FI66923C - FRAMEWORK FOR CONTAINING FRAMEWORK WITHOUT FRAMEWORK - Google Patents

Description

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Patent · och regleter ityreleen AnaMan iithfd och «LakrtfkM puMnrarf j i. uo. oh (32) (33) (31) Requested etheoftem B «| M prtorltt 31.08.73 USA 393688 (71) Pali Corporation, Glen Cove, New York, USA (72) David Boris Pall, Roslyn Estates , New York, USA (74) Oy Kolster Ab (54) Method for continuous production of nonwoven webs -Förfarande för kontinuerlig framställning av ovävda banor (62) Divided by application 2552/74 (patent 59430) -Avdelad frln trap 2552/74 (patent 59430)

The present invention relates to a method of forming nonwoven flexible webs of thermoplastic fibrous material into a seamless, continuously length helically wound structure, in which the molten thermoplastic material is spun from a plurality of spinning ends into a plurality of strands. and wherein the fibers are collected and wound directly on the collecting surface on the outer surface of the rotating mandrel to form a cylindrical layer of heterogeneously spun spun fibers randomly oriented therein, and in which method a nonwoven fibrous material when spinning so that the cylinder is continuously formed at one end of the mandrel and the cylinder is pulled n continuously at one end, with the mandrel rotating.

Examples of methods known in the art include U.S. Patent Nos. 3,543,332 and 3,615,998. In the solution of U.S. Patent No. 3,543,332, the fibrous material is pressed through only one opening. Thus, multiple openings are not used in the solution. Also, the fiber is not thinned and broken, but the fiber is continuously collected on the drum in the form of a continuous fiber. In the solution of U.S. Patent No. 3,615,998, a tube of fibrous material is formed by passing a liquid fibrous material through a nozzle. The resulting threads are not broken into discontinuous parts. The fibers are collected on the inner surface of the rotating tube and on this surface the resulting tube is pulled out and flattened into a two-layer web. Again, only one nozzle is used in this solution. An example of the use of several nozzles is FI patent publication 59430, from which the present invention has been separated by division. However, in the solution of FI patent publication 59430, the nozzles are at a different distance from the collecting surface.

The method according to the invention is mainly characterized in that the spinning openings are placed at an equal distance from the collecting surface on the outer surface of the rotating mandrel, and that the flexible cylinder of nonwoven fibrous material is flattened

The advantage of the invention is that the density of the resulting web is obtained by placing all the nozzle openings of the spinning mold at the same distance from the accumulation surface on the outer surface of the rotating mandrel. If the plane formed by the spinning openings containing the nozzle openings is parallel to the outer circumference of the mandrel and the cylinder placed on it, all the nozzle openings are located at the same distance from the collecting surface. It follows that all the fibers travel the same distance before they reach the heart.

By proceeding according to the method of the invention, a web of varying density and pore size can be obtained, if desired, by placing fibers of varying diameters, but less than 6, with different diameters in different proportions or located in different zones or layers of the web. Thus, if necessary, nozzle openings can be used, 3 66923 grouped according to size, or all groups have different sized nozzle openings and different sizes in different groups in different proportions. In addition, if necessary, spinning head groups can be used in which the speed of the dilution air varies from one part to another, resulting in a higher or lower density and pore size depending on the position relative to the inner surface of the material cylinder. In either case, fibers of different diameters are placed in different zones, causing changes in density.

This process allows unlimited flexibility in the dimensions and number of nozzle openings as well as in the clearances of these nozzle openings at this spinning head. The large continuous spinning heads required to position a wide web in place on a moving belt are difficult to construct and certain size limitations cannot be practically exceeded, but there is no limit to the number and location of these spinning heads in the method of this invention. Since each part of the web, which rotates simultaneously and moves axially, is at the same distance and under a similar effect from each of the mandrel heads used, these spinnerets can be arranged around this mandrel in any position and orientation so as to provide any desired number of fibers per unit spacing. Multiple narrow spinning heads, which are easier and cheaper to manufacture, can be used in a certain number so as to provide this web at any desired size and at the desired production rate.

It is not necessary to use an adhesive or glue to hold the fibers in place in the resulting nonwoven fibrous web. These fibers become thoroughly adhered to each other during placement due to adhesion. If the fibers are soft and sticky the moment they hit the heart, they can stick together at their intersections during winding. However, this process can be adjusted so that the fibers, when melted as they emerge from the nozzle openings of this spinning mold, harden, solidify and are no longer sticky by the time they reach the heart and are wrapped in a pile. In such fibers, their dimensions are fixed at the moment when the cartridge is formed, and thus a better adjustment of the pore size can be realized, since these fibers have little or no tendency to warp randomly during stacking.

Since the cylinder made according to the method is flattened in a manner known per se after drawing from the mandrel in a manner known per se to form a double-layered web joined at the edges which does not open at the edges, pieces of the web-shaped sheet thus obtained can be cut into desired pieces. Such sheets can be advantageously used, for example, as filter parts. Although such sheet materials are particularly useful as filter components, they are generally useful in the same way as nonwoven fibrous webs in general, i.e. as insulation, linings or interlinings in building partitions, packaging materials, clothing, cooling and heating systems, carpeting, flooring and other flooring. for cars, trucks and buses, farm equipment and tools to name just a few.

Preferred embodiments of the method and products of the invention are illustrated by the examples described in the drawings, with Figure 1 representing an embodiment of the method of the present invention in which a relatively flexible fibrous sheet material is flattened after being pulled from a mandrel; Figure 2 shows a longitudinal section of a mouthpiece Fig. 3 is a perspective view of the spinning head of Fig. 2, Fig. 4 shows a second embodiment of the invention in which a cylinder is placed on a tubular nozzle. , which is preformed by extrusion or in some other way and which net acts as a permanent part of the resulting flattened cylinder element, Fig. 5 shows a longitudinal section of the flattened spir made of a helically twisted filter part by a method according to Fig. 4 as a filter cartridge, Fig. 6 shows a cross-sectional view taken along line 6-6 of the filter cartridge shown in Fig. 5.

The method of the present invention is applicable to any thermoplastic resinous material that can be spun through the nozzle openings of a spinning mold or spinning device to form fibers that are capable of supporting themselves. Exemplary thermoplastic materials include polyamides, polyacrylonitrile, linear polyesters such as esters of ethylene glycol and terephthalate acid, polyvinylidene chloride, polyyvinyl chloride, polyvinyl chloride, polyvinyl acetate, copolymers of vinyl chloride and vinyl acetate, polyvinyl chloride, vinyl acetate, , polytrifluorochloroethylene, polymethylpentene and polyisobutylene. Also included in this class are thermoplastic cellulose derivatives such as, for example, cellulose acetate, cellulose propionate, cellulose acetate propinate, cellulose acetate butyrate and cellulose butyrate. Non-resinous materials such as glass can also be treated in a similar manner.

The fibers can be spun to any desired diameter specified in the requirements. Single yarns are generally considered the most preferred, but multifilament yarns can also be spun. Both are only commonly referred to herein as fibers. These strands may be of any desired cross-sectional shape, generally round but also elliptical, square, hourglass-shaped, triangular, pentagonal, V- or U-shaped, T- or I-shaped or other cross-sectional, and may be closed, tubular, cellular or foamed.

Any filament less than 6 μm in diameter can be used in this method. Fine fibers generally provide a nonwoven web with a finer pore size and coarser filaments generally provide a nonwoven web with a larger pore size.

Threads of different sizes can be used in different areas of this cylinder. For example, fine fibers from one set of nozzle openings may be positioned first in the inner portion of this cylinder and coarse fibers from another set of nozzle openings may be positioned in the outer portion of this cylinder. This results in a cylinder with a progressively variable and tapering pore size that decreases from coarse to small in size from outside to inside in this cylinder in the same manner as described in U.S. Patent 3,158,532 to David B. Pali and Cyril A. Keed-well, issued 24 November 1964. Mixtures of fine and coarse fibers can be placed in place for the entire depth of this filter cylinder using a spinneret mixed with nozzles of different diameters using varying diameters ranging from fine to coarse just to give an example.

Any conventional spinning head or spinning device can be used. Such spinning heads are available and are known per se in the field of fiber spinning and do not form any part of the present invention.

In the most preferred spinning head, apertures are arranged circumferentially around the individual nozzle orifices or around a series of these, arranged to discharge gas at a high but controlled rate in the direction of the central axis of this orifice.

This gas blowing elongates these fibers and tends to break them so that they break into separate pieces, which can be adjusted according to the speed and volume of this gas blowing. If a plurality of spinning orifices are used, the blow can be discharged from fountains arranged around the circumference of the individual jets or nozzles. In the case of a spinning head with a plurality of nozzle openings in a given plate, the blowing can be let out of the edge area of this spinning head. A typical arrangement is shown in Figures 2 and 3, where a spinneret nozzle is illustrated.

This gas blowing can be heated so as to slow down the cooling of these fibers. Gaseous blowing can also be used as cold blowing, so as to accelerate the cooling of these fibers and thus their solidification rate. Thus, by using gaseous blowing, the time interval during which the fibers harden and solidify can be adjusted. If the fibers are kept hot for a longer time, thinning increases, if the fibers are cooled faster, this thinning is reduced. Thus, some adjustment to the length of these fibers can also be achieved in this way.

The polymeric material from which these fibers are spun is kept in a molten state during this spinning. The temperature of this melt is adjusted to melt the material having the desired viscosity at the time the material comes out of the orifice.

This also provides some control over the degree of thinning and the lengths of these fibers, as the more viscous material tends to be more cohesive and thinner by less gaseous blowing and because it is generally at a lower temperature, it also cools faster and therefore solidifies in less time.

The distance between the nozzle openings in this spinning mold from the rotating core, i.e. the mandrel, is adjustable so that by the time the fibers reach this core, they have cooled sufficiently so that they already retain their shape. They may still be soft and, as a result, sticky, so that 7 66923 they tend to adhere to each other at their intersections.

They may also be completely solidified so that they do not stick to each other, which situation preserves their shape better. They are collected in a randomly oriented heterogeneously intertwined arrangement on this core portion because substantially no adjustment is made to the path of these fibers as they pass from the spinneret to the core portion along a particular path. By the time the fibers reach the heart, they are either broken into pieces or broken into discrete lengths, or they are still attached to a nozzle orifice from which they have been spun by a certain portion, which is molten. In all likelihood, this will result in very little thinning of the fibers due to the rotational movement of this core, and any thinning is usually accomplished solely by gaseous blowing and normal thinning by the weight of solidifying or solidifying fiber that develops into the molten portion of this fiber at the orifice. However, mechanical thinning of these fibers prior to placement can be accomplished using a conventional thinning method, such as, for example, drawing the fibers while they are still plastic.

The fibrous material collected on the rotating core part, i.e. the mandrel, tends to be layered in structure, and the material collected during each successive rotation forms a single layer or part thereof. If the distance from the mold to the core or the cylindrical collecting surface is small, i.e. 7.5 to 10 cm, these fibers in the adjacent layers become firmly adhered to each other, so that it becomes difficult or impossible to separate or separate these layers from each other. If the distance from the spinning head to the collecting surface is relatively large, i.e. 30 to 45 cm, these layers can be separated from each other, but the adhesion is large enough for the product to be very useful for several filtration purposes. The thickness of each layer in this stackable web obtained depends on the speed of rotation of the core part, which is not critical for a very wide range from a practical point of view. As a general rule, it is desirable for the core portion to rotate at such a speed that each portion of the collected web cylinder contains two or more layers.

If the distance from the nozzle openings to the collecting surface is relatively large and the distance between the nozzle openings is relatively large, "rope entanglement" (strand entanglement or helical twisting so as to obtain a thick wire or string) may occur in different strands from adjacent nozzle openings. A certain amount of "rope formation" can be tolerated without substantially adversely affecting the properties of this cylinder. However, as "rope formation" increases, this cylinder begins to acquire the properties of a "honeycomb" cylinder, which may be detrimental.

In general, at a distance between 7.5 and 10 cm, no "rope formation" occurs, while at a distance greater than 30 cm, this "rope formation" becomes severe. At these spacings, i.e. between 10 and 30 cm, "rope formation" occurs and it becomes more and more severe. The distance can thus be adjusted as needed to avoid or control this amount of "rope formation".

For filtering liquids, uniformity of placement is important and the distance is thus most preferably between 7.5 and 12.5 cm. For gas filtration, it is most preferred to have a large void volume to reduce the pressure drop across this nonwoven web, and thus the distance is most preferably between 17.5 and 25 cm, so as to obtain a lower density location and a reasonable proportion of "rope braided" filaments.

Another way to control "rope formation" is to increase the spacing of the nozzle openings. In a conventional spinning head, the nozzle openings are quite close to each other and the arrangement of 20 to 50 nozzle openings for each 2.5 cm line length is of the standard type. Such a distance provides serious "rope formation" at distances greater than 30 cm.

On the other side of the addition to spacing, so that the nozzle piece 10, kostakutakin 2.5 cm per line length of up to one each of the nozzle opening of 2.5 cm per line length substantially closes off if not completely eliminate this "köydenmuodostusta". Although this increases the size and length of the spinning head or heads, this is perfectly acceptable in the process of this invention.

By positioning the spinning head or spinning head assembly so that all nozzle openings are equidistant from the circumferential surface of the rotating core portion, i.e. the mandrel, or the cylinder placed thereon, and by thinning these fibers prior to placement using gas blowing or other thinning means, a uniform felt or web density is achieved. As already mentioned above, this density can be easily adjusted by changing the distance between the nozzle openings and the collecting surface.

9 66923

In the case of continuous operation, the thickness is adjusted by the diameter of the mandrel diameter at the speed at which the fibers are cast, the density of the collected fiber structure, and the speed at which the cylinder is pulled into place from the placement zone.

The rotating core part, i.e. the mandrel on which the blanket is placed, can be rotated in a certain fixed position, whereby the finished cylinder is pulled out from the end of this core part and wrapped together as flattened, as shown in Fig. 1. To facilitate sliding of the tubular web from the core part, this core part can that is, the mandrel should be tapered so that its diameter decreases towards the end from which the web is pulled out.

When relatively thicker walled pipes are produced in the above-mentioned manner, e.g. when the wall thickness exceeds 0.6 cm or 1.3 cm, these fibers may soften as a result of being exposed to the impact of the extended hot gas flow. This is especially the case when the distance from the spinning head to the mandrel is small, e.g. when it is less than 10 to 17.5 cm. In order to avoid the resulting condensation and shrinkage, it is often advantageous to bring in a coolant, which can be achieved by various means, e.g. by cooling the core collecting from the inside, e.g. by making cold water flow through it or cooling the fibrous mass by blowing cold or room temperature air. from the opposite side through and towards it or by blowing cold air suitably through the perforated core portion.

After the double web is formed in the above-mentioned manner, it can be further treated in various ways. It can be impregnated with a resinous binder or impregnating agent so as to obtain a stiffer structure or a lower porosity therein. Additives can also be added to it. For example, if the web is to be used for water treatment purposes, it may be impregnated with a bactericidal agent or a fungicide or other water treatment agent which must be dissolved in the water introduced through it.

Additives can also be included by feeding them into the flow of fibers from the nozzle openings of the spinning head before they are placed. Such additives may include diatomic clay, glass or other organic or inorganic fibers, surfactants, filter aids such as silicone resins, polytetrafluoroethylene, hydrophobic silica and the like, and binder resins in liquid droplets or solid form.

10 66923

The device shown in Figures 1-3 includes a spinning head 30 having a series of nozzle openings 33 on the surface 31 of uniform size. (Compare Figures 2 and 3.) A molten thermoplastic polymeric material, such as polypropylene, is fed to this spinning head from a container fed through an inlet 5 which conveys molten thermoplastic polymeric material from a press or other feed source (not shown) under pressure which is sufficient to push the material out through the nozzle openings in this mold, thus forming a plurality of molten fibers 10.

These fibers pass over a short air gap, during which they thin out under the influence of air from the openings 3 and solidify and accumulate on a tapered rotating core 32, the other end of which is held by a shaft 34 of an electric motor 35 arranged to rotate the core at a relatively slow speed, approximately 1-1 , 5 m / s in this case. These fibers are randomly arranged and intertwined heterogeneously with each other as they wrap around the core, forming a generally helically wound mat of nonwoven fibrous material 36.

The device shown in Fig. 1 has a spinning head 30, the surface 31 of which has nozzle openings arranged parallel to the longitudinal axis of the core part, i.e. the mandrel 32, so that all of the nozzle openings 33 are equidistant from the surface of this core part. The result of this is that all the fibers travel the same distance before they end up on the collecting surface. Correspondingly, if the openings of the mold are equal, then the mat formed of fibers is of uniform density throughout. During forming, the tube 36 is continuously pulled to the right, flattening it using flattening rollers 37 and 38, and then wrapped to form a helical roll 39. The result is a two-layer sheet or web of nonwoven fibrous material having longitudinal edges non-braided because the sheet or web consists of a compressed tubular blank. In this way, a very cohesive filter sheet is obtained from a non-woven material in which the fibers are unable to migrate.

In the treatment system shown in Figure 4, the preformed core portion 71 also forms a core filter portion that can be pulled out in a cylindrical shape and flattened with a core such as a perforated clearance piece, as shown in Figure 4.

11 66923

The core 71 is compression molded into a mesh parallel to the diagonal open mesh of thermoplastic polymeric material. Since the net is continuously cast during manufacture, it may be in very long lengths. The net is tubular in shape and has a plurality of openings 73 through which fluid passes through an open slot 74 in the center therein. The net 71 is continuously fed forward by a mandrel 83, which in turn is supported at its distal end by the core portion 1a of this die casting mold 80. The net 71 continuously moves into place to receive the pore fibers 76 which are spun from the nozzle openings 77 of the spinning head 78.

As the compression-molding polymeric material, not only any of the thermoplastic crosslinking agents used to form the fibers can be used, but also materials such as, for example, polycarbonates, polyoxymethylene, polytetrafluoroethylene polyaldehydealdehydealdehyde, polychlorotrifluoroethylenealdehyde, phenol-formaldehyde, phenol-formaldehyde, The fibers 76 are spun on this core 71 in the same way as in Fig. 1 and thus the resulting combination of core and filter part 75 formed thereon is pulled forward and flattened by rollers 81 and 82 and the resulting two-layer sheet 84 with inner two-layer mesh 71 is then wrapped on a storage roll 85 .

Figures 5 and 6 show a helically wound filter portion made of a two-layer pile of two-layer sheet material 84 and 71 obtained using the system of Figure 4. This sheet material has two layers 40 and 41, the longitudinal edges of which are adhered to each other due to the tubular nature of this sheet.

A double tubular sheet 84 made in accordance with the invention may be helically wound into a cylindrical portion 42 provided with a longitudinal slot 43. One end 44 of tube 84 is secured to this slot and the tube is then twisted several turns around the core overlapping the second strip 45 into a net fluid for flow. The internal mesh 71 acts as an internal clearance for fluid flow. The outer end of the 46 tubular sheets is closed. The liquid passes in the edge direction along an overlapping outer strip 45, from there through the hose walls 40 and 41 into the inner space of this hose 84 along the net 71 to part 43 12 66923 and then into the open interior 47 from the core 42 closed at one end 48 so that all liquid is introduced 49 through the other end. The core has an O-ring seal 50 for sealing purposes in a filter assembly (not shown).

In an alternative construction, strips of flat tubular web with an inner tube made of flat tubular mesh may be closed at one end and the other attached to a tubing sheet by which a plurality of such tubes are connected to a single outlet forming a large area "parallel plate" filter.

The following example represents, in the opinion of the inventor, a preferred embodiment of the present invention.

Example Using the system of Figure 1 and a tapered core portion, i.e. a mandrel with a diameter of 10.00 cm at the larger end, a polypropylene polymer was spun at 327 ° C at a speed of 5 kg per hour for a rotating core portion. The temperature of the diluting air was 332 ° C. This cylinder was pulled out of the core section and flattened before being wrapped in a pile. The resulting cylinders, when flattened, were 14.5 cm wide and when split and opened, they were 29.2 cm wide, although the casting mold used was only 25 cm wide. These sheets were very strong and very flexible and apparently had perfect return ability after several piles of piles. Various experiments were performed on these sheets and the results are shown in Table I. These sheets have several uses as filter media and in addition are useful as thermal and electrical insulators, clothing, disposable clean room and hospital clothing, battery separators and the like.

Preferred types of spinning heads are described (1) in the report Manufacture of Superfine Organic Fibers, U.S. Pat. Department of Commerce, Office of Technical Services, from the Naval Research Laboratory, (2) in an article by Van A. Wenten,

Ind. & Eng. Chem., Volume 48, Number 8, pages 1342-1346, August 1956, and (3) in the report An Improved Device for the Formation of Superfine Thermoplastic Fibers by Lawrence, Lucas & Young, U.S. Pat. Naval Research Laboratory, February 11, 1959, and these three reports are referred to as 1 3 66923 I ^ ¾.

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Claims (3)

66923 A method of forming nonwoven flexible webs of thermoplastic fibrous material into a seamless, continuously length helically wound structure, wherein the molten thermoplastic material is spun from a plurality of spinnerets into a plurality of strands. the fibers are collected and wound directly on the collecting surface on the outer surface of the rotating mandrel to form a cylindrical layer of randomly oriented spunbonded fibers spunbonded therewith, and in which method a web at one end and the cylinder is continuously pulled at the other end, as the mandrel rotates, characterized in that the spinning openings are spaced equidistant from the accumulation surface on the outer surface of the rotating mandrel, and that a flexible cylinder of nonwoven fibrous material is flattened after drawing from the mandrel in a manner known per se. A method according to claim 1, characterized in that the fibers are soft and adherent at the moment when they hit the accumulation surface and that they adhere to their intersection point, adhering to each other during winding on the accumulation surface. A method according to claim 1, characterized in that the fibers solidify and are not sticky when they reach the accumulation surface and winding occurs.