JPH03260154A - Production of nonwoven fabric - Google Patents

Abstract

PURPOSE:To obtain the title bulky ultrathin nonwoven fabric having excellent uniformity in high productivity by using a nozzle having a cut out in which a flow channel of suction fluid is made in such a way that the fluid flows in opposing directions only around an orifice. CONSTITUTION:The objective nonwoven fabric is obtained by using a melt blow nozzle having a cut out in which a flow channel of suction fluid is made so that the suction fluid flows in opposing directions only around an orifice. spinning is preferably carried out at >=5,000sec<-1>, especially 8,000-30,000sec<-1> shear rate.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing bulky nonwoven fabrics made of ultrafine fibers with good uniformity.

(Prior Art) Many proposals have been made regarding efficient manufacturing methods for ultrafine melt blowing.

The method described in Japanese Patent Publication No. 7883/1983 is a method in which the traction fluid is made uniform within the header and provides a condition in which yarn breakage does not occur, but the yarn diameter is as large as 1 denier.

Japanese Patent Publication No. 61-1523 discloses a technique for reducing unevenness in the traction fluid by equalizing the pressure within the header, but this method has problems in improving productivity.

The method disclosed in Japanese Patent Publication No. 43-30018 uses a slit-shaped orifice to achieve high discharge, but the thread unevenness is large. Special Publication No. 43-30017, Special Publication No. 43-20
The methods shown in Japanese Patent Publication No. 248 and Japanese Patent Publication No. 49-6768 are examples of the double traction method, but they are examples of yarns with a large diameter.

Regarding the effective use of traction fluid, see Japanese Patent Publication No. 43-2233.
The method disclosed in Publication No. 3 expands and compresses the traction fluid, and is effective for yarns with a large diameter.

For improved structures around the orifice, see Japanese Patent Publications No. 13210/1970, Japanese Patent Publication No. 22232/1972, Japanese Patent Publication No. 22525/1973, and Japanese Patent Publication No. 22525/1973.
Methods are disclosed in Japanese Patent Publication No. 871, Japanese Patent Publication No. 44-25872, Japanese Patent Publication No. 47-44446, etc.
All of these methods have problems such as thick thread diameter and large thread unevenness.

As a method for improving manufacturing conditions, Japanese Patent Publication No. 44-12848 discloses traction fluid conditions, but the yarn diameter is large and yarn unevenness is large. Japanese Patent Publication No. 5B-33511 discloses a method of lowering the viscosity, but the pore diameter is large and the thread unevenness is large.

JP-A-1-156561 discloses a method for improving the uniformity of fineness. This method uses a decomposing agent to lower the molecular weight in order to meet the conditions set forth in Japanese Patent Publication No. 56-33511, and the orifice diameter is as large as 0.3 mm, and the discharge rate is low at 0.2 g/min, resulting in low productivity. , the thread diameter is 0.
1-5 μm is shown, but in the example it is 1.4 μm.
The best result is a variation rate of 0.15 in m. In other words, it has been shown that even if the viscosity is lowered, it is difficult to make the pores extremely fine if the pore diameter is large.

Japanese Patent Publication No. 50-10992 discloses mixing and spinning to elute the piece components and make the fibers extremely fine, but this method has poor productivity.

Japanese Patent Publication No. 80-22100 discloses applying droplets to promote cooling, but this method is not preferable because it causes noticeable unevenness when the thread diameter is reduced.

Japanese Patent Publication No. 58-12930 discloses an example in which a back spacer is provided on the back surface of the lip, but this is somewhat effective in equalizing and saving the traction fluid, but does not improve productivity much. From the viewpoint of the prior art, it is preferable to make the hole diameter thinner and increase the discharge in order to obtain ultra-fine fineness with good uniformity, but because the pipe length cannot be increased by more than 10 times due to processing, the nozzle does not have the pressure resistance and high discharge cannot be achieved. For this reason, if you try to manufacture a high discharge amount using a nozzle with a large hole diameter, you will not be able to make it extremely fine.

(Problems to be Solved by the Invention) As mentioned above, yarns with a small diameter and good uniformity cannot be obtained with high productivity. In order to solve this problem, it is necessary to be able to increase the discharge amount even if the diameter of the orifice is made smaller. The present invention aims to solve this problem and provide a highly productive nonwoven fabric made of ultrafine fibers with good uniformity.

(Means for Solving the Problems) The present invention adopts the following means in order to solve the above problems. That is, the present invention is a method for manufacturing a nonwoven fabric characterized by using a nozzle having a notch in which the flow path of the traction fluid flows only around an orifice from the direction opposite to the traction fluid.

(Function) The flow path of the traction fluid in the present invention has a notch that allows the flow to flow from the opposite direction only around the orifice.

The thickness of the flow path is added to the portion other than the notch, which is thicker than the thickness of the introduction hole and the slit-shaped traction fluid flow path, and has a higher pressure resistance. Furthermore, the parts other than the notch are supported and reinforced from the outside by the lip, and this part has improved pressure resistance. In other words, only the traction fluid flow path is the weak part related to the nozzle pressure resistance, and the pressure resistance is significantly improved compared to the conventional structure in which the entire slit-shaped traction fluid flow path is the weak part. Specifically, for example, a nozzle in which the introduction hole is slit-shaped, the opening angle of the connection part with the orifice is 45 degrees, the fluid flow path is rectangular, the depth and width are 0.3 seconds, and the pitch between the holes is 1 degree. Assuming that, a nozzle with such a structure is, for example, 5US6
If it is made of 30 martensite E-treated product and the nozzle opening angle is 75 degrees, the yield strength is 85 kg/■■, and the orifice diameter is 0.15. ,,for a hole length of 1.5 mm, the safety factor is 4 times 5.
It has a pressure resistance of 00 kg/cJ or more, which is 1 compared to the pressure resistance of the conventionally known slit-shaped fluid flow path of 50 kg/c+1.
The withstand voltage is improved by more than 0 times.

Furthermore, in this structure, the flow path of the traction fluid is 0.
．． Since the cross-sectional area is three times larger, the flow rate of the drag fluid can be reduced by 0.4 times or less with the same traction force.

Since high-speed fluid flows through the notch, which is the flow path for the pulling fluid of this nozzle, it is necessary to have a shape and cross-sectional area that will not reduce the flow velocity due to the formation of a boundary layer. If the flow velocity is reduced due to the development of a boundary layer, the traction force will be reduced, making it difficult to make the fibers extremely fine, which is not preferable. The width and depth of the notch are preferably at least 0.251 mm, more preferably 0.3 mm or more. If the notch is made too large, the withstand pressure will decrease, so the width should be within 0.5-n and the depth should be 0.5-n.
It is preferably within 411.

The cutout shape can be rectangular, semicircular, semielliptical, etc. Further, the facing angle of the introduction part of the traction fluid is preferably 6
The angle is more preferably 75 degrees to 90 degrees. 1 of the tip part of the nozzle used in such a method of the present invention
A conceptual diagram of an example is shown in FIG. The orifice in the figure has a round cross section, and the cutout flow path has a rectangular cross section. 1 indicates the molten polymer passage, and 2 indicates the high temperature, high velocity jet passage.

In the method of the present invention, it is preferable that the orifice diameter be smaller because the polymer discharge linear velocity can be increased and the draft ratio can be lowered. If the orifice diameter is too large, the effective draft ratio becomes large, and the deformation speed of the discharged polymer increases at a micro level, which may lead to breakage, which is not preferable. A preferable relationship between the orifice diameter and the discharge amount is a shear rate of 5000 seconds or more. More preferably, it is 8,000 seconds or more and 30,000 seconds or less. The preferred viscosity of the polymer at this time is 500
Boise or more and 2000 poise or less, more preferably 700 poise
It is not less than poise and not more than 1500 poise. If the viscosity is too low, the uniformity of the fibers will be poor and yarn breakage will occur easily. If it is too high, it is not preferable because the fibers will not be thin. It is preferable that the velocity of the traction fluid be around the sonic velocity at the orifice exit.

I don't really understand the reason, but if you do this, you can achieve the most efficient thinning even during high discharge. This has a simple shape in terms of structure, and when the discharge amount is high, the traction fluid is supplied at a speed exceeding the sonic speed to the orifice exit, and the traction fluid that is supplied to the lip exit is expanded and accelerated. It is presumed that this is because the discharged polymer can be made thinner efficiently.

In the method of the present invention, the spinning temperature of the discharged polymer is preferably 10°C or more and 80°C or less above the melting point of the polymer. If the spinning temperature is too low, the melt viscosity will increase, which is undesirable, and if it is too high, troubles due to thermal decomposition will occur, which is not preferred. However, this does not apply to those that have a very low melting point and good heat resistance.

The temperature of the traction fluid is at least above the melting point of the polymer and below the melting point plus 200°C, preferably above the melting point plus 20°C and below the melting point plus 100°C.

The reason is not clear, but it can be inferred from the phenomenon that if the temperature is too low, thread breakage occurs frequently, probably because the orifice tip is cooled, and if the temperature is too high, thread breakage occurs frequently again, probably due to capillary breakage. As long as a nozzle having a notched flow path, which is a requirement of the present invention, is used, the temperature of the traction fluid will be at an appropriate temperature.

The method of the present invention is applicable to all polymers that can be melt spun.

The thus spun fibers are taken up by a take-up net having a pick-up function and formed into a nonwoven fabric. When fusion bonding is desired, the distance between the nozzle and the net is shortened, and when fusion bonding is not desired, the distance between the nozzle and the net is lengthened. If the length is too long, rope-like objects will increase, so it is preferable that the distance between the nozzle and the net is at least 1 m or less. It should be noted that in the method of the present invention, the amount of traction fluid is smaller than in the conventional method, so there is less entrained flow and the downstream wind speed is low, so the nozzle
The distance between nets can be made shorter than in the conventional method. This also allowed the nonwoven to be extremely soft and bulky. If necessary, the nonwoven fabric can be subjected to various treatments such as heat treatment, entanglement treatment such as spunlace or needle punching, molding treatment such as heat pressing, embossing, and ultrasonic welding, and resin treatment.

(Example) Example 1 The notch shape, notch radius, and notch depth shown in FIG. 1 are 0.3. ,, hole pitch lam, orifice diameter 0.15 mm, using nozzles with a facing angle of 75 degrees, using air at 290°C as the traction fluid, and using lip back pressure 4 kg/
Polyethylene terephthalate (abbreviated as PET) with an intrinsic viscosity of 0.65 in cJ is discharged at a rate of 0.15 g/
The pore size was changed to 1.0 g/pore, and a nonwoven fabric with a fabric weight of 40 g// was obtained by extrusion at the bottom 40c of the ultrafine fiber forming nozzle. The results are shown in Table 1.

For comparison, the same thread diameter (
Table 1 also lists the conditions for the ejection amount to give a discharge amount of 1 μm). Note that this nozzle burst at a discharge rate of 0.2 g/min.

It is shown in Table 2. For comparison, a normal slit-type fluid flow path nozzle with a hole diameter of 0.2. An example of a discharge rate of 0°2 g/minute hole using a hole diameter of 0.11 cm and a discharge rate of 0.02 g/minute hole are also shown.

A nozzle with a hole diameter of 0.1■■ burst at a discharge rate of 0.08 g/min.

Table 2 Example 2 Using the same nozzle as in Example 1, 300°C air was supplied as the traction fluid at a pressure of 3 kg/C4, and polypropylene with a melt index of 50 was extruded at 270°C by changing the discharge amount. It was taken up at 50c below the nozzle and made into a non-woven fabric. Characteristics of the Obtained Nonwoven Fabric (Effects of the Invention) According to the method of the present invention, a nonwoven fabric made of ultrafine fibers with high productivity and good uniformity can be obtained.

[Brief explanation of drawings]

FIG. 1 is an example of a conceptual diagram of a nozzle used in the method of the present invention. 1... Molten polymer passage 2... High temperature, high speed jet fluid passage. Fang Ding

Claims (2)

[Claims] (1) A method for producing a nonwoven fabric, which uses a melt blow nozzle having a cutout in which the traction fluid flows only around an orifice from the opposite direction. (2) The method for producing a nonwoven fabric according to claim 1, wherein the spinning is performed at a shear rate of 5000 seconds^-1 or more.