JPS6026859B2 - Nonwoven fabric stretching device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for stretching a nonwoven fabric made of synthetic fibers to increase its strength, and more particularly, to an apparatus for stretching a nonwoven fabric made of molecularly oriented fibers in both the longitudinal and lateral directions.

Various nonwoven fabrics and (continuous filament) spun bonded webs are commercially available as fiber substitutes.

This type of non-woven fabric is made of short fibers or continuous filament-like unstructured fibers, and is either unstretched or partially unstretched, so its strength is favorable. do not have. A technique for improving the tensile strength of fibers by orienting molecules through a stretching process is already known as a stretching method in the production of films made of oriented (molecularly orientable) fibers such as polyethylene.

However, even if this technology is directly applied to a nonwoven fabric and stretched in the longitudinal direction using a conventional godet roller, the nonwoven fabric will narrow in the lateral direction, and tensile force will not effectively act on the fibers between the bonding points of the fibers. No molecular orientation occurs in individual fibers. Further, in a method in which the side ends of the nonwoven fabric are held with a clamp or the like and the nonwoven fabric is stretched in the lateral direction, tearing tends to occur at the gripping portion. In such a method, if a single tear occurs, tensile force will be concentrated there and the tear will become larger. In nonwoven fabrics, each fiber is bonded at the intersection by adhesive or heat fusion, but in the case of a nonwoven fabric made of particularly short fibers, the number of bonding points in one fiber is small, so the tensile force against one bonding point is small. The load becomes so large that it exceeds the bonding strength and the individual fibers tend to separate. The present invention takes the above-mentioned facts into account and aims to provide a device that can evenly stretch the entire surface of a nonwoven fabric between bonding points of individual fibers.

The present invention is an apparatus for stretching a nonwoven fabric made of molecularly oriented fibers in the longitudinal and lateral directions, which comprises a first pair of meshing rollers having grooves parallel to the axis, and a second pair having grooves perpendicular to the axis. It has a pair of meshing rollers, and is characterized in that the pattern of the grooves in the transverse direction on each roller of each pair of rollers substantially corresponds to a sine wave.

The groove spacing of each roller corresponds to the standard weight of the nonwoven fabric before stretching in g.
It is desirable to select a value that is less than or equal to the value expressed in /.

According to the present invention, a nonwoven fabric made of molecularly oriented fibers is stretched evenly in 20,000 directions in the vertical and horizontal directions in each meshing roller pair, and the standard weight is reduced by that amount. A nonwoven fabric with improved strength is obtained.

The invention will now be described in detail in accordance with the embodiments illustrated in the accompanying drawings, but drive and support mechanisms, timing and safety circuits, and other parts known to those skilled in the art are omitted for the sake of clarity.

FIG. 1 shows the first extension section of the device according to the present invention, in which a nonwoven fabric 12 consisting of oriented fibers (continuous or discontinuous) is attached to a support roll 10.

The nonwoven fabric 12 passes between the nip 14 of a pair of rollers 16, 16 having a number of holes 18 parallel to their axes, as shown in FIG. The speed V of the nonwoven fabric 12 is the same as that of the grooved roller 1.
A pair of press rollers 21 press the nonwoven fabric 12 onto the lower grooved roller 16 so that the surface velocity V of
come into contact with. The grooves 18 of both rollers 16, 16 have a transverse groove pattern corresponding to a substantially sinusoidal wave and mesh with each other like gears. Nonwoven fabric 12 is nip 1
4, the nonwoven fabric 12 takes on the shape of a sine wave of the grooves 18, and the thickness at the tip of each groove is determined by dividing the sinusoidal wavelength of the grooves ``W'' (FIG. 3) by the initial length ``W'' of the nonwoven fabric 12. It is stretched between solution points. That is, since the speed at which the nonwoven fabric 12 is introduced into the nip 14 is limited by the press roller 21, the nonwoven fabric 12 is not caught in the nip 14 along the waveform, and is introduced by the amount "W". This is because that. When the groove shape is a sine wave, the stretch ratio /W is calculated by the following formula.

〆/W=' no 10aZos2× Ship ÷ During the raising ceremony, a=
d/W, where d is the depth of the groove.

That is, if d/W is 1.0, 0.75, and 0.5, the stretch ratios/W are 2.35, 2.0, and 1.6, respectively.
After roller 16 passes nib 14, nonwoven fabric 12 is pulled out by a pair of tension rollers 22.

The surface speed V2 of this tension roller 22 is
6, but not greater than the ejection velocity of the stretched nonwoven in the nip 14. Note that the nonwoven fabric 12 does not become narrower while being stretched in the longitudinal direction, as would be the case with a secondary roller system.

It will be apparent to those skilled in the art that if it is desired to further stretch the nonwoven fabric 12 in the longitudinal direction, multiple pairs of grooved rollers 16 may be provided to sequentially pass the nonwoven fabric 12 through. If the stretching process continues beyond the residual elongation of each individual fiber, the strands will break and
Nonwoven fabric 12 loses its tensile strength. Up to the point of fiber failure, the strength per standard weight of the fabric increases considerably. By measuring the residual elongation of individual fibers of the raw material nonwoven fabric, the maximum allowable elongation ratio can be easily determined. If excellent results are to be achieved with the aim of producing heavy products of standard weight, the grooves 18 of the roll 16 must be made as narrow as possible and the groove depth must be increased. In light of experience, the groove spacing (unit fence) is set to 1. Excellent results can be obtained as below. The greater the depth of the grooves, the wider the spacing between the fiber intersections, which can lead to destruction and weaken the fabric structure. In the case of nonwoven fabrics consisting of short staple fibers, the depth d of the grooves should be 1/2 of the fiber length or less. If the groove depth d is greater than this, the fibers will break and separate rather than being stretched between the grooves, resulting in a very weak nonwoven fabric. Next, referring to FIG. 4, the first extension section including the press roller 21 is
a pair of rollers 26 in which the nonwoven fabric 20 stretched in the longitudinal direction has a plurality of grooves 28 parallel to the circumferential direction of the second stretched portion;
into a nib 24 formed by 26.

Passing the nonwoven fabric 20 into the nip 24 is by a pair of press rollers 30 that press the nonwoven fabric 20 against a lower roller 26 to prevent it from constricting prior to introduction. When you enter Nip 24,
The nonwoven fabric 20 is shaped according to the pattern of grooves 28 and is stretched at a stretch ratio calculated similarly to the stretch ratio described in connection with FIG. In the second stretching section, ie, the lateral stretching section, the nonwoven fabric 32 discharged from the nip 24 is wound onto the rollers 36 at the same speed as the feed speed. As the product is wound into a loaf 36, the nonwoven fabric 32 is stretched laterally by a tenter clamp or a curved mount hope roll, as known to those skilled in the art, to flatten the crimp pattern. For better results, the longitudinal and lateral stretching is repeated in stages at relatively low stretching ratios until the final acceptable stretching ratio is reached. The number of stretching steps in the longitudinal and machine directions and the magnitude of the stretching ratio at each step may be selected to yield a homogeneous final fabric that is directionally balanced. With the device of the present invention, the tensile tear strength (load g/fabric width m) and the tensile tear length per standard weight (tension tear strength/fabric standard weight: unit m) are improved compared to unstretched fabric. Much higher non-woven fabrics are obtained.

In the stretching process, the standard weight of the fabric is reduced by a factor of areal stretch ratio (longitudinal stretch ratio x transverse stretch ratio). The denier of the individual fibers is similarly reduced, resulting in a nonwoven fabric consisting of thinner fibers, although the bonds are not yet broken. The fabrics produced according to the invention are softer than the original material, resulting in an entirely new type of product. Examples of use of the apparatus of the present invention will be described below, but these are merely for illustration purposes, and the present invention is not limited to these examples.

Example 1 A non-woven nonwoven fabric (where the intersections of the filaments form the Melt・
(mostly melted in the blowing step) were processed according to the invention.

Standard weight: 10 mm filament denier: 1-5 tensile tear strength
:78 mustache/handling line) tensile tear length
:788h The surface speed of this nonwoven fabric is 3/min.
．． Introduced to roller 16 at 08h.

The groove length d of each groove was formed into 3 grooves, and the interval W was formed into 4 legs so that the stretch ratio was 2.0. The nonwoven fabric 20 is moved to the nip 1 by a tension roller 22 with a surface speed of 6 plates per minute.
Pull out from 4. When the nonwoven fabric was sequentially stretched into longitudinal and transverse stretches that were similar to each other, a final stretch ratio of 16.0 was reached, and the nonwoven fabric exhibited the following properties. standard weight
:6. / Elbow filament denier
: 0.1-1 Tensile tear strength : Moth. Love/enemy (line) tensile tear length:
Tensile tear length per standard weight of 1 ball 7m product (unit: m)
was 1 gruel 7 to 785 for the original polypropylene fiber material.

Example 0 Depth 2.5 kite, Width 5. A commercially available spun-bond wep consisting of continuous polyester fibers having the following properties was processed with a grooved roller in the cross section (stretch ratio 1.6).

Standard weight: 6 cone/filament denier: 15 Tensile tear strength: 110 Cover/skin (wire) filament elongation: 250% Surface speed: 3.
The web is introduced into the roller 16 at 05h, and the speed is 4/min.
．． It was pulled out by a tension roller 22 of 88 m.

After passing through two complete stretching steps (both including longitudinal and transverse stretching), the weave exhibited the following properties. Standard weight: 2 acids/
Filament denier: 6 Tensile tear strength: 787. The tensile tear length (unit: m) of the product is 1749.2 of the original polyester material.
It was 3149.6.

Implementation m 1.27 skin polyester with the following properties.
A latex bonded nonwoven fabric consisting of staple fibers was processed in accordance with the present invention.

Standard weight: 3 mm / filament denier: 7 tensile tear strength
:157. One rib in depth and three strips in width (stretch ratio 1.8) were formed on each roller for the chick/rival (line).

After biaxial stretching followed by pressing between calender rolls, the nonwoven exhibited the following properties: standard weight
:1 spot/pillow filament denier
:4.0 Tear strength :1
77. Tensile tearing strength of the product (unit: m)
was 984.4 compared to 492.2 for the original material.

The present invention has been described above with respect to the case where the nonwoven fabric first passes through the vertical (longitudinal) direction stretching section and then the horizontal direction stretching section, but the stretching section is first introduced into the blind direction stretching section. Needless to say, they may be replaced. Also,
The device of the present invention may be configured to stretch longitudinally to the stretch limit of the material prior to lateral stretching.
Although the present invention has been described with reference to illustrative examples, those skilled in the art will readily recognize that various modifications may be made thereto, and this application is intended to cover any and all adaptations or improvements.

Accordingly, the invention is limited only by the scope of the claims and their equivalents.

[Brief explanation of the drawing]

FIG. 1 is a simplified side view of the first extension section of the device of the invention, FIG. 2 is a perspective view of one of the rollers of the first extension section, and FIG. 3 is a sine wave curve. FIG. 4 is a simplified side view of the second extension section, and FIG.
The figure is a plan view of the second extension section. 10...Support roller, 12...Nonwoven fabric, 14...Nip, 16...O-roller, 18...Groove,
20...Nonwoven fabric, 21...Press roller, 22... - Punsion roller, 24...Nip, 26...Roller, 28...Groove, 30...Press row, 32...Nonwoven fabric, 36. ．．・．． ．．・Loaf of/evening. /'/G. 2'ノ6.3 f/G. Child F/G. evening

Claims (1)

[Scope of Claims] 1. A device for stretching a nonwoven fabric made of molecularly oriented fibers in the longitudinal and lateral directions, comprising: (a) a first pair of meshing rollers having grooves parallel to the axis; and (b) an axis. a second pair of meshing rollers having grooves perpendicular to the center; (c) and a pattern in a direction across the grooves of each roller of the first and second pairs of meshing rollers substantially corresponds to a sine wave; A nonwoven fabric stretching device characterized by: