JPS6123288B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing electret defibrated and wound fibers, and more specifically, to a method for producing electret defibrated and wound fibers, and more specifically, to a method for producing electret defibrated and wound fibers, which has excellent dust collection and dust retention properties and is useful as dust control products, filters, etc. This invention relates to a method for producing a novel electret defibrated and wound yarn.

Conventionally, a thermoplastic resin film that can be oriented by stretching, such as polyethylene or polypropylene, is stretched to form a fibrillated film, and friction or mechanical force is applied to this film in the lateral direction or in the stretching direction. It is known to produce split fibers by mechanically creating a number of fissures along the length of the fiber. Such a fibrillated yarn has the characteristics of having minute and relatively uniform fluff, and being lightweight and bulky. Furthermore, since fibrillated yarns such as polioflaine have the property of being electrically charged by friction, for example, fluff flutters in which these fibrillated yarns are implanted have excellent dust-collecting and dust-retaining properties. Look forward to it. However, in experiments conducted by the present inventors, flutter using bird feathers showed a dust retention rate of about 20%, while that of defibrated yarn was 5%, and defibrated yarn subjected to crimping treatment showed a dust retention rate of about 20%. Even in the case of 15 to 20%,
It is still unsatisfactory in its practical effectiveness.

It is already known to convert defibrated yarn into an electret and use this as a filter. For example, Japanese Patent Application Laid-open No. 132223/1984 discloses a method for manufacturing a filter made of electret fibers by stretching a film of polypropylene or the like, charging it by corona discharge, and then defibrating it with a needle roll. . This invention has important significance in that it has succeeded in producing electret fibers, which are difficult to produce, by a combination of the steps of charging a stretched film and defibrating the charged film. Electret fibers are still not fully satisfactory in terms of dust collection and dust retention.

The present inventors have discovered that when the electret defibrated yarn obtained by the above-described method is subjected to crimping treatment under specific conditions detailed below, significant attenuation of the electric charge,
That is, it has been discovered that electret defibrated crimped yarn can be obtained for the first time, which can be crimped without loss of electret action and has excellent dust collection and dust retention properties.

According to the present invention, there are steps of stretching a film made of olefin resin in the longitudinal direction, defibrating the stretched film, and subjecting the film to corona discharge at any stage before or after defibration. The process of charging the charged defibrated film with 110
Provided is a method for producing an electret defibrated and crimped yarn, which comprises a combination of a step of crimping at a temperature of .degree. C. or lower.

In the method of the present invention, the olefin resin film can be stretched by means known per se. As the olefin resin, any olefin homopolymer, copolymer, or blend thereof that can be oriented by stretching can be used, and suitable examples include polyethylene, isotactic polypropylene, and ethylene-propylene copolymer. etc.
The present invention uses isotactic polypropylene and polyethylene in a ratio of 95:5 to 70:30, especially 85:15 to
It can be suitably applied to a film of a polyolefin blend containing a polymerization ratio of 75:25. That is, the film made of this blend not only yields a fibrillated yarn having a uniform and fine fiber structure by stretching and fibrillation, but also can be easily electrified and crimped. When the content of polyethylene is less than the above range, crimping can be applied to a degree effective for dust collection and retention at a relatively low temperature at which substantial attenuation of charge does not occur. On the other hand, when the content of polyethylene is higher than the above range, significant attenuation of the charge appears to occur even when the crimping treatment is carried out at a relatively low temperature. Film stretching is generally
It is preferable to carry out the stretching at a stretching ratio of 6.0 to 8.5 times. Stretching can be carried out using a device known per se, and can be easily carried out, for example, by passing the film between two pairs of rotating rolls having different circumferential speeds at a temperature higher than room temperature and lower than the softening temperature of the olefin resin. can. When stretching is carried out under heating, a hot roll, hot plate, heated air bath or other heating medium can be used as desired. There is no particular limit to the film line speed, but it should be between 60 and 60.
A speed of 140 m/min is advantageous in terms of workability.

The film can be easily charged by subjecting the stretched film to corona discharge. As a corona discharge mechanism, a combination of a discharge electrode such as a corona wire or an electrode with many needles and a counter electrode is used. This is easily accomplished by applying a voltage, for example a DC voltage of 3 to 15 KV. The distance between the discharge electrode and the film varies depending on the applied voltage, but is generally 3 to 10 mm.
Just choose an appropriate interval from the range. The discharge treatment may normally be performed once, but it can be performed multiple times if desired. For example, one surface of the film may be subjected to positive corona discharge, and the other surface may be subjected to negative corona discharge. can. The surface potential of the film rapidly attenuates after the corona discharge ends, but reaches a certain saturation potential after a certain period of time, and the film becomes electret.

A charged stretched film can be easily defibrated by fibrillating the film itself, by applying friction or mechanical force in the lateral direction of the film, or by bringing the film into contact with a rotating needle roll. It will be done. Generally, the latter method is advantageous. The gap between each load in the needle roll is preferably in the range of 0.2 to 2 mm.

Instead of subjecting the stretched film to the charging process and the defibrating process in the above order, the defibrating process may be performed first and then the charging process.

An important feature of the present invention is that when the thus obtained electret defibrated yarn is subjected to a crimping treatment at a temperature of 100°C or less, a defibrated and crimped yarn in the form of electret can be easily obtained. This is based on the knowledge that shrunken fibers have significantly superior dust adsorption and retention properties. Generally, the manufacturing method of crimped yarn is based on the principle of deforming the internal structure using physical or chemical strain within the filament, and the drawn yarn is heated with hot water or steam. A method of relaxing heat treatment in a heating medium such as a method of strongly twisting the yarn, a method of combining the yarn with a mechanical member or rubbing it against this,
Methods are known in which the yarn is brought into contact with a fluid jet. Regardless of which of these crimping methods is adopted, in the case of electret defibrated yarn, if the crimping temperature exceeds 110°C or less, the dust collection rate of the product crimped yarn will decrease significantly. This fact will become immediately clear by referring to the comparative examples described below. The exact reason for this is unknown, but it is believed that the higher the crimping temperature, the greater the crimping effect, but at the same time the effect of the electret is diminished due to excessive deformation and relaxation of the internal structure. Seem.

In a preferred embodiment of the present invention, the electret fibrillated yarn is subjected to a fluid jet, preferably at a temperature below 110°C.
The crimping process is carried out by contacting with a jet of hot air at 60 to 110°C. The contact between the electret defibrated yarn and the fluid jet is achieved by blowing the fluid jet into the passage of the fibrillated yarn, which has an introduction part at one end and an injection hole at the other end, and creates turbulence or vortex flow in the passage. This can be easily done by forming a . Such a crimping device is well known per se, and is described in, for example, Japanese Patent Publication No. 35-6684 and Japanese Patent Publication No. 36-8123. Air is preferably used as the fluid, but
Other gases may also be used. The pressure of the fluid may be such as to form the above-mentioned turbulent flow or eddy flow within the passage of the defibrated yarn, and is generally preferably in the range of 5 to 25 kg/cm ² .

For the crimping treatment of the electret defibrated yarn, the above-mentioned strong twisting method, abrasion method, etc. can be used on the condition that the treatment temperature is 100° C. or less, but heat treatment methods should be avoided.

The electretted defibrated wound yarn according to the present invention is
It has significant advantages over non-electrified defibrated and wound yarns.

It has been known that polyolefin fibers are easily triboelectrically charged. However, since the fibrillated and curled yarn is triboelectrically charged, the external electric field is strong, causing discomfort to people and causing so-called static electricity damage. In addition, even if dust is attracted from a distance, the electric charge is easy to move, so the dust will fall off easily, and once the dust falls, it will be repelled and escape because it has the same charge. Although it looks good at first glance, triboelectric charging has such inadequacies as dust control.

On the other hand, the electretted defibrated and crimped yarn according to the present invention has a small external electric field due to the coexistence of ○+ charges and ○- charges, so it does not have the power to attract dust from a distance, but once it comes in contact with If you do this, the dust will not be released, and since the charge is fixed,
It does not cause static electricity damage, and has the remarkable advantage that dust does not easily fall off because the electric charge does not transfer to the dust.

The electret defibrated and crimped yarn according to the present invention has a fine and bulky fiber structure due to the electret process and the crimping process, so it has dust collection and retention properties compared to conventional fiber materials. It has the advantage that these characteristics are maintained permanently. Taking advantage of this advantage, the electret defibrated and curled yarn of the present invention can be used to make cloths, cloths, rags, dusters, brushes, dusters, etc. by spinning, knitting, weaving, nonwoven fabric forming means, etc. It can be used as a cleaning material for mats, etc., and as various filters.

The invention is illustrated by the following example. Example 1 and Comparative Examples 1 and 2 A blend consisting of 80% by weight of isotactic polypropylene and 20% by weight of high-density polyethylene was formed into a film with a thickness of 0.08 mm by the T-die method at a resin temperature of 230°C in the die section. It was filmed. This film was stretched in the longitudinal direction at a stretching ratio of 7.1 times, and then the distance between the film electrodes was 5 mm, and the needle density was 0.2.
The specimens were subjected to corona discharge treatment under the conditions of 100 kg/cm ² and an applied voltage of ±10 KV. The film line speed is
The speed was 100m/min. The charged stretched film was brought into contact with a rotating needle roll with a needle spacing of 1 mm, and then the electret fibrillated yarn was wound around a bobbin.

The defibrated thread unwound from the bobbin is heated at an air temperature of 80°C.
℃, air supply pressure 7.0Kg/cm ² and air volume 0.01m ³ /
The yarn was fed into a fluid jet device at a speed of 50 m/min, and the yarn ejected from the device was wound onto the bobbin of a twisting machine so that the number of twists per inch was 0.2.

The resulting electret defibrated and curled yarn was formed into a feather with an ear length of 100 mm, and the dust rate was measured by the method described below. How to measure the dust rate The dust rate is measured by cutting the panicle from any part of the formed flycatcher, bundling one end and using it as a sample. Place the sample in a plastic container, vibrate the container for 30 seconds, take out the sample, measure the amount of attached dust, and use the following formula: dust attached sample weight - sample initial weight / sample initial weight x 10
Calculated from 0 (%).

For comparison, the same procedure was applied to the defibrated yarn (Comparative Example 1) which was not subjected to the electrification treatment and crimping treatment in the above example, and the defibrated and crimped yarn (Comparative Example 2) which was not subjected to the electrification treatment. It was molded into a square shape and the dust rate was measured.

The dust rate of the defibrated yarn of Comparative Example 1 was 5%, and the dust rate of Comparative Example 2 was 5%.
The dust ratio of the defibrated and wound crinkled yarn of Example 1 was 20%, whereas the dust ratio of the electret defibrated and wound crinkled yarn of Example 1 was 56%. Comparative Examples 3 and 4 For comparison, the electret fibrillated yarn obtained in Example 1 was defibrated and crimped in the same manner as in Example 1, except that the electret fibrillated yarn was crimped with hot air at a temperature of 130°C. A yarn (Comparative Example 3) was produced.

Further, the electret fibrillated yarn obtained in Example 1 was subjected to relaxation heat treatment in a heat treatment air bath at a temperature of 180°C to produce an electret fibrillated yarn (Comparative Example 4).

These fibrillated yarns were molded into a hataki in the same manner as in Example 1, and the dust rate was measured, and it was found that Comparative Example 3
showed a dust ratio of 36%, and Comparative Example 4 showed a dust ratio of 27%.

Example 2 Hataki using a yarn obtained by crimping the electret defibrated yarn obtained in Example 1 by a known abrasion method showed a dust rate of 43%.

Claims (1)

[Scope of Claims] 1. A step of stretching a film made of olefin resin in the longitudinal direction, a step of defibrating the stretched film, and subjecting the film to corona discharge at any stage before or after defibration. 1. A method for producing an electret defibrated and crimped yarn, which comprises a combination of a step of charging the electret fibrillated filament with a temperature of 110° C. and a step of crimping the charged defibrated film at a temperature of 110° C. or lower. 2 The olefin resin contains isotactic polypropylene and polyethylene in a ratio of 95:5 to 70:
A method according to claim 1, comprising a blend containing a weight ratio of 30. 3 The film made of the olefin resin is 6.0
The method according to claim 1, wherein the film is stretched by a factor of 8.5 to 8.5 times. 4. The method according to claim 1, wherein the film before or after defibration is charged by passing it between a pair of corona discharge mechanisms. 5 The crimping treatment of the charged fiber film is carried out at a temperature of 60°C.
The method according to claim 1, which is carried out by bringing a jet of hot air at a temperature of 110° C. to 110° C. into contact with the defibrated film.