KR960011614B1 - Cross-laminated stretched non-woven fabric and method for making the same - Google Patents

Abstract

None.

Description

Cross-overlapping Nonwovens and Manufacturing Method Thereof

1 is a schematic perspective view showing how a cross-overlapping nonwoven is produced from two consecutive identical identical nonwoven webs longitudinally stretched in accordance with the present invention.

2 is a schematic perspective view showing how a longitudinally stretched nonwoven web and a laterally stretched nonwoven web are laminated to form a crossover overlapping nonwoven fabric in accordance with the present invention.

3 is a bottom view of the spinning nozzle used to form the transversely aligned or arranged filaments of the web.

FIG. 4 is a schematic vertical cross-sectional view showing a device incorporating the spinneret shown in FIG. 3 to form a nonwoven fabric in which the filaments are laterally laid.

5 is a cross-sectional view taken along the line V-V in FIG.

6 is a schematic view showing a general structure of a near longitudinal drawing device.

7 is a schematic view showing a general structure of a rolling device for rolling a nonwoven fabric.

8 is a schematic perspective view of an apparatus including pulleys for stretching the nonwoven in the lateral direction.

9 is a partial cross-sectional view of a device that includes a pair of grooved rolls cooperating to stretch the nonwoven in the transverse direction.

* Explanation of symbols for main parts of the drawings

1, 21, 26: warp web 2a, 2b, 2c, 3, 33: weft web

23: continuous webs 4a, 4b, 6, 15a, 20, 22a, 22b, 25: nip rolls

5, 24a, 24b: pressurized roll 7, 13, 14, 27, 36: nonwoven fabric

8: spinning nozzle 9: filament

10-1 to 10-6: 1st air hole 11: 2nd air hole

12 shielding network 16 cylinder

17a, 17b: stretched roll 18: heat treatment roll

19: cooling roll 23, 28, 31: direction change roll

29a, 29b: pulley 30a, 30b: belt

32: heating chamber 34a, 34b: home roll

35: tooth

The present invention relates to a cross-laminated nonwoven fabric composed of warp webs and weft webs laminated alternately with each other and having strength in both the longitudinal and transverse directions. It relates to a method for producing.

Throughout this specification and claims, the term slanted web refers to a web formed of fibers arranged to extend substantially in the longitudinal direction of the web and having a greater longitudinal strength than the transverse direction. The term weft web likewise refers to a web formed of fibers arranged to extend substantially in the transverse direction of the web and having a greater transverse strength than the longitudinal direction. Furthermore, a higher order nonwoven fabric refers to a layered nonwoven fabric consisting of a warp web and a weft web in which the layers of the warp web intersect with the fibers of the weft web and are bonded together.

Conventional random nonwovens have good bulkiness and texture, but have only a limited strength that cannot be compared with the strength of the fabric. In addition, the permeability and filterability of the nonwoven fabrics are excellent. This excellent permeability and filterability has led to the recent application of nonwovens to geo-fabrics (fiber materials for soil engineering and building construction). However, this new application is virtually limited because of the limited strength of conventional random nonwovens. In view of these difficulties, the present inventors have made various attempts to increase the strength of conventional nonwoven fabrics. In one such attempt, there is provided a nonwoven fabric of laminated construction consisting of parallel nonwoven warp webs and parallel nonwoven weft webs combined with warp webs, wherein the fibers of the warp web intersect the fibers of the weft webs. . The strength of this laminated nonwoven fabric is increased, but still less than that required for civil engineering and building geo-fabrics.

In view of these difficulties, it is an object of the present invention to provide a cross-overlapping nonwoven that has a strength comparable to that of a fabric and thus can be used as a geo-fabric, ie, a fiber material for civil engineering and building.

It is another object of the present invention to provide a method of making such overlapped stretched nonwovens at increased production rates.

According to the first aspect of the invention,

(a) a first web of stretched nonwoven fabric formed by combining a plurality of substantially stretched filaments, wherein the stretched filaments are non-stretched filaments before being stretched, and are stretched in the longitudinal direction such that each non-stretched filament is substantially stretched The first web to cause an orientation

(b) a second web of stretched nonwoven fabric formed by combining a plurality of substantially stretched filaments, wherein the stretched filaments are non-stretched filaments before being stretched, and each non-stretched filaments are stretched transversely so as to be substantially stretched; Thus, there is provided a cross-overlapping nonwoven composed of the second web laminated to the first web in such a way that molecular orientation occurs and the stretching directions of each of the first and second webs are perpendicular to each other.

According to a second aspect of the invention,

(a) a first web of stretched nonwoven fabric formed by joining a plurality of substantially stretched filaments, wherein the stretched filaments are non-stretched filaments before being stretched, and are stretched in the longitudinal direction such that each non-stretched filament is substantially stretched The first web to cause molecular orientation

(b) a second web of stretched nonwoven fabric formed by combining a plurality of substantially stretched filaments, wherein the stretched filaments are non-stretched filaments before being stretched, and are stretched transversely so that each of the non-stretched filaments is substantially stretched; A cross-overlapping nonwoven composed of the second web laminated to the first web is provided so that molecular orientation occurs and the stretching directions of each of the first and second webs are orthogonal to each other.

According to a third aspect of the invention,

(a) forming a first web of random nonwoven formed by joining substantially unoriented filaments;

(b) stretching the first web in a longitudinal direction such that each non-stretched filament is substantially stretched to cause molecular orientation in the web;

(c) forming a second web of random nonwoven that substantially combines non-stretched filaments;

(d) stretching the second web in a longitudinal direction such that each unstretched filament is substantially drawn to cause molecular orientation in the second web;

(e) laterally cutting the second web such that each length of the second web piece is equal to the width of the first web;

(f) Laminating the second web piece on the first web such that the extending direction of the first web and the extending direction of the second web piece are orthogonal to each other such that adjacent edges of the second web piece slightly overlap each other. Provided is a method for producing a cross-overlapping stretched nonwoven fabric composed of steps.

According to a fourth aspect of the invention,

(a) forming a first web of random nonwoven combining substantially non-stretched filaments;

(b) stretching the first web in a longitudinal direction such that each non-stretched filament is substantially stretched to cause molecular orientation in the web;

(c) forming a second web of random nonwoven combining substantially non-stretched filaments;

(d) stretching the second web laterally so that each non-stretched filament is substantially drawn, causing molecular orientation in the second web;

(e) There is provided a method of manufacturing a cross-overlapping stretched nonwoven fabric comprising laminating the first web and the second web in such a manner that the stretching directions of the first web and the second web are perpendicular to each other.

Throughout this specification and claims, the term non-stretched filaments refers to filaments that are not drawn or stretched filaments, filaments without molecular orientation, or filaments that can be stretched more than twice their original length when stretched at an appropriate stretch temperature. Say.

Other advantages and features of the present invention will become apparent with reference to the accompanying drawings, in which the following detailed description and examples are shown.

1 shows a method of continuously producing superimposed stretched nonwoven in accordance with the present invention. The overlapped stretched nonwoven fabric is a continuous warp web 1 which is a longitudinal (lengthwise) stretched nonwoven formed of approximately longitudinally aligned filaments, and a series of weft webs 2a, 2b, 2c which is a stretched nonwoven fabric. The weft web is coupled to the warp web 1 with adjacent edges overlapping each other. When the continuous web 2 is fed transversely over the inclined web 1 appropriately for the movement of the inclined web 1, the continuous length is a longitudinally stretched nonwoven fabric, the individual length being substantially equal to the width of the inclined web 1. The web 2 (same as the warp web 1) is cut continuously and these weft webs 2a-2c are disposed on the warp web 1. The warp web 1 and the weft webs 2a-2c disposed thereon are then joined together by heat bonding with an adhesive. The adhesive is held in at least one of the warp web 1 and the continuous web 2 in the form of adhesive filaments produced simultaneously or separately with the extrusion of the main polymer, short staple fibers, adhesive powder or bubbles. Bonding the warp web 1 with the continuous web 2 first involves immersing the webs 1, 2 in an adhesive liquid such as an emulsion adhesive and then removing the webs 1, 2 to remove excess adhesive. Squeeze and finally dry the webs 1, 2 by force or in a natural state by means of a hot drum, hot air chamber or infrared oven. The warp web 1 and the continuous web 2 may be joined together mechanically by sewing.

According to the cross-overlap process, even if the width of the non-woven fabric is greater than 3m it can produce a cross-overlapping stretched nonwoven fabric at a speed of 40-50m / min. Another advantage arises when the webs 1, 2 are stretched in the longitudinal direction prior to bonding, since they increase the bond strength between the respective filaments due to the cross overlap of the warp web 1 and the continuous web 2. Local separation or breakage of the bond may also be repaired or regenerated. The thus produced cross-overlapping stretched nonwoven has great strength in the longitudinal and transverse moduli. For example, the tensile strength of this nonwoven fabric is at least three times the tensile strength of a conventional random nonwoven fabric of the same weight as the nonwoven fabric. Similarly, this nonwoven fabric has an impact strength, tear strength, punch resistance, and seal tear resistance of about five times that of a conventional random nonwoven fabric. Moreover, the Young's modulus of the present nonwoven fabric is usually at least five times the nonwoven Young's modulus and the elongation of the present nonwoven fabric is substantially smaller than that of the nonwoven fabric. Therefore, the cross-overlapping stretched nonwoven fabric of the present invention is excellent in dimensional stability.

2 shows another lamination process according to the invention, in which a continuous warp web 1 that is a longitudinal or longitudinally stretched nonwoven fabric and a continuous weft web 3 that is a transversely or transversely stretched nonwoven fabric overlap each other. Is supplied to the lamination apparatus. Cross-overlapping warp webs 1 and weft webs 3 are nip rolls 6 abutting a pair of nip rolls 4a, 4b, hot press rolls 5 and press rolls 5 which cooperate. Join together as they move continuously around. In the same manner as in the embodiment shown in FIG. 1, the warp web 1 and the weft web 3 are joined by adhesive bonding. In the case of using an emulsion adhesive as the adhesive, the nip roll 4a is applied so that the adhesive is applied to the webs 1 and 3 when the warp web 1 and the weft web 3 move around the nip roll 4a. Partially submerged in an emulsion adhesive bath. The strength of the crossover nonwoven fabric 7 is substantially the same as that of the crossover nonwoven fabric of the first embodiment shown in FIG. In contrast to the weft webs 2a-2c of the second embodiment shown in FIG. 1, the weft webs 3 have no overlapping areas in succession, so that the nonwoven fabric 7 is structurally uniform throughout the entire area.

The filaments constituting the warp web 1 and the continuous web 2 and the weft webs 2a-2c, 3 consist essentially of unstretched filaments before being stretched. The non-stretched filaments are formed by the melt spinner shown in FIGS. 3 to 5. A central spinning nozzle 8 for extruding a spin melt made of polymeric material to form a melt spinner filament 9 and a filament 9 being spiraled by applying air to the filament 9 while the filament 9 is being extruded A plurality of (6 in this embodiment) beveled first air holes 10-1-10-6 arranged circumferentially equidistantly around the spinning nozzle 8 to move to a conical bottom ) And first air to be disposed on both sides of the spinning nozzle 8 to direct air in a direction opposite to the direction of movement of the shielding network 12 to form two air streams impinging at a position just below the spinning nozzle 8. It consists of a nozzle plate or spinneret having a pair of opposite horizontal second air holes 11, 11 located downstream of the holes.

Due to these two impinging air streams, the spirally moving filaments 9 spread out laterally in a direction perpendicular to the direction of movement of the nonwoven 13 web during formation on the shielding net 12.

The slanted first air hole 10-1-10-6 of the spinneret extends in a tangential direction to the spinning nozzle 8 as shown in FIG. 3 and also as shown in FIG. 4. It is inclined at an angle to the central axis. According to this arrangement, the air exiting from each of the air holes 10-1-10-6 is concentrated in an area spaced several centimeters to 10 cm or more below the spinning nozzle 8. The air flow thus collected causes a spiral movement of the filament 9 described above. The filaments 9 deposited on the shielding net 12 are mainly laid or aligned in the transverse direction of the nonwoven fabric 13 during production, so that the nonwoven fabric 13 is particularly suitable for the transverse stretching of the nonwoven fabric. Alternatively, the air escaped from the first air hole 10-1-10-6 collides with the filament 9 before the filament 9 is widened by the air released from the second air hole 11. The first air hole 10-1-10-6 may be linearly arranged in the vicinity of the spinning nozzle 8 in such a manner as to open the filament to some extent. The width of the nonwoven fabric 13 produced by the melt spinner with a single spinneret is about 100-300 mm. Nonwovens having a width of 300 mm or more may be produced by a melt spinner having a plurality of spinnerets arranged transversely. Moreover, multiple spinnerets can be produced at high speed with a dense spinner arranged in the nonwoven longitudinal direction.

The air exiting from the first air holes 10-1-10-6 and the air exiting from the second air holes 11 are at a temperature higher than the melting temperature of the polymer material used to form the filament 9. Heated.

One of the air supplied from the first air holes 10-1-10-6 and the air supplied from the second air holes 11 may not be heated depending on the type of polymer material used. Using hot air, virtually no molecular orientation occurs in the filaments 9 during formation.

In fact, the spinneret described above may be used to form a nonwoven fabric consisting of undrawn filaments laid or arranged in the longitudinal direction of the nonwoven fabric. In this case, the spinneret is 90 ° from the position shown in FIG. 3 about the central axis of the spinning nozzle 8 to the position where the second air holes 11 extend perpendicular to the direction of movement of the nonwoven during production. Is rotated. The nonwoven fabric thus formed is particularly suitable for the longitudinal stretching process.

Suitable materials for the filaments of this nonwoven fabric include polyolefins, such as high density polyethylene (HDPE) or polypropylene (PP), polyesters, polyamides, polyvinylchloride, polyacrylonitrile, polyvinyl alcohol, polyurethanes, and stretchable and stretchable Other polymers that increase in strength when applied.

According to an important feature of the present invention, the specimen used to form the nonwoven fabric consists essentially of undrawn filaments. The non-drawn filaments have the following characteristics.

(a) a small yield strength that can be increased by less force;

(b) large elongation (at least several times its original length) at an appropriate drawing temperature;

(c) high strength at room temperature after stretching at an appropriate stretching temperature.

It has been found experimentally that nonwoven fabrics formed of unstretched filaments can be stretched by a tension less than or about equal to the bonding strength between the individual filaments. In this case, the respective filaments are stretched to the extent that they are rearranged to lie in a direction substantially parallel to the stretching direction. According to this stretching of the respective filaments, the ratio of the longitudinal (lengthwise) strength to the transverse (width direction) strength varies from about 7: 3 to about 5: 1 to 10: 1.

In strict sense, the unstretched filaments will not be completely free of molecular orientation. Rather, non-stretched filaments include filaments that can stretch to several times their original length (preferably two or more times). Such highly extensible filaments can be produced by the melt spinning described above with reference to FIGS.

In contrast to the nonwovens formed by the present invention, conventional random nonwovens are simple planar assemblies of filaments joined by mechanical bonding or by adhesion with an adhesive. Since the bond strength between the filaments is less than the strength between each filament, simply stretching such a nonwoven fabric automatically breaks the bond between the filaments before actual stretching or rearrangement of the filaments occurs. Moreover, conventional stretching processes do not take into account the thickness of the nonwovens, the degree of bonding between the filaments, and the various irregularities present in the adhesion of the nonwoven filaments. Non-woven fabrics having such irregularities are susceptible to rupture when stress is concentrated in weak areas or portions of the nonwoven fabric upon stretching. Therefore, a nonwoven fabric cannot be stretched large by a normal extending process.

Moreover, conventional nonwovens include short staple fibers or filaments. In random nonwovens made by a drying process or a wetting process, short staple fibers are firmly bonded by mechanical bonding or adhesion with an adhesive. Due to the tight coupling of short staple fibers, the stretching of the nonwoven is practically impossible. Although the nonwoven fabric is stretched, the stretching force is unevenly distributed throughout each short staple fiber.

On the other hand, nonwovens composed of filaments are difficult to stretch when the filaments used contain bubbles or large amounts of foreign matter.

Conventional filaments are pulled to gain strength before being treated with nonwovens, for example when spun. Therefore, the strength of the fibers is greater than the bond strength between the respective filaments, so that stretching the nonwoven breaks this bond and the individual filaments are not stretched or rearranged.

The nonwoven formed from the non-stretched filaments 9 lying substantially in the longitudinal or longitudinal direction of the nonwoven is stretched in the longitudinal direction by the device shown in FIG. 6 or the device shown in FIG.

In the apparatus shown in FIG. 6, the nonwoven fabric 14 is conveyed through a cooperating nip rolls 15a, 15b and then travels around the hot cylinder 16, in which the nonwoven fabric 14 is preheated. . The preheated nonwoven fabric 14 then moves continuously around a pair of slightly spaced stretch rolls 17a and 17b, with the stretch roll 17b rotating at a higher speed than the rotational speed of the stretch roll 17a. As a result, the nonwoven fabric is stretched in the longitudinal direction. Due to the longitudinal stretching of the nonwoven 14, each of the filaments is substantially stretched, resulting in molecular orientation within the nonwoven.

The longitudinally stretched nonwoven fabric 14 is thermally solidified while being guided around the heat treatment roll 18. The thermally solidified nonwoven fabric 14 is cooled and solidified by the cooling roll 19 and then exits the nip roll 20. The stretched nonwoven fabric 14 thus formed constitutes a continuous warp web 21 which is a longitudinally stretched nonwoven fabric, which is produced when the laminated stretched nonwoven fabric is subsequently produced as described above with reference to FIGS. 1 and 2. Inclined webs 1 and continuous webs 2 are used. The stretching interval between the stretching rolls 17a and 17b is at least limited to obtain a uniformly stretched nonwoven fabric. As a result, the diameters of the stretching rolls 17a and 17b are small and closely arranged with each other. The stretching interval is preferably no more than one tenth of the original width of the web.

In the apparatus shown in FIG. 7, the nonwoven fabric 14 formed of substantially non-stretched filaments placed in the longitudinal direction is provided with a pair of nip rolls 22a and 22b cooperating, a turning roll 23 and a pair of cooperating presses. The rolls 24a and 24b and the nip roll 25 are supplied to move continuously around. Pressurized rolls 24a and 24b are heated to an appropriate draw temperature, and the roll spacing defined therebetween is less than the original thickness of nonwoven fabric 14. Since the pressure roll 24b rotates faster than the pressure roll 24a, the nonwoven fabric 14 is stretched in the longitudinal direction while being pressed between the pressure rolls 24a and 24b. Due to this longitudinal stretching of the nonwoven 14, each filament is substantially drawn in a manner that causes molecular orientation in the nonwoven. The longitudinally stretched nonwoven fabric 14 is thermally solidified as it is guided around the hot press roll 24b. The thermally solidified nonwoven fabric 14 then exits the nip roll 25. The nonwoven 14 thus exiting the apparatus constitutes a continuous warp web 26 which is a longitudinally stretched nonwoven, which is subsequently fabricated of a laminated stretched nonwoven as described above with reference to FIGS. 1 and 2. Used as warp web 1 and continuous web 2. This stretching (rolling) process is particularly advantageous because the nonwoven fabric can be greatly stretched even when the thickness of the nonwoven fabric or the degree of bonding of the respective filaments is irregular. Another advantage is that the surface of the elongated warp web is polished like a pearl.

In fact, the nonwoven formed from the non-stretched filaments 9 lying in the transverse direction of the nonwoven is stretched in the transverse direction by the device shown in FIG. 8 or the device shown in FIG.

The apparatus shown in FIG. 8 consists of a pair of axially spaced pulleys 29a and 29b and a pair of endless belts 30a and 30b, which pulleys rotate at a uniform peripheral speed and the nonwoven 27 Disposed symmetrically with respect to this direction of movement to form two gaping arch paths on or along the outer periphery of the pulley, the belts each of the edges around the pulleys 29a and 29b forming two gaping arch paths; Tightly wound around the bottom of the. As the nonwoven fabric 27 moves around the pulleys 29a and 29b, the bottom portions of the pulleys 29a and 29b enter the heating chamber 32 which heats the nonwoven fabric 27. In operation both sides of the nonwoven fabric 27, which are conveyed longitudinally through the reversing rolls 28 to the pulleys 29a, 29b, are located between the pulleys 29a, 29b and the corresponding endless belts 30a, 30b. The nonwoven is then stretched in the transverse direction as the gripped edge moves along two gaping arch paths. Due to this stretching of the nonwoven 27, each of the non-stretched filaments are substantially stretched in the transverse direction in a manner that causes molecular orientation in the nonwoven. During stretching, the nonwoven 27 is heated by hot water, hot air or an infrared heater in the heating chamber 32. In the case of using hot air, it is desirable to force hot air into the nonwoven fabric 27 to increase the thermal efficiency. The laterally stretched nonwoven fabric exits the redirection roll 31 and, as described above with reference to FIG. 2, is a laterally stretched nonwoven fabric that is later used as the weft web 3 when producing the laminated stretched nonwoven fabric. The web 33 is constituted.

The apparatus shown in FIG. 9 comprises a pair of cooperating groove rolls 34a and 34b, in each of the rolls 34a or 34b a nonwoven is pressed between the rolls 34a and 34b and stretched in the transverse direction. There are a number of parallel spaced peripheral teeth 35 that mesh with the teeth 35 of the opposite groove roll 34b or 34a. The transversely stretched nonwoven is rolled up and then passed through at least a pair of similar groove rolls (not shown). Due to this multi-step transverse stretching, the resulting nonwoven fabric is greatly stretched and the structure is uniform. Using grooved rolls 34a, 34b, actual stretching occurs in each narrow area, placed side by side in the transverse direction, which extends between adjacent teeth 35 on each roll 34a, 34b.

Due to this subdivided stretching, irregularities in the thickness of the nonwoven fabric or irregularities in the adhesion or bonding degree of each filament may be reduced or eliminated. Although not shown, there are no grooves at both end portions of each groove roll 34a, 34b so that the edge of the nonwoven can be firmly gripped during stretching. Alternatively, the edges of the nonwoven 36 may be gripped by these between the groove rolls 34a and 34b and a pair of endless belts wound around both ends of one of the groove rolls 34a and 34b. Can be.

Claims (4)

(a) a first web of stretched nonwoven fabric formed by combining a plurality of substantially drawn filaments; (b) a cross-overlapping nonwoven consisting of a second web of stretched annex fabric formed by combining a plurality of stretched filaments, wherein the stretched filaments are unstretched filaments before being stretched, and the first web is a respective nonstretched The filaments are stretched in the longitudinal direction such that the filaments are substantially stretched to cause molecular orientation in the first web, and the second web is stretched in the longitudinal direction such that each of the non-stretched filaments is substantially stretched to induce molecular orientation in the second web and And the second web is laminated on the first web in such a manner that an extending direction of each of the first web and the second web is orthogonal to each other. (a) a first web of stretched nonwoven fabric formed by combining a plurality of substantially drawn filaments; (b) a cross-overlapping nonwoven, consisting of a second web of stretched nonwoven fabric formed by combining a plurality of stretched filaments, wherein the stretched filaments are unstretched filaments before being stretched, and the first web is a respective nonstretched The filaments are stretched in the longitudinal direction such that the filaments are stretched in length to cause molecular orientation in the first web, and the second web is stretched in the transverse direction such that each of the non-stretched filaments is stretched in nature in order to induce molecular orientation in the second web and And a cross-overlapping nonwoven fabric laminated on the second web and the first web in such a manner that stretching directions of the first web and the second web are perpendicular to each other. (a) forming a first web of random nonwoven formed by combining substantially non-stretched filaments; (b) stretching the first web in a longitudinal direction such that each non-stretched filament is substantially stretched to cause molecular orientation in the first web; (c) forming a second web of random nonwoven fabric formed by combining substantially non-stretched filaments; (d) stretching the second web in a longitudinal direction such that each unstretched filament is substantially drawn to cause molecular orientation in the second web; (e) continuously cutting the second web in a transverse direction such that the length of each of the second web pieces is substantially equal to the width of the first web; (f) the second web pieces are arranged in parallel with each other in a direction perpendicular to each other in the drawing direction of the first web and in the drawing direction of the second web piece. Method for producing a cross-overlapping stretched nonwoven fabric consisting of the step of laminating to. (a) forming a first web of random nonwoven formed by combining substantially non-stretched filaments; (b) stretching the first web in a longitudinal direction such that each non-stretched filament is substantially drawn to cause molecular orientation in the first web; (c) forming a second web of random nonwoven that substantially combines non-stretched filaments; (d) stretching the second web laterally so that each non-stretched filament is substantially drawn to cause molecular orientation in the second web; (e) stacking the first web and the second web in such a manner that the respective stretching directions of the first web and the second web are perpendicular to each other.

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