US3798100A

US3798100A - Apparatus for making spunbonded fabrics

Info

Publication number: US3798100A
Application number: US00247874A
Authority: US
Inventors: C Marchadier; J Togny
Original assignee: Rhone Poulenc Textile SA
Current assignee: Rhone Poulenc Textile SA
Priority date: 1971-04-26
Filing date: 1972-04-26
Publication date: 1974-03-19
Anticipated expiration: 1991-03-19
Also published as: FR2134206A1; CH553870A; BR7202407D0; DE2220575A1; LU65243A1; DE2220575C3; NL167741C; IT956239B; NL7203512A; ES402120A1; GB1345307A; DE2220575B2; SE387974B; BE782631A; NO132548C; DK132187B; NO132548B; AR196194A1; NL167741B; SU396875A3

Abstract

A PROCESS FOR PRODUCING SPUNBONDED NONWOVENFABRICS IS DISCLOSED, WHEREIN CONTINUOUS FILAMENTS OF ORGANIC POLYMERS ARE EXTRUDED, STRETCHED TO ORIENT SAME, AND THEN ARRANGED IN FABRIC FORM ON A MOVING CONVEYOR. THE FILAMENTS ARE ARRANGED OR DISTRIBUTED ON THE MOVING CONVEYOR BY IMPACT FROM A DEFLECTOR SURFACE, WITH A FLUID JET OPERATING UPON THE POINT OF IMPACT FORM A LOCATION IN FRONT OF THE POINT OF IMPACT IN RELATION TO THE DIRECTION OF THE DEFLECTED FILAMENTS, AND IN THE SAME PLANE AS THE AXIS OF THE FILAMENTS BEFORE AND AFTER IMPACT WITH THE DEFLECTOR SURFACE. THE SUPNBONDED NONWOVEN FABRIC PRODUCED BY THE DISCLOSED PROCESS ARE MORE HOMEGENEOUS THAN PRIOR SPUNBONDED NON-WOVEN FABRICS, AND ARE SUITABLE FOR KNOWN USES OF SUCH BABRICS, SUCH AS APPAREL BACKING PADDING AND THE LIKE.

Description

March 19, 1974 (;,MARCHAD1ER ETAL 3,798,100

AFPAHAIUS FOR MAKTNG SPUNBONDED FABRICS Filed April 26. 1972 United States Patent Int. or. 150411 3/00 U.S. Cl. 156-167 14 Claims ABSTRACT OF THE DISCLOSURE A process for producing spunbonded nonwoven fabrics is disclosed, wherein continuous filaments of organic polymers are extruded, stretched to orient same, and then arranged in fabric form on a moving conveyor. The filaments are arranged or distributed on the moving conveyorby impact from a deflector surface, with a fluid jet operating upon the point of impact from a location in front of the point of impact in relation to the direction of the deflected filaments, and in the same plane as the axis of the filaments before and after impact with the deflector surface.

The spunbonded nonwoven fabrics produced by the disclosed process are more homogeneous than prior spunbonded non-woven fabrics, and are suitable for known uses of such fabrics, such as apparel backing, padding and the like.

BACKGROUND OF THE INVENTION Spun-bonded non-woven textile fabrics are non-Woven textile fabrics substantially made of continuous filaments generally randomly disposed throughout the fabric.

The manufacture of spun-bonded non-woven textile fabrics generally consists of extruding through a draw plate a melted, or even dissolved, fiber-forming organic polymer. Depending upon the nature of the particular polymer involved, the extruded filaments are generally next oriented by stretching the extruded fiber bundle, generally by pneumatically stretching the filaments with one or several compressed air jets. Then, the filament bundle is deposited in a pre-determined manner on a moving conveyor, with the speed and the method of feeding the conveyor being regulated to control the desired thickness and width of the non-woven fabric, and also to increase the regularity or homogeneous nature, thereof. After being deposited on the moving conveyor, the spun-bonded fabric is often Subjected to a calendaring step, generally a relatively light calendaring step, preferably with the application of heat, to increase the cohesiveness of the final product. Generally this calendaring step causes some of the basic filaments to be bound to one another, markedly increasing the unity of the nonwoven fabric product.

As mentioned above, after the textile filaments have been extruded and stretched, the filaments are deposited on a moving receiving conveyor. The distribution of the filaments on the conveyor is normally accomplished with the use of deflector surfaces. The bundle of filaments is directed upon and impinges the deflector surface at a certain angle and then, after impingement, moves in a tangential direction along and off of the deflector surface. The deflector surfaces are in the form of flat or curved surfaces, preferably curved surfaces of revolution, which can be either concave or convex in relation to the direction of travel of the filaments.

It is known to utilize fixed, flat deflectors to produce relatively regular textile fabrics, and this involves a relatively simple design. However, the width of the distributed fibers, as well as their strength, is often less than desired.

The art prefers to use deflectors which produce a greater filament spread, as such use permits a decrease in the number of filament extrusion or spinning positions for a given width of final fabric produced. To achieve a sufficient filament spread, the art has used deflectors with complex surfaces, or movable deflectors, either flat or curved, which lead to greater filament spreads. However, these moveable deflectors are mechanically relatively complicated, expensive, difficult to precisely regulate, and relatively untrustworthy.

U.S. Pat. 2,736,676 discloses a process for producing sheets or mats made of strands, yarns or slivers of various materials, especially glass strands. The glass strands are extruded, stretched, and then impinged on a deflector surface. The patent discloses that the deflector surface may be either flat or curved, and may be fixed or moveable. The angle of impingement is disclosed as being between 0 and The patent discloses, with relation to FIG. 7 thereof, the use of two air jets, mounted on opposite sides of the point of impact, to laterally sweep the strand from the deflector surface, by alternate operation. The patent also discloses, with relation to FIGS. 8 and 9 thereof, the use of an air jet operating behind the point of impact to aid in throwing the deflected strand :1 further distance from the point of impact to a receiving conveyor. The process of this patent, however, still suffers the defects of prior processes mentioned above, namely inadequate width and poor homogeneity of the resulting product.

SUMMARY OF THE INVENTION The process of the present invention involves the use of a deflector surface upon which a polymeric filament is impinged, to produce a non-woven textile fabric hav-- ing greater width and uniformity than produced by the prior art processes. The polymer is extruded in filamentary form, and the filaments are oriented by stretching. Thereafter, the filaments are impinged on a deflector surface to distribute the filaments on a moving receiving conveyor. A fluid jet is associated with the deflector surface and is directed at the point of impact of the filaments on the deflector surface. The fluid jet is located in front of the point of impact, with relation to the direction of the deflected filaments, and the fluid jet is in the same plane as the axis of the impinging filaments and the average axis of the deflected filaments, and at an angle of 30- to the axis of the impinging filaments.

DESCRIPTION OF THE INVENTION Spun-bonded non-woven textile fabrics are manufactured by extruding filaments of a fiber-forming polymer, orienting the extruded filaments by stretching, and then distributing the filaments on a receiving conveyor by impinging the filaments on a smooth deflector surface. The improved process of the present invention involves directing a fluid jet at the point of impact of the filaments on the deflector surface from a location in front of the point of impact, in relation to the direction of the deflected filaments. The fluid jet is at an angle of 30-135 to the axis of the impinging filaments, and is in substantially the same plane as the axis of the impinging filaments, i.e., the filaments which are about to contact the deflector surface, and the average axis of the deflected filaments, i.e. the filaments which have contacted the deflector surface and have been deflected towards the receiving conveyor.

Various types of filaments may be used in the present process of manufacturing spun-bonded non-woven textile fabrics. The filaments may be made of fiber-forming inorganic polymers, such as glass, although preferably the filaments are made of a fiber-forming organic polymer. Any of the conventional textile fiber-forming organic polymers may be used, such as cellulose acetate, nylon or other polyamide, rayon, acrylic, modacrylic and the like.

However, the present process is particularly useful in the production of polyester spun-bonded non-woven fabrics. Preferably, the polyester is a polyalkylene terephthalate. When the term polyalkylene terephthalate is used in the present specification, it is to be understood to apply to polymeric linear terephthalate esters formed by reacting a glycol of the series HO (CH OH wherein n is an integer of 2 to 10, inclusive, with terephthalic acid or a lower alkyl ester of terephthalic acid, wherein the alkyl group contains l-4 carbon atoms, such as, for example, dimethyl terephthalate. The preparation of polyalkylene terephthalates is disclosed in U.S. Pat. No. 2,465,319 to Whinfield and Dickson, the disclosure of which is hereby incorporated by reference. The most widely used and commercially attractive polyalkylene terephthalate material is polyethylene terephthalate, which is the most preferred polymer in the practice of the process of the present invention. Polyethylene terephthalate is generally produced by an ester interchange between ethylene glycol and dimethyl terephthalate to form bis-2- hydroxy ethyl terephthalate monomer, which is polymerized under reduced pressure and elevated temperature to polyethylene terephthalate. The fiber-forming polymers are extruded into continuous textile filaments, generally of about 4 to 70 dtex.

The filaments may be extruded at extrusion rates which are conventional in the textile field. However, it is preferred that the impinging fibers be travelling at a speed of about 50 to 130 meters per second at the time of impact with the deflector surface, and the extrusion rate may be accordingly adjusted.

After extrusion, the filaments are generally stretched by an amount sufiicient to orient the polymer molecules in the filament. Generally, the stretching will be within the range of about 200 to about 400%, based on the un stretched length of the filaments. Preferably, the filaments are stretched by pneumatic means, but other means may be utilized, such as those disclosed in the aforesaid U.S. Pat. 2,736,676, the disclosure of which is hereby incorporated by reference.

After being stretched, the filaments are directed at the deflector surface, and impinged on the surface, generally at the aforesaid speed of about 50 to 130 meters per second. While the angle of impingement may be from slightly more than up to slightly less than 90, e.g. 1 to 89", it is preferred that the angle of impingement be from to 80, more preferably to 60.

The deflector surface may be flat or curved, and if a curved surface is used, it is preferred that the curved surface be a surface of revolution. The curved surface may be either concave or convex, and may be either stationary or rrnoveable, as known to the art. Any of the known deflectors, such as those disclosed in the aforesaid U.S. Pat. 2,736,676, may be used in the practice of this invention. It is important that the deflector present a smooth surface in order to prevent any restraint of the filaments and to prevent any filament impingement that might disturb the regularity of the deflected filaments. In normal operation, the nature of the deflector material has no significant influence upon the formation of the spunbonded non-woven fabric. However, it is clear that the material of which the deflector surface is made must have suflicient strength and resistance to abrasion so that the impingement of the filaments and the fluid jet will not deteriorate the surface. Among suitable materials for the deflector surface may be mentioned soft steel, bronz, glass, ceramics, and the like.

The fluid jet which is directed at the point of impact of the filaments with the deflector surface is conveniently formed by passing the fluid, under pressure, through a nozzle. In the case of compressed air, the air is suitably under a pressure of between about 1 to about 4 bars. The nozzle preferably has a circular cross-section of a diameter of 0.5 to 5 millimeters, preferably 1-3 millimeters, although the nozzle cross-section can be of shapes other than circular. For instance, the nozzle may be in the form of a rectangular or eliptical slot, having its major axis in the vertical plane defined by the axis of the impinging filaments and the average axis of the deflected filaments. In any event, the nozzle cross-sectional area is preferably no larger or smaller than that of the circular nozzle mentioned above. It should be understood that the fluid pressure and nozzle areas mentioned above are not limiting, but are decidedly preferred, as it has been observed that lower pressures or greater cross-sectional areas produces an insuflicient deflected filament spread, whereas higher pressures or smaller cross-sectional areas generally adversely affect the homogeneous nature of the resultant non-woven fabric product.

Particularly good results are obtained when the fluid jet acts in a manner which does not destroy the symmetry of the impacting bundle of filaments. This is accomplished by having the fluid jet substantially in the vertical plane which contains the axis of the impacting filaments and the average axis of the deflected filaments. The deflected filaments will be on diverging paths, so that some of the deflected filaments will be in a different vertical plane than other of the deflected filaments. Therefore, an average axis must be considered. In addition, the deflected filaments may be subjected to a sweeping action, e.g. such as that caused by movement of the deflector surface, and this also must be considered when determining the average axis of the deflected filaments. The velocity of the fluid jet should not be so great as to destroy the filament bundle symmetry.

Preferably, but not necessarily, the fluid jet is a gas, which generally is chemically inert with respect to the filament. It is, however, possible to use a gas or other fluid which does react with the filaments, if such action is desired. Compressed air is conveniently used as the inert gas, as being efficient and economical, but other gases may also be used, such as nitrogen, carbon dioxide, helium and the like, and liquids, such as Water, while not preferred, can be used as well.

The distance from the end of the fluid jet nozzle to the point of impact of the filaments on the deflector surface will vary according to the type of fluid, fluid pressure, nozzle size, diameter and number of filaments, and desired width of the fabric product. Generally, the nozzle will be located a few centimeters from the point of impact, but this distance can be as great as a few decimeters. Generally, the distance will be no greater than 5 decimeters and no less than about 2 centimeters, but preferably the distance is between 2 and 5 centimeters.

Obviously, several units comprising a deflector surface and fluid jet nozzle associated therewith can be mounted side by side with each group of filaments treated on each unit forming a portion of the final fabric. This approach permits the ready production of extremely wide spunbonded non-woven fabrics. Using this approach, care must be taken to avoid the disturbance of one deflected group of filaments by another group at the time of depositing the filaments on the conveyor. It is preferred to displace the deflected group of filaments so that they contact the conveyor in a stepwise manner. This is readily done by displacing the deflectors so that the planes of the deflected filaments leaving the deflector surface are parallel, and the points of impact are aligned along a straight line which is parallel to the plane of the receiving conveyor. This insures that the distance travelled by each group of filaments between the point of impact and the conveyor surface is the same.

After the filaments are deposited on the receiving conveyor, in the general form of the spun-bonded nonwoven textile fabric, the deposited filaments are subjected to conventional treatments to improve the cohesiveness of the non-woven fabric product. Generally the use of a relatively light calendaring step is preferred, although other approaches, such as use of an adhesive, can also be utilized. For polyalkylene terephthalate filaments, a calendering step using a nip pressure of 20 to 50 kilograms per centimeter and a temperature of 140 to 250 C. is preferred.

The Weight of the spun-bonded non-woven fabric produced, for a given fabric width, can be controlled by varying the speed of the receiving conveyor and/or the extrusion rate of the filaments. In the case of polyethylene terephthalate, the fabric weight will generally be in the range of to 500 grams per square meter, preferably 80 to 120 grams per square meter.

The spun-bonded non-woven textile fabrics produced by the process of this invention are used in applications where the products of prior spun-bonded non-woven textile fabric processes are used, such as apparel backing, padding, or the like. However, the products of the present process are wider and more uniform than the products of such prior processes.

DESCRIPTION OF THE DRAWINGS The invention will be more readily understood with reference to the accompanying drawings wherein:

FIG. 1 represents a schematic side view of the process, and

FIG. 2 illustrates a front view of the same process.

In FIGS. 1 and 2 a bundle of filaments 1, produced on an extrusion device (not shown) is stretched in compressed air nozzle 2. Upon discharge from the compressed air nozzle 2, the filament bundle 1 impinges upon a smooth, flat, fixed deflector surface 3.

A compressed air jet 6 passing through nozzle 4 is di rected at the point of impact of the filament bundle 1 upon deflector surface 3. Under the influence of both the deflector surface 3 and the compressed air jet 6, the filament bundle 1 is spread regularly and travels in a tangential direction from the deflector surface to receiving conveyor 5, which moves at a speed lower than the filament speeds. The filaments are deposited on conveyor 5 in the form of spun-bonded non-woven fabric 7. The distance between the point of impact of the filament bundle 1 on the deflector surface 3 and the receiving conveyor 5 is regulated by displacement of the conveyor 5.

EXAMPLES OF THE INVENTION Example 1 Four parallel bundles of filaments, each bundle having 60 filaments of 4.4 dtex, of polyethylene terephthalate were extruded through perforated draw plates having dies or holes 0.5 mm. in diameter, with the extrusion rate being 2.86 grams of polymer per minute per die. The extruded filaments were then stretched 350% of their original length by compressed air jets.

After stretching, each filament bundle was impinged on a smooth, flat, soft steel deflector plate at an impingement angle of about Compressed air under a pressure of 3 bars was passed through a nozzle having an round port of 2 mm. in diameter. The air jet, which made an angle of 90 C. with the impinging filaments (that is with the filaments passing between the stretching device and the deflector surface) was directed at the point of impact of the filaments upon the deflector surface and was located in the same plane as the axis of the impinging filaments and the average axis of the deflected filaments. The end of the air jet nozzle was mm. from the point of impact. Each of the 4 deflectors and deflecting fluid jet nozzles were displaced from each other a distance of 28 centimeters, and arranged in a straight line.

The filaments deflected from the deflector surface were received on a horizontal conveyor which was 400 mm. from the point of impact. A very regular fabric having a width of 600 mm. and a weight of 200 g. per square meter was formed by passing the fabric received on the conveyor through a pair of smooth steel rolls maintained at 170 C. at a nip pressure of 36 kg./cm.

Repeating this example, but using no deflecting fluid jet (the compressed air source was simply turned ofl) resulted in the production of a more irregular spun-bonded fabric having a width of only 150 mm.

Repeating this example, but using the deflecting ap paratus disclosed in FIG. 7 of the aforesaid US. Pat. No. 2,736,676 (that is, the single air jet was transversely disposed in a perpendicular plane to the vertical plane of the axis of the impinging filaments and the average axis of the deflected filaments) resulted in the production of a more irregular spun-bonded fabric having a width of only 150 mm., which was transversely shifted by about 30 mm. on the receiving conveyor. Thus, the use of an air jet directed from the side of the filament bundle resulted in a displacement of the filaments on the receiving conveyor, but had no effect on the width of the resulting spunbonded fabric.

Example 2 Example 1 was repeated, except that the extruder die holes were 0.3 mm. in diameter, producing filaments of 2.2 dtex. The deflecting air jet nozzle had a port in the form of a rectangular slot 4 mm. long and 0.7 mm. wide, with the main axis being located in the vertical plane defined by the axis of" the impinging filaments and the average axis of the deflected filaments. A compressed air pressure of 2.8 bars was used in the nozzle.

A highly regular fabric was obtained having a width of 650 mm.

Example 3 Polyethylene terephthalate was extruded through perforated draw plates having die ports or holes 0.5 mm. in diameter, at an extrusion rate of 2.86 grams per minute per hole, to form a bundle of 60 filaments of 4.4 dtex. The filaments were stretched 350% of their original length in a compressed air stretching nozzle. After stretching, the bundle of filaments was deflected upon a receiving apron by means of a convex deflector surface. The convex deflector surface was formed of a portion of a revolution cone, the generators of which oriented from the base towards the summit formed an angle of 120 with the leading axis of the filament bundle.

A compressed air jet was applied to the point of impact at an angle of 35 with the impinging filament bundle. The air jet was formed by passing compressed air under a pressure of 3.5 bars through a nozzle having a circular port 3 mm. in diameter, with the end of the nozzle located about 30 mm. from the point of impact.

The distance from the point of impact of the filaments on the deflector surface to the receiving apron was about 4001 mm. and the receiving apron was inclined at a 45 ang e.

The material received on the apron was calendered at a nip pressure of 30 kg./cm. and a temperature of 170 C. The resulting spun-bonded non-woven textile fabric had a width of 350 mm. and a weight of 120 grams per square meter.

Repeating this example but without using a compressed air jet resulted in the production of a more irregular fabric having a width ofonly mm.

Example 4 This example involves the use of a concave deflector having a cyclically oscillating motion around a vertical axis parallel to the axis of the impinging filament bundle.

The deflector was oscillated 60 round trips per minute about its axis, with the total travel spanning 22. The deflector surface was in the form of a round half tile having a diameter of 100 mm. and a length of mm. The point of impact was at the mid-point of the tiles length. The major axis of the deflector made an angle of 120 with the axis of the impinging filament bundle.

A bundle of 70 polyethylene terephthalate filaments of 8.9 dtex were extruded through a perforated draw plate having holes 0.5 mm. in diameter at an extrusion rate of 5.2 grams of polymer per minute per hole. The extruded filaments were stretched 350% of their original length in a compressed air stretching nozzle, and then impinged upon the above described concave deflector. A compressed air jet was directed at the point of impact, at an angle of 45 with the direction of the impinging filament bundle, the air jet being located in the same plane as the axis of the impingement filament bundle and the average axis of the deflected filaments. The air jet was formed by passing compressed air under a pressure of 3 bars through a single nozzle having a circular port 2 mm. in diameter, with the end of the nozzle located about 25 mm. to the point of impact.

The bundle was deflected upon an apron inclined at an angle of 35 and located 800 mm. from the point of impact. After being calendered at a nip pressure of 30 kg./cm. and a temperature of 170 C., a fabric having a weight of 150 grams per square meter, and a width of 800 mm., was obtained, which was more homogeneous and wider than a spun-bonded non-woven fabric obtained in the identical process but without the use of the defleeting fluid jet (without the deflecting fluid jet, the fabric width was only 400 mm.).

Repeating this example, but using the deflector arrangement of FIGS. 8 and 9 of the aforesaid U.S. Pat. No. 2,736,676 (that is, using a single air jet located directly behind the point of impact, in relation to the direction of the deflected filaments) resulted in the production of a more irregular spun-bonded fabric having a width of only 400 mm. In this air jet arrangement, the air jet had no influence on the filament behavior other than accelerating the filaments leaving the deflector surface, to enable the deflector filaments to be thrown a greater distance from the point of impingement (Which is consistent with the teaching of the aforesaid U.S. patent).

What is claimed is:

1. In a process for manufacturing spun-bonded nonwoven textile fabrics, said process comprising extruding a plurality of filaments of a fiber-forming polymer, orient ing the extruded filaments by stretching, and distributing the filaments on a receiving surface by impinging the filaments upon a smooth deflector surface, the improvement comprising spreading the filaments without destroying the filament bundle symmetry directing a fluid jet to the point of impact of said filaments on said deflector surface, said fluid jet being at an angle of 30-135 to the axis of the filaments prior to said point of impact and located in front of the point of impact in relation to the direction of the deflected filaments and in substantially the same plane 8 as the axis of the impinging filaments and the average axis of the deflected filaments.

2. The process according to claim 1, wherein said fluid jet is a gas jet.

3. The process according to claim 2, wherein said gas jet is discharged through a nozzle having a diameter or minimum width of 0.5 mm. and a maximum diameter or width of 5 mm., and wherein said gas is under a pressure, prior to passing through said nozzle, of about 1-4 bars.

4. Process according to claim 3, wherein said gas is compressed air.

5. The process according to claim 1, including the additional step of calendaring the spun-bonded nonwoven fabric to improve the cohesiveness of said fabric.

6. The process according to claim 1 wherein said deflector surface is a fiat surface.

7. The process according to claim 1 wherein said deflector surface is a curved surface.

8. The process according to claim 7 wherein said curved surface is a surface of revolution.

9. The process according to claim *1 wherein the major axis of said deflector surface is at an angle of 10 to to the axis of said filaments prior to contact with said deflector surface.

10. The process according to claim 1 wherein said filaments are pneumatically stretched.

11. The process according to claim 10, wherein said filaments are stretched 200 to 400% of their original length.

12. The process according to claim 1, wherein said filaments are polyester filaments.

13. The process according to claim 12 wherein said polyester filaments are polyalkylene terephthalate filaments.

14. The process according to claim 1, wherein said filaments are travelling at a speed of about 50 to about meters per second at the time of impinging said defector surface.

References Cited UNITED STATES PATENTS 3,692,618 9/1972 Dorschner et al l56l8l 2,736,676 2/19'5'6 Frickert, Jr. 156-16-7 3,314,840 4/1967 Lloyd et al. 156-167 2,875,503 3/1959 Frickert, Jr. 156-467 DANIEL J. FRITSCH, Primary Examiner U.S. Cl. X.R.