space is
For example, also in the scale of 2000m ^3. Filling such a huge space with combustible gas is extremely dangerous and practically impossible.

Further, a spinning head,
There are various types of machines, such as wire mesh conveyors and corona charging devices, for making non-woven fabrics, and in some cases, workers are forced to enter a closed space for repair and maintenance. Therefore, if the flash spinning solvent is toxic, it cannot be used.

From this point of view, although various types of solvents have been disclosed, the solvent that can be substantially used is trichlorofluoromethane (CFC-
11) There is only one. In fact, the only commercially available flash spinning method uses trichlorofluoromethane.

However, recently, all halogenated hydrocarbons in which all hydrogen has been replaced by chlorine and fluorine have been reported to have a very high ozone destruction ability as a specific freon (also referred to as chlorofluorocarbon or CFC). Production was banned. Naturally, the specific fluorocarbon, trichlorofluoromethane, 1,1,2-trichloro-
The flash spinning method of polyolefin using 1,2,2-trifluoroethane or the like cannot be used. Especially non-combustible
The inability to use trichlorofluoromethane, which is non-toxic and dissolves polyolefin well, is fatal to the flash spinning method, and a highly practical product cannot be obtained.

[0016] From such a background, a new spinning method without using trichlorofluoromethane, which is a preferable specific freon, has been proposed as a flash spinning method.

That is, JP-A-2-139408 discloses that a partially substituted halogenated hydrocarbon such as chlorofluoromethane, 1,1,1,2-tetrafluoroethane, 1,1-difluoroethane, Flash spinning using a mixture with 1,1,1,2-tetrafluoro-2-chloroethane, 1,1-difluoro-1-chloroethane, etc., and JP-A-2-160909 discloses that -Dichloro-2,2,2-trifluoroethane, 1,
2-dichloro-1,2,2-trifluoroethane, 1,1-dichloro
The spinning method using -2,2-difluoroethane, 1,2-dichloro-1,1-difluoroethane, 1,1-dichloro-1-fluoroethane, etc. is further described in EP-0407953A2, , 1-Dichloro-2,2,2-trifluoroethane,
A method of spinning using 1,2-dichloro-1,2,2-trifluoroethane or the like, and a method of spinning using methylene chloride and carbon dioxide gas are proposed in EP-357364A2. .

However, the disclosed spinning method includes:
When spinning with polyolefin, there are the following serious defects. That is, Japanese Patent Application Laid-Open No.
The methods disclosed in 139408 and EP-357364A2,
Not practically usable. Because methylene chloride is carcinogenic. As described above, such a toxic solvent cannot be used for flash spinning.

[0019] Further, in Japanese Patent Application Laid-Open No. 2-160909, which proposes the use of fluorocarbons instead of trichlorofluoromethane (CFC-11), only 1,1-dichloro-1-fluoroethane (HCFC-141b) is disclosed.
Only CFC-11 dissolves high-density polyethylene, which is a typical example of polyolefin, and other CFC-11 alternative fluorocarbons do not dissolve high-density polyethylene at all. Rather, hydrocarbons proposed as co-solvents are the main solvents, and the alternative CFCs are merely boiling point regulators. Looking at these cosolvents, it is inevitable to use methylene chloride Yabari from the viewpoint of flame retardancy or nonflammability.

Further, 1,1-dichloro-1-fluoroethane (H
Regarding CFC-141b), its thermal stability is remarkably inferior, and its ozone depletion ability is more than 0.1. In this way, the ones proposed so far, in which only methylene chloride can be used practically, have to be avoided from the viewpoint of toxicity. Even if it can be used, the three-dimensional network fiber of polyolefin obtained by the above proposed spinning method has low fiber strength and poor openability, and therefore cannot be put to practical use.

As described above, the feature of the nonwoven fabric sheet product made of the fiber obtained by the flash spinning method is that it is essential that the product is a light, strong, uniform and dense air-permeable sheet. This is the basis of social utility. Therefore, the proposed flash spinning method of polyolefin which does not destroy ozone cannot produce a practical product.

If the strength of the three-dimensional network fiber is low, the strength of the product itself is low, and airmail envelopes, floppy disk sleeves, medical sterilization bags, building insulation dew condensation preventing cloth, reactor power generation work clothes and asbestos work clothes As a matter of course, it is difficult to use such a fiber in the process of spinning, in which the fiber is cut, fluffed, or fibrid is generated. As a result, lint is generated and cannot be used at all for dust-free paper, floppy disk sleeves, medical sterilization bags, reactor power generation work clothes, asbestos work clothes, etc., which dislike the generation of lint.

If the spreadability is not good, the fiber does not spread in a net-like manner and becomes a sheet with many spots. It cannot be used for desiccant bags, medical sterilization bags, building insulation dew condensation prevention cloth, nuclear power generation work clothes, asbestos work clothes, etc.

An object of the present invention is to provide an improved socially useful polyolefin flash which can obtain a three-dimensional reticulated fiber having high strength and excellent spreadability by using a solvent having a low ozone depleting ability. An object of the present invention is to provide a spinning method. It is a further object of the present invention to provide an improved flash-spinning method which provides an excellent three-dimensional reticulated fiber using a solvent which is less flammable, less toxic and has a lower ozone depleting ability. In addition, it is an object of the present invention to provide an improved flash spinning method capable of spinning without greatly changing a conventional flash spinning apparatus.

[0025]

SUMMARY OF THE INVENTION The present inventors have developed a method for producing a fiber having a performance comparable to or surpassing that of a conventional flash spinning three-dimensional reticulated fiber while using a solvent having a low ozone depleting ability. After obtaining or conducting enormous research, they reached the present invention.

That is, in the method for producing a polyolefin three-dimensional network fiber according to the present invention, a high-temperature and high-pressure solution comprising a polyolefin and a solvent containing a halogenated hydrocarbon is prepared, passed through a vacuum orifice, a vacuum chamber, and a spinneret. A method for producing a fibrillated polyolefin three-dimensional reticulated fiber which is released to a normal pressure region, wherein a solvent comprising bromochloromethane and a hydrocarbon having 3 to 5 carbon atoms is used as a halogenated hydrocarbon. Then, a solution comprising the solvent and 5 to 25% by weight of polyethylene was adjusted to a pressure exceeding the cloud point curve represented by the temperature and pressure on the vertical and horizontal axes, respectively. It is characterized by pressure.

Bromochloromethane in a solvent consisting of the above bromochloromethane and a hydrocarbon having 3 to 5 carbon atoms, wherein the bromochloromethane is 5 to 45 mol%, and a hydrocarbon having 3 to 5 carbon atoms. Is preferably from 95 mol% to 55 mol%.

According to this method, the present inventors, unlike a conventionally known method, have extremely high strength and excellent openability, although they are low in ozone depleting ability and at least a nonflammable and non-toxic solvent. A three-dimensional network fiber of polyolefin was obtained.

As described above, flash spinning is based on the premise that an organic solvent which becomes a gas at normal temperature and normal pressure is used. That is, the polyolefin is dissolved under high temperature and high pressure, and then the pressure is once reduced to change the phase from a transparent liquid to an opaque liquid, and then the opaque polymer solution is blown 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 the gas jet, and becomes a fiber having high strength.

Therefore, the properties to be possessed as a solvent for flash spinning are disclosed as described above, but when examined in more detail, they are as follows.

At room temperature and normal pressure, the polymer is not dissolved at all, and the polymer is melted at a temperature exceeding the melting point of the polymer and at a high pressure far exceeding the normal pressure.

A phase change from a transparent liquid to an opaque liquid by a temperature exceeding the melting point of the polymer and not causing thermal deterioration. In particular, in the case of flash spinning, it is essential to use a polymer solution having an LCST (Lower Critical Solution Temperature) type phase diagram referred to in the theory of polymer solutions. The LCST phase diagram is detailed in a general polymer chemistry textbook or a polymer solution theory textbook.

Of course, the flash spinning solvent must also have an LCST phase diagram. Of course, it has an LCST type phase diagram, and its phase change must occur instantaneously. This property is important because flash spinning changes the phase from transparent to opaque with pressure.

At the moment of exiting the spinneret, it must be gasified. This means that it must have a boiling point near normal temperature and normal pressure. That is, the organic solvent must have a low boiling point. The change before and after the spinneret is approximately an isentropic change. Thus, the spinneret outlet is spontaneously a boiling liquid / gas mixture. If used as it is, it will not be used because it will be a wet mesh fiber. However, because the polymer has heat,
This amount of heat gasifies the liquid to form a dry reticulated fiber. This means that the heat of evaporation of the organic solvent must be adequate.

Organic solvents must have good thermal stability because they are exposed to high temperatures above the melting point of the polymer. It must be non-flammable or non-flammable because it fills a large volume of enclosed space. Humans often come into contact with the gas filled in the enclosed space and must be non-toxic. Since the entire flash spinning device becomes a high-pressure device, it is necessary that the corrosiveness is low.

Of particular importance are low boiling point, LCST type polymer solutions, non-flammable and non-toxic.

A great number of polyolefin flash spinning solvents are known to date. However, trichlorofluoromethane (hereinafter abbreviated as CFC-11) and similar alternative fluorocarbons, such as 1,1-dichloro-2,2,2-trifluoroethane (hereinafter abbreviated as HCFC-123), 1,2 -Dichloro-
1,2,2-trifluoroethane (hereinafter abbreviated as HCFC-123a), 1,1-dichloro-2,2-difluoroethane (hereinafter HCFC-123a)
-132a), 1,2-dichloro-1,1-difluoroethane (hereinafter abbreviated as HCFC-132b), 1,1-dichloro-1-
Four conditions other than fluoroethane (hereinafter abbreviated as HCFC-141b) and 1-chloro-1,1-difluoroethane (hereinafter abbreviated as HCFC-142b), namely, low boiling point, LCST type polymer solution, non-flammable, non-toxic There is no proposal that satisfies even partially.

The alternative CFCs are representative of polyolefins, and the high-density polyethylene, which is the most widely marketed flash-spun nonwoven fabric, is:
Not a solvent for high density polyethylene. The alternative CFC is simply a boiling point modifier when combined with other organic solvents,
It is just a combustion suppressant. In addition, one of the alternative CFCs
Some of the substances, such as 2-dichloro-1,1-difluoroethane (HCFC-132b), cannot be used due to their carcinogenic potential.

The present inventors have conducted numerous experiments to find a flash spinning solvent which satisfies at least the four conditions of low boiling point, LCST type polymer solution, non-flammable and non-toxic.

As a result, it was confirmed that an organic solvent composed of bromochloromethane (chlorobromomethane, methylenechlorobromide, CH ₂ BrCl) and a hydrocarbon having 3 to 5 carbon atoms satisfied the above four conditions. I found it.

A. Toxicity Regarding toxicity, ACGIH (American Conference of Governance)
nmental Industrial Hygienists) TLV (Threshold Limi
ts Values of Airbone Contaminants) is the indicator. Chlorobromomethane is 200 ppm, and hydrocarbons having 3 to 5 carbon atoms often exceed 500 ppm. The flash spinning solvents of the invention consisting of these solvents are at least above 200 ppm and are not completely non-toxic but have low toxicity. Take care of gas leakage and ventilation of the place, maintain the controlled concentration of the work place, and use an air line mask if touched by humans, without harming human health. This is the first time such a less toxic flash spinning solvent has been found with a flash spinning solvent other than trichlorofluoromethane (CFC-11).

B, Flammability With respect to the flammability, bromochloromethane has an extremely high combustion suppressing effect. In addition, the material itself is nonflammable. Hydrocarbons having 3 to 5 carbon atoms are combustible and have an explosive range. Combination with bromochloromethane makes it nonflammable depending on the composition. Even if it does not become nonflammable, the ignition energy becomes extremely high and it becomes a flame-retardant substance whose flash point disappears. The flash spinning solvent of the present invention has extremely low toxicity and is significantly less flammable than hydrocarbons. This is the first time such a flash spinning solvent has been found.

C, Boiling point The boiling point is preferably 60 ° C. or lower because of gasification at normal temperature and normal pressure. More preferably, it is 50 ° C. or lower. This boiling point is a function of the solvent composition and can be adjusted freely. The flash spinning solvent of the present invention can also be brought to a desirable boiling point by changing the mixing ratio of bromochloromethane and a hydrocarbon having 3 to 5 carbon atoms.

D, Cloud Point Curve The solvent used in the present invention becomes an LCST-type polymer solution when a polyolefin is dissolved therein. As described above, the basic principle of flash spinning is that spinning is performed by depressurizing a high-temperature and high-pressure polymer solution to cause phase separation to form an opaque liquid comprising at least two phases of a polymer and a solvent.
Therefore, the temperature and pressure of the cloud point 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 represented by the temperature and pressure at which the liquid changes from transparent to opaque. The cloud point is usually measured visually and varies somewhat with the measurement method. The transparency and opacity of the liquid also vary depending on the temperature, pressure, polymer concentration of the liquid, and the types of the polymer and the solvent constituting the system. Further, the method for preparing the solution, the measurement time, the light source, and the like are slightly changed. Therefore, although there is some variation, if the measurement method is fixed, observation can be performed with good reproducibility.

In polymer chemistry, a diagram in which the cloud points are stitched on temperature and pressure coordinates is called a cloud point curve. The suitability for flash spinning of the solvent can be determined from the position of the cloud point curve on the temperature / pressure coordinate plane. In the case of bromochloromethane alone, this cloud point curve exists at a low pressure where it can be formed in the temperature range of flash spinning, and cannot be observed unless the temperature is considerably high. The present inventors also attempted measurement, but the polymer and the solvent were thermally degraded and could not be actually observed.

However, a cloud point curve could be brought to a position suitable for flash spinning by combining with a hydrocarbon having 3 to 5 carbon atoms. Figure 1 shows examples of high-density polyethylene as polyolefin and 2-methylbutane and n-pentane as hydrocarbons together with CFC-11.
Shown in Furthermore, as a matter of course, it was also found that the position of the cloud point curve changes depending on the composition ratio of chlorobromomethane and hydrocarbon. This is shown in FIG. As shown in FIG. 2, as the bromochloromethane content increases, the position of the cloud point curve shifts to the low pressure side. This indicates that the thermodynamic properties of the polymer solution change depending on the solvent composition ratio.

Incidentally, the cloud point curve, which is an important factor in the present invention, is measured by the apparatus shown in FIGS.
FIG. 3 is an explanatory diagram of the entire apparatus, and FIG. 4 is an explanatory diagram of an optical cell container for measuring a cloud point. That is, two optical windows 2 are provided in an optical cell container (dimensions, 40 mmφ × 83 mm length, volume: about 100 cm ² ) 1 so that the inside can be observed through light. The length of the optical path through which the light passes is 9 mm for the glass 14 of the optical window 2, 18 mm because two are provided, and the thickness of the solution is 40 mm, so the total length is 58 mm. The optical cell container 1 has a built-in stirring blade 13 for stirring the inside of the container at about 180 rpm until the polymer is almost dissolved. The structure of the stirring blade 13 is such that two stirring blades are installed, and the axis corresponding to the optical window is formed in a U-shape so as not to disturb the optical observation. Further, a thermometer 4 is inserted so as to be in direct contact with the solution in the optical cell container. The pressure gauge 5 is provided in the middle of the pipe 9 and detects the pressure in the optical cell container. In order to adjust the liquid pressure in the optical cell container, a plunger-type pressure regulator is provided via a pipe 9. Further, a pipe 10 for venting gas in the optical cell container and pushing out the liquid in the container is provided. Further, the entire optical cell container is covered with an aluminum casting heater, and the temperature is controlled by a control circuit.

In the method for measuring the cloud point, first, the polymer and the solvent are measured and supplied to the container so that the polymer concentration becomes a predetermined concentration and the inside of the container becomes a liquid ring. Preparation of the polymer solution was performed on the basis of volume% for the purpose of simplifying the experiment. That is, the solvent was adjusted by measuring with a measuring cylinder so as to have a predetermined volume ratio and mixed. Volume changes due to mixing were ignored. The conversion to the molar ratio used the solvent density at normal temperature and normal pressure. In the case of high-density polyethylene, the polymer was charged into a measuring cylinder so as to have a predetermined volume%, and the conversion to weight% was a density of 0.96 g / cm ³ . Then, heating is performed, and as the liquid expands, the internal pressure of the container increases. In most cases,
The heating rate was 4.5 ° C./min. In this way, when the temperature reaches around the melting point of the polymer, the polymer starts to partially dissolve in the solvent. The polymer solution is adjusted in this state. The state of the liquid
After reaching a liquid pressure of about 50 kgf / cm ² and a temperature of about 105 ° C., the pressure was not adjusted until the polymer was completely dissolved.

Next, measurement of the cloud point is started. Find cloud point by changing temperature and pressure. The cloud point is determined by observing a change in the amount of light through an optical window or by using a photocell or the like, and when the visual field becomes dark or the light amount sharply decreases, the point is regarded as the cloud point. In this way, while increasing the temperature, the pressure was adjusted using a plunger type pressure controller, and the cloud point was measured. FIG. 2 shows a cloud point curve of bromochloromethane and n-pentane thus obtained. As can be seen from FIG. 2, as the bromochloromethane content increases, the cloud point curve shifts to a higher temperature side and its pressure decreases. When the content of bromochloromethane exceeds 45 mol%, the pressure of the cloud point curve becomes too low, resulting in a coarse three-dimensional network fiber, which cannot be used for the production of a nonwoven fabric sheet. Also, 5 mol%
When the temperature is further reduced, the pressure of the cloud point curve increases, and the effect of suppressing the combustion of bromochloromethane almost disappears, and the solvent becomes flammable. For these reasons, regions where the bromochloromethane content is below 5 mol% and above 45 mol% are not subject to the present invention.

Thus, a method for producing, for the first time, a polyolefin three-dimensional network fiber having good spreadability and high strength, which is practically usable, using a solvent having an extremely low ozone destruction ability has been found. Needless to say, a three-dimensional reticulated fiber which is always stable, has excellent spreadability, and has high strength can be obtained by using a solvent having a low ozone destruction ability. This industrial significance has immeasurable value.

The bromochloromethane used is preferably a pure product. Note the moisture content, the lower the better,
It is more preferable that the content is 10 ppm or less. Further, bromochloromethane is liable to be thermally degraded when exposed to a high temperature, so it is better to use a heat stabilizer. As heat stabilizers, 1,4-dioxane, 1,2-
Butylene oxide and the like.

Examples of the hydrocarbon having 3 to 5 carbon atoms include propane, n-butane, n-pentane, 2-methylpropane, 2-methylbutane, 2,2-dimethylpropane and cyclopentane. . Hydrocarbons have low purity, and in particular, the higher the carbon number, the lower the purity. The purity may be 70% or more, but is preferably 80% or more, and more preferably 95% or more. From the viewpoint of boiling point and purity, n-butane, n-pentane, 2-methylpropane, 2-methylbutane and the like are preferred.

As the polyolefin, polyethylene,
Examples include polypropylene and polymethylpentene-1.
Polyethylene is most preferably high density polyethylene,
The density is 0.94 g / cc or more. Furthermore, the copolymer component is
It is preferable to maintain the above density at 15 wt% or less.
The polypropylene preferably contains about 85 wt% or more of isotactic polypropylene, and may contain about 15 wt% or less of other polypropylene or copolymer components such as ethylene and butene. Further, commonly known polymer additives, that is, heat stabilizers, light stabilizers, lubricants, nucleating agents, crosslinking agents, plasticizers, fillers and the like may be contained in the polymer.

The apparatus used in the present invention may be provided with a solution adjusting device and a spinning device including a decompression orifice, a decompression chamber, and a spinneret. Beyond that, there are a device for opening and dispersing the mesh fibers, a conveyor device for moving the opened and dispersed mesh fibers into a sheet, and a winding machine for winding the formed sheet. The sheet forming section is housed in a closed box, and the solvent gas in the box is recovered. The solution adjusting device may be an autoclave device or an extruder. Or,
A conventionally known apparatus used for flash spinning of polyethylene can also be used.

Hereinafter, the contents of the present invention will be described with reference to examples. This example is intended to specifically show the content of the present invention, and does not limit the scope of the claims of the present invention.

The term “solution adjustment point” used in the examples indicates the temperature and pressure conditions when a polymer solution was produced, and can be indicated by a point on a cloud point curve diagram. Similarly, the spinning point indicates the pressure condition when the polymer solution is depressurized, phase-changed to an opaque liquid, and spun from the nozzle,
This term was used because it can be represented by points on the cloud point curve diagram.
What should be noted here is the temperature at the spinning point. The change from the solution adjustment point to the spinning point can be considered roughly as an isentropic change. Then, the liquid temperature should always drop. However, in the case of an autoclave experiment, since the spinning is completed in a relatively short time, this accurate detection cannot be performed. In addition, the polymer can be considered to have little change in temperature.
As a result, it can be assumed that the apparent temperature does not change roughly. However, this is not essential to the present invention and is not to be arrested.

The number of free fibrils appearing in the examples is a measure of the openness of the reticulated fiber.
If it is above, a dense and non-uniform non-woven sheet can be obtained. On the other hand, if it is less than 100, the sheet will be non-uniform and extremely uneven, and will not endure practical use at all. Those between 100 and 300 are somewhat unreasonable for advanced applications, but can be used satisfactorily for general applications that do not require very high performance.

The scale of the spreadability in the examples is as follows: “で あ れ ば” indicates that the number of free fibrils is 300 or more, and “△ − ○” indicates 1
Between 00 and 300, if it is "x", it is 100 or less. The number of free fibrils was measured as follows. The three-dimensional network fiber has a structure in which a large number of fine short fibers (single yarns) are connected in a network. The number of each fiber is
The greater the denier compared with the same denier, the better the opened fiber is. The number of free fibrils is measured using a spun yarn obtained by colliding the spouted gas jet with the fibers contained in a copper plate tilted at about 45 ° to a position about 25 mm from the tip of the spinneret while containing the fibers. . The sampled spread yarn is gently sandwiched between glass plates, and the number of single yarns in the field of view is determined by moving the optical microscope with an objective lens 1.6 times and an eyepiece 10 times in the fiber width direction. Is counted and converted to the number of free fibrils per 100 denier.

[0060]

Example 1 An autoclave having an inner volume of 550 cm ³ and a pressure resistance of 300 kgf / cm ^{2 was} prepared by adding a melt index (MI) of 0.78 and a density of 0.96 g.
/ Cc of high-density polyethylene (78.6 g), n-pentane (hereinafter abbreviated as PT) 200 g and bromochloromethane (hereinafter BC)
111.3 g) was added, and after the lid was covered, the heater was energized and heated while rotating the stirrer, and PT: BCM = 76.3: 2
A solution was prepared for flash spinning with a polymer concentration of 20.2 wt% consisting of 3.7 (mol%) solvent.

The dissolution is always performed in a liquid-sealed state, and the pressure is 300 k
gf / cm^TwoWhen approaching the vicinity, polymer is dissolved while draining.
The liquid was adjusted. And finally temperature 190 ℃, pressure 151kgf
/cm ^TwoAnd Next, the stirrer was stopped, and 156 kgf
/cm^TwoN_TwoIntroduce gas and pressurize the solution directly with this gas
Quickly open the discharge valve at the bottom of the autoclave
And spun. At this time, the tip of the discharge valve of the autoclave
The decompression orifice, the decompression chamber,
Has a circular through-hole whose center axis coincides with the chisel and nozzle
The spinneret which incorporated the components in this order was attached.
That is, a decompression orifice with an inner diameter of 0.65 mmφ and a length of 5 mm
The introduction angle from the decompression chamber with a diameter of 8 mmφ and a length of 40 mm to the nozzle is
60 ° decompression chamber, inner diameter 0.5mmφ, length 0.5mm
Nozzle, the inner diameter is 3.0mmφ coaxial with the nozzle center axis and the length is
This part has a through hole of 3.0 mm.

The solution was discharged through the spinneret into the atmosphere and spun out. At this time, the pressure in the decompression chamber is 94k
gf / cm ² . Therefore, solution adjustment point is 190 ℃, 151k
gf / cm ² , and the spinning point is 94 kgf / cm ² . The fiber was opened by applying it to a copper plate inclined about 45 ° at a position about 25 mm away from the spinneret. The performance of the obtained fiber was excellent in openability, and the number of free fibrils was 376. Further, the strength is 6.7 g / d, and the spinning speed determined from denier is 240 m / d.
s.

At this time, the pressure corresponding to the solution adjustment point temperature in the cloud point curve was 102 kgf / cm ² . Further, of the solvent used,
The boiling point and TLV calculated from the mole fraction were 43.6, respectively.
° C and 407 ppm. The three-dimensional reticulated fiber thus obtained was of very good quality and was most suitable for a flash spun nonwoven fabric sheet.

[0064]

According to the present invention, it is possible to easily produce a three-dimensional network fiber of polyethylene which is much more excellent in openability and higher in strength compared to the conventionally known flash spinning method which does not destroy the ozone layer. Can greatly contribute to society. By using the flash spinning method of the present invention,
A socially useful reticulated fiber can be easily obtained without destroying the ozone layer surrounding the earth and without adversely affecting the global warming.

In particular, a three-dimensional reticulated fiber of polyolefin having excellent opening properties and excellent strength can be stably obtained. From this three-dimensional reticulated fiber, a nonwoven fabric sheet having high uniformity and consequently great social utility is obtained. An excellent flash spinning method that can be easily manufactured was obtained. In addition, the present inventors have found a flash spinning method which has excellent characteristics of conventional CFCs, that is, low flammability comparable to nonflammability and nontoxicity and low toxicity.
This is a flash spinning method that not only satisfies the protection of the global environment but also is extremely excellent in terms of occupational safety and health.

Furthermore, since the solubility of the polyolefin can be made comparable to that of the conventionally known method, the apparatus manufactured by the conventional method can be used without any special modification. This economic effect is extremely large. Therefore, the social value of the present invention is immense.

[Brief description of the drawings]

FIG. 1 is an example of measurement of a cloud point curve of a polymer solution of the present invention. The symbol “○” in the figure indicates 2-methylbutane / BCM = 76: 2
The cloud point of 4 (molar ratio), the symbol “△” indicates the cloud point of CFC-11 only, and the symbol “▽” indicates the cloud point of the solvent composition of n-pentane / BCM = 76: 24 (molar ratio). . The figure shows a transparent region (one liquid phase) and an opaque region (two liquid phases). The polymer had a melt index of 0.78, a density of 0.96 g / cc and a polymer concentration of the solution of 12.5 wt%.

FIG. 2 is an example of measurement of a cloud point curve of the polymer solution of the present invention. This figure is a measurement example of a change in composition and a change in cloud point in a solvent of n-pentane / BCM. The solid line on the highest pressure side is the cloud point of n-pentane only, and the next dotted line is n-pentane.
The cloud point of pentane / BCM = 91: 9 (molar ratio), the next dashed line is the cloud point of n-pentane / BCM = 83: 17 (molar ratio), and the next broken line is n-pentane / BCM = 76. : 24 (molar ratio), the solid line next shows the cloud point of n-pentane / BCM = 69: 31 (molar ratio). The figure shows a transparent region (one liquid phase) and an opaque region (two liquid phases). The polymer has a melt index of 0.7
8. Density: 0.96g / cc, polymer concentration of solution is 12.5wt%
It is.

FIG. 3 is a schematic view of an optical cell container-based measuring device for measuring the cloud point of a polymer solution.

FIG. 4 is a schematic view of an optical cell container used for cloud point measurement.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Optical cell container 2 ... Optical window 3 ... Motor 4 ... Thermometer 5 ... Pressure gauge 6 ... Valve 7 ... Light source 8 ... Light receiver 9 ... Piping 10 ... Piping 11 ... Plunger type pressure regulator 12 ... Valve 13 ... Stirring Feather 14 ... glass

Claims (2)

(57) [Claims] 1. A high-temperature and high-pressure solution comprising a polyolefin and a solvent containing a halogenated hydrocarbon is prepared, passed through a reduced-pressure orifice, a reduced-pressure chamber, and a spinneret, discharged into a room-temperature and normal-pressure region, and fibrillated polyolefin. In a method for producing a three-dimensional network fiber, a solvent comprising bromochloromethane and a hydrocarbon having 3 to 5 carbon atoms is used as a halogenated hydrocarbon, and the solvent and 5 to 25 wt% of a polyolefin are used. A three-dimensional network of polyolefins, characterized in that the temperature of the solution is adjusted to a pressure exceeding the cloud point curve expressed by the vertical and horizontal axes, respectively, and then the pressure in the decompression chamber is set to a pressure lower than the cloud point pressure. Fiber manufacturing method. 2. A solvent comprising 5 to 45 mol% of bromochloromethane and 3 to 5 carbon atoms in a solvent comprising the bromochloromethane and a hydrocarbon having 3 to 5 carbon atoms. 2. The method for producing a three-dimensional polyolefin network fiber according to claim 1, wherein the hydrocarbon is 95 mol% to 55 mol%.