JPS6141318A - Manufacture of multifilament - Google Patents

Abstract

PURPOSE:To obtain the titled multifilament composed of filament units finer than a specific level, and having excellent chemical resistance, heat resistance, etc., by carrying out the melt-spinning and drawing of a polyvinylidene fluoride resin having a specific melt flow index under specific conditions. CONSTITUTION:A polyvinylidene fluoride resin having a melt flow index of 50- 200g/10min, preferably 60-150g/10min at 250 deg.C under 10kg load, is melted and extruded through a nozzle having a diameter of 0.07-0.51mm.<2> at a shear rate of 270-1,800/sec and a resin temperature of 250-290 deg.C, and the extrudate is spun in air at a draft ratio of 20-100. The obtained multifilament is drawn at 100- 160 deg.C to obtain the objective multifilament having a filament fineness of <=30 denier and a linear strength of >=3.0g/denier.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing multifilaments made of polyvinylidene fluoride resin and consisting of single filaments with a diameter of 30 deniers or less, and involves single-stage or multi-stage heating stretching of polyvinylidene fluoride filaments that have been melt-spun. It's something you can get by doing.

Polyvinylidene fluoride resin has a higher melt viscosity than resins such as polyethylene and polypropylene, so it is difficult to obtain fine denier yarn when spinning using conventional melt-spinning equipment due to molding problems such as single fiber breakage. there were. However, by adopting specific spinning and drawing conditions discovered by the present inventors, fine denier is possible. The number can be selected from a wide range of 20 to 100, making stable melt spinning possible.

Here, the polyvinylidene fluoride resin used in the present invention has a melt flow index of 50 or more and 200 at 250°C and 10 kg load.
(g710 minutes) or less is preferable, or 60 or more and 150 (J
/10 minutes) or less. If it is less than 60 minutes (!9710 minutes), high-temperature molding is forced and thermal decomposition is likely to occur, nozzle breakage occurs, and a high draft rate cannot be achieved. 150 (.9/10 minutes) or more, denier unevenness and yarn fluctuation occur within the draft rate range where fine denier is possible. Therefore, the filament strength also decreases. Such polyvinylidene fluoride resin may be a homopolymer or a copolymer with different monomers. If necessary, fillers, additives, etc. may be included, but if they exceed 10% by weight, stable spinning will be hindered by the stagnation in the nozzle. Preferably.

Next, the apparatus, spinning and stretching conditions will be described in detail.

It is obtained by melt extrusion at a draft rate within the above range using a nozzle with a nozzle cross-sectional area of 007 to 0.51 tan" and then stretching. At this time, in order to make a single fine filament of 30 deniers or less, The larger the nozzle diameter is used, the higher the draft or the higher the draw ratio needs to be selected.The appropriate resin temperature during melt extrusion is 250°C to 290°C as measured directly below the nozzle, but preferably 260°C to 280°C. If it is less than 250℃, the extrusion torque will increase, causing skin roughness and melt fracture.On the other hand, if it is more than 290℃, the resin accumulated in the die and nozzle will thermally deteriorate, resulting in filament breakage and low filament strength. It becomes easier to sit up.

In the drawing process, the melt-extruded multifilament may be cooled and rolled up using a winding roll and then subjected to a drawing hot roll in a separate process, or it may be obtained by applying a drawing hot roll machine in a continuous process after melt spinning. .

Polyvinylidene fluoride resin has high crystallinity and high elastic modulus, so it is strong and gives the filament a hard feel. Therefore, lowering the denier of the single yarn through high-magnification stretching is the key to softening the texture of woven fabrics, etc. Therefore, the hot roll temperature is an important factor for stably and uniformly stretching. Generally, stretching is carried out at a temperature slightly higher than the glass transition point. In the case of the multifilament according to the method of the present invention, the denier is 100 to 160, depending on the denier and the drawing speed.
Stretching is possible in the temperature range of °C, but polyvinylidene fluoride resin has a higher melting point than polyethylene, etc.
In order to perform high-stretching stretching, more stable stretching can be achieved by stretching at a higher temperature range of 120°C to 150°C. To make a single filament of 30 denier or less,
Although careful consideration must be given to the relationship between the nozzle diameter, drawing ratio, and filament strength, the drawing, which is normally carried out in one stage, can be divided into two or three stages under the above temperature conditions to increase the stretching by 2 to 6 times. A multifilament with a linear strength of 3.011/denier or more can be obtained.

At present, polyvinylidene fluoride resin is mostly used for spinning and drawing monofilaments, and is currently being developed for use in large diameter fields such as fishing lines. The establishment of fine denier filament molding technology through the present invention has made it possible to advance into the field of fibers and filtration fabrics that take advantage of their high chemical resistance, high heat resistance, and high weather resistance.

Next, the present invention will be explained in more detail with reference to Examples.

250℃, 10 to 9 charged MFR! 1/10 minute polyvinylidene fluoride resin was extruded at a temperature of 27 using a 30-hole nozzle with a nozzle cross-sectional area of 0201+II++2.
0°C, shear rate 990sec-' + draft rate D
The product was melt-extruded and wound up at R=40 and subjected to the next hot roll stretching process. Stretching conditions and JIS-L1070
The results of the physical properties of the multifilament measured in accordance with the above table are shown in Table 1.

Table - Examples Examples After weaving the multifilament obtained in Example 1, a chemical resistance test was conducted. Show the results on the second page.

Table 2 Patent applicant: Showa Denko Co., Ltd. Supplementary manuscript (spontaneous) April 72, 1982

Claims (1)

[Claims] Melt flow index (10kg load at 250℃) is 50-20
0 (g/10 min) of polyvinylidene fluoride resin with a nozzle cross-sectional area of 0.07 mm^2 to 0.51 mm^2 with a shear rate of 270 sec^-^1 to 1800 s.
Resin temperature is 250℃ to 290℃ in the range of ec^-^1
The extrudate is melt-extruded in the air, spun at a draft rate of 20 to 100, and then drawn at a temperature of 100°C to 160°C to produce a single yarn of 30 denier or less and a linear strength of 3.0 g/denier or more. A method for producing polyvinylidene fluoride multifilament.