JPS63145465A - Polyvinyl alcohol fine fiber sheet like article and its production - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a dense and uniform thin film-like sheet made of polyvinyl alcohol-based filament fibers spun using high voltage, and a method for producing the same.

(Prior art) There are various ways to obtain AM fibers, such as high-speed spinning and composite spinning, but to obtain them in sheet form, there is a method of blowing them with strong hot air like a melt-prone. It is used in However, although the average diameter of the fibers is around 1 micron (Jl), there is a large variation in the diameter, and it also depends on the airflow, so in order to obtain a thin film sheet, the density of the fibers is uneven. A uniform thin sheet was not obtained.

Although there is a strong need in the filter and medical fields for uniform and dense planar sheets made of ultra-fine microfibers of 1μ or less, homogeneous sheets with a diameter of 1μ or less and fine openings of 1μ2 or less are needed. No sheet-like material has been obtained, and this demand has not been met.

On the other hand, a method for obtaining fine fibers using high voltage was published in
No. 8-1466 discloses that the polymer is acrylonitrile, but the conditions for controlling the fiber diameter, the uniformity of the fibers, and the uniformity among the fibers in the resulting sheet are not disclosed. Not yet.

(Problems to be solved by the invention) A thin film-like sheet that prevents bacterial permeation and captures high molecular weight substances such as antigens and antibodies requires a uniform structure with fiber diameters of 1 μm or less and openings of 1 μm or less. However, in the prior art, it was not possible to obtain a fibrous structure that matched this number ζ.

The present invention aims to obtain a fibrous structure as described above.

(Means for Solving the Problems) As a result of intensive studies using polyvinyl alcohol (PVA), the present inventors found that the fiber diameter, the uniformity of the fibers, and the uniformity among the fibers in the obtained sheet were It was discovered that the results were extremely dependent on the concentration of the spinning stock solution. Moreover, its concentration depends on the polymerization degree of the polymer, and in order to obtain the fibrous structure as described above, which is the object of the present invention, the concentration of the polyvinyl alcohol spinning solution must be adjusted within a predetermined range depending on the polymerization degree. I realized that I needed to. That is, PVA as a polymer
Alternatively, use modified PVA, use water and/or water with an organic solvent, alkali, or acid added as a solvent, dissolve PVA or modified PVA in this, and uniformly dissolve the granular gel without any particulate gel. The spinning stock solution is prepared while being kept at a warm temperature. When discharging the heated spinning stock solution from a spinning nozzle, the nozzle is made into a nozzle with each hole protruding,
A DC high voltage of 6 KV or more, preferably loKV or more, or a pulse wave high voltage on one side of Yin and Yang is applied to this. As a result, the spinning solution discharged from the spinning nozzle is charged and split, and then fibers are continuously pulled out from one point of the droplet by an electric field, and a large number of split fibers are dispersed.

Even if the PVA concentration is less than 10%, the solvent dries quickly during the IIR fibril acid formation stage and is transferred to a grounded collection belt or sheet several to several tens of meters away from the protruding nozzle. accumulate. As they are deposited, the semi-dry fibers become slightly agglomerated, preventing movement between the fibers, and new fine fibers are successively deposited to form a dense sheet.

Among the polymers, PVA is the most preferable condition for a-fiber formation, thinning, and semi-drying to cause slight adhesion between the fibers, and the dissolved concentration of PVA also depends on the concentration. It has been found that it is highly dependent on the degree of This was found to be a significantly different concentration range from conventional PVA dry spinning. The heating of the spinning dope is preferably 50° C. or more and 2006° C. or less, and although the degree of polymerization of PVA changes depending on the concentration, it is desirable to control it while checking the stability of spinning. What was particularly important was that, as will be described later, it was necessary to determine the dissolved concentration in the stock solution according to the degree of polymerization of PVA.If the average degree of polymerization of PVA is 7 (according to the Sakurada formula), the preferable dissolved concentration XwL% is , 2L5 54! greater than ogP, 51
．． The dissolved concentration of the polymer is in the range less than 9-11.81 ogP and at least greater than 1 wt%. A dense sheet-like material of 1 ala fine size was obtained by using PVA at the above concentration.

In order for PVA fibers to accumulate in a semi-dry state and bury the wt opening of the sheet to a size of 1μ or less, it is preferable to keep the discharge rate of the spinning stock solution as low as possible from 1.5 to 0.051.
/ex-mtn (area: internal cross-sectional area of the nozzle) is preferable; if it is too large, it deviates from the range of miniaturization and tends to cause unevenness. If the discharge rate is increased to speed up the formation of a sheet-like material, the fiber Mf will be mixed with thick fibers with a diameter of 1 μm or more, and the openings between the fibers will be larger than 1 μm, resulting in poor permeation prevention properties as a medical filter. It was inappropriate. In particular, the performance as a filter for separating protein 'R') was insufficient and it could not be used conveniently.

The PVA-based polymer used here may be any water-soluble polymer, including ordinary PVA, carboxyl group-modified PVA, sulfonic acid group-modified PVA, etc.
Anion-modified PVA such as J acid group-modified PVA or cation-modified PVA or ethylene, long chain alkyl group t-
copolymerized vinyl ether, vinyl ester, (meth)acrylamide, alpha olefin, etc.
Modified PVA, such as one modified with silane, can also be used. As a solvent for dissolving the polymer, in addition to water, organic solvents such as dimethyl sulfoxide, ethylene glycol, glycerin, triethylene glycol, etc. may be mixed, and boric acid, caustic soda, etc. may be added as necessary.

The present invention will be explained below using the apparatus shown in the drawings.

In FIG. 1, a spinning stock solution in which PVA is dissolved is metered and sent by a gear pump, distributed by a distribution and rectification block 2 so as to have a uniform pressure and liquid volume, and sent to a mouthpiece 3. In the cap part, a protruding cap 4 is attached to each hollow needle-like hole, and an electrically insulating part 5 prevents VT air from leaking to the entire cap part 3. A large number of protruding caps 4 made of conductive material are mounted vertically downward in parallel in a direction perpendicular to the traveling direction of a formed sheet take-up device 7 consisting of an endless conveyor. 9 are attached to the protruding cap 4, and each protruding cap 4 enables voltage to be applied to the conductor wire. A grounded conductive member 8 is attached to the endless conveyor of the formed sheet take-up device, so that the applied potential can be neutralized.

The spinning dope, which is force-fed from the mouthpiece 3 to the ejecting mouthpiece 4, is charged and split, and then fibers are continuously pulled out from one point of the droplet by an electric field, and a large number of split fibers are dispersed, forming a semi-dry sheet. It is deposited on the 4-electroconductor member attached to the device 7, becomes finely adhered, is moved by the sheet take-up device, and as it moves, is subjected to the deposition of fine fibers from the next ejecting nozzle. Moreover, a uniform thin film-like sheet is formed. The obtained sheet is subjected to heat treatment and strong drying as necessary, and then taken as a sheet.

Figure 2 shows a scanning electron microscope imitation mirror (S
It refers to a portion where the presence of fibers is not recognized as observed by photographing at a magnification of 10,000 to 30,000 times using EM), and a portion exceeding 1μ is evaluated as having insufficient filter properties.

Sen again! The 1ICrL diameter refers to the minimum unit when the original thickness is clearly recognized even when 2 to 5 fibers are glued together, and is not the thickness after sticking. The average diameter of the fibers in Figure 2 is about 0.2μ, and the opening between the fibers is at most 0.2μ.
It was 8μ.

The present invention will be further explained in detail with reference to Examples below.

The polymerization degree of Example PVA is 1700.3500.5000.1
Using 2500, 16200 and 5 rods, each solution concentration was changed and spinning was carried out under the following conditions. The obtained fiber diameter and the opening area of the sheet were investigated.

Nozzle inner diameter 0.5m++φ EP applied voltage 10 KV Nozzle discharge rate 0.1 f/min Distance M from the tip of the protruding nozzle to the earth wire mesh (2) 50mm Conveyor speed [10c11/min Table 1 Fiber spinning property O 艮 Good △ Slightly unsatisfactory × Some particulates are unsatisfactory The results in Table 1 are expressed by plotting the logarithm of the average polymerization density of PVA (according to the loading formula) on the horizontal axis and the concentration of PVA on the vertical axis.
Those with good fiber spinnability and a fiber diameter of 1μ or less and openings with m spacing of 1μ or less are marked with an ○, and those with a diameter exceeding either of these or with poor spinability are marked with an x. The result is shown in Figure 3. As shown in this figure, the relationship between the average polymerization degree of 9 PVA and the suitable PVArJll expansion was derived, and it became clear that the shaded area in FIG. 3 was obtained. It should be noted that when the degree of polymerization of PVA is less than 500, the stringiness is poor and the result is poor, and when the degree of tEk is less than 1%, a problem arises in terms of uniformity, so it was excluded from the preferred range.

When the degree of PVA polymerization was low, the strength of the sheet obtained tended to be low9, but when the degree of polymerization of PVA was high,
It was observed that the preferred concentration range for obtaining a good thin fiber sheet became narrower, but the strength and tear resistance of the obtained sheet were lowered.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a preferred range of the correlation between the average degree of polymerization and the PVA concentration in a schematic diagram of an apparatus for carrying out the present invention.

Claims (1)

[Claims] (1) A thin film-like polyvinyl alcohol-based fine fiber sheet made up of continuous fine fibers with a fiber diameter of 1 micron or less that are laminated and intersected with each other, and the openings between the fibers are 1 square micron or less. something like that. (2) A voltage of 6 KV or higher is applied to a nozzle from which a nozzle for discharging the spinning dope protrudes from each hole, and the spinning dope that flows out from the nozzle hole is charged, and the spinning dope is heated by the action of a high electric field. When forming fine fibers, the concentration X of the polyvinyl alcohol-based spinning stock solution is adjusted to the range expressed by the following formula (1) in relation to the average degree of polymerization (■) of the polyvinyl alcohol Y. 21.5-5・log■≦Xwt%≦51.9-11.
8・log ■・・・(1) (3) The protruding caps are arranged at equal intervals in one row, in parallel multiple rows, or in multiple rows in a staggered pattern at right angles to the sheet traveling direction, and the solvent of the stock solution is water. 1. A method for producing a polyvinyl alcohol-based fine fiber sheet material.