EP0277234B1

EP0277234B1 - Process for producing non-woven fabric

Info

Publication number: EP0277234B1
Application number: EP87903431A
Authority: EP
Inventors: Miyoshi Okamoto
Original assignee: Toray Industries Inc
Current assignee: Toray Industries Inc
Priority date: 1986-06-10
Filing date: 1987-05-28
Publication date: 1991-11-13
Anticipated expiration: 2007-05-28
Also published as: WO1987007658A1; EP0277234A4; JPS62299557A; EP0277234A1; DE3774561D1; KR880701301A; JPH0361788B2

Abstract

A process for producing non-woven fabric which comprises collecting fibers carried by a high-speed fluid as web, and introducing it into a cloth wrapper to superpose. In this process, the web preferably has such a cross-section distribution that the weight per unit area in both edges is gradually reduced toward the edge. This process enables filament web or filament non-woven fabric with a broad width and remarkably reduced unevenness to be produced by non-woven fabric producing equipment wherein one- or two-spindle spinning machines are directly connected to each other. Therefore, a broad non-woven fabric can be economically produced in a small amount by the spinning-connected process. In addition, the width or weight per unit area of the product can be changed without changing spinning conditions, so that this process is also suited for producing a variety of products with less loss in changing the kind of product.

Description

Field of Art

This invention relates to a novel method of manufacturing non-woven fabric. Particularly, it relates to a method of directly manufacturing fabric enabling the width to be extended with a spinning machine of a small number of spinnerets.

Background Art

Recently, the non-woven fabric industry has been accelerating its tempo of expansion. Particularly, a non-woven fabric manufacturing method having the spinning process and fabricating process directly coupled for reducing the cost, as described in the specification of U.S. Patent No.3,338,992, is extensively used. However, this method requires a high equipment cost and may involve an increased production cost if the production is for a small quantity. Also, it has a limit in improving the homogeneity or isotropy of the web.
On the other hand, for changing the weight (expressed as weight per unit area of fabric) or width, a cloth lapper has been traditionally used. Further, in the Patent Publication No. JP-B-47-29456, a method of obtaining a continuous non-woven fabric consisting of long filaments by opening a tow into a web and supplying the same to a cloth lapper is described. But this method has the filaments oriented and so it is difficult to provide random webs. Moreover, it is very low in productivity.
The present invention is intended to resolve the foregoing problems. Specifically, it aims at excellent homogeneity and high isotropy, and simple width setting, weight setting and production of broad products with a small investment and less selvage loss.
In the method of manufacturing non-woven fabric according to the present invention fibers are (in a manner known per se) collected and carried by high speed fluid into a web. This web is then introduced into a cloth lapper. Examples of cloth lappers are shown in US-A-3 903 568 and DE-A-2 519 493, these cloth lappers cross-lapping the web to form a laminate. The invention is characterised in that the web is formed with a cross section in which the weight near each selvage gradually decreases toward the selvage and terminates in the selvage.
The present invention will now be described in detail.
The first point of the invention exists in the following. That is, while the prior art concentrated directly on the high productivity of fabric, the method of the present invention has its merit found in the combination with a cloth lapper of low productivity against said high productivity.
The cloth lapper produces "lines" incidental to lapping, resulting in defective non-woven fabric with lines. To prevent such defect, the webs have usually been made as thin as practicable as they came out of a short staple card or web making machine before lapping and have been lapped in 50 to 60 thicknesses at a high speed (from the standpoint of productivity) to prevent non-uniformity accompanying the cloth lapping. However, according to a preferable method of the present invention, that is, when the spun fiber filaments are drawn on a high speed air flow to form on the collecting surface a continuous web having the selvages in the form of the skirt of Mt. Fuji, such webs when lapped do not display steps at the selvages as in conventional material, so that the lapping occurs in a very smooth manner, and so a small number of webs may be lapped, but no ununiform stepwise lamintion is produced.
A particularly preferable method of the invention is to apply the filaments withdrawn by a high speed fluid flow onto a reflecting plate or surface which has its direction changed repeatedly to scatter the filaments and thus very effectively form a web of a smooth and even mountainous distribution.
The web of the mountainous distribution has a selvage expressed by the formula $0.01X ≦ Y ≦ 2.0X + 3$
where Y is weight in unit of g/m², and X is the distance from the selvage edge of the web in unit of cm.
The method of deriving the formula is as follows.
The web is cut into squares of a side of 5 cm successively from the selvage edge, and the weight of each square is measured. This procedure is repeated five times for a web, and the mean values are obtained to provide a weight distribution curve in the direction of width of the web.
Next, up to a distance of 20 cm from the selvage edge of the web a primary regression curve of weight in relation to distance is obtained. Here, five values are, of course, to be used for the distance and weight respectively in obtaining the primary regression curve.
Here, it is of course preferable that each selvage of the web is within the range of the foregoing formula.
And, a particularly preferable form of the web selvage is that expressed by the formula $0.05X ≦ Y ≦ 1.0X + 1$
or, more preferably, by the formula $0.05X ≦ Y ≦ 0.6X + ++++0.8$
Further, a web with a correlation function of said primary regression curve of 0.55 or higher is preferable. Particularly preferable is a web of a correlation function of 0.65 or higher.
In the case of a web shown by formula (3), the selvages are very smooth, and so a good web laminate is provided with a small number of webs. In the case of other webs within formula (1), it is preferable to laminate a greater number of webs into a web laminate.
The width of the selvage (where weight changes) is subject to vary with the overall breadth of the web and is not determinable generally, but in many cases, a width of about 20 cm will suffice. It is also possible to electrostatistically repulse the fibers from one another by forced or frictional charging to provide a web having a more homogeneous central part and smoothly decreasing selvages.
The present invention has now been described generally in the foregoing, but the interpretation of the invention is in no way restricted by such description. The method of the invention will now be described more in detail below.
In the present invention, the fluid used for withdrawing the fibers may be air, steam, water or a combination thereof, but a preferable fluid is a gas comprised mainly of air or steam. Air is easy to handle, and steam is advantageous in that it allows collection of fibers and, at the same time, heat treatment or stretching and orientation. In the case of a liquid such as water, it allows a high speed for drawing and is, therefore, effective when a high degree of orientation is aimed at. Such fluid is normally used at room temperature, but by using, for example, high temperature air, the filament quality can be modified.
Next, the form of the fibers collected by such fluid is not particularly limited. The fibers may be in the form of filaments or those obtainable by melt blow or flash spinning. That the fibers are collected in a mountainous distribution enhances the advantages of the method of the invention. The mountainous distribution is readily obtainable from fibers in the form of filaments or staples if they are carried on a fluid for collecting. In the conventional fabric making, on the contrary, efforts were made to reduce selvages in the form of a mountain skirt. Furthermore, filaments, very fine fibers, melt-blow fibers and flash spun fibers could hardly transformed into a web, and so that the method of the invention is applicable to them is very significant.
Accordingly, any material that can be provided in the form of a fiber is usable. For example, there may be used esters such as poly(butylene terephthalate) and Poly(ethylene terephthalate), nylons such as nylon 6, 66 and 610, polyolefins such as polyethylene and polypropylene, flexible polyurethanes, copolymers of poly(tetramethylene glycol) and an amide, ester or urethane, and regenerated celluloses such as rayon.
The fiber used according to the method of the invention may be comprised of one component or be a multi-component fiber. Particularly, fibers that can be subdivided by chemical treatment, mechanical treatment or heat treatment or a combination thereof (subdividable fibers) are preferable. Of such subdividable fibers, those having a plurality of fibers generated from a fiber are preferable. As such fibers, the sea-island fiber, radially subdividable fiber and radially subdividable hollow fiber are representative. By collecting such fiber into a web and upon subdivision through removal of the sea or intermittent component or exfoliation between the components, there is provided a great advantage that the sheet has microunevenness reduced and the texture softened. Particularly, with fibers of 0.2 denier or less used, the texture and evenness are further improved. That is, there is no particular restriction for the fibers used according to the method of the invention, and well-known fibers are well applicable.
Such fibers are collected by a fluid flowing at a high speed into a web. For the collection, any well known method is usable, and thus the collecting method is not limited in any way.
The velocity of the high speed fluid is subject to variation with the kind of the fiber or fluid, cannot be specified in general, and must be determined appropriately through testing. However, in the case of the conventional melt spinning or blow, the speed at which the fiber is spouted or drawn, that is, 2000 m/min or more or, more particularly, 3000 m/min is preferable.
The web obtained by such method may be directly introduced to a cloth lapper into a laminate. Here, however, preliminary bonding is desirable. The non-woven web is very unstable in the form with the fibers merely overlaid upon one another, and, in the process of introducing to the cloth lapper for lamination, it may have a web disturbance such as scraping, cramping or stretching generated by a turbulence or hooking, resulting in uneven folding at the time of lamination to make it difficult to obtain a satisfactory non-woven fabric. But, by preliminary bonding, lamination is effected stably and efficiently. For such preliminary bonding, high speed fluid treatment, needle punching, adhesion, fusion and pressing are suitable.
Such treatment is chosen appropriately depending on the purpose, use and the kind of the fibrous material. Bonding by means of high speed fluid or needle punch has a great degree of freedom of bond between the fibers and is thus advantageous in that various processings are allowed later. It also provides a flexible product.
The fluid or, more particularly, water jet or air jet is suitable for treating a web of very fine fibers. The needle punch may have the needle broken when it is applied to the very fine fibers. But, high speed fluid flow is free from such problem. It also facilitates interwining.
On the other hand, heat pressing with a calendar roll or belt nip used has a fast processing speed and has thus a great advantage that the productivity is high. Use of this method enables the hardening of the texture to be suppressed by using a composite fiber having the core component of a higher melting point than the sheath component.
Also, depending on the kind of the fiber forming the web, it is often seen that the web is charged to preclude smooth movement from the cloth lapper or from the preceding collecting device to the subsequent process. This was particularly noticeable when a web comprised of a less conductive thermoplastic fiber was carried at a high speed, producing a problem that the transfer of the non-woven web from the carrier to the laminate support would become irregular, resulting in uneven folds. In such case, it is preferable to supply at least once a gas containing anions and/or cations to the web before the web is laminated. Thereby, the charge of the web is quickly neutralized to allow the web to drop stationarily from the carrier. That is, a non-woven fabric having the folds evenly arranged is obtainable with less selvage cut loss and improvement of the process yield.
The apparatus used for the method of the invention is preferably made of materials which are not readily charged. Apparatus having a coat of conductive substance over the surface or comprised of conductive materials is preferable. Specifically, for the conveyor of the cloth lapper, apparatus having the surface comprised mainly of cellulose and/or cellulose derivative of small electric resistance is particularly preferable.
In the invention, the type of the cloth lapper is not specifically limited. However, a cloth lapper having the carrier comprised of a pair of belts and carrying the non-woven web between them is preferable, as the non-woven web is scarcely disturbed. Particularly, a cloth lapper of the type pressing the web constantly while lapping is preferable. As a cloth lapper of this type repeatedly lapping while pressing the lapped web to the conveyor, the product of Asran, France, is well known. Moreover, the cloth lapper of this type features in that the lapping speed is high and that the web is not disturbed by the wind incidentally generated by the reciprocal movement.
When the web is too thin, it is entwined over the lattice on the cloth lapper and is hardly laminated. In such case, the web should be lapped continuously on a carrier which is comprised of a gas permeable member and has its black side adapted to slide over the suction port of a gas suction device. Heretofore, a non-woven web of lower weight had a problem of being so much more disturbed by the turbulent flow or mechanical vibration when placed on the carrier, resulting in uneven folds at the edges or creases being generated, and a satisfactory process yield was hardly attained. But, by holding the web on the carrier surface through suction, very exact, stable and efficient laminating is enabled.
The number of layers to be laminated by the cloth lapper is preferably 3-60, or more preferably 5-50, from the uniformity of weight and productivity of the equipment.
The web thus laminated is directly usable effectively. But, it is preferable to bond the layers further for improvement of the ease of handling, physical property and homogeneity. For such purpose, high speed fluid treatment, needle punching, adhesion, fusion and pressing are applied depending on the use. High speed fluid treatment is suitable for production of a flexible non-woven fabric of a weight of 300 g/m² or less or treatment of very fine fibers or partially fibrillary fibers. The Needle punching is used for production of a non-woven fabric of 100 g/m² or more, and adhesion, fusion and pressing are used for production of a non-woven fabric of which a hardness or resilience is required and for production of a sheet used in the field where falling off of fibers from the sheet is to be avoided. Of course, these treatments are usable in combination.
If needle punching is taken for example, when a foundation for artificial suede leather is to be provided, needle punching of 100 needles/cm² or more, particularly 1000 needles/cm² or more, is preferable. When the foundation is for silvering leather, needle punching less than 2000 needles/cm² is generally effective. For development to the sanitary field such as diapers, needle punching of about 200 needles/cm² will suffice. Of course, these values are subject to change with the type of the needle.
The fibers constituting the web laminated by the cloth lapper are generally oriented in a lateral direction, and so stretching the laminated web is effective for controlling the direction of orientation of the fibers. By taking such measure, it is possible to improve the anisotropy in physical properties of the sheet obtained. Stretching of the laminated web is preferably made before the bonding treatment of the laminated web. It is, of course, preferable to give a bonding treatment, then stretching and again give a bonding treatment. Stretching may also be made simultaneously with the bonding treatment.
It is particularly effective for improving the homogeneity and flexibility of the sheet to use subdividable fibers for the web forming fibers and subject them to needle punching or fluid jet punching for subdividing.
As the subdividable fibers, there may be listed the multi-core fibers subdividable into a number of core components such as a polymer oriented fiber, the so-called exfoliating type fibers and the polymer blend fibers. The fibers may, of course, be subdivided in the preliminary bonding or any other treatment. Subdivision does not always mean that the fiber is subdivided over the whole length and includes partial subdivision.
Needle punching has less movement or sliding of fibers with finer fiber to produce needle breaking. As a result, the fibers are not entwined together, but the non-woven fabric has the apparent density increased, that is, takes the so-called corrugated board structure and has thus the quality degraded. Here, the fluid jet or, more specifically, water jet punching works more effectively as the fiber becomes finer and is, therefore, preferable for 0.2 denier or less or, more particularly, 0.07 denier or less. By the water jet punching, it is also possible to exfoliate the multi-core fibers or remove the bond component, and in this case, it is possible to directly produce a non-woven fabric having very fine fibers highly entwined. It should be noted that for the multi-core fibers or relatively thick fibers, needle punching is suitable and that water jet punching is suitable for the fibers which are adapted to become thin or have become thin. The method of the invention satisfies both successfully. As the fibers generating very fine fibers, mention may be made of those sea-island type fibers which have the sea component dissolve in water or hot water. The sea-island fibers having the island component further transformed into a sea-island structure may have very fine fibers obtained readily or the island component removed readily. For better entwining, the number of islands is preferably 50 or more or, more preferably, 100 or more. The upper limit may be as large as 10,000, but, when a high proportion of the island component to the sea component is required, 1000 or less is preferable, 500 or less being more preferable. The proportion of the island component is preferably 75 percent or higher or, more preferably, 85 percent or higher, and the sea component is preferably water-soluble. For needle punching, it is desirable to apply a slippery oiling agent to the fibers. It is also desirable to perform the needle punching with the web heated at a temperature of from 40°C to 100°C. For water jet punching, a columnar jet flow rather than a mist flow is preferable. A preferable water pressure is 70-150 kg per square centimeter. For the long fibers, the water temperature should be 30-60°C, more preferably 45-60°C. Multi-core fibers using for one component a hot water soluble sea component of a copolymer of terephthalic acid, isophthalic acid or 5-sodium-sulfoisophthalic acid with ethylene glycol or a copolymer having polyethylene glycol further copolymerized are particularly suitable. When a polyalkylether or its compound is added to the sea component, destruction of the sea component by the water jet is accelerated to enhance the entwining effect. When a multi-stage water jet punching process is employed, water of a former stage covers the surface of the web to reduce the effect of the subsequent water jet, and so draining water quickly by suction becomes an effective method for entwining.
The effects of the present invention are as set forth in the following.

(1) Long fiber webs and long fiber non-woven fabrics of little unevenness are obtainable. According to the prior art where a number of spinnerets are arranged to produce a sheet of an industrially required width, say, 1-5 meters, there was a limit in reducing the unevenness because of the interference of fluids between the spinnerets and repulsion or attraction of fibers due to charging.
(2) As the process can be directly coupled to spinning, economic small quantity production is enabled. Heretofore, a number of spinnerets had to be arranged for producing a broad product, and this required an investment in a large scale. Consequently, small quantity production was expensive and was substantially difficult. Then, even in the case of a new product having a great demand in prospect, the high cost at the initial stage could not be overcome, resulting in failure as an enterprise.
(3) The process directly coupled to spinning has the width changed with ease. Heretofore, it was very troublesome to change the width with the same equipment, and during the course of change, a considerable product loss was produced. To stop or move some particular spinnerets is not realistic for those who know the actual condition of spinning. Then, the production of a variety of products was not realizable.
(4) The process directly coupled to spinning is adapted to maintain a high yield. According to the prior art, the selvages correspond to the machine edges, and so uniform lamination was not ensured, and they were generally disposed of as a selvage cut loss, being counted as one of the major factors for decrease of the yield. This may be understood upon analysis of many commercial products.
(5) Anisotropy in the longitudinal and lateral directions can be reduced. The spun bond had a serious problem involved that it would be scarcely stretched in the longitudinal direction but readily in the lateral direction (direction of width). This is because the fibers were oriented in a direction at right angles to the arrangement of spinnerets due to interference of the jet flow between the spinnerets. Further, in the subsequent processes of take-up and needle or water jet punching, the sheet was usually stretched, resulting in increasing orientation in the longitudinal direction and then increasing anisotropy.
(6) Change of the weight is facilitated (instantly practicable by changing the speed of the receiving lattice on the cloth lapper or by setting the drive motor speed).

The present invention will now be described in detail with reference to examples, but it should be understood that the examples in no way restrict the interpretation of the invention. The values of evaluation in the examples are those measured and calculated according to the following methods.

(1) Weight and weight variation

From the web, 20 square samples of a side of 5 cm were taken in the longitudinal and lateral directions respectively, and each sample had the weight measured and the weight converted to weight per unit area (g/m²), then the average of all samples was taken as a mean weight (g/m²). Also, for each direction, the percentage of the root of the mean square of the weight to the mean weight was calculated, and such percentage was taken as lateral weight variation (%) and longitudinal weight variation (%).

(2) Tensile strength and tensile elongation

Rectangular samples of 5 cm x 20 cm were taken for the lateral and longitudinal directions respectively, and using a constant speed tensile testing machine of a tensile speed of 10 cm/min, the values of maximum strength and the elongation at the maximum strength were measured and taken as the lateral and longitudinal tensile strength (kg/5 cm) and lateral and longitudinal tensile elongation (%).

(3) Anisotropy

For each characteristic, the percentage of the difference between the lateral and longitudinal values to the mean of the absolute values was taken as anisotropy (%).

(4) Process yield

For each characteristic, the proportion of the weight of class 1 product to that of the materials introduced in percentage terms was taken as the process yield (%).

Example 1

At a spinning temperature of 290°C, and using nylon 6 as an island component and a polymer having an isophthalic component and a 5-sodium-sulfoisophthalic component copolymerized to a poly(ethylene terephthalate) of an impact water and hot water soluble type for the sea component, 24 filaments of a sea-island fiber of an island number of 433 and an island component proportion of 85% were drawn at a high speed through an ejector nozzle, and were applied to an obliquely disposed metal surface, while the angle of the surface was changed repeatedly, and they were collected on a conveyor belt mesh. The width extended over about 120 cm, and about 80 cm at the central part was a web of nearly uniform weight. The web was a good one with the web weight (Y) and the distance (X) from the selvage edge of web expressed by the following formula for both selvages. $Y = 0.3X$
The correlation function of X and Y was 0.88. This web was lapped in a width of 58 inches (1.47 m) while it was held by a high speed cloth lapper, product of Asran, France, in 20 laps (pitch 12 cm). In ordinary card webbing this would be considered deficient in the number of lappings, but a very clean cloth lap web was formed with selvages neatly arranged. Weight was about 120 g/m². The web was subjected to needle punching at a needle density of 50 needles/m² then to water jet punching. The water jet was of oscillating type, and an impact treatment was given at a water pressure of 100 kg/cm² through a nozzle having a number of small holes of 0.23 mm diameter arranged at a pitch of 6 mm. Notwithstanding the long filaments, they were entwined tightly into a firm and very flexible non-woven fabric. The fiber was reduced to very fine fibers, and it was found that by the water jet punch, both entwining and removal of the sea component proceeded simultaneously. The fabric was strong, flexible, scarcely anisotropic in both lateral and longitudinal directions with the selvages scarcely loosened and was very suitable as a wiping cloth.

Example 2

Nylon 6 was spun through a spinning device having two spinning nozzles disposed in a longitudinal direction at a spacing of 32 cm, each nozzle having 156 nozzle holes of a diameter of 0.15 mm, at a spinning temperature of 265°C, then drawn through air ejectors respectively at 5000 m/min, and the filaments thus obtained were guided to hit a metal surface for opening by frictional charging then deposited on a moving wire gauge, and there was obtained a web of a single filament fineness of 0.5 denier, mean weight of 4.8 g/m² and width of 110 cm. Observing the weight distribution of the web by an optical weight gauge incorporated on line, it presented the form of a mountain foot having a flat central part and gradually decreasing side parts. The web had a nearly uniform weight for about 70 cm at the central part and was a good one with the web weight (Y) and the distance from the web selvage end (X) expressed by the formula $Y = 0.23X$
The correlation function of X and Y was 0.83.
Next, the web had a pressing treatment rendered as a preliminary bonding treatment by a pair of 50 cm diameter calendar rollers heated at a surface temperature of 160°C, then it was guided to the carrier of a cloth lapper and was treated with air containing anions and cations and was continuously dropped on a moving support comprised of a gas permeable unit, the back of which slid in contact with the suction port of a gas suction device, with the atmosphere in the vicinity of the surface of said gas permeable unit sucked in the backward direction, into a laminate having an average of 10 layers and a width of 5.9 cm. Further, as a bonding treatment, the top and reverse surfaces were alternately treated twice repeatedly by a high pressure, high speed columnar flow of 25 kg/cm² from a rectangular nozzle having a number of 0.2 mm diameter nozzle holes arranged at a spacing of 1.2 mm which moves reciprocally at an amplitude of 1.2 mm and 20 cycles per minute on the support, then the laminate was dried by hot air of 120°C, and there was obtained a long fiber non-woven fabric of a mean weight of 52 g/m² and a width of 5.7 m. As shown in Tables 1 and 2, this long fiber non-woven fabric was, when compared with the reference, of a broader width, very small in weight variation as well as anisotropy, high in process yield, with the trace of lamination by the cloth lapper scarcely observed and the folds at both ends well arranged, and was thus of a high grade in appearance and was very suitable for clothing such as an operating gown or dust-free clothing or as an industrial material for leather or filter foundation.

Example 3

A web was obtained similarly to Example 2. It was guided to the carrier of a cloth lapper and was treated with air containing anions and cations, then had the lamination, bond treatment and bonding similarly to Example 2, and there was obtained a long fiber non-woven fabric, the mean weight and width of which were nearly the same as those in Example 2. With respect to the weight variation and anisotropy, this long fiber non-woven fabric was a distinguished one similar to that of Example 2, as shown in Tables 1 and 2. The process yield was far superior to the reference.

Example 4

Similarly to Example 2, a web was obtained. It was guided to the carrier of a cloth lapper with no preliminary bonding treatment, then had a voltage of 30 kV applied by a high voltage generator, product of Kasuga Denki, and was treated with air containing anions and cations. Thereafter, it was successively dropped on a moving wooden lattice into a laminate of 10 layers on average and a width of 5.9 m. Further, under the same conditions as Example 2, a bonding treatment and drying were performed, and there was obtained a long fiber non-woven fabric which was nearly the same as Example 1 in mean weight and width. As shown in Tables 1 and 2, this long fiber non-woven fabric was a distinguished long fiber non-woven fabric similar to Example 2 in so far as the weight variation and anisotropy were concerned. The process yield was considerably improved over the reference.

Reference 1

Spinning nylon 6 at a spinning temperature of 265°C by a spinning device having 8 spinning nozzles arranged in the direction of width at a spacing of 13 cm, each nozzle having 39 nozzle holes of 0.15 mm diameter, then drawing at 5000 m/min through an air ejector provided at each nozzle, the filaments thus produced were caused to hit a metal surface for opening by frictional charging then deposited on a moving wire gauge conveyor, and there was obtained a long fiber non-woven fabric of a single size of 0.5 denier, weight of 49 g/m² and width of 110 cm. The direction and angle of the metal surface were carefully adjusted so that the filaments would be deposited as evenly as practicable, while a side plate having a high voltage of 50 kV loaded in order to prevent the web from spreading excessively was provided at each end of the wire gauge conveyor. Then, the web had the top and reverse surfaces alternately treated twice repeatedly by a high pressure, high speed columnar flow of 25 kg/cm² from a reactangular nozzle having a number of 0.2 mm nozzle holes arranged at a spacing of 1.2 mm which makes a reciprocal movement at an amplitude of 1.2 mm and a frequency of 20 cycles per minute in the direction of the width on a support comprised of a 100 mesh wire gauge conveyor. Thereafter, the web was dried by hot air of 120°C and had the selvages cut, and there was obtained a long fiber non-woven fabric of a mean weight of 52 g/m² and a width of 1.0 m. This long fiber non-woven fabric was inferior in the weight variation and anisotropy to Examples 2, 3 and 4 and involved a great selvage cut loss, resulting in a low yield, degraded appearance and smaller width.

Example 5

Using a direct web manufacturing device having five spinning units arranged at a spacing of 30 cm in the proceeding direction, each spinning unit comprised of a melt spinning machine, an air ejector and a reflecting plate, there was successively collected a web consisting of nylon 6 filaments of a mean single size of 0.9 denier and having a mean weight of 14 g/m², a width of 50 cm and selvages similar to those of Example 2. Then, the web had an oiling agent (butylstearate, 6%; ethylene oxide additive of lauryl alcohol, 4%; phosphate static eliminator, 1%; and water, 89%) applied in an amount of 4.5% to the web weight. It was then fed to a cloth lapper at a feed speed of 60 m/min, and there was obtained a laminate of 15 layers and 5 m wide at a discharge speed of 0.4 m/min. The mean weight of the laminate was 210.6 g/m². Successively, the laminate was guided to a uniaxial stretching machine and stretched 1.37 times in the longitudinal direction. By stretching, the laminate width was reduced to 0.95 of that before stretching or 4.75 m. Thereafter, the stretched laminate was guided to a needle punch for a bonding treatment from both top and reverse surfaces at a needle density of 300 needles/cm², then after drying, had each selvage cut by 2 cm, and there was obtained a long fiber non-woven fabric of a mean weight of 180 g/m² and a width of 4.46 m at a speed of 0.5 m/min. The tearing strength of the non-woven fabric thus obtained was 3.9 kg/4.1 kg in longitudinal/lateral direction. With a non-woven fabric obtained similarly except stretching, the tear strength was 4.8 kg/3.0 kg.

Claims

1. A manufacturing method of non-woven fabric including the steps of collecting fibers and carrying them on high speed fluid into a web and then introducing the web into a cloth lapper which cross-laps the web to form a laminate, characterised in that the web is formed with a cross section in which the weight near each selvage gradually decreases toward the selvage and terminates in the selvage.

2. A manufacturing method of non-woven fabric as set forth in claim (1), wherein the cross-sectional distribution of weight has a relationship between the weight at the selvage and at a point within 20 cm from the selvage edge expressed by the following primary regression curve and that the correlation function of the weight at the selvage and the distance is 0.55 or more.

0.01X ≦ Y ≦ 0.9X + 3

where Y represents weight in unit of g/m², and X represents the distance from the selvage edge of the web in cms.

3. A manufacturing method of non-woven fabric as set forth in claim (1) or claim (2), wherein the method of carrrying fibers on a high speed fluid is that of carrying the fibers while blowing them onto a reflective colliding surface.

4. A manufacturing method of non-woven fabric as set forth in any preceding claim, further characterized in that the high speed fluid is at least one of the following:
(i) air; (ii) steam; and (iii) water.

5. A manufacturing method of non-woven fabric as set forth in any preceding claim, wherein the fiber is at least one of the following:
(i) filament; (ii) melt blow fiber; and (iii) flash spun fiber

6. A manufacturing method of non-woven fabric as set forth in any preceding claim, wherein the fiber is comprised of a multi-component fiber having at least two components.

7. A manufacturing method of non-woven fabric as set forth in claim (6), wherein the fiber is a multi-core fiber having cores in a number of at least ten.

8. A manufacturing method of non-woven fabric as set forth in claim (7), wherein the cores are each of 0.2 denier or less.

9. A manufacturing method of non-woven fabric as set forth in any preceding claim, wherein the web lapping is carried out with the web pressed or sucked onto a collecting surface.

10. A manufacturing method of non-woven fabric as set forth in any preceding claim, wherein the web is bonded before it is introduced to the cloth lapper.

11. A manufacturing method of non-woven fabric as set forth in claim (10) wherein the bonding treatment is at least one of the following methods:
(i) entwining treatment; (ii) melt treatment; (iii) adhesion treatment; and (iv) pressing treatment

12. A manufacturing method of non-woven fabric as set forth in claim (11), wherein the entwining treatment is at least one of the following methods:
(i) high speed fluid jet treatment; and (iii) needle punch treatment

13. A manufacturing method of non-woven fabric as set forth in any preceding claim, wherein the lapped web is subject to a bonding treatment.

14. A manufacturing method of non-woven fabric as set forth in claim (13), wherein the bonding treatment is at least one of the following methods:
(i) entwining treatment; (i) melt treatment; (iii) adhesion treatment; and (iv) pressing treatment

15. A manufacturing method of non-woven fabric as set forth in claim (14), wherein the entwining treatment is at least either of the following methods:
(i) high speed fluid treatment; and (ii) needle punch treatment

16. A manufacturing method of non-woven fabric as set forth in any preceding claim, wherein the lapped web is subjected to stretching.

17. A manufacturing method of non-woven fabric as set forth in any preceding claim, wherein the lapped web and is treated with a gas containing ions.