JPH0233313A - Ultrafine hollow fiber and nonwoven fabric - Google Patents

Abstract

PURPOSE:To obtain an inexpensive ultrafine hollow fiber for heat insulation material consisting of a thermoplastic high polymer having specific single fiber area and hollow ratio and having bulkiness regardless ultrafine string and excellent heat retaining property as well as softness, waterproofing property, permeability, etc. CONSTITUTION:The ultrafine hollow fiber obtained by spinning a thermoplastic high polymer having <=40mum<2> single fiber cross section and >=3% hollow ratio using a nozzle 1 having 60-120 deg.theta widening angle of nozzle tip, 0.2-2.0mm distance L of nozzle tip and 0.03-0.1mm tip flat part 4 as well as trapezoid cross section according to melt blow method. The above-mentioned hollow fiber is used, preferably at amount of >=50%, more preferably >=100% to provide the nonwoven fabric.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to ultrafine hollow fibers with excellent heat retention and bulkiness, and nonwoven fabrics containing the hollow fibers.

(Prior art) Nonwoven fabrics made of ultrafine fibers obtained by the melt-blowing method are moisture permeable and waterproof, pliable, and have a large yarn surface, but their ultrafineness reduces bulk, making them difficult to breathe in still air. decreases, and the insulation effect decreases.

Japanese Patent Publication No. 50-10992 has proposed a method for improving bulkiness, but it requires complicated operations such as matrix dissolution, water washing, and drying, and such post-processing steps
Since non-woven fabrics have reduced bulk, they cannot yet be bulky enough and have excellent heat retention properties.

On the other hand, hollow fibers have good elasticity, are bulky, and have hollow parts, so they are said to have a relatively good heat insulating effect.
As exemplified in U.S. Pat. No. 3-35026 and US Pat. No. 299929E3, ultrafine yarns of less than 1 denier have not been achieved, and are only several steps inferior to ultrafine yarns in terms of thinness, lightness, and good heat retention. do not have. In addition, as for ultra-fine heat insulating materials, it is stated in Japanese Patent Publication No. 83-31581 that the fineness is 0.1 to 30 denier and that the cross-sectional shape can be various shapes such as circular, irregular shape, hollow, etc., but 0.5 denier. No performance or technical disclosure regarding the following ultrafine hollow fibers has been made.

(Problems to be Solved by the Invention) An object of the present invention is to solve the above-mentioned drawbacks of conventional products, and to provide a thin, light, excellent heat retaining material, moisture permeable and waterproof, and flexible heat insulating material at a low cost. The task is to

(Means for Solving the Problems) The present invention provides an ultra-fine hollow fiber characterized by being made of a thermoplastic polymer having a single fiber cross-sectional area of 40 μm or less and a hollowness ratio of 3% or more, and the ultra-fine hollow fiber. The above problem is solved by a nonwoven fabric containing yarn. The present invention will be explained in detail below.

The single fiber cross-sectional area of the ultrafine hollow fiber of the present invention is 40 μm 2 or less.

If the thickness exceeds 40 μm2, it is not preferable because it is inferior in coverage, moisture permeability and waterproofness, heat retention, and flexibility when made into a thin nonwoven fabric. In addition, in the case of polyester fiber, 4
A single fiber with a cross-sectional area of 0μ corresponds to 0.5d.

Preferable single fiber cross-sectional area is 20 μm or less, 0.01 μm
2 or more, more preferably 10μm or less, 0.05μ
m2 or more, and if it is smaller than 0.01 μm, it is not preferable because the hollow bulk, shape retention, and appropriate elasticity are poor.

The hollowness ratio of the ultrafine hollow fibers of the present invention is 3% or more.

3% ungrooved fabric is not preferable because when it is made into a non-woven fabric, air content, bulkiness and appropriate elasticity are lowered, and heat retention is also poor. The preferred hollowness ratio is 5% or more and 50% or less, and if the hollowness ratio is too high, the hollow portion will be easily crushed and flattened, resulting in poor bulkiness, which is not preferable. More preferably 8% or more4
It is 0% or less.

It is thought that the ultrafine hollow fibers of the present invention, when made into a nonwoven fabric, exhibit the characteristics of ultrafine fibers and hollow fibers as a synergistic effect.

In other words, although the reason for this is not clear, the hollow part can be reliably maintained even when the airflow velocity in the atmosphere is extremely high, and in addition, even if it is made extremely thin, the moment of inertia of area is high, and it is difficult to maintain close-packed light against external forces. Because it is extremely thin, the surface area increases due to the ultra-fine structure, and the boundary surface increases due to the increase in the number of constituent pieces, which increases the ventilation resistance of high-speed airflow and maintains a large still air layer in the aggregate, resulting in bulkiness. ,
It is thought that heat retention will also improve. In addition, coverage and water resistance are improved, and the porous structure and bulkiness make it possible to maintain moisture permeability. The composition constituting the ultrafine hollow fiber of the present invention consists of a thermoplastic polymer. The reason for this is that the molten polymer is made into ultra-fine hollows by the melt blowing method, which will be described later. Preferred examples of the composition of the ultrafine hollow fiber of the present invention include polyester, polyamide, polyolefin, polyacrylonitrile, polyvinyl chloride, and copolymers and blends thereof.

These high molecular weight polymers may contain up to 10% of modifiers, matting agents, impurities, etc. However, if they are in the form of particles, the particle size is preferably 0.3 μm or less.

The ultrafine hollow fibers of the present invention have not been obtained by conventionally known methods, and have only been made possible by melt blowing. In particular, in the case of nozzle orifice shapes that do not form hollow fibers in conventionally known nozzle orifice shapes, such as x-shape, to-shape, 2-shape, n-shape, etc., the hollow cross section is C (), Qo.
, @, etc. are obtained. In the C type, etc., it becomes a crushed G cross section.

The reason for this is not clear, but as an example when using the trapezoidal cross-section nozzle shown in Figure 1, the force in the streamline direction of the fluid ( It is presumed that the lateral component force (Fi) of F) acts to push the dissolved polymer flow exiting the orifice from the side wall surface into the center of the nozzle orifice, forming a hollow portion. In addition, at this time, since the contact area of the molten polymer flow in contact with the pulling fluid is large, it is possible to achieve a draft ratio that would be unimaginable in normal spinning or the conventionally known melt blowing method with a round cross section, making it possible to obtain ultra-fine hollow fibers. It is assumed that this is the case. As an example of a nozzle dimension suitable for ultra-fine hollow formation, the nozzle tip angle θ is 4.
5 degrees or more, preferably 60' or more and 120 degrees or less, and the nozzle tip angle IJL is 0.01 degrees or more, preferably 0.
2■■ or more and 2.0m or less, flat end W is 0.2
1 or less, preferably 0.1 μl or less to 0.03. ■ Above,
The orifice width D can be any desired width, but is preferably 2 liters or less in view of the utility cost of the traction fluid, and the lip opening width W preferably satisfies 0.8D≦W with the orifice width. If 0.8D>W, thread breakage may occur.

The spinning temperature is 20°C or higher than the melting point of the polymer used1.
The temperature is preferably 50°C or lower, but even higher temperatures are possible if the residence time can be shortened. Hollow fibers may not be formed at temperatures below T m +15°C.

The shape of the orifice is not particularly limited as long as it is symmetrical with respect to the center of the flat portion and a hollow space of 3% or more is formed, but the shape described above is more preferable.

Although the temperature of the traction fluid is not particularly limited, it is preferably at least the spinning temperature when the purpose is to obtain ultrafine particles of 10 μm 2 or less.

When obtaining a desired fiber area, the flow velocity of the traction fluid may be appropriately set in the sonic to subsonic range in balance with other conditions and discharge amount. Exceeding the speed of sound may cause thread breakage. However, if the thread is not grooved at 50 m/s, the thread cross section will be 40 m/s.
It may not be less than μI, so at least 50m/
It is preferable to set it to more than a second. Suitable traction fluids include air, steam, nitrogen, and the like.

The discharge amount varies greatly depending on the individual spinning conditions, polymer properties, nozzle, etc., but for example, in the case of polyethylene terephthalate, at a spinning temperature of 290°C, using air as the traction fluid, and at a temperature of 290°C, the discharge amount per single hole is at least 4g/. It is preferably 2 g/pore or less.

If the nozzle orifice shape shown in Fig. 1 is used, 0.3 to 0.8 g/minute hole is suitable for desiring 2 μm or less. The cross-sectional shape of the obtained fiber was C9.

In order to make the ultrafine hollow fibers obtained under the above conditions into a non-woven fabric, a known method for making a sheet by stacking them with a net having a succilon function or the like can be applied. The pick-up position can be before or after solidification is completed, if necessary. Since it is preferable that the single fibers are not bonded to each other, in the case of polyethylene terephthalate, the distance is sufficient to cool down to below the solidification point, and the condition is that 30
It is set to about 60 cm. The apparent bulk density of the taken-up nonwoven fabric can be adjusted by lightly pressing it with a heating roller or by embossing it if necessary, but it is preferable to take it up in the form of a sheet and then set it by non-contact heating to increase its bulk. It is desirable to maintain gender.

The nonwoven fabric containing ultrafine hollow fibers thus obtained has both the characteristics of ultrafine fibers and hollow fibers described above.

The content of ultrafine hollow fibers contained in the nonwoven fabric of the present invention is at least 30%, preferably 50% or more, and more preferably 100%. If it is less than 30%, the effect is undesirably poor.

(Example) Examples are given below to further clarify the effects of the present invention.

Note that the characteristics of fibers defined in the present invention refer to values measured by the following method.

■ Single fiber cross-sectional area (S) From the obtained fibers or nonwoven fabric, embed 300 or more fibers in acrylic resin, create a section, and then elute one end and photograph the section with an electron microscope at 2000 to 5000 times. 100 pieces were randomly selected from the enlarged photograph (10,000 to 20,000 times), the cross-sectional area (St) was measured, and the average value (μm2) of the 100 pieces was shown.

■ Hollowness ratio (HV) Measure the hollowness ratio (HVi) from the 100 pieces above, and
Shown as average value (%) of books.

■ Ultra-fine hollow fiber content A non-woven fabric is embedded in acrylic and one section is eluted. The section is photographed at 2000 to 5000 times magnification using an electron microscope. 200 fibers are randomly selected from the enlarged photograph and the hollow fiber content (%) is determined. .

Examples 1 to 5, Comparative Examples 1 to 6 Polyethylene terephthalate (intrinsic viscosity 0.80) and polypropylene (melt index 40) were used as polymers by melt blowing under the conditions shown in Table 1. The sheet was manufactured.

The obtained single fiber properties and sheet evaluation results are also listed in Table 1. Although the material of the present invention is extremely thin, it is bulky, soft, and has excellent heat retention. The bulkiness of the sheet performance evaluation is the bulk under a load of 0.2 g/eJ, and the thermal resistance value is ASTM-D-
Compliant with 1518, flexible enough to touch 20 people
~Very soft is ranked as ◎.Waterproofness is ranked as ◎ with no leakage at water pressure of 0.2kg/cJ~Completely water permeable as ×, and moisture permeability is rated as 100 in a room at 20℃ x 20% RH.
One side of the box with RH99% inside the box of 0cc (10c*X 10
cm) as a sheet and the time to equilibrium is 0 to 6 within 5 minutes.
It is evaluated by ranking with 0 minutes or more as X.

(Effect of the invention) The nonwoven fabric containing the ultra-fine hollow fibers of the present invention is bulky and has excellent heat retention despite being ultra-fine, and also has the characteristics of ultra-fine fibers such as softness, waterproofness, and moisture permeability. This makes it possible to provide a material that is ideal for functional heat insulating materials, especially clothing heat insulating materials.

It can also be widely used as various industrial insulation materials, various filter materials, impact materials, integral molding materials, soundproofing materials, medical materials, etc.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a nozzle for obtaining ultrafine hollow fibers of the present invention, and a conceptual diagram of an assembled part viewed from below. 1...-nozzle, 2--lip, 3...-orifice 4--tip flat portion, 5--lip surface. Patent applicant: Toyobo Co., Ltd. No. 1 @ 1 ... Nozu II / 2 ° Schiff 0 3 ... Orifi person

Claims (2)

[Claims] 1. An ultrafine hollow fiber characterized by being made of a thermoplastic polymer having a single fiber cross-sectional area of 40 μm^2 or less and a hollowness ratio of 3% or more. 2. A nonwoven fabric comprising the ultrafine hollow fibers according to claim 1.