KR100332443B1 - Absorbent Improved Nonwoven Fabric - Google Patents

Abstract

The present invention relates to a nonwoven fabric with improved absorption properties.

The fabrics have three different fiber arrangements that are interconnected to create a unique fiber distribution within the fabric.

Description

Nonwoven fabric with improved absorbency

The present invention relates to nonwoven fabrics with improved absorbency.

Nonwovens have been developed in an attempt to produce inexpensive fabrics, eliminating many of the various steps required to produce woven fabrics or knitted fabris. Nonwovens were initially made from card webs or air-laid webs of fibers bonded with a chemical binder. Such nonwoven fabrics have poor strength characteristics and use chemical binders as compared with woven or knitted fabrics, and thus have poor use of the desired absorbency and flexibility. Rearrangement or entanglement of the fibers in the fibrous web produces yarn type fiber segments and entangled fiber regions, greatly reducing or eliminating the amount of chemical binders used in nonwovens. There was a major advance. Methods and devices for making nonwoven fabrics of this nature are described in more detail in US Pat. No. 2,862,251, US Pat. No. 3,033,71 and US Pat. No. 3,486,168. This technique has been able to improve the strength properties of nonwovens, but still falls short of the strength properties of woven or knitted fabrics. Such entangled or rearranged fiber fabrics require a small amount of binder, and therefore have good absorbency and flexibility. As a result, nonwovens are mainly used in many products, such as sanitary napkins, disposable diapers, replacement gauze, medical bands, and the like. These products are used in applications where absorbency and flexibility are required, and the absorbency varies depending on the fiber area. For example, yarn-like structrues differ in their absorbency from non-yarn-like structures. In addition, most of these nonwovens have apertures and are suitable for surface materials, while not being used for some absorbent articles unless used in a multilayer structure. Although the field of application of nonwoven fabrics is wide, there is a need for nonwoven fabrics which improve the absorbency of such nonwoven fabrics and have good efficiency in use.

It is an object of the present invention to produce a nonwoven fabric with improved absorption properties. It is another object of the present invention to produce a nonwoven fabric having substantially uniform absorption properties. It is still another object of the present invention to produce a nonwoven fabric having improved absorption properties without adversely affecting other desirable properties of the nonwoven fabric.

The nonwoven fabric of the present invention is almost uniform in absorbency in all directions within the plane of the nonwoven fabric. The nonwovens of the present invention have a pattern in which three interconnected fiber arrays are repeated. The first fiber array of nonwovens has a number of parallel fiber segments. The second fiber array includes a plurality of twisted and spun fiber segments that form a band disposed almost perpendicular to the parallel fiber segments of the first fiber array. The second fiber array is disposed adjacent to the first fiber array. The nonwoven of the present invention has a third fiber array interconnected with the first fiber array and the second fiber array. The third fiber array has a plurality of highly entangled fiber segments.

Since the nonwoven fabric of the present invention has uniform absorption characteristics, the mean roundness factor of the fluid absorption pattern by the nonwoven fabric is 0.6 or more. In addition, since the fluid absorption pattern generally has a smooth perimeter, the mean form factor is greater than 0.7.

It is believed that the overall absorption properties of the nonwovens of the present invention can be attributed to the characteristic distribution and arrangement of the fibers in the nonwovens. Nonwovens of the present invention generally have a sinusoidal fiber distribution curve over their cross-sectional area. This oblique fiber distribution curve of the nonwoven of the present invention must meet certain criteria. We have found that one way to define and measure these criteria is to mathematically define the fiber distribution curve. This curve can be defined as the cycle or period of the average percent (%) curve of the area covered with fibers and the average amplitude of the curve. The inventors have found that the fiber distribution index of the nonwovens of the present invention is at least 600, preferably at least 800. This fiber distribution index is multiplied by 0.5 times the average number of minimum fiber coverage points clearly identified over the specified cross-sectional area above, and the average percentage of the fiber coverage area of the particular measured cross-sectional area of the nonwoven fabric, divided by the average amplitude of the fiber distribution curve. Measured by

Regarding the drawings, FIG. 1 is a photomicrograph of about 20 times magnification of the nonwoven fabric 20 of the present invention. The nonwovens of the present invention have a repeating pattern of three interconnected fiber arrays. The first fiber array 21 is a plurality of parallel fiber segments. The second fiber array 22 adjacent to the first fiber array is a number of twisted and spun fiber segments forming a band. The bands are arranged almost perpendicular to the parallel fiber segments. The third fiber array 23 connects the first fiber array and the second fiber array and includes a plurality of highly entangled fiber segments.

2 schematically shows a nonwoven of the present invention. As can be seen from this figure, in this embodiment, the bands 25 of some twisted and rotated fiber segments form longitudinally extending ribs with respect to the nonwoven fabric 26. On these bands and on each side connected to the band there is a highly entangled fiber segment 27 extending longitudinally of the nonwoven. Multiple parallel fiber segments 28 are adjacent to and join adjacent regions of the highly entangled multiple fiber segments. These parallel fiber segments are disposed almost perpendicular to the band of twisted and rotated fiber segments.

3A is a cross-sectional view of the nonwoven fabric shown in FIG. As can be seen in this figure, the band 30 of the twisted and rotated fiber segment is the thickest area of the nonwoven, while the multiple parallel fiber segments 31 are the thinnest areas of the nonwoven. These two regions are joined together by a region 32 comprising a plurality of highly entangled fiber segments.

The nonwoven fabric of the present invention is durable. That is, they have considerable strength without chemical binders. Moreover, the nonwovens of the present invention have a unique fiber distribution that provides nonwovens with uniform absorbency as well as durability.

The fiber distribution of the nonwoven fabric can be measured by image analysis of the nonwoven fabric. Image analysis using an image analyzer such as the Leica Quantimet Q520 is a relatively standard technique for measuring fiber distribution in nonwovens. Image analysis is performed on the cross-sectional area of the nonwoven fabric. A piece of nonwoven is cut to about 1 "in the machine direction of the nonwoven and about 3" in the transverse direction of the nonwoven. The nonwoven is dried to remove moisture and then embedded in a transparent resin well known in the art. In the buried process, the nonwoven is kept in a relatively relaxed state. When the nonwoven fabric is appropriately embedded in the resin, a low speed saw can be used to cut thin sections in the transverse direction of the nonwoven fabric. Cut or thinly cut sections are about 6 to 8 mils thick. Many of these cross sections are then analyzed using a Leica Quantimet Q520 image analyzer. A typical image formed by such an image analyzer is shown in FIG. 3A. An image analyzer uses a computer to quantify the image. The cross section of the nonwoven is imaged through a microscope, such as an Olympus SZH model equipped with a stabilized transmitter light source. The video camera connects the microscope and the image analyzer. This image is converted into an electronic signal suitable for analysis. By forming an image of suitable visual contrast using a stabilized transmitter light source of the microscope, the fibers in the cross section exhibit various shades of gray to black, making it easier to match the light gray to white resin background, as shown more clearly in FIG. 3a. Can be identified. This image is divided into sample points or pixels for measurement. The fiber distribution in the cross section can be specified by the change in the cross section, and can be expressed as the fiber area (mm 2) in the specific rectangular measuring frame. In this example, the particular measurement frame is 17 pixels (width) x 30 pixels (height) or about 95 mm 2. To measure the fiber distribution, the fiber coverage or fiber area within the measured frame is examined and measured. The two frames are then advanced across the cross section of the measurement frame and repeated measurements are made for adjacent areas. This is done anywhere from 200 to 300 times depending on the size of the cross section. The fiber regions within each particular measurement area are then plotted in a graph as shown in FIG. The size of the fiber covering area is plotted along the ordinate or Y axis and the position of the particular measurement area from the starting point is plotted along the abscissa or X axis. As can be seen in FIG. 4, about 232 specific dimension areas are measured along the cross section of the nonwoven. The amount of fiber in each particular measurement area is plotted and, as can be seen in FIG. 4, from about 0.10 or 10% of the measurement area covered with the fiber to about 0.30 or 30% of the measurement area covered with the fiber. Change. In selecting the size of the measurement area, the height of the measurement area should be higher than the thickness of the nonwoven fabric. The width of the area should be chosen so that the resolution of the fiber area is excellent. The fiber distribution index of the nonwoven can then be determined from this graph. As shown in FIG. 4, the curve is generally a sinusoidal curve, and the fiber distribution index is multiplied by the number of minimum fiber coverage points that are clearly identified across the cross section and the percentage of average fiber area covered and multiplying this number by the Measure by dividing by the average amplitude.

In FIG. 4, the average fiber area covered is indicated by the dotted line (A). In this embodiment, this coverage area is about 0.23 or 23% of the specific measurement area. Cycles or repetitions are indicated by the numbers I, II, III and IV. In the repetitions I to III, since there are 12 maximum points and minimum points, there are an average of 4 maximum points and minimum points in each repetition number. If you divide these numbers in two, you have two cycles or periods. The average amplitude is obtained by measuring the difference in the amount of fibers between the maximum fiber coverage and the average fiber coverage and the difference in the amount of fibers between the minimum fiber coverage and the average fiber coverage. The maximum fiber coverage point is the point at which the slope of the curve changes from a positive slope to a negative slope. The minimum fiber coverage point is the point at which the slope of the curve changes from a negative slope to a positive slope. Changes in the slope, considered maximum or minimum, should occur at six or more measurement frames or 12 pixel distances. In Figure 4 the mean amplitude of the curve is 0.04. The fiber distribution index of this nonwoven fabric can then be obtained by multiplying the average fiber coverage area by 0.23% by cycle or period 2 and dividing by the average amplitude of the curve 0.04 to obtain a fiber distribution index 1150. The fiber distribution index of the nonwovens of the present invention is at least 600, preferably in the range of about 800 to 3,300. The fiber distribution index of the nonwovens of the prior art is usually considered to be 400 or less. In fact, some prior art have a fiber distribution index of 100 or less.

In general, the nonwoven fabric of the present invention has an average fiber coverage area of 13 to 24%, a period of 1.3 to 4 and an average amplitude of 0.02 to 0.06.

The durability of the nonwovens of the present invention is excellent, and they also surprisingly unexpectedly have very desirable absorbency. Surprisingly, the nonwovens of the present invention have an almost uniform absorbency, with their absorption patterns being nearly circular. In addition, the perimeter of the absorption pattern is relatively smooth. The absorption pattern of the nonwoven of the present invention is shown in FIG.

Absorption patterns are made using a test solution of 0.05% Sandola Rhodamine Red Dye in water. Fill the eye drop with the test solution. Drop 1 drop of solution onto the nonwoven fabric to be tested. Drop one drop with the eyedropper to create an absorption pattern with a diameter of about lin. The nonwoven is supported such that the nonwoven does not come into contact with any substrate that may affect the absorption pattern. A series of drops (10 drops or more for each side of the nonwoven) are applied and placed sufficiently far so that one drop does not collide with an adjacent drop. In the application, the dropper is placed about 1 cm above the nonwoven surface and only one drop is discharged from the dropper to the nonwoven surface. The supported nonwoven is allowed to air dry before image analysis.

In order to measure the roundness of the absorption pattern and the smoothness of the circumference, the pattern is placed under a microscope and the roundness factor and shape factor are measured using appropriate computer software. The roundness factor is determined by measuring the area of the absorption pattern and also by measuring the length of the longest diameter of the pattern. The roundness factor is determined by multiplying the area of the pattern by 4 and dividing the longest length of the square's diameter by "π". The roundness for a perfect prototype is one. The roundness of the absorption pattern of the nonwovens of the present invention has an average roundless factor of at least 0.6, preferably from about 0.65 to 1.0.

The shape factor of the absorbent pattern, ie the smoothness of the perimeter, is determined by measuring the area of the absorbent pattern and the perimeter of the absorbent pattern. The shape factor is 4? × absorption pattern area ÷ (circumference of the absorption pattern) ² . For a perfectly smooth circle, the shape factor is one. The average shape factor of the absorption factor of the nonwoven fabric of the present invention is 0.7 or more, preferably about 0.75 to 1.0.

The "mean" roundness factor and the "mean" shape factor mean the arithmetic mean of the results measured 15 times or more.

6 is a cross-sectional view of an apparatus that can be used to make the nonwoven fabric of the present invention. The apparatus includes a movable conveyor belt 55. The topographically novel support member 56 placed on top of the belt moves with the belt. The support member has a plurality of swelling triangular regions extending in the longitudinal direction. A hole or opening extending through the support member is disposed between the triangular regions (discussed in more detail in connection with FIG. 8), and the fibrous web 57 to be treated is arranged or supported by the inspection of these triangular regions. . The opening in the support member is arranged between the triangular regions. Particular forming members will be mentioned in more detail later. As already mentioned above, there is a fibrous web on top of the support member. The web may be a nonwoven web, such as carded fibers, air integrated fibers, melt blown fibers, or the like. Although the fibrous web is supported on the support member and moved under the manifold to the conveyor belt, the fibrous web is a manifold 58 for injecting fluid 59, preferably water. Water can be injected under various pressures. The fibrous web disposed under the conveyor belt is a vacuum manifold 60 for removing water from the triangular region by passing the web and support member down the fluid manifold. In operation, the fibrous web is positioned on the support member, and then the fiber web and support member are passed under the rapeseed manifold. By injecting water into the fiber to wet the specific fibrous web, it is ensured that the web does not remove or escape from its original position on the support member in subsequent processing. The support member and the web are then passed through the manifold several times in succession. While passing through them, the pressure in the manifold increases to a pressure of at least 1,000 spi at a starting pressure of about 100 psi. Manifolds consist of multiple orifices with about 4 to 100 or more holes per lin. Preferably, the number of holes in the manifold is 13 to 70 per lin.

In this embodiment, there are about 12 longitudinal ribs per web lin. The height of the longitudinal ribs of these triangles is about 0.085 inches. The width of the base of the triangular area is about 0.030 inches. The distance between the triangle regions is approximately 0,053 inches. The diameter of the holes present in the support member is about 0.044 inches, located at 0.0762 inches from the center. After several successive passes of the web and support member under the manifold, the injection of water is stopped and the vacuum is maintained to help the web dehydrate. The web is then removed from the support member and dried to produce the nonwoven fabric described in connection with FIGS.

In figure 7, an apparatus for continuously producing a nonwoven fabric according to the invention is shown. The schematic diagram includes a conveyor belt 80 which acts as a support member according to the invention. The belt continuously moves in the counterclockwise direction with respect to the member at a distance, as is well known in the art. Above the belt is located a fluid supply manifold connecting the multiple lines or groups 81 of the orifice. Each group lists more than one row of fine diameter holes with more than 30 holes per lin. The manifold is equipped with a pressure gauge 87 and a control valve 88 for regulating the fluid pressure in each line or group of orifices. Underneath each orifice line or group is a suction member 82 that removes excess water to prevent undesirable flooding. When processed, the fibrous web 83 to be formed into the nonwoven fabric of the present invention is supplied to a support conveyor belt. Spraying water onto the fibrous web through a suitable nozzle 84 facilitates control of the fibers as they pass under the pressure manifold because the web is presoaked or prewet. Suction box 85 is disposed below the water nozzle to remove excess water. The fibrous web passes under the fluid supply manifold, where the pressure in the manifold is preferably increased gradually. For example, the first line of holes or orifices provides a fluid force of 100 psi, while the next line of orifices provides a fluid force of 300 psi, and the final line of orifices provides a pressure of 700 spi. It can provide health. Although six lines of orifices are shown, the number of lines or rows of orifices is not critical and depends on the width, speed, working pressure of the web, the number of rows of holes in each line, and the like. After passing between the fluid supply manifold and the fluid suction manifold, excess water is removed from the web when the formed nonwoven passes through the additional suction box 86. The support member may be made of a relatively hard material and may include a number of slats. Each slat extends across the width of the conveyor, with ribs on one side and shoulders on the opposite side, so that the shoulder of one slot can be moved between adjacent slots by engaging ribs of adjacent slots and being relatively rigid The member is adapted to be used in the conveyor form shown in FIG. Each orifice strip consists of one or more rows of very fine diameter holes with a diameter of about 1 / 5,000 to 10 / 1,000 inches per lin. There are about 50 holes per lin across the orifice.

8 is a perspective view of one type of support member that can be used to make the nonwoven of the present invention. The support member is comprised from the board 90 provided with the rising rib area | region 91 located in the longitudinal direction at predetermined intervals. The plate has twelve raised rib areas per lin. The raised rib region has a triangular cross-sectional shape with a width of about 0.03 inches below the triangle. The ribs are 0.085 inches in height and reach a point with a closing angle of about 20 ". The base of the ribs is spaced about 0.053 inches from the adjacent rib base. In the area between these ribs, the opening of the plate ( 92) or openings, the openings extending longitudinally or longitudinally of the plate between each adjacent rib, the openings being about 0.044 in diameter and spaced 0.0762 in from the center of the opening. The raised areas of the support members used to make the nonwoven fabric of the present invention should have a height of at least 0.02 in. The width of their bases should be about 0.04 to about 0.08 in, and the width of their tops should be the width of the base. In a preferred embodiment of the support member used in the present invention, the cross-sectional area is a triangle in which the width of the top is actually zero. The space between the adjacent raised areas should be at least 0.04 in. The openings in the space between adjacent raised areas should be about 0.01 to 0.045 in diameter and the distance between the openings should be about 0.03 to 0,1 in.

The following is a specific example of a method of making the nonwoven fabric of the present invention.

Example 1

Nonwovens are manufactured using the apparatus depicted and described in FIG. It takes a random wepdang 1½oz of 1yd ^2, by stacking them on top of each card web 1yd ² 1oz to prepare a 100% of the web of fiber per 1½oz 1yd ^2. The thus laminated web is placed on the support member described in FIG. The support member and the web are passed through at a rate of 92 ft / min under the columnar jet stream produced from the orifice shown in FIG. Three passes under pressure of 100 psi and nine passes under pressure of 800 psi. The diameter of the orifice is 0.007 inches and there are about 30 orifices per lln so that the added energy is about 0.8 horsepower / 1b. The web is spaced about 0.75 inches from the orifice. In this way, after performing the first machining, the web is removed from the support member, and the reverse side of the web is inverted so as to contact the orifice jet. The support fan containing the inverted web is placed under a water jet at a speed of 4 yd / min. The web and support member are passed once at 600 psi and further through twice at 1500 psi. The web is dried and the fiber distribution of the web is detected. The fiber distribution index of this web is about 820. Samples of the web are tested for absorption properties using the absorbency tests already described. The average roundness factor of the absorption pattern of this sample is about 0.6 and the average shape factor of the absorption pattern of this sample is 0.72.

The support members used to make the nonwoven fabric described above all have ribs extending in the longitudinal direction, but the ribs need not extend longitudinally. Support members having a horizontal rib or a diagonal rib, or a combination of diagonal ribs, horizontal ribs and / or longitudinal ribs can be used for the production of the nonwoven fabric according to the present invention.

9 shows another form of member forming a plate that can be used to make the nonwoven fabric of the present invention. The member includes a plate 94 having raised rib regions 95 arranged diagonally. The rib regions are distributed in a herringbone pattern. This pattern is formed by parallel slanted lines in rows adjacent to the columns forming the V shape or the inverted V shape. The cross section of each rib is triangular in shape with a triangular top 96 forming the top surface of the member. Between the parallel rows in its region at the triangular base 97 there are a number of openings 98 or holes penetrating the thickness of the plate.

FIG. 10 shows a micrograph of a nonwoven fabric according to the present invention, which is manufactured utilizing the support member shown in FIG.

Example 2

The nonwoven fabric shown in FIG. 10 is made from 100% cotton at ² ozoz per 1 yd ² fiber web. The web is placed on a 100 × 92 mesh bronze belt and pretreated by passing it at 92 ft / min under a columnar water jet stream. Three passes under the srim at 100 psig followed by nine passes at 800 psig. The jet stream is produced from orifices (0.007 in diameter) arranged in lines with 30 orifices per inch. The web for the orifice space is 0.751 n. The pretreated web is collected from the bronze belt and inverted, and then the pretreated web surface is exposed to a water jet stream located on the mold plate shown in FIG. The web and plate are passed at a rate of 90 ft / min under a column jet stream as described above. One pass at 600 psig followed by seven pass at 1400spig. The treated web is removed from the molded plate and used to produce the nonwoven fabric shown in FIG.

As can be seen in the micrograph, nonwoven 1000 has a herringbone pattern of three interconnected fiber arrays. The first fiber array 102 includes a plurality of fiber segments. The second fiber array 101 is a band of twisted and rotated fiber segments, which bands are disposed almost perpendicular to the parallel fiber segments. The third fiber array 103 includes a plurality of highly entangled fiber segments interconnected with the first fiber array and the second fiber array.

As the invention is referred to in certain aspects and as illustrated by way of example, it is possible for those skilled in the art to modify, modify, improve and extend the basic principles contained in the invention without departing from the spirit or scope of the invention. It is obvious.

1 is a photomicrograph of about 20 times magnification of the nonwoven fabric of the present invention.

2 is a perspective view of a nonwoven fabric in which a photograph is shown in FIG.

3a is a computerized image of a partial cross section of a nonwoven fabric according to the present invention in which a fiber distribution curve is shown.

4 is a fiber distribution diagram which is generally sinusoidal developed from the image shown in FIG. 3A.

5 is a photograph of an absorbent pattern produced by the nonwoven fabric of the present invention.

6 is a cross-sectional view of one type of apparatus for making the nonwoven fabric of the present invention.

7 is a view showing the configuration of different types of apparatus for manufacturing the nonwoven fabric of the present invention.

FIG. 8 is an enlarged perspective view of a type of topographic support member that can be used in the apparatus shown in FIG.

9 is an enlarged perspective view of another type of local support member that can be used to make the nonwoven of the present invention.

10 is a micrograph at about 20 times magnification of another nonwoven fabric according to the present invention.

Claims (8)

A first fiber array comprising a plurality of parallel fiber segments. A second fiber array comprising a plurality of twisted and rotated fiber segments forming a band disposed substantially perpendicular to a fiber segment parallel to the first fiber array; A third fiber array interconnecting the first fiber array and the second fiber array and comprising a plurality of highly entangled fiber segments, The absorbency is almost uniform in all directions in the plane, A nonwoven fabric having a repeating pattern of interconnected first fiber arrays, second fiber arrays, and third fiber arrays. The nonwoven fabric of claim 1, wherein the band is continuous and extends to the length of the fabric. The nonwoven fabric of claim 1, wherein the bands are spaced at regular intervals from adjacent bands. A nonwoven fabric comprising a plurality of interconnected fiber segments, the absorbency being nearly uniform, the fluid absorption pattern having an average roundness factor of 0.65 to 1.0 and the smoothness around the pattern being an average shape factor of 0.7 to 1.0 ( non-woven fabric characterized in that it has a formfactor. A nonwoven fabric having a nearly uniform absorbency and having a fiber distribution curve that is generally sinusoidal over a cross-sectional area, 0.5 times the average number of maximum fiber covering points and minimum fiber covering points in one cycle multiplied by the average percentage of the fiber covering area of the nonwoven cross section and the fiber distribution index divided by the average amplitude of the fiber distribution curve is 800 to 3,300 nonwovens. 6. The nonwoven fabric of claim 5 wherein the average number of minimum and maximum coverage points in a cycle is four. 6. The nonwoven fabric of claim 5, wherein the average amplitude of the fiber distribution curve is from 0.02 to 0.06. 6. The nonwoven fabric of claim 5 wherein the average percentage of fiber coverage areas is 13-24%, the average number of maximum fiber coverage points and minimum fiber coverage points in the cycle is 4 and the average amplitude of the fiber distribution curve is 0.02 to 0.06.