JPH01280009A - Production of netty fiber - Google Patents

Abstract

PURPOSE:To obtain a fibrillated three-dimensional netty polypropylene fiber outstanding in opening nature and mechanical strength by spinning, through flash spinning process, a high-pressure homogeneous solution comprising isotactic polypropylene, trichlorofluoromethane and CO2. CONSTITUTION:The objective fiber can be obtained by spinning, through flash spinning process, a high-pressure homogeneous solution comprising, preferably. (A) 7-17wt.% of isotactic polypropylene, (B) 63-92wt.% of trichlorofluoromethane, and (C) 0.3-20wt.% of carbon dioxide.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing highly fibrillated polypropylene fibers. More specifically, the present invention relates to a method for producing three-dimensional reticulated polypropylene fibers with excellent openability and strength.

[Conventional technology]

M-fibers produced by flash spinning are known as three-dimensional fibrillated fibers.

Flash spinning is a method in which a homogeneous solution of a fiber-forming polymer and a solvent is instantaneously pressed into a low pressure region through a spinneret having one or more holes at a temperature above the boiling point of the solvent and a pressure above the vapor pressure. This is the way to get it out. The characteristics of the I miscellaneous are t
lsP3.081.519 Publication and Special Publication 1977-28
It is disclosed in Publication No. 125.

That is, the three-dimensional reticular fiber disclosed in USP 3.081.519 is an organic synthetic crystalline polymer fiber having a surface area of 2 m'/g or more and having a structure in which fibrils are spread in a three-dimensional network. . The fibrils are characterized in that they have an average thickness of 4 μm or less, have an oriented structure, and have an average orientation angle of 90° or less as determined by electron beam diffraction.

Furthermore, X-ray diffraction of the fibers: the average orientation angle is smaller than 55°, the number of free fibrils is 50/1000 d
/ 0.1 m+n or more or 25 pieces / 1000
It is characterized by being d/0.1 mm or more.

This three-dimensional reticular fiber has an irregular cross section, a large specific surface area, excellent light scattering properties, high bulkiness, and high strength. Therefore, by taking advantage of the morphology and performance characteristics of this fiber, it is possible to create a high-strength nonwoven fabric with high covering properties. As an example, a non-woven fabric made from straight polyethylene fibers under the trade name "TyvekO" (manufactured by E.I., DuPont, Nimo Earth, Endo, and Company) is commercially available.

Next, a conventional method for producing three-dimensional reticular fibers of PP will be explained.

Trichlorofluoromethane (hereinafter abbreviated as Freon-11).

) is used as a solvent for flash spinning, which is USP.
Publication No. 3.564.088, USP 3.756.441
No. 49-42917 corresponding thereto, and Japanese Patent Application Laid-Open No. 62-33816 filed by the present applicant.

In the process of obtaining an integrated fibrous agglomerated web using a spinneret with multiple spinning holes as disclosed in USP 3.564.088, reticular fibers of isotactic polypropylene (hereinafter referred to as 1-pp) are used. To obtain this, a manufacturing method consisting of the following steps is used.

■ 1.1°2 with a critical temperature between 190 and 220°C
-Trichloro-1,2-2-trifluoromethane (hereinafter abbreviated as Freon-113), Freon-11, and a mixture thereof.
A homogeneous single solution of 4 to 20% of 1-pp with an MFR between 0.9 and 10 is prepared, and the amount of solvent in the solution is above the critical temperature of the component with a low boiling point and the liquid phase boundary pressure is above 2. create pressure.

■ Reduce the solution pressure to 10 to 4 oops under the two-liquid phase boundary pressure.
Pass the solution through the vacuum area to reduce the pressure to i.

■ Discharging the solution through a spinneret orifice at substantially atmospheric pressure and ambient temperature to obtain continuous, highly fibrillated fibers.

The method disclosed in Japanese Patent Application Laid-Open No. 49-42917 involves heating 2 to 20% by weight of 1-pp in a solvent to a pressure equal to or higher than the vapor pressure to form a solution, and then heating this solution at a lower temperature. A method for producing 1-pp filamentary material by extrusion into a low-pressure region, and the temperature used is 2
00-240℃, pressure 63.3kg/cr1
The above is the melting rate of i-pp immediately before extrusion (
MFR) is the relational expression [in the above formula, C is the concentration in weight percent of PP, and T is ℃
The method disclosed in Japanese Patent Application Laid-Open No. 62-33816, which satisfies the indicated solution temperature] and has a VFR in the range of 2 to 30, is
-pp warm solution, spinning temperature below the critical temperature of the solvent (less than 198°C when the solvent is Freon-11), 0.75 to 1
．． This method performs flash spinning by passing through a final nozzle having a nozzle diameter of 5 mm, and is characterized in that the MFR of the polymer immediately before extrusion is 15 or less.

As an example of introducing carbon dioxide into a system consisting of a polymer and a solvent used for flash spinning, USP 3.081.5
An example is disclosed in Publication No. 19.

In this example, a methylene chloride solution of linear polyethylene is saturated with carbon dioxide gas at 200° C. and 1000 psi, and flash spinning is performed by pressurizing the solution with N2 to 1060 psi. As a result, the strength was 3.9 g/d, the elongation was 78%, the specific surface @ 8.5 m'/g, the SX-ray orientation angle was 24°, the electron beam diffraction angle was 30°, the thickness was 2μ or less, the fibril width was 1 to 25μ, and the fineness was 1120 d. of fibers have been obtained.

[Problem to be solved by the invention]

Polypropylene (hereinafter abbreviated as PP), which has a melting point 25 to 35 degrees Celsius higher, may be used as a material that meets the claim of having higher heat resistance than linear polyethylene, but known three-dimensional reticular fibers made of PP may be used. The problem with this is that it has low spreadability and strength.

Therefore, it has not been possible to satisfactorily produce a nonwoven fabric made by laminating spread fibers. Even if it were possible, a nonwoven fabric with excellent dispersibility of HaNl2 could not be obtained.

Opening here refers to the separation of fibers spun from a single spinneret nozzle into smaller units, for example, into individual fibers (referred to as fibrils) constituting a network structure. Further, the term "spreadability" refers to the property of opening the collar. The spreadability is
These properties are necessary for producing nonwoven fabrics, which is an important use of three-dimensional network fibers.

Collar openability can be evaluated by the number of free fibrils and fiber width. The number of free fibrils is a measure of the degree of separation of fibers into finer units, and is expressed as the number of separated fibers per unit amount of fiber.

The fiber width is the spread in the direction perpendicular to the fiber axis until the fiber is spun from a single spinneret and spread two-dimensionally in the direction perpendicular to the fiber axis. Since the fiber width is proportional to the amount of fiber, it is expressed as the spread of fiber per unit amount of fiber, for example, 2
Display as 0 u/200d.

In particular, unless the number of free fibrils is small, the fibrils are clumped together, tears occur in the fiber axis direction, and as a result, there are holes in the spread yarn, the spreadability is determined by the approximate fiber width. It is possible to judge the

When spinning with a spinneret with a single nozzle, one with a circular groove on the outside or one without a groove, especially when the number of free fibrils is not small and the fibers do not tear or have holes. The fiber width is about 150 d of fineness, and the maximum is 1
Up to about 5 pieces. When making a nonwoven fabric by laminating fibers with such small fiber widths, it becomes difficult to fill the spaces between the fibers. To fill this space, only thick nonwoven fabrics with a high fiber content can be created. Further, such a nonwoven fabric has poor uniformity in basis weight and appearance. In order to obtain a nonwoven fabric with a thin basis weight and high uniformity, it is important that the fiber width is 20 mm or more, regardless of the fiber amount.

Next, problems in the conventional method for manufacturing PP three-dimensional reticular fibers will be explained.

The method disclosed in USP 3.564.088 is not satisfactory in the strength and spreadability of the spun yarn, especially in the spreadability.

When the collar is opened by collision as in the method disclosed in JP-A-49-42917, the fibers may be torn in the fiber axis direction, holes may be formed in the spread yarn, and in extreme cases, the fibers may be torn in the direction of the fiber axis. may break, and the strength of the spread yarn due to collision becomes unsatisfactorily low. Furthermore, since a relatively high solution temperature is used, the fibers tend to be colored easily.

In the method disclosed in JP-A-62-33816, since the solution temperature is lower than the critical temperature of the solvent, the flashing force is low, and the opening property is affected by the impact force on the dispersion plate. was inferior.

In view of the above problems, an object of the present invention is to provide a method for producing a three-dimensional reticular polypropylene fiber having excellent openability and strength.

[Means to solve the problem]

An object of the present invention is to provide a method for producing three-dimensional network fibers of fibrillated polypropylene by a flash spinning method, which is characterized by using a high-pressure homogeneous solution consisting of isotactic polypropylene, trichlorofluoromethane, and carbon dioxide gas. This is achieved by the method of

Preferably isotactic polypropylene 7-17
wt%, trichlorofluoromethane 63-92 wt%,
This is achieved by a method characterized by using a homogeneous solution consisting of 0.3 to 2 Qwt% carbon dioxide.

In a method for producing polypropylene three-dimensional network fibers by a flash spinning method, the present inventors have discovered that by adding carbon dioxide gas to a well-known system of 1-pp and Freon-11, the collar openability and strength of the spun yarn can be improved. The present invention was achieved based on the findings that the present invention can be improved, that spinning can be carried out stably over a wide temperature range, and that the decrease in the molecular weight of the polymer is small.

In particular, since it can be spun at a low temperature and with a high flash force, when the spun yarn collides with the dispersion plate to spread the fibers, there is no close contact between the fibrils, the fibers are highly spread, and the fibers are highly oriented. Furthermore, since spinning can be carried out at a high pressure to the pressure of the vacuum chamber set in front of the spinneret, the flushing power of the solution from the spinneret is high, improving the opening property and strength.

The concentration of 1-pp is preferably 7 to 17 wt%.

If it is less than 7 wt%, it will be difficult to ensure the strength of the spun yarn. If the concentration exceeds 17 wt%, it becomes difficult to provide suitable opening properties for nonwoven fabrics.

It is preferable to use a polymer having a λIFR of 20 or less.

If it exceeds 20, it becomes difficult to develop strength, which is not preferable.

The 1-pp used contains about 35 wt% or more of 1-pp, and less than about 15 wt% contains ppl other than 1-pp, or ethylene, n-butylene, imbutylene, acetic acid vinylopemethacrylic acid. It may also contain polymer components such as methyl. Further, additives such as antioxidants, ultraviolet absorbers, lubricants, fillers, nucleating agents, antistatic agents, colorants, etc. may be added to the extent that the properties of 1-pp are not impaired.

The amount of Freon-11 constituting the flash spinning solution is 63
It is preferable to set it as 92 wt%. If it is less than 63%, the spreadability will decrease. If it exceeds 92 wt%, the strength of the spun yarn will decrease.

The amount of carbon dioxide gas added is preferably Q, 3wt% to 2Qwt%. If it is less than 3.3 wt%, it is difficult to achieve high strength and high fiber opening effects. If it exceeds 20%, the solubility of the polymer decreases, which is not preferable. In addition, F gasified after discharging the solution
If the amount of carbon dioxide gas is too large to liquefy and recover -11, it will be difficult to recover it, so it is preferable to reduce the amount within a range that satisfies the spreadability and strength of the spun yarn. Even at about 1Qwt%, the opening property and strength are sufficiently satisfied. It is preferable to use liquefied carbon dioxide because it is easy to measure the amount of carbon dioxide introduced and to prepare a homogeneous solution.

Polymer solutions and solution extrusion can be carried out not only by a batch method using an autoclave or the like, but also by a continuous method using a screw extruder or the like.

〔Example〕

The present invention will be explained in detail with reference to Examples below. However, the present invention is not limited to the examples.

Examples 1 and 2 Comparative Example 1.2 A schematic diagram of an example of a spinning apparatus for carrying out the method of the present invention is shown in FIG.

61 g of 1-pp (Chisso Polypro 1011 sold by Chisso) with an MFR of 0.7, 584 g of fluorocarbons, and 56 g of liquid carbon dioxide were charged into autoclave 1 with an internal volume of 534 crl (polymer concentration 9 wt%, F-11133 wt).
%, carbon dioxide amount 3wt%) heating the autoclave while rotating the propeller type stirrer 2 to dissolve 1-pp.
A homogeneous solution was obtained.

Carbon dioxide gas was introduced using an ultra-high pressure metering pump (manufactured by Milton Roy).

The solution temperature was detected with a thermocouple thermometer 3 inserted into the autoclave. The solution pressure was similarly detected with a diaphragm pressure detection terminal 4 inserted into the autoclave.

The solution pressure is 260 to 300 kg/cII with heating.
1G, but at this point the polymer has dissolved and remains, and while the composition of the solution remains unchanged, operate the valve 7 to release the polymer at the bottom and reduce the solution pressure to this pressure while discharging the solution. (autoclave pressure 300
kg/c++! G) Heating was continued until the predetermined temperature was reached after a heating time of 54 minutes. (For batches that finished heating up a little earlier,
A slight opening was maintained at the specified temperature. ) At this point, the amount of solution is further reduced and the pressure is lowered to about 3 to 5 kg/c [I
After lowering the pressure to 1G, bring the solution to the specified temperature again, stop the stirrer, open valve 6 at the top of the autoclave, pressurize at the specified pressure by introducing N2 gas, and quickly close the release valve 7 at the bottom of the autoclave. The solution is introduced into the vacuum chamber 9 (diameter 8 mm, length 60 mm) through the vacuum orifice 8 (diameter 0.6 mmφ, length 5), and then the spinneret nozzle 10 (introduced from the vacuum chamber to the nozzle hole). Angle 60°, nozzle hole diameter 0.5 mmφ, length 0.5 mm
.

3.0 mmφ and 3.0 mm deep outward from the nozzle hole.
(with a circular groove of 0 mm) and was discharged into the atmosphere.

During the discharge, about 4.5 m at a distance of about 20 m from the spinneret.
The discharged fibers were applied to a copper plate tilted at 5° and opened. The spread yarn was received by a coarse e-net (approximately 5 meshes), and the fiber width was measured.

Table 1 shows the main spinning conditions and fiber properties.

It can be seen that in the examples in which carbon dioxide gas was added, the strength of the spun yarn was high and the fiber opening properties were excellent. It can also be seen that the weight average molecular weight is higher in Examples.

Blank space below Example 3 Flash spinning was carried out in an autoclave under the same conditions as in Example 1, except that the pressure reducing orifice was 0.5 mmφ x 5 holes β and the solution temperature was 190°C.

Solution pressure is 122kg/cnfG Decompression chamber pressure is 59kg/crlG Met.

As a result, the strength was 4.2 g/d, the elongation was 52%, and the fineness was 49 d.
Fibers with good morphology were obtained.

The fineness was measured by applying a load of 0.6 g per 1 d.

Particularly in the case of a 1-pp spread yarn, it has high elasticity, and under tension at a low load, the fibrils are measured in a bent state.

The tensile strength and elongation of the fibers were measured using an Instron type tensile tester (manufactured by Shimabara Seisakusho) at a tensile speed of 200 mm/min using a sample twisted at 8 twists/cm. The load during twisting was the same as that used for fineness measurement.

The weight average molecular weight of decalin is 0.3 g/100
c++ was determined by using a solution, measuring the viscosity of the solution at 135°C, and calculating from the relational expression.

〔Effect of the invention〕

The method for producing reticular fibers according to the present invention can be performed in a wide temperature range.
Stable flash spinning is possible. In particular, spinning is possible at low temperatures (for example, 190° C.), and the spun yarn has high strength without fibril adhesion. In addition, since high pressure conditions can be used in the decompression chamber, a spread weft suitable for nonwoven fabrics having excellent spreadability and strength can be obtained. Since the decrease in the molecular weight of the polymer is small, the molecular weight of the polymer used as a raw material can be lowered, and the solubility of the polymer can be improved during solution preparation, allowing stable spinning.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment of an apparatus for carrying out the method for producing reticular fibers of the present invention. 1... Autoclave, 2... Stirrer, 3.
...Thermocouple temperature detection section, 4.Diaphragm pressure gauge detection section, 5.Air degassing valve, 6.Introduction of solvent, carbon dioxide gas and pressurized nitrogen 7 Nll
Dub 7...polymer solution release valve, butt...orifice for depressurization, 9...decompression chamber, 10...
...Spinning nozzle nope 11...Bolts with tightening,
12... Autoclave lid part, 13... Autoclave main body part, 14... Diaphragm type pressure gauge detection part.

Claims (1)

[Claims] 1. In a method for producing a three-dimensional network fiber of fibrillated polypropylene by a flash spinning method,
A method for producing a reticular fiber, which comprises spinning using a high-pressure homogeneous solution consisting of isotactic polypropylene, trichlorofluoromethane, and carbon dioxide gas.