JPH06116808A - Production of polyolefin three-dimensional fiber - Google Patents

Abstract

PURPOSE:To provide the method for producing the polyolefin net-like fiber excellent in strength and openability and suitable for the production of flush spun nonwoven fabric sheets by using a non-inflammable hydrocarbon halide extremely reduced in the ozone layer-destroying function. CONSTITUTION:The method for producing the fibrillated polyolefin three- dimensional fiber by producing a high temperature high pressure solution comprising a polyolefin and a solvent containing a hydrocarbon halide, passing the solution through a pressure-reducing orifice, a pressure-reducing chamber and a spinneret, and subsequently releasing the solution into an ordinary temperature and ordinary pressure area is characterized in that the solvent is a solvent mixture substantially composed of a 1-3C hydrocarbon halide and 1,1,1- trifluoro-2-chloroethane and that the weight ratio of the solvent mixture/the polyolefin is 5-25%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved production method for obtaining a polyolefin three-dimensional reticulated fiber having excellent strength and openability for a non-woven fabric sheet by using a solvent which is incombustible and has a small ozone depleting ability. It is a thing.

[0002]

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

For example, this spinning method is disclosed in US 30815.
No. 19, US 3,227,794, US 32
No. 27784, U.S. Pat. No. 3,467,744, U.S. Pat. No. 3,564,088, U.S. Pat. No. 3,756,411, European Patent No. 285670A1, Japanese Patent No. 321567A1, Japanese Patent No. 357.
364A2, Japanese Patent Publication No. 40-28125, Japanese Patent Publication No. 42-19520, and Japanese Patent Laid-Open No. 62-33816.
JP-A-63-50512 and the like.

Incidentally, the solvent of the polymer used in the flash spinning method is required to have the following characteristics, which has already been shown in US Pat. No. 30,815,19 and the like. That is, the boiling point of the solvent is at least 25 ° C. lower than the melting point of the polymer used, and the solvent is inert to the polymer under spinning conditions,
Under suitable temperature and pressure to prepare polymer solution,
Being a good solvent for the polymer, below the boiling point of the solvent,
A solvent that dissolves the polymer in less than 1%,
It is a solvent that can form a phase composed of almost a polymer by immediately performing phase separation during spinning, and a solvent that hardly remains in the separated polymer phase.

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

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

However, in recent years, it has been discovered that all halogenated hydrocarbons in which all hydrogen is replaced by chlorine and fluorine have extremely high ozone depletion ability as specific CFCs (also referred to as chlorofluorocarbons or CFCs),
From the standpoint of protecting the earth, production was banned by 1996 AD. Naturally, the specific fluorocarbons trichlorofluoromethane, 1,1,2-trichloro-1,2,2-
The production of trifluoroethane etc. is also prohibited and cannot be obtained. Therefore, trichlorofluoromethane cannot be used as a solvent for the flash spinning method of polyolefin.

From such a background, a flash spinning method using a new solvent without using trichlorofluoromethane which is a specific flon has already been proposed. In particular, the development of solvents using methylene chloride is being actively conducted. For example, U.S. Pat. No. 5,032,326, European Patent Publication No. 0357381A2, Japanese Patent Laid-Open No. 2-13.
9408 discloses methylene chloride and alternative freons such as chlorodifluoromethane, 1,1,1,2-tetrafluoroethane, 1,1-difluoroethane, 1,1,1,2.
-Tetrafluoro-2-chloroethane, 1-chloro-1,
A flash spinning method using a mixed solvent with 1-difluoroethane or the like is disclosed. Also, US 5081177
In the specification and the like, there is proposed a method of spinning using an alternative CFC such as 1,1-dichloro-1,1,1-trifluoroethane.

However, all of these already proposed flash-spinning methods have drawbacks when spinning with polyolefins. One of the characteristics of fibers produced by flash spinning is their high strength. However, for example, in the mixed solvent of methylene chloride and alternative CFCs proposed in US Pat. No. 5,033,326, the strength of spun yarn is as low as 3.55 g / d at the highest. Further, since gas is used as the cosolvent, there is a problem that the spinning equipment and the cosolvent recovery process are complicated.

Further, in the proposal using alternative CFCs such as US Pat. No. 5,081,177, the strength of the spun yarn is similarly low at a maximum of 4.61 g / d. In addition, Japanese Patent Laid-Open No. 4-1
85708 discloses 1,1-dichloro-2,2.
3,3,3-pentafluoropropane or / and 1,
A method using 3-dichloro-1,2,2,3,3-pentafluoropropane and a hydrocarbon solvent is disclosed.

However, 1,1-dichloro-2,2
3,3,3-pentafluoropropane or / and 1,
Depending on the mixing ratio of 3-dichloro-1,2,2,3,3-pentafluoropropane and the hydrocarbon solvent, there are problems that the polyolefin is not completely dissolved and the spun yarn strength is low. , The mixing ratio is not examined at all. Further, in the examples, cyclohexane is used as the hydrocarbon solvent, but since cyclohexane has high combustibility, it can be presumed that a fire accident will occur at the time of recovery or abnormality.

[0012]

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

[0013]

In order to achieve the above-mentioned object, the present inventors have conducted a great deal of research on solvent screening, and found out how to compare fibers with polyolefin three-dimensional fibers by conventional flash spinning methods. It was possible to reach the present invention as a result of trial and error as to whether or not a fiber having excellent performance could be obtained.

That is, according to the present invention, a high temperature and high pressure solution comprising a solvent containing a polyolefin and a halogenated hydrocarbon is prepared and passed through a pressure reducing orifice, a pressure reducing chamber and a spinneret,
In the method for producing a reticulated fiber of fibrillated polyolefin by releasing into a room temperature and normal pressure region, the solvent is substantially composed of halogenated hydrocarbon having 1 to 3 carbon atoms and 1,1,1-trifluoro-2-chloroethane. The mixed solvent and the polyolefin have a weight ratio of 5 to 5
The present invention provides a method for producing a polyolefin three-dimensional fiber characterized by being 25%.

According to this method, the inventors of the present invention have three-dimensional fibers of a polyolefin having a markedly high strength and good openability, which is different from the conventionally known improvement method, even though it is a solvent having a small ozone depletion ability. I was able to get The properties that should be possessed as a flash spinning solvent are as follows in detail. At normal temperature and pressure, the polymer does not dissolve at all, but at temperatures above the melting point of the polymer and at high pressures far above atmospheric pressure, the polymer is dissolved.

A phase change from a transparent liquid to an opaque liquid at a temperature exceeding the melting point of the polymer and causing no thermal deterioration, particularly in the case of flash spinning, LCST (Lower Critical So), which is referred to as polymer solution theory.
lotion Temperature. It is preferable that the polymer solution has a lower critical solution temperature phase diagram, and the flash spinning solvent also has an LCST phase diagram. Moreover, it is preferable to have an LCST type phase diagram, and moreover, the phase change should occur instantaneously. This property is important because flash spinning causes a phase change from transparent to opaque under pressure.

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

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

Since the entire flash spinning device is a high-pressure device, it is necessary to use a solvent having low corrosiveness. ODP must be small. Preferably, 0.
It is preferably less than 01. Of particular importance are low boiling point, LCST type polymer solutions,
It has low flammability and low ODP.

To date, a large number of polyolefin flash-spinning solvents are known. However, other than trichlorofluoromethane, those satisfying the above four conditions have not been proposed. We have at least a low boiling point, L
An extremely large number of experiments were conducted in order to find a flash spinning solvent satisfying the four conditions of CST type polymer solution, low flammability and low ODP.

As a result, the flash spinning solvent has 1 carbon atoms.
It has been found that a mixed solvent consisting essentially of halogenated hydrocarbons up to ~ 3 and 1,1,1-trifluoro-2-chloroethane fulfills the above four conditions completely or almost completely. 1,1,1-Trifluoro-2-chloroethane has a low boiling point of 6.9 ° C., has a small heat of vaporization, is nonflammable, and has a small ozone depleting ability, and is therefore useful as a flash spinning solvent. Further, among the above-mentioned conditions, the most important condition is the LCST type polymer solution, and the setting of an appropriate cloud point pressure.

When the polyolefin is dissolved in the mixed solvent used in the present invention, an LCST type polymer solution is obtained. As described above, the basic principle of flash spinning is that the polymer solution at high temperature and high pressure is decompressed to be phase-separated into an opaque liquid composed of at least two phases of the polymer and the solvent, and then spun. Therefore, the cloud point temperature and pressure that can be determined by changing from a transparent liquid to an opaque liquid are extremely important. This cloud point is also the point at which phase separation occurs. The cloud point is
It is indicated by the temperature and pressure at the point where the liquid changes from transparent to opaque.

As a result of detailed examination of flash spinning suitability,
The cloud point pressure is approximately 1 at around 200 ° C. when high density polyethylene is used (polymer concentration is 10 to 15% by weight).
It has been found that a fiber having excellent strength and openability can be obtained in the range of 00 to 200 kg / cm ³ . Preferred 1,1,1-trifluoro-2-in the mixed solvent of the present invention
Considering the applied cloud point pressure, the proportion of chloroethane in the mixed solvent is generally 30 to 80% by weight.
Met. When the proportion of 1,1,1-trifluoro-2-chloroethane is higher than 80% by weight, the solubility of the mixed solvent in polyolefin becomes low, so that part of the polyolefin is not dissolved or completely dissolved. However, there is a problem in that the time required for the extension becomes long. These problems are directly related to the strength of the spun yarn, the openability,
It adversely affects solvent deterioration. When the proportion of 1,1,1-trifluoro-2-chloroethane is lower than 30% by weight, the solubility of the polyolefin is improved, but the cloud point pressure is too low, resulting in a low discharge pressure. A phenomenon occurs in which the spun yarn is not drawn and the strength decreases. Particularly preferably, it is 50 to 70% by weight.

The halogenated hydrocarbon having 1 to 3 carbon atoms in the present invention is not a so-called specific CFC or alternative CFC. As a halogen atom, 1 of chlorine, bromine and iodine
It may contain one or more species or more, and in some cases some of the hydrogen atoms may be replaced by functional groups such as esters, ethers, hydroxyl groups and the like. To exemplify such a halogenated hydrocarbon having 1 to 3 carbon atoms, methyl chloride, ethyl chloride, 1-butyl chloride, 2
-Butyl chloride, methylene chloride, chloroform, 1,1-
Dichloroethane, 1,2-dichloroethane, 1,1,2
-Trichloroethane, dichloroethylene, trichlene,
Perclane, 1,2-dichloropropane, 1,3-dichloropropane, methyl bromide, ethyl bromide, 1-butyl bromide, 2-butyl bromide, bromochloromethane, dibromomethane, bromochloroethane, methyl iodide, Ethyl iodide, 1-iodinated propane, 2-iodinated propane and the like can be mentioned. Among these halogenated hydrocarbons, preferable ones are 1,2-, because they satisfy the above 5 conditions at a high level.
It is dichloroethylene, bromochloromethane, 1,2-dichloropropane, 1,1-dichloroethane, methylene chloride, trichlene, perclen, particularly 1,2-dichloroethylene and bromochloromethane, methylene chloride and trichlene. These halogenated hydrocarbons having 1 to 3 carbon atoms may be mixed alone or in combination, if necessary.

The halogenated hydrocarbon having 1 to 3 carbon atoms and 1,1,1-trifluoro-2-chloroethane used in the present invention are preferably substantially pure products. In particular, free acids such as hydrogen chloride, hydrogen bromide and water are preferably as small as possible, particularly preferably 10 ppm.
It is the following. Further, for halogenated hydrocarbons having low thermal stability, it is recommended to use a stabilizer or the like, if necessary. As the heat stabilizer, 1,2-butylene oxide, propylene oxide, 1,4-dioxane, dibutyltin malate, dibutyltin laurylate, phosphite derivative, methanol, ethanol, pyridine, butylamine, methyl acetate, ethyl acetate, catechol, One or more of phenol derivatives, etc.
About 4% can be used.

The three-dimensional reticulated fiber spun by using the solvent of the present invention determined as described above has high strength and excellent openability, and can be formed into a good nonwoven fabric sheet. . Each of the solvents used in the present invention exhibits relatively high thermal stability under flash spinning conditions, but in order to maximize thermal stability, the acid content and water content contained in the solvent should be as low as possible. It is preferable to reduce the amount. The concentration of such impurities is generally 50 ppm or less, preferably 20 ppm, more preferably 10 ppm or less.

The proportion of polyolefin in the polyolefin solution of the present invention is 5 to 25% by weight. Within this range, it is possible to easily produce a polyolefin three-dimensional fiber having excellent fiber-opening property and high strength. If it is 5% by weight or less, the pulp-like or low-strength yarn is obtained, and if it is 25% by weight or more, the yarn openability is low, which is not preferable in any case. More preferably, it is 10 to 20% by weight.

As the polyolefin, polyethylene,
Examples include polypropylene and polymethylpentene-1. The polyethylene is most preferably high-density polyethylene, and the density is 0.94 g / cm ³ or more. Further, it is preferable that the copolymerization component is not more than about 15% by weight and maintains the above density. The polypropylene preferably contains about 85% by weight or more of isotactic polypropylene, and may contain about 15% by weight or less of other polypropylene or a copolymerization component such as ethylene or butene. Further, a polymer additive which is generally known, a light stabilizer, a lubricant, a nucleating agent, a crosslinking agent, a plasticizer, a filler and the like may be contained in the polymer.

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

[0030]

The contents of the present invention will be described with reference to the following examples. This example is for specifically explaining the content of the present invention, and does not limit the scope of the claims of the present invention. In the examples below, 1,1,1-trifluoro-2-chloroethane is abbreviated as HCFC-133a.

[0031]

Example 1 81.7 g of high-density polyethylene having a melt index of 0.78, bromochloromethane / HCFC
481 g of a mixed solvent of -133a (60/40% by weight) was charged into the autoclave (polymer concentration: 14.5% by weight), and the autoclave was heated while rotating the propeller stirrer to dissolve the high density polyethylene. The solution was further heated and the solution pressure was increased to completely dissolve the polymer. After dissolution, the solution pressure is not to exceed 300 kg / cm ^2, keeping the solution was drained pressure from the discharge nozzle of the autoclave lower part 200~300kg / cm ^2. When the temperature of the solution reaches 200 ° C., the solution is discharged, and the pressure applied during spinning is 10 kg rather than 150 kg / cm ^2.
/ Cm ^{2 After} lowering the pressure, keep the solution temperature at the specified 200 ° C.
The nitrogen gas introduction valve in the upper part of the autoclave was opened, a pressure of 150 kg / cm ² was applied, and the discharge valve in the lower part of the autoclave was quickly opened. Next, the solution was passed through a decompression orifice (diameter 0.65 mm, length 5 mm) and led to a decompression chamber (diameter 8 mm, length 40 mm), and the spinneret (introduction angle from the decompression chamber to the nozzle 60 °, nozzle diameter 0.5 mm, a length of 0.5 mm, and a circular groove having a diameter of 3.3 mm and a depth of 3 mm around the nozzle as a center) was passed through and discharged into the atmosphere. The spread yarn was made by applying it to a vinyl chloride plate inclined at about 45 ° at a position about 20 to 40 mm away from the spinneret. The opened yarn in the opened state was received by a wire mesh of 10 mesh and collected.

The obtained fiber is an unopened yarn and has a fineness of 64d.
Tensile strength 6.5 g / d, tensile elongation 37%, specific surface area 35 m ² / g, fineness 65 d with open yarn, tensile strength 6.5 g / d, tensile elongation 36%, fiber width 3.5-6
It was a reticulated fiber having a good shape in cm.

[0033]

[Comparative Example 1] As the solvent, trichlorofluoromethane was used,
Example 1 was repeated at a polymer concentration of 12.5% by weight. The obtained fiber is an unopened yarn with a fineness of 99d, a tensile strength of 5.4g / d, a tensile elongation of 27%, and a specific surface area of 2
It was 1.2 m ² / g.

[0034]

Example 2 Reticulated fibers were produced using the spinning apparatus of Example 1 while changing only the solvent composition and fixing the polymer and polymer concentration of Example 1. When the weight% of bromochloromethane / HCFC-133a was 35/65, the strength was 6.1 g / d, and at 50/50, the reticulated fiber was 6.0 g / d. All of these reticulated fibers showed good openability.

[0035]

Example 3 Solvent composition was changed to methylene chloride / HCFC-13.
Using 3a (60/40% by weight), the reticulated fiber was produced using the spinning apparatus of Example 1 while fixing the polymer and polymer concentration of Example 1. A fiber having high strength of 6.6 g / d and a specific surface area of 33.1 m ² / g and having a high openability was obtained.

[0036]

Example 4 Using the solvent composition trans-1,2-dichloroethylene / HCFC-133a (60/40 wt%), the polymer of Example 1 and the polymer concentration were fixed, and the spinning apparatus of Example 1 was used. A reticulated fiber was produced.
A highly open fiber having a strength of 6.3 g / d and a specific surface area of 35.1 m ² / g was obtained.

[0037]

EFFECTS OF THE INVENTION By using the present invention, a three-dimensional reticulated fiber which is socially useful and has the strength and opening property equivalent to or higher than the case of using trichlorofluoromethane without depleting the ozone layer. Is obtained. When the present invention is utilized, the three-dimensional reticulated fiber of polyolefin, which is much more excellent in openability than the conventional flash spinning method using a solvent capable of substituting trichlorofluoromethane and has high strength, is always stable. The productivity can be maintained and the product can be easily manufactured. This industrial significance is of great value.

Claims (1)

[Claims] 1. A high-temperature and high-pressure solution comprising a solvent containing a polyolefin and a halogenated hydrocarbon is prepared, passed through a pressure-reducing orifice, a pressure-reducing chamber, and a spinneret, and discharged into a room temperature and normal pressure range to obtain a fibrillated polyolefin. In the method for producing reticulated fibers, the solvent is a mixed solvent substantially composed of a halogenated hydrocarbon having 1 to 3 carbon atoms and 1,1,1-trifluoro-2-chloroethane, and the mixed solvent A method for producing a three-dimensional polyolefin fiber, characterized in that the weight ratio of the polyolefin is 5 to 25%.