JP2834315B2 - Method for producing polyethylene three-dimensional reticulated fiber - Google Patents

Description

The present invention relates to a method for producing a three-dimensional polyethylene network fiber using an improved flash spinning method. More specifically, the present invention relates to an improved flash spinning method for obtaining an excellent three-dimensional reticulated fiber using a solvent having a low ozone depleting power.

[Problems to be solved by conventional technology and invention]

The flash spinning method, which is a method for producing a three-dimensional network fiber of polyolefin, is disclosed in US Pat.
It is published by a patent publication such as -50512 and is well known.

As nonwoven fabrics made of fibers produced by the flash spinning method, Tyvek (polyethylene raw material) manufactured by DuPont and Luxer (polyethylene and polypropylene raw materials) manufactured by the present applicant are known.

In the flash spinning method, a fiber-forming crystalline polymer is dissolved in a solvent such as a halogenated hydrocarbon under high temperature and high pressure,
This is a method of changing the pressure and temperature of a solution to form a microphase-separated structure, releasing the solution into a low-temperature and low-pressure region, and forming a three-dimensional net-like fiber.

As the solvent, as described in USP 3,081,519, aromatic hydrocarbons such as benzene and toluene, butane, pentane, hexane, heptane, aliphatic hydrocarbons such as octane, and isomers thereof and Homologs, alicyclic hydrocarbons such as cyclohexane, unsaturated hydrocarbons,
Halogenated hydrocarbons such as methylene chloride, carbon tetrachloride, chloroform, ethyl chloride and methyl chloride, alcohols, esters, ethers, ketones, nitriles, amides,
Many liquids have been disclosed, such as fluorohydrocarbons, sulfur dioxide, carbon disulfide, nitromethane, water, and the various liquid mixtures described above.

As a solvent for polyolefin, a nonflammable solvent is easy to use, and trichlorofluoromethane, 1,1,2
-Trichloro-1,2,2-trifluoroethane and the like are preferred.

However, a specific substance of the totally substituted chlorofluorocarbon, which is obtained by completely replacing hydrogen in these hydrocarbon compounds, is regulated as a substance having a strong power to destroy the ozone layer. Trichlorofluoromethane, 1,1,2-trichloro-
Specific controlled substances such as 1,2,2-trifluoroethane are 2001
It is to be abolished by the year.

Under such a background, a flash spinning method using a mixed solvent containing methylene chloride as a main solvent as a solvent instead of a conventional solvent suitable for flash spinning (Japanese Patent Laid-Open No.
No. 139408) and a flash spinning method using five designated chlorofluorocarbons (JP-A-2-160909) have recently been disclosed.

The problems of the flash spinning method using these solvents are that the spun yarn has a low fiber strength and the shape of the spread yarn is problematic. One of the characteristics of the fibers produced by flash spinning is that the fibers have high strength. In this respect, for example, in the examples in JP-A-2-139408, the strength of the yarns is 1.363 to 2.99 for a polyethylene material. g / d, Examples in JP-A-2-160909 show that the strength is 1.70 to 4.61 g / d, which is not a satisfactory strength. Another problem with the form of the spread yarn obtained by colliding the spinning plate with a rotating plate or the like is that the spread yarn does not separate into fine fibrils and the width of the spread yarn does not increase. Attempts to increase the spreadability will result in fibril breakage and powdery matter.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved flash spinning method for obtaining a high-strength, well-formed three-dimensional reticulated fiber using a solvent having a low destructive power of the ozone layer.

[Means for solving the problem]

An object of the present invention is to prepare a high-temperature and high-pressure solution composed of a solvent containing polyethylene and a halogenated hydrocarbon, pass through a reduced-pressure chamber and a spinneret, and discharge to a low-temperature and low-pressure region to form a three-dimensional network of fibrillated polyethylene. A method for producing a fiber, wherein the halogenated hydrocarbon is 1,1-dichloro-
2,2,3,3,3-pentafluoropropane (HCFC 225ca or simply 225ca) or 1,3-dichloro-1,2,2,3,
3-pentafluoropropane (HCFC 225cb or simply 225
Abbreviated as cb. ) Or a mixture thereof, using 80 to 95% by weight of a mixed solvent of the solvent and a hydrocarbon solvent, polyethylene 20
A homogeneous one-phase solution consisting to 5 wt%, at a temperature above that exceeds the temperature T _alpha starts to rise with increasing the cloud point pressure of the temperature,
And at a pressure above the cloud point pressure, and then, in a decompression chamber, at a temperature from the solvent temperature before introduction of the decompression chamber to 5 ° C. below the temperature, and a pressure below the cloud point pressure. .

The present inventors are a halogenated hydrocarbon having a low ozone depleting power, and a solvent having a very low solubility in polyethylene, but the fiber strength is significantly higher than a known method using a solvent having a low ozone depleting power, A flash spinning method having a good reticulated fiber morphology has been found, and the present invention has been achieved.

225ca and 225cb and their mixtures have very low ozone depletion potentials, estimated at 0.01-0.04.

These solvents are difficult to dissolve polyethylene.For example, high-density polyethylene with MI 0.8 is 500 kg / cm ^{2 at} high temperature.
At pressures below G, no homogeneous solution is formed. The present inventors have found that in order to form a uniform spinning solution and obtain a high-strength spun yarn, it is important to mix a solvent composed of hydrocarbons. Further, the temperature of the solution is set at a temperature not lower than the temperature at which the cloud point pressure starts to increase as the temperature rises and at a temperature higher than the cloud point pressure. It has been found that it is important that the pressure be equal to or lower than the cloud point pressure.

Preferred solvents composed of hydrocarbons include butane, pentane, hexane, carcans such as heptane, cyclopentane, cyclohexane, cycloalkanes such as cycloheptane, cycloalkenes such as cyclohexene, aromatic hydrocarbons such as toluene, methylene chloride, Examples include halogenated hydrocarbons such as ethyl chloride, ethylene chloride, isopropyl chloride, and propylene chloride, and other esters and ethers.

These hydrocarbons have a boiling point of 0 to 100 ° C, preferably 20 to 60 ° C.

The cloud point of the solution, which is an important factor in the present invention, is the second factor.
As shown in the figure, an autoclave 1 having two viewing windows 7 and a stirrer 3 through which a solution can be observed through a light beam.
Observed using. While raising or lowering the temperature of the solution, the pressure of the solution was adjusted to find a point at which visible light was not transmitted, and the cloud point was determined. The pressure at that point is the cloud point pressure.

The cloud point pressure of the solution of the composition of the present invention described above has a point at which the cloud point pressure starts to increase as the temperature increases. The point at which the temperature starts to rise is a specific point of the solution (temperature is T _α , pressure is P _α ). T _α and P _α vary depending on the type and amount of the hydrocarbon solvent to be mixed.

If both are fixed, a constant value is shown. As having a high dissolving power for hydrocarbons, also as the mixing amount is large, the T _alpha to the cold side, the P _alpha moves to the low pressure side.

Polymer and a solvent is heated and when observing the cloud point while the temperature is increased, the cloud point pressure tends to decrease to T _alpha seen. Once heating above T _alpha, if observed while lowering the solution temperature, the cloud point pressure is tend to exhibit a certain value at a temperature lower than T _alpha. Despite these changes, the points T _alpha begins to rise from the cloud point pressure minimum point is found to exhibit a constant value with a solution of constant composition. The unique cloud point pressure T cloud point pressure corresponding to _alpha P _alpha also show a constant value.

The above will be described below with a specific example. Cyclohexane is added to a mixture of 225ca and 225cb of 50wt% each and 20wt% of the total solvent
High-density polyethylene 1 with mixed solvent 87.5wt% and MI 0.78
While increasing the cloud point of the solution consisting of 2.5 wt%,
(Heating rate: about 3.3 ° C / min before starting the measurement, about 1.4 after starting the measurement
° C / min). The result is shown in FIG. The point T _α at which the cloud point pressure began to increase with increasing temperature was observed to be 193 ° C. _P α was 190kg / cm ² G. In this experimental example, the cloud point pressure with increasing temperature at a lower temperature than T _alpha tended to decrease, it takes the minimum value in terms of T _alpha.

As boundary T _alpha in the present invention have found that spinning state, spun yarn properties change. That is, in the above experimental example, T
_Although it is not impossible to adjust the solution and spin at a temperature lower than _α = 193 ° C., the spinning state is not stable, the strength of the spun yarn is low, and the form of the spread yarn is not good. T _α = 193 ° C
The solution is adjusted at a pressure not lower than the temperature of the solution and at a pressure higher than the cloud point pressure at the solution temperature. When the flash spinning is performed at a pressure equal to or lower than the cloud point pressure, a high-strength, well-shaped reticulated fiber can be obtained.

The polyolefin may be a copolymer containing less than 15% by weight of components other than the main component. In addition, additives such as an antioxidant, an ultraviolet absorber, a lubricant, a filler, a nucleating agent, an antistatic agent, and a coloring agent may be added as long as the properties of the polymer are not impaired.

〔Example〕

Example 1 71.3 g of high density polyethylene with MI of 0.78, HCFC225ca and HC
80 wt% of a mixture of 50 wt% each of FC225cb and cyclohexane 20 w
499 g of a solvent composed of t% was charged into an autoclave of 534 cm ³ (polymer concentration: 12.5 wt%), and the autoclave was heated while rotating a propeller-type stirrer to dissolve high-density polyethylene.

The solution was further heated, the pressure of the solution was increased, the entire amount of the polymer was dissolved, and the solution was adjusted. Solution pressure after dissolution is 30
The solution was discharged from the discharge nozzle below the autoclave so as not to exceed 0 kg / cm ² G (design pressure of the autoclave), and the pressure was maintained at 260 to 300 kg / cm ² G. Solution temperature is 205
At the time when the temperature reached ° C., the solution was discharged to 250 kg / cm ² G, the solution temperature was adjusted to 205 ° C., the stirrer was stopped, the H ₂ gas introduction valve at the top of the autoclave was opened, and 265 kg / cm 2
Pressurize ² G, quickly open the release valve at the bottom of the autoclave, and pour the solution into a vacuum orifice (diameter 0.65 mm, length 5 m
m) to a decompression chamber (diameter 8 mm, length 40 mm) and a spinneret (introduction angle from the decompression chamber to the nozzle 60 °, nozzle diameter 0.
5mm, length 0.5mm, 3.0mmφ outside around the nozzle,
It has a circular groove with a depth of 3 mm. ) And released into the atmosphere. The decompression room temperature and pressure were 204 ° C. and 192 kg / cm ² G. The spread yarn is approximately 45 mm at a position about 25 mm away from the spinneret.
゜ I made it on the inclined copper plate.

The obtained fiber is an unspread yarn, with a fineness of 110 d and a tensile strength of 6.
It was a three-dimensional reticulated fiber with good morphology, with 7 g / d, an open fiber fineness of 115 d and a tensile strength of 5.8 g / d. The specific surface area of the unspread yarn is 15
m ² / g.

(Effect of the present invention)

By using the flash spinning method of the present invention, the protection of the ozone layer, that is, the preservation of the global environment is preferable, and the fiber strength is remarkably high by the method using a known countermeasure solvent, and the opened fiber form is excellent. Three-dimensional reticulated fibers can be made.

[Brief description of the drawings]

FIG. 1 shows an example of a cloud point curve of the solution of the present invention, a specific point T _α , and a preferable temperature range of the solution. Figure 2 is a schematic illustration of observation window autoclave used to measure the cloud point for determining the T _alpha. DESCRIPTION OF SYMBOLS 1 ... Autoclave with a viewing window, 2 ... Tightening bolt, 3 ... Stirrer, 4 ... Valve, 5 ... Temperature detection terminal, 6 ... Diaphragm pressure detection terminal, 7 ... Viewing window, 8 ... ... Light source, 9 ... Receiver, 10 ... Intensifier for liquid, 11 ~ 13 ... Bulb.

Claims (1)

(57) [Claims] 1. A three-dimensional reticulated fiber of fibrillated polyethylene is prepared by preparing a high-temperature and high-pressure solution comprising a solvent containing polyethylene and a halogenated hydrocarbon, passing the solution through a vacuum chamber and a spinneret, and releasing the solution into a low-temperature and low-pressure region. In the method for producing 1,1-dichloro-2,2,3,
3,3-pentafluoropropane or 1,3-dichloro-1,
Using 2,2,3,3-pentafluoropropane or a mixture thereof, a mixed solvent of the solvent and a hydrocarbon solvent 80 to 95.
wt% and 20 to 5 wt% of polyethylene at a temperature T at which the cloud point pressure starts to rise as the temperature increases.
Adjust the temperature above _α and above the cloud point pressure, and then adjust the temperature and pressure of the decompression chamber to a temperature from the solvent temperature before introduction of the decompression chamber to 5 ° C. below this temperature and a pressure below the cloud point pressure. A method for producing a three-dimensional polyethylene network fiber, comprising the steps of: